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, doi: 10.14135/j.cnki.1006-3080.
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$v.latestStateEn , doi: 10.14135/j.cnki.1006-3080.20190806001 [Abstract](1533) [FullText HTML](460) [PDF 820KB](17) [Abstract](5151) [FullText HTML](666) [PDF 617KB](6) [Abstract](6453) [FullText HTML](1338) [PDF 1448KB](5) [Abstract](5816) [FullText HTML](1531) [PDF 840KB](2) [Abstract](7888) [FullText HTML](1819) [PDF 772KB](11) [Abstract](5977) [FullText HTML](1572) [PDF 1340KB](9) [Abstract](6724) [FullText HTML](2010) [PDF 852KB](3) [Abstract](8830) [FullText HTML](2070) [PDF 1289KB](4) [Abstract](6455) [FullText HTML](2084) [PDF 827KB](18) [Abstract](9195) [FullText HTML](3485) [PDF 1107KB](12) [Abstract](7250) [FullText HTML](2752) [PDF 892KB](5) [Abstract](7015) [FullText HTML](1970) [PDF 1041KB](6) [Abstract](9979) [FullText HTML](2651) [PDF 949KB](10) [Abstract](7979) [FullText HTML](2041) [PDF 1323KB](16)$v.latestStateEn , doi: 10.14135/j.cnki.1006-3080.20190428002
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Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes/issues, but are citable by Digital Object Identifier (DOI).

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Dispersion is an important indicator affecting the application properties of nano-silica. A new method for treating the precipitatednano-silica particles by high-temperature rapid flame treatment was proposed. The effect of the method on the surface structure and dispersion of silica nanoparticles was investigated. At the same time, the reinforcing effect on the silicone rubber was studied. The results showed that under the optimal treatment conditions, the mass fraction of adsorbed water of nanoparticles decreased by 28.3% compared with untreated samples, and the number of surface hydroxyl groups decreased by 27%. The treated nanoparticles were used for silicone rubber reinforcing filler. The tensile strength was increased by 41.6% compared to the untreated sample, and the tear strength was increased by 100%.
Abstract:
The associated fluorine impurities in phosphate ore seriously affect the quality of the phosphoric acid during the wet-process phosphoric acid production. Tributylphosphate (TBP) was used as an extractant, sulfonated kerosene (hereinafter referred to as kerosene), isoamylol, diisopropyl ether were used as the diluent, respectively. The extraction mechanism was investigated by quantum chemical calculation, flourier transform infrared spectroscopy (FT-IR), 19F nuclear magnetic resonance (19F NMR) and composition of extraction complexes. The binding energy of TBP-kerosene with HF was calculated by implicit solvent model, while TBP-isoamylol and TBP-diisopropyl ether with HF were calculated by explicit solvent model. The results show that the binding energy of above three extraction systems are −13.399, −19.199, and −20.556 kJ/mol, respectively. Analyses of the FT-IR spectra of the loaded organic phases indicate the TBP extraction of HF is occurred by the association of hydrogen bonding, while the extraction of HF using isoamylol and dissopropyl ether is realized through hydrogen bonding. The main form of fluoride in organic solvent was TBPHF according to the 19F NMR spectra. The compositions of the extraction complexes in the solvent of kerosene, isoamylol, diisopropyl ether were determined to be 0.9HF TBP, 1.4HF TBP and 1.6HF TBP, respectively. The effects of different fluorine forms in wet-process phosphoric acid on defluorination rate were studied. It can be concluded that CaF+ and \begin{document}${\rm{FeF}}_x^{3-x}$\end{document} (x=1~6) have a slight effect on the selectivity coefficient and defluorination rate. MgF+ can be effectively extracted from the organic solvent by TBP, and the selectivity coefficient is increased with increase in the concentration of Mg2+. The TBP extraction of \begin{document}${\rm{SiF}}_6^{2-}$\end{document} and \begin{document}${\rm{AlF}}_x^{3-x}$\end{document} were moderated, indicating that the defluorination of wet process phosphoric acid needs to be achieved by pretreatment or other methods when the content of active silica and aluminum oxide in phosphate rock is high.
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New drug design is a huge project, and the failure rate is very high. If based on existing active compounds, the design of “me-too” drugs can increase the success rate. The “me-too” drug should have the same or similar spatial structure, pharmacophore, etc. as the original active compound, so as to ensure that the combination of the “me-too” drug and the enzyme is the same as the original active compound. The lead compound can provide the same or similar spatial structure as the original active compound, and a novel skeleton, but the skeleton of the lead compound does not necessarily have good physicochemical properties. Designing “me-too” drugs based on lead compounds can significantly reduce the difficulty of new drug development and improve development efficiency and success rate. How to accurately grasp the spatial structure of the lead compound, designing a novel structure, a reasonable valence bond, and a skeleton with the same or similar spatial structure as the lead compound are the key issues in designing “me-too” drugs. The author designs and writes an automated new drug skeleton design software based on the extraction of structural long chains, fragment matching and splicing: ChemCloser. The software can provide researchers with all core frameworks with reasonable structure and the same or similar spatial structure as the lead compound. Researchers may find frameworks with novel structures, good physical properties and stable chemical properties in these core frameworks. After splicing pharmacodynamic groups on these skeletons, it can produce the same or similar biological activity as the original active compound.
Abstract:
Taking bump-type gas foil thrust bearing as the research object, a force and deformation model of bump foil and top foil were established by elastic mechanics analysis. The foil structure deformation was calculated and the gas film thickness equation was obtained. On this basis, a fluid-solid coupling model used for calculating the lubrication performance of bump-type gas foil thrust bearings was established with use of Reynolds equation for compressible gas. The established fluid-solid coupling calculation model was verified with specific literature, proving the reliability of the algorithm. With a specific example, the dimensionless gas film pressure distribution, dimensionless gas film thickness distribution and foil structure deformation distribution of the bearing were calculated numerically. The lubrication performance of foil thrust bearing and that of rigid thrust bearing were compared. It was found that the gas film thickness of foil bearing was bigger, while the bearing capacity and friction torque of it were smaller. The influences of bump foil thickness tB, half bump length l, bump radius R0 and top foil thickness tT on the lubrication performance of the bearing were studied, and relevant curves were obtained, which showed that bearing capacity and friction torque will increase as tB or tT increase, and decrease as l or R0 increase.
Abstract:
The magnetic polymer brushes contain a magnetic core and a polymer brush shell, which is a new type of core-shell structure composing of polymer chains closely grafted to the magnetic core surface at one end. The magnetic core could be either based on single magnetic nanoparticle or composite materials, at which the matrix to encapsulate the magnetic nanoparticles could be inorganic materials like silica or organic materials like polystyrene or poly(methyl methacrylate). The introduction of magnetic nanoparticles brings great convenience and functionality in the preparation process and practical application of polymer brushes. Functional magnetic polymer brushes could be recycled, separated, and purified by easy operation under external magnetic field. In the last decade, with the continuous development of preparation strategy of magnetic nanospheres and surface modification techniques of nanospheres, magnetic polymer brushes have been systematically studied on structure design, functionality and applications. Magnetic polymer brushes have broad application prospects in protein adsorption and purification, bioimaging, specific detection, and catalytic enhancement, etc. This paper reviews the latest research progress in magnetic polymer brushes and the future development direction is also anticipated.
[Abstract](1137) [FullText HTML](243) [PDF 1493KB](7)
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Cylindrical roller bearings are widely used in mechanical equipment. The inner and outer rings of such bearing are usually tightly fitted when assembling, which results in expansion of the inner ring and shrinkage of the outer ring, thus affecting the mechanical properties of the bearing. In this paper, based on the mechanical analysis and the thick-walled cylinder theory, a calculation model is established, which can be used to calculate the contact stress between the roller and raceways and calculate the axial orbit with considering the assembly interferences of inner and outer rings. An algorithm for numerical calcultion based on this model under different clearance values is constructed, and the force of each roller of cylindrical roller bearings can be accurately calculated. Upon using the established algorithm, taking the cylindrical roller bearing NU306E as an example, influences of assembly interferences of inner and outer rings on the contact stress and the axial orbit are studied, and curves of the maximum contact stress and the axial orbit are drawn. It is found that when the initial clearance keeps constant, as the interference increases, the range of the contact stress of the roller increases gradually. The maximum value of the contact stress of the roller decreases gradually. When the interference increases to a certain extent, the roller is stressed over the entire circumference, and the maximum value of the roller contact stress is increased significantly. When the bearing assembly interference keeps constant, as the initial clearance increases, the range of the roller contact stress decreases gradually, and the maximum value of the contact stress increases gradually.
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As a hot topic in the domain of text information mining, text clustering has been widely used in information retrieval, search engines, etc. However, short text has high dimensionality and sparsity of features, which make the clustering on short text face many challenges. Although a lot of efforts have been made to overcome the sparsity and high dimensionality of short text, there still exist many problems on how to further improve the quality of short text clustering. To this end, by means of biterm topic model (BTM) and paragraph vector (PV), this poper proposes a short text clustering method from the perspective of statistics and neural network algorithm, which includes two main steps: (1) Utilize the obtained word-document-topic probability distribution via BTM, in combination with the local outlier factor and JS divergence, to achieve semantic splitting of the words in the entire set of texts; (2) Input the above texts into the vectorization model PV-DBOW (Distributed Bag of Words version of Paragraph Vector) to obtain the paragraph vectors, which will further be combined with their corresponding document-topic probability distribution to form the eigenvectors of text feature. The proposed method can enrich the information carried by text features and ensures a low feature dimension. Finally, it has been shown via the experimental results that the obtained eigenvectors have stronger discriminative ability for short texts such that the clustering effect of short texts can be effectively improved, meanwhile, the negative effects of sparseness in short texts may be avoided.
[Abstract](6559) [FullText HTML](2408) [PDF 898KB](18)
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Nanopore detection technology plays important role in the field of single molecule detection. The feature extraction and transformation of nanopore blockade current is the key to classify signals and determine the analytes. Since the supervised learning can only predict the blockade current with known types, the unsupervised learning would be expected to achieve the distinction of the essential characteristics of signals. By means of the blockade current based on DNA carrier and the feature extraction of convolutional neural network, this paper proposes an unsupervised clustering scheme for nanopore signals. The proposed method combines the improved deep embedded clustering with the variational auto-encoder so that the feature transformation and the clustering of the blockade current can be jointly trained. In the original improved deep embedded clustering, the model utilizes an auto-encoder to transform the input data to a new compressed representation, which can reserve the crucial information of the input data. Thus, the auto-encoder may be replaced by a variational auto-encoder to learn the parameters of a probability distribution on the input data, instead of just learning the compressed representation. Finally, the proposed clustering model is firstly verified via 8 clustering centroids. Due to the symmetrical encoded DNA, like “100” and “001”, the case of 6 clustering centroids is further conducted to validate the proposed clustering model. It is shown from the experiment results that the proposed method can provide better clustering results for blockade current of DNA carrier, and achieves a 29% boost at most, compared with other clustering algorithms. .
[Abstract](441) [FullText HTML](136) [PDF 1332KB](2)
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Foam-based hyper-crosslinked polymers (HCfoams) were synthesized by Scholl coupling method using recycled polystyrene foams as the raw materials and aluminium chloride (AlCl3) as the catalyst. HCfoams exhibit high specific surface area, permanent porosity and well thermal stability. Shape-stabilized phase change materials (PCMs) composites were obtained by sorption of palmitic acid (PA) into the channel of HCfoams via vacuum impregnation. The specific surface area and pore size distribution of HCfoams were characterized by a nitrogen adsorption/desorption isotherm. The morphology, structure, thermal stability and latent heat of PA@HCfoams were characterized by scanning electron microscopy (SEM), X-ray diffractometer (XRD), Fourier transform infraredspectrometer (FT-IR), thermogravimetricanalysis (TG) and differential scanning calorimeter (DSC), respectively. The results show that HCfoam2 has a rich pore volume (1.25 cm3/g), suitable pore size (5.68 nm) and a large specific surface area (1 078 m2/g). PA was successfully adsorbed into the pores of HCfoams by physical binding. As indicated by the DSC tests, the composites have favorable encapsulation rate and phase enthalpies. For palmitic acid@HCfoam2 (PA@HCfoam2), its encapsulation rate reaches up to 77.53 %, and the latent heat values of melting and freezing were 148.50 J/g and 141.62 J/g, respectively, with the corresponding temperature of 66.4 ℃ and 56.2 ℃, respectively. PA@HCfoam2 showed excellent thermal reliability, with a load decreased by only 1.42% after 100 times cycling. In addition, compared with PA, the thermal conductivity of PA@HCfoam2 increased by 12.59%. All these results that the materials have broad prospects in thermal energy storage applications.
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In recent years, the number of clinical trials of adeno-associated virus (AAV) vectors for gene transfer in vivo has steadily increased. Excellent safety and efficient transduction of a wide range of target tissues make AAV vectors to be the platform of choice for gene therapy in vivo. However, due to the poor selectivity of AAV vector serotypes and target cells, the presence of AAV neutralizing antibodies, and the continuous occurrence of immune responses, the effect of gene therapy are seriously affected. For enhancing the liver targeting of AAV and making AAV silent against the body’s immune response. Recently, DNA shuffling was employed to produce an AAV cap gene library based on eight different AAV (AAV1-4, AAV6-9) capsid genes. DNA sequences in the mutant gene library were inserted into the plasmid containing the AAV2 Rep gene and the ITR sequence, and the resulting plasmid (pIRC) have a full set of AAV genomic sequences (>107 independent clones, ie, bacterial colonies). HEK293 cells were co-transfected, and the purified virus was collected after transfection for 72 h hours to obtain an AAV mutant library. Human liver cancer Hep G2 cells were assisted by wild type 5 adenovirus (wt Ad5). After screening, we finally obtained a capsid protein mutant AAVXL12 in hepatocytes. By infecting Hep G2 cells with different serotypes of recombinant AAV virus carrying the GFP gene, we observed different degrees of green fluorescence expression, which finally showed that the serotype vector AAVXL12 mediated GFP gene expression was the best. Therefore, the new AAV vector, which is highly infectious to human liver cells, has enhanced the efficiency of gene transduction and is expected to provide a novel therapeutic vector for AAV for gene therapy.
[Abstract](56) [FullText HTML](59) [PDF 1051KB](0)
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The CB (carbon black)/TPU (thermoplastic polyurethane) conductive composite was prepared by melt blending with using TPU as the matrix and conductive CB as the filler. The experimental temperature was 185 °C, the speed was 60 r/min with the CB/TPU mixture in a torque rheometer for 5.5 min and then pressed by a flat vulcanizer. The effects of CB content on electrical or dielectric properties, mechanical properties, microstructure and thermal stability of the materials were investigated. The relationship between the logarithmic resistivity and the amount of added carbon black was in accordance with the conduction path theory. When the CB content was less than 10%, the decrease of resistivity was not obvious; when the amount of added CB was increased from 10% to 14%, the resistivity of the CB/TPU composite was decreased sharply by 9 orders of magnitude, and the percolation zone of the CB/TPU material was between 10% and 14%; when the CB content was increased to be more than 16%, the resistivity was decreased slowly and reached a steady state, which were highly consistent with the classical inverse S-shaped percolation curve in region Ⅰ, Ⅱ and Ⅲ, respectively. As the CB content increased, the dielectric loss, dielectric constant and AC conductivity of the material were increased, the tensile strength and elongation at break of CB/TPU were increased first and then decreased, and ultimately reached the maximum values of 53.8 MPa and 1 066.7%, respectively. When the CB content was 4%, the tensile modulus was improved with the increase of CB content. The tensile fracture morphology of CB/TPU was changed from "river-like" morphology to high-low-staggered fracture stretching, and the conductive path was observed in SEM. The addition of CB improved the thermal stability of CB/TPU composites.
[Abstract](1369) [FullText HTML](313) [PDF 1496KB](5)
Abstract:
Silicon-containing arylacetylene resin(PSA) has been widely used in aerospace and electronic information field, because of it’s excellent process performance, high temperature resistance and dielectric properties. However, the dielectric constant of PSA resin still cannot meet the use of the very large scale integration (VLSI). Fluorine-containing silicon arylacetylene resins(PSAFs), which offered high temperature resistance and low dielectric constant, were synthesized through the reaction between long chain fluoroalkyltrichlorosilane and phenyldiethynylmagnesium bromide, and their structures were characterized using FT-IR, 1H- NMR and 19F NMR. The rheological properties and cure behavior of the PSAFs resins were investigated by the rotational rheometer and DSC. The thermal stability and dielectric properties of the cured PSAFs resins were analyzed by thermogravimetric analysis and dielectric spectrometer. The results showed that the PSAFs resins had good processability, and the processing window was under the temperature ranging from 40 ℃ to 150 ℃. The incorporation of fluorine into silicon-containing arylacetylene resin improved the dielectric properties, and the dielectric constants of the cured PSAFs resins can tuned from 2.43 to 2.62, and the dielectric loss were varied from 0.003 0 to 0.005 8 under 1 MHz, respectively. Moreover, the dielectric constant was decreased with the increase in fluorine content, but the dielectric loss did not change significantly. The 5% weight loss temperature of the cured PSAF1 and PSAF2 resins under nitrogen atmosphere were 430 ℃ and 416 ℃, and the decomposition residue at 1 000 ℃ were 42.3% and 34.7%, respectively.
[Abstract](102) [FullText HTML](78) [PDF 831KB](2)
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Particle size and surface charge of nanoparticles have important impacts on drug delivery process. Conventional preparation and tuning of particle features e.g. surface charge are difficult and time consuming. In this work, a pH-responsive spherical drug-loaded nanoparticles was prepared by encapsulating a hydrophobic drug β-carotene in biocompatible copolymer poly(ethylene glycol)- b -polycaprolactone (PEG- b -PCL) and poly(2-(dimethylamino) ethylmethylacrylate)- b -polycaprolactone (PDMAEMA- b -PCL) via flash nanoprecipitation (FNP) method in a multi-inlet vortex mixer (MIVM). Particle size and surface charge of nanoparticles at different pHs were investigated. By changing the feed ratio of the two polymers, surface charge of the nanoparticles can be tuned from +32.4 mV to −4.7 mV. Meanwhile, as the ratio of PEG- b -PCL was increased, the surface charge decreased due to the decrease of amine content from the PDMAEMA block. The size of the nanoparticles can be adjusted by changing the feed flow rate into the MIVM by which the flow rate of organic phase v 1 was kept at 12 mL/min and the flow rate of water v 2 was increased from 24 mL/min to 96 mL/min, the nanoparticles size was decreased from 126.6 nm to 62.7 nm. also It was also found that when the flow rate ratio of v 1/ v 2 was kept at 1∶4 and v 1: v 2 was increased from 6∶24 to 24∶96, the nanoparticles size can be reduced from 107.5 nm to 77.3 nm. The s nanoparticle is stable for 25 days at pH=7.4. As a conclusion, by the strategy of flash nanoprecipitation, the spherical drug-loaded nanoparticles can be rapidly prepared and particle size and surface charge can be accurately modulated easily providing potential applications for cancer diagnosis and treatments in future.
[Abstract](111) [FullText HTML](70) [PDF 1346KB](1)
Abstract:
Spodumene is one of the exploited and utilized lithium resources in the world, which is often associated with feldspar, quartz and other minerals. There are a lot of silicon resources in spodumene, so it is of great value to synthetically utilize the silicon resources in spodumene. The spodumene ore from Jiangxi Province was used as raw material, while the NaOH solution was applied as reactant. The leaching behaviors of Si, Li, Al from spodumene ore were studied. The influences of different parameters, including leaching time, stirring speed, leaching temperature, alkali-to-ore mass ratio and NaOH mass fraction on the leaching rates of Si, Li, Al were investigated. The mineralogical structure and microstructures of spodumene ore and concentrate were characterized by X-ray diffraction (XRD) analyzer and scanning electron microscope (SEM), and the desilication leaching process was analyzed as well. Central composite design(CCD), a kind of response surface methodology, was employed to investigate the effects of leaching time, leaching temperature, alkali-to-ore mass ratio and NaOH mass fraction on the leaching rates of Si and Li. The optimal leaching conditions were thereby obtained as following: 3.7 h, 215 ℃, 1.15, 16%. Under the conditions, the optimal predicted values were: leaching rate of Si 74.55%, leaching rate of Li 3.31%, while the corresponding experimental results were 73.41% and 3.33%, respectively. The errors between the predicted and experimental values were ignorable. which indicated that the established models could analyse and predict the desilication process in alkaline leaching of low-grade spodumene ore accurately and reliably.
[Abstract](8861) [FullText HTML](2370) [PDF 2004KB](12)
Abstract:
p-Propargyloxyphenyl side groups were grafted to the backbone of novolac-type cyanate ester (NCE) by diazo coupling reaction to obtain a new novolac resin (PPANC) with cyanate ester and propargyloxyphenyl side groups. The resins were characterized by 1H-NMR, FT-IR, UV-Vis and size exclusion chromatography (SEC). The thermal cure reaction of PPANC was studied by differential scanning calorimetry (DSC) and in situ monitoring Fourier-transition infrared. Furthermore, quartz fabrics (QF) reinforced PPANC composites were also molded using hot-press process. The thermal stability of the resins and the mechanical and dielectric properties of the composites were also studied. The results showed that the propargyloxyphenyl side groups in the prepared PPANC could promote the curing reaction of cyanate ester groups attached on NCE as facilitated by the acidic hydrogen of the terminal alkynyl groups. The curing temperature of the NCE resins decreased with the introduction of the propargyloxyphenyl groups, and further decreased with increase of the propargyloxyphenyl content. The thermal stability of the cured PPANC resins in nitrogen decreased with increase of the propargyloxyphenyl content. However, the temperature at 5% mass loss of the cured PPANC resins retained higher than 400 °C. The PPANC resin with a moderate propargyloxyphenyl content was reinforced by QF to form the composite which showed higher mechanical properties and lower dielectric properties than those of the composites of NCE and PPANC matrices. The flexural strength and modulus, and interlayer shear strength (SILS) of the QF/PPANC composite could reach 612 MPa and 26 GPa, and 52 MPa, respectively. The glass transition temperature of the QF/PPANC composites and QF/NCE composite were higher than 350 ℃. The dielectric constant and dissipation of the QF/PPANC composites were lower than 3.6 and 0.004, respectively. These values are lower than those of the QF/NCE composite in the frequency range of 1~106 Hz.
[Abstract](7787) [FullText HTML](1945) [PDF 888KB](8)
Abstract:
In propylene polymerization catalyzed by transition metal complexes, chain transfer reactions exert crucial influence on the structures of terminal groups as well as molecular weights of the resultant polymers. Among the known chain transfer reactions, β-methyl elimination (β-Me elimination) could lead to the production of ally-terminated polymer chain selectively, thus attracts great attention. Up to data, it is still a great challenge to achieve high β-Me elimination selectivity systematically during propylene polymerization process. In this work, a series of ethylene-bridged indenyl-fluorenyl complexes, {C2H4(5,6-cyclopenta-Ind)(Flu)}ZrCl2(C1), {C2H4 (5,6-cyclopenta-Ind)(2,7-tBu2-Flu)}ZrCl2(C2), {C2H4(3-Bn-5,6-cyclopenta-Ind) (2,7-tBu2-Flu)}ZrCl2(C3), {C2H4 (3-Bn-5,6-cyclopenta-Ind)(2,7-tBu2-Flu)}HfCl2(C4), were synthesized and characterized. Upon activation with methylaluminoxane(MAO), these complexes could catalyze the polymerization of propylene with moderate to high activities to produce propene oligomers or polymers with vinylidene or allyl-dominant chain ends. Complex C3 bearing a benzyl group at the 3- position of the indenyl ring showed significantly higher β-Me elimination selectivities (80-83%) at 40-100°C than the other zirconocene complexes C1 and C2, and meanwhile led to the formation of propene oligomers with significantly lower molecular weights (Mn = 800~13 600) than those obtained by the other zirconocene complexes, suggesting that the dominant β-Me elimination chain transfermode led to the decrease of molecular weights of resultant polymeric products. The hafnocene complex C4 also showed the highest β-Me elimination selectivity among these complexes (87%), however its activity were very low.
[Abstract](671) [FullText HTML](112) [PDF 1098KB](1)
Abstract:
Cucurbit[n]urils (CB[n]s) are macrocyclic host molecules with polar carbonyl groups on both portals, which enable CB[n]s to bind strongly and selectively with cationic species, especially to protonated organic amines. Here, a novel supramolecular polymer has been successfully constructed by the self-assembly between a cucurbit[5]uril analogue (decamethyl substituted methylene bridge cucurbit[5]uril, Me10TD[5]) and 1,3,6,8-tetrakis(4-aminophenyl)pyrene tetrahydrochloride salt in aqueous solution through portal interactions. Diverse measurements were used to characterize the formation of this polymer, including fluorescence emission spectrum, 1H nuclear magnetic resonance (NMR) spectroscopy, dynamic light scattering (DLS) and transmission electron microscopy (TEM). The 1H NMR measurements and the job's plot indicate that Me10TD[5] and 1,3,6,8-tetrakis(4-aminophenyl)pyrene tetrahydrochloride salt are combined in a ratio of 1:2. The association constant (Ka) was calculated to be (7.1 ± 0.7) × 104 M-1 by non-linear curve-fitting method based on the fluorescence experiments. Transmission electron microscopy image and the dynamic light scattering measurements demonstrate that 1,3,6,8-tetrakis(4-aminophenyl)pyrene tetrahydrochloride salt and Me10TD[5] could self-assemble into supramolecular polymers and this self-assembly behavior will lead to a certain degree of red shift of the maximum emission wavelength along with the decrease in fluorescence intensity. Meanwhile, the recognition performance of the polymer on metal ions was studied. Upon the addition of Ba2+, Ca2+, Co2+, Ni2+, Pb2+, Zn2+, Fe2+, Mg2+, Cd2+, Mn2+, Cu2+, it was found that Ba2+ can significantly enhance the fluorescence of the system and has a certain degree of anti-interference. Therefore, this polymer can be used to detect Ba2+, and the detection limit of the polymer for Ba2+ is 7.6 × 10-6 mol/L.
[Abstract](559) [FullText HTML](165) [PDF 1562KB](3)
Abstract:
By controlling the molar ratio of D-enantiomer to L-enantiomer of the lactide, a series of di-stereoblock polylactides (di-sb-PLA) bearing similar block sequences between poly(D-lactide) (PDLA) and poly(L-lactide) (PLLA) were synthesized by ring-opening polymerization of L-lactide (L-LA) using hydroxyl terminated PDLA (HO-PDLA) as a macromolecular initiator. Ultrafine fibers were then fabricated by electrospinning di-sb-PLAs from their dichloromethane (DCM) and hexafluoroisopropanol (HFIP) mixtures. The thermal properties, mechanical properties, fiber morphology and crystallization properties of di-sb-PLAs were analyzed. The results of DSC examination showed that di-sb-PLA formed complete stereocomplex(sc) crystals with the melting point of higher than 215 ℃, and no homocrystal was formed. The crystallization ability of sc was decreased with the increase in length of each block. It is worth to note that sc of stereoblock PLA was formed on molecular-scale without post-processing when compared with PLA homopolymers, which enhanced the heat resistance and improved the elongation at break of casted films to 250% without losing tensile strength, especially for di-sb-PLAs that has higher molecular weight. After electrospinning, the as-spun micro/nanofibers of di-sb-PLA were homogeneous and smooth, in which PLA molecules were almost amorphous. A large amount of sc crystals were then formed by cold crystallization during heating-up process, and 8 ℃ in the melting points of sc crystals in these fibers were increased as compared with the melt-quenched samples. Moreover, the results of in-situ ATR-FT-IR at variable temperature disclosed that the formation of sc crystals was related to the interactions between side methyl groups and carbonyl groups in PLA. The results hold promise for the further application of di-sb-PLA.
[Abstract](861) [FullText HTML](157) [PDF 1397KB](1)
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The lignin-based film was obtained by addition polymerization of lignin and polycaprolactone (PCL) though hexamethylene diisocyanate (HDI) as the linking agent and stannous isooctylate as the catalyst. The structure and properties of the materials were characterized by infrared spectroscopy (FT-IR), NMR, XRD, thermogravimetry (TG), mechanical properties, contact angle, UV test and scanning electron microscopy (SEM). The effects of lignin content, isocyanate fraction and molecular weight of PCL on the properties of the films were also investigated. The results showed that the biodegradable soft polycaprolactone was successfully introduced into the lignin. The initial degradation temperature rose to 338.10 ℃ at the lignin content of 36.36%, indicating that the modification enhanced the thermal stability of lignin. The obtained film was flexible without breaking and exhibited prominent mechanical strength, the elongation at break and tensile strength of the film could reach 1114.84% and 17.66 MPa at the lignin content of 9.09%. With the increase of lignin content, the mechanical properties of the film decreased, but when the lignin content was 27.27%, the elongation at break, tensile strength and elastic modulus of the film could still reach 235.09%, 24.70 MPa and 262.49 MPa, respectively. Furthermore, the hydrophilic properties of the film was tunable according to the composition which could be adjusted as needed in practical applications. Exceptionally, UV absorption test manifested that the films had extraordinary UV-shielding property and could block against 100% UV light in the UV region (290-400 nm). Thus these lignin-based films have great prospect for diverse promising applications, such as agricultural fields, packaging areas and UV-shielding biomaterial fields.
[Abstract](8061) [FullText HTML](3071) [PDF 970KB](31)
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This paper uses EEG dataset DEAP to undergo the emotion recognition. By considering the time sequence characteristics of EEG signals, we adopt temporal convolution network (TCN) as a deep learning approach to train and identify EEG data. TCN model can not only grasp the characteristics of time series, but also retain the parallel computing property of CNN. Hence, it can improve the computational efficiency, while maintaining high identification accuracy. Firstly, wavelet packet transform is employed to decompose the raw signals into sub-frequency bands, and then, wavelet coefficient energy values are computed as the features. Wavelet packet analysis is an extension of wavelet analysis, whose basic idea is to concentrate the information energy, find the order in the details, and filter out the rules. Hence, it can provide a more sophisticated analysis method for the signal. Besides, the extracted features are trained through the TCN and Snapshot optimization idea is adopted for saving multiple models during the process of training. The principle of Snapshot optimization is to avoid local pole values by constantly resetting the learning rate. Finally, the ensemble learning with the voting integration strategy is implemented to combine multiple machine learning models into an integrated model such that the recognition accuracy can be improved and the robustness of the results can be enhanced. Finally, it is shown via the experimental results that the proposed method can realize the two-category and four-category identification tasks of emotions with the average recognition accuracy, 95% and 93%, respectively. Compared with similar methods, this proposed method attains significant improvement.
[Abstract](6458) [FullText HTML](2124) [PDF 805KB](8)
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In the chemical laboratory, the laboratory staff often forget to close the fume hood window in time before they leave, which may cause potential safety hazards and the waste of energy. Therefore, it is necessary to develop a methodology for the safety management of fume hood window. To the best of the authors’ knowledge, the related research works about window status recognition are mainly through various electronic control systems, which are not suitable for fume hood window. By using computer vision with the advantages of non-contact and easy expansibility, this paper proposes a novel safety management method for fume hood window. Firstly, the surveillance videos are preprocessed and these areas of fume hood window are extracted via motion features and geometric priority. This can effectively reduce the influence of irrelevant area on window status recognition. Due to the lack of available data set and the limitation of the number of fume hood windows in the laboratory, this paper constructs a new data set containing 400 window images. By using few-shot learning, this paper proposes a recognition method on the status of fume hood window. Compared with the traditional few-shot learning dataset, fume hood window images have higher resolution such that it is difficult to extract effective features. To overcome this significant challenge, this paper applies dilation convolution to enlarge receptive field and constructs the inception layer with multi-scale dilation rate instead of traditional convolution layer. In order to avoid invalid detection on the window status while staff are in the laboratory, we use the moving foreground region extracted from the Gauss mixture model as the prior region of Yolov3 (You only look once version 3) target detection such that the error recognition can be greatly reduced. In the simulation experiment, the proposed method is compared with the traditional machine learning algorithm and CNN(convolutional neural network). LBP (local binary pattern), PCA(principal component analysis), ColorHist(histogram of color) and HOG(histogram of oriented gradient) are selected as the features of machine learning methods from the aspects of texture, dimension reduction, color and shape. It is shown via the experimental results that the proposed method can achieve 99.29% accuracy under normal illumination conditions, 17.20% higher than the best traditional HOG combined with Randomforest method and 10.95% higher than the convolution neural network. Under the condition of illumination change, the accuracy is 95.74%, which is less changed than the one under normal illumination.
[Abstract](1986) [FullText HTML](410) [PDF 1320KB](4)
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Photodynamic Therapy (PDT) is a novel non-invasive treatment protocol for cancer therapy, which is usually consisted of three nontoxic components: photosensitizers (PSs), light with a specific wavelength and molecular oxygen. Upon the light irradiation with suitable wavelength, PSs absorb the light energy to reach the excited state and further transfer their excited-state energy to the surrounding oxygen inducing the generation of reactive oxygen species (ROS), such as singlet oxygen (1O2), hydroxyl radical and hydrogen peroxide. The resulting Res can rapidly oxidize key cellular biomacromolecules leading to tumor cell apoptosis. Porphyrin and its derivatives, which are widely existed in organisms and participate in essential physiological processes, are well-known and promising photosensitizers. However, many drawbacks, such as strong hydrophobicity and self-quenching induced by aggregation, have greatly limited their applications in PDT. Herein, a series of water-soluble porphyrin semitelechelic polymers (TPP-PEG) were successfully synthesized via click reaction between hydrophilic polyethylene glycol chains with various molecular weight (PEG, Mn=1 000, 2 000, 5 000) and tetraphenyl porphyrin unit (TPP). Compared with small porphyrin molecules, these PEGlated porphyrin semitelechelic polymers exhibit excellent solubility in aqueous solution, greatly reducing the intermolecular π-π stacking and thereby enhancing the singlet oxygen generation. In addition, the introduction of PEG chains also improves the biocompatibility of the porphyrin photosensitizer. Using 1,3-diphenylisobenzofuran (DPBF) as the 1O2 detecting probe, the UV-vis absorption intensity results show that the 1O2 generation of TPP-PEG are faster and more extensive than the free TPP molecules. Additionally, the results indicate that the 1O2 generation capability of TPP-PEG decreases with the increase of the lergth of PEG chain. The MTT assay results of dark cytotoxicity and phototoxicity in HeLa cells also confirmed that TPP-PEG possesses good biocompatibility and high cytotoxicity under light irradiation.
[Abstract](1167) [FullText HTML](631) [PDF 854KB](3)
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Since the industrial revolution, the use of fossil fuels has led to a sharp increase in CO2 emissions, which has caused a series of environmental problems. Therefore, the conversion and utilization of CO2 have become one of the most important green chemistry research topics. Among them, the preparation of methanol from CO2 is considered as a promising resource utilization way. The effects of operating conditions on the hydrogenation of CO2 to wards methanol were investigated in an isothermal integral reactor. The experimental results show that under the experimental conditions, higher conversion of CO2 and yield of methanol can be obtained at a reaction temperature of 240.0 ℃, higher reaction pressure and ratio of hydrogen to CO2. Meanwhile, the intrinsic kinetics of hydrogenation of CO2 towards methanol was studied on a Cu/ZnO/Al2O3 modified catalyst with 80-100 meshes under the condition of 240.0~280.0 ℃, 4.00~8.00 MPa and feed gas nH2/nCO2 3.0~3.4. Orthogonal method was used to design experiments and measure the kinetic data. A double-rate intrinsic kinetic model expressed by the fugacity of each component was deduced by taking the hydrogenation of formate as the rate control step, and its kinetic parameters were estimated by the maximum inheritance method. The statistical test, physicochemical meaning analysis and residual analysis results of the models show that both the kinetic models are applicable, and the relative error of the proposed double-rate kinetic model is smaller than that of the model of CO generation by direct dissociation and adsorption of CO2 in the literature.
[Abstract](83) [FullText HTML](67) [PDF 1145KB](1)
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Research based on the ultra-short baseline positioning system and Doppler velocimeter and electronic compass combination of underwater robot navigation problem, put forward a kind of based on iterative unscented Kalman filtering fusion algorithm of multi-sensor underwater integrated navigation, reduce traditional unscented Kalman filter process noise covariance matrix and measurement noise covariance matrix of the influence of the filtering precision and response time. The proposed method improves the precision of underwater multi-sensor combined navigation by iterating the results of multi-sensor data fusion several times. Firstly, the data obtained by the sensors were preprocessed. Secondly, plot the motion trajectory diagram simulated by the ultra-short baseline positioning system, the motion trajectory diagram calculated by dead reckoning and the motion trajectory diagram fused by the unscented Kalman filtering algorithm were drawn respectively. Thirdly, the unscented Kalman filtering algorithm iterates the output of multi-sensor data fusion for several times, which can achieve a better fusion effect. Finally, the feasibility and effectiveness of the combined navigation algorithm under the water are verified by multi-sensor pool test and simulation analysis. The effectiveness of the iterative unscented Kalman filtering algorithm based on underwater integrated navigation system was verified by comparing the simulated ultra-short baseline positioning data, the dead reckoning data based on the electronic compass and Doppler velocimeter and the position information of the positioning data fused with the iterative unscented Kalman filtering data.
[Abstract](777) [FullText HTML](154) [PDF 5206KB](0)
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[Abstract](121) [FullText HTML](67) [PDF 1148KB](1)
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The photocyclization quantum yield of traditional diarylethene systems is always limited to 50% (mol%) due to the inseparability of the parallel (p-) and anti-parallel (ap-) conformers. However, it is possible to block the conversion between the two conformers by increasing steric hindrance between the side aryl groups and ethene bridge, thus enhancing the photocyclization quantum yields. Herein, based on the sterically-hindered bisbenzo(thiadizole) ethene bridge, we fully compared the steric effect of side thiophene rings, and got insight into the electronic effects of substitution groups, like the electron-donating, such as anisole unit and the electron-withdrawing pyridine units. The parallel and antiparallel conformers of compounds 1 and 3 can be separated successfully upon introducing the sterically hindered methyl group to the β-position of thiophene rings, thus greatly improving their photocyclization quantum yields, higher than 50% (mol%). Moreover, the incorporated steric hindrance of β-methyl groups on thiophene rings results in lower thermal stability of 1c and 3c. In contrast, 2c and 4c show good thermal stability which can be attributed to the relatively small steric hindrance and intramolecular hydrogen bond. When compared with the electronic effects, the electron-withdrawing effects of pyridine units brings forth the higher thermal bleaching rate of 1c than that of 3c containing the electron-donating anisole units.
[Abstract](123) [FullText HTML](72) [PDF 1106KB](0)
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To study the influences of vacuum freeze-drying on the active constituent of Panax notogiseng (P. notoginseng), and approach an optimal drying process with the content of Panax notoginseng Saponins and Dencichine. The single factor experiment was utilized combining with response surface methodology and satisfaction function to optimize the drying process of P. notoginseng. On the basis of single factor experiments, different optimum conditions of clapboard temperature and vacuum pressure were selected, and the method of response surface analysis were adopted according to the Central Composite Design (CCD) experimental design principles. In addition, the P. notoginseng quality was evaluated by the scanning electron microscope(SEM). The optimum drying conditions of the P. notoginseng are as follows: vacuum pressure of 56.9 Pa, the clapboard temperature of 45.2 ℃. Under the optimal drying conditions, the average Panax notoginseng Saponins and Dencichine content could reach 9.77% and 1.76%. The satisfaction function results shown that the expected value of the optimum process conditions is 4.353. The average value of three demonstration tests is 4.276. The results are similar to the predicted value of the model. This technology could be used to guide industrial production of P. notoginseng and provide a theoretic basis.
[Abstract](100) [FullText HTML](63) [PDF 1089KB](2)
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How to characterize the cross-section quality after blanking test is a difficult problem in the punching industrial field. At present, the main evaluation method for the cross-section quality is to measure the relative ratio of smooth-sheared length and fracture length. However, the relative length ratio can’t reveal the complexity of the fracture surface and can’t fully characterize the details of the cross section profile. As a promising theory, fractal theory has been widely used in the metal research field and has a great advantage on the quantitative characterization of the quality of blanking cross sections. Based on the Mandelbrot fractal theory, the relative length ratios of different blanking cross sections were measured and the fractal dimension of each fracture surface were calculated. The research found that with the decrease of the fractal dimensions of the blanking cross section, the quality of fracture surface becomes better. The numerical simulations of the blanking process show that the smooth fracture zone is determined by the shear stress, and the fracture zone is determined by the tensile stress. The study results showed that the upper limit of fractal dimension for the blanking section can be estimated by measuring the fractal dimension of the fracture profile of tensile specimen.
[Abstract](154) [FullText HTML](86) [PDF 789KB](0)
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A drug delivery system was designed in this paper. The system was composed of (6,5) chiral single-walled carbon nanotube ((6,5)SWCNT), doxorubicin hydrochloride (Dox), human serum albumin (HSA), and folic acid (FA). Firstly, the Dox-HSA-FA was prepared. (6,5) SWCNT was isolated by aqueous two-phase extraction. Then (6,5) SWCNT-Dox-HSA-FA was dispersed into Dox-HSA-FA by ultrasonication. Finally, cytotoxicity evaluation of the complex was performed using Hep G2 cells. The results showed that the IC50 of Dox-HSA-FA and (6,5) SWCNT-Dox-HSA-FA were 27.3 μg/mL and 25.7 μg/mL. The results indicated that the targeting effect of Dox was enhanced in the (6,5) SWCNT-Dox-HSA-FA complex.
[Abstract](208) [FullText HTML](83) [PDF 784KB](1)
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A Mach-Zehnder interferometer demodulation scheme based on slow light in electromagnetically induced transparency medium is proposed and applied to improve the sensing sensitivity of fiber Bragg grating strain sensors. Theoretical studies have found that higher group refractive index can be obtained under suitable control field conditions by the common Λ-type three-level atomic system, and the sensing sensitivity of fiber Bragg grating strain sensors is improved. The influence of the control field on the sensing range and sensing sensitivity is further analyzed. According to the theoretical calculation, when the control field G=60 MHz, the sensitivity of fiber Bragg grating strain sensor based on Mach-Zehnder interference demodulation can be increased by about 3000 times. The proposed strain sensor demonstrates a high sensitivity of -40 Rad/uε and strain measurement range of -50 nε~50 nε.
[Abstract](399) [FullText HTML](126) [PDF 1018KB](2)
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Over the past few decades, Lithium-ion batteries (LIBs) have attracted extensive interests in energy storage devices due to their high energy density, long cycle life and environmental friendliness. However, the conventional anode materials with low specific capacity restrict the commercial applications of LIBs. Therefore, it is crucial to develop advanced electrodes for next-generation LIBs to meet the ever-increasing energy requirements. Metal-organic frameworks (MOFs) is a potential candidate for anode materials due to its high surface area, controlled pore size and structural diversity, but its poor conductivity and easy aggregation often result in the decline of electrochemical performance of LIBs.　　To further improve the overall performance of MOF as anode materials for lithium ion batteries, electrostatic attraction and chemical liquid deposition methods were developed to fabricate CoNi-MOF/RGO composite nanoflakes by using reduced graphene oxide (RGO) as substrate, cobalt chloride and nickel chloride as precursors, and benzenedicarboxylic acid as organic ligands. The addition of RGO not only induces the structural transformation of CoNi-MOF from cross-linked lamellae to two-dimensional nanoflakes, but also enhances the conductivity of CoNi-MOF/RGO composite. Subsequently, the coin type Lithium ion battery was assembled by using CoNi-MOF/RGO as anode materials for lithium ion batteries. The electrochemical tests indicated that CoNi-MOF/RGO electrode possessed a high charge specific capacity of 747 mA·h/g at a current density of 0.2 A/g after 100 cycles. Even at high current density of 5 A/g, a high capacity of 289 mA·h/g was still achieved, which is much higher than that of CoNi-MOF, demonstrating its excellent electrochemical performance.
[Abstract](296) [FullText HTML](147) [PDF 720KB](2)
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Aluminum doped Zinc Oxide (AZO) thin films with TiO2, SnO2 and ZnO buffer layers were deposited on flexible PET substrates by intermediate frequency reaction magnetron sputtering method at room temperature. The effects of different buffer layers on the photoelectric properties and bending resistance performance of flexible AZO films were investigated. The results show that three kinds of buffer layers improved the electrical properties of the flexible AZO thin films. The AZO thin film with SnO2 buffer layer deposited Ar/O2 ratio of 5:1 has the best performance, of which the reducing rate in the resistivity reaches 90% and the average optical transmittance is over 85% in the visible range. The changes in the electrical resistance of the flexible AZO thin films under cyclic bending condition were studied. The AZO thin film with SnO2 or ZnO buffer layer exhibit an excellent electrical stability after inward repeated bending cycles, at steps of 100, to a maximum number of 1 000, with radius fixed at 1.2 cm, for which the relative resistance increment was always below 10%, whereas the dramatic increase of the electrical resistance is more than a factor 250 already after 800 cycles of bending for the as-grown ones. The TiO2 and SnO2 buffer layers were found to be better when the AZO films are outward bent at the same cycles, and their relative resistance increment was maintained at about 6% and 12%, respectively.
[Abstract](92) [FullText HTML](75) [PDF 802KB](1)
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The influence of temperature, H2 pressure, hydrogen donating capabilities and catalyst on the hydroliquefaction of Hongliulin coal under mild conditions was investigated in this paper. The results show that in the range of 370~390 ℃, higher reaction temperature could promote the pyrolysis reaction of coal; in the range of 390~430 ℃, higher reaction temperature could promote the secondary cracking of heavy products. With reaction temperature increasing, the reaction pressure needs to be increased to match the reaction temperature. Moreover, compared to coal liquefaction under mild condition with recycle solvent and Fe catalyst, the effect of Fe catalyst addition on liquefaction performance with methylnaphthalene is tiny, which could be result from weak hydrogen transfer ability of methylnaphthalene. Fe catalyst has a little effect on liquefaction performance with tetralin as solvent. It could be due to that tetralin is a good hydrogen donor solvent which dissociates a large amount of activated hydrogen could stabilize most of the free radicals produced from Hongliulin coal pyrolysis, and with the addition of Fe catalyst, the activated hydrogen produced from H2 is more than needed for Hongliulin coal liquefaction process. Furthermore, the addition of alkali catalyst to Fe catalyst could promote coal conversion, oil production and H2 consumption, while reducing water production. It could be ascribed to there exists a prominent synergistic effect between alkali catalyst and Fe catalyst in Hongliulin coal hydroliquefaction, and the synergistic effect could promote the hydrolyzation of oxygen-containing moieties (such as carbonyl groups and ether bonds) and the depolymerization of macromolecular structures.
, doi: 10.14135/j.cnki.1006-3080.
[Abstract](707) [FullText HTML](182) [PDF 710KB](3)
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A polynomial-time topological reduction plays an important role in the computation of diameter constrained reliability, because many irrelevant edges are able to be deleted and the reliability remains unchanged. However, irrelevant edges cannot be completely found from previous researches. The necessary condition of detecting irrelevant edges is a so-called open problem. In this paper, we define new metrics of path lengths, classify st-paths as real path (RP), pseudo path (PP), combination path (CP) and the shortest st-path containing a specific edge (SPE), and make it clear that the length of SPE can be approached by measuring PPs, RPs and CPs. Further, we propose an algorithm to detect innermost irrelevant edges and the complexity of the algorithm is polynomial (O(n4)). Experiment results show the effectiveness and efficiency of the algorithm.
[Abstract](134) [FullText HTML](81) [PDF 954KB](2)
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In this study, continuous and single crystal graphene films on copper (Cu) are synthesized by low pressure chemical vapor deposition (LPCVD) in the growth time of 40 minutes with the meticulously modulation of the oxygen and carbon supply in multistages synthesis processing and graphene properties dependence on the oxygen and carbon supply has been investigated. Optical microscope, field emission scanning electron microscope (FESEM) and atomic force microscope (AFM) are employed for morphology characterization while the graphene films structure are measured by transmission electron microscope (TEM), selected area electron diffraction (SAED) and Raman spectrum. It is found that double oxygen passivation (with the oxygen passivation in both nucleation and growth stages) together with the optimal methane (CH4) : hydrogen (H2) ratio will lead to the balance between nucleation and graphene growth rate to accomplish continuous single crystal bilayer graphene films in short time. The remarkable properties difference between the graphene processed by single and double oxygen passivation as well as the strong properties dependence on ratio of CH4:H2 with double oxygen passivation indicate that the nucleation and growth of graphene domains can be properly modulated by the oxygen passivation and carbon supply. Moreover, the graphene-based field effect transistor (FET) reveals the superior hole mobility of 4347 cm2 V-1s-1. Our study provides a simple LPCVD procedure to achieve high quality graphene film on Cu in short time.
[Abstract](278) [FullText HTML](146) [PDF 660KB](1)
Abstract:
A defense method for linear deception attacks using KL divergence detector to detect watermarks in cyber physics system (CPS) is proposed. It is well known that linear deception attacks can degrade the performance of the remote estimator without being detected by the KL divergence detector. In order to detect such attacks, computer-based encryption methods use watermarks to encrypt and decrypt data transmitted over a wireless network to protect the system. When there is no attack, the decryption section can recover the transmitted data to ensure remote estimation performance. In the case of linear deception attacks, these data will be watermarked to expand the variance of the transmitted data, so that the data at the receiving end will no longer obey the original normal distribution. Due to the convex nature of KL divergence, the KL divergence value can be proved. It is enlarged to exceed the thresholds that have been tested by the detector so that they can help the KL divergence detector to detect the attack. The watermark encryption method has been proved to help the KL divergence detector to detect attacks or to mitigate the effects of attacks in different situations, and further discusses how to select the appropriate value of the watermark parameters, which makes the system's protection more perfect. Finally, numerical simulations are given to further illustrate the limitations of the existence of watermarks on attackers, further highlighting the practical effects of parameter selection.
[Abstract](123) [FullText HTML](80) [PDF 832KB](1)
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Poria cocos, known as FuLing in Chinese, is a traditional Chinese medicinal herb. Poria cocos polysaccharides (PCPs) were extracted by water extraction and alcohol precipitation method from P. cocos collected from different origins. High performance liquid chromatography (HPLC) was applied to establish the fingerprint for 16 batches PCPs. A macrophage cell line Raw274.7 was incubated in the different concentration of 16 batches PCPs. The immunological activity was evaluated based on the proliferation activity of cells as determined by MTT assay and NO production. The immunological activity of 16 batches PCPs were introduced into orthogonal partial least squares analysis to investigate the correlation between monosaccharide compositions and immunological activity. The results showed that PCPs were composed of eight monosaccharides, including Glc, Gal, Man, Fuc, GlcN, GlcA, Xyl and Ara. The similarity analysis showed that the similarity of the 16 batches PCPs ranged from 0.981 to 1. All the 16 PCPs showed well immunological activities, according to the in vitro activity evaluations. Mouse macrophages were stimulated with different concentrations of PCPs. NO production increased with the increase of PCPs concentration, which was higher than that of the blank. According to the orthogonal partial least squares analysis, all the monosaccharides from PCPs had relationship with immunological activity. Gal, Ara, Man and Glc were positively correlated with the immunological activity of mouse macrophages. Fru, GlcA, GlcN and Xyl were negative correlated with the immunological activity of mouse macrophages. Particularly, Glc, Gal and Man in PCPs were significantly contributed to the NO production from mouse macrophages.
[Abstract](256) [FullText HTML](113) [PDF 687KB](2)
Abstract:
Riboflavin is considered to play a crucial role in metabolic pathway. Commercial riboflavin has been widely applied in a variety of different industries, for instance, pharmaceuticals, cosmetics, human and animal nutrition etc. Recently, riboflavin product is mainly derived from biological process in industrial production. However, the focus of research has been placed on molecular modification of production strain genes, for which there is little attention paid to the analysis of metabolic flux regulation during metabolism, with nitrogen regulation in particular. This work is aimed to explore how the interaction of inorganic nitrogen sources affects the riboflavin yield and cell density and how the ammonium ion concentration causes effect on the whole process in fed-batch culture. In the experiment, it was discovered that ammonium is effective in promoting the biomass but exerts an inhibitory effect on the yield. On the contrary, nitrate is beneficial to improve the output of riboflavin but has some adverse effect on biomass. In this work, ammonium and nitrate were employed with a 1:8 ratio. The riboflavin yield was observed to reach 812 IU mL−1, a 30% increase as compared to when ammonium alone was used under the identical condition. In fed-batch culture, ammonia is frequently involved in the regulation of pH to ensure nitrogen supply. Nevertheless, a careful control over its concentration is needed. In 7 L bioreactor, glucose concentration was in the range of 5—10 g L−1 or so and the concentration of ammonium was restricted to below 10 mmol L−1 in the late fermentation. As a result, DCW was 74.5 g L−1 and the riboflavin yield increased to 4573 IU mL−1, which was 15% higher than its control.
[Abstract](95) [FullText HTML](69) [PDF 1203KB](1)
Abstract:
During the reaction crystallization of picromerite for potassium sulphate, a large amount of potassium-containing mother liquor is produced. In order to improve the utilization of potassium resources, different crystallization strateqiess performed under different vacuum degrees were used to investigate the recovery and utilization of potassium resources in reaction mother liquor at temperatures of 108, 75 and 35 ℃. The purity, morphology and particle size distribution of the three routes of evaporation crystallization were systematically studied using XRD, chemical analysis, particle size distribution and other analytical methods. The ending point of evaporation water for potassium resource recovery under metastable conditions was determined. The experimental results show that the products of the evaporation crystallization process at 108 ℃ are langbenite and potassium chloride, and the crystal products at 75 ℃ and 35 ℃ are potassium chloride. At 35 ℃, the potassium content and potassium recovery rate of the products reach the highest within the same time, which are 44.64% and 78.73%, respectively. Meanwhile, combined with the characteristics of drought and little rain in the western salt lake area, it is determined that the evaporation crystallization at room temperature is the best process for potassium resource recovery in the mother liquor of reaction of picromerite. The experimental results provide relevant basis and reference for the further improvement of utilization of potassium resource in the resource-type potassium sulfate production process.
[Abstract](7068) [FullText HTML](1490) [PDF 1144KB](3)
Abstract:
A chain extender, styrene-maleic anhydride copolymer SMA-700, was mixed with recycled polyamide 6/carbon fiber composites (r-PA6/CF10) with a twin-screw extruder. The rheological properties, mechanical properties, morphology, crystalline structure, non-isothermal crystallization and subsequent melting behaviors of the resulting r-PA6/CF10 composites were investigated. The results show that SMA-700 has a remarkable chain extension effect on r-PA6/CF10 composites, and can significantly improve the processing performance of r-PA6/CF10. With increased mass fraction of SMA-700, the melt mass flow rate of r-PA6/CF10 decreases gradually. Meanwhile, the apparent viscosity and melt pseudo-plasticity of r-PA6/CF10 will increase with an increased mass fraction of SMA-700. Mechanical tests show that incorporation of chain extender can simultaneously improve the tensile strength and flexural strength of r-PA6/CF10 composites. A SMA-700 mass fraction of 1% and 2% maximizes the tensile strengty (125.4 MPa) and flexural strength (182.3 MPa) of the r-PA6/CF10 composites, respectively. The impact strength decreases with increased SMA-700 content. Scanning electron microscopy (SEM) used suggests that there is no phase separation between SMA-700 and PA6 matrix, implying a good compatibility between SMA-700 and PA6. Non-isothermal crystallization and subsequent melting behaviors characterized by differential scanning calorimetry (DSC) show that when the mass fraction of SMA-700 is 1%, the nucleation effect of SMA-700 may increase the crystallization rate and crystallinity of the PA6 matrix. However, with an excessive amount of SMA-700, both the crystallization rate and crystallinity of PA6 drop, and the perfection degree of α crystal form of PA6 decreases simultaneously.
[Abstract](8033) [FullText HTML](2745) [PDF 905KB](34)
Abstract:
Inspired by the adhesion between mussels and rocks, a series of hydrogels composed of poly[3-(methacrylamido)propyl] trimethylammonium chloride polyacrylamide dopamine (PMPTCDMA) and poly vinyl benzenesulfonic acid sodium salt hydrate (PNaSS) based on charge interaction were prepared. Without introducing covalent bond or coordination bond, opposite charge interaction were adopted in this PNaSS/PMPTCDMA hydrogels system. The cationic polyelectrolyte, PMPTCDMA, simulating the proteins secreted by mussels, which similarly contained abundant positive charges and catechol residues. In addition, the anionic polyelectrolyte, PNaSS, which imitated the rocks with negative charged surfaces. The mechanical performance of the obtained PNaSS/PMPTCDMA hydrogels could be tuned with the content of catechol and water. The PNaSS/PMPTCDMA hydrogels exhibited high stretch performance and robust adhesion property. Before being soaked with saline, the hydrogels were transparent elastomer, however, after soaked, the hydrogels exhibited high tensile fracture stress, which could reach a maximum of 1.89 MPa. Besides, the hydrogels provided robust adhesion on glass slides with a shear strength which was up to 1.58 MPa, after being soaked with saline, the value could increase to 6.17 MPa, which was increased by 3 times, revealing a comparable performance to commercial adhesives. The mussel-inspired polyelectrolyte hydrogels were promising for the adhesion of devices underwater, or under humid environments.
[Abstract](1294) [FullText HTML](207) [PDF 1218KB](3)
Abstract:
Chronic cerebral hypoperfusion (CCH) is one of the most important causes in the initiation and progression of vascular dementia. Tanshinone IIA (TSA) is an active compound isolated from the plant roots of Salvia Miltiorrhiza, which is a traditional Chinese medicine with the activities of improving blood circulation and reducing vessel stasis. In this study, the potential neuroprotective effects and mechanisms of TSA were studied using a bilateral common carotid artery occlusion (BCCAO) model in vivo and H2O2 induced oxidative damage of primary astrocytes in vitro. The results showed, first of all, TSA obviously reversed BCCAO induced cognitive impairment in rats evaluated by Morris water maze (MWM). Nissl staining showed the neuronal loss in CA1 and CA3 region were reversed by TSA. TSA also increased the expression of brain-derived neurotrophic factor (BDNF) levels in cortex and hippocampus. In H2O2-induced primary astrocytes injury, TSA suppressed the decrease of cell viability and inhibited lactate dehydrogenase (LDH) release. Secondly, TSA attenuated mitochondrial membrane potential (MMP) loss and increased ATP level. Furthermore, TSA significantly reversed the damage induced by the disorders of the mitochondria respiratory complex enzyme, and then attenuated reactive oxygen species (ROS) accumulation and lipid peroxidation, simultaneously enhanced antioxidant capacity. The results demonstrated that TSA can enhance mitochondrial bioenergetics and ameliorate oxidative stress effectively, which might contribute to the improving effect of TSA on cerebral ischemia, hypoperfusion and oxidative injuries. Our study provided new evidence to illustrate the mechanisms of protective effects of TSA on cerebral ischemia induced cognitive impairment.
[Abstract](1406) [FullText HTML](242) [PDF 750KB](2)
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Based on the design information of a cracking gas compressor in some ethylene unit, the compressor performance prediction model is established by modifying the design data. An improved BP algorithm (LR-GA-BP) is proposed for compressor performance prediction. The simulation calculation of a four-stage compressor system in the ethylene unit is carried out, and the relative errors between the calculation values and actual values of main components in cracking gas from the fourth-stage outlet of the compressor are less than 2%, and the relative errors between the calculation values and actual values of the outlet temperature and pressure of the compressor are less than 1%. It indicates the reliability of the model. The effect factors of the higher outlet temperature at the fourth-stage of the compressor were analyzed and the corresponding cooling measures were put forward, which is of good guiding significance to slow down the coking of compression system and further optimize its operation.
[Abstract](990) [FullText HTML](268) [PDF 1210KB](5)
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Based on the principle of two-color method, the mixed oil slurry of fluid catalytic cracing slurry and diesel fuel is used as fuel, where fluid catalytic cracing slurry mass concentration is 0, 10%, 30%. The non-premixed flame temperature field (T) and soot concentration field (KL) of different oil slurry at oxygen-carbon ratio of 0.8, 0.9, 1.0, 1.1, 1.2 are constructed. From the hypothesis based on the fact that the nozzle flame section is circular, the percentage of soot volume per unit of flame volume(fv) is obtained. Studies have shown that the flame is divided into flame core(oxygen-rich combustion zone), inner flame (oxygen-poor combustion zone), outer flame. The flame core and outer flames have a higher temperature and the inner flame temperature is lower. The soot is more in the inner and outer flames and is the most in the inner flame.In the transition from the flame core to the inner flame, the temperature drops and the soot concentration rises. In the transition zone from the inner flame to the outer flame, the oxygen concentration increases, the temperature rises, and the soot concentration decreases. The more the catalytic slurry content in the slurry, the more soot is produced when the slurry is at the same oxygen to carbon ratio. When the oxygen-carbon ratio of the slurry is increased, the flame temperature rises and the soot concentration decreases.
[Abstract](1483) [FullText HTML](328) [PDF 737KB](2)
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By using the hyphenated instrument of solid phase extraction (SPE) and solid phase spectroscopy developed by our group, a rapid, sensitive and selective method for detecting Hg2+ in river was proposed. A orange Hg-Dithizone compound was produced with dithizone and the analyte Hg2+ in solution, and then was enriched on the mixed cellulose membrane, the extra dithizone was removed by washing the membrane with sodium hydroxide solution, after that a visible diffuse reflectance spectrum was measured on the membrane directly for the quantitative analysis of mercury. In this work, the serious interference problems were resolved by using base washing to remove dithizone and by adding EDTA to mask Cu2+ and Cd2+. Under the optimal conditions, the liner range of the method was 0.5-30 μg/L with a squared correlation coefficient of 0.993, and the limit of detection was 0.444 μg/L. The method was applied to the detection of Hg2+ in river samples. The recoveries were from 99% to 101%, and the relative standard deviations of parallel tests were between 4.5% and 10.5%. This work provided a fast method for the determination of Hg2+ in river samples with high sensitivity and selectivity, as well as acceptable accuracy and precision.
[Abstract](1349) [FullText HTML](282) [PDF 1149KB](3)
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The intensive removal of heat with limited area is a crucial to many industrial processes such as glass tempering, metal annealing and electronic components cooling. The intensive impingement cooling with blade-type multiply circular gas jets is developed on the purpose. The experimental investigation is preformed to study the effects of impingement height H and jet Reynolds numbers on the heat transfer when multiply intensive circular air jets normally impinge on a smooth and flat surface. The average convective heat transfer coefficients are measured with heated thin foil technique which involves the detection of surface temperature and apples const heat flux heating. The jet Reynolds numbers based on nozzle exit condition, ReD, vary from 5000 to 48500 and normalized impingement height H/D is in range of 6.25 to 12.5. The experimental result show that an increase in jet Reynolds numbers will produce higher average Nusselt numbers and normalized impingement height with an exponent of -0.606 also have a strong impact on it. All experimental data have been correlated as functions of jet Reynolds number, Prandtl number and normalized impingement height and a new heat transfer dimensionless correlations of blade-type multiply circular jet array is established. The experiment findings are compared with Martin’s correlation and about 40% higher is observed. It is indicated that intensive circular nozzle array can significantly enhance heat transfer rate due to its high open porosity. The experimental data are quite well fitted by the Gardon's equation. Conversely the correlation proposed by Martin is not suitable to reduce present data and a modified geometrical function is developed.
[Abstract](811) [FullText HTML](356) [PDF 828KB](8)
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[Abstract](1289) [FullText HTML](355) [PDF 1169KB](1)
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Arm-type tensioner is widely used in the automotive engine belt system, whose spindle often break during actual working process caused by fatigue. For this reason, it is necessary to study the mechanics properties of the tensioner and try to find a method for calculating the spindle’s fatigue life. In this paper, the arm-type tensioner in automotive engine is taken as the research object, the mechanics analysis is carried out for the tensioner in working process, the mechanics model is established for calculating the forces acted on the tensioner’s spindle, and the method for calculating the bending stress of the tensioner’s spindle is established. On such basis, and by use of the fatigue theory and rain-flow counting method, a method is established to calculate the fatigue life of the tensioner’s spindle. With a specific example, the fatigue life of the tensioner’s spindle is calculated numerically and verified by comparing with the actual life of spindle. Several parameters’ influences on the mechanics performance and fatigue life of the tensioner’s spindle are studied. It is found that, the main factors affecting the fatigue life of the tensioner’s spindle are the distance between the pulley and the rotating arm (l1) and the bushing length (l2), and decreasing l1 and l2 can effectively increase the fatigue life of the spindle, while the length of the arm L and the vortex spring torsion stiffness T’ have no significant effects on the fatigue life of the tensioner’s spindle.
[Abstract](1095) [FullText HTML](380) [PDF 1498KB](11)
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In this paper, lean coal, fat coal and gas coal were taken as the research objects to deeply study the macroscopic gas release law and microstructural changes of coking coal during low temperature oxidation. The gas release laws were obtained by heating and isothermal oxidation and the structure of coals was characterized by N2 adsorption, scanning electron microscopy equipped with energy dispersive X-ray analysis (SEM-EDS) and infrared spectroscopy (FTIR). The results of constant temperature experiment showed that a small amount of the CO generated at a certain temperature came from the thermal decomposition of coal itself, and most of it came from the decomposition of carbon-oxygen complexes produced by oxidation reaction. N2 adsorption and SEM characterization results indicated that at 95 ℃, the destructive effect on coal structure was small, but at 190 ℃, the cracks on coal surface increased and the degree of pulverization became larger. The total volume and average pore diameter increased, but BET surface area decreased due to the blockage of some oxidation products. Al and Si elements were detected on the surface of coal, so it could be inferred that the attached particles contained Al2O3 and SiO2. FTIR characterization result showed that during the low temperature oxidation process, -OH, -CH3 and -CH2- reacted with oxygen and formed unstable carbon-oxygen complexes like C=O, -COOH and ether bonds, which were further decomposed into CO, CO2 and other gases. The thermodynamic feasibility of the proposed gas generation mechanism was verified by HSC Chemistry 6.0. Besides, the higher the volatile content of coal contained, the smaller the proportion of aromatic structure was, the more developed the pore structure was, resulting in the more easily oxidation and spontaneous combustion occurred.
[Abstract](1478) [FullText HTML](439) [PDF 1352KB](16)
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Reasonably describing gas-liquid interaction force and bubble size distribution is the key to accurately simulate the hydrodynamic parameters of the bubble column. For the gas-liquid system, a new bubble breakup model was implemented into the population balance model (PBM) and coupled with the Euler two-fluid model. The gas-liquid two-phase flow in a bubble column with an inner diameter of 0.44 m and a height of 2.43 m was simulated. Firstly, the predicted values of bubble breakup rate and daughter bubble size distribution of the breakup model were verified. Then, the gas holdup and liquid axial velocity predicted by coupled model at different superficial gas velocities were compared with the experimental values. Moreover, the effect of lift to model (prediction result)was investigated. The results show that, both gas holdup and liquid axial velocity is improved in radial distribution when the lift force is included. The simulation value of the CFD-PBM coupled model have a good agreement with the experimental data in low and high superficial velocity. Both the turbulent dissipation rate in the reactor and the interaction between the bubbles rise with an increase in superficial gas velocity, which makes the distribution range of bubble size is widened.
[Abstract](1489) [FullText HTML](348) [PDF 818KB](8)
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The dividing wall column has the advantage of saving energy and capital cost compared to a conventional rectifying column. At the same time, the dividing wall column has more degrees of freedom than the conventional rectifying column, and its design, control and optimization are more difficult. In this paper, the shortcomings of the simple calculation method for the four-tower equivalent model of the existing dividing wall column, an improved calculation method is proposed. The minimum operating conditions of the dividing wall column are determined according to the Underwood equation, and the operating parameters such as the number of stages, the feeding stage, side-stream stage, the reflux ratio, and the gas-liquid distribution ratio of the dividing wall column can be quickly determined in combination with the design requirements. In order to verify the effectiveness of the design method, three different ESI feed streams were selected for design and the obtained design results were strictly simulated in HYSYS. The results show that the method can be more accurate than other design methods in calculating the composition of the connecting stream between the pre-fractionator and the main column, and the total annual cost is less than other short cut design methods.
[Abstract](1547) [FullText HTML](558) [PDF 882KB](26)
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Hypervolume-based evolutionary algorithms can effectively solve the multi-objective optimization problems and obtain promising solution sets with fast convergence and uniform distribution, but the performances usually fade because of high computational complexity and low programming efficiency. Aiming at solving the two-dimensional and three-dimensional multi-objective optimization problems, hypervolume-based multi-objective evolutionary algorithm(MOEA-HV) is proposed for accurately calculating the individuals’ exclusive hypervolume contributions to guide the evolution of the whole population. The proposed algorithm employs non-dominated sorting among all individuals before the indicator-based evolutionary algorithm(IBEA) to delete dominated individuals, reduce the amount of calculation of the individuals’ exclusive hypervolume contributions and improve operational efficiency. Meanwhile the other strategies in NSGA-Ⅲ are utilized to optimize the distribution of the algorithm. The experimental results demonstrate that MOEA-HV has higher efficiency while maintaining the trade-off between fast convergence and uniform distribution.
[Abstract](1531) [FullText HTML](355) [PDF 803KB](10)
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Generally, flow shop scheduling problem assumes that all processing is performed in one factory which is called single factory production mode. Nowadays, with the advantages of low cost, low risk and high quality, distributed manufacturing has become a mainstream in the industrial production. Therefore, it is necessary to study the distributed scheduling problem. Distributed assembly permutation flow shop scheduling problem plays an important role in modern supply chains and manufacturing systems. In this paper, a modified biogeography-based optimization algorithm is proposed to solve distributed assembly permutation flow shop scheduling problem with the goal of minimizing makespan. In the initialization phase, the MBBO uses the SPT and the NR2 rule to optimize the feasible solutions. Then, in the mutation phase, the job insertion heuristic method based on the factory completion time is used to adjust the factory assignment and processing order of the jobs. Finally, the simulated annealing algorithm is combined to jump out of the local optimal solutions, which enhances the global search ability of the algorithm. Simulation experiments based on 900 small instances and 540 large instances and comparison with the existing 12 heuristic algorithms and the basic biogeography-based optimization algorithm verify the superiority of the MBBO. Besides, the new best known solutions for 70 instances are found.
[Abstract](1605) [FullText HTML](605) [PDF 912KB](9)
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Aiming at the problems of too many channels in motor imagery (MI)-based brain-computer interface (BCI) systems, a channel selection algorithm based on multi-correlation forward searching (MCFS) algorithm is proposed to optimize the channel set to improve the performance of BCI systems. First, a forward searching algorithm is performed on the channel set based on the training set. At the same time, the trust values of three correlation algorithms are updated with the classification accuracy of the validating set. Then according to the trust values of three correlation algorithms, select the high-quality channel set to obtain motor imagery related features with common spatial pattern (CSP) algorithm and train the classification model through support vector machine (SVM) with a linear kernel. The proposed algorithm is implemented on two datasets (BCI Competition IV dataset I and BCI Competition III datasets IVa) with average classification accuracy 81% and 87%, respectively. Moreover, compared with three other common channel selection algorithms, the MCFS algorithm achieves the highest average classification accuracy. The results suggest that the proposed MCFS algorithm shows superior performance and provides a technical reference for the application of MI-based BCI system.
[Abstract](1876) [FullText HTML](551) [PDF 785KB](11)
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Aiming at the situation that the variable neighborhood search algorithm can hardly find a better feasible solution in some neighborhoods for a long time in later stage, this paper proposed an adaptive variable neighborhood search algorithm based on neighborhood selection probability. The algorithm can adjust the neighborhood selection probability adaptively base on corresponding neighborhood’s optimization circumstance, thereby improving the optimization efficiency of the algorithm. This paper designed two select probability update methods and discussed the characteristics of the two selection probability update methods, we set the minimum selection probability to avoid selection probability reduced to zero and ensure the diversity of the neighborhood. Due to battery capacity limitations and charging requirements, the optimization to the electric vehicle route problem is more complicated than the traditional vehicle route problem. The large-scale electric vehicle routing problem under the actual urban distribution logistics was modeled and analyzed, and an efficient initial solution generation algorithm was designed according to the geographic location and time window of the service customer. The segmentation-exchange based on spatial proximity, 2-opt, relocation and other neighborhood operators for adaptive variable neighborhood search. Finally, the algorithm is validated by simulation with different scales data. The result shows that the variation curves of the two select probability update methods have the same tendency which proved the rationality of minimum selection probability vector setting. Compared to the traditional variable neighborhood search algorithm, the adaptive variable neighborhood search algorithm proposed in this paper can better jump out of the local optimal solution and reduce the logistics cost under urban distribution more effectively.
[Abstract](1533) [FullText HTML](460) [PDF 820KB](17)
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Glutathione (GSH), one of the thiol short peptide in organisms, is widely used in medicine, food additive, health care and cosmetic industries. In this study, a two-enzyme cascade consisting of bifunctional glutathione synthetase (GshF) and polyphosphate kinase (PPK) was constructed for ATP-regenerating synthesis of GSH. As the catalytic substrate of PPK, polyphosphate (polyP) was used to provide energy in the reaction. The efficient soluble expressions of GshF and PPK were obtained when induced at the low temperature of 18 ℃. After purification, the two enzymes were coupled together to synthesize GSH in one pot. It was found that high concentration of MgCl2 inhibited the production of GSH due to the chelation with polyP. The optimal concentration ratio of polyP to MgCl2 was 30∶45 (mmol/L∶mmol/L). At 0.5 mmol/L ADP, the reaction achieved the highest efficiency for GSH synthesis. The optimal temperature for the two-enzyme reaction was 45 ℃, achieving a high yield of 78% based on added L-cysteine. The optimal temperature for GSH synthesis was relatively high, because the activities of GshF and PPK could increase with the increased temperature. The enzyme ratio in the system was further investigated. The production of GSH was improved at higher concentration of PPK, indicating the ATP-regenerating reaction was a limiting step in the reaction. At the optimal ratio of 4 g/L PPK and 1 g/L GshF, the titer of GSH reached 58 ± 3.3 mmol/L with a productivity of 19.3 ± 1.1 mmol/L/h at 3 h, which achieved the reported highest production of GSH. Using the low-cost substrate of polyP to supply energy, the efficient cascade reaction provided a potential application for large-scale enzymatic production of GSH.
[Abstract](5151) [FullText HTML](666) [PDF 617KB](6)
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In parallel system, the arrangement graphs An,k has good properties such as symmetry, small diameter, and high fault tolerance. Subsystem reliability is defined as the probability that there is still a normal operating subsystem when the system has faults. It is usually used to measure the system health status, and the calculation of subsystem reliability is an NP-hard problem. This paper discusses the robustness of the reliability of the subgraphs and the approximate algorithm of reliability. Further, the Monte Carlo algorithm for arrangement graphs is constructed. The simulation results show that the constructed Monte Carlo algorithm is much better than the known approximation algorithm. In particular, the error of Monte Carlo approximation of A3,2 subgraph reliability is less than 1%.
[Abstract](6453) [FullText HTML](1338) [PDF 1448KB](5)
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In this paper, halogen-free surface active ionic liquid (SAIL), 1-butyl-3-methylimidazolium alkyl sulfate ([C4mim][C12SO4]), was synthesized through ion exchange reaction. The photo responsive system of Gemini12-3-12/[C4mim][C12SO4]/trans-OMCA/H2O was constructed by mixing [C4mim][C12SO4] and Gemini surfactant 12-3-12·2Br- (Gemini12-3-12) together and introduce photosensitive molecules trans-o-methoxy cinnamate (trans-OMCA) at the same time. The photo-responsive behaviors of aqueous two-phase system (ATPS), specific single-phase system and anisotropic phase system in Gemini12-3-12/[C4mim][C12SO4]/trans-OMCA/H2O mixed system have been studied by TEM, UV-vis and dynamic light scattering (DLS). The results have shown that the mixed system displays good photo responsiveness. For the aqueous two-phase system in which spherical micelle and wormlike micelle coexist, UV irradiation for a certain period of time will promote the fusion of spherical micelle phase and wormlike micelle phase into a single wormlike micelle phase. For the single-phase vesicle system, it will be separated into a two-phase system of spherical micelle and wormlike micelle after UV irradiation for a certain period of time, and the system will gradually merge into a single wormlike micelle phase after prolonging the UV irradiation time. The anisotropic system will turn into isotropic one after a certain time of UV irradiation. It is obvious that the macro phase behaviors of the system can be tuned by UV irradiation and the system realizes the photo induced phase separation and photo induced phase combination.
[Abstract](5816) [FullText HTML](1531) [PDF 840KB](2)
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Partial transfer sequence (PTS) is one of the effective methods for filter bank multicarrier (FBMC) to reduce peak-to-average power ratio (PAPR). However, PTS method selects the optimal phase factor by exhaustive search, there is a high computational complexity. In order to overcome this shortcoming, this paper presents a new method based on PTS method. First, This method proposes an odd-partial transfer sequence(OPTS) segmentation method based on the traditional PTS segmentation method, this method uses staggered segmentation method for odd subblocks and random segmentation method for even subblocks, the method combines the advantages of staggered segmentation and random segmentation, not only improves the PAPR performance of the system, but also reduces the computational complexity. Second, this paper proposes a scaled particle swarm optimization (SPSO) algorithm, which introduces the scaling factor into the traditional PSO algorithm. The existing particle swarm optimization (PSO) algorithm has a slow convergence rate in the iteration process, and is prone to fall into local optimal in high-dimensional space, which also has the problem of particle optimization. The main goal of the proposed PSO algorithm is to use the scaling factor to control the particle speed, and to obtain good PAPR performance with lower computational complexity and faster convergence speed. The addition of SPSO algorithm on the basis of OPTS will slightly increase PAPR value, but have better performance in terms of complexity and significantly improve the spectrum utilization. Simulation results show the effectiveness of the new method.
[Abstract](7888) [FullText HTML](1819) [PDF 772KB](11)
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Volatile organic compounds (VOCs), which include benzene, toluene and xylene, are harmful to both human health and the environment. It is important to control and reduce the release of VOCs. Transition-metal oxides have been widely studied due to their low cost and relative high activity for catalyzing VOCs. In this work, manganese oxide was used to coat zeolite molecular sieve, producing the composite by a one-step redox reaction between potassium permanganate and manganese nitrate. By introducing a template agent, the reaction temperature and concentration are optimized to modulate the structure and properties of manganese oxide, producing a layered porous structure that sets free the pore of the zeolite molecular sieve thoroughly. The large special surface area of zeolite molecular sieve facilitates the adsorption of VOCs and the manganese oxide coating promotes the catalytic oxidation of VOCs. Our results show that the use of different reaction temperature and catalyst concentration leads to a change of the morphology of manganese oxide the specific surface area of the composite, the ratio of lattice oxygen to adsorbed oxygen. And the Mn3+/Mn4+ ratio in manganese oxide catalyst. The special surface area of the composite, coating amount, the ratio of lattice oxygen to adsorbed oxygen and Mn3+/Mn4+ together impact the catalytic performance of the composite. An appropriate amount of manganese oxide coated molecular sieve catalyst prepared under ice bath shows the best catalytic performance for toluene (200 ppm); the toluene conversion reaches 90% at 256 °C.
[Abstract](5977) [FullText HTML](1572) [PDF 1340KB](9)
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In order to explore the relationship between drug grafting ratio of polymeric prodrug and its drug loading efficiency, a model of polymeric prodrug: methoxy poly(ethylene glycol)-b-poly(ε-caprolactone-co-piperilactone-g-5-aminolevulinic acid) (mPEG-b-P(CL-co-APIL)) was designed. This polymeric prodrug was used as drug carrier of 5-Aminolevulinic acid (5-ALA), it would load drug both by method of chemical bonding and physical embedding. Molecular dynamics (MD) was utilized to calculate the compatibility of polymeric prodrug with 5-Aminolevulinic acid and H2O, and to predict the relationship between drug grafting ratio and drug loading. During the process of calculation, the Flory-Huggins interactional parameter was decomposed into van der Waals force components and electrostatic force components, so that the effect of 5-ALA grafting ratio on the polymeric prodrug carrier was analyzed. The dissipative particle dynamics simulation (DPD) was used to explore and observe the morphology of the drug-loaded micelles and observe the concentration state of the drug molecules. Computational simulation results showed that the compatibility between polymeric prodrug and 5-ALA was getting better with the drug grafting increased, so it can predict that the drug loading efficiency of polymeric drug would get better as the drug grafting ratio increases. And the DPD simulation showed that the polymeric prodrug would self-assemble into spherical micelles in H2O.The density distribution of drug molecules showed that the distribution in core of micelle was higher since the drug grafting ratio was higher. All the simulation results indicated that it’s feasible to improve drug loading efficiency by grafting drug molecule. The content of this research can provide some guide for the design and development of drug carriers.
[Abstract](6724) [FullText HTML](2010) [PDF 852KB](3)
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In this paper, a distributed coordination solution control strategy of partitioned micro-grid based multi-agent technology is proposed. The optimal power flow model is constructed by combining the power flow calculation and economic scheduling problems. The complex power system network is partitioned to achieve the balance among regions. The regional control error (ACE) is used to compensate the deviation of the frequency between the areas. Further, the optimal micro-grid power flow problem is solved by optimizing the hierarchical scheduling with two-level agents, i.e. Bus Agent and Regional Agent. Finally, the optimal micro-grid power flow distribution is derived and the safety, stability and economy optimal operation of micro-grid are achieved. It is shown that the multi-agent technology can complete the analysis on optimal power flow of the micro-grid and the distributed method can protect the internal information security of each regional power grid and solve the problem of excessive communication in the centralized optimization.
[Abstract](8830) [FullText HTML](2070) [PDF 1289KB](4)
Abstract:
Turbulent mixing enhancement of twisted tape for cracking process was studied. Meso- and micro-scale mixing performance was analyzed to reveal the close relationship between turbulent mixing and cracking reaction. Research method of computational fluid dynamics was used to conduct contrast simulations between bare coil and coil with twisted tape to present variations of transfer and cracking reaction characteristics. The simulation results show that by paying 5.31% more pressure drop than bare coil, turbulent kinetic energy at the ratio of axial distance to total length Z/L=0.228 in the downstream of twisted tape is increased by 39.6% while the overall averaged characteristic micro-mixing time is reduced to 1.72% of bare coil, indicating an effective meso- and micro-mixing enhancement. The intensified turbulent mixing promotes the uniformity of field profiles to improve synergy among temperature, species concentration and velocity distributions, resulting in enhanced heat and mass transfer performance. The Nu and Sh of cracking coil installed twisted tape are increased by 7.50% and 2.34% respectively compared with bare coil. While the overall olefin yield is improved by 5.88% and the averaged coil skin temperature is reduced by 24.01 K. The coking suppression effect can be attributed to the strong swirling flow induced by twisted tape, generating radial velocity component to accelerate fluid in the wall vicinity. Consequently, the residence time of fluid in the near wall region at the ratio of radial distance to cracking coil radius r/R=0.993 can be reduced by 53.01%. Furthermore, the enhanced turbulent mixing results in more homogenous radial field profiles, enlarging the molecular scale uniform mixed region by 5.29% to extend reactive zone, which is beneficial for olefin yield improvement.
[Abstract](6455) [FullText HTML](2084) [PDF 827KB](18)
Abstract:
The non-contact deception detection technology is of great significance in areas such as judicial. In order to improve the accuracy of deception detection model, this paper proposes a deception detection model based on multimodal fusion. With the support of this model, we only need to process the video and audio signals of the speaker to effectively complete the deception detection evaluation task. The heart rate reflects the emotional changes of the liar. We extract the feature of heart rate by the Photo-plethysmography method and the fully connected network. The video and text features are extracted through 3D-convolutional neural networks and Word2Vec+CNN, then these features are merged. The linear support vector machines are used to classify the fused features. The simulation experiment was carried out on the open source Real-life Trial dataset. Compared with the latest MLPH+C multi-modal model, the accuracy of the deception detection model proposed in this paper increased by 2.74%-23% in the three-mode. In order to evaluate whether the combination of different modal features can improve the performance of the deception detection model, we use the combination of features of each modality to conduct experiments. The accuracy of each category combination is over 70%.And the combination of text and heart rate features is 96.89%, especially the combination of text, video and heart rate reaches the highest accuracy of 98.88%,and the AUC values reached 0.9883.The accuracy of the three-mode prediction is better than the single-mode and dual-mode. The experimental results show that the multi-modal model proposed in this paper can effectively improve the correct rate of deception detection.
[Abstract](9195) [FullText HTML](3485) [PDF 1107KB](12)
Abstract:
Cobalt selenide is considered to be an ideal anode material for lithium-ion batteries because of its good lithium-ion insertion/extraction capability. However, the battery performance of cobalt selenide is limited by the large volumetric expansion upon cycling and its insulating nature. In this study, we produced CoSe2-C/C-PAN by coating CoSe2-C polyhedrons with polyacrylonitrile (PAN) in N2 atmosphere. The CoSe2-C polyhedrons were successfully synthesized using Co-based zeolitic imidazolate framework (ZIF-67) as precursor through a two-step method, which includes carbonization of ZIF-67 and a subsequent selenization. The resultant CoSe2-C/C-PAN showed high specific capacity and excellent cycling stability with an initial discharge capacity of 1 440 mA·h/g at 0.2 A/g and a reversible capacity of 653 mA·h/g at 1.0 A/g after 200 cycles as anode material of Li-ion battery. The excellent battery performance of CoSe2-C/C-PAN could be attributed to the synergistic effect of nanostructured CoSe2 and carbon materials, in which the nanostructured CoSe2 possesses high reactivity towards lithium-ions and the carbon can provide a continuous conductive matrix to facilitate the charge transfer and an effective buffering to mitigate the structural variation of CoSe2 during cycling. The significantly enhanced electrochemical performance of the composite could be ascribed to the improved electrical conductivity and structural stability of C-PAN.
[Abstract](7250) [FullText HTML](2752) [PDF 892KB](5)
Abstract:
In this study, the salt-tolerant bacteria were used to degrade the organic matter and ammonia nitrogen in the shale field produced water. The degradation performance and membrane fouling characteristics of the anoxic reactor-membrane bioreactor (AR-MBR) and the separate MBR reactor were investigated. The difference between two reactors was that the AR-MBR system was provided with a filament filler to form an anoxic circumstance in front of the MBR reactor. The results showed that the degradation of the AR-MBR combined reaction system was better than that of the MBR reactor alone. The removal rates of TOC were 88% in AR-MBR and 80% in MBR, the removal rates of ammonia nitrogen were 90% and 75%, respectively.The transmembrane pressure(TMP) and the total membrane fouling rate of the AR-MBR was slower than that of the MBR reactor. The main reason was that the particle size of the floc in the AR-MBR reactor was larger than that in the MBR reactor, which was not easy to block the membrane pores. On the other hand, the soluble microbial products(SMP) and extracellular polymeric substances (EPS) content was lower in AR-MBR reactor than that of the MBR reactor, while the protein to polysaccharide concentration ratio (PN/PS) was higher, the reduction of fouling substance on membrane alleviated the membrane fouling phenomenon.
[Abstract](7015) [FullText HTML](1970) [PDF 1041KB](6)
Abstract:
In this study, a bacterial strain named 206BP, with efficient degradation for the organic matters in shale gas produced water, was isolated from high-salt wastewater and surrounding soil samples. Morphological observation, gram stain and 16SrDNA gene sequence analysis were used to identify the strain 206BP and the results showed that it belonged to the Bacillus genus as it had 99% similarity with Bacillus purgationiresistens and other orthologs. The diameters of the strain and spore were about 2.0 μm and 0.3-0.6 μm, respectively. Besides, it was confirmed the strain was Gram-positive, capable of producing urease for urealysisand hydrogen sulfide gas as well as hydrolyzing starch and reducing nitrate and nitrite. The growth of the strain 206BP was observed that it stayed at the lag phase in the first 5 h and enter the exponential growth phase in the period of 5-22 h, finally reaching the stationary phase after 24 h. Meanwhile, the effects of NaCl concentration, carbon source, nitrogen source and pH on growth characteristics were also investigated. The experimental results reflected the strain 206BP could grow well and was moderately salt-tolerant with 0-8w% NaCl. In addition, its optimum growth pH was in the range of 5-8 and the optimum carbon and nitrogen sources were glucose and urea, respetively. The bacterial concentration in the stationary phase of the growth curve could increase with more glucose while the stagnation period of the growth curve was prolonged as the glucose concentration exceeded 5000 mg·L−1. The added urea had a positive correlation with the strain 206BP growth but the promotion faded away with the urea concentration up to 50 mg·L−1.
[Abstract](9979) [FullText HTML](2651) [PDF 949KB](10)
Abstract:
TPA-functionalized prepolymer (iPrTPA-PrePBO, tBuTPA-PrePBO) was synthesized by treating 4,4'-dicarbonylchloride-4''-isopropyltriphenylamine (iPrTPADC) and 4,4'-dicarbonyl chloride-4''-tertbutyltriphenylamine (tBuTPADC) with 4,6-di(tert-butyldimethylsilylamino)-1,3-di(tertbutyldimethylsiloxy)benzene (TBS-DAR), respectively. Then, a thermal cyclization reaction was carried out to obtain two benzoxazole polymers containing electron-donating triphenylamine groups (iPrTPA-PBO, tBuTPA-PBO). The prepolymers and benzoxazole polymers were characterized by nuclear magnetic resonance spectroscopy(1H-NMR) and Fourier transforminfrared spectroscopy (FT-IR). We also used thermogravimetry (TG), X-ray diffraction (XRD), Ultraviolet-visible spectroscopy (UV-Vis) and Fluorescence spectroscopy to analyze the solubility, thermal and photophysical properties of the polymers. The results showed that the two prepolymers had excellent solubility in conventional solvents, and the polymer after thermal cyclization reaction also had moderate solubility in solvents with a high boiling point such as DMSO. The polymers existed in nitrogen atmosphere and air showed excellent thermal stability with a temperature above 500 ℃. Photophysical studies showed that polymers had higher fluorescence quantum yields than the conventional PBO with a similar band gap (~2.0 eV).
[Abstract](7979) [FullText HTML](2041) [PDF 1323KB](16)
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[Abstract](9092) [FullText HTML](2254) [PDF 1066KB](42)
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[Abstract](935) [FullText HTML](246) [PDF 1116KB](8)
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Cobalt selenide is considered to be an ideal anode material for lithium-ion batteries because of its good lithium-ion insertion/extraction capability. However, due to large volumetric expansion upon cycling and insulating nature, the performance of cobalt selenide is limited. In this study, we obtained CoSe2-C/C-PAN by coating CoSe2-C polyhedrons with polyacrylonitrile (PAN) in N2 atmosphere. The CoSe2-C polyhedrons were successfully synthesized using Co-based zeolitic imidazolate framework (ZIF-67) as precursor through a two-step method, including carbonization of ZIF-67 and subsequent selenization. The resultant CoSe2-C/C-PAN presents high specific capacity and excellent cycling stability with an initial discharge capacity of 1 440 mAh/g at 0.2 A/g and a reversible capacity of 653 mAh/g at 1 A/g after 200 cycles as anode material of Li-ion battery. The excellent battery performance of CoSe2-C/C-PAN should be attributed to the synergistic effect of nanostructured CoSe2 and carbon materials, in which the nanostructured CoSe2 possesses high reactivity towards lithium-ions and the carbon can provide a continuous conductive matrix to facilitate the charge transfer and an effective buffering to mitigate the structure variation of CoSe2 during cycling. And such significantly enhanced electrochemical performance should be ascribed to the improved electrical conductivity and structure stability of C-PAN.
[Abstract](7949) [FullText HTML](2101) [PDF 1030KB](16)
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Proteins are widely used as reagents in laboratories and as therapeutics for many different diseases. However, the native proteins are often aggregated and denatured under extreme conditions such as freezing, drying and dehydration, reducing bioavailability and therefore increasing the dose that is required. To protect the proteins under extreme conditions, we prepared two types of amino acid polymers, poly-(L-lysine) (PLL) and poly-L-glutamate (PLG) from the rapid ring-opening polymerization (ROP) of α-amino acid N-carboxyanhydride (NCA) using lithium hexamethyldisilazide (LiHMDS) as the initiator. β-galactosidase (β-Gal) was used as model protein to examine the protein protecting effect of synthesized amino acid polymers during lyophilization. The results indicated that PLL and PLG blending had significant protection effect on β-Gal during lyophilization and improved activity of the resulting protein from 38%, without using protecting agent during lyophilization, to 77% of the original protein activity. Our studies demonstrated that amino acid polymers could exert potent activity for protein stabilization. The easy operation of LiHMDS-initiated, moisture insensitive and rapid NCA polymerization implies great potential of this strategy to prepare amino acid polymers quickly for screening of protein stabilization and mechanism study.

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2020, 46(2): 155-163.   doi: 10.14135/j.cnki.1006-3080.20190104001
[Abstract](7064) [FullText HTML](2618) [PDF 1323KB](87)
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2020, 46(2): 164-172.   doi: 10.14135/j.cnki.1006-3080.20190223001
[Abstract](1520) [FullText HTML](466) [PDF 1441KB](34)
Abstract:
A three-dimensional randomly packed granular bed with a height of 20 mm and a granular diameter of 1.0 mm was simulated on the basis by coupling of computational fluid dynamics (CFD) and discrete element method (DEM) for liquid-solid phase filtration. Fluid flow and particle deposition characteristics were analyzed, and effects of deposition growth on the filtration efficiency and pressure drop were investigated as well. The results show that with deepening of the filter bed, the initial pressure drop is gradually increased. Compared with the values from Ergun equation, the calculation deviations of the initial pressure drop at different fluid flow rates are within 25%. The initial filtration efficiency for larger particles is higher, and it decreases with the velocity of fluid flow. On the basis of regression analysis, it can be predicted that the deviations between the predicted and the experimental values are within 10%. In addition, the particle deposition fraction in the filter bed decreases with the depth of the filter bed, and particles near the inlet incline to form clusters, and their proportion at the early stage of filtration becomes prominent. When the filtration goes gradually deepening, the numbers of particles that accumulated along the bed become more and more even. The deposition of particles influences the flow of fluid within the filter column, which subsequently affects the filtration efficiency and pressure drop. For the particles in different sizes, the deposition growth on the granular surface leads to an increasing trend of filtration efficiency and pressure drop.
2020, 46(2): 173-178.   doi: 10.14135/j.cnki.1006-3080.20190221004
[Abstract](5906) [FullText HTML](1684) [PDF 943KB](15)
Abstract:
Gas phase combustion synthesis technology is a well-known chemical manufacturing technique for preparing nanomaterials. Nevertheless, the chemical reaction of precursors and the nucleation, growth, sintering and agglomeration of the nanoparticles make the whole combustion reaction zone be complicated. Flame chamber is the core equipment, and its structure affects the flow field parameters, ultimately determining the morphologies, structures and properties of the final products. In this work, three-dimensional geometric models of premixed high-speed jet flame reactors were developed, and the combustion simulations were carried out using k-ε turbulence model, Eddy Dissipation Concept (EDC) and discrete phase model. Additionally, a 19-step detailed reaction mechanism of H2 was used for the temperature profile, velocity field and the particles residence time in high-temperature flame region. The effects of temperature, velocity and the reaction rate of H2 combustion under different outlet diameters of the burner center duct were systematically investigated. The simulation results indicate that increasing the diameter of the outlet of burner center duct leads to significant increase in the length of the high temperature region, and the attenuation of the central jet velocity drops off in the different scales of flame reactors. SiO2 nanoparticles were selected as discrete source in different scales of flame reactor, as well as for the study of residence time and back mixing in high temperature flame region. The results show that the residence time of the nanoparticles in the high temperature flame region is obviously increased, and the back-mixing phenomenon is aggravated. Together with the calculations, these results supply useful references for regulation and control of nucleation growth process of nanoparticles and provide theoretical fundamentals for industrial flame reactor design.
2020, 46(2): 179-188.   doi: 10.14135/j.cnki.1006-3080.20190218002
[Abstract](7219) [FullText HTML](2524) [PDF 1778KB](12)
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The carbon shell was coated on the surface of ferroferric oxide via high temperature carbonization to form the core-shell structure of Fe3O4@C. Compared with the single structured filler particles, the core-shell structure of Fe3O4@C was more uniform and more compatible with the organic matrix. Thus, the Fe3O4@C/PVDF (Polyvinylidene fluoride)flexible film with high dielectric constant and low dielectric loss was obtained. Carbon shell plays a key role in improving the dielectric properties of materials. The carbon shell can not only be used as a transition layer between the Fe3O4 core and the PVDF matrix, but also strengthen the interfacial polarization of the material. The improvement of the dielectric properties of the materials is mainly based on percolation theory and interfacial polarization theory. According to the experiment, the percolation threshold of Fe3O4@C was 12%. During the experiment, it is necessary to accurately control the amount of added filler. At this packing ratio, the film was filled with countless microcapacitors and the dielectric constant of the material was increased rapidly. At the same time, the interfacial polarization of the electric dipole between different interfaces further enhanced the dielectric properties of the material. Compared with pure PVDF, carbon fiber/PVDF and graphene oxide (GO)/PVDF, the Fe3O4@C/PVDF flexible film prepared in this paper has a higher dielectric constant of 115 (normal temperature, 1 kHz) and lower dielectric loss of 0.063. Meanwhile, compared with pure PVDF, its tensile strength was increased from 42.3 MPa to 76.6 MPa, and the elasticity modulus was increased from 1.3 GPa to 2.0 GPa. Thus, the prepared materials can be used as a flexible film with high dielectric in electronic components and other fields.
2020, 46(2): 189-196.   doi: 10.14135/j.cnki.1006-3080.20190225004
[Abstract](999) [FullText HTML](298) [PDF 1080KB](8)
Abstract:
Polybenzoxazine resins have many excellent properties. However, most of the raw materials for the synthesis of benzoxazines are derived from petroleum resources. With the global energy crisis and current environmental problems, polybenzoxazines are facing challenges in terms of supply and cost. Therefore, the search of green raw materials for synthesizing fully-bio-based benzoxazine is a sustainable development and is also of great significance for developing benzoxazine science. In this paper, magnolol was used with furfurylamine and dehydroabietylamine by a simple solvent method to prepare two fully-bio-based benzoxazines: M-fa and M-da, respectively. The structures of the two monomers were confirmed by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance analysis (1H-NMR and 13C-NMR) and ESI-high resolution time-of-flight mass spectrometer (ESI-MS). Differential scanning calorimetry (DSC) were performed to monitor the curing behaviors of M-fa and M-da, and the exothermic peaks were displayed in the spectra of the oxazine ring and the double bond. The thermal stability of the corresponding polybenzoxazines was supported by thermogravimetric analysis (TGA). The char yield of P(M-fa) and P(M-da) at 800 ℃ reached 69% and 41%, respectively. The limiting oxygen indexes (LOI) of the polybenzoxazine resins were higher than 30, suggesting a good flame retardancy. The use of polybenzoxazine for the corrosion protection of Q235 low-carbon steel was also studied. The results of open circuit voltage (OCP) curves and Tafel plots demonstrate that the polymer coatings provide good corrosion resistance. This study enriches the diversity of benzoxazine resins and is conductive to environmental protection and sustainable development.
2020, 46(2): 197-207.   doi: 10.14135/j.cnki.1006-3080.20190220001
[Abstract](1337) [FullText HTML](272) [PDF 1593KB](6)
Abstract:
A series of triphilic diblock copolymer blends, consisting of hydrophilic poly(ethylene glycol) monomethyl ether (PEG), hydrophobic polystyrene (PS) and superhydrophobic poly(1H,1H,5H-octafluoropentyl methacrylate) (POFPMA), were blended with two diblock copolymers PEG-PS and PEG-POFPMA. The two copolymers were successfully synthesized by atom transfer radical polymerization (ATRP) and single electron transfer living radical polymerization (SET-LRP), and were characterized by nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). Hydrophobic segments have been regarded as one of the most important limited factors for the preparation of nano-assemblies in aqueous solution. The transformation of a series of PEG-PS/PEG-POFPMA nano-assemblies were investigated by changing the polymerization degree of hydrophobic PS and superhydrophobic POFPMA, which were confirmed by dynamic light scattering (DLS), transmission electron microscope (TEM) and scanning electron microscopy (SEM). The results indicated that adjusting the ratio of the double hydrophobic blocks was an effective way to obtain rich assembled morphologies of the triphilic diblock blends, including spherical micelles, porous spheres, vesicles, spindle-like micelles and worm-like micelles. In addition, self-assembly based on one typical blend at different concentrations was also investigated, and it was obvious that the morphology evolved from the porous sphere to the coil structure, then to vesicle with the increase of concentration. The assembled morphologies of the blends changed from strip micelles to dendritic micelles, vesicles and porous spheres, and eventually led to the formation of spherical micelles by increasing the length of PS, but they were mainly affected by low concentration of the blends. Two detailed and regular binary phase diagrams based on the above results were concluded and served as a reliable reference for targeting predetermined nanoparticles before polymerization.
2020, 46(2): 208-218.   doi: 10.14135/j.cnki.1006-3080.20190128001
[Abstract](7503) [FullText HTML](3049) [PDF 1296KB](12)
Abstract:
Nowadays, photodynamic therapy(PDT) has become one of the promising and important cancer therapies. 5, 10, 15, 20-Tetraphenyl porphyrin(TPP), a unique and promising photosensitizer which can convert triplet oxygen(3O2) into singlet oxygen(1O2) after laser illumination, can be used to kill cancer cells. Due to the strong hydrophobicity of porphyrin molecules, porphyrins always need the physical encapsulation by different vehicles. However, the general physical encapsulation not only makes it difficult to quantify the loaded porphyrin content accurately, but also causes aggregation effects after the intracellular release, leading to a compromised PDT effect. Herein, we developed a NIR-triggered pH-responsive amphiphilic block copolymer as to serve as the photosensitizer and drug delivery system(DDS) for the combination of PDT therapy and chemotherapy. The well-defined block copolymer was composed of hydrophilic poly(ethylene glycol)(PEG) block, hydrophobic poly((diisopropylamino)ethyl methacrylate)(PDPA) block and a TPP unit at the junction point between PEG and PDPA. Such a copolymer was synthesized by the combination of RAFT polymerization and click chemistry. The amphiphilic pH-responsive block copolymer(PEG-PDPA-TPP) can self-assemble into spherical micelles in aqueous solution and perform as a perfect drug release platform. It is worthy to notice that the well-designed chemical structure of PEG-PDPA-TPP with TPP at the junction point leads to a relatively regular arrangement of TPP moieties between the hydrophobic and hydrophilic blocks instead of aggregating together, which can reduce the aggregation-induced quenching effect of the photosensitizers, thereby increasing the quantum yield of singlet oxygen. Meanwhile, the Doxorubicin(DOX)-loaded PEG-PDPA-TPP nanoparticles will dissociate under weak acidic conditions and release the drug after entering the cells by endocytosis. Therefore, this pH-responsive TPP-containing block copolymer provides a new strategy for cancer treatment.
2020, 46(2): 219-226.   doi: 10.14135/j.cnki.1006-3080.20190116004
[Abstract](6605) [FullText HTML](2601) [PDF 1113KB](8)
Abstract:
Poly(butylene terephthalate) (PBT), a semicrystalline polymer belonging to polyester family, is widely used in engineering applications due to its versatile combination of mechanical and thermal properties, chemical resistance, and high rates of crystallization. The physical and mechanical properties of the product are directly related to the microstructure, which is determined by the extent of crystallization and influenced by the nonisothermal conditions set forth during practical processing. Therefore, the nonisothermal crystallization kinetics can be used to clarify the crystallization behavior and provide a theoretical basis for the formation of crystals. In this paper, the epoxidized ethylene propylene diene rubber (eEPDM) was first successfully prepared by the epoxidation of ethylene propylene diene rubber (EPDM) using t-butyl hydroperoxide as an oxidant and molybdenum oxide as a catalyst. The prepared rubber was characterized by Fourier transform infrared spectroscopy (FT-IR) and 1H-nuclear magnetic resonance (1H-NMR). Then the PBT/Glass fiber (GF)/eEPDM composites with different eEPDM contents were prepared in a twin-screw extruder. The influence of eEPDM on the nonisothermal crystallization kinetics of PBT/GF was investigated using differential scanning calorimetry (DSC). The phase structure of PBT/GF/eEPDM was observed by scanning electron microscopy (SEM). Analysis of the crystallization data by Mozhishen model revealed that the presence of eEPDM could accelerate the nonisothermal crystallization rate of PBT in PBT/GF/eEPDM. The result was further proved by the effective activation energy calculated by Friedman method. The observation of SEM demonstrated that the interface performance was excellent among PBT, GF and eEPDM phases. Meanwhile, the mechanical properties of the specimens were evaluated.
2020, 46(2): 227-233.   doi: 10.14135/j.cnki.1006-3080.20190107002
[Abstract](957) [FullText HTML](325) [PDF 657KB](5)
Abstract:
In recent years, amber identification has still been a hot topic in academic research field. Amber, copal resin, pressed amber and heated copal resin are investigated using three non-destructive testing methods, including the conventional gemological testing method, Fourier transform infrared spectrum and Raman spectrum as a supplementary. From FT-IR testing results, amber, copal resin, pressed amber and heated copal resin have the similar basic FT-IR characteristics, such as absorption bands at 2 980—2 900 cm−1 and 2 900—2 800 cm−1 caused by the saturated C−H bond stretching vibration and the corresponding infrared absorption bands at 1 480—1 430 cm−1 and 1 400—1 350 cm−1 caused by CH2−CH3 bending vibration. Compared with amber, FT-IR characteristics of copal resin show infrared absorption at 889 cm−1, and FT-IR characteristics of pressed amber show strong absorption at 1 723 cm−1. When copal resin is heated, the absorption at 1 645 cm−1 is disappeared. Amber, copal resin, pressed amber and heated copal resin only have slight differences in the Raman shift. Compared with amber, copal resin lacks in the Raman shift at 1 720 cm−1. Through the exploration of its basic characteristics and analysis of the attribution of its functional group characteristic peaks, the differences and connections can be found among amber, copal resin, pressed amber and heated copal resin. The results show that the Gem identification should be combined with its physical and chemical properties and spectral characteristics.
2020, 46(2): 234-242.   doi: 10.14135/j.cnki.1006-3080.20190107001
[Abstract](6400) [FullText HTML](1703) [PDF 889KB](15)
Abstract:
The effects of reaction temperature on hydrothermal liquefaction (HTL) process of municipal sewage sludge (MSS) and on liquefied products characteristics were investigated. The results showed that the bio-crude yield and asphaltene yield reached the highest level at 370 ℃, which were 26.82% and 27.73%, respectively. The water recovery ratio and volume reduction ratio were also increased to the maximum value of 94.81% and 80.16%, respectively, indicating that improved effects on volume reduction of MSS were obtained after HTL process. The mass concentration of water-soluble organics dropped to 29.47 g/L, which demonstrated that higher reaction temperature would promote the decomposition of these water-soluble organics. The bio-crude was mainly composed of aliphatic acids, amines and aliphatic hydrocarbons, and the carbon chain length of aliphatic acids was located in between 16 and 18, which indicated that the properties of bio-crude were similar to those of diesel oil. The water-soluble organics were mainly composed of carboxylic acids, esters, amides and phenols while the existence of carboxylic acids would have detrimental influences on the growth of plants, the availability of soil nutrient and the biodiversity of environment. The gaseous products were mainly consisted of CO2 which could be explained by the decarboxylation taking place on the surface of MSS particles. The ash content of residual solids reached the highest level (79.72%) at 370 ℃, which showed that a better extraction rate of organic matters in residual solids could be obtained by HTL process. During the HTL process, the energy recovery ratio of liquid bio-fuels was between 53.23% and 98.20% at 270 ℃ to 370 ℃, indicating that more than half heating value of the MSS could be recovered to be liquid bio-fuels upon a HTL treatment.
2020, 46(2): 243-249.   doi: 10.14135/j.cnki.1006-3080.20181209001
[Abstract](6643) [FullText HTML](1862) [PDF 1053KB](9)
Abstract:
The conventional extreme learning machine (ELM) is sensitive to outliers. Aiming at the shortcoming, this paper proposes a robust extreme learning machine based on p-power Welsch loss. Firstly, the mean square error loss of the conventional ELM is replaced by the p-power Welsch loss to enhance the robustness of the proposed algorithm; Secondly, the l1 norm regularization is introduced into the objective function to reduce the complexity and improve the stability of the ELM network model; Moreover, a fast iterative shrinkage-thresholding algorithm (FISTA) is adopted to minimize the objective function so that the computational efficiency can be increased; Finally, the performance of the proposed method is verified by means of synthetic data and UCI datasets, which shows that the proposed algorithm can attain stronger robustness, better stability and lower training time.
2020, 46(2): 250-258.   doi: 10.14135/j.cnki.1006-3080.20190118001
[Abstract](7092) [FullText HTML](2293) [PDF 1287KB](17)
Abstract:
In this paper, two types of vehicle platoon following controllers are designed, respectively, according to the situation that the communication between vehicles is normal or interrupted in the driving process. Laser range finder and monocular camera are used as vehicle sensors. Firstly, the physical characteristic information of obstacles in the environment is collected from the laser sensor and the obtained data is clustered by means of the DBSCAN algorithm. The clustering result of obstacles in the environment is fitted to the physical shape with a minimum circumscribed rectangle, whose center point is taken as the center of each obstacle. Secondly, the angle of the leader vehicle is obtained from visual sensor. The color distribution information of the preceding vehicle is pre-defined. The Camshift algorithm is used for calculating the relative angle between the preceding and the following vehicle in each frame of picture. Thirdly, the information collected by two kinds of sensors is fused for designing controller. According to whether there exists the communication between the leader and the follower or not, this paper proposes two different controllers based on Lyapunov function and fuzzy control logic, respectively. When the communication between vehicles is normal, the Lyapunov-based controller design will be used. When there doesn’t exist the communication between vehicles, the fuzzy control strategy will be selected. If the vehicle does not resume communication within a certain period of time, it would move to a safety area to wait for repairing. Finally, the proposed algorithm is verified via the theoretical derivation and the simulation in robot operating system (ROS).
2020, 46(2): 259-268.   doi: 10.14135/j.cnki.1006-3080.20190218001
[Abstract](6710) [FullText HTML](2033) [PDF 1044KB](20)
Abstract:
Traditional intelligent optimization algorithms easily fall into local optimal and premature convergence for cloud computing task scheduling. Aiming at this shortcoming, this paper proposes a reverse learning behavior particle swarm optimization (RLPSO) algorithm. Firstly, a grouping strategy is adopted to divide the individuals into two different groups according to the gender of individuals and the individuals in different groups will perform different search behaviors. This strategy can increase the diversity of search mode and enhance the search ability. Secondly, the reverse learning and mating mechanism are introduced to avoid the local optimum. By means of the reverse learning mechanism, individuals will reversely learn from the target individuals with a certain probability, which can increase the ability of finding a new potential better solution. By using the mating mechanism, the worst individual in the swarm will be replaced by a new better individual so that the global search ability can be further enhanced. Moreover, the convergence of the RLPSO algorithm is discussed in detail. It is proven that the RLPSO algorithm will converge to an equilibrium. Finally, the effectiveness of the RLPSO algorithm is verified by simulation results. It is shown from the experiment results that the RLPSO algorithm exhibits better search performance than the other four algorithms for the large-scale task scheduling.
2020, 46(2): 269-276.   doi: 10.14135/j.cnki.1006-3080.20190107003
[Abstract](7085) [FullText HTML](2887) [PDF 729KB](23)
Abstract:
Facial action unit recognition task is one of the most important aspects of understanding facial expressions. However, the extremely unbalanced categories and the multi-label classification bring great difficulties for the design of recognition algorithm. By means of deep learning technique, this paper proposes a face action unit recognition algorithm. Firstly, based on the transfer learning theory and driven by the face recognition task, some large-scale datasets are used to pre-train the convolutional network so as to make this model has the ability to extract abstract features of face. Secondly, an objective function is designed to dynamically weigh the sample loss according to the classification confidence for making the model focus more on optimizing a few samples. Finally, two related tasks including the multi-label co-occurrence relationship fitting and the key-point regression of face are combined to jointly train and test the model. It is shown from the experimental results that the proposed method can effectively improve the classification accuracy and F1-score on the relevant datasets CK+ and MMI.
2020, 46(2): 277-283.   doi: 10.14135/j.cnki.1006-3080.20190114006
[Abstract](1384) [FullText HTML](443) [PDF 1526KB](7)
Abstract:
The automobile engine tensioner is an important component of the automobile engine belt system, which generates vibration during the working process. It is a difficult task to quantitatively calculate the mechanical properties of the tensioner. In this paper, the tensioner in the automobile engine belt system is selected as the research object, and the mechanical model is established for the vibration generated by the tensioner during the working process. The dynamic moment balance equation and dynamic energy balance equation of the mechanism are established as well. The calculation model is established with the work of each torque, and the method of numerical calculation of this model is also established. Combined with a specific example, the influences of the relevant parameters on the mechanical properties of the tensioner are studied, giving rise to the influence curves. The swing angle θ of the tensioner becomes smaller with the increase of the spring stiffness G2 when other parameters unchanged. The increase of the friction coefficient of the damping structure will make the vibration amplitude of the tensioner be smaller. With the fluctuation range of the tension increasing, the vibration range of the tensioner becomes larger. As the length L of the rotating arm increases, the amplitude of the tensioner will increase.
2020, 46(2): 284-292.   doi: 10.14135/j.cnki.1006-3080.20190103001
[Abstract](1646) [FullText HTML](1689) [PDF 2216KB](8)
Abstract:
Taking the plug valve as the research object, calculation model of the contact surfaces was established based on the deformation coupling model between the set screw of the plug valve and the cock. A leak identification algorithm for sealing surface considering fatigue cumulative damage of sealing surface asperities of plug valve was established by analyzing the microscopic contact of the plug valve’s sealing surfaces which are constructed by auto-correlation function. Taking plug valve F-2 ISO-STANDARD (1″) as the research example, the variation of plug valve fatigue life is numerically studied with the change of the number of tightening cycles of the set screw. It was shown that the life expectancy of the sealing surface of the plug valve was decreased with the increase of the numbers of screw tightening cycles, and was increased with the sealing surface roughness at the same tightening cycles. And the life expectancy of the sealing surface of the plug valve was decreased with the increase of the plug compression force, and was decreased with the sealing surface roughness at the same plug compression. The fatigue life of the sealing surface of plug valve was increased with the increase of the ratio of fluid pressure amplitude in the pipe, and was decreased with the increase of the limit pressure amplitude of the fluid in the pipe. The fatigue life of the sealing surface was first increased and then decreased with the increase of the average pressure of the fluid in pipe. This research provides a new method for the prediction of the fatigue life of the valve sealing surface, based on the fluctuation of fluid pressure in the pipe.
2020, 46(2): 293-300.   doi: 10.14135/j.cnki.1006-3080.20190108001
[Abstract](1321) [FullText HTML](194) [PDF 1606KB](7)
Abstract:
Taking bump-type gas foil bearing as the research object, the mechanical properties of bump foil are studied using the elastic mechanics theory, a force and deformation model is established, and a fluid-solid coupling algorithm is established on the basis of Reynolds equation of coercible gas. An example is given to compare the gas film pressure distribution and the film thickness distribution of elastic foil gas bearings with those of rigid gas bearings. It was found that the distribution shapes of the pressure and gas film were similar, but the maximum gas film pressure of the elastic foil gas bearings was smaller, while the minimum gas film thickness at the axial bisector was larger. With the same eccentricity, the friction torque of the elastic foil gas bearings was smaller than that of the rigid gas bearings, and the side leakage flow of gas was larger than that of the rigid gas bearings. The friction torque of the elastic foil gas bearings during working was smaller with less heat generation and faster heat dissipation. Increasing the thickness of bump foil (tB) or decreasing the wave distance of bump foil (s) can reduce both the minimum gas film thickness and the attitude angle of bearings. Decreasing tB or increasing s can reduce the friction torque resulting in less friction power loss and friction heat generation, as well as increase in the side leakage flow of gas resulting in faster heat dissipation.