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28 September 2021, Volume 55 Issue 9 Previous Issue    Next Issue

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Effect of Preparation Process of La0.95FeO3-δ/C Composite Electrode on Preparation and Bifunctional Electrocatalytic Properties HU Huanming, YANG Fan, ZHANG Junliang 2021, 55 (9):  1049-1057.  doi: 10.16183/j.cnki.jsjtu.2021.009 Abstract ( 779 )   HTML ( 1491 )   PDF (9736KB) ( 750 )   Save In order to optimize the bifunctional electrocatalytic performance of La0.95FeO3-δ, the effects and influencing mechanism of carbon morphology, electrode ink preparation, and catalyst loading on the bifunctional electrocatalytic performance of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) were investigated. The results show that compared with La0.95FeO3-δ, the catalytic activity of La0.95FeO3-δ/C is significantly improved. The bifunctional electrocatalytic performance of La0.95FeO3-δ/C is mainly dependent on carbon morphology and electrode ink preparation. An optimum bifunctional performance is achieved in a composite electrode with 0.6 mg/cm2 La0.95FeO3-δ and 0.12 mg/cm2 EC600JD prepared by ultrasonic dispersion, ball milling, and ultrasonic dispersion. The optimized La0.95FeO3-δ/C has an excellent bifunctional electrocatalytic performance, simple preparation, and low cost, which is expected to be applied in Li-O2 batteries. Figures and Tables | References | Related Articles | Metrics

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Efficient Construction of Novel C3-Silyl Substituted Chiral Proline Catalysts TAN Fuxin, LI Zihao, ZHOU Jia, ZHANG Shuyu 2021, 55 (9):  1058-1063.  doi: 10.16183/j.cnki.jsjtu.2021.038 Abstract ( 611 )   HTML ( 344 )   PDF (961KB) ( 411 )   Save In order to apply the C-H activation strategy to the development of chiral organic catalysts, two novel C3-trimethylsilyl substituted chiral proline catalysts are designed and synthesized using L-proline as the starting material and C(sp 3)-H silylation as the key step, which are applied to the asymmetric aldol reaction of p-nitrobenzaldehyde with acetone and the asymmetric Mannich reaction of imine with β-methylbutyraldehyde, respectively. Both target products can be synthesized with a good enantioselectivity. This strategy effectively enriches the means of structural modification of proline and provids a new method for the development of new silicon-containing organic catalysts. Figures and Tables | References | Related Articles | Metrics

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Preparation and Immunoassay Application of Polyethylene Glycol Grafted Styrene Maleic Acid Copolymer Composite Microspheres ZHANG Xiannan, LENG Yuankui, WU Weijie, LI Wanwan 2021, 55 (9):  1064-1070.  doi: 10.16183/j.cnki.jsjtu.2020.029 Abstract ( 765 )   HTML ( 327 )   PDF (2309KB) ( 453 )   Save In the quantum dot-encoded microspheres based on the suspension array technology, the nonspecific biofouling will decrease the detection sensitivity and the multiplex detection ability. In order to inhibit the nonspecific biofouling, the polyethylene glycol grafted styrene maleic acid copolymer (PEG-g-PSMA) was used as substrate, and the CuInS2/ZnS quantum dot-encoded PEG-g-PSMA fluorescent microspheres were fabricated via the Shirasu porous glass (SPG) membrane emulsification-emulsion solvent evaporation technique. The grafting ratio and the chain length of PEG in PEG-g-PSMA were controlled by adjusting the feed mass and relative molecular mass of methoxy polyethylene glycol (mPEG), respectively. The microspheres were further applied to the immunoassay of CA199. The results of morphology and fluorescence properties show that the prepared microspheres are spherical and monodisperse, with an average particle size of 5 μm, and the internal quantum dots and fluorescence distribution are uniform. Immunoassay shows that the microspheres can significantly inhibit the nonspecific adsorption. When the optimal grafting ratio of PEG is 30 and the relative molecular mass of PEG is 1000, the limit of detection (LOD) to CA199 reaches up to 0.9 kU/L (1 U=1 μmol/min). The PEG-g-PSMA fluorescent microspheres can be prepared in large quantites by this method and have a promising application in multiplex immunoassay. Figures and Tables | References | Related Articles | Metrics

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Analysis of Factors and Significances of Adsorption Kinetics R115/NaX System ZHANG Jinke, MIAO Guangwu, JIN Jiamin, CHEN Yinfei, LU Hanfeng, NING Wensheng, BAI Zhanqi, LIU Wucan 2021, 55 (9):  1071-1079.  doi: 10.16183/j.cnki.jsjtu.2020.065 Abstract ( 739 )   HTML ( 132 )   PDF (1015KB) ( 409 )   Save To understand the adsorption kinetic mechanism of chloropentafluoroethane (R115) on NaX and then to guide the industrial applications of R115 adsorption removal and catalytic conversion, the effect of R115 concentration (referring to volume fraction) and adsorbent particle size on adsorption performance are studied by using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. The applicability of the Thomas model and Yan model for breakthrough curve analysis are compared. A two-level three-factor experimental method is implemented to evaluate the significance and possible correlations of R115 concentration, adsorbent mass, and flow rate on adsorption performance. The results indicate that the adsorption process is mainly controlled by R115 external film diffusion. The Yan model and the pseudo-first-order adsorption kinetic model fit the experimental data better. The adsorbent mass is the most important factor significantly affecting the breakthrough time, saturation time, volume of effluent treated per gram of adsorbate, and fractional bed utilization. The interaction of adsorbent mass and flow rate has a significant effect on the volume of effluent treated per gram of adsorbate. Figures and Tables | References | Related Articles | Metrics

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Short-Term Wind Speed Forecasting Model Based on Mutual Information and Recursive Neural Network WANG Yan, CHEN Yaoran, HAN Zhaolong, ZHOU Dai, BAO Yan 2021, 55 (9):  1080-1086.  doi: 10.16183/j.cnki.jsjtu.2020.433 Abstract ( 841 )   HTML ( 73 )   PDF (3483KB) ( 542 )   Save The volatility and randomness of wind speed have caused potential safety hazards to wind power grid integration. Improving wind speed forecasting is crucial to the stability of wind power systems and the development of wind energy. A novel short-term wind speed forecasting model (MI-RNN) was proposed based on mutual information (MI) and recursive neural network (RNN). In this model, the MI theory was introduced to select the optimal length of historical wind speed sequence (τ), and the method of using each τ step to forecast wind speed at the next time point was adopted to input the historical wind speed data into RNN for model training. The final wind speed forecasting result was output by the trained RNN model. Besides, the MI-RNN model was applied to the wind speed dataset collected from a wind farm and the forecasting accuracy was compared with that of the traditional wind forecasting methods. The results show that the MI-RNN model has achieved a higher forecasting accuracy compared with the commonly used wind farm wind speed forecasting methods, and can accurately forecast the future wind direction, which is expected to be applied to wind speed forecasting of wind farms with spatial dimensions. Figures and Tables | References | Related Articles | Metrics

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Thermal Experimental and Numerical Study on Performance of a Novel Conical Swirl-Vane Steam Separator XU Dehui, GU Hanyang, LIU Li, HUANG Chao 2021, 55 (9):  1087-1094.  doi: 10.16183/j.cnki.jsjtu.2020.038 Abstract ( 636 )   HTML ( 115 )   PDF (2981KB) ( 545 )   Save A full-scale novel conical swirl-vane steam separator with a conical barrel is studied by test and numerical methods using steam and water as working fluids. The test results indicate that the separation efficiency of the separator decreases first and then increases with the increase of steam superficial velocity. But this phenomenon is not obvious at low steam superficial velocities. The pressure drop of the separator increases significantly with the increase of steam superficial velocity. Based on the commercial software STAR-CCM+ and Euler-Euler two-fluid model, a numerical simulation is conducted to study the effect of droplet size on the separation efficiency and pressure drop of the swirl-vane separator. The numerical results imply that large droplets promote the liquid separation. However, the pressure drop is insensitive to the droplet size. According to the test results, a numerical model that is in good agreement with the test is established, and the distribution of presssure, velocity, and water volume fraction are analyzed in detail. Figures and Tables | References | Related Articles | Metrics

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Analysis of Frictional Pressure Drop Correlations of Refrigerant Two-Phase Flow in Mini-Channel LIU Xucheng, GU Bo, ZENG Weijie, DU Zhongxing, TIAN Zhen 2021, 55 (9):  1095-1107.  doi: 10.16183/j.cnki.jsjtu.2020.159 Abstract ( 652 )   HTML ( 149 )   PDF (1523KB) ( 498 )   Save This paper presents a comprehensive analysis of the frictional pressure drop correlations in two-phase flow in mini-channel, describes the relationship of inheritance and development between the correlations, and points out the innovation between different correlations. In order to evaluate the universality and precision of various correlations, it establishes a large frictional pressure drop database, which is specialized for mini-channels. This database includes 1302 and 1576 data points under evaporation and condensation/adiabatic conditions, respectively. Finally, it evaluates and analyzes 26 correlations under different conditions. The results show that the Sempértegui-Tapia and the Kim correlation have the best prediction ability under evaporation conditions and condensation/adiabatic conditions, respectively. This paper provides some advice on the improvement of correlation. Figures and Tables | References | Related Articles | Metrics

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Stability Analysis and Support Suggestions of Pile Hole Based on Mud Pressure Balance Earth Pressure XIONG Guojun, WANG Jianhua, CHEN Jinjian 2021, 55 (9):  1108-1115.  doi: 10.16183/j.cnki.jsjtu.2018.330 Abstract ( 628 )   HTML ( 71 )   PDF (1146KB) ( 643 )   Save Based on the principle of mud pressure balance earth pressure, this paper establishes a mechanical model for analyzing the stability of pile hole, and analyzes the applicable conditions and application scopes of the three construction methods, namely, no-support excavation, the hole formation method by mud retaining wall, and the hole formation method by hard support. It also provides reasonable determination methods for maximum depth of pore-creating without support, lower limit value of mud weight of protecting wall, and useful tables. The research results show that the friction angle, the cohesion, and the mud weight of soil are basic factors for maintaining the stability of the pile hole. When the depth of pore-forming is less than the maximum depth of pore-creating without support, no-support excavation can be adopted. Otherwise, hole-forming should be assisted by slurry-support, and mud weight should not be less than the lower limit value of mud weight for the retaining wall determined by the site soil. When the friction angle is greater than 25°, mud weight can be arbitrarily selected. When the lower limit value of mud weight for the retaining wall calculated by look-up table is greater than the maximum mud weight given by specification, casing or other hard support measures should be adopted. Figures and Tables | References | Related Articles | Metrics

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Dynamic Response of Marine Pile Foundation Under Combined Action of Wind and Wave Loads LI Wanling, ZHANG Qi, ZHOU Xianglian 2021, 55 (9):  1116-1125.  doi: 10.16183/j.cnki.jsjtu.2019.246 Abstract ( 763 )   HTML ( 65 )   PDF (10784KB) ( 405 )   Save In order to study the dynamic response of a single pile foundation under combined action of wind and wave loads in the marine environment, a three-dimensional unidirectional coupling numerical model of wind wave-seabed-single pile is established. The Reynolds average N-S equation and the Biot dynamic equation are used to control the wave motion and seabed response respectively. Based on the verification of the rationality of the model, the influence of wind and wave parameters (such as wind speed, wind shear coefficient, and wave height) on the response of fluid and pile foundation under combined action of wind and wave loads are explored. The results show that the increase of wind speed, wind shear coefficient, and wave height will aggravate the fluid deformation around the pile, accelerate the wave propagation, and then affect the horizontal displacement and bending moment of the pile. Therefore, when calculating the bearing capacity of offshore pile foundations, the combined effect of wind and wave loads on the pile foundation should be considered comprehensively. The results will provide an important theoretical basis for the study of the bearing performance of pile foundations in harsh marine environments. Figures and Tables | References | Related Articles | Metrics

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Calculation Method of Pile Foundation Settlement Displacement Based on Virtual Column Equivalent Model WANG Rongyong, LIU Linqi, WANG Yingyi, HUANG Xingchun 2021, 55 (9):  1126-1133.  doi: 10.16183/j.cnki.jsjtu.2020.383 Abstract ( 667 )   HTML ( 123 )   PDF (1084KB) ( 511 )   Save According to the engineering characteristics of pile foundation in soft soil layer, a virtual column structure model was proposed, and a theoretical solution to pile foundation settlement displacement was established. Besides, the load transfer characteristics of pile foundation in soft soil layer, the bearing mode of pile foundation, and its dynamic relationship with the gradual evolution of load and environmental conditions were studied. The results show that there are friction bearing and friction with pile end bearing modes in pile foundation, and they change significantly with pile top load, construction, and environmental factors. Affected by the load transfer law, there is a 0-axis force section in the axial direction of pile foundation. The relationship between the depth and the length of pile foundation affects the type of bearing mode and displacement calculation results. The field results verify the correctness and applicability of the theoretical method. Figures and Tables | References | Related Articles | Metrics

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Impact of Continuous RESET/SET Operations on Endurance Characteristic of Phase Change Memory WU Lei, CAI Daolin, CHEN Yifeng, LIU Yuanguang, YAN Shuai, LI Yang, YU Li, XIE Li, SONG Zhitang 2021, 55 (9):  1134-1141.  doi: 10.16183/j.cnki.jsjtu.2020.028 Abstract ( 605 )   HTML ( 136 )   PDF (2205KB) ( 463 )   Save In order to explore the effects of continuous RESET operations and continuous SET operations on the endurance characteristic of phase change memory (PCM), the endurance characteristics of PCM at different ratios of RESET-SET times are studied based on a 4Mbit PCM chip. The variation of resistance distributions of PCM after continuous RESET and continuous SET operations are measured. The endurance characteristics of PCM in RESET-only and SET-only operations are compared with the typical endurance characteristic. Besides, the causes and repair methods of failure are also discussed. Moreover, the endurance characteristics of PCM at 8 different RESET-SET ratios are compared. The research results show that continuous RESET operation has little effect on the endurance characteristic of PCM, and the endurance characteristic of PCM in the RESET-only mode is on the same order as the typical endurance characteristic. However, the continuous SET operation has a significantly destructive effect on the endurance characteristic of PCM, and the endurance characteristic of PCM in the SET-only mode is 2 orders of magnitude lower than the typical endurance characteristic. The failure process of PCM caused by continuous RESET operation is irreversible while the failure process of PCM caused by continuous SET operation can be repaired by intermittent RESET operation. Figures and Tables | References | Related Articles | Metrics

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Design of Fast Steering Mirror Based on Displacement Amplification Mechanism XIE Yong, LIU Chongfei, JIA Jianjun, DAI Jiansheng 2021, 55 (9):  1142-1150.  doi: 10.16183/j.cnki.jsjtu.2020.103 Abstract ( 954 )   HTML ( 161 )   PDF (5785KB) ( 757 )   Save According to the current situation that the deflection angle of the piezoelectric ceramics direct drive fast steering mirror (FSM) is restricted by small elongation of piezoelectric ceramics and the large deflection angle cannot be realized, a novel piezoelectric FSM is designed. A two-stage lever-type amplification mechanism is adopted to realize the amplification of small displacement of piezoelectric ceramics and a strain gauge attached to the amplification mechanism is considered as the displacement sensor. The experimental results indicate that the deflection angle of the designed FSM is larger than 50 mrad, and the closed-loop linearity is below 0.5%, which satisfies the requirements of large deflection angle and accuracy pointing for light beam. Figures and Tables | References | Related Articles | Metrics

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Biocompatibility and Biosafety Analysis of Transcutaneous Energy Transfer System of Artificial Anal Sphincter YANG Chen, YAN Guozheng, ZHOU Zerun, HUA Fangfang 2021, 55 (9):  1151-1157.  doi: 10.16183/j.cnki.jsjtu.2020.196 Abstract ( 591 )   HTML ( 135 )   PDF (8581KB) ( 252 )   Save The biosafety and biocompatibility after implantation of the transcutaneous energy transfer system of artificial anal sphincter is verified by combining simulation and experiment in this paper. The biosafety study is based on the simulation of bioelectromagnetic radiation experiment and the thermal rise during the charging period while the biocompatibility study is based on the coloration experiment of the tissue around the energy supply system during the in vivo experiment. The results of biosafety indicate that the transcutaneous energy transfer system performs excellently in bioelectromagnetic safety in the experimental environment with a resonance frequency of 110 kHz and an output power of 10 W. In addition, the local specific absorption rate is far below the international human electromagnetic safety standard. After 30 minutes of fast charging, the system temperature increases by 2.81 ℃, which is lower than the temperature threshold of 4.8 ℃, demonstrating the outstanding biothermal safety of the system. The section staining experiment of the wireless energy supply system indicates that the poly-ether-ether-ketone (PEEK) shell can significantly reduce immune rejection and improve the biocompatibility of the system. Figures and Tables | References | Related Articles | Metrics

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A Domain Adaptive Semantic Segmentation Network Based on Improved Transformation Network ZHANG Junning, SU Qunxing, WANG Cheng, XU Chao, LI Yining 2021, 55 (9):  1158-1168.  doi: 10.16183/j.cnki.jsjtu.2019.307 Abstract ( 657 )   HTML ( 142 )   PDF (24999KB) ( 597 )   Save Due to the high cost and time-consumption of artificial semantic tags, domain-based adaptive semantics segmentation is very necessary. For scenes with large gaps or pixels, it is easy to limit model training and reduce the accuracy of semantic segmentation. In this paper, a domain adaptive semantic segmentation network (DA-SSN) using the improved transformation network is proposed by eliminating the interference of large gap pictures and pixels through staged training and interpretable masks. First, in view of the problem of large domain gaps from some source graphs to target graphs and the difficulty in network model training, the training loss threshold is used to divide the source graph dataset with large gaps, and a phased transformation network training strategy is proposed. Based on the ensurance of the semantic alignment of small gap source images, the transformation quality of large gap source images is improved. In addition, in order to further reduce the gap between some pixels in the source image and the target image area, an interpretable mask is proposed. By predicting the gap between each pixel in the source image domain and the target image domain, the confidence is reduced, and the training loss of the corresponding pixel is ignored to eliminate the influence of large gap pixels on the semantic alignment of other pixels, so that model training only focuses on the domain gap of high-confidence pixels. The results show that the proposed algorithm has a higher segmentation accuracy than the original domain adaptive semantic segmentation network. Compared with the results of other popular algorithms, the proposed method obtains a higher quality semantic alignment, which shows the advantages of the proposed method with high accuracy. Figures and Tables | References | Related Articles | Metrics

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Hierarchical Mission Planning for Cleaning Photovoltaic Panels Based on Improved Genetic Algorithm LI Cuiming, WANG Ning, ZHANG Chen 2021, 55 (9):  1169-1174.  doi: 10.16183/j.cnki.jsjtu.2020.254 Abstract ( 759 )   HTML ( 154 )   PDF (1893KB) ( 486 )   Save Aimed at the mission planning for cleaning photovoltaic panels in large-area photovoltaic plants with mobile cleaning robots, a district planning strategy is hereby proposed. The photovoltaic plants, considering the position of wind gaps, the illumination time, and other environmental factors, adopt a hierarchical mission planning based on the cleaning priority, and use the Hamilton graph to turn the cleaning problem of photovoltaic panels into a travelling salesman problem (TSP). Considering the disadvantages of low efficiency and early convergence of the genetic algorithm, an improved genetic algorithm, which includes the hybrid selection operator combining the tournament selection with the roulette wheel selection and the crossover operator based on the segmentation rule is thus put forward. The improved genetic algorithm is applied to plan the cleaning order of robots to clean the photovoltaic panels. The experimental results show that in comparison with the adaptive genetic algorithm, the improved genetic algorithm has a higher efficiency and better results. Figures and Tables | References | Related Articles | Metrics