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Effects of baffle position in serpentine flow channel on the performance of proton exchange membrane fuel cells

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Chinese Journal of Chemical Engineering 2024年第5期69卷 250-262页

作者： Guodong Xia Xiaoya Zhang Dandan Ma MOE key laboratory of Enhanced Heat Transfer and Energy Conservation Beijing Key Laboratory of Heat Transfer and Energy ConversionBeijing University of TechnologyBeijing 100124China

This study used a three-dimensional numerical model of a proton exchange membrane fuel cell with five types of channels:a smooth channel(Case 1);eight rectangular baffles were arranged in the upstream(Case 2),midstream(Case 3),downstream(Case 4),and the entire cathode flow channel(Case 5)to study the effects of baffle position on mass transport,power density,net power,***,the effects of back pressure and humidity on the voltage were *** showed that compared to smooth channels,the oxygen and water transport facilitation at the diffusion layer-channel interface were added 11.53%-20.60%and 7.81%-9.80%at 1.68 A·cm^(-2)by adding *** closer the baffles were to upstream,the higher the total oxygen flux,but the lower the flux uniformity the worse the water *** oxygen flux of upstream baffles was 8.14%higher than that of downstream baffles,but oxygen flux uniformity decreased by 18.96%at 1.68 A·cm^(-2).The order of water removal and voltage improvement was Case 4>Case 5>Case 3>Case 2>Case *** power of Case 4 was 9.87%higher than that of the smooth *** the Case 4,when the cell worked under low back pressure or high humidity,the voltage increments were *** potential increment for the back pressure of 0 atm was 0.9%higher than that of 2 atm(1 atm=101.325 kPa).The potential increment for the humidity of 100%was 7.89%higher than that of 50%.

关键词： Proton exchange membrane fuel cell Baffle position Mass transfer Net power Uniformity Voltage increment

Improving actionable warning identification via the refined warning-inducing context representation

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Science China(Information Sciences) 2024年第5期67卷 321-322页

作者： Xiuting GE Chunrong FANG Xuanye LI Quanjun ZHANG Jia LIU Zhihong ZHAO Zhenyu CHEN State key laboratory for Novel Software technology Nanjing University

Static analysis tools(SATs) have shown potential ability in software quality assurance [1]. However, SATs report an overwhelming number of warnings, where most warnings are unactionable ones(i.e., warnings that are not acted on or fixed by developers). It is not a trivial task for developers to find actionable warnings(i.e., warnings that are acted on and fixed by developers) in all reported warnings. Hence,the excessive unactionable warnings seriously impede the usability of SATs [2].

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Structural Optimization of the Inlet Header of Supercritical Carbon Dioxide Printed Circuit Board Heat Exchanger

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Journal of Thermal Science 2024年第4期33卷 1458-1467页

作者： WANG Yanquan LU Yuanwei WANG Yuanyuan HAN Xinlong WU Yuting GAO Qi MOE key laboratory of Enhanced Heat Transfer and Energy Conservation Beijing Key Laboratory of Heat Transfer and Energy ConversionBeijing University of TechnologyBeijing100124China

Supercritical carbon dioxide printed circuit board heat exchangers are expected to be applied in third-generation solar thermal power ***,the uniformity of supercritical carbon dioxide entering the heat exchanger has a significant impact on the overall performance of the heat *** order to improve the uniformity of flow distribution in the inlet header,this article studies and optimizes the inlet header of a printed circuit board heat exchanger through numerical *** results indicate that when supercritical carbon dioxide flows through the header cavity,eddy currents will be generated,which will increase the uneven distribution of flow rate,while reducing the generation of eddy currents will improve the uniform distribution of flow *** the dimensionless factor of the inlet header is 6,the hyperbolic configuration is the optimal *** also reduced the eddy current region by adding transition segments,and the results showed that the structure was the best when the dilation angle was 10°,which reduced the non-uniformity by 21%compared to the hyperbolic configuration,providing guidance for engineering practice.

关键词： third-generation solar thermal power generation inlet header PCHE numerical simulation

Design Optimization and Operating Performance of S-CO_(2) Brayton Cycle under Fluctuating Ambient Temperature and Diverse Power Demand Scenarios

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Journal of Thermal Science 2024年第1期33卷 190-206页

作者： YANG Jingze YANG Zhen DUAN Yuanyuan key laboratory for Thermal Science and Power Engineering of MOE Beijing Key Laboratory for CO_(2) Utilization and Reduction TechnologyTsinghua UniversityBeijing 100084China

The supercritical CO_(2)(S-CO_(2)) Brayton cycle is expected to replace steam cycle in the application of solar power tower system due to the attractive potential to improve efficiency and reduce *** the concentrated solar power plant with thermal energy storage is usually located in drought area and used to provide a dispatchable power output,the S-CO_(2) Brayton cycle has to operate under fluctuating ambient temperature and diverse power demand *** addition,the cycle design condition will directly affect the off-design *** this work,the combined effects of design condition,and distributions of ambient temperature and power demand on the cycle operating performance are analyzed,and the off-design performance maps are proposed for the first time.A cycle design method with feedback mechanism of operating performance under varied ambient temperature and power demand is introduced *** show that the low design value of compressor inlet temperature is not conductive to efficient operation under low loads and sufficient output under high ambient *** average yearly efficiency is most affected by the average power demand,while the load cover factor is significantly influenced by the average ambient *** multi-objective optimization,the optimal solution of designed compressor inlet temperature is close to the minimum value of35℃ in Delingha with low ambient temperature,while reaches 44.15℃ in Daggett under the scenario of high ambient temperature,low average power demand,long duration and large value of peak load during the peak temperature *** the cycle designed with compressor inlet temperature of 35℃ instead of 44.15℃ in Daggett under light industry power demand,the reduction of load cover factor will reach 0.027,but the average yearly efficiency can barely be improved.

关键词： supercritical CO_(2)Brayton cycle ambient temperature fluctuating power demand scenarios design optimization off-design performance

Enhanced Photocatalytic Activity of Z-scheme Meso-BiVO_(4)-Au-CdS for Degradation of Rhodamine B

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Journal of Wuhan University of technology(Materials Science) 2024年第4期39卷 869-876页

作者：张雁伟 WANG Yanze LI Junguo XIE Jingjing 王文宣 FU Zhengyi State key laboratory of Advanced technology for Materials Synthesis and Processing Wuhan University of TechnologyWuhan 430070China Hubei Longzhong laboratory Xiangyang 441000China

We synthesized BiVO_(4)mesocrystals with ordered assembly structure,and studied the structural order and the relationship between the photodegradation of Rhodamine *** nanoparticles(NPs)were successfully loaded onto Meso-BiVO_(4)by light-assisted induction,and Cd nanoparticles were further selected to be deposited on Au nanoparticles to form Z-scheme photocatalyst Meso-BiVO_(4)-Au-CdS *** try and propose to analyze its ordered assembly structure by XRD for the first *** results show that Meso-BiVO_(4)is a mesocrystal with highly exposed(001)plane and directional assembly *** charge separation efficiency of all samples was studied by PL *** results show that the Z-scheme Meso-BiVO_(4)-Au-CdS can promote the charge separation and obtain the best carrier separation ***,it has the best photocatalytic activity in the experiment of photocatalytic degradation of rhodamine *** main active species in the degradation process were confirmed by free radical trapping experiment,and the degradation mechanism was put forward.

关键词： biomineralization photosynthesis mesocrystal photocatalysis TiO_(2) BiVO_(4)

Numerical Study on Heat Transfer and Frictional Resistance of Two Types of Molten Salts in Straight Channels and Supercritical Carbon Dioxide in Airfoil Channels

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Journal of Thermal Science 2024年第4期33卷 1443-1457页

作者： WANG Yanquan LU Yuanwei GAO Qi LI Feng MA Yancheng WANG Yuanyuan WU Yuting MOE key laboratory of Enhanced Heat Transfer and Energy Conservation Beijing Key Laboratory of Heat Transfer and Energy ConversionBeijing University of TechnologyBeijing100124China

Molten salt and supercritical carbon dioxide(sCO_(2))are considered to be one of the most promising combined heat transfer refrigerants for third-generation solar thermal power *** evaluate the potential of chloride salts and carbonates in third-generation solar thermal power generation,this paper uses molten salts and sCO_(2)as the working media of printed circuit board heat exchangers(PCHE),and uses numerical simulation to study the heat transfer and friction of PCHE channels with different molten salts and sCO_(2),and establishes predictive correlations respectively.A local heat transfer and friction study was conducted on the sCO_(2)side of the airfoil channel,and it was found that the inlet mass flow rate has a significant impact on it,while the inlet temperature has a relatively small impact.A comprehensive comparison was made between the heat transfer and friction of two molten salts,and the comprehensive performance of chloride salts was 70%-80%higher than that of *** results indicate that the potential of chloride salts in third-generation solar thermal power generation is much greater than that of carbonates.

关键词： third generation solar thermal power generation sCO_(2) PCHE molten salt

pH-Responsive polymer boosts cytosolic siRNA release for retinal neovascularization therapy

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Acta Pharmaceutica Sinica B 2024年第2期14卷 781-794页

作者： Shuai Guo Chunhui Li Changrong Wang Xiaowen Cao Xinyue Liu Xing-Jie Liang Yuanyu Huang Yuhua Weng School of medical technology Advanced Research Institute of Multidisciplinary ScienceSchool of Life ScienceKey Laboratory of Molecular Medicine and BiotherapyKey Laboratory of Medical Molecule Science and Pharmaceutics EngineeringBeijing Institute of TechnologyBeijing 100081China School of Pharmacy Shandong New Drug Loading&Release Technology and Preparation Engineering LaboratoryBinzhou Medical UniversityYantai 264003China School of Ophthalmology and Optometry School of Biomedical EngineeringThe Eye HospitalWenzhou Medical UniversityWenzhou 325027China Chinese Academy of Sciences(CAS) Key Laboratory for Biomedical Effects of Nanomaterials and NanosafetyCAS Center for Excellence in NanoscienceNational Center for Nanoscience and Technology of ChinaBeijing 100190China

Small interfering RNA(siRNA)has a promising future in the treatment of ocular diseases due to its high efficiency,specificity,and low toxicity in inhibiting the expression of target genes and ***,due to the unique anatomical structure of the eye and various barriers,delivering nucleic acids to the retina remains a significant *** this study,we rationally design PACD,an A-B-C type non-viral vector copolymer composed of a hydrophilic PEG block(A),a siRNA binding block(B)and a pH-responsive block(C).PACDs can self-assemble into nanosized polymeric micelles that compact siRNAs into polyplexes through simple *** evaluating its pH-responsive activity,gene silencing efficiency in retinal cells,intraocular distribution,and anti-angiogenesis therapy in a mouse model of hypoxia-induced angiogenesis,we demonstrate the efficiency and safety of PACD in delivering siRNA in the *** are surprised to discover that,the PACD/siRNA polyplexes exhibit remarkable intracellular endosomal escape efficiency,excellent gene silencing,and inhibit retinal *** study provides design guidance for developing efficient nonviral ocular nucleic acid delivery systems.

关键词： SiRNA Oculardeliverysystem Block polymer Endosomalescape Retinal neovascularization Blood-retinal barrier VEGFA Safety

Numerical Study on the Aerodynamic and Fluid−Structure Interaction of An NREL-5MW Wind Turbine

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China Ocean Engineering 2024年第3期38卷 363-378页

作者： ZHAO Mi YU Wan-li WANG Pi-guang QU Yang DU Xiu-li key laboratory of Urban Security and Disaster Engineering of Ministry of Education Beijing University of TechnologyBeijing 100124China State key laboratory of Bridge Engineering Safety and Resilience Beijing University of TechnologyBeijing 100124China

A 5-MW wind turbine has been modeled and analyzed for fluid-structure interaction and aerodynamic *** this study, a full-scale model of a 5-MW wind turbine is first developed based on a computational fluid dynamics(CFD) approach, in which the unsteady, noncompressible Reynolds Averaged Navier-Stokes(RANS) method is used. The main focus of the study is to analyze the tower shadow effect on the aerodynamic performance of the wind turbine under different inlet flow conditions. Subsequently, the finite element model is established by considering fluid/structure interactions to study the structural stress, displacement, strain distributions and flow field information of the structure under the uniform wind speed. Finally, the fluid-structure interaction model is established by considering turbulent wind and the tower shadow effect. The variation rules of the dynamic response of the one-way and two-way fluid-structure interaction(FSI) models under different wind speeds are analyzed, and the numerical calculation results are compared with those of the centralized mass model. The results show that the tower shadow effect and structural deformation are the main factors affecting the aerodynamic load fluctuation of the wind turbine, which in turn affects the aerodynamic performance and structural stability of the blades. The structural dynamic response of the coupled model shows significant similarity, while the structural displacement response of the former exhibits less fluctuation compared with the conventional centralized mass model. The one-way fluid-structure interaction(FSI)model shows a higher frequency of stress-strain and displacement oscillations on the blade compared with the two-way FSI model.

关键词： computational fluid dynamics methods(CFD) tower shadow effect aerodynamic performance fluidstructure interaction space flow field

Machine learning enabled film pressure sensor to identify surface contacts:An application in surface transmission of infectious disease

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Building Simulation 2024年第6期17卷 1023-1036页

作者： Baotian Chang Jianchao Zhang Yingying Geng Jiarui Li Doudou Miao Nan Zhang Beijing key laboratory of Green Built Environment and Energy Efficient technology Beijing University of TechnologyBeijing100124China

The global prevalence of infectious diseases has emerged as a significant challenge in recent *** transmission is a potential transmission route of most gastrointestinal and respiratory infectious diseases,which is related to surface touch *** observation,the traditional method of surface touching data collection,is characterized by limited accuracy and high labor *** this work,we proposed a methodology based on machine learning technologies aimed at obtaining high-accuracy and low-labor-cost surface touch behavioral data by means of sensor-based contact *** touch sensing device,primarily utilizing a film pressure sensor and Arduino board,is designed to automatically detect and collect surface contact data,encompassing pressure,duration and *** make certain the surface touch behavior and to describe the behavioral data more accurately,six classification algorithms(*** Vector Machine and Random Forest)have been trained and tested on an experimentally available dataset containing more than 500 surface *** classification results reported the accuracy of above 85%for all the six classifiers and indicated that Random Forest performed best in identifying surface touch behaviors,with 91.8%accuracy,91.9%precision and 0.98 *** study conclusively demonstrated the feasibility of identifying surface touch behaviors through film pressure sensor-based data,offering robust support for the calculation of viral load and exposure risk associated with surface transmission.

关键词： surface transmission touch behavior film pressure sensor random forest infectious disease