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Towards mass applications: A review on the challenges and developments in metallic bipolar plates for PEMFC

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Progress in Natural Science:Materials International 2020年第6期30卷 815-824页

作者： Zhutian Xu Diankai Qiu Peiyun Yi Linfa Peng Xinmin Lai state Key Laboratory of Mechanical System and Vibration Shanghai Jiao Tong University

The industrial applications of proton exchange membrane fuel cell(PEMFC) technology have attracted tremendous capitals and research attention in the last ten years. However, there are still many bottlenecking problems before the progress triumphs. Among them, a core challenge is the improvement of bipolar plates(BPs).As a key component of PEMFC, the BPs undertake the crucial functions of distributing reactant gases and cooling medium, collecting the electricity generated, exporting waste products, etc. Due to the unique advantages of ultra-thin, high strength, easy-to-mass-produce, etc., metallic BPs have been considered as the promising solution for the automotive and aerospace application scenarios with a strong requirement of power density. However,many challenges remain to be conquered in metallic BPs to fully meet all the requirements in those industrial applications such as corrosion, toxic ion emission and fabrication. The aim of this work is to provide an overview of the important researches in recent years dealing with the most critical problems of metallic BPs before industrial applications. The future studying directions in material and processing methods development are also given towards the wide application of metallic BP PEMFCs.

关键词： Metallic bipolar plate Proton exchange membrane fuel cell Base material Coating material Processing method Mass application

Physicochemical analysis of individual atmospheric fine particles based on effective surface-enhanced Raman spectroscopy

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Journal of Environmental Sciences 2019年第1期31卷 388-395页

作者： Zhenli Sun Fengkui Duan Kebin He Jingjing Du Liu Yang Hui Li Tao Ma Shuo Yang state Key Joint Laboratory of Environment Simulation and Pollution Control School of Environment Tsinghua University state Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex Tsinghua University state Key Laboratory of Environmental Chemistry and Ecotoxicology Research Center for Eco-Environmental Sciences Chinese Academy of Sciences

Fine particles associated with haze pollution threaten the health of more than 400 million people in China. It is therefore of great importance to thoroughly investigate and understand their composition. To determine the physicochemical properties in atmospheric fine particles at the micrometer level, we described a sensitive and feasible surface-enhanced Raman scattering(SERS) method using Ag foil as a substrate. This novel method enhanced the Raman signal intensities up to 10,000 a.u. for ν(NO_3^-) in fine *** SERS effect of Ag foil was further studied experimentally and theoretically and found to have an enhancement factor of the order of ～10~4. Size-fractionated real particle samples with aerodynamic diameters of 0.4–2.5 μm were successfully collected on a heavy haze day,allowing ready observation of morphology and identification of chemical components, such as soot, nitrates, and sulfates. These results suggest that the Ag-foil-based SERS technique can be effectively used to determine the microscopic characteristics of individual fine particles, which will help to understand haze formation mechanisms and formulate governance policies.

关键词： SERS PM2.5 Individual particle Atmospheric

Stiffness of Postural Alignment System Based on 3-Axis Actuators for Large Aircraft Components

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Chinese Journal of Mechanical Engineering 2010年第4期23卷 524-531页

作者： GUO Zhimin JIANG Junxia KE Yinglin The state Key Lab of Fluid Power Transmission and Control Zhejiang university Hangzhou 310027 China

Aircraft digital flexible assembly fixture and technologies are widely used in developed countries, while the traditional jig-based assembly mode is still used in China. The application study of aircraft digital flexible assembly system is just beginning in our country recently. To meet the requirements of automated posture alignment and join in digital assembly system for large aircraft components, a novel fitting fixture called 3-axis actuator is developed. On the basis of the actuators, three kinds of posture alignment system for large aircraft components are proposed, including the non-redundant system, the redundant actuating system, and the redundant leg system, and their constitutions and properties are introduced. Through deriving the feeding transmission stiffness model of single actuator and analyzing the inverse kinematics of these systems, the relationship between the external force and the changes of position and orientation of large aircraft component is obtained, and then the postural alignment stiffness models are established. With the method mentioned above, the postural alignment stiffness of three systems is computed by using the algebraic formulate, and the results show that redundant properties can increase system＇s postural alignment stiffness. As an example, a optimized layout of the assembly system for a given model of aircraft is developed, the results of application show that the layout has many advantages, such as high accuracy, stiffness, stability, reliability, efficiency and flexible, which can satisfy the requirement of aircraft digital assembly system well. The proposed study of postural alignment stiffness for different systems can supply the theoretic support for the optimization layout design of aircraft digital assembly system, and contribute to evaluate the system working performance of systems.

关键词： 3-axis actuator large aircraft component redundant postural alignment stiffness posture-holding

Demonstrate chiral spin currents with nontrivial interactions in superconducting quantum circuit

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Chinese Physics B 2023年第4期32卷 587-592页

作者：喻祥敏邓翔徐建文郑文兰栋赵杰谭新生李邵雄于扬 National Laboratory of Solid state Microstructures School of PhysicsNanjing UniversityNanjing 210093China

Quantum many-body systems in which time-reversal symmetry is broken give rise to a wealth of exotic phases,and thus constitute one of the frontiers of modern condensed matter *** simulation allows us to better understand many-body systems with huge Hilbert space,where classical simulation is usually *** superconducting quantum circuit as a platform for quantum simulation,we realize synthetic Abelian gauge fields by using microwave drive and tunable coupling in loop configurations to break the time-reversal symmetry of the *** on high-precision manipulation and readout of circuit-QED architecture,we demonstrate the chiral ground spin current of a time-reversal symmetry broken system with nontrivial *** work is a significant attempt to simulate quantum many-body systems with time-reversal symmetry breaking in multi-qubit superconducting processors.

关键词： superconducting qubit time-reversal symmetry breaking chirality

Simulation and Experiment Research on the Proportional Pressure Control of Water-assisted Injection Molding

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Chinese Journal of Mechanical Engineering 2012年第3期25卷 430-438页

作者： ZHOU Hua CHEN Yinglong ZHANG Zengmeng YANG Huayong The state Key Lab of Fluid Power Transmission and Control Zhejiang UniversityHangzhou 310027China

Water-assisted injection molding（WAIM）,a newly developed fluid-assisted injection molding technology has drawn more and more attentions for the energy saving,short cooling circle time and high quality of *** research for the process of WAIM has shown that the pressure control of the injecting water is mostly important for the ***,the proportional pressure control for the WAIM system is quite complex due to the existence of nonlinearities in the water hydraulic *** order to achieve better pressure control performance of the injecting water to meet the requirements of the WAIM,the proportional pressure control of the WAIM system is investigated both numerically and experimentally.A newly designed water hydraulic system for WAIM is first modeled in AMEsim environment,the load characteristics and the nonlinearities of water hydraulic system are both considered,then the main factors affecting the injecting pressure and load flow rate are extensively ***,an open-loop model-based compensation control strategy is employed to regulate the water injection pressure and a feedback proportional integrator controller is further adopted to achieve better control *** order to verify the AMEsim simulation results WAIM experiment for particular Acrylonitrile Butadiene Styrene（ABS） parts is implemented and the measured experimental data including injecting pressure and flow rate results are compared with the *** good coincidence between experiment and simulation shows that the AMEsim model is accurate,and the tracking performance of the load pressure indicates that the proposed control strategy is effective for the proportional pressure control of the nonlinear WAIM *** proposed proportional pressure control strategy and the conclusions drawn from simulation and experiment contribute to the application of water hydraulic proportional control and WAIM technology.

关键词： water-assisted injection molding nonlinear modeling proportional pressure control AMEsim simulation

Orientation and alignment during materials processing under high magnetic fields

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Chinese Physics B 2019年第4期28卷 1-6页

作者： Zhong-Ming Ren Jiang Wang Rui-Xin Zhao state Key Laboratory of Advanced Special Steel & Shanghai Key Laboratory of Ferrometallurgy Shanghai University

The characteristics of lattice structures can make crystal possess distinct anisotropic features, such as the varying magnetism in different crystal orientations and different directions. The anisotropic magnetism can also cause the free energy to vary in different orientations of crystal in a magnetic field(magnetic anisotropy energy). Magneto-anisotropy can make the crystal rotate by the magnetic force moment on the crystal with the easy axis towards the direction of the magnetic field, and can also promote the preferential growth along a certain crystal direction at the lowest energy *** solidification, vapor-deposition, heat treatment, slip casting and electrodeposition under magnetic field, the crystal structure with high grain orientation is obtained in a variety of binary eutectics, peritectic alloys, multicomponent alloys and high temperature superconducting materials. This makes it possible to fabricate texture-functional material by using high magnetic field and magneto-crystalline anisotropy of crystal. The purpose of this article is to review some recent progress of the orientation and alignment in material processing under a high magnetic field.

关键词： high magnetic field orientation alignment

STUDY ON THE ANGLE OF REPOSE OF NONUNIFORM SEDIMENT

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Journal of Hydrodynamics 2009年第5期21卷 685-691页

作者： YANG Feng-guang LIU Xing-nian YANG Ke-jun CAO Shu-you state Key Laboratory of Hydraulics and Mountain River Engineering Sichuan University Chengdu 610065China

A conception of exposure degree is used in this article to account for the hiding and exposure mechanism of nonuniform sediment transport. The force arms of particles on the bed slope are assumed to be a function of the exposure degree, which is stochastically related to the size and gradation of bed materials. Based on this conception, the formula for the angle of repose of nonuniform sediment is developed. The angle of repose of nonuniform sediment is experimentally investigated in rotation drum at the rolling motion of sediment particles. The nonuniform sediment is gotten from the mixture of two kinds of uniform sediment with different weight ratios and two experimental plans that one for changing the weight ratio of two kinds of uniform sediment from 1：9 to 9：1 and the other changing the uniform sediment size and weight ratio are used. The effect of the rotation speed and the filling degree on the angle of repose is investigated, too. Finally, the formula has been tested against a wide range of laboratory data, the prediction by the newly proposed formulas is very good.

关键词： the angle of repose nonuniform sediment rotation drum exposure degree

p-Sulfonatocalix[4]arene-induced amphiphilic aggregation of fluorocarbon surfactant

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Science China Chemistry 2014年第3期57卷 371-378页

作者： CAO Yu WANG YiXuan GUO DongSheng LIU Yu state Key Laboratory of Elemento-Organic Chemistry Department of Chemistry Nankai University

Sulfonatocalix[4]arene lowers the critical aggregation concentration of fluorocarbon surfactant pronouncedly by a factor of ca.100 to form binary amphiphilic aggregates on the basis of host-guest complexation,which was identified by1H NMR spectroscopy,fluorescence spectroscopy,optical transmittance spectroscopy,dynamic laser scattering,high-resolution transmission electron microscopy,scanning electron microscopy,and surface tension ***,the resulting aggregates can respond to external stimuli,including temperature and inclusion of competitor ***,the present system may have potential applications in drug delivery systems.

关键词： calixarene-induced aggregates fluorocarbon surfactant supra-amphiphile multi-stimuli responses

Upper Bound Solution of the Resisting Moment Bearing Capacity of A Composite Bucket Shallow Foundation of An Offshore Wind Turbine in Sand

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China Ocean Engineering 2022年第6期36卷 859-870页

作者： LIU Run LI Tian-liang CHEN Guang-si LIAN Ji-jian state Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China

Bearing the large moment that is generated by the wind load that acts on the upper structure of offshore wind turbines is an important feature of their foundations that is different from other offshore structures.A composite bucket shallow foundation(CBSF)has been proposed by Tianjin university to address the soft geological conditions in the offshore regions of China for wind *** CBSF is a new type of foundation and is effective against large *** soil deformation test of a CBSF and the numerical simulation study under the same working conditions are carried out to determine the failure mechanism of a CBSF under moment *** resisting soil compression rateηm is defined as a new empirical parameter that indicates the ability of the soil inside the bucket to resist moment *** upper limit of the resisting moment bearing capacity of the bucket foundation is derived through the upper bound theorem of classical plasticity theory based on the failure *** calculation method is validated by tests of bucket models with different height-diameter ratios in sand under moment loading.

关键词： bucket foundation failure mechanism resisting moment bearing capacity upper bound theorem resisting soil compression rate