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Oblique detonation wave triggered by a double wedge in hypersonic flow

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Chinese Journal of Aeronautics 2022年第4期35卷 176-184页

作者： Honghui TENG yuhang zhang Pengfei YANG Zonglin JIANG School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China State Key Laboratory of High Temperature Gas Dynamics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Sciences University of Chinese Academy of SciencesBeijing 100049China

Pressure-gain combustion has gained attention for airbreathing ramjet engine applications owing to its better thermodynamic efficiency and fuel consumption rate. In contrast with traditional detonation induced by a single wedge, the present study considers oblique shock interactions attached to double wedges in a hypersonic combustible flow. The temperature/pressure increases sharply across the interaction zone that initiates an exothermic reaction, finally resulting in an Oblique Detonation Wave(ODW). Compared with the case for a single-wedge ODW, the double-wedge geometry has great potential to control the initiation of the ODW. As a tentative study, two-dimensional compressible Euler equations with a two-step induction-reaction kinetic model are used to solve the detonation dynamics triggered by a double wedge. The effects of the wedge angles and wedge corner locations on the initiation structures are investigated *** results show an ODW complex comprising three Oblique Shock Waves(OSWs), an induction zone, a curved detonation front, and an unburned/low-temperature gas belt close to the surface of the second wedge. Both the increasing wedge angle and downstream wedge corner location lead to an abrupt OSW–ODW transition type, whereas the former corresponds to the shock–shock interaction and the later has a greater effect on the exothermic chemical process. Analysis of the shock polar and flow scale confirms that the OSW–ODW initiation structure mainly depends on the coupling of shocks and heat release in a confined initiation zone.

关键词： Double wedge Hypersonic flow Initiation structures Oblique detonation Shock interactions

A hybrid model for high spatial and temporal resolution population distribution prediction

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International Journal of Digital Earth 2022年第1期15卷 2268-2295页

作者： yuhang zhang Yi zhang Bo Huang Xin Liu Tsinghua-Berkeley Shenzhen Institute Tsinghua UniversityShenzhenPeople’s Republic of China Institute of Future Human Habitats Tsinghua Shenzhen International Graduate SchoolTsinghua UniversityShenzhenPeople’s Republic of China Department of Geography and Resource Management The Chinese University of Hong KongShatinHong KongPeople's Republic of China Huawei Technologies Co. Ltd.ShenzhenPeople’s Republic of China

The accurate prediction of population distribution is crucial for numerous applications,from urban planning to epidemiological *** one-week data collected from open and multiple sources,including telecommunication activity,weather,point of interest,buildings,roads,and land use in Milan,Italy,we develop a hybrid method combining cellular automata(CA)and long short-term memory(LSTM)to predict population distribution with fine temporal and spatial ***,the convolutional autoencoder and LightGBM are applied to identify missing building types based on the pedestrian *** LSTM learns the transition rules of CA and Shapley additive explanations value is used for variable importance *** demonstrate that the combination of convolutional autoencoder and LightGBM is effective in building type *** proposed model for population distribution prediction outperforms LSTM,the combination of CA and neural network,and the combination of CA and LightGBM by at least 5–10%.A variable importance analysis reveals that temporal variables are the most significant for prediction,followed by spatial and natural *** order of hour,housing-related variables,and types of precipitation are the most important variables in each category.

关键词： Cellular automata long short-term memory spatial and temporal analysis big data population distribution

The study of lithographic variation in resistive random access memory

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Journal of Semiconductors 2024年第5期45卷 69-79页

作者： yuhang zhang Guanghui He Feng zhang Yongfu Li Guoxing Wang Department of Micro-Nano Electronics Shanghai Jiao Tong UniversityShanghai 200240China MoE Key Lab of Artificial Intelligence Shanghai Jiao Tong UniversityShanghai 200240China Institute of Microelectronics Chinese Academy of SciencesBeijing 100029China

Reducing the process variation is a significant concern for resistive random access memory(RRAM).Due to its ultrahigh integration density,RRAM arrays are prone to lithographic variation during the lithography process,introducing electrical variation among different RRAM *** this work,an optical physical verification methodology for the RRAM array is developed,and the effects of different layout parameters on important electrical characteristics are systematically *** results indicate that the RRAM devices can be categorized into three clusters according to their locations and lithography *** read resistance is more sensitive to the locations in the array(~30%)than SET/RESET voltage(<10%).The increase in the RRAM device length and the application of the optical proximity correction technique can help to reduce the variation to less than 10%,whereas it reduces RRAM read resistance by 4×,resulting in a higher power and area *** such,we provide design guidelines to minimize the electrical variation of RRAM arrays due to the lithography process.

关键词： layout lithography process variation resistive random access memory

Erosion wear experiments and simulation analysis on bionic anti-erosion sample

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Science China(Technological Sciences) 2014年第3期57卷 646-650页

作者： zhang yuhang HUANG He REN LuQuan Key Laboratory of Bionic Engineering (Ministry of Education) Jilin University

The dorsal surface of a desert lizard has excellent particle erosion *** this paper,a bio-inspired sample was designed and fabricated based on the biological characteristics of the dorsal skin of the desert lizard(Laudakin stoliczkana).The bionic sample consists of two materials with different characteristics,which form a two-layer composite *** particle erosion property and erosion wear mechanism of the bionic sample was studied by means of sandblast experiment and numerical simulation,*** experimental results show that,in the stage with steady abrasion rate,the weight loss per unit time of the bionic sample is about 10%lesser than the control *** numerical simulation indicated that the two-layer structure of the bionic sample can efficiently absorb the normal stress,and dissipate the stress in the horizontal ***,the stress concentration on the sample surface is *** two-layer structure is contributed to the decentralizing of the stress distribution,and thus the occurrence probability of erosion damage can be decreased.

关键词： bionics particle erosion sandblast desert lizard numerical simulation

Ferromagnetism and insulating behavior with a logarithmic temperature dependence of resistivity in Pb_(10-x)Cux(PO_(4))_(6)O

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Science China(Physics,Mechanics & Astronomy) 2024年第1期67卷 106-111页

作者： yuhang zhang Cong Liu Xiyu Zhu Hai-Hu Wen Center for Superconducting Physics and Materials National Laboratory of Solid State Microstructures and Department of PhysicsNational Collaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjing 210093China

Recent claim of discovering above-room-temperature superconductivity(Tc≈400 K)at ambient pressure in copper doped apatite Pb10(PO_(4))_(6)O has stimulated world-wide enthusiasm and impulse of motion.A lot of follow-up works have been carried out with controversial *** check whether superconductivity is really present or absent in the material,we need samples which should have a rather pure phase of Pb_(10-x)Cux(PO_(4))_(6)*** we report the characterization results from the Pb_(10-x)Cux(PO_(4))_(6)O with a fraction of about 97 wt.%inferred from the fitting to the X-ray diffraction pattern,if assuming Cu2S as the only *** resistivity measurements show that it is a semiconductor characterized roughly by a ln(1/T)temperature dependence in wide temperature region without trace of *** measurements show that it has a general ferromagnetic signal with a weak superparamagnetic *** grains of the sample show clear interactions with a Nb Fe B *** detected Cu concentration is much lower than the expected nominal *** results show the absence of metallicity and superconductivity in Pb_(10-x)Cux(PO_(4))_(6)O at ambient pressure,and suggest the presence of strong correlation effect.

关键词： superconductivity Pb10(PO4)6O ferromagnetic correlation effect

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A novel predictive braking energy recovery strategy for electric vehicles considering motor thermal protection

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Science China(Technological Sciences) 2024年第4期67卷 1253-1269页

作者： YANG Chao SUN TongLin YANG LiuQuan zhang yuhang WANG WeiDa School of Mechanical Engineering Beijing Institute of TechnologyBeijing 100084China

Braking energy recovery(BER)aims to recover the vehicle's kinetic energy by coordinating the motor and mechanical braking torque to extend the driving range of the electric vehicle(EV).To achieve this goal,the motor/generator mode requires frequent switching and prolonged operation during *** this case,the motor temperature will unavoidably rise,potentially triggering motor thermal protection(MTP).Activating MTP increases the risk of motor component failure,and the EV typically disables the BER ***,maximizing BER while reducing the risk of motor overheating is a challenging *** address this issue,this article proposes a predictive BER strategy with MTP using the non-smooth Pontryagin Minimum Principle(NSPMP)for ***,a Markov long short-term memory(MLSTM)model is designed to obtain future velocity ***,the BER problem with MTP in the studied EV is embedded in a model predictive control(MPC)***,under the MPC framework,the NSPMP strategy is proposed to resolve the problem of ***,the performance of the proposed strategy is verified through simulation and a hardware-in-loop *** results show that in two real-world driving cycles,compared to the rule-based strategy,the proposed strategy reduced power consumption by 1.24%and0.96%,respectively,and effectively limited motor ***,under global cycle conditions,this strategy demonstrated better MTP control performance compared to other benchmark strategies.

关键词： electric vehicle braking energy recovery strategy motor thermal protection non-smooth PMP

Mechanics and Wave Propagation Characterization of Chiral S-Shaped Auxetic Metastructure

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Acta Mechanica Solida Sinica 2022年第4期35卷 571-586页

作者： Qingsong zhang Wenjie Hong Jianfei Xu yuhang zhang Suhang Ding Wenwang Wu Re Xia Key Laboratory of Hydraulic Machinery Transients(Wuhan University) Ministry of EducationWuhan430072China School of Naval Architecture Ocean and Civil EngineeringShanghai Jiao Tong UniversityShanghai200240China Institute of Advanced Structure Technology Beijing Institute of TechnologyBeijing100081China Hubei Key Laboratory of Waterjet Theory and New Technology Wuhan UniversityWuhan430072China

Auxetic metastructures have attracted tremendous attention because of their robust multifunctional properties and promising potential industrial *** paper studies the in-plane mechanical behaviors of a chiral S-shaped metastructure subjected to tensile loading in both X-direction and Y-direction and wave propagation properties using the finite element(FE)*** relationships between structural parameters and elastic behaviors are also *** results indicate that the orientation of chiral S-shaped metastructure under tensile loading in the X-direction exhibits higher auxeticity and ***,the band structures and the edge modes of each band gap of the chiral S-shaped metastructure are explored,and the relations between band gap properties and structural parameters are also systematically ***,we explore the wave mitigation of the chiral S-shaped metastructures by regulating the structural ***,the transmission properties of the finite chiral S-shaped periodic metastructures are studied to confirm the results of band gap *** study promotes the engineering application of vibration isolation of chiral structures based on the band gap theory.

关键词： Auxetic metastructures Mechanical properties Band gaps Wave mitigation

Model-Based Double Closed-Loop Coordinated Control Strategy for the Electro-Mechanical Transmission System of Heavy Power-Split HEVs

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Automotive Innovation 2021年第1期4卷 44-55页

作者： Weida Wang yuhang zhang Xiaoxia Sun Changle Xiang Chao Yang School of Mechanical Engineering Beijing Institute of TechnologyBeijing 100081China Beijing Institute of Technology Chongqing Innovation Center Chongqing 401120China China North Vehicle Research Institute Beijing 100072China

The dual-mode electro-mechanical transmission(EMT)system is a crucial part of power-split hybrid electric vehicles(HEVs),especially for the heavy *** improve the precision of the system power distribution and the response speed of the electric power supply,a model-based double closed-loop coordinated control strategy is *** the basis of the proposed control strategy,an EMT system model,particularly of an electrical system,is established *** proposed control strategy includes the power distribution strategy,battery power closed-loop feedback control strategy,and motor coordinated control *** verify the feasibility of the proposed control strategy,simulation and experiment are *** results indicate that the proposed control strategy can realize the expected power distribution by coordinating generators and motors and achieve rapid and stable electric power supply.

关键词： Hybrid electric vehicles Electro-mechanical transmission system Hybrid power-split Power coordinated control Multi-power distribution

Selective oxidation of propane to acrylic acid over mixed metal oxide catalysts

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Journal of Natural Gas Chemistry 2008年第2期17卷 191-194页

作者： Wei Zheng Zhenxing Yu Ping zhang yuhang zhang Hongying Fu Xiaoli zhang Qiquan Sun Xinguo Hu School of Municipal and Environmental Engineering Harbin Institute of Technology Harbin 150001 Heilongjiang China Daqing Petroleum Co Ltd Daqing 163453 Heilongjiang China

The effects of metal atomic ratio, water content, oxygen content, and calcination temperature on the catalytic performances of MoVTeNbO mixed oxide catalyst system for the selective oxidation of propane to acrylic acid have been investigated and discussed. Among the catalysts studied, it was found that the MoVTeNbO catalyst calcined at a temperature of 600 ℃ showed the best performance in terms of propane conversion and selectivity for acrylic acid under an atmosphere of nitrogen. An effective MoVTeNbO oxide catalyst for propane selective oxidation to acrylic acid was obtained with a combination of a preferred metal atomic ratio （Mo1V0.31Te0.23Nb0.12）. The optimum reaction condition for the selective oxidation of propane was the molar ratio of C3H8 ：O2 ： H2O ： N2 = 4.4： 12.8 ： 15.3 ： 36.9. Under such conditions, the conversion of propane and the maximum yield of acrylic acid reached about 50% and 21%, respectively.

关键词： propane oxidation catalysts preparation acrylic acid selective oxidation