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Ripple-based matrix modeling and cross-coupling effect analysis of double-input DC-DC Boost converters

Science China(Technological Sciences) 2022年第8期65卷 1878-1890页

作者： zhang hao REN Han YI ChuanZhi DONG DaChu State Key Lab of Electrical Insulation&Power Equipment School of Electrical EngineeringXi’an Jiaotong UniversityXi’an 710049China Bosch Automotive Product(Suzhou)Co.Ltd Suzhou 215000China Hangzhou Power Supply Company of State Grid Zhejiang Electric Power Co.Ltd Hangzhou 310000China

This paper deals with the modeling and cross-coupling effect analysis in double-input Boost converters with multiplex current control. A ripple-based multiplex current controlled matrix model is proposed to restore the system's high-frequency domain dynamics information and resolve the coexistence problem of the sample-and-hold effect in multiplex current controllers, which significantly improves the resolution of the conventional average model. Based on the proposed model, both sub-harmonic and low-frequency oscillations are identified in terms of stability analysis, and the inherent mechanism of these complicated nonlinear dynamic behavior is revealed, which not only illustrates the origin of the oscillations but also points out the dominant factors in diverse types of instability situation. Besides, cross-coupling effect analysis is performed to study the interaction between the input ports with the help of the Gershgorin band, and the mechanism of the special unbalanced oscillation phenomenon is revealed. Furthermore, the sensitivity analysis approach is used to identify the key parameters with respect to the cross-coupling effect, which provides more design-oriented knowledge for practical engineering. In addition, the benefits of the proposed model are further illustrated through a comparative analysis. Finally, these theoretical results are verified by experimental ones. These results are beneficial to the improvement of performance as well as the understanding of the cross-coupling effect of multi-input converters.

关键词： ripple-based matrix model cross-coupling effect multiplex current control multi-input converter Gershgorin band

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Experimental Investigation of Dimensionless Velocity and Shearing Stress in Boundary Layer Flow on Continuous Moving Surface in Power Law Fluids

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Journal of Thermal Science 2011年第2期20卷 115-118页

作者： hao zhang Xinxin zhang Liancun Zheng Weiliang Wang Yuancheng Wang Key Laboratory of Renewable Energy Utilization Technologies in Buildings Ministry of Education Jinan 250101China Shandong Key Laboratory of Building Energy-saving Technique Shandong Jianzhu University Jinan 250101 China School of Thermal Energy Engineering Shandong Jianzhu University Jinan 250101 China Department of Thermal Engineering University of Science and Technology Beijing Beijing 100083 China Department of Mathematics and Mechanics University of Science and Technology Beijing Beijing 100083 China College of Population Resources and Environment Shandong Normal University Jinan 250014 China

An analysis is carried out to study the steady flow characteristics from a continuous flat surface moving in a parallel free stream of non-Newtonian power law fluid. The constitutive equations of the fluid are transformed into dimensionless ones. The velocity field is measured by Particle Image Velocimetry. Experimental results are obtained for the distribution of velocity. The influence of wall velocity ratio parameter on boundary layer flow field is observed in the experiment. Dimensionless velocity distribution and shearing stress distribution are obtained by post-processing experimental results. The effects of various physical parameters like velocity ratio parameter and similarity variable on various momentum transfer characteristics are discussed in detail and shown graphically. It is indicated that dimensionless velocity increases with velocity ratio parameter and similarity variable, and that dimensionless shearing stress decreases with velocity ratio parameter and similarity variable.

关键词： Boundary layer Power law fluid PIV Experiment Dimensionless transformation

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Synthesis and analysis of new humidity-controlling composite materials

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International Journal of Minerals,Metallurgy and Materials 2017年第5期24卷 594-602页

作者： Jian-li Shang Zhi-fang Zong hao zhang College of Materials and Mineral Resources Xi’an University of Architecture and TechnologyXi’an 710055China

Gypsum is a traditional building material. To improve the humidity-controlling properties of gypsum, we prepared a new type of humidity-controlling composite using the sol-gel method. Methods to determine the maximum equilibrium moisture content and speed of adsorption/desorption were subsequently applied to analyze the performance of the samples. The appearance and structural properties of the samples were characterized by scanning electronic microscopy (SEM). The experimental results show that the humidity-controlling gel with added LiCl exhibits high moisture storage and that the equilibrium maximum moisture content is 5.652 g/g at a 75.29% relative humidity (RH). A mass ratio of LiCl/sol = 0.15 is demonstrated to be appropriate for the preparation of the new humidity-controlling composites. A coarse network with tiny pores is observed on the surface of the new humidity-controlling composites, and this pore network provides sufficient space for moisture adsorption.

关键词： composite materials gypsum humidity control sol-gel processing adsorption desorption

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Experimental investigation on unstart-restart hysteresis of a supersonic inlet during throat regulation

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Chinese Journal of Aeronautics 2023年第11期36卷 135-152页

作者： Yi JIN Huijun TAN hao zhang Gaojie ZHENG Shu SUN Yue zhang Jiangsu Province Key Laboratory of Aerospace Power System College of Energy and Power EngineeringNanjing University of Aeronautics and AstronauticsNanjing 210016China Aerospace Times Feipeng Company Limited China Academy of Aerospace Electronics TechnologyKunshan 215000China

The hysteresis during the throat regulation process of a supersonic variable inlet is unconducive to ***,detailed experimental studies of such a hysteresis and its control are necessary.A throat variable supersonic inlet was designed at a shock-on-lip Mach number of 4.0 and an Internal Contraction Ratio(ICR)ranging over 1.21–***,a distributed bleed system was proposed to suppress the *** wind tunnel tests were conducted at Mach number *** throat regulation processes were recorded using a high-speed schlieren and dynamic pressure acquisition *** results indicate that the unstart and restart ICRs during the uncontrolled inlet’s throat regulation process were 1.95 and 1.48,respectively,demonstrating an unstart-restart *** typical flowfields were summarized during the uncontrolled inlet’s restart *** proposed bleed control increased the unstart and restart ICRs to 2.06 and 1.75,respectively,and the inlet realized the designed state as the ICR was further decreased to *** controlled inlet’s hysteresis loop was decreased compared to the uncontrolled ***,the mechanism of the hysteresis,dominated by the entrance separation-induced wave system,was *** mechanisms of the bleed control to broaden the unstart and restart boundaries and suppress the hysteresis were elucidated.

关键词： Supersonic inlet Unstart-restart hysteresis Bleed control Throat regulation process Wind tunnel test

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Promoting the mechanical properties of Ti42Al9V0.3Y alloy by hot extrusion in the α+β phase region

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2010年第10期11卷 738-743页

作者： Wen-chen XU hao zhang De-bin SHAN Department of Materials Science and Engineering Harbin Institute of Technology Harbin 150001 China

Hot extrusion was conducted in the α+β phase region for promoting mechanical properties of Ti42Al9V0.3Y. The microstructures and tensile properties before and after hot extrusion were studied. The results show that the microstructure of the as-cast alloy mainly consists of massive γ phase in β matrix and the as-extruded alloy mainly consists of lamellar α2/γ, lamellar β/γ, and strip γ propagating from elongated β phase. In the as-cast alloy, the predominantly observed fracture mode is transgranular cleavage failure at room temperature and intergranular fracture at 650-750 °C. After hot extrusion, it transforms into transgranular cleavage-like failure, including translamellar cleavage and delamination. The excellent tensile properties of the as-extruded material are attributed to the obvious refined microstructure with broken YAl2 particles and the micro-crack shielding action of the TiAl lamellasome.

关键词： TiAl alloy Microstructure Mechanical property Hot extrusion

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Discernible image mosaic with edge-aware adaptive tiles

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Computational Visual Media 2019年第1期5卷 45-58页

作者： Pengfei Xu Jianqiang Ding hao zhang Hui Huang College of Computer Science and Software Engineering Shenzhen University School of Computing Science Simon Fraser University

We present a novel method to produce discernible image mosaics, with relatively large image tiles replaced by images drawn from a database, to resemble a target image. Compared to existing works on image mosaics, the novelty of our method is ***, believing that the presence of visual edges in the final image mosaic strongly supports image perception,we develop an edge-aware photo retrieval scheme which emphasizes the preservation of visual edges in the target image. Secondly, unlike most previous works which apply a pre-determined partition to an input image, our image mosaics are composed of adaptive tiles, whose sizes are determined based on the available images in the database and the objective of maximizing resemblance to the target image. We show discernible image mosaics obtained by our method, using image collections of only moderate size. To evaluate our method, we conducted a user study to validate that the image mosaics generated present both globally and locally appropriate visual impressions to the human observers. Visual comparisons with existing techniques demonstrate the superiority of our method in terms of mosaic quality and perceptibility.

关键词： image mosaic image retrieval image synthesis

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Multi-constrained intelligent gliding guidance via optimal control and DQN

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Science China(Information Sciences) 2023年第3期66卷 214-229页

作者： Jianwen ZHU hao zhang Sibo Zhao Weimin BAO School of Aerospace Science and Technology Xidian University China Aerospace Science and Technology Corporation

In order to improve the adaptability and robustness of gliding guidance under complex environments and multiple constraints, this study proposes an intelligent gliding guidance strategy based on the optimal guidance, predictor-corrector technique, and deep reinforcement learning(DRL). Longitudinal optimal guidance was introduced to satisfy the altitude and velocity inclination constraints, and lateral maneuvering was used to control the terminal velocity magnitude and position. The maneuvering amplitude was calculated by the analytical prediction of the terminal velocity, and the direction was learned and determined by the deep Q-learning network(DQN). In the direction decision model construction, the state and action spaces were designed based on the flight status and maneuvering direction, and a reward function was proposed using the terminal predicted state and terminal constraints. For DQN training, initial data samples were generated based on the heading-error corridor, and the experience replay pool was managed according to the terminal guidance error. The simulation results show that the intelligent gliding guidance strategy can satisfy various terminal constraints with high precision and ensure adaptability and robustness under large deviations.

关键词： gliding flight optimal guidance velocity control deep reinforcement learning intelligent decision

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Heat Treatment Effect on Microstructure, Hardness and Wear Resistance of Cr26 White Cast Iron

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Chinese Journal of Mechanical Engineering 2015年第1期28卷 140-147页

作者： ZHOU Shaoping SHEN Yehui zhang hao CHEN Dequan Key Laboratory of Pressure Systems and Safety of Ministry of Education East China University of Science and Technology Shanghai First Fluid Machinery Co.Ltd

High chromium cast iron（HCCI） is taken as material of coal water slurry pump impeller, but it is susceptible to produce serious abrasive wear and erosion wear because of souring of hard coal particles. The research on optimization of heat treatments to improve abrasive wear properties of HCCI is insufficient, so effect of heat treatments on the microstructure, hardness, toughness, and wear resistance of Cr26 HCCI is investigated to determine the optimal heat treatment process for HCCI. A series of heat treatments are employed. The microstructures of HCCI specimens are examined by using optical microscopy and scanning electron microscopy. The hardness and impact fracture toughness of as-cast and heat treated specimens are measured. The wear tests are assessed by a Type M200 ring-on block wear tester. The results show the following： With increase of the quenching temperature from 950 ℃ to 1050 ℃, the hardness of Cr26 HCCI increased to a certain value, kept for a time and then decreased. The optimal heat treatment process is 2 h quenching treatment at 1000 ℃, followed by a subsequent 2 h tempering at 400 ℃. The hardness of HCCI is related to the precipitation and redissolution of secondary carbides in the process of heat treatment. The subsequent tempering treatment would result in a slight decrease of hardness but increase of toughness. The wear resistance is much related to the ＂supporting＂ effect of the matrix and the ＂protective＂ effect of the hard carbide embedded in the matrix, and the wear resistance is further dependent on the hardness and the toughness of the matrix. This research can provide an important insight on developing an optimized heat treatment method to improve the wear resistance of HCCI.

关键词： Cr26 white cast iron heat treatment microstructure hardness wear resistance

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NLOS Identification and Machine Learning Methods for Predicting the Outcome of 60GHz Ranging System

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Chinese Journal of Electronics 2018年第1期27卷 175-182页

作者： LIANG Xiaolin JIN Yiheng zhang hao LYU Tingting College of Information Science and Engineering Ocean University of China Department of Electrical Computer Engineering University of Victoria

Millimeter-wave(MMW) signals in 60 GHz band have shown immense potential for accurate range estimation with precise time and multipath resolution. Nonline of sight(NLOS) propagation is a primary factor affecting the range precision. To improve range estimation,an Energy detector(ED) based normalized threshold algorithm which employs a Neural network(NN) is developed on the basis of NLOS identification. The maximum curl and standard deviation of the received energy block values are used to determine NLOS environment and the normalized thresholds for different Signal-to-noise ratios(SNRs). The effects of the channel and integration period are *** results are presented which show that the proposed approach provides better precision and is more robust than other solutions over a wide range of SNRs for the CM1.1 and CM2.1 channel models in the IEEE802.15.3 c standard.

关键词： Non-line of sight(NLOS) identification Curl Standard deviation IEEE 802.15.3c Machine learning

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Investigation of multinucleon transfer processes in the Langevin equation model

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Nuclear Science and Techniques 2024年第10期35卷 180-187页

作者： Ying Zou Ming-hao zhang Mei-Chen Wang Yu-Hai zhang Feng-Shou zhang The Key Laboratory of Beam Technology of Ministry of Education School of Physics and AstronomyBeijing Normal UniversityBeijing 100875China Institute of Radiation Technology Beijing Academy of Science and TechnologyBeijing 100875China Center of Theoretical Nuclear Physics National Laboratory of Heavy Ion Accelerator of LanzhouLanzhou 730000China

Multinucleon transfer in low-energy heavy-ion collisions is increasingly considered a promising approach for generating exotic *** the complex mechanisms involved in multinucleon transfer processes presents significant challenges for the theoretical investigation of nuclear reactions.A Langevin equation model was developed and employed to investigate multinucleon transfer ***^(40)Ar+^(232)Th reaction was simulated,and the calculated Wilczyński plot was used to verify the ***,to study the dynamics of multinucleon transfer reactions,the^(136)Xe+^(238)U and^(136)Xe+^(209)Bi reactions were simulated,and the corresponding TKE-mass and angular distributions were computed to analyze the energy dissipation and scattering *** investigation enhances our understanding of the dynamics involved in multinucleon transfer processes.

关键词： Reaction mechanisms Multinucleon transfer reactions Langevin equations Wilczyński plot Exotic nuclei

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