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IEEE Conference on Vehicular technology (VTC)

作者： Lijun Yang Haitao Lu Xinchao Ge Zhixin Sun Pan Cao School of Internet of Things Nanjing University of Posts and Telecommunications Nanjing China RAN System Design Dept. ZTE Corporation Shenzhen China Shenzhen Key Laboratory of 5G RAN Security Technology Research and Application Shenzhen China School of Modern Posts Nanjing University of Posts and Telecommunications Nanjing China School of Physics Engineering and Computer Science University of Hertfordshire Hatfield UK

A better understanding of the mmWave channel coherence time will play a significant role in both communication and sensing. Traditional literatures consider that the channel coherence time in mmWave communication will be very short due to high frequency, which makes the channel estimation more difficult. However, we believe that the propagation characteristics of the mmWave channel will affect its coherence time, i.e., channel sparsity may limit its time variability. In this paper, we investigate the time-varying nature of mmWave channel by analyzing its Doppler spread based on the clustered sparsity model. After the derivation of Doppler spectrum DPS and the simulation analysis based on the two-cluster channel, we found that the maximum angle between clusters and the power distribution between clusters are two main factors limiting the Doppler spread. Finally, the realistic mmWave NYUSIM model is used for Doppler spread comparative analysis with Clarke’s model and find that Doppler spread of NYUSIM channel is far less than that estimated based on Clarke’s model. Thus, it is demonstrated that even if the mmWave frequency is high, the clustered sparsity characteristics makes its channel coherence time not as short as thought intuitively, which is meaningful for mmWave vehicular sensing and communication.

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DC-Side Decoupling Method of DC-link Capacitor Reduction for Single Phase PWM Rectifier

DC-Side Decoupling Method of DC-link Capacitor Reduction for...

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Sustainable Power and Energy Conference (iSPEC)

作者： Jinxin Wang Peng Renyong Kailei Dai Zhiqiang Zhang Ting Zhang Junjie Zhao Qian Chen Jianjian Zhang Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu China Nuclear Power Institute of China Chengdu China

ISBN: (数字)9781728191645

ISBN: (纸本)9781728191652

The integrated charging system of Electric vehicle consists of a single-phase PWM rectifier and a Buck converter. When the single-phase PWM rectifier works with unit power factor, the dc-link voltage contains a large voltage harmonic of twice the grid frequency. Although the output voltage ripple can be controlled within the required range using the proper control of the Buck converter, the second-order harmonic on the dc-link capacitor is inevitable. This paper proposes a de-side decoupling method for the second-order harmonic problem of the dc-link voltage of the integrated charging system. A de-side decoupling half bridge is connected in parallel to absorb the ripple power of twice the grid frequency. This paper analyzes the operating principle of the de-side decoupling half bridge. Based on a theoretical analysis of the topology and the design procedure for controlling system, the proposed converter is designed and simulated. Finally, simulation results are given to verify the method.

关键词： Capacitors Rectifiers Bridge circuits Pulse width modulation Harmonic analysis Control systems Voltage control

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Anomalous Polarization-Switching Phenomena and Noteworthy Pyroelectricity in Ferroelectric Hf0.5zr0.5o2 Polycrystalline Films

SSRN

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SSRN 2023年

作者： Wang, Xudong Zhou, Yong Xiong, Ke Wu, Shuyu Tu, Luqi Chen, Yan Wu, Shuaiqin Zeng, Jinhua Zheng, Yuqing Gu, Shiqun Luo, Man Lin, Tie Shen, Hong Meng, Xiangjian Liu, Qi Chu, Junhao Wang, Jianlu State Key Laboratory of Infrared Physics Shanghai Institute of Technical Physics Chinese Academy of Sciences Shanghai200083 China Key Laboratory of Microelectronics Device and Integrated Technology Institute of Microelectronics Chinese Academy of Sciences Beijing100029 China Frontier Institute of Chip and System Fudan University Shanghai200433 China Shanghai Frontier Base of Intelligent Optoelectronics and Perception Institute of Optoelectronics Fudan University Shanghai200433 China Hangzhou Institute for Advanced Study University of Chinese Academy of Sciences Chinese Academy of Sciences Hangzhou330106 China BirenTech Shanghai201114 China Jiangsu Key Laboratory of ASIC Design School of Information Science and Technology Nantong University Jiangsu Nantong226019 China

Hafnia-based oxide thin films exhibit unconventional robust ferroelectricity at the nanoscale, paving the way for advancements in next-generation nanoelectronics. However, the stability and dynamics of ferroelectric polarization in hafnia-based oxides films, particularly at the nanoscale, warrant further exploration. In this study, we delve into the factors influencing the formation of the ferroelectric phase. Our findings illuminate that the confinement effect of the capped layer enhances the stabilization of the metastable orthorhombic phase, thereby bolstering its ferroelectricity and endurance. Furthermore, we identify an unprecedented polarization-switching behavior in HfO2-based ferroelectric films, characterized by a decrease in the remanent polarization and an increase in the coercive field as the temperature drops. This peculiar phenomenon can be ascribed to the reduction in the long-range interaction of polarization dipoles upon cooling, as evidenced by the dielectric spectrum. The diminished long-range interaction results in the emergence of nanodomains and a re-entrant relaxer behavior, offering novel insights into the origin of ferroelectricity and the stability of ferroelectric polarization in hafnia-based thin films. Given the commendable compatibility of Hf0.5Zr0.5O2 films with Si substrates and a pyroelectric coefficient of -62.1 μC/m2·K, they emerge as a prime candidate for sensor device applications. © 2023, The Authors. All rights reserved.

关键词： Thin films

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Effect of variable stroke on combustion characteristics and stability of a free-piston engine generator

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Applied Thermal Engineering 2025年 277卷

作者： Liu, Chang Jia, Boru Liu, Zhen Zhang, Zhiyuan Hu, Xiaoxu Wei, Shuojian Ma, Yuguo School of Mechanical Engineering Beijing Institute of Technology Beijing 100081 China Hubei Key Laboratory of Power System Design and Test for Electrical Vehicle Hubei University of Arts and Science Xiangyang 441053 China

The free-piston engine generator (FPEG) features a variable stroke structure, offering significant advantages in multi-fuel adaptability and high-efficiency combustion technologies. Stroke control and design directly affect combustion regulation and system performance, and thus represent a key challenge in FPEG development. Existing studies on stroke variation mostly rely on numerical simulations, often neglecting fuel short-circuit losses and lacking experimental validation of actual combustion performance and stability. In this study, an experimental approach was employed to investigate the effects of stroke length variation (47–55 mm) on the combustion characteristics, system performance, and operational stability of an FPEG. The results show that shortening the stroke reduced the indicated work by 4.3 % from 55 mm to 47 mm, but increased the operating frequency by 14.7 %, resulting in a 10 % improvement in indicated power. Moreover, shorter stroke lengths enhanced both indicated thermal efficiency and fuel economy, with the indicated thermal efficiency increasing by 19.6 % and the minimum ISFC reaching 336 g/(kW·h). In terms of stability, the short-stroke configuration markedly reduced cycle-to-cycle variations in both combustion and system operation: COVPmax and COVIMEP decreased by 34.5 % and 50.6 %, respectively, while COVf dropped to 0.59 %.This study is the first to experimentally reveal the influence of stroke variation on FPEG performance, providing valuable data support for structural optimization and performance control of FPEG systems.

关键词： Combustion characteristics Engine performance Free-piston engine generator Stability Variable stroke

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A review and correlations for two phase flow heat transfer in helically coiled tubes 27

A review and correlations for two phase flow heat transfer i...

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27th International Conference on Nuclear Engineering: Nuclear Power Saves the World!, ICONE 2019

作者： Ma, Haifu Xu, Tao Li, Peiying Gou, Junli Yuan, Hongsheng Chen, Wei Wu, Yirui Zhong, Mingjun Gao, Yingxian Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu China School of Nuclear Science and Technology Xi'an Jiaotong University Xi'an710049 China

ISBN: (纸本)9784888983051

Helically coiled heat exchangers have been widely applied in many power conversion systems for their advantages, such as compactness and high efficiency in heat transfer. Reliable heat transfer models are required to analyze the thermal hydraulic characteristics of the once-through helically coiled tube steam generator. The purpose of this study is to evaluate the applicability of the existing heat transfer models. This paper review the experiments for heat transfer in helically coiled tubes in the case of two-phase flow, and summarize and screening corresponding experimental data and correlation. Then, this article compared these correlations to the existing available experimental data to evaluate the applicability of these correlations. Most of the correlations for two phase heat transfer were also valid within the parameter range of pressure, mass flux and heat flux. Results indicate that the currently existing correlation could not accurately match the experiment date. And the Steiner-Taborek correlation was recommended even though the 70% experiment date within the 20% deviation of predicted. Therefore the steam-water two phase flow need to further study to conclude a more suitable correlation in the further. Copyright © 2018-2019 by JSME

关键词： Two phase flow

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Beyond biochemical patterning: How mechanical bistability governs robust organoid morphogenesis

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Mechanobiology in medicine 2025年第2期3卷 100134页

作者： Qigan Gao Yuehua Yang Haoxiang Yang Hongyuan Jiang CAS Key Laboratory of Mechanical Behavior and Design of Materials CAS Center for Excellence in Complex System Mechanics Department of Modern Mechanics University of Science and Technology of China Hefei Anhui 230026 China.

Understanding the regulatory mechanisms of intestinal organoid morphogenesis remains a fundamental challenge in organoid biology. Emerging evidence highlights mechanical bistability as a critical regulator, mediated by dynamic lumen-actomyosin feedback. The recently developed 3D vertex model demonstrates that crypt curvature modulates actomyosin localization via mechanosensitive pathways, creating two stable morphological states-bulged or budded-depending on mechanical history. This model advances beyond static vertex models by incorporating epithelial thickness variations and lumen pressure effects, explaining previously unresolved phenomena like irreversible crypt budding and snap-through transitions. The findings establish a new framework for understanding mechanical decision-making in epithelial tissues, with implications for organoid engineering and developmental biology.

关键词： Epithelial mechanics Intestinal organoids Mechanical bistability Morphogenesis Vertex model

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The SIF model of Zr-4 cladding tube with axial cracks 14

The SIF model of Zr-4 cladding tube with axial cracks

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14th International Nuclear Fuel Cycle Conference, GLOBAL 2019 and Light Water reactor Fuel Performance Conference, TOP FUEL 2019

作者： Chen, L. Liu, L.L. Song, X.M. Pang, H. Xie, X.M. Zeng, X.G. Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China No.328 1st Section of Changshun Avenue Chengdu610213 China Sichuan University No.24 1st South Section of 1st Ring Road Chengdu610021 610213 China

The calculation of the stress intensity factor (SIF) on the axial cracking of the cladding tube is the basis for the study of the failure phenomena of delayed hydride cracking (DHC) and hydrogen embrittlement (HE). In most hydrogen failure models, especially the DHC model, an infinite or semi-infinite plate is used as the modeling basis. There is no doubt that cylindrical shell as a modeling object will make the calculation more accurate for nuclear fuel cladding. This work analyzes the influence of geometric conditions and the external load conditions on SIF of tubular components, respectively, based on virtual crack closure technique (VCCT), using single variable. Then the influence of crack length on SIF is analyzed under concentrated stress loading on the end of Zr-4 cladding tube by numerical analysis method. The approximate calculation formula of the stress intensity factor on the crack front is obtained and verified. Copyright © GLOBAL 2019 - International Nuclear Fuel Cycle Conference and TOP FUEL 2019 - Light Water reactor Fuel Performance *** rights reserved.

关键词： Stress analysis

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The friction characteristics and velocity distribution of pulsatile flows in a rod bundle 27

The friction characteristics and velocity distribution of pu...

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27th International Conference on Nuclear Engineering: Nuclear Power Saves the World!, ICONE 2019

作者： Li, Xing Qi, Peiyao Tan, Sichao Mi, Zhengpeng Li, Dongyang Fundamental Science on Nuclear Safety and Simulation Technology Laboratory Harbin Engineering University Harbin Heilongjiang China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu China

ISBN: (纸本)9784888983051

The transient fluctuation of flow rate in a nuclear reactor is a common phenomenon in floating reactors and possible accident scenarios, the response for transient flow determined the damage threshold of fuel assemblies. Friction characteristics and velocity distribution of low-frequency pulsatile flows in a rod bundle have been studied. The experiments were conducted under the time-averaged Reynolds number 1000 Copyright © 2018-2019 by JSME

关键词： Pressure drop

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Observation of intrinsic chiral bound states in the continuum

arXiv

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arXiv 2022年

作者： Chen, Yang Deng, Huachun Sha, Xinbo Chen, Weijin Wang, Ruize Chen, Yuhang Wu, Dong Chu, Jiaru Kivshar, Yuri S. Xiao, Shumin Qiu, Cheng-Wei Department of Electrical and Computer Engineering National University of Singapore Singapore117583 Singapore Chinese Academy of Sciences Key Laboratory of Mechanical Behavior and Design of Materials Department of Precision Machinery and Precision Instrumentation University of Science and Technology of China Hefei230027 China Ministry of Industry and Information Technology Key Lab of Micro-Nano Optoelectronic Information System Harbin Institute of Technology Shenzhen518055 China Nonlinear Physics Center Research School of Physics Australian National University CanberraACT2601 Australia Pengcheng Laboratory Shenzhen518055 China

Photons with spin angular momentum possess intrinsic chirality which underpins many phenomena including nonlinear optics1, quantum optics2, topological photonics3 and chiroptics4. Intrinsic chirality is weak in natural materials, and recent theoretical proposals5-7 aimed to enlarge circular dichroism by resonant metasurfaces supporting bound states in the continuum that enhance substantially chiral light-matter interaction. Those insightful works resort to three-dimensional sophisticated geometries, which are too challenging to be realized for optical frequencies8. Therefore, most of the experimental attempts9-11 showing strong circular dichroism rely on false/extrinsic chirality by employing either oblique incidence9, 10 or structural anisotropy11. Here, we report on the experimental realization of true/intrinsic chiral response with resonant metasurfaces where the engineered slant geometry breaks both in-plane and out-of-plane symmetries. Our result marks the first observation of intrinsic chiral bound states in the continuum with near-unity chiral dichroism of 0.93 and record-high quality factor exceeding 2663 for visible frequencies. Our chiral metasurfaces promise a plethora of applications in chiral light sources and detectors, chiral sensing, valleytronics and asymmetric photocatalysis. © 2022, CC BY.

关键词： Dichroism

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The Impact Failure and Energy Dissipation Mechanism of Polyethylene Laminates

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Journal of Wuhan University of technology(Materials science) 2019年第3期34卷 723-727页

作者： SHU Zaiqin ZHANG Jinyong State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Institute of Material Science and EngineeringWuhan University of TechnologyWuhan430070China System Design Institute of Hubei Aerospace Technology Academy Wuhan430040China

The damage mechanism and energy dissipation of the Polyethylene (PE) laminates in impacting was investigated. It was found that the dissipated energy of the impacting sphere bullet by the 1-mmthick PE plate firstly increased with the impacting velocity increasing from 50 to about 300 m/s, and then decreased with the impacting velocity increasing up to 600 m/s. According to the measured deformation and damage degree, a numerical simulation of the dissipated energy was made and obvious offset was found with the experimental results. The quasi-static properties of the PE fibers, decreasing with increase in tensile velocity, may be the main reason for the offset.

关键词： polyethylene ballistic impact energy dissipation strain rate

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