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Statistical analysis on the validity of the cold plasma approximation for chorus waves based on Van Allen Probe observations and their effects on radiation belt electrons

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Earth and Planetary Physics 2025年第1期9卷 159-170页

作者： AoJun Ren Jiang Yu Jing Wang ZuZheng Chen XiaoMan Liu Planetary Environmental and Astrobiological Research Laboratory(PEARL) School of Atmospheric SciencesSun Yat-sen UniversityZhuhai Guangdong 519000China

Theoretical analysis has demonstrated that the dispersion relation of chorus waves plays an essential role in the resonant interaction and energy transformation between the waves and magnetospheric *** quantitative analyses often simplified the chorus dispersion relation by using the cold plasma ***,the applicability of the cold plasma assumption is doubtful,especially during geomagnetic *** here present a systematic statistical analysis on the validity of the cold plasma dispersion relation of chorus waves based on observations from the Van Allen Probes over the period from 2012 to *** statistical results show that the observed magnetic field intensities deviate substantially from those calculated from the cold plasma dispersion relation and that they become more pronounced with an increase in geomagnetic activity or a decrease in background plasma *** region with large deviations is mainly concentrated in the nightside and expands in both the radial and azimuthal directions as the geomagnetic activity increases or the background plasma density *** addition,the bounce-averaged electron scattering rates are computed by using the observed and cold plasma dispersion relation of chorus *** with usage of the cold plasma dispersion relation,usage of the observed dispersion relation considerably lowers the minimum resonant energy of electrons and lowers the scattering rates of electrons above tens of kiloelectronvolts but enhances those ***,these differences are more pronounced with the enhancement of geomagnetic activity or the decrease in background plasma density.

关键词： chorus waves cold plasma approximation dispersion relations scattering rates

A comprehensive review of cavitation in valves:mechanical heart valves and control valves

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Bio-Design and Manufacturing 2019年第2期2卷 119-136页

作者： Jin-yuan Qian Zhi-xin Gao Cong-wei Hou Zhi-jiang Jin Institute of Process Equipment College of Energy EngineeringZhejiang UniversityHangzhou 310027People’s Republic of China State Key Laboratory of Fluid Power and Mechatronic Systems Zhejiang UniversityHangzhou 310027People’s Republic of China

Valves are widely used in various working conditions for their flow control functions,and the cavitation inside valves has been investigated owing to its harm to the valve itself and the connecting downstream *** paper presents a comprehensive review of the progress that has been achieved in the past years about cavitation in valves including both mechanical heart valves and control *** review is divided in the following parts,namely the location where there is a high possibility of the occurrence of cavitation,the parameters that affect cavitation intensity,and the methods to minimize cavitation *** should be noticed that although simulation has been widely used,advanced experiments are still needed in order to obtain accurate analysis of cavitation in valves and the cavitation model still needs to be improved.

关键词： Cavitation Mechanical heart valves Control valves

Archetype identification and urban building energy modeling for city-scale buildings based on GIS datasets

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Building Simulation 2022年第9期15卷 1547-1559页

作者： Zhang Deng Yixing Chen Jingjing Yang Zhihua Chen College of Civil Engineering Hunan UniversityChangsha 410082China Key Laboratory of Building Safety and Energy Efficiency of Ministry of Education Hunan UniversityChangsha 410082China

Urban building energy modeling has become an efficient way to understand urban building energy use and explore energy conservation and emission reduction *** paper introduced a method to identify archetype buildings and generate urban building energy models for city-scale buildings where public building information was unavailable.A case study was conducted for 68,966 buildings in Changsha city,***,clustering and random forest methods were used to determine the building type of each building footprint based on different GIS ***,the convolutional neural network was employed to infer the year built of commercial buildings based on historical satellite images from multiple *** year built of residential buildings was collected from the housing ***,twenty-two building types and three vintages were selected as archetype buildings to represent 59,332 buildings,covering 87.4%of the total floor *** scripts leveraging on OpenStudio-Standards were developed to generate building energy models for the archetype ***,monthly and annual electricity and natural gas energy use were simulated for the blocks and the entire city by *** total electricity and natural gas use for the 59,332 buildings was 13,864 GWh and 23.6×10^(6) *** energy conservation measures were evaluated to demonstrate urban energy saving *** proposed methods can be easily applied to other cities in china.

关键词： urban building energy modeling building type year built-archetype building EnergyPlus

Flow Field Simulation and Parameter Analysis of Hydraulic Unbalanced Bionic Self-recovery Actuator for Rotary Equipment

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Journal of Bionic Engineering 2024年第1期21卷 325-343页

作者： Wei Li Xin Pan Dehong Ge Jinji Gao Key Laboratory of Engine Health Monitoring-Control and Networking of Ministry of Education Beijing University of Chemical TechnologyBeijing 100029China Beijing Key Laboratory of High-End Mechanical Equipment Health Monitoring and Self-Recovery Beijing University of Chemical TechnologyBeijing 100029China

The rotor is the most important component of rotating machinery,and the vibration produced by its mass unbalance has a serious influence on the secure and steady operation of the machine,so an effective online suppression technology is urgently needed.A new hydraulic unbalanced bionic self-recovery system is introduced,imitating the way of manually repairing faulty *** accomplish the effect of actuator mass redistribution,the technology employs pressurized air to drive the quantitative transfer of liquid in the reservoir cavity at opposite *** can complete the online adjustment of the equipment's balancing state and suppress the unbalanced vibration of equipment in real time,which gives the equipment the ability to maintain an autonomous health state and improve equipment *** composition and working principle of the system are introduced in detail,and the key performance parameters,such as the minimum running speed and the balancing liquid transfer speed,are analyzed *** fluid-solid coupling model of the actuator was established,and the two-phase flow from inside the hydraulic unbalanced bionic self-recovery actuator was simulated under multiple working conditions and the performance parameters were quantitatively analyzed.A balancing simulation test bed was built,and its effectiveness was verified by performance parameter tests and unbalanced bionic self-recovery *** experimental results show that the mass distribution adjustment of the balancing disk can be achieved using different viscosity balancing liquid,and the response of liquid viscosity 10 cSt is faster than that of liquid viscosity 100 cSt in the process of balancing liquid transfer,and the time is reduced by more than 75%;the system can reduce the simulated rotor amplitude from 18.3μm to 10.6μm online in real time,which provides technical support for the subsequent development of a new generation of bionic intelligent equipment.

关键词： Engineering self-recovery-Bionics Simulation analysis Self-recovery regulation

Investigation on Cooling Effectiveness and Aerodynamic Loss of a Turbine Cascade with Film Cooling

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Journal of Thermal science 2016年第1期25卷 50-59页

作者： LIU Jianjun LIN Xiaochun ZHANG Xiaodong AN Baitao Institute of Engineering Thermophysics Chinese Academy of Sciences 11 Bcisihuan West RoadBeijing 100190China School of Physics University of Chinese Academy of Sciences 19A Yuquan RoadBeijing 100049China

This paper describes the numerical study on film cooling effectiveness and aerodynamic loss due to coolant and main stream mixing for a turbine guide vane. The effects of blowing ratio, mainstream Mach number, surface curvature on the cooling effectiveness and mixing loss were studied and discussed. The numerical results show that the distributions of film cooling effectiveness on the suction surface and pressure surface at the same blowing ratio(BR) are different due to local surface curvature and pressure gradient. The aerodynamic loss features for film holes on the pressure surface are also different from film holes on the suction surface.

关键词： turbine guide vane film cooling cooling effectiveness aerodynamic loss

A single-point measurement scheme for quantum work based on the squeezing state

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Communications in Theoretical Physics 2021年第6期73卷 51-58页

作者： Bao-Ming Xu Jian Zou Zhan-Chun Tu Shandong Key Laboratory of Biophysics Institute of BiophysicsDezhou UniversityDezhou 253023China School of Physics Beijing Institute of TechnologyBeijing 100081China Department of Physics Beijing Normal UniversityBeijing 100875China

To investigate the role of initial quantum coherence in work-probability distribution,it is necessary to consider an incomplete or partial measurement,in which the energy cannot be fully discriminated by the *** this paper,we use a harmonic oscillator with a coherent or squeezing state to realize this incomplete or partial measurement,and propose a unified framework of quantum work statistics for a closed system with an arbitrary initial *** find that work is proportional to the change of the real part of the coherent state parameter,i.e.,quantum work can be estimated by the coherent state *** resulting work-probability distribution includes the initial quantum coherence,and can be reduced to the result of the traditional two projective energy measurement scheme(TPM)by squeezing the state of the harmonic *** measurement scheme reveals the fundamental connections between measurement error and coherent *** introducing a‘coherent work-to-noise ratio’,we find the optimal measurement error,which is determined by the energy difference between the superposed energy *** an application,we consider a driven two-level system and investigate the effects of driving velocity on work *** find that only when the driving velocity matches the transition frequency of the system can initial quantum coherence play an important role.

关键词： work distribution quantum coherence coherent state squeezing state

GLOBAL VIEW OF MICROSTRUCTURAL EVOLUTION:ENERGETICS,KINETICS AND DYNAMICAL SYSTEMS

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Acta Mechanica Sinica 1996年第2期12卷 144-157页

作者：杨卫锁志钢 Dept.Eng.Mech. Tsinghua Univ.Beijing 100084China Mech.Environ.Eng.Dept. Univ.CaliforniaSanta BarbaraCA 93106USA

An evolving material structure is in a non-equilibrium state, with free energy expressed by the generalized coordinates. A global approach leads to robust computations for the generalized thermodynamic forces. Those forces drive various kinetic processes, causing dissipation at spots, along curves, surfaces and interfaces, and within volumetric regions. The actual evolution path, and therefore the final equilibrium state, is determined by the energetics and kinetics. A virtual work principle Links the free energy landscape and the kinetic processes, and assigns a viscous environment to every point on the landscape. The approach leads to a dynamical system that governs the evolution of generalized coordinates. The microstructural evolution is globally characterized by a basin map in the coordinate space; and by a diversity map and a variety map in the parameter space. The control of basin boundaries raises the issue of energetic and kinetic bifurcations. The variation of basin boundaries under different sets of controlling parameters provides an analytical way to plot the diversity maps of structural evolution.

关键词： microstructural evolution energetics kinetics dynamic system

The Unsteady Fluctuating Pressure and Velocity in a Cross Flow Fan

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Journal of Thermal science 2008年第4期17卷 349-355页

作者： Jiaye Gan Fei Liu Min Liu Keqi Wu State Key Laboratory of Coal Combustion Huazhong University of Science and Technology Wuhan 430074 Chinaganjiaye0775 @ ***

This paper investigates the relations between the fluctuating pressure and velocity of the source by means of nu- merical method and sound pressure in the far field obtained with an noise experiment for a novel cross flow fan. The frequency characteristics of the fluctuating pressure and velocity in a cross flow fan are analyzed by means of spectral analysis and wavelet transform. The fluctuating pressures obtained by large eddy simulation on the casing wall are compared with that of experiments and show good agreement. From the spectral analysis of sound source, it is found that the pressure fluctuating peak is correspond with the sound pressure in the far field.

关键词： cross flow fan spectral analysis aerodynamic noise

A Model for Fractal Dimension of Rough Surfaces

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Chinese Physics Letters 2009年第11期26卷 133-135页

作者：李建华郁伯铭邹明清 Biomedical Materials and Engineering Research Center Wuhan University of Technology Wuhan 430070 School of Physics Huazhong University of Science and Technology Wuhan 430074

We report a model for the fractal dimension D8 of rough surfaces based on the fractal distribution of roughness elements on surfaces and the fractal character of surface profiles. The proposed model for the fractal dimension Ds is expressed as a function of the fractaJ dimensions D for conic roughness diameter/height and Dp for surface profile, maximum roughness base diameter λmax, the ratio β of conic roughness height to its base radius as well as the ratio λmin/λmasx of the minimum to the maximal base diameter.

关键词： No English Keyword