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Experimental study on the space charge properties in haze events

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Journal of Environmental Sciences 2020年第1期32卷 361-376页

作者： xiaobin zhang Sen Yang Tianli Bo Key Laboratory of Mechanics on Western Disaster and Environment Lanzhou University

In recent years,haze has posed a serious threat to the global climate change,ecological balance and human *** this study,the laboratory experiments and field observations were performed and a possible charging mechanism was proposed to investigate the space charge properties in haze *** laboratory experiments showed that the charge polarity of primary aerosol is determined by species of combustion fuels while the magnitude is dependent on the combustion *** field observations revealed that the space charge of atmosphere aerosol in haze events differs from that of fair weather and is closely related to PM2.5 concentration when Relative Humidity(RH)<60%,with 1 to 2 orders of magnitude less than the case when RH≥60%.The analysis of equivalent chargeto-mass ratio(ECTM)suggested that in haze events the space charge is governed by primary aerosol emitted by combustion of fossil fuel in a low relative humidity,whereas it is manipulated by the secondary chemical reaction of atmosphere aerosol in a high relative *** we can identify the main pollutants in haze events according to the polarity of atmosphere aerosol and quickly take measures when RH<60%.Accordingly,the dusthaze of RH<80% can be divided into dry-dust-haze when RH<60%and wet-dust-haze when 60%≤RH<80%.Our study firstly elucidated the space charge properties of atmosphere aerosol in haze events and can provide a new perspective for the prevention and control of air pollution.

关键词： Haze Atmosphere aerosol Space charge density(SCD) Equivalent charge-to-mass ratio(ECTM) Charging mechanisms

Experimental research on aero-propulsion coupling characteristics of a distributed electric propulsion aircraft

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Chinese Journal of Aeronautics 2023年第2期36卷 201-212页

作者： Xingyu zhang Wei zhang Weilin LI xiaobin zhang Tao LEI School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China Key Laboratory of Aircraft Electric Propulsion Technology Ministry of Industry and Information TechnologyXi'an 710072China School of Automation Northwestern Polytechnical UniversityXi'an 710072China

Distributed Electric Propulsion(DEP)aircraft use multiple electric motors to drive the propulsors,which gives potential benefits to aerodynamic-propulsion *** investigate and quantify the aerodynamic-propulsion interaction effect of the wing section,we built a DEP demonstrator with 24"high-lift"Electric Ducted Fans(EDFs)distributed along the wing’s trailing *** paper explores and compares the aero-propulsion coupling characteristics under various upstream speed,throttle,and EDF mounting surface deflection angles using a series of wind tunnel *** compare various lift-augmentation power conditions to the clean configuration without propulsion unit under the experiment condition of 15-25 m/s freestream flow and angles of attack from-4°to 16°.The comparison of computational results to the experimental results verifies the effectiveness of the computational fluid dynamic analysis method and the modeling method for the DEP *** results show that the EDFs can produce significant lift increment and drag reduction simultaneously,which is accordant with the potential benefit of Boundary Layer Ingestion(BLI)at low airspeed.

关键词： Aero-propulsion coupling Boundary layer ingestion Distributed electric propulsion Short Take-Off and Landing(STOL) Wind-tunnel experiment

Mechanical properties of Cu based composites reinforced by carbon nanotubes

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中国有色金属学会会刊：英文版 1999年第3期9卷 457-461页

作者： Dong Shurong(董树荣) zhang xiaobin(张孝彬) Zhejiang Univ Dept Informat & Elect Engn Hangzhou 310027 Peoples R China

Cu based composites reinforced by 0%～25% (volume fraction) carbon nanotubes were *** fracture behaviors and the rolling properties of the composites and the effects of the volume fraction of the carbon nanotubes were *** experimental results show that the fracture toughness of the composites is related to the pulling out and bridging of the carbon nanotubes in the fracture *** the volume fraction of the carbon nanotubes increasing, the Vicker’s hardness and the compactness of the composites increase first and then decrease. The peaks of the hardness and the compactness occur at 12%～15% of volume fraction of carbon *** proper ratio of rolling reduction benefits to the comprehensive mechanical properties of the composites.

关键词： Cu matrix composites carbon nanotubes nanotubes content fracture behavior rolling

State of art on energy management strategy for hybrid-powered unmanned aerial vehicle

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Chinese Journal of Aeronautics 2019年第6期32卷 1488-1503页

作者： Tao LEI Zhou YANG Zicun LIN xiaobin zhang School of Automation Northwestern Polytechnic UniversityXi’an 710129China Key Laboratory of Aircraft Electric Propulsion Technology Ministry of Industry and Information Technology of ChinaXi’an 710129China

New energy sources such as solar energy and hydrogen energy have been applied to the Unmanned Aerial Vehicle(UAV), which could be formed as the hybrid power sources due to the requirement of miniaturization, lightweight, and environmental protection issue for UAV. Hybrid electrical propulsion technology has been used in UAV and it further enforces this trend for the evolution to the Hybrid-Powered System(HPS). In order to realize long endurance flight mission and improve the energy efficiency of UAV, many researching works are focused on the Energy Management Strategy(EMS) of the HPS with digital simulation, ground demonstration platforms and a few flight tests for the UAV in recent years. energy management strategy, in which off-line or on-line control algorithms acted as the core part, could optimize dynamic electrical power distribution further and directly affect the efficiency and fuel economy of hybrid-powered system *** order to give the guideline for this emerging technology for UAV, this paper presents a review of the topic highlighting energy optimal management strategies of UAV. The characteristics of typical new energy sources applied in UAV are summarized firstly, and then the classification and analysis of the architecture for hybrid power systems in UAV are presented. In the context of new energy sources and configuration of energy system, a comprehensive comparison and analysis for the state of art of EMS are presented, and the various levels of complexity and accuracy of EMS are considered in terms of real time, computational burden and optimization performance based on the optimal control and operational modes of UAV. Finally, the tendency and challenges of energy management strategy applied to the UAV have been forecasted.

关键词： Energy management strategy(EMS) Hybrid power system(HPS) New energy sources Optimization algorithms UAV

Global research on artificial intelligence in thyroid-associated ophthalmopathy:A bibliometric analysis

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Advances in Ophthalmology Practice and Research 2024年第1期4卷 1-7页

作者： xiaobin zhang Department of Health Sciences National Natural Science Foundation of ChinaBeijingChina

Purpose:To provide an overview of global publications on artificial intelligence(AI)in thyroid-associated oph-thalmopathy(TAO)through bibliometric ***:Publications related to AI in TAO from inception until April 2023 were retrieved from the Web of Science *** trends of publications and citations,publishing performance,collaboration among countries and institutions,and the funding agencies,relevant research domains,leading journals,hotspots and their evolution were ***:A total of 55 publications were included for *** number of publications and citations continued to grow since 1998,with a significant acceleration of growth after *** is the most productive country with the highest number of productive institutions,followed by the United *** countries have the most extensive *** most relevant research domain was radiology,nuclear medicine&medical *** European Journal of Radiology was one of the most productive journals,with the most influential articles published."Thyroid-associated ophthalmopathy"and"neural network"maintain hotspots during the entire *** were more focused on clinical features during 1998 and 2016,clinical features and medical data during 2017 and 2020,and medical data and AI techniques during 2021 and ***:This study summarized the global research status regarding AI in TAO in terms of trends,countries,institutions,research domains,journals,and key *** has shown great potential in *** by funding agencies such as NSFC,China has become the most productive country in the field of AI in *** findings help researchers better understand the development of this field and provide valuable clues for future research directions.

关键词： Thyroid-associated ophthalmopathy Artificial intelligence Global publications Bibliometric analysis

Theoretical analysis of hydrogen solubility in direct coal liquefaction solvents

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International Journal of Coal Science & Technology 2024年第2期11卷 187-197页

作者： xiaobin zhang Aoqi Wang Xingbao Wang Wenying Li State Key Laboratory of Clean and Efficient Coal Utilization Taiyuan University of TechnologyTaiyuan 030024ShanxiChina College of Chemical Engineering and Technology Taiyuan University of TechnologyTaiyuan 030024China

The cyclic hydrogenation technology in a direct coal liquefaction process relies on the dissolved hydrogen of the solvent or oil participating in the hydrogenation ***,a theoretical basis for process optimization and reactor design can be established by analyzing the solubility of hydrogen in liquefaction *** studies of hydrogen solubility in liquefaction solvents are challenging due to harsh reaction conditions and complex solvent *** this study,the composition and content of liquefied solvents were *** model compounds,hexadecane,toluene,naphthalene,tetrahydronaphthalene,and phenanthrene were chosen to represent the liquefied solvents in chain alkanes and monocyclic,bicyclic,and tricyclic aromatic *** solubility of hydrogen X(mol/mol)in pure solvent components and mixed solvents(alkanes and aromatics mixed in proportion to the chain alkanes+bicyclic aromatic hydrocarbons,bicyclic saturated aromatic hydrocarbons+bicyclic aromatic hydrocarbons,and bicyclic aromatic hydrocarbons+compounds containing het-eroatoms composed of mixed components)are determined using Aspen simulation at temperature and pressure conditions of 373–523 K and 2–10 *** results demonstrated that at high temperatures and pressures,the solubility of hydrogen in the solvent increases with the increase in temperature and pressure,with the pressure having a greater ***-more,the results revealed that hydrogen is more soluble in straight-chain alkanes than in other solvents,and the solubility of eicosanoids reaches a maximum of *** hydrogen solubility in aromatic ring compounds decreased gradually with an increase in the aromatic ring *** influence of chain alkanes on the solubility of hydrogen predominates in a mixture of solvents with different mixing ratios of chain alkanes and aromatic *** solubility of hydrogen in mixed aromatic solvents is less than that in the corresponding single ***

关键词： Direct coal liquefaction Liquefaction solvents Process simulation Hydrogen solubility

Group decision-making method based on entropy and experts cluster analysis

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Journal of Systems Engineering and Electronics 2011年第3期22卷 468-472页

作者： Xuan Zhou Fengming zhang xiaobin Hui Kewu Li Engineering College Air Force Engineering UniversityXi'an 710038P.R.China

According to the aggregation method of experts＇ evaluation information in group decision-making,the existing methods of determining experts＇ weights based on cluster analysis take into account the expert＇s preferences and the consistency of expert＇s collating vectors,but they lack of the measure of information *** it may occur that although the collating vector is similar to the group consensus,information uncertainty is great of a certain ***,it is clustered to a larger group and given a high *** this,a new aggregation method based on entropy and cluster analysis in group decision-making process is provided,in which the collating vectors are classified with information similarity coefficient,and the experts＇ weights are determined according to the result of classification,the entropy of collating vectors and the judgment matrix ***,a numerical example shows that the method is feasible and effective.

关键词： group decision-making judgment matrix entropy information similarity coefficient cluster analysis.

Circulating current suppression for ground tied variable frequency to constant frequency converter system in aircraft

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Chinese Journal of Aeronautics 2023年第11期36卷 386-397页

作者： Wei WEI Ming HUANG Wenli YAO Weilin LI xiaobin zhang School of Automation Northwestern Polytechnical UniversityXi’an 710072China Air Defense and Antimissile School Air Force Engineering UniversityXi’an 710100China

This paper presents a solution to the circulating current fault of aircraft power *** DC-link type Variable Frequency to Constant Frequency(VFCF)converter system is the preferred scheme to feed the constant 400 Hz load in an aircraft with a variable frequency power *** to the requirement of aircraft standards,both grounds of the rectification and inversion stage are tied to the metal frame of the *** such a tied ground,the DC bus voltage rises greatly,and a large circulating current appears in the casing as the ground,which leads to equipment failure and potential safety *** to the existing methods of circulating current fault suppression,this paper analyzes the causes of the above faults and the harmonic components of circulating current and points out the limitations of the existing ***,a Common-Mode(CM)choke-based method is proposed to provide a high impedance in the path of the CM circulating *** doing so,the circulating current can be suppressed without the additional burden of the hardware and control algorithm,which is quite friendly for quality control of mass-production ***,a simplified mathematic model of the VFCF converter system is derived to calculate the minimum inductance value reference of the CM choke,which saves the weight of passive devices to the greatest ***,simulation and experimental results are studied to verify the effectiveness of the proposed method.

关键词： Aircraft power supply Circulating current Common mode choke Power supply circuits Variable Speed Constant Frequency

Validation of dynamic cavitation model for unsteady cavitating flow on NACA66

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Science China(Technological Sciences) 2014年第4期57卷 819-827页

作者： zhang xiaobin zhang Wei CHEN JianYe QIU LiMin SUN DaMing Institute of Refrigeration and Cryogenics Zhejiang University

Unsteady cavitating flow is extremely complicated and brings more serious damages and unignorable problems compared with steady cavitating *** has become a practical way to model cavitation;however,the popularly used full cavitation model cannot reflect the pressure-change that the bubble experiences during its life path in the highly unsteady flow like cloud *** a dynamic cavitation model(DCM)is proposed and it has been considered to have not only the first-order pressure effects but also zero-order effect and can provide greater insight into the physical process of bubble producing,developing and collapsing compared to the traditional cavitation *** has already been validated for steady cavitating flow,and the results were ***,DCM is designed and supposed to be more accurate and efficient in modeling unsteady cavitating flow,which is also the purpose of this *** basic characteristic of the unsteady cavitating flow,such as the vapor volume fraction distribution and the evolution of pressure amplitude and frequency at different locations of the hydrofoil,are carefully studied to validate *** is found that not only these characteristics mentioned above accord well with the experimental results,but also some detailed transient flow information is depicted,including the re-entrant jet flow that caused the shedding of the cavity,and the phenomenon of two-peak pressure fluctuation in the vicinity of the cavity closure in a *** numerical results validate the capability of DCM for the application of modeling the complicated unsteady cavitating flow.

关键词： unsteady cavitation dynamical cavitation model NACA66 hydrofoil