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Flight dynamics modeling and analysis for a Mars helicopter

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中国航空学报:英文版 2023年第9期36卷 221-230页

作者： Hong ZHAO zhiwei DING Gen leng Jianbo LI National Key Laboratory of Helicopter Aeromechanics Nanjing University of Aeronautics and AstronauticsNanjing 210016China China Helicopter Research&Development Institute Jingdezhen 33300China

Flight dynamics modeling for the Mars helicopter faces great challenges.Aerodynamic modeling of coaxial rotor with high confidence and high computational efficiency is a major difficulty for the field.This paper builds an aerodynamic model of coaxial rotor in the extremely thin Martian atmosphere using the viscous vortex particle method.The aerodynamic forces and flow characteristics of rigid coaxial rotor are computed and analyzed.Meanwhile,a high fidelity aerodynamic surrogate model is built to improve the computational efficiency of the flight dynamics model.Results in this paper reveal that rigid coaxial rotor can bring the Mars helicopter sufficient controllability but result in obvious instability and control couplings in forward flight.This highlights the great differences in flight dynamics characteristics compared with conventional helicopters on Earth.

关键词： Aerodynamic modeling Coaxial rotor Flight dynamics Mars helicopter Viscous Vortex Particle Method(VVPM)

Passive attitude stabilization of ionic-wind-powered micro air vehicles

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Chinese Journal of Aeronautics 2023年第7期36卷 412-419页

作者： Hengyu ZHANG Jiaming leng zhiwei LIU Mingjing QI Xiaojun YAN School of Energy and Power Engineering Beihang UniversityBeijing 100191China

The ionic-wind-powered Micro Air Vehicles(MAVs)can achieve a higher thrust-toweight ratio than other MAVs.However,this kind of MAV has not yet achieved controlled flight because of the unstable thrust produced by the ionic wind and the dynamic instability related to the small size.In this paper,a passive attitude stabilization method of the ionic-wind-powered MAV using air dampers is introduced.The key factors that influence the performance of the air dampers,including the layout,position,and area of the air dampers,are theoretically studied.The appropriate optimal position of the air dampers is also obtained by Monte Carlo stochastic simulations.Then the proposed passive attitude stabilization method is applied to the ionic-wind-powered MAVs of different wingspan(2 cm and 6.3 cm).Finally,the experimental results show that using the proposed method,attitude stabilization is achieved for the first time for the ionic-wind-powered MAV.Moreover,the altitude control of an ionic-wind-powered MAV with a wingspan of 6.3 cm is also demonstrated.

关键词： Air dampers Altitude control Ionic wind propulsion Micro air vehicle Monte Carlo methods Stability

Selective preparation for biofuels and high value chemicals based on biochar catalysts

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Frontiers in Energy 2023年第5期17卷 635-653页

作者： Hui LI Changlan HOU Yunbo ZHAI Mengjiao TAN Zhongliang HUANG zhiwei WANG Lijian leng Peng LIU Tingzhou LEI Changzhu LI State Key Laboratory of Utilization of Woody Oil Resource Hunan Academy of ForestryChangsha 410004China College of Environmental Science and Engineering Hunan UniversityChangsha 410082China School of Environmental Engineering Henan University of TechnologyZhengzhou 450001China School of Energy Science and Engineering Central South UniversityChangsha 410083China National-Local Joint Engineering Research Center of Biomass Refining and High-Quality Utilization Institute of Urban and Rural MiningChangzhou UniversityChangzhou 213164China

The reuse of biomass wastes is crucial toward today’s energy and environmental crisis,among which,biomass-based biochar as catalysts for biofuel and high value chemical production is one of the most clean and economical solutions.In this paper,the recent advances in biofuels and high chemicals for selective production based on biochar catalysts from different biomass wastes are critically summarized.The topics mainly include the modification of biochar catalysts,the preparation of energy products,and the mechanisms of other high-value products.Suitable biochar catalysts can enhance the yield of biofuels and higher-value chemicals.Especially,the feedstock and reaction conditions of biochar catalyst,which affect the efficiency of energy products,have been the focus of recent attentions.Mechanism studies based on biochar catalysts will be helpful to the controlled products.Therefore,the design and advancement of the biochar catalyst based on mechanism research will be beneficial to increase biofuels and the conversion efficiency of chemicals into biomass.The advanced design of biochar catalysts and optimization of operational conditions based on the biomass properties are vital for the selective production of high-value chemicals and biofuels.This paper identifies the latest preparation for energy products and other high-value chemicals based on biochar catalysts progresses and offers insights into improving the yield of high selectivity for products as well as the high recyclability and low toxicity to the environment in future applications.

关键词： biomass biochar catalysts biofuels high chemicals

Long-term outcomes in COVID-19 patients who recovered from the first wave of the pandemic

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National Science Review 2022年第11期9卷 87-96页

作者： Dan Cui Simiao Chen Luzhao Feng Mengmeng Jia Yeming Wang Weijun Xiao Yanxia Sun Qiangru Huang Libing Ma Zhiwei Leng Hao Wang Bin Cao Weizhong Yang Juntao Yang Chen Wang Department of Pulmonary and Critical Care Medicine The Second Affiliated Hospital of Harbin Medical UniversityHarbin Medical University Department of Pulmonary and Critical Care Medicine National Center for Respiratory Medicine Center of Respiratory MedicineNational Clinical Research Center for Respiratory Diseases China-Japan Friendship Hospital Heidelberg Institute of Global Health Faculty of Medicine and University Hospital Heidelberg University School of Population Medicine and Public Health Chinese Academy of Medical Sciences &Peking Union Medical College Department of Respiratory and Critical Care Medicine the Affiliated Hospital of Guilin Medical University Institute of Respiratory Medicine Chinese Academy of Medical Science State Key Laboratory of Medical Molecular Biology Department of Biochemistry and Molecular BiologyInstitute of Basic Medical Sciences Chinese Academy of Medical Sciences & Peking Union Medical College

This cross-sectional study evaluated the long-term health effects of coronavirus disease 2019(COVID-19)in Jianghan District(Wuhan, China). The results showed that 61.4% of COVID-19 patients reported at least one symptom and 8.8% had depressive symptoms at the 17-month follow-up. The proportion of patients with chest radiographic abnormalities in Fangcang shelter hospitals and designated COVID-19hospitals was 31.6% and 41.1%, respectively, and the proportion of patients with impaired pulmonary diffusion capacity in these hospitals was 52.8% and 60.9%, respectively. Female sex(odds ratio[OR] = 1.48, 95% confidence interval [CI]: 1.16–1.88), severe disease(OR = 1.46, 95% CI: 1.01–2.10)and a higher number of initial symptoms(OR = 1.31, 95% CI: 1.23–1.40) were associated with the development of sequelae symptoms at 17 months. This study involving community-dwelling COVID-19adults may help determine the long-term effects of COVID-19 during the first pandemic wave.Nonetheless, larger follow-up studies are needed to characterize the post-COVID-19 condition.

关键词： SARS-CoV-2 post-COVID-19 syndrome follow-up studies

Role of social organization engagement in high-risk groups intervention against HIV/AIDS:a case study from 176 cities of China

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Infectious Diseases of Poverty 2022年第6期11卷 70-83页

作者： Zhiwei Leng Sha Sha Shuyu Dai Xuehui Meng Jinfeng Li Junyi Jin Wenlin Zheng Weihua Yang Chuanju Mao Zhenzhong Wang Liujin Zhang Peng Wang Tao Yang Weizhong Yang School of Population Medicine and Public Health Chinese Academy of Medical Sciences&Peking Union Medical CollegeBeijingChina Chinese Preventive Medicine Association BeijingChina Zhejiang Chinese Medical University HangzhouChina Centre for Health Management and Policy Research School of Public HealthCheeloo College of MedicineShandong UniversityJinanChina Chinese Academy of Medical Sciences&Peking Union Medical College BeijingChina

Background: A high-risk prevention strategy is an effective way to fight against human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS). The China AIDS Fund for Non-Governmental Organizations (CAFNGO) was established in 2015 to help social organizations intervene to protect high-risk populations in 176 cities. This study aimed to evaluate the role of social organizations in high-risk population interventions against HIV/AIDS.Methods: This study was based on the CAFNGO program from 2016 to 2020. The collected data included the number and types of social organizations participating in high-risk group interventions and the amount of funds obtained by these organizations each year. We explored the factors influencing the number of newly diagnosed AIDS cases using a spatial econometric model. Furthermore, we evaluated the effectiveness of intervention activities by comparing the percentages of the individuals who initially tested positive, and the individuals who took the confirmatory test, as well as those who retested positive and underwent the treatment.Results: Overall, from 2016 to 2020, the number of social organizations involved in interventions to protect HIV/AIDS high-risk populations increased from 441 to 532, and the invested fund increased from $3.98 to $10.58 million. The number of newly diagnosed cases decreased from 9128 to 8546 during the same period. Although the number of cities with overall spatial correlations decreased, the spatial agglomeration effect persisted in the large cities. Citywise, the number of social organizations (direct effect 19.13), the permanent resident population (direct effect 0.12), GDP per capita (direct effect 17.58;indirect effect -15.38), and passenger turnover volume (direct effect 5.50;indirect effect -8.64) were the major factors influencing new positive cases confirmed through the testing interventions performed by the social organizations. The initial positive test rates among high-risk populations were below 5.5%, the retesting rates among

关键词： Social organization High-risk groups HIV/AIDS Spatial effect

Carbonate-salt-based composite materials for medium- and high-temperature thermal energy storage

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Particuology 2014年第4期12卷 77-81页

作者： zhiwei Ge Feng Ye Hui Cao Guanghui leng Yue Qin Yulong Ding State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of Sciences University of Chinese Academy of Sciences Institute of Particle Science & Engineering University of LeedsLeeds LS2 9JTUK School of Engineering and Technology China University of Geosciences Centre for Cryogenic Energy Storage University of BirminghamEdgbastonBirminghamB15 2TTUK

This paper discusses composite materials based on inorganic salts for medium- and high-temperature thermal energy storage application. The composites consist of a phase change material （PCM）, a ceramic material, and a high thermal conductivity material. The ceramic material forms a microstructural skeleton for encapsulation of the PCM and structural stability of the composites; the high thermal conductivity material enhances the overall thermal conductivity of the composites. Using a eutectic salt of lithium and sodium carbonates as the PCM, magnesium oxide as the ceramic skeleton, and either graphite flakes or carbon nanotubes as the thermal conductivity enhancer, we produced composites with good physical and chemical stability and high thermal conductivity. We found that the wettability of the molten salt on the ceramic and carbon materials significantly affects the microstructure of the composites.

关键词： Thermal energy storage Composite materials Microstructure Thermal conductivity Phase change material

A Scenario-Based Evaluation of COVID-19-Related Essential Clinical Resource Demands in China

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Engineering 2021年第7期7卷 948-957页

作者： Ting Zhang Qing Wang Zhiwei Leng Yuan Yang Jin Yang Fangyuan Chen Mengmeng Jia Xingxing Zhang Weiran Qi Yunshao Xu Siya Chen Peixi Dai Libing Ma Luzhao Feng Weizhong Yang School of Population Medicine and Public Health Chinese Academy of Medical Sciences&Peking Union Medical CollegeBeijing 100730China Division of Infectious Diseases Chinese Center for Disease Control and PreventionBeijing 102206China Department of Respiratory and Critical Care Medicine The Affiliated Hospital of Guilin Medical UniversityGuilin 541001China

The coronavirus disease 2019(COVID-19)pandemic is a global crisis,and medical systems in many countries are overwhelmed with supply shortages and increasing demands to treat patients due to the surge in cases and severe illnesses.This study aimed to assess COVID-19-related essential clinical resource demands in China,based on different scenarios involving COVID-19 spreads and interventions.We used a susceptible–exposed–infectious–hospitalized/isolated–removed(SEIHR)transmission dynamics model to estimate the number of COVID-19 infections and hospitalizations with corresponding essential healthcare resources needed.We found that,under strict non-pharmaceutical interventions(NPIs)or mass vaccination of the population,China would be able to contain community transmission and local outbreaks rapidly.However,under scenarios involving a low intensity of implemented NPIs and a small proportion of the population vaccinated,the use of a peacetime–wartime transition model would be needed for medical source stockpiles and preparations to ensure a normal functioning healthcare system.The implementation of COVID-19 vaccines and NPIs in different periods can influence the transmission of COVID-19 and subsequently affect the demand for clinical diagnosis and treatment.An increased proportion of asymptomatic infections in simulations will not reduce the demand for medical resources;however,attention must be paid to the increasing difficulty in containing COVID-19 transmission due to asymptomatic cases.This study provides evidence for emergency preparations and the adjustment of prevention and control strategies during the COVID-19 pandemic.It also provides guidance for essential healthcare investment and resource allocation.

关键词： COVID-19 Transmission dynamics model Clinical resource demands Vaccination

Moving Mechanism of a High-speed Insect-scale Microrobot via Electro-magnetically Induced Vibration

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Journal of Bionic Engineering 2021年第3期18卷 662-673页

作者： Xinyi Liu zhiwei Liu Yangsheng Zhu Jiaming leng Mingjing Qi Jianmei Huang Xiaojun Yan School of Energy and Power Engineering Beihang UniversityBeijing 100191China National Key Laboratory of Science and Technology on Aero-Engine Aero-thermodynamics Beijing 100191China Beijing Key Laboratory of Aero-Engine Structure and Strength Beijing 100191China Collaborative Innovation Center of Advanced Aero-Engine Beijing 100191China

This paper presents the moving mechanism of a high-speed insect-scale microrobot via electromagnetically induced vibration of two simply supported beams.The microrobot,which has a body length of 12.3 mm and a total mass of 137 mg,can achieve reciprocating lift motion of forelegs without any intermediate linkage mechanisms due to the design of an obliquely upward body tilt angle.The gait study shows that the body tilt angle prevents the forelegs from swinging backward when the feet contact the ground,which results in a forward friction force applied on the feet.During forward movement,the microrobot utilizes the elastic deformation of the simply supported beams as driving force to slide forward and its forelegs and rear legs work as pivots alternatively in a way similar to the movement of soft worms.The gait analysis also indicates that the moving direction of the microrobot is determined by whether its body tilt angle is obliquely upward or downward,and its moving speed is also related to the body tilt angle and as well as the body height.Under an applied AC voltage of 4 V,the microrobot can achieve a moving speed at 23.2 cm s1(18.9 body lengths per second),which is comparable to the fastest speed(20 cm s-1 or 20 body lengths per second)among the published insect-scale microrobots.The high-speed locomotion performance of the microrobot validates the feasibility of the presented actuation scheme and moving mechanism.

关键词： Legged microrobot electromagnetic actuation moving mechanism high-speed

Thermal energy storage:Challenges and the role of particle technology

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Particuology 2014年第4期12卷 2-8页

作者： zhiwei Ge Yongliang Li Dacheng Li Ze Sun Yi Jin Chuanping Liu Chuan Li Guanghui leng Yulong Ding Institute of Process Engineering Chinese Academy of Sciences School of Chemical Engineering University of BirminghamBirmingham B152TTUK East China University of Science & Technology School of Mechanical Engineering University of Science & Technology Beijing

Thermal energy is at the heart of the whole energy chain providing a main linkage between the primary and secondary energy sources. Thermal energy storage （TES） has a pivotal role to play in the energy chain and hence in future low carbon economy. However, a competitive TES technology requires a number of scientific and technological challenges to be addressed including TES materials, TES components and devices, and integration of TES devices with energy networks and associated dynamic optimization. This paper provides a perspective of TES technology with a focus on TES materials challenges using molten salts based phase change materials for medium and high temperature applications. Two key challenges for the molten salt based TES materials are chemical incompatibility and low thermal conductivity. The use of composite materials provides an avenue to meeting the challenges. Such composite materials consist of a phase change material, a structural supporting material, and a thermal conductivity enhancement material. The properties of the supporting material could determine the dispersion of the thermal con- ductivity enhancement material in the salt. A right combination of the salt, the structural supporting material, and the thermal conductivity enhancement material could give a hierarchical structure that is able to encapsulate the molten salt and give a substantial enhancement in the thermal conductivity. Understanding of the structure-property relationships for the composite is essential for the formulation design and fabrication of the composite materials. Linking materials properties to the system level performance is recommended as a key future direction of research.

关键词： Thermal energy storageComposite materialsStructure-property relationshipsRole of particle technology