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Numerical analysis of deflection control of a gas plasma jet based on magnetohydrodynamic staggered electrode configuration

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Chinese Journal of Aeronautics 2022年第12期35卷 47-58页

作者： Jingjia ZHANG junwei li Zelin ZHANG Zhijun WEI School of Aerospace Beijing Institute of TechnologyBeijing 100081China

To control the deflection of the gas plasma jet, a new analytical method is proposed based on the Magnetohydrodynamic(MHD) technique. Based on the typical MHD power generation model, the applied voltage is applied to the staggered electrodes, that is, a pair of electrodes on the same side wall are connected to generate an axial current in the channel. Under the action of the magnetic field perpendicular to the direction of the flow, the plasma is subjected to electromagnetic forces perpendicular to these two directions, and the jet is deflected. The computational model including the Navier-Stokes equations coupled with electromagnetic source terms, the electric potential equation and Ohm’s law is solved. The deflection of the gas jet under the action of an electromagnetic field is observed, and the maximum deflection angle is about 14.8°. The influences of the electric field, magnetic field, and conductivity on the jet deflection are studied. Results show that although the influences of these three factors on the deflection are similar, and the effect of increasing the electric field strength is slightly greater, priority should be given to increasing the magnetic field strength from the perspective of reducing energy consumption. The Stuart number is introduced to assess the ability of electromagnetic force to control jet deflection. When the electromagnetic parameters are constant, this solution provides better control of low-density and low-speed fluid flows. The calculation results show that using the staggered electrode method configuration is feasible in terms of controlling the deflection of a plasma jet deflection.

关键词： Deflection angle Deflection control Gas plasma Magnetohydrodynamic Thrust vector

mRNA Vaccines: Possible Tools to Combat SARS-CoV-2

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Virologica Sinica 2020年第3期35卷 259-262页

作者： Changhua Yi Yongxiang Yi junwei li Department of Infectious Diseases The Second Hospital of NanjingThe Affiliated Hospital of Nanjing University of Chinese MedicineNanjing 210003China Public Health and Therapy Center of Nanjing Nanjing 211113China College of Veterinary Medicine Qingdao Agricultural UniversityQingdao 266109China

Coronaviruses are large, enveloped, positive-strand RNA viruses. Several coronaviruses are pathogenic in humans,including severe acute respiratory syndrome coronavirus(SARS-CoV), Middle East respiratory syndrome coron... 详细信息

关键词： respiratory acute Vaccine

Biomechanical energy harvesting technologies for wearable electronics:Theories and devices

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Friction 2024年第8期12卷 1655-1679页

作者： Xiaowen li Xu ZENG junwei li Boyuan li Yu CHEN Xiaosheng ZHANG University of Electronic Science and Technology of China Chengdu 611731China

Wearable biomechanical energy harvesting devices have received a lot of attention recently,benefiting from the rapid advancement of theories and devices in the field of the micro electromechanical system(MEMS).They not only fulfil the requirements for powering wearable electronic devices but also provide an attractive prospect for powering self-powered flexible electronic devices when *** this article,we provide a review of the theories and devices of biomechanical energy harvesting technology for wearable *** different forms of biomechanical energy harvesting mechanisms,including the piezoelectric effect,electromagnetic effect,and electrostatic effect,are investigated in *** fundamental principle of converting other types of energy from the biomechanical environment into electrical energy,as well as the most commonly-used analytical theoretical models,are outlined for each ***,the features,properties,and applications of energy harvesting devices are *** addition,the coupled multi-effect hybrid energy harvesting devices are listed,showing the various possibilities of biomechanical energy harvesting devices for serving as sources,sensors,and ***,we present perspectives on the future trends of biomechanical energy harvesting devices for wearable electronics applications.

关键词： micro electromechanical system(MEMS) nanogenerators biomechanical energy harvesters wearable electronics

A triple-combination nanotechnology platform based on multifunctional RNA hydrogel for lung cancer therapy

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Science China Chemistry 2020年第4期63卷 546-553页

作者： junwei li Dandan Yuan Xiangjiang Zheng Xinyue Zhang Xuemei li Shusheng Zhang Collaborative Innovation Center of Tumor Marker Detection Technology Equipment and Diagnosis-Therapy Integration in Universities of ShandongShandong Province Key Laboratoty of Detection Technology for Tumor MakersSchool of Chemistry and Chemical EngineeringLinyi UniversityLinyi 276005China College of Chemistry Chemical Engineering and Materials ScienceCooperative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of ShandongShandong Normal UniversityJinan 250014China

Conventional cancer combination therapy usually involves systemic delivery of anticancer drugs which may lead to the destruction of normal cells and physiological toxicity due to the lack of targeting ability and toxicity of drug carriers. In the present study, a triple combination nanosystem of gene therapy, chemotherapy and phototherapy delivered by multifunctional RNA nanohydrogels(RNA NHs) was established. By taking the advantages of DNA nanotechnology and rolling circle transcription(RCT), three lung cancer inhibitor microRNA(let-7 a, microRNA 34 a, microRNA 145) hairpins were integrated in one RNA NH nanoparticle, leading to the simultaneous silencing of three targeted m RNAs. Meanwhile, RNA NH carried doxorubicin(DOX, a chemotherapy drug) as well as 5,10,15,20-tetrakis(1-methylpyridinium-4-yl) porphyrin(TMPyP4, a photosensitizer) and delivered these drugs to cancer cells. It was demonstrated that lung cancer inhibitor microRNAs integrated in RNA NHs, DOX and TMPyP4 could play a synergistic anti-cancer role in multi-drug resistance cancer cells. Under the action of aptamer sequence S6 that was modified with cholesterol, the resulting RNA NHs were condensed to feasible size without the assistance of polyelectrolyte condensation reagents and showed cancer-specific cellular targeting. Subsequently, thousands of copies of miRNA together with chemotherapy drug as well as photosensitizer were delivered to cancer cells specifically, and an ideal synergistic treatment effect was achieved in vivo, thus playing a combined role of gene therapy, chemotherapy and phototherapy. Through this study, it can be concluded that the triple combination therapy nanosystem can overcome the multidrug resistance caused by the malfunction of genes in chemotherapy and shows a great potential in the field of multifunctional synergistic cancer treatment.

关键词： RNA nanohydrogel phototherapy drug delivery gene therapy lung cancer

Safety and Considerations of the COVID-19 Vaccine Massive Deployment

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Virologica Sinica 2021年第5期36卷 1097-1103页

作者： junwei li Mingyue Song Deyin Guo Yongxiang Yi Department of Infectious Diseases The Second Hospital of NanjingThe Affiliated Hospital of Nanjing University of Chinese MedicineNanjing210003China Public Health and Therapy Center of Nanjing Nanjing211113China MOE Key Laboratory of Tropical Disease Control Centre for Infection and Immunity StudySchool of MedicineSun Yat-Sen UniversityShenzhen518107China

Emerging and re-emerging infectious diseases represent a significant and growing cause of morbidity and *** vaccination campaigns were carried out,several infectious diseases have been controlled successfully,such as smallpox and poliomyelitis,making vaccination one of the most reliable and cost-effective public health *** the long run,vaccine coverage,whether high or low,has been shown to yield important public health benefits(Weycker et al.2005).Therefore,vaccines play an important role in increasing population immunity,preventing severe infectious diseases。

关键词： immunity diseases vaccination

Experimental and numerical study on pressure oscillation in a combustor with rotary valve

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Chinese Journal of Aeronautics 2021年第5期34卷 298-314页

作者： Yunzhi XI Ningfei WANG junwei li Zhihui ZHANG Lei HAN School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China

A rotary valve coupled in a combustor assembly can generate periodic pressure oscillations inside the combustor and can be used to study the combustion instability in the combustion chamber of a rocket *** paper proposes a cold gas flow experimental system based on a rotary valve and a corresponding rotation model.A 3 D numerical model is proposed to obtain the transient flow inside the rotary valve,and the dynamic mesh technique and User-Defined Functions(UDFs)are adopted to implement a swing motion instead of a rotary *** cold gas flow experiments are carried out at rotating speeds of 75225,and 375 rpm to verify the validity of the numerical *** effects of rotating speed,stroke length ratio and radius of the RED(Rotor Exhaust Duct)on the pressure oscillations are studied using this numerical *** results show that the maximum and peak-to-peak values of the pressure oscillations gradually decrease with increasing rotating *** ratio of the corresponding peak-to-peak value to the maximum pressure(pressure amplitude ratio)is reduced from 1.81 to 0.6%.The stroke length ratio affects the pressure waveform because it leads to a change in the time spent in the non-exhaust *** the stroke length ratio is 0,the waveform closely resembles a sine *** the increase in the stroke length ratio,the pressure waveform exhibits a more square or a triangular wave ***,a high-frequency and high-amplitude pressure oscillation can be obtained by appropriately increasing the radius of the RED.

关键词： Cold gas test Dynamic mesh Numerical simulation Pressure oscillation Rotary valve

Transient flow characteristics and performance of a solid rocket motor with a pintle valve

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Chinese Journal of Aeronautics 2020年第12期33卷 3189-3205页

作者： Anchen SONG Ningfei WANG junwei li Baoyin MA Xinjian CHEN School of Aerospace Beijing Institute of TechnologyBeijing 100081China

The pintle valve is currently the most promising technology among all thrust control methods for solid rocket *** structure and working condition play a critical role in the successful operation of a pintle ***,2D transient simulations of a pintle motor using dynamic meshing are ***-averaged Navier–Stokes equations are solved with the implementation of an RNG k–e turbulence *** cold flow test,emphasis is placed on the effect of pintle structure,and in hot flow test,emphasis is placed on the effect of propellant pressure *** is performed first by comparing the present results with available cold-test experimental *** shows that the transient simulations can provide good predictions for pintle motors with a relative error of less than 2%in terms of the chamber *** can be found that,when the gas supply system is different,the working principles and conditions of pintle motors are *** feedback process in propellant combustion has a significant impact on its operation and the effect on the pintle motor performance of different pintle structures is achieved by different variations in the equivalent throat ***,the pressure exponent is an important parameter in hot flow test and changes of thrust in hot flow test are not monotonic,because changes in the flow field and motor performance are asynchronous.

关键词： Numerical simulation Pintle motor Shock wave Solid propellant rocket Variable thrust

Influence of thermal inhibitor position and temperature on vortex-shedding-driven pressure oscillations

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Chinese Journal of Aeronautics 2013年第3期26卷 544-553页

作者： Su Wanxing li Shipeng Zhang Qiao li junwei Ye Qingqing Wang Ningfei School of Aerospace Engineering Beijing Institute of Technology China Academy of Space Technology

Vortex-acoustic coupling is one of the most important potential sources of combustion instability in solid rocket motors （SRMs）. Based on the Von Karman Institute for Fluid Dynamics （VKI） experimental motor, the influence of the thermal inhibitor position and temperature on vortex-shedding-driven pressure oscillations is numerically studied via the large eddy simulation （LES） method. The simulation results demonstrate that vortex shedding is a periodic process and its accurate frequency can be numerically obtained. Acoustic modes could be easily excited by vortex shedding. The vortex shedding frequency and second acoustic frequency dominate the pressure oscillation characteristics in the chamber. Thermal inhibitor position and gas temperature have little effect on vortex shedding frequency, but have great impact on pressure oscillation amplitude. Pressure amplitude is much higher when the thermal inhibitor locates at the acoustic velocity anti-nodes. The farther the thermal inhibitor is to the nozzle head, the more vortex energy would be dissipated by the turbulence. Therefore, the vortex shedding amplitude at the second acoustic velocity antinode near 3/4L （L is chamber length） is larger than those of others. Besides, the natural acoustic frequencies increase with the gas temperature. As the vortex shedding frequency departs from the natural acoustic frequency, the vortex-acoustic feedback loop is decoupled. Consequently, both the vortex shedding and acoustic amplitudes decrease rapidly.

关键词： Combustion instability Pressure oscillation Solid rocket motor Vortex-acoustic coupling Vortex shedding

An estimation model of time-varying origin-destination flows in expressway corridors based on unscented Kalman filter

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Science China(Technological Sciences) 2009年第7期52卷 2069-2078页

作者： li junwei liN Boliang SUN ZhiHui GENG XueFei State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong UniversityBeijing 100044China School of light Industry Harbin University of CommerceHarbin 150076China

On the basis of measurable time series of mainline and ramp flows from traffic counts and the assumption of travel time distributions, this research presents a dynamic system model and its on-line estimation algorithm for recursive estimation of time-varying origin-destination (OD) matrices in expressway corridors. The proposed model employs a macro-traffic flow model to estimate travel times of OD flows and uses parameters of the traffic model as state variables, which are added to the constrained function of the system. To improve the model efficiency, we revise the travel time distribution based on the feature of normal distribution. The research employs a newly developed filtering technique, called unscented Kalman filter. The proposed model is evaluated with simulation experiments. Numerical analyses with respect to the sensitivity of the selection of initial parameters on the estimation results indicate that the proposed model is sufficiently reasonable and stable for real-world appli-cations.

关键词： OD estimation expressway Kalman filtering algorithm