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Mathematical Model of Drag Torque with Surface Tension in Single-Plate Wet Clutch

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Chinese Journal of Mechanical Engineering 2019年第2期32卷 93-99页

作者： Zengxiong Peng Shihua YUAN National Key Laboratory of Vehicular Transmission Beijing Institute of Technology

Reduction of drag torque in disengaged wet clutches is essential for transmission research because it is one of the potentials of e ciency improvement. Aeration of oil film between two closely rotating plates promotes the decrease of drag torque at high speed region. The e ects of surface tension and static contact angles during aeration are nonnegligible showed by test results. The traditional lubrication model does not adequately predict the experimental results with di erent surface tension and contact angles during aeration. Hence, in this present paper, contact angles between Aluminum and Teflon materials were firstly measured, and the drag torques under two di erent contact angles were examined experimentally. An improved lubrication model of drag torque based on Navier–Stokes equations at the gas-liquid interface was built. The lubrication boundary condition was modified to introduce the e ects of surface tension and contact angle. The model shows that the e ects at the beginning of aeration of oil film are significant. These e ects almost occur at stationary plate due to low Reynolds number and Weber number. The model shows that an increase in the surface tension promotes aeration, but does not a ect the peak drag torque. Increasing contact angle also promotes the aeration, and accelerates the decrease of drag torque. The larger contact angle is, the smaller the peak drag torque will be. A computational fluid dynamics(CFD) model based on volume of fluid(VOF) method was presented to validate the interface shape when aeration occurs. The model prediction has a good agreement with experimental observations for Aluminum plates and Teflon plates. The modified lubrication model of drag torque gives a convenient description of the e ects of surface tension and contact angel, and lays down a frame to understand the beginning of aeration.

关键词： Drag torque Wet clutch Surface tension Contact angle

Co-regulation of circadian clock genes and microRNAs in bone metabolism

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2022年第7期23卷 529-546页

作者： Tingting LI shihua ZHANG Yuxuan YANG Lingli ZHANG Yu yuan Jun ZOU School of Exercise and Health Guangzhou Sport UniversityGuangzhou510500China School of Kinesiology Shanghai University of SportShanghai200438China College of Graduate Education Shandong Sport UniversityJinan250102China

Mammalian bone is constantly metabolized from the embryonic stage,and the maintenance of bone health depends on the dynamic balance between bone resorption and bone formation,mediated by osteoclasts and osteoblasts.It is widely recognized that circadian clock genes can regulate bone metabolism.In recent years,the regulation of bone metabolism by non-coding RNAs has become a hotspot of research.MicroRNAs can participate in bone catabolism and anabolism by targeting key factors related to bone metabolism,including circadian clock genes.However,research in this field has been conducted only in recent years and the mechanisms involved are not yet well established.Recent studies have focused on how to target circadian clock genes to treat some diseases,such as autoimmune diseases,but few have focused on the co-regulation of circadian clock genes and microRNAs in bone metabolic diseases.Therefore,in this paper we review the progress of research on the co-regulation of bone metabolism by circadian clock genes and microRNAs,aiming to provide new ideas for the prevention and treatment of bone metabolic diseases such as osteoporosis.

关键词： Circadian rhythm Circadian clock gene MicroRNAs Bone metabolism

Dynamic Characteristics of Lubrication and Wear Prediction of Slipper/Swash-Plate in Axial Piston Pumps

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Journal of Beijing Institute of Technology 2019年第3期28卷 519-528页

作者： Jichen Zhou Junjie Zhou Chongbo Jing Shihua YUAN Anlin Luo School of Mechanical Engineering Beijing Institute of Technology

A novel dynamic model describing the slipper posture of the swash plate in axial piston pumps is proposed, taking into account the hydrodynamic and squeezing effects, which involves three degrees of freedom. The variation in the lubricating film thickness and the slipper tilt are accurately calculated. The influence of hydrodynamic effects and charging pressure on the slipper lubrication is discussed. The minimum film thickness, the overturning angle and the azimuth angle are obtained.Then, the trajectory of minimum thickness on the friction surface of the swash plate is predicted, the accuracy of which can be verified with the abrasion distribution of an actual swash plate. Research results can predict the durability and provide theoretical help for the design of the slipper.

关键词： slipper/swash-plate pair lubrication dynamic characteristics wear predicting

^(1)O_(2)-activatable Eu^(3+)-afterglow nanoprobe for highly sensitive detection of porphyria in whole blood

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Journal of Rare Earths 2022年第9期40卷 1382-1388,I0002页

作者： Jia Liu Jiamiao Yin Hang yuan Yiyang Zhao shihua Luo Fuyou Li Department of Chemistry State Key Laboratory of Molecular Engineering of PolymersFudan UniversityShanghai 200433China Hangzhou Foreign Languages School Hangzhou 310023China Department of Traumatology Ruijin HospitalSchool of MedicineShanghai Jiao Tong UniversityShanghai 200025China

High-sensitivity detection of porphyrin in blood is very important for the early diagnosis and treatment of porphyria.Based on the advantages of longer luminescence lifetime and lower background interference,organic afterglow molecular porphyrin detection probes were developed,but these probes show poor water solubility and insufficient luminescence intensity.Herein,we present an afterglow nanoprobe(Eu-NP)for porphyria detection in whole blood.The luminescent substance(europium complex)and the organic vinyl co mpound reacted with singlet oxygen(^(1)O_(2))were selected for encapsulation in polystyrene spheres.Eu-NP can respond to^(1)O_(2)produced by porphyrins,and the detection signals can be obtained by the emission of the afterglow Eu^(3+)-emissive nanosensor.Eu-NP can achieve high-sensitivity detection of porphyrin,and the lowest detection limit reaches 0.29μmol/L.The porphyrin detection in whole blood samples is consistent with clinical diagnosis results.Compared with the organic afterglow molecule,the Eu-NPs constructed in this work show a higher signal-to-noise ratio and sensitivity of porphyria detection.

关键词： Porphyria Afterglow Nanoprobe Europium luminescence Whole blood detection Rare earths

Background levels of OCPs,PCBs,and PAHs in soils from the eastern Pamirs,China,an alpine region influenced by westerly atmospheric transport

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Journal of Environmental Sciences 2022年第5期34卷 453-464页

作者： Yang Ding Huanfang Huang Wei Chen yuan Zhang Wenwen Chen Xinli Xing shihua Qi State Key Laboratory of Biogeology and Environmental Geology China University of GeosciencesWuhan 430074China School of Environmental Studies China University of GeosciencesWuhan 430074China Department of Physical and Environmental Sciences University of Toronto ScarboroughTorontoONM1C 1A4Canada State Key Laboratory of Organic Geochemistry Guangzhou Institute of GeochemistryChinese Academy of SciencesGuangzhou 510640China College of Environmental Science and Engineering Guilin University of TechnologyGuilin 541004China

Long-range atmospheric transport(LRAT)plays a crucial role in the occurrence of persis-tent organic pollutants(POPs)in remote regions.When studying the LRAT of POPs on the Tibetan Plateau,westerly-controlled regions have received insufficient attention compared with regions influenced by the Indian monsoon or air flow from East Asia.We investigated the residual levels of POPs in soils from the eastern Pamirs and used air backward trajectory analysis to elucidate the influence of potential source regions via LRAT.Organochlorine pes-ticides(OCPs,mainly comprising DDTs,HCHs,and HCB),polychlorinated biphenyls(PCBs,mainly comprising penta-and hexa-CBs),and polycyclic aromatic hydrocarbons(PAHs,mainly comprising three-and four-ring)were detected at low concentrations of 40-1000,

关键词： Persistent organic pollutants Long-range atmospheric transport Westerlies Tibetan Plateau Remote regions

Factors Influencing Diurnal Variations of Cloud and Precipitation in the Yushu Area of the Tibetan Plateau

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Journal of Meteorological Research 2022年第2期36卷 311-325页

作者： Bangjun CAO shihua LYU Yu ZHANG Xianyu YANG Boliang LI Liang yuan Meilin LI Plateau Atmosphere and Environment Key Laboratory of Sichuan Province School of Atmospheric SciencesChengdu University of Information TechnologyChengdu 610225

Using the cloud radar,ground observations,and ECMWF Reanalysis v5(ERA5)data,we investigate the factors influencing nighttime precipitation during summer in the Yushu area of the Tibetan Plateau(TP).The cloud top height(CTH),cloud base height(CBH),and liquid water content(LWC)are compared between non-precipitation and precipitation days.The results show that the average CTH on precipitation days in Yushu is below 10 km above ground level(AGL)in the daytime,whereas it exceeds 10 km AGL at night,with the maximum at 2300 BT(Beijing Time).The CBH is in-phase with the dewpoint spread.The precipitation intensity and CTH are in-phase with the LWC.The hourly averaged precipitation intensity and convective available potential energy in ERA5 reach their maximums at2100 BT,which is 3 h ahead of their observed counterparts.There is descending motion in the mid day on non-precipitation days,whereas there is ascending motion at night on precipitation days.In addition,the horizontal wind direction in the lower level(below 5000 m)shows clockwise rotation from morning to night.Wind shear occurs in the mid level of the atmosphere,accompanied by a subtropical westerly jet in the upper level.The difference in horizontal wind speed between 200 and 500 hPa is positively related to the LWC,thereby contributing to the formation of upper-level cloud.

关键词： diurnal variation cloud precipitation Tibetan Plateau

Experimental Research and Mathematical Model of Drag Torque in Single-plate Wet Clutch

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Chinese Journal of Mechanical Engineering 2011年第1期24卷 91-97页

作者： yuan shihua PENG Zengxiong JING Chongbo National Key Laboratory of Vehicular Transmission Beijing Institute of Technology Beijing 100081 China

Reduction of drag torque is one of important potentials to improve transmission efficiency.Existing mathematical model of drag torque was not accurate to predict the decrease after oil film shrinking because of the difficulty in modeling the flow pattern between two plates.Flow pattern was considered as laminar flow and full oil film in the gap between two plates in traditional model.Subsequent equivalent circumferential degree model presented an improvement in oil film shrinking due to centrifugal force,but was also based on full oil film in the gap,which resulted difference between model prediction and experimental data.The objective of this paper is to develop an accurate mathematical model for the above problem by using experimental verification.An experimental apparatus was set up to test drag torque of disengaged wet clutch consisting of single friction and separate plate.A high speed camera was used to record the flow pattern through transparent quartz disk plate.The visualization of flow pattern in the clearance was investigated to evaluate the characteristics of oil film shrinking.Visual test results reveal that the oil film begins to shrink from outer radius to inner radius at the stationary plate and only flows along the rotating plate after shrinking.Meanwhile,drag torque decreases sharply due to little contact area between the stationary plate and the oil.A three-dimensional Navier-Stokes （N-S） equation based on laminar flow is presented to model the drag torque.Pressure distributions in radial and circumferential directions as well as speed distributions are deduced.The model analysis reveals that the acceleration of flow in radial direction caused by centrifugal force is the key reason for the shrinking at the constant feeding flow rate.An approach to descript flow pattern was presented on the basis of visual observation.The drag torque predicted by the model agrees well with test data for non-grooved wet clutch.The proposed model enhances the precision for predicting drag torque,and lays down a fr

关键词： wet clutches drag torque mathematical model laminar flow

Trigger control characteristics of fuze-recoil simulation system based on electromagnetic launcher

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Journal of Systems Engineering and Electronics 2017年第3期28卷 563-571页

作者： Wenhao Wang shihua Bi Hongjun Xiang Chao Zhan Xichao yuan School of Aerospace Beijing Institute of TechnologyBeijing 100081China Shijiazhuang Mechanical Engineering College Shijiazhuang 050003China Representative Bureau of the General Equipment Xi’an 710032China

Fuze is the information processing and control unit of the ammunition, so the quality of the fuze becomes one of the most important aspects of ammunition detection. Since using recoil force is a common method to the arm fuze, its dynamic simulation test has always been the focus of the fuze test research. A new fuze recoil environmental simulation method is proposed based on the electromagnetic launcher. Then the trigger control characteristics of the fuze recoil simulation system and the influence of the trigger position on the recoil force are studied. The results of the study show that although the pulse width of the armature force curve can be changed by adjusting the trigger position, due to the limit of the range, there also exists the contradiction that the electromagnetic pulse width gets narrow with the increase of electromagnetic force peak. Thus, it cannot meet the requirements of the fuze launch recoil simulation. In order to make the recoil force close to the actual environment, the multi-stage trigger control characteristics are analyzed, and the influence of trigger position on recoil environmental force characteristics is studied. Then a fuze launch recoil environmental simulation platform is established and continuous electromagnetic force is achieved by using the trigger strategy. Finally, the experiment is performed to simulate the fuze launch recoil environment and show the feasibility and effectiveness of the proposed theoretical analysis. The major research work of this paper includes studying the composition and basic principle of the simulation system, establishing a launch model to analyze the single-stage and multi-stage coil fuze launch recoil characteristics, designing the test device to verify the correctness and validity of the research. This paper draws the conclusions that the feasibility of the fuze launch environmental simulation based on the electromagnetic launcher is verified, the trigger position has a great influence on force peak continuity, the problems of low maximum over

关键词： trigger control fuze-recoil simulation electromagnetic launcher

Drag Torque Prediction Model for the Wet Clutches

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Chinese Journal of Mechanical Engineering 2009年第2期22卷 238-243页

作者： HU Jibin PENG Zengxiong yuan shihua National Key Laboratory of Vehicular Transmission Beijing institute of Technology Beijing 100081 China

Reduction of drag torque in disengaged wet clutch is one of important potentials for vehicle transmission improvement. The flow of the oil film in clutch clearance is investigated. A three-dimension Navier-Stokes(N-S) equation based on laminar flow is presented to model the drag torque. Pressure and speed distribution in radial and circumferential directions are deduced. The theoretical analysis reveals that oil flow acceleration in radial direction caused by centrifugal force is the key reason for the shrinking of oil film as constant feeding flow rate. The peak drag torque occurs at the beginning of oil film shrinking. A variable is introduced to describe effective oil film area and drag torque after oil film shrinking is well evaluated with the variable. Under the working condition, tests were made to obtain drag torque curves at different clutch speed and oil viscosity. The tests confirm that simulation results agree with test data. The model performs well in the prediction of drag torque and lays a theoretical foundation to reduce it.

关键词：湿式离合器预测模型拖曳扭矩曲线转矩 Stokes 速度分布车辆传动