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Friction 2024年第2期12卷 271-290页

作者： Shaohua LI Xiaohui LIN Shuyun JIANG School of Mechanical Engineering Southeast UniversityNanjing 211189China

Bubbly oil lubrication is a type of lubrication method.However,the lubrication model of the bubbly oil has not been thoroughly considered.This paper aims to investigate the modelling for bubbly oil lubrication considering the interfacial effect and thermal effect,and a theoretical model is established based on the theory of multiphase mixtures.The interfacial and thermal effects on the static characteristics of a thrust bearing are analyzed.A test rig for the thrust bearing is developed to measure the static characteristics of the bearing under bubbly oil lubrication.The results show that the bearing static characteristics,i.***.bearing temperature rise,film thickness,friction torque,and volume flow,increase with consideration of three interfacial effects;the bearing temperature rise increases but the film thickness,friction torque,and volume flow rate decrease with consideration of the three thermal effects;the thermal effect on the bearing static characteristics is greater than the interfacial effect.

关键词： bubbly oil lubrication theory of multiphase mixtures interfacial effect thermal effect fluid bearing

thermal effect of the accumulated water with different depths on permafrost subgrade in cold regions

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Advances in Climate Change Research 2023年第2期14卷 179-189页

作者： Er-Xing PENG Xiao-Ying HU Yu SHENG Ji-Chun WU Wei CAO Qi-Fan YANG Xiang-Bin ZHAO Ji CHEN State Key Laboratory of Frozen Soil Engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China School of Civil Engineering Lanzhou University of TechnologyLanzhou 730050China Beiluhe Observation and Research Station on Frozen Soil Engineering and Environment in Qinghai‒Tibet Plateau State Key Laboratory of Frozen Soil EngineeringNorthwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China

In cold regions,the thermal effect of accumulated water on underlying permafrost and permafrost subgrade remains a significant hazard causing engineering risks.Water depth of accumulated water may be an important influence factor of permafrost thermal stability,but there is lack of qualitative and quantitative research about that.In this study,equivalent thermal conductivity theory and solid heat transfer theory have been used to establish the calculation model for simulating heat transfer in water and soil.Thereafter,the accuracy and reliability of the calculation model are checked by monitored data and subsequently used to analyze the thermal erosion of water on underlying permafrost and permafrost under the embankment.These simulation results show that shallow water can protect permafrost and deeper water disrupts the thermal stability of underlying permafrost.The thermal effect extent of water is primarily determined by its depth,and the concept of critical depth and stable depth of accumulated water has been proposed.Moreover,the temperature field of permafrost under embankment can be changed by the slope toe water.In addition,the thermal effect range of the slope toe water is limited by the thermal influence radius,which increases with the depth of standing water.These findings provide support as well as a fundamental base for environmental issues arising from the accumulated water.These observations will,thus,also be valuable to further engineering environment studies in cold regions.

关键词： Accumulated water Water depth Permafrost Embankment thermal effect

The action mechanism of the work done by the electric field force on moving charges to stimulate the emergence of carrier generation/recombination in a PN junction

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Applied Mathematics and Mechanics(English Edition) 2024年第6期45卷 1001-1014页

作者： Lingyun GUO Yizhan YANG Wanli YANG Yuantai HU Department of Mechanics School of Aerospace EngineeringHubei Key Laboratory of Engineering Structural Analysis and Safety AssessmentHuazhong University of Science and TechnologyWuhan 430074China

It is discovered that the product of the current and the electric field in a PN junction should be regarded as the rate of work(power)done by the electric field force on moving charges(hole current and electron current),which was previously misinterpreted as solely a Joule heating effect.We clarify that it is exactly the work done by the electric field force on the moving charges to stimulate the emergence of non-equilibrium carriers,which triggers the novel physical phenomena.As regards to Joule heat,we point out that it should be calculated from Ohm’s law,rather than simply from the product of the current and the electric field.Based on this understanding,we conduct thorough discussion on the role of the electric field force in the process of carrier recombination and carrier generation.The thermal effects of carrier recombination and carrier generation followed are incorporated into the thermal equation of energy.The present study shows that the exothermic effect of carrier recombination leads to a temperature rise at the PN interface,while the endothermic effect of carrier generation causes a temperature reduction at the interface.These two opposite effects cause opposite heat flow directions in the PN junction under forward and backward bias voltages,highlighting the significance of managing device heating phenomena in design considerations.Therefore,this study possesses referential significance for the design and tuning on the performance of piezotronic devices.

关键词： piezoelectric semiconductor(PS) work done by electric field force thermal effect piezotronic device resistivity conductivity

thermal effect on endurance performance of 3-dimensional RRAM crossbar array

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Chinese Physics B 2016年第5期25卷 253-257页

作者：卢年端孙鹏霄李泠刘琦龙世兵吕杭炳刘明 Key Laboratory of Microelectronics Devices&Integrated Technology Institute of Microelectronics of Chinese Academy of SciencesBeijing 100029China Jiangsu National Synergetic Innovation Center for Advanced Materials Nanjing 210000China

Three-dimensional（3D） crossbar array architecture is one of the leading candidates for future ultra-high density nonvolatile memory applications. To realize the technological potential, understanding the reliability mechanisms of the3 D RRAM array has become a field of intense research. In this work, the endurance performance of the 3D 1D1 R crossbar array under the thermal effect is investigated in terms of numerical simulation. It is revealed that the endurance performance of the 3D 1D1 R array would be seriously deteriorated under thermal effects as the feature size scales down to a relatively small value. A possible method to alleviate the thermal effects is provided and verified by numerical simulation.

关键词： 3-dimensional resistive random access memory（RRAM） thermal effect endurance performance

thermal effect of the Cable-Stayed Bridge Tower

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Wuhan University Journal of Natural Sciences 2003年第4A期8卷 1121-1125页

作者： Zhang Hai-long, Li Jun, Liu Chang-guo, Jiang Tian-hua, Wei jun School of Civil Engineering and Mechanics, Huazhong University of Science and Technology, Wuhan 430074, Hubei, China School of Civil Engineering and Mechanics Huazhong University of Science and Technology Wuhan Hubei China

This paper studies the thermal effect of the cable-stayed bridge tower based on full time accurate measurement and finite element analysis on Xiantao Hanjiang River Highway Bridge. The measured results and the displacement variation of top tower show that the tower rotates periodically when it is exposed in sunshine. But the tower column will not decline when there is no sunshine. In spite of in winter or in summer, the period when the tower column changed smallest is from 0∶00 am to 5∶00 am. The time period when the tower column has maximum deviation lags behind the time when the tower column has maximum temperature difference, and this phenomenon is obvious in winter. The conclusions also have directive value in predicting the tower deformations and their directions in construction control of cable-stayed bridge, and in verifying the finite element program.

关键词： bridge tower thermal effect deformation full time measurement

thermal effect of Ge_2Sb_2Te_5 in phase change memory device

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Chinese Physics B 2014年第8期23卷 121-124页

作者：李俊焘刘波宋志棠任堃朱敏徐佳任佳栋冯高明任万春童浩 State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information TechnologyChinese Academy of Sciences University of the Chinese Academy of Sciences Semiconductor Manufacturing International Corporation

In the fabrication of phase change random access memory （PRAM） devices, high temperature thermal processes are inevitable. We investigate the thermal stability of GezSb2Te5 （GST） which is a prototypical phase change material. After high temperature process, voids of phase change material exist at the interface between Ge2Sb2Te5 and substrate in the initial open memory cell. This lower region of GezSb2Te5 is found to be a Te-rich phase change layer. Phase change memory devices are fabricated in different process conditions and examined by scanning electron microscopy and energy dispersive X-ray. It is found that hot-chuck process, nitrogen-doping process, and lower temperature inter-metal dielectric （IMD） deposition process can ease the thermal impact of line-GST PRAM cell.

关键词： phase change memory Ge2Sb2Te5 thermal effect failure analysis

Experimental investigation of thermal effect on cavitation characteristics in a liquid rocket engine turbopump inducer

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Chinese Journal of Aeronautics 2021年第8期34卷 48-57页

作者： Chunmin WANG Le XIANG Yonghua TAN Hui CHEN Kaifu XU Northwestern Polytechnical University Xi'an 710072China Xi’an Aerospace Propulsion Institute Xi'an 710100China Academy of Aerospace Propulsion Technology Xi'an 710100China

The objective of this paper is to investigate the effect of water temperature on cavitation characteristics in a turbopump inducer,a series of experiments at different temperatures have been conducted in a newly developed visualization test facility.It is found that higher temperature shows little influence on the non-cavitation performance and breakdown characteristic in the investigated range.The relationship between cavitation development and pressure fluctuation has been discussed in detail.Higher temperature displays a remarkable stabilization effect on the cavitation excited pressure.In particular,the inception cavitation numbers of both the super-synchronous rotating cavitation and synchronous rotating cavitation are decreased at higher temperatures,and the corresponding frequencies are not affected,while the amplitudes are distinctly reduced,and the occurrence range of synchronous rotating cavitation is significantly narrowed.A generalized RayleighPlesset equation has been employed to account for the thermal effect on the bubble development,which may provide a deep insight in understanding the experimental results.thermal effect is found to act as a remarkable dissipation mechanism to suppress the bubble growth,smooth the collapse.In particular,the excited pressure during collapse is smaller at higher temperatures,which may lead to the stabilization effect of high temperature in this study.

关键词： Bubble dynamic Cavitation instability Inducer thermal effect Visualization experiment

Numerical Calculation of thermal effect on Cavitation in Cryogenic Fluids

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Chinese Journal of Mechanical Engineering 2012年第6期25卷 1176-1183页

作者： SHI Suguo WANG Guoyu School of Mechanical Engineering Beijing Institute of TechnologyBeijing 100081China

A key design issue related to the turbopump of the rocket engine is that cavitation occurs in cryogenic fluids when the fluid pressure is lower than the vapor pressure at a local thermodynamic state. Cavitation in cryogenic fluids generates substantial thermal effects and strong variations in fluid properties, which in turn alter the cavity characteristics. To date, fewer investigate the thermal effect on cavitation in cryogenic fluids clearly by the numerical methods due to the difficulty of the heat transfer in the phase change process. In order to study the thermal effect on cavitation in cryogenic fluid, computations are conducted around a 2D quarter caliber hydrofoil in liquid nitrogen and hydrogen respectively by implementing modified Merkle cavitation model, which accounts for the energy balance and variable thermodynamic properties of the fluid. The numerical results show that with the thermal effect, the vapour content in constant location decreases, the cavity becomes more porous and the interface becomes less distinct which shows increased spreading while getting shorter in length. In the cavity region, the temperature around the cavity depresses due to absorb the evaporation latent heat and the saturation pressure drops. When the vapour volume fraction is higher, the temperature depression and pressure depression becomes larger. It is also observed that a slight temperature rise is found above the reference fluid temperature at the cavity rear end attributed to the release of latent heat during the condensation process. When the fluid is operating close to its critical temperature, thermal effects on cavitation are more obviously in both the liquid nitrogen and hydrogen. The thermal effect on cavitation in liquid hydrogen is more distinctly compared with that in liquid nitrogen due to the density ratio, vapour pressure and other variable properties of the fluid. The investigation provides aid for the design of the cryogenic pump of the liquid rocket.

关键词： thermal effect cavitation cryogenic fluid numerical simulation

Impact of the thermal effect on the load-carrying capacity of a slipper pair for an aviation axial-piston pump

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Chinese Journal of Aeronautics 2018年第2期31卷 395-409页

作者： Hesheng TANG Yaobao YIN Yan REN Jiawei XIANG Jun CHEN School of Mechanical Engineering WenZhou University School of Mechanical Engineering Tongji University Sany Heavy Industry Co. Ltd

A thermal hydraulic model based on the lumped parameter method is presented to analyze the load-carrying capacity of a slipper pair in an aviation axial-piston pump under specified operating conditions. Both theoretical and experimental results are presented to demonstrate the validity of the thermal hydraulic model. The results illustrate that the squeezing force and thermal wedge bearing force are the main factors that affect the film thickness and load-carrying capacity.At high oil temperature and high load pressure, the film thickness decreases with increasing clamping force due to a combined action of the squeezing bearing force and the thermal wedge bearing force, but the load-carrying capacity will increase. An increase of the film thickness is proven to be beneficial under high shaft rotational speed but especially dangerous as it strongly increases the ripple amplitude of the film thickness, which leads to decreasing the load-carrying capacity. The structural parameters of the slipper can be optimized to achieve desired performance, such as the slipper radius ratio and orifice length diameter ratio. To satisfy the requirement of the load-carrying capacity, the slipper radius ratio should be selected from 1.4 to 1.8, and the orifice length diameter ratio should be selected from 4 to 5.

关键词： Aviation axial piston pumpFluid lubrication Load-carrying capacity Slipper pair thermal effect

Bionic Leaf Simulating the thermal effect of Natural Leaf Transpiration

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Journal of Bionic Engineering 2014年第1期11卷 90-97页

作者： Zhi Yuan Hong Ye Shimin Li Department of thermal Science and Energy Engineering University of Science and Technology of China Hefei 230027 P. R. China

We proposed a kind of bionic leaf to simulate the thermal effect of leaf transpiration. The bionic leaf was firstly designed to be composed of a green coating, a water holding layer, a Composite Adsorbent （CS） layer and an adsorption-desorption rate controlling layer. A thermophysical model was established for the bionic leaf, and the dynamic simulation results reveal that the water holding layer is not necessary; a CS of high thermal conductivity should be selected as the CS layer; the adsorp- tion-desorption rate controlling layer could be removed due to the low adsorption-desorption rate of the CS; and when CaC12 mass fraction of the CS reaches 40%; the bionic leaf could simulate the dynamic thermal behavior of the natural leaf. Based on the simulation results, we prepared bionic leaves with different CaC12 content. The thermographies of the bionic leaf and the natural leaf were shot using the Infrared thermal Imager. The measured average radiative temperature difference between the bionic and natural leaves is less than 1.0 ℃.

关键词： bionic leaf composite sorbent transpiration thermal effect leaf temperature