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Wave-mean flow interaction and its relationship with the atmospheric energy cycle with diabatic heating

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Science China Earth Sciences 2005年第8期48卷 1293-1302页

作者： DUAN Anmin WU Guoxiong State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China

Based on the traditional theory of wave mean flow interaction, an improved quasi-geostrophic Eliassen-Palm flux with diabatic heating included is deduced. It is shown that there exists an intrinsic relation between the atmospheric energy cycle derived by Lorenz and the wave energy transfer derived by Eliassen and Palm. From this relation it becomes clear that the energy propagation process of large-scale stationary wave is indeed a part of Lorenz energy cycle, and the energy transform from mean flow to wave equals the global mass integral of the divergence of local wave energy flux or the global integral of local wave energy. The diagnostic results by using NCEP/NCAR reanalysis data suggest that the classical adiabatic Eliassen-Palm flux relation can present only the wintertime wave energy transformation. For other seasons, however, the diabatic effect must be taken into account.

关键词： wave-mean flow interaction, Eliassen-Palm flux, diabatic heating, Lorenz energy cycle, wave energy.

Removal of shells of multi-wall carbon nanotubes by repeatedly scanning bias voltage

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Science China(Technological Sciences) 2004年第1期47卷 1-5页

作者： LI Qiuhong WANG Taihong Institute of Physics Chinese Academy of Sciences Beijing 100080 China Institute of Physics Chinese Academy of Sciences Beijing 100080 China

Carbon nanotubes can either be metallic or semiconducting, depending on their chirality. IBM converted multi-wall nanotubes into either a metallic or a semiconducting conductor by selectively removing the shells of the MWNTs. This was realized by applying a constant voltage to the tubes in air. Here we report a new method to remove the shells of a single MWNT just by repeatedly scanning the bias voltage in vacuum. Both the direct contact of the outmost shell with the electrodes and the high anisotropy of thermal conductivity help to remove the shells one by one. Keywords multi-wall carbon nanotube - Joule heating - thermal conductivity - breakdown

关键词： multi-wall carbon nanotube, Joule heating, thermal conductivity, breakdown.

Thermal Management of Vehicle Cabins,External Surfaces,and Onboard Electronics:An Overview

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Engineering 2019年第5期5卷 954-969页

作者： Garrett J.Marshall Colin P.Mahony Matthew J.Rhodes Steve R.Daniewicz Nicholas Tsolas Scott M.Thompson Center for Advanced Vehicular Systems Mississippi State UniversityMississippi StateMS 39762USA Department of Mechanical Engineering The University of AlabamaTuscaloosaAL 35487USA Department of Mechanical Engineering Auburn UniversityAuburnAL 36849USA

Reducing heat accumulation within vehicles and ensuring appropriate vehicular temperature levels can lead to enhanced vehicle fuel economy,range,reliability,longevity,passenger comfort,and *** in vehicle thermal management remain key as new technologies,consumer demand,societal concerns,and government regulations emerge and *** study summarizes several recent advances in vehicle thermal management technology and modeling,with a focus on three key areas:the cabin,electronics,and exterior components of ***-related topics covered include methods for reducing thermal loads and improving heating,ventilation,and air-conditioning(HVAC)systems;and advancements in window glazing/tinting and vehicle surface *** the thermal management of electronics,including batteries and insulated-gate bipolar transistors(IGBTs),active and passive cooling methods that employ heat pipes,heat sinks,jet impingement,forced convection,and phase-change materials are ***,efforts to model and enhance the heat transfer of exterior vehicular components are reviewed while considering drag/friction forces and environmental *** advances in the field of vehicle thermal management,challenges still exist;this article provides a broad summary of the major issues,with recommendations for further study.

关键词： Vehicle design Automotive engineering Electronics packaging Heat pipes Climate control heating, ventilation, and air-conditioning Battery cooling Thermal soak

Dynamical diagnosis of the breakup of the stratospheric polar vortex in the Northern Hemisphere

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Science China Earth Sciences 2007年第9期50卷 1369-1379页

作者： WEI Ke1,2, CHEN Wen1 & HUANG RongHui1 1 Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100080, China 2 Graduate University of the Chinese Academy of Sciences, Beijing 100049, China Center for Monsoon System Research Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100080 China Graduate University of the Chinese Academy of Sciences Beijing 100049 China Center for Monsoon System Research Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100080 China

The research on climate change in polar regions, especially on the role of polar in the global climate system, has gain unprecedented level of interest. It has been the key scientific issue of the International Polar Year program (IPY, 2007—2008). In this paper, we dealt with the debate upon the breakup time of the stratospheric polar vortex in boreal spring. An observational study of the relation between stratospheric polar vortex breakup and the extra-tropical circulation was performed. The mean breakup date—when the winter westerly at the core of polar jet turns to summer easterly—is about April 10. The breakup time has large interannual variation with a time span of about 2 months. It also has a long-term trend with the 1990s and 2000s witnessing more and more late breakups of polar vortex. Composite of wind speed at the core of polar jet for the extremely early and late breakup years shows that late years have two periods of westerly weakening while early breakup years have only one. The flrst weakening in the late years happens in middle January with wind speed dropping sharply from more than 40 m s^(-1) to about 15 m s^(-1). This is accompanied with anomalous activities of planetary waves in both stratosphere and troposphere; while the second weakening in the late breaking years is mainly the results of diabatic heating with very weak wave activities. In early breakup years, the transition from westerly to easterly is rapid with wind speed dropping from more than 30 m s^(-1) to less than -10 m s^(-1) within a month. This evolution is associated with a strong bidirectional dynamical coupling of the stratosphere and troposphere. The circulation anomalies at low troposphere are also analyzed in the extremely early and late breakup years. It shows that there are significant differences between the two kinds of extreme years in the geopotential height and temperature composite analysis, indicating the dynamical coupling of stratosphere and troposphere with the evo

关键词： stratospheric polar vortex, wave-flow interaction, diabatic heating, final breakup, stratosphere-troposphere coupling