The Regional Surface Heating Field over the Heterogeneous Landscape of the Tibetan Plateau Using MODIS and In Situ Data

In this study, a parameterization scheme based on Moderate Resolution Imaging Spectroradiometer （MODIS） data and in-situ data was tested for deriving the regional surface heating field over a heterogeneous landscape. As a case study, the methodology was applied to the whole Tibetan Plateau （TP） area. Four images of MODIS data （i.e., 30 January 2007, 15 April 2007, 1 August 2007, and 25 October 2007） were used in this study for comparison among winter, spring, summer, and autumn. The results were validated using the observations measured at the stations of the Tibetan Observation and Research Platform （TORP）. The results show the following： （1） The derived surface heating field for the TP area was in good accord with the land-surface status, showing a wide range of values due to the strong contrast of surface features in the area. （2） The derived surface heating field for the TP was very close to the field measurements （observations）. The APD （absolute percent difference） between the derived results and the field observations was 〈10%. （3） The mean surface heating field over the TP increased from January to April to August, and decreased in October. Therefore, the reasonable regional distribution of the surface heating field over a heterogeneous landscape can be obtained using this methodology. The limitations and further improvement of this method are also discussed.

Variations in Surface Urban Heat Island and Urban Cool Island Intensity:A Review Across Major Climate Zones

The climate has an impact on the urban thermal environment,and the magnitude of the surface urban heat island(SUHI)and urban cool island(UCI)vary across the world’s climatic zones.This literature review investigated:1)the variations in the SUHI and UCI intensity under different climatic backgrounds,and 2)the effect of vegetation types,landscape composition,urban configuration,and water bodies on the SUHI.The SUHI had a higher intensity in tropical(Af(tropical rainy climate,Köppen climate classification),Am(tropical monsoon climate),subtropical(Cfa,subtropical humid climate),and humid continental(Dwa,semi-humid and semi-arid monsoon climate)climate zones.The magnitude of the UCI was low compared to the SUHI across the climate zones.The cool and dry Mediterranean(Cfb,temperate marine climate;Csb,temperate mediterranean climate;Cfa)and tropical climate(Af)areas had a higher cooling intensity.For cities with a desert climate(BWh,tropical desert climate),a reverse pattern was found.The difference in the SUHI in the night-time was greater than in the daytime for most cities across the climate zones.The extent of green space cooling was related to city size,the adjacent impervious surface,and the local climate.Additionally,the composition of urban landscape elements was more significant than their configuration for sustaining the urban thermal environment.Finally,we identified future research gaps for possible solutions in the context of sustainable urbanization in different climate zones.

Calculation and experimental study on heating temperature field of super-high strength aluminum alloy thick plate

Stepped heating treatment has been applied to aluminum alloy thick plate to improve the mechanical performance and corrosion resistance.Accurate temperature control of the plate is the difficulty in engineering application.The heating process,the calculation of surface heat transfer coefficient and the accurate temperature control method were studied based on measured heating temperature for the large-size thick plate.The results show that,the temperature difference between the surface and center of the thick plate is small.Based on the temperature uniformity,the surface heat transfer coefficient was calculated,and it is constant below300°C,but grows greatly over300°C.Consequently,a lumped parameter method(LPM)was developed to predict the plate temperature.A stepped solution treatment was designed by using LPM,and verified by finite element method(FEM)and experiments.Temperature curves calculated by LPM and FEM agree well with the experimental data,and the LPM is more convenient in engineering application.

THERMAL EFFECTS OF BUILDING′S EXTERNAL SURFACES IN CITY——Characteristics of Heat Flux into and out of External Wall Surfaces

This study examined the thermal effects of building′s external wall surfaces, using observational data of spatial-temporal distribution of surface temperature, air temperature, and heat flux into and out of external surface. Results indicate that external wall surface temperature and nearby air temperature vary with the change of orientation, height and season. In general, the external wall surface temperature is lower near the ground, and is higher near the roof, than nearby air temperature. But north wall surface temperature is mostly lower than nearby air temperature at the same height; south wall surface temperature during the daytime in December, and west wall surface temperature all day in August, is respectively higher than nearby air temperature. The heat fluxes into and out of external wall surfaces show the differences that exist in the various orientations, heights and seasons. In December, south wall surface at the lower sites emits heat and north wall surface at the higher sites absorbs heat. In April, all external wall surfaces, emit heat near the ground and absorb heat near the roof. In August, west wall surface all day emits heat, and other wall surfaces just show the commensurate behavior with that in April.

Impact of Tibetan Plateau surface heating field intensity on Northern Hemispherical general circulations and weather and the climate of China

The basic climatic characteristics about the Tibetan Plateau surface heating field intensity (TPSHFI) and its anomalous change trend are analyzed by using Lhasa, Yushu and Wu-daoliang as the representatves of north-part, east-part and mid-north part of the Tibetan Plateau, respectively. The impact of heating intensity anomalism on NH general circulation and the climate of China is diagnosed.

Remote Sensing Parameterization of Land Surface Heat Fluxes over Arid and Semi-arid Areas

Dealing with the regional land surfaces heat fluxes over inhomogeneous land surfaces in arid and semi-arid areas is an important but not an easy issue. In this study, one parameterization method based on satellite remote sensing and field observations is proposed and tested for deriving the regional land surface heat fluxes over inhomogeneous landscapes. As a case study, the method is applied to the Dunhuang experimental area and the HEIFE (Heihe River Field Experiment, 1988-1994) area. The Dunhuang area is selected as a basic experimental area for the Chinese National Key Programme for Developing Basic Sciences: Research on the Formation Mechanism and Prediction Theory of Severe Climate Disaster in China (G1998040900, 1999-2003). The four scenes of Landsat TM data used in this study are 3 June 2000, 22 August 2000, and 29 January 2001 for the Dunhuang area and 9 July 1991 for the HEIFE area. The regional distributions of land surface variables, vegetation variables, and heat fluxes over inhomogeneous landscapes in arid and semi-arid areas are obtained in this study.

Optimization of heat transfer in the thermal Marangoni convective flow of a hybrid nanomaterial with sensitivity analysis

The heat transfer rate of the thermal Marangoni convective flow of a hybrid nanomaterial is optimized by using the response surface methodology(RSM).The thermal phenomenon is modeled in the presence of a variable inclined magnetic field,thermal radiation,and an exponential heat source.Experimentally estimated values of the thermal conductivity and viscosity of the hybrid nanomaterial are utilized in the calculation.The governing intricate nonlinear problem is treated numerically,and a parametric analysis is carried out by using graphical visualizations.A finite difference-based numerical scheme is utilized in conjunction with the 4-stage Lobatto IIIa formula to solve the nonlinear governing problem.The interactive effects of the pertinent parameters on the heat transfer rate are presented by plotting the response surfaces and the contours obtained from the RSM.The mono and hybrid nanomaterial flow fields are compared.The hybrid nanomaterial possesses enhanced thermal fields for nanoparticle volume fractions less than 2%.The irregular heat source and the thermal radiation enhance the temperature profiles.The high level of the thermal radiation and the low levels of the exponential heat source and the angle of inclination(of the magnetic field)lead to the optimized heat transfer rate(Nux=7.46275).

Solidification of Al alloys under electromagnetic field

New theories and technology in the electromagnetic field were put forward about DC casting of Al alloys, including the fundamental research works, i.e, effects of the electromagnetic field on solidus and liquidus, macrosegregation of the main alloying elements, microstructures, content of alloying elements in grains and grain size after solidification under electromagnetic field, and also including a new process DC casting under low frequency electromagnetic field(LFEMC), which can refine microstructure, eliminate macrosegregation, increase the content of alloying elements within grains, decrease the residual stress, avoid cracks and improve surface quality, and another new process DC casting under low frequency electromagnetic vibration(LFEVC), which is a high effective method for grain refining.

超声混粉电火花加工热力学仿真及表面形貌研究

为了研究超声振动和混粉对电火花加工的影响,基于传热理论,结合超声和混粉特性建立了超声混粉电火花传热模型。基于建立的传热模型对超声混粉电火花加工去除材料过程进行瞬态热力学仿真,并通过实验验证了仿真结果的准确性。通过仿真和实验分析了普通电火花、超声电火花、混粉电火花和超声混粉电火花四种加工方式,结果表明超声混粉电火花加工效率比普通电火花加工效率提高了23%。加入混粉和施加超声可以减少加工表面积碳,提高表面质量;可以使放电凹坑变得更加规则,使表面粗糙度降低。混粉电火花加工相对于普通电火花加工其表面粗糙度平均降低了8.9%,超声混粉电火花表面粗糙度相对于普通电火花平均降低了4.3%。

磁电弹性材料含正六边形纳米缺陷的表面效应研究

在磁电弹性材料断裂力学框架下,利用表面弹性理论和解析函数边值理论,解析研究了反平面机械载荷、面内电载荷和磁载荷耦合作用下磁电弹性体中正六边形孔边均布六条等长裂纹的Ⅲ型断裂力学问题,确定了考虑表面效应时纳米尺寸裂纹问题的精确解.基于以上解析解,通过数值算例揭示了表面效应、缺陷几何参数及所施加的损坏载荷分别在两种理想裂纹面电磁条件假设下对断裂参数的影响规律.研究发现:考虑表面效应时影响裂纹扩展的因素与经典弹性理论解答明显不同.各个物理分量呈现出显著的尺寸依赖效应,但随着缺陷尺寸的增加,表面效应的影响呈下降趋势,并趋于经典弹性理论值.研究可为该材料应用于微纳米结构和微机电系统提供理论指导.

CHARACTERISTICS OF THE SURFACE AND ATMOSPHERIC HEATING FIELDS OVER QINGHAI-XIZANG PLATEAU FOR THE PERIOD FROM AUGUST 1982 TO JULY 1983

The surface and atmospheric heating fields over the Qinghai-Xizang Plateau are computed by using the observational data of solar radiation during 1982—1983.The mian results are as follows:The central and northern parts of the Plateau act as heat sinks in winter from November to January.Both eastern and south- ern parts of the Plateau are of heat sources.In summer,the main part of the Plateau acts as a strong heat source,and the center of the heating field is in the southeastern Plateau.However the main part of the Plateau acts as a heat sink for the atmospheric heating fields from October to March.The maximum intensity of the atmospheric heat sink over the central Plateau appears in December and January.From April to September,the main part of the Plateau acts as a heat source for the atmospheric heating fields.

Heat transfer model for microwave hot in-place recycling of asphalt pavements

In order to solve for temperature fields in microwave heating for recycling asphalt mixtures, a two-dimensional heat transfer model for the asphalt mixtures within the heating range is built based on the theory of unsteady heat conduction. Four onedimensional heat transfer models are established for the asphalt mixtures outside the heating range, which are simplified into four half-infinite solids. The intensity of the radiation electric field is calculated through experiment by using heating water loads. It is suggested that the mathematical model of boundary conditions can be established in two ways, which are theoretical deduction and experimental reverse. The actual temperature field is achieved by fitting temperatures of different positions collected in the heating experiment. The simulant temperature field, which is solved with the Matlab PDE toolbox, is in good agreement with the actual temperature field. The results indicate that the proposed models have high precision and can be directly used to calculate the temperature distribution of asphalt pavements.

磁电弹性材料含纳米尺度唇口次生两不对称裂纹的反平面问题

基于Gurtin-Murdoch表面弹性理论和磁电弹性(MEE)理论,利用解析函数的保角映射技术,研究了反平面机械载荷和面内电磁载荷作用下,MEE材料中含有纳米尺度唇口次生两不对称裂纹的断裂行为,给出了缺陷(裂纹和唇口孔)周围广义MEE应力场和裂纹尖端MEE场强度因子以及能量释放率的解析解.在特殊条件下,所得结果退化为已有结果或者给出新的结果.数值算例揭示了缺陷表面效应对裂纹尖端MEE场强度因子的影响与纳米圆孔半径、唇口孔的大小、唇口次生裂纹大小,以及外加的机-电-磁载荷有关,也揭示了考虑表面效应时,无量纲能量释放率随唇口宽度、无穷远处机械载荷、电载荷和磁载荷的变化而变化.

永磁交变磁场平面磁粒研磨试验研究

目的探究永磁交变磁场下平面磁粒研磨质量的影响因素,增强加工区域的磁场变化,使磁性磨粒的加工轨迹多样化,提高研磨效率和研磨效果。方法设计永磁交变磁场取代传统平面磁粒研磨中的恒定磁场源,并采用磁场模拟软件对永磁交变磁场进行仿真,对不同状态下磁场的分布进行分析,参考仿真结果选取实验参数;使用产生径向磁场的环形磁铁作为磁场发生源,导磁性良好的纯铁作为导磁骨架,通过磁路的开放和闭合实现磁场的交变;使用步进电机及脉冲发生器调节研磨磁场,进而调节磁极交变频率;通过试验对比不同参数下对SUS304不锈钢的研磨效果,在研磨间隙为1.5mm的条件下,对比不同研磨时间、不同磨粒目数、不同主轴转速对工件表面质量的影响,使用触针式表面粗糙度测量仪和超景深3D电子显微镜检测对比试验前后试件的表面质量并对仿真结果进行验证。结果对比永磁交变磁场不同磁场分布状态仿真图,发现永磁交变磁场研磨区域场强变化显著,场强峰值时磁感应强度较高;磁性磨粒随离心力与永磁交变磁极状态的变化做周期性运动,使研磨轨迹复杂化。在研磨时间为40min、主轴转速为245 r/min、磨粒粒径为60目条件下,SUS304不锈钢板经研磨后,表面粗糙度由原始的0.312μm降至0.060μm。结论永磁交变磁场在提高加工区域磁感应强度的同时,使磁场发生周期性变化进而使磁性磨粒在加工区域做周期性运动,复杂化研磨轨迹促进了磨粒的更新,相比于恒定磁场磁粒研磨工艺,永磁交变磁场提高了研磨效率与研磨效果。

北京奥林匹克公园中心区广场下垫面热环境特征及材质优化研究

【目的】城市中大面积且连续的硬质下垫面是近地表热环境恶化的重要原因之一,下垫面反照率的增加通常能使地表环境变得凉爽。通过研究下垫面热环境特征与环境温度的关系,可以为缓解城市地表升温提供理论依据。【方法】以北京奥林匹克公园中心区广场为例,实测6种典型下垫面(沥青、透水混凝土、砖、花岗岩、砾石、草地)的地表温度,对下垫面热环境特征及温度区间进行相关性研究,并结合ENVI-met数值模拟法探究整体反照率对热环境的具体影响。【结果】硬质下垫面在四季均能加热空气,在相同环境条件下,所有参与研究的硬质下垫面中沥青最热,花岗岩最凉爽;在不同下垫面类型中,颜色深浅对表面温度的影响高于材料类型与表面粗糙程度差异的影响;在单日内不同的测试时间段,日温度均值较低的深色下垫面在某一时刻的瞬时温度可能会高于日温度均值较高的浅色下垫面;在一定区间内增加场地整体反照率可有效降温,场地温度降幅随反照率上升呈先升后降的单峰趋势,且研究区域内整体反照率约为0.56时热环境改善效益最佳。【结论】提出硬质下垫面材料选择及设置建议,为北京公共空间硬质下垫面设计提供参考和依据。

辐射式电加热器中电加热芯的优化布置研究

为降低辐射式电加热器的电加热芯表面温度以延长电加热器寿命,本文设计了四种电加热芯布置方式,采用Fluent模拟研究了电加热芯布置方式对其电加热器内部温度场和表面温度的影响规律。结果表明:在满足物料出口温度要求条件下,各方案电加热芯与氮气区域温度差分别为:方案一约为190℃,方案二约为210℃,方案三约为200℃,方案四约为180℃,方案四温度差相比其余方案降低10~30℃,温度场更加稳定;各方案电加热芯平均温度:方案一约为910℃;方案二约为950℃;方案三约为905℃;方案四约为860℃,电加热芯温度相比其他布置形式降低40~90℃。

磁场对钕铁硼表面电沉积Ni镀层性能的影响

目的研究不同磁场参数对钕铁硼表面电沉积Ni镀层性能的影响。方法以烧结钕铁硼(NdFeB)为基体,采用磁场辅助电沉积方法在其表面镀覆Ni层。利用扫描电镜(SEM)、EDS能谱仪、X射线衍射仪(XRD)分析镀层的表面形貌、元素组成和微观结构,通过电化学工作站对Ni镀层进行耐蚀性能研究。结果施加磁场能显著改善镀层的表面形貌,表面镀层形貌更加均匀致密;试样的耐蚀性显著提高,在平行磁场方向下,当磁场强度为0.07 T时电沉积30 min,所得Ni镀层自腐蚀电位(E_(corr))为–0.193 V,自腐蚀电流密度(J_(corr))为8.305×10^(–7)A·cm^(–2),阻抗值达到3.882×10^(4)Ω·cm^(2),耐蚀性最好。结论施加磁场后,镀层性能得到改善,平行磁场作用下Ni镀层更加均匀细致,其耐蚀性最优,垂直磁场次之,均优于无磁场作用下制备的Ni镀层。

局地气候分区下的杭州中心城区城市热环境研究

以杭州市主城区为例,运用局地气候分区分类框架分析杭州城市热环境。整合卫星遥感影像、建筑物矢量等多源数据,开展了杭州市中心城区局地气候分区分类制图,探讨各LCZ类型分布格局,分析类间和类内热特征和季节差异。①根据城市建筑矢量、地物覆盖分类数据,利用WUDAPT构建研究区LCZ地图;②利用Landsat 8卫星遥感影像通过GEE反演得到研究区逐月地表温度数;③结合LCZ地图和多时相地表温度数据,分析不同局地气候分区各季节间的热环境差异。结果表明:研究区内建筑以中低层为主,且多为开阔类型,自然地表覆盖中低植被区LCZ D占主要比例;LCZ 1-LCZ 3密集建筑类型较其他建筑类型地表温度更高,且随着建筑高度的升高温度依次降低;除水体外,LCZA是所有类型温度最低的区域;夏季各分区之间温度差异显著,夏季热岛强度达到全年最大值,春秋两季热岛强度相近,但是变化趋势不同;类内热岛内部相对稳定,强度变化受周边环境特征影响较大,LCZ 5.1的特征要素相关系数与城市整体变化趋势不一致,尽管占比较高,但不能主导整体变化趋势,BSF在秋季的影响最大(每升高10%升高0.7℃),PSF和ISF在四季的影响力相近,且夏季最高,冬季最低。研究结果能够为城市规划设计和公园建设提供参考,助力于城市的可持续健康发展。

南极宇航员海夏季水文结构变化特征研究

本文基于中国南极考察(CHINARE37-38)在宇航员海获取的海洋综合站位观测数据,结合海冰密集度、WOA23和ERA5再分析资料等,分析了该海域主要水文结构及其变化特征。结果表明:宇航员海夏季水团包括南极表层水(分为夏季表层水与冬季残留水)、绕极深层水、变性绕极深层水和南极底层水。夏季表层水均分布在表层50 m深度以浅,呈现出南冷北暖的趋势。66°S以南的冬季残留水最厚,最深可达200 m左右。绕极深层水向南侵入的趋势明显,CHINARE-38绕极深层水向上涌升的高度较CHINARE-37高出10~20 m。夏季表层水的高温高盐核心位于中心海域无冰区,因为无冰海域的表层海水长时间接收太阳短波辐射而温度较高。近岸海域因冰融水导致局部夏季表层水降温淡化。宇航员海中心海域海面风场维持低气压气旋式环流,次表层水体通过Ekman抽吸上升冷却表层暖水,导致表层与次表层水体混合加强,绕极深层水向南侵入并向上涌升。

基于电场驱动喷射微3D打印的曲面透明电加热玻璃技术

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