BECAPEX科学试验城市建筑群落边界层大气环境特征及其影响

20 0 1～ 2 0 0 3年在北京实施了大气边界层动力、热力、化学综合观测试验 (BECAPEX ,BeijingCityAtmosphericPollutionObservationFieldExperiment) ,获取了北京城市大气动力和大气化学三维结构图像。综合观测试验分析研究发现 ,城市区域呈非均匀次生尺度热岛分布 ,并伴随着城市次生尺度环流 ,影响了局地空气污染物分布特征。MODIS卫星遥感 地面观测资料经过变分分析 ,可发现北京城市空气污染与周边区域影响源有密切关系 ,并影响城市群落环境气候特征 ,导致该区域日照、雾日、低云量和能见度呈显著年代际变化趋势。     

石墨炉原子吸收光谱法测定土壤样品中镉

采用磷酸氢二铵作基体改进剂塞曼扣背景石墨炉原子吸收光谱法测定土壤样品中镉，方法检出限DL=0．012μg／g，精密度RSD在3．55％～7．33％，满足了土壤样品中镉测定的镉质量要求。     

北极苔原Ny-lesund地区短期气候特征

利用我国北极黄河站所在地,德国Koldwey站1994—2003年的逐时常规气象资料,对北极苔原Ny lesund地区短期气候特征进行了初步分析。结果表明,由于受北大西洋暖流的影响,该地是北极同纬度温度最高的地区。岛上气候温暖湿润,即使在隆冬季节,日平均气温都可以升至0℃以上。全年平均风力较小,以东南(SE)风居多。该地区平均增温速度为0. 68℃/10a,是北极增温较快的地区之一。与同期我国北冰洋浮冰区考察数据相比较,Ny lesund气候更温暖湿润,风速要小得多。在Ny lesund地区,美国国家环境预测中心/美国国家大气研究中心(NCEP/NCAR)的近地面气温的再分析结果,与Koldwey站实测常规地面资料相比,在冬季基本一致,而在夏季则差异较大。     

A numerical study of mechanical behavior of a cement paste under mechanical loading and chemical leaching

Based on relevant experimental data of a petroleum cement paste under mechanical loading and chemical leaching, an elastic‐plastic model is first proposed by taking into account plastic shearing and pore collapse. The degradation of mechanical properties induced by the chemical leaching is characterized by a chemical damage variable which is defined as the increase of porosity. Both elastic and plastic properties of the cement paste are affected by the chemical damage. The proposed model is calibrated from and applied to describe mechanical responses in triaxial compression tests respectively on sound and fully leached samples. In the second part, a phenomenological chemical model is defined to establish the relationship between porosity change and calcium dissolution process. The dissolution kinetics is governed by a diffusion law taking into account the variation of diffusion coefficient with calcium concentration. The chemical model is coupled with the mechanical model, and both are applied to describe mechanical response of cement paste samples subjected to progressive chemical leaching and compressive stresses. Comparisons between experimental data and numerical results are presented.     

青藏高原和亚洲夏季风动力学研究的新进展

亚洲夏季风环流受海陆和伊朗高原—青藏高原大地形的热力作用调控.亚洲季风所释放的巨大潜热又对大气环流形成反馈.这种相互反馈过程十分复杂,揭示其物理过程对理解气候变化格局的形成和变化以及提高天气预报及气候预测的准确率十分重要.夏季北半球副热带对流层上层环流的主要特征是存在庞大的南亚高压(SAH)以及强大的对流层上层温度暖中心(UTTM).本文介绍了温度—加热垂直梯度(T-Q_Z)理论的发展,并用以揭示SAH和UTTM的形成机制.指出沿副热带欧亚大陆东部的季风对流潜热加热及其中西部的表面感热加热和高层长波辐射冷却是导致SAH和UTTM在南亚上空发展的原因.文中还介绍了Gill模型用于上部对流层研究的局限性及解决的办法.     

Identifying geospatial services across heterogeneous taxonomies

Geospatial services with different functions are assembled together to solve complex problems. Different taxonomies are developed to categorize these services into classes. As differences in granularity and semantics exist among these taxonomies, the identification of services across different taxonomies has become a challenge. In this paper, an approach to identify geospatial services across heterogeneous taxonomies is proposed. Using formal concept analysis, existing heterogeneous taxonomies are decomposed into semantic factors and their various combinations. With these semantic factors, a super taxonomy is established to integrate the original heterogeneous taxonomies. Finally, with the super taxonomy as a cross-referencing system, geospatial services with classes in original taxonomies are identifiable across taxonomies. Experiments in service registries and a social media-based spatial-temporal analysis project are presented to illustrate the effectiveness of this approach.     

Simulating train moving loads in physical model testing of railway infrastructure and its numerical calibration

Ballastless high-speed railways have dynamic performances that are quite different from those of conventional ballasted railways. The essential dynamic characteristics of high-speed railways due to passing train wheels, such as the cyclic effect, moving effect, and speed effect, were put forward and discussed. A full-scale accelerated railway testing platform for ballastless high-speed railways was proposed in this study. The feasibility of the sequential loading method in simulating train moving loads, and the boundary effect of the proposed physical model of ballastless railways, was investigated using three-dimensional finite element models. A full-scale physical model, 5 m long, 15 m wide, and 6 m high, was then established according to practical engineering design methods. Using a sequential loading system composed of eight high-performance hydraulic actuators, loads of a moving train with highest speed of 360 km/h were simulated. Preliminary experimental results of vibration velocities were presented and compared with field measurements of the Wuguang high-speed railway in China. Results showed that the experimental results coincided with the field measurements, demonstrating that the full-scale accelerated railway testing platform can simulate the process of a moving train and realistically reproduce the dynamic behaviors of ballastless high-speed railways.     

东特提斯喜马拉雅下白垩统碎屑锆石U-Pb年代学及其古地理

东特提斯喜马拉雅在中生代位于东冈瓦纳大陆的结合部位,其古地理对于了解东冈瓦纳大陆裂解至关重要.对东特提斯喜马拉雅塔嘎地区沉积地层进行了详细的碎屑锆石U-Pb年代学研究.结果表明,东特提斯喜马拉雅塔嘎地区采样剖面沉积下限为126.6±2.7 Ma.碎屑锆石年龄谱显示东特提斯喜马拉雅塔嘎地区采样地层主要包含~520 Ma、~890 Ma和~1 200 Ma的特征峰值年龄,对比结果表明东特提斯喜马拉雅塔嘎地区沉积地层碎屑锆石年龄谱与印度东部和澳大利亚西南部地层碎屑锆石年龄谱具有一定的相似性.结合东冈瓦纳岩浆活动记录以及该剖面下部玄武岩年龄,东特提斯喜马拉雅塔嘎地区地层沉积于东特提斯喜马拉雅从东冈瓦纳大陆分离时期,其物质来源可能为印度东部、澳大利亚西南部以及南极大陆.      

天津市城市热岛效应的综合性研究

近几年,我们采用较先进的仪器设备,进行了天津市城市热岛效应的综合性探测和红外线航空遥感测量。并对地面和低空城市热岛强度、厚度和结构进行了分析。结果表明,白天低空热岛强度比地面热岛强度强。并有冷湖现象;在城市内,热岛是由一些小热岛群组成;我们还用能量平衡模式对城市热岛的结构进行了研究。