Initial results from long-term measurements of atmospheric humidity and related parameters in the marine boundary layer at two locations in the Gulf of Mexico

Measurements of boundary layer moisture have been acquired from Rotronic MP-100 sensors deployed on two NDBC buoys in the northern Gulf of Mexico from June through November 1993. For one sensor, which was retrieved approximately 8 months after deployment, the post- and precalibrations agreed closely and fell well within WMO specifications for accuracy. The second sensor operated continuously from June 1993 to February 1997 (3.5 years). Buoy observations of relative humidity and supporting data were used to calculate specific humidity and the surface fluxes of latent and sensible heat. Specific humidities from the buoys were compared with observations of moisture obtained from nearby ship reports, and the correlations were generally high (0.7–0.9). Surface gravity wave spectra were also acquired. The time series of specific humidity and the other buoy parameters revealed three primary scales of variability, small (h), synoptic (days), and seasonal (months). The synoptic variability was clearly dominant and occurred primarily during September, October, and November. Most of the synoptic variability was due to frontal systems that dropped down into the Gulf of Mexico from the continental US followed by air masses which were cold and dry. Cross-correlation analyses of the buoy data indicated that: (1) the moisture field was highly coherent over distances of 800 km or more in the northern Gulf of Mexico; and (2) both specific humidity and air temperature served as tracers of the motion associated with propagating atmospheric disturbances. These correlation analyses also revealed that the prevailing weather systems generally entered the buoy domain from the South prior to September, but primarily from the North thereafter. Spectra of the various buoy parameters indicated strong diurnal and semidiurnal variability for barometric pressure and sea surface temperature (SST) and lesser variability for air temperature, wind speed and significant wave height. The surface fluxes of latent and sensible heat were dominated by the synoptic events which took place from September through November with the transfer of latent heat being primarily from the ocean to the atmosphere. Finally, an analysis of the surface wave observations from each buoy, which included calculations of wave age and estimates of surface roughness, indicate that major heat and moisture flux events coincide with periods of active wave growth, although the data were insufficient to identify any causal relationships.     

机车车体结构设计中变元法的应用与研究

变元法是用于机械产品结构设计的一种富有创造性内涵的新方法，是一种系统性的、逻辑性的设计方法，有助于可靠、有效地构造结构设计方案。通过分析机械构造的形状、材料、位置、数量、连接、尺寸和工艺等基本元素的变化，探讨了变元法在机车车体结构设计中的应用。     

应用响应面方法进行200km/h转向架阻尼器参数的优化研究

以我国铁路应用的 2 0 0km/h客车为实例 ,应用响应面优化方法 ,进行 2 0 0km/h转向架悬挂系统的阻尼器参数优选。首先应用ADAMS/Rail进行 2 0 0km/h客车的动力学仿真计算 ,将计算结果与试验比较 ,验算了模型的准确性。然后 ,应用响应面优化法对其阻尼参数进行优化 ,将得到的最优参数应用到ADAMS建立的仿真模型中 ,得到了更好的舒适性     

电力机车车体底架结构设计

结合各型电力机车车体底架的结构特点,详细阐述了底架各主要部件的结构设计及其特点,并进一步介绍了底架结构的选材及计算分析方法。     

津滨轻轨常用跨度桥梁结构型式的选择

津滨轻轨工程近 40km采用高架桥梁 ,选定合理的桥梁结构型式至关重要。根据工程及现场的实际情况 ,明确桥型选择原则 ,同时提出 7种桥型结构 ,分别论述其各自的技术特点 ;并结合地基基础实际情况 ,全面进行技术经济比较 ,提出推荐的桥梁结构类型     

弯斜坡异形桥梁全过程结构仿真分析及其软件3D-BSA的开发

3D－BSA2．0系统是一个集前处理建立模型、结构分析计算、后处理图形生成于一体的弯斜坡异形桥梁空间结构分析软件。本文着重论述了3D－BSA对弯斜坡异形桥梁结构分析中几个关键技术问题的处理，包括限位条件的引入、曲线梁自重荷载的计算、空间预应力描述及计算、徐变分析计算、内力影响面分析及其自动充载，最后给出Windows95操作系统下3D－BSA2．0的部分图形界面。     

弯道超高路段沥青路面的力学响应分析

车辆在弯道超高路段行驶时会受到离心力作用,而现行路面设计方法未考虑离心力的影响。工程实践发现,在沥青路面弯道超高路段病害较多。就这分析了路面超高路段的力学特征,推导出离心力导致轮载不平衡的计算公式。利用有限元软件,以高速公路典型沥青路面结构为例,定量分析了离心力对路面力学响应的影响。计算表明:考虑离心力后路面的力学响应均大于不考虑离心力的情况,且速度越高影响程度越大。可见离心力的存在和现行设计方法的不足是导致路面弯道薄弱环节的原因。     

数字图像技术在露石混凝土路面中的应用

应用数字图像技术,将普通数码相机拍摄的露石水泥混凝土路面照片进行处理,根据图像的灰度值变化分析得到露石混凝土路表面的构造深度,并通过与常规方法的比较表明,此方法测量的路表面构造深度结果可靠,操作简单,可以在分析露石混凝土路面粗糙的表面特征上应用。     

复杂形状海洋浮体水动力系数计算

网格划分是水动力计算的关键环节,文中针对复杂形状海洋浮体提出了一种湿表面网格划分方法.对于有复杂首尾结构的浮体,用型线重构的方式在首尾生成曲面构成所需要的截面线,将通用建模工具和NURBS曲线拟合相结合,生成相贯结构的相交线;然后,用分片法生成浮体湿表面及内自由面网格,并独立表达各自的速度势以处理不规则频率现象,进而进行水动力系数计算.计算结果表明,上述处理方式很适合复杂形状海洋浮体水动力系数的计算.     

上海地铁轨面接触疲劳裂纹伤损的产生、影响及防治

随着上海地铁运营年限的不断增加,系统设备也不断老化,特别是钢轨的伤损越来越频繁.对上海轨道交通1号线钢轨伤损的类型特点进行了分析,并依据其特点对1号线自1999年来发现的伤损钢轨进行了统计.在众多的钢轨伤损中,轨面裂纹伤损非常严重.运用轮轨接触力学分析了轨面裂纹伤损产生及发展的主要原因,并提出了防治措施.