大尺寸高精度三维控制网技术探讨

空间大尺寸机构的位置和姿态测量是诸多领域中不可或缺的必要环节。而传统的一维测量技术在精度、范围和速度上已经无法满足越来越高的需求,因此必须探索新的测量技术和方法。激光跟踪仪的单站坐标测量精度在局部范围内能够达到几十个微米量级,如果要在大尺度空间内同样实现该坐标测量精度,则需要建立全局的精密三维控制网。为了解算控制点全局坐标以及测站的位置和姿态参数,文中基于边角观测值和坐标转换模型建立了激光跟踪仪三维边角网整体平差模型。平差过程中,为了削弱激光跟踪仪测角误差的影响,建立了合理的角度和距离观测值权矩阵,为高精度距离观测值赋予较大的权值,从而对其进行约束。将该方法应用于宝钢不锈钢冷轧厂生产线的安装检测和轧辊轴线平行度测量,基于激光跟踪仪自由设站理论实现大尺寸精密三维控制网的建立,取得了良好效果。     

半干旱沙地-草甸区水面蒸发模拟及其影响因子辨识

在分析半干旱沙地—草甸区的水面蒸发过程及其影响因子的基础上,采用多元逐步回归分析方法,对水面蒸发的众多影响因子进行逐步筛选,找出显著影响因子,建立水面蒸发与其显著影响因子间的多元非线性回归模型,并模拟计算了彭曼蒸发公式、道尔顿水汽运输理论蒸发公式中的风函数,比较分析了彭曼模型、变异道尔顿模型、多元非线性回归模型计算的水面蒸发量。结果表明:彭曼模型、变异道尔顿模型和最终建立的多元非线性逐步回归模型所得结果十分接近,与实测水面蒸发量的趋势也很一致;除变异道尔顿模型稳定性稍差外,其余两者都具有较好的稳定性;多元非线性逐步回归方法可以找到水面蒸发的显著影响因子,剔除掉不显著影响因子,避免因子相关造成的影响,使所建回归模型具有良好的拟合效果,其决定系数达到了0.773,预测结果令人满意。     

影响北京的一例沙尘天气过程的起沙沉降及输送路径分析

本文选取2012年4月27-28日影响北京的一次沙尘天气过程进行分析,发现在本次过程中,沙源地区的沙尘暴主要发生在地面冷锋和500 hPa槽后,在近地层强烈的感热加热与中低层冷平流的共同作用下,形成了不稳定层结及深厚的混合层,最高可达600 hPa,是沙尘天气能够影响下游地区的重要条件。本文还通过分析等熵混合层厚度变化及其平流过程来追踪沙尘天气的输送路径和定位沉降地,发现本次过程有两种传输路径,一种是沿辽宁北部向东而后转向东北方向,主要沿等熵混合层平流向下游移动,之后随着等熵混合层的接地沉降到近地层,该路径影响高度较高;另一种是沿辽宁南部向东南方向移动,混合层平流较清楚,但沉降时与东北路径明显不同,在辽东半岛东部地面辐散气流及下沉运动的作用下发生沉降,并随冷锋后冷高压南侧的东风回流向西输送影响北京地区。另外,由于混合层之上的稳定层明显下压,使沙尘输送高度偏低。运用HYSPLIT模式模拟的前、后向轨迹证实了上述两种输送路径,表明北京的扬沙天气是由东风回流造成的。     

马氏珠母贝激光育苗的生物学机理

对马氏珠母贝激光育苗的机理进行研究，结果表明：激光能加强精子活力，提高精液品质；影响卵子的通透性；抑制水中的细菌生长，使受精卵发育成健壮的胚胎、幼虫、幼苗。     

激光时间传递技术的进展

激光时间传递技术是通过激光脉冲在空间的传播来实现地面与卫星时钟或地球上远距离两地时钟的同步，它具有很高的准确度和稳定度。一些国家已经成功进行了激光时间传递的试验，结果证明利用激光进行时钟之间的同步是有效可行的。介绍国内外已有的激光时间传递试验的情况和结果，重点介绍美国地面与机载原子钟之间的激光时间比对，以及法国的LASSO(LAser Synchronization from Stationary Orbit)和T2L2(Time Transfer by Laser Link)计划。     

2000年度上海天文台卫星激光测距观测报告

介绍了 2 0 0 0年度上海天文台卫星激光测距观测和系统的改进情况     

手持式激光测距仪前级接收通道的相关问题研究

介绍了手持式激光测距仪前置放大电路的设计方法,并且针对便携式设备供电的特殊性,给出了单电源供电放大电路的解决方案,较好地解决了前级接收通道电路设计的相关问题.     

Sensitivity analysis of geologic computer models: A formal procedure based on Latin hypercube sampling

Mathematical models in which a response variableY is calculated, usually via a computer program, as a function of input variablesX ₁ ,X ₂, ...,X _k are encountered frequently in earth sciences literature. In many cases, uncertainty in the knowledge of the correct values of the input variables exists, leading to uncertainty in the correct value of the response. Sensitivity analysis procedures can be used to identify which input variable uncertainties contribute most to uncertainty in the response variable.This paper presents the technique of Latin hypercube sampling, a structured, formal sampling process used in the sensitivity analysis procedure. Output resulting from the sample is analyzed using stepwise regression analysis, leading to identification of key input variables. Future data gathering activities can then be done efficiently, focusing on these variables. The technique is applied to a model, developed by Sudicky and Frind, which represents the flow of a contaminant through a porous media.     

Heating status of the Tibetan Plateau from April to June and rainfall and atmospheric circulation anomaly over East Asia in midsummer

Based on the 1958-1999 monthly averaged reanalysis data of the National Center for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) and the rainfall data of 160 Chinese surface stations, the relationship between rainfall and the atmospheric circulation anomaly over East Asia (EA) in July and the sensible heating (SH) over the Tibetan Plateau (TP) from April to June (AMJ) is investigated by using the rotational experimental orthogonal function (REOF) method. The results show that the TP is an isolated heating source in this period. The lagged correlation analysis between the first rotational principal component (RPC) of SH over the TP in May and rainfall of EA in July demonstrates that strong SH over the TP before July leads to a positive rainfall anomaly over the TP, the valley between the Yangtze River and Huaihe River, and the regions south and southeast of the TP, and the Sichuan Basin and Yunnan-Guizhou Plateau, but less rainfall anomaly over the regions north, northeas     

A portable remote methane detector using an InGaAsP DFB laser

A portable remote methane detector based on infrared-absorption spectroscopy using an InGaAsP distributed-feedback laser is described. This equipment transmits a laser beam and detects a fraction of the backscatter reflected from the target. From this, the detector thereby measures the integrated methane concentration between the detector and the target. The equipment operator can easily detect methane clouds at a distance by hand-scanning the laser beam. To achieve a high sensitivity of detection, wavelength-modulation spectroscopy is applied to the infrared-absorption measurement for methane. The wavelength of the light source is modulated at a frequency of 10 kHz, and the center wavelength is stabilized at the center of the 2₃ band R(3) line of methane (1.65372 m). When used with typical targets at distances up to 10 m, the detector has a detection limit of less than 5 ppm-m. To the best of the authors knowledge, the detector is the only hand-held product capable of remote methane detection. Recently, this novel equipment was commercially introduced into the Japanese market as a product named the Portable Remote Methane Detector (PRMD). Some PRMD units were in research use for detecting methane emissions from garbage landfills, although the PRMD was mainly developed for remote detection of leaks from natural gas pipelines. The author expects that the PRMD could become the standard equipment for field measurements of methane emissions from land.