三维激光扫描点位误差源分析

目前对三维激光扫描的分析主要停留在误差模型的建立上,没有对三维激光扫描仪的特点及其所受的误差进行分析,而三维激光扫描仪的系统误差和偶然误差都将会对整个误差模型的建立产生影响,点位误差源的准确分析是点位准确建立点位误差模型的基础。基于此,本文对三维激光扫描仪的点位误差源进行了分析,得到了不同误差源的误差模型,并给出了不同条件可能对激光扫描仪误差影响的大小。     

冷热源空间位置对水系统循环的影响

通过供暖水系统和空调冷热水系统的实例计算,将重力循环压力、冷热源在系统中的位置及系统的质调节与量调节结合在一起进行分析.结果表明,冷热源的空间位置影响重力循环的形成和水循环方向;在系统质、量调节运行中,因冷热源的空间位置的不同,重力循环压力对管网系统垂直失调产生较大影响.     

具有非局部源和边界流抛物型方程组解的性质

研究了一类具有非局部源及边界流抛物型组解的性质,通过构造方程组的上、下解及运用比较定理,得到了方程组解整体存在及解在有限时刻爆破的充分条件。由此得到,当反应项和扩散项的指数满足不同条件时,方程组的解具有不同的性质。     

矿井突水水源判别方法与应用

对目前广泛使用的矿井突水水源判别方法进行了综合评述.从整体而言,除了水化学分析方法外,其他方法都是以一定理论为基础,或构造最优函数,根据判别目标达到最优时的状态进行水源识别;或构造适当的区间,根据一定的法则使判别目标进入不同的区间,进行水源识别.样本较多时采用BP神经网络法,样本较少时采用SVM法会取得更好得预测效果.针对研究区实际状况,选择基于MATLAB的BP神经网络法进行突水预测,准确率达到91.67%,训练样本的选择和数量对预测结果影响较大.     

关于对金属冶炼建设项目安全设施设计编写的思考

根据金属冶炼建设项目安全设施设计编写提纲,围绕安全设施设计编写中常遇到的几个问题进行分析和思考,主要阐述编写安全设施设计的前期准备工作和编写重点。     

Substitutional diffusion and Kirkendall effect in binary crystalline solids containing discrete vacancy sources and sinks

We investigate vacancy-mediated diffusion in a binary substitutional alloy by explicitly accounting for discrete vacancy sources and sinks. The regions between sources and sinks are treated as binary crystals with a perfect lattice structure containing a dilute concentration of vacancies. The sources and sinks are assumed ideal, maintaining an equilibrium vacancy concentration in their immediate vicinity. Diffusion within the perfect lattice is described with a diffusion-coefficient matrix determined by kinetic Monte Carlo simulations for a binary, thermodynamically ideal alloy in which the components have different vacancy-exchange frequencies. Continuum simulations are performed for diffusion couples with discrete grain boundaries acting as vacancy sources and sinks. Effective grain coarsening due to the Kirkendall effect is observed even in the absence of Gibbs-Thomson driving forces. As in standard ternary systems, uphill diffusion is observed. We also find that the drift of the lattice frame of reference as a result of the Kirkendall effect increases with the source/sink density. Upon increasing the density of vacancy sources and sinks, we recover the conventional treatment of substitutional diffusion, which assumes a dense and uniform distribution of vacancy sources and sinks that maintain an equilibrium vacancy concentration throughout the solid. The inverse Kirkendall effect, where the slower component segregates at grain boundaries acting as vacancy sinks, is also observed in the simulations.     

连续碳分CO2吸收率分析及探讨

本文简述了CO2 气体吸收率的测定原理 ,着重分析了影响连续碳分CO2 气体吸收率的因素 ,提出了提高连续碳分CO2 气体吸收率的途径     

中国的铸造生产能力与铸件出口贸易

2001年度中国灰铸铁，铸钢和可锻铸铁三类铸件的产量均大于或相当于日、美、德三国同类铸件产量的总和。尚欠发达的中国相关工业如何能为如此巨大的铸造工业提供足够的订单?美国按相关工业分类预测铸件年需求量的经验值得我们借鉴。中国铸件出口以廉价低档铸件为主，量值长期在低位徘徊的局面应予改变。2003年度美国各类进口铸件预计可达220万t，销售总金额约为40亿美元。     

关于城市饮用水水源地风险管理的思考

在综合分析我国城市饮用水水源现有状况下,阐述如何开展城市饮用水水源地风险评价和管理风险评估、风险减免和规避、全过程风险监控和信息发布以及事故应对的工作内容。建议:1开展全国城市饮用水水源地风险评估和风险管理工作;2城市饮用水水源风险管理要以流域环境应急管理相衔接;3强化政府的监管及公共服务职能;4探索水源地保护与补偿机制。提出对于高风险的城市供水水源地难以降低风险的,必要情况下要改变水源,选择风险相对低的水源地作为供水水源。     

Using the World Wide Web for Art and Humanities Reference Services

Abstract

This paper describes what the World Wide Web is and what is needed in order to access its information. It discusses the future of art and humanities reference resources and presents criteria for evaluating Web sites. A review of the literature related to “Generation X” and their information expectations was done. There is an annotated list of specific World Wide Web resources related to African Diaspora, American Poetry, Comparative Literature, Gay and Lesbian Literature, and Outsider Art. This list provides examples for evaluation and is not meant to be exhaustive.