以对硝基氯苯为原料合成对氨基苯甲醚

以对硝基氯为原料，利用相转移催化反应，先制备对硝基苯甲醚，然后用铁屑粉还原对硝基苯甲醚合成氨基苯甲醚。第一步反应在70-80℃下回流5h，对硝基苯甲醚的收率可达97%，第二步反应在102℃下回流2h，对氨基苯甲醚的收率为82%，纯度为99%。     

列车对半圆拱形隧道中电磁波截止频率的影响

在空隧道中电磁波存在着截止频率，列车的存在改变了隧道的截面形状和尺寸，从而影响了电磁波的截止频率。应用有限元方法研究了煤矿井下巷道中列车的高度，宽度和位置对半圆拱形隧道电磁波截止频率的影响，其结果对铁路隧道，公安隧道等有限空间的无线通信也具有重要的意义。     

Asymptotic efficiency properties of least squares in an ultrastructural model

This paper considers the estimation of both the intercept term and the slope parameter in a linear ultrastructural model using direct regression and reverse regression methods. Without assuming the errors to be normally distributed, asymptotic expressions for the bias and the variance of the estimators are derived and analyzed. The effect of departure of the errors from normality is also studied.     

动态Cache技术在网站性能设计中的应用

本文主要讲述如何利用Cache技术,来有效的提高网站性能。以ASP.NET为基础,展示ASP.NET中使用Cache的新特性,主要应用了Databasedependencies技术。     

CARR水平孔道的设计特点

介绍了中国先进研究堆(CARR)水平孔道的用途、在堆本体的布置、水平孔道结构设计及设计方面的特点。     

声光技术在光纤系统中的应用

本文简要介绍了在光纤通信、光纤传感和光纤信号处理枝术等各种光纤系统中可能开发应用的固体声光技术和光纤声光技术。     

Steady laminar flow in a 90 degree planar branch

The flow characteristics of a Newtonian fluid in a two-dimensional, planar, right angled Tee branch are studied over a range of inlet Reynolds number of 10–800 by solving the Navier-Stokes equations using a finite element discretization. The effects of the branch length and the grid size on the interior flow field are examined to assess the accuracy of the solutions. In one case the computed velocity field is compared with the Laser Doppler anemometry measurements available in the literature and excellent agreement has been obtained. The computed velocity field is believed to be accurate within about 5%. Results are presented for two types of experimentally realizable boundary conditions—viz. equal exit pressure at the outlet of each branch and specified flow split between the branches. For the case of equal exit pressures the fractional flow in the main duct increases with increasing Reynolds number and the flow characteristics in the side branch become akin to that in a cavity. For the case of specified flow split, the number, size and strength of the recirculation zones increase as more fluid is forced to go into the side branch. The length of the side branch appears to have very little influence on the interior flow field, particularly at higher Reynolds number. This observation is rationalized as being due to the parabolized approximation becoming more valid at higher Reynolds numbers. The critical Reynolds number at which the first recirculation zone appears in the side branch increases with increasing fractional flow in the side branch and with decreasing side branch width.     

崇礼东坪黄金公司缓倾斜薄矿体采空区综合治理

在采空区调查的基础上,以FLAC工程力学分析软件为手段,应用“诱导崩落和封闭采空区综合治理”理论,进行缓倾斜薄矿体采空区综合治理研究.该项研究与实践为缓薄矿体采空区综合治理提供了可供借鉴的经验,并为矿山创造了可观的经济效益.     

浅谈黑客入侵及服务器安全防护

在网络流行的今天,我们如何更好地保护自己的服务器的安全已是一个更加重要和普及的问题。本文着眼黑客入侵的手段,阐述了服务器安全防护的一些措施。