美研制出探测地下污染物新方法

探明土壤或地下水中的污染物 ,通常是一个既费钱又费力的过程。美国罗得岛大学的研究人员近日开发出一种新方法 ,有望使地下污染物的探测工作变得更快更省。罗得岛大学发布的新闻公报介绍说 ,在美国环保局的资助下 ,该校助教弗勒利克设计出了一套新系统 ,它通过将两个金属钉插入地下 ,通上电流并测量两个金属钉之间的电压 ,然后算出土壤的电阻率 ,就能判断其是否受到了污染。电阻率测量法目前在分析地下水中溶解的盐类污染物方面已经被广泛应用 ,这些物质都是良好的导电体。而新系统的探测重点是甲苯、二甲苯、乙苯等有机化合物以及其他一些…     

Structural Description of Polyaromatic Nucleus in Residue

The proton nuclear magnetic resonance spectroscopy （1H-NMR）, the synchronous fluorescence spectrometry （SFS） and the ruthenium ions catalyzed oxidation （RICO） method were used to determine the chemical structure of polyaromatic nucleus in Oman residue fractions. The results of 1H-NMR analyses showed that the average numbers of aromatic rings in the aromatics, resins and asphaltenes units were 3.2, 5.6 and 8.2, respectively. SFS was used to investigate the distribution of aromatic rings in residue fractions, the main distribution range of aromatic rings in aromatics, resins and asphaltenes were 3 4 rings, 3--5 rings and more than 5 rings, respectively. The aromatic network in residue fractions was oxidized to produce numerous carboxylic acids. The types and content of benzenepolycarboxylic acids, such as phthalic acid, benzenetricarboxylic acids, benzenetetracarboxylic acids, benzenepentacarboxylic acid and benzenehexacarboxylic acid disclosed the condensed types of aromatic nuclei in the core. The biphenyl fraction （BIPH）, the cata-condensed fraction （CATA）, the peri-condensed fraction （PERI） and the condensed index （BCI） were calculated based on the benzenepolycarboxylic acids formed. The results implied that there was less biphenyl type structures in all residue fractions. The aromatics fraction was almost composed of the cata-condensed type system, and the asphaltenes fraction was wholly composed of the peri-condensed type system, while in the resins fraction co-existed the two types, herein the peri-con- densed type was predominant over the cata-condensed type. Based on the analytical results obtained in the study, the components --aromatics, resins and asphaltenes -- were given the likely structural models.     

一种测量建筑材料和土壤氡面析出率的新方案

在分析了直接测量法测量氡面析出率的原理和影响测量效果各因素的基础上，对建筑材料、土壤氡面析出率的测量方案进行了探讨，并提出了一种新的测量方案。该方案能够较好地克服氡面析出率测量中各种因素的影响，并且具有装置简单、可大批量重复测量、成本低等优点。     

万用表电压测量法查找直流接地故障

直流电源是发电站的主要设备，一旦直流系统发生接地故障，将会严重地危及到发电站的安全和经济运行。因此，本文介绍一种简单易行，能快速找出直流接地点的方法一万用表电压测量法。     

Analysis of Uranium Enrichment in Environment Samples Using HPGe γ-ray Spectrometry

In this work a method for determination of uranium enrichment in environmental samples was studied and the minimum detectable activities of ^235U in environmental samples （including soil, water, swipe） using HPGe γ-ray spectrometry were determined. Eq. （1） is used to calculate the enrichment of uranium in the samples. G was obtained through Eq. （1） or Eq. （2） by measuring a working standard or reference material in which the uranium enrichment is known. After determining the sample, the enrichment of uranium is calculated.     

用声波测量法预测浇注料的热震特性

用声波测量法监测了一种浇注料的一次急冷热震特性和热震疲劳损坏发展过程，这种浇注料的１３００℃下煅烧２小时。料体的密度和显气孔率分别为１．８４ｇ／ｃｍ＾３－１．８６ｇ／ｃｍ＾３和３１％－３２％。烧后的试样在水中作了一次急冷热震试验，△Ｔ高达１２８０℃，同时作了一次从１０００℃到常温的热震疲劳试验。超声波速度、杨氏弹性模量和耐压强度随急冷温差的增加而逐步减小，而坯体中的准静态裂纹增多。在热震疲劳状况下     

零件测绘设计经验谈

在机械维修中，经常需要测绘磨损或损坏的零件．在工作现场往往没有可供参考的图纸，只能根据经验和拆卸下来的不完整的零件进行测绘设计，有时甚至需要改变零件的形状或变更零件的尺寸。因此，经验显得尤为重要。