海水中阴极极化对X80钢应力腐蚀及氢脆敏感性的影响

目的研究不同p H值海水中阴极极化对X80管线钢应力腐蚀及氢脆的抑制作用。方法采用慢应变速率拉伸试验、电化学测试、微观组织观察等分析方法。结果 X80钢在天然海水中的析氢电位约为-940m V(vs.SCE,下同),海水p H为3.5时析氢电位发生正移。其应力腐蚀敏感性与极化电位有很大关系,随着极化电位负移,X80钢的氢脆敏感性增加。天然海水中当极化电位负于-950 m V时,断口出现准解理断裂特征形貌。在-1050 m V极化电位下,钢材进入氢脆断裂区发生脆性断裂。海水p H为3.5时,-900 m V钢材有发生氢脆的危险。结论与天然海水相比,X80钢在p H为3.5的酸性海水中具有较高的应力腐蚀敏感性,两种海水介质中X80钢的应力腐蚀敏感性均随极化电位负移而增加。     

A Variance Estimator for Constrained Estimates of Change in Relative Categorical Frequencies

Consistent estimators of change and state becomes an issue when sample data come from a mix of permanent and temporary observation units. A joint maximum likelihood estimator of state and change creates estimates of state that depend on antecedent viz. posterior survey results and may differ from estimates of state derived from a single-date analysis of the sample data. A constrained estimator of change in relative categorical frequencies that eliminates this potential inconsistency is proposed and a model based estimator of their sampling variance is developed. The performance of the constrained estimator is quantified against six criteria and a joint maximum likelihood estimator in simulated sampling from 15 populations with three combinations of permanent and temporary samples, four to six categorical class attributes, and constant size between sampling dates. Bias of the constrained estimators was negligible but larger than for joint maximum likelihood estimators. Mean absolute deviations and variances of constrained estimators were generally at par with the joint estimators. Constrained estimators of root mean square errors and achieved coverage of nominal confidence intervals of constrained estimators were occasionally better. A generalized variance function for the constrained estimates of change is provided as a computational shortcut.     

How and why is Aquatic Quality Changing at Nahanni National Park Reserve, nwt, Canada?

Nahanni National Park Reserve is located at southwestern NWT-Yukon border. One of the first UNESCO World Heritage sites, Nahanni lies within Taiga Cordillera and Taiga Shield Ecozones. Base and precious metal mining occurred upstream of Nahanni prior to park establishment. Nahanni waters, sediments, fish, and caribou have naturally elevated metals levels. Baseline water, sediment and fish tissue quality data were collected and analyzed throughout Nahanni during 1988–91 and 1992–97. These two programs characterized how aquatic quality variables are naturally varying in space and time, affected by geology, stream flow, seasonality, and extreme meteorological and geological events. Possible anthropogenic causes of aquatic quality change were examined. Measured values were compared to existing Guidelines and site-specific objectives were established.     

乌鲁木齐市可吸入颗粒物(PM10)与总悬浮颗粒物(TSP)的相关性规律浅析

通过对乌鲁木齐市的PM10和TSP数据的对比分析，找出PM10在TSP中所占比率（分担率）在采暖季和非采暖季的变化范围，从而使过去采集的TSP数据与PM10数据有一定的可比性，保证监测数据的连续可比。     

发光细菌法评价工业废水的毒性

用发光细菌测定法估算了两城市污水对河道水体污染的分担率，评价了工厂排放废水的毒性，并据此确定了污染源监督管理中应优先治理的工厂（车间）废水。     

无机痕量分析中预富集技术的应用现状及前景

综述了预富集技术在无机痕量分析中的应用，概述了国内外最新进展，介绍了主要技术及方法的特点，大量文献表明预富集技术用于痕量分析取得满意的效果，降低了检测限，提高了灵敏度。     

合成洗涤剂对小鼠诱变性研究

连续５天腹腔注射同一剂量（１／５ＬＤ５０）的合成洗涤剂，取小鼠骨髓细胞测定嗜多染色红细胞的微核率，研究表明，３种合成洗涤剂（加大香洗衣粉，洁牌餐具洗涤剂，恩威高级餐具洗洁精）使小鼠微核率有所增高，但恩威，洁牌餐具洗涤剂与对照无显著性差异。     

西藏公路建设过程中的生态保护

针对西藏独特的高原生态环境特征，分析了公路建设的生态影响，提出了不同生态系统类型的生态恢复和保护措施。     

Numerical modeling of radionuclide migration in porous media with nonequilibrium sorption

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Mechanics Principle and Engineering Application of Split Layer and Bed Separation of Mining Overburden

<正>To control land surface subsidence caused the underground mineral exploitation and the catastrophic phenomena such as serious damage of buildings, waterbodies, cultivated lands, railways, bridges caused by land subsidence, bed separation grouting technology of overburden is put forward. To provide theoretical support for the technology, the characteristics and the mechanics mechanism of mining overburden from layer-split to formation of bed separation are studied. On the basis of elastic sheet board theory, calculation formula of rock sheet deflection is presented, and the mechanics criteria of the separation formation and the calculation formula of bed separation volume are set up. Finally, the applications and technics of bed separation grout technology of mining overburden to control land subsidence in china are introduced.