直读光谱法测定钢中的Pb、As、Sn、Nb的研究

钢中Pb、As、Sn、Nd等痕量元素对钢材性能影响很大，近年来开发的钢材系列新产品要求对Pb、As、Sn、Nb等痕量元素进行控制，但采用光谱分析这些元素从未进行研究过。本文选用ARL4460直读光谱仪，通过对仪器检测限和精度的试验、分析条件和样品加工工艺等方面的探索。解决了直读光谱仪仪器分析的系列问题，使ARL4460直读光谱仪高效率应用于钢中Pb、As、Sn、Nb等痕量元素的现场分析。     

Selenium and selenoproteins in mammals: extraordinary,essential, enigmatic

Selenium (Se), once known only for its potential toxicity, is now well established as an essential trace element for mammals. Insufficient Se intake predisposes to and manifests in a variety of diseases. Recent studies have proven that it is the synthesis of selenocysteine (Sec)-containing proteins, designated selenoproteins, which represents an essential prerequisite for regular development and a long and healthy life. New transgenic mouse models analysing those selenoproteins with proven enzymatic functions displayed particular phenotypes and highlighted essential Se-dependent processes in development, growth or against specific challenges. While there is a growing molecular understanding of and general agreement on the importance of sufficiently high Se intake and undisturbed selenoprotein biosynthesis, many of the recently identified selenoproteins are still uncharacterised, and the effects and consequences of supra-physiological Se dosages are not biochemically understood. With the recent definition of the human and mouse selenoproteomes and a growing number of available tools, the Se field is now geared for a great leap forward. Se biology has already broadened our knowledge about the genetic code and about protein translation. It now holds great promises also for a better understanding of some key aspects of cancer, inflammation, fertility and prevention of age-associated diseases.Received 17 March 2004; received after revision 29 April 2004; accepted 27 May 2004     

基于遗传算法的多核芯片并发追踪调试方法

基于追踪的调试技术将追踪信号连接到追踪缓存,这些连接设施不仅占用有限的片上资源,全局连线还可能导致信号完整性问题.一种有效的解决方案是复用片上网络传输追踪数据.复用片上网络传输多组并发追踪信号,需要确定追踪缓存数量和放置位置以满足链路带宽的约束,同时实现传输功耗最小化.本文将该问题规约为NP难约束P-Median问题,并提出了一种基于遗传算法的多追踪缓存选址方法.在片上网络链路带宽的约束下,优化追踪缓存选址数和追踪数据传输能耗,为多组并发追踪信号的实时追踪提供了一种有效方法.实验结果表明,在同等约束条件下,多缓存能够有效提高追踪信号数量.相比于以前的研究结果,本文方法能够有效地减少缓存选址数和降低追踪数据传输能耗.     

基于踪迹挖掘的自动缺陷警报分类方法

缺陷检测一般包括静态分析与人工确认两个阶段.静态缺陷检测工具报告大量警报,但是主要的警报确认工作仍然由人工完成,这是一件费时费力的工作.巨大的确认投入,会导致测试人员和管理人员拒绝使用该静态检测工具.为了辅助警报确认工作,提出一种基于警报踪迹挖掘的警报分类方法,使用该方法挖掘警报踪迹进而将代码结构相似警报分为一类,使得分类后的最终警报报告更加易于人工确认.实验表明,该方法能够在较大规模的软件测试过程中分类测试结果,提高警报确认效率.     

色谱联用技术在环境和生物样品中痕量超痕量元素形态分析研究进展

随着分析科学的不断发展,常用的元素分析方法,如光谱技术(AES,AFS)和质谱等已不能满足环境和生物样品中痕量、超痕量元素的赋存形态分析。以色谱联用技术为代表的元素形态分析测试技术(如液相色谱-原子光谱联用、色谱-电感耦合等离子质谱联用、毛细管电泳-电喷雾离子化质谱联用技术等)已成为国内外研究的热点。本文扼要的介绍了近年来国内外在环境和生物样品中痕量、超痕量元素砷、硒、汞形态分析的色谱联用技术研究进展,并侧重于样品前处理方法、痕量或超痕量元素的形态分析技术。     

土壤侵蚀研究中的地球化学示踪技术应用评价

土壤侵蚀被认为是全球最严重的环境问题之一。随着人口增加，土地的强化利用，土壤侵蚀日益严重。土壤侵蚀及其引起的江河堵塞、洪水泛滥、养分流失、土壤退化、土地生产力下降、水体污染等一系列生态环境问题，不仅为全球所关注，而且也关系到我国农业持续发展的重大问题。传统的土壤侵蚀研究方法如高差法、遥感研究法、RUSLE等研究方法存在一些不足，而核素地球化学示踪法、稀土元素示踪法、磁性示踪剂法、土壤地球化学指标法等地球化学示踪方法为土壤侵蚀在精度和量化以及实用上提供了更好研究手段。分别论及了放射性核素137^Cs，7^Be，210^Pb示踪、稀土元素示踪、磁性示踪剂法、土壤地球化学指标法等在土壤侵蚀研究中的应用现状。比较和评价了国内外地球化学示踪方法及其在土壤侵蚀研究中的应用进展，可兹今后在这方面的研究工作参考借鉴。     

Distribution of metals in annual rings of the beech (Fagus sylvatica) as an expression of environmental changes

Summary Annual rings of 140–160-year-old beeches (Fagus sylvatica) from St. Ingbert, Saarland (FRG) were prepared and analyzed for 14 metals by atomic absorption spectroscopy. According to the chronological variations of their concentrations, the elements could be divided into three groups: 1) Metals without any tendency for chronological changes. This was established for Na, K, Cu, Cr, Co, Ni, Pb, and Cd. 2) Metals with a recent decrease of their concentrations, appropriate for Ca, Mg, Mn, and Zn. 3) Metals with a recent tendency to increase, e.g. Fe and Al. These variations are discussed in connection with the industrial history of the Saarland region and the influence of acid immissions which may alter the soil and thereby the trace element metabolism of the trees with consequences for the vitality of the plants.     

Geochemistry,soils and cardiovascular diseases

Summary The hypothesis is presented that deficiencies or excesses in the content or availability of trace elements in rocks and soils, or in water flowing through them, may be a possible cause of certain chronic diseases, including cardiovascular ones. The geographic distribution of cardiovascular diseases is often associated with geochemical differences. This trend is particulalry evident in the United States and in Europe, with higher rates for cardiovascular mortality in areas underlain by soils that are poor in most essential trace elements. Confirmation of this trends is found in connection with the degree of mineralization of local water supplies. Areas that are served by soft waters usually show higher rates of cardiovascular mortality and other forms of cardiovascular pathology, compared with the areas that are served by hard waters. Such a negative association between water hardness and cardiovascular pathology is evident in many countries, both industrialized and developing ones.     

Interaction of Co, Mn, Mg and Al with d(GCCCATGGC) and d(CCGGGCCCGG): a spectroscopic study

Spectroscopic study of the interactions of metal ions, Co, Mn, Mg and Al with d(GCCCATGGGC) and d(CCGGGCCCGG) revealed the following. Metal ions Mn, Al and Mg at the lowest concentrations enhanced the t _m of oligomers, whereas Mn and Mg at higher concentrations decreased the t _m . Co enhanced the t _m of oligomers at higher concentrations. The studies have also indicated that Mn at lower concentrations displaced EtBr fluorescence, Mg and Co at moderate concentrations and Al only at higher concentrations. Addition of Co, Mn, Mg and Al altered the bands of the circulars dichroism (CD) spectra of the oligomers in a concentration-dependent manner. The CD spectra of d(GCCCATGGGC) and d(CCGGGCCCGG) indicated B and Z forms of DNA, respectively, in contrast to the A form observed in the crystal structures. Mg and Co at different ionic strength induced Z–B transition in d(CCGGGCCCGG), while Al at higher concentrations induced a Z–A transition. Mn did not induce any transition. This is the first report to show that Al causes structural transitions in sequence-specific oligomers and has strong binding ability with GC-rich euchromatin oligomers. Received 22 December 1997; received after revision 16 March 1998; accepted 16 March 1998     

Effects of chronic caffeine feeding on the activities of oxygen free radical defense enzymes in the growing rat heart and liver

The purpose of the present study was to determine the relationship between concentration of Zn, Cu and Fe, and the catalase, glutathione peroxidase and superoxide dismutase activities in the heart and liver of newborn rats whose dams were fed a diet supplemented with caffeine. Heart Zn levels of the 22- and 30-day-old rats of the caffeine group showed a decrease, whereas liver Zn levels showed an increase compared to the control. Cu levels in the liver at day 22 in the caffeine group were less than in the control. Cu- and Zn-containing superoxide dismutase activities showed an increase in the hearts of the caffeine group compared to the control. The activity of catalase and glutathion peroxidase showed no difference in the heart and liver between the groups. The present study suggests the possible involvement of superoxide dismutase enzyme in the impairment of heart formation as a result of chronic caffeine intake in the early growing period.     

Mineral composition of pigeon milk

Summary Mineral analysis of pigeon milk indicates its major elements to be P>Ca>K>Na>Mg (in that order) and trace elements Fe>Zn>Mn>Cu. Whereas the levels of Ca, K, Mg, Na and Mn remain fairly constant in the first week, those of P, Fe, Zn and Cu fall significantly during this period. Compared to cow's and human milk, pigeon milk has definitely higher levels of trace elements. Similarly, the trace mineral content of pigeon milk exceeds that of pigeon egg albumen or yolk. Except for Fe, Mn and Cu, pigeon milk is richer than adult pigeon feed in its mineral content. The Ca:P ratio of pigeon milk increases from 0.3 to 1.1 in the first five days. It appears that the high trace mineral content of pigeon milk is one of the factors contributing to the phenomenal postnatal growth of squabs.     

基于均匀设计法的有限元网格划分与精度提高

本文首次运用均匀设计法的理论到有限元网格划分与精度提高领域,借助MATLAB程序计算,可以得出网格划分的关键点。运用二次开发的理念,在有限元网格划分时进行二次优化。具体思路是在求解同一个工程问题时,分别用均匀设计的方法计算得出结果（应力最优点）,再与有限元方法计算得出结果（应力梯度）比较,应力变化图如果吻合,可以在有限元划分网格时使用MATLAB优化的关键点来加密网格。因为结果相等说明均匀设计得到的优化点等价于变化梯度大的点,加密梯度变化大的点当然精度更高。后面的计算结果证明均匀设计法相对自适应网格划分时的优越性,为全部单元都加密时带来结果失真的问题提供了一种有效的解决方法。     

石油井架有限元分析

井架是石油开采设备的重要组成部分之一.考虑风载荷的影响,运用ANSYS对石油井架进行有限元分析,得到石抽井架的受力分布云图.本文的研究对井架结构设计和油田安全生产有着重要指导意义.     

基于Pro／M对齿轮泵齿轮轴的精确建模和模态分析

以Pro／E为平台,依据方程精确建立齿轮泵的齿轮轴三维实体模型,并以振动力学和有限元理论为基础,建立齿轮轴的有限元模型,利用Pro／E集成环境Pro／MECHANJCA对其进行模态分析,计算出其前4阶固有阵型和固有频率,为齿轮泵的齿轮轴优化设计提供理论依据;为其动力响应的计算奠定了基础;为改善齿轮泵的动态特性、避免共振的发生、提高其工作的可靠性提供了一种方法。     

The epidemiology of dental caries in relation to environmental trace elements

Summary This paper reviews the influence of the geochemical environment on the epidemiology of human dental caries. The best documented association is that between water borne fluoride and reduced caries prevalence. The influence of fluoride was first reported during the early decades of this century in Colorado, USA, and led to the fluoridation of some public water supplies in several countries. In all cases, fluoridation has been followed by significant improvements in dental health and no adverse effects in general health. Other trace elements in food and water have now been linked with dental caries. Molybdenum has been associated with reduced caries prevalence whereas selenium and lead appear to have adverse effects. Cavity formation in teeth probably involves a localised dissolution of the enamel surface by the products of bacterial activity. It is possible that the incorporation of trace metals into the apatite microcrystals of enamel may alter their physical properties, especially solubility, and hence their susceptibility to degradation.     

基于结构元方法的矿井机械模糊可靠性分析

应用模糊结构元理论,对矿井可修复机械设备可靠性中的有效度进行研究.首先,定义了模糊可靠度、模糊维修度和模糊有效度,并应用结构元理论对其进行表示.提出了相关的运算定理,在此基础上,再运用结构元理论对模糊有效度进行表示.之后,提出了正序,该序为全序.最后,用算例计算模糊有效度,通过正序对有效度进行比较.结果表明,运用模糊有...     

A hybrid-stress solid-shell element for non-linear analysis of piezoelectric structures

This paper presents eight-node solid-shell elements for geometric non-linear analyze of piezoelectric structures.To subdue shear,trapezoidal and thickness locking,the assumed natural strain method and an ad hoc modified generalized laminate stiffness matrix are employed.With the generalized stresses arising from the modified generalized laminate stiffness matrix assumed to be independent from the ones obtained from the displacement,an extended Hellinger-Reissner functional can be derived.By choosing the ass...     

基于Benchmarking技术的汽车侧面碰撞建模与仿真试验

介绍了Benchmarking技术的概念和基本工作流程,并根据某车型所进行的Benchmarking数据,建立了包括车身结构、发动机和底盘系统在内的整车有限元分析模型根据ECE R95法规进行了整车侧面碰撞仿真试验,通过对比仿真试验的结果与实车侧面碰撞试验的结果,验证了模型的有效性。本文的研究方法为Benchmarking技术在汽车碰撞安全分析上的应用提供了参考。     

双块式无砟轨道温度场试验研究和数值分析

为较准确掌握无砟轨道温度场的分布规律,建立无砟轨道温度与环境温度的对应关系,为温度应力的计算和无砟轨道设计提供基础参数,本文测试了双块式无砟轨道不同部件、不同位置的温度和环境温度变化情况,建立有限元模型对无砟轨道温度场进行了数值模拟和对比.实测数据及数值模拟的结果均表明:道床板温度随外界气温呈以日为周期的周期性变化,秋季平均每天的升温时间约为8 h,降温约16 h;由于热交换条件的差异,距轨道表面越远,轨道温度受环境气温的影响越小,道床板角部的温度变化幅度大于中部,支撑层与基床表层的温度变化幅度很小;道床板内存在较大的温度梯度,随着距表面距离的增大,温度梯度逐渐减小,至支撑层时温度梯度可忽略不计;采用有限元模拟的方法获取无砟轨道温度随气温变化规律是可行的.