生活饮用水中铅含量检测技术分析

运用火焰原子吸收分光光度法(火焰法)、无火焰原子吸收分光光度法(石墨炉法)和电感耦合等离子体发射光谱法(ICP-AES)对不同类别水体铅含量的最低检出限进行测定,结果表明:在铅含量的检测区间内,三种方法的最低检出限顺序为:火焰法(0.132μg/m L)ICP-AES(2.23μg/L)石墨炉法(0.629μg/L)。铅含量均未检出,加标回收率均高于90%,检测结果准确、可靠。     

石墨炉原子吸收光谱法直接测定纺织品萃取汗液中砷

本文采用石墨炉原子吸收光谱法直接测定纺织品萃取液中砷。通过在样品萃取液中加入基体改进剂,并对石墨炉原子化工作条件和基体改进剂用量进行优化。结果表明,加入4μL 50g/L硝酸镍基体改进剂,可以有效降低高浓度氯化钠基体的影响,样品检出限可达到0.05mg/kg,相对标准偏差为为1.65~3.44%,实际纺织品样品加标回收率为93.8%~103%。该方法具有快速、准确、灵敏度高等优点,适用于测定纺织品萃取汗液中砷含量的检测。     

微波消解-石墨炉原子吸收光谱法测定纳米二氧化钛中痕量砷

建立微波消解-石墨炉原子吸收光谱法(GF-AAS)测定纳米二氧化钛中痕量杂质砷的分析方法,以快速完全消解二氧化钛基体并且准确测定痕量杂质砷。方法采用氢氟酸、硝酸混合试剂结合高压密闭微波加热技术,解决二氧化钛难消解和低酸度溶液中高钛基体容易水解等难点。通过基体效应影响试验,优选采用热解涂层石墨管,优化石墨炉升温原子化控制程序以及原子吸收光谱仪工作条件等检测参数,消除热稳定性强的二氧化钛基体对测定易挥发痕量元素砷的影响。结果表明:方法检出限为0.02μg/L,回收率为93.0%~106.0%,相对标准偏差9.36%,与ICP-MS检测方法结果对照一致。     

石墨炉原子吸收光谱法测定大米中镉含量研究

目的:通过采用石墨炉原子吸收光谱法来对大米中镉的含量进行测量。方法:首先对所要进行试验的大米做实验前的处理,对大米采用湿法消解法进行处理,采用石墨原子吸收光谱法来测定大米中镉的含量,从而对大米中镉含量的最佳测定时间、重复性、回收率和精密度进行检测。结果:选用实验大米质量1g,采用消解剂为硝酸,实验时间13h,在该实验条件进行处理,然后对进行酸化处理的大米采用石墨炉原子吸收光谱法对镉含量进行测定。石墨炉原子吸收光谱法测定大米中镉含量的加标回收率为98.78%。结论:通过石墨炉原子吸收光谱法对大米中镉含量进行测量,具有测量准确、重复性好、误差小的特点,可以用于大米中镉含量的测定。     

石墨炉原子吸收光谱法测定面制食品中的铝

目的:介绍并建立起面制食品中铝的石墨炉原子吸收光谱法。方法:将面制食品试验样品于85℃进行烘烤(4小时),然后经520℃进行灰化(6小时),采用0.5%HN03溶解并定容,采用石墨炉原子吸收光谱法测定铝。结果:测定线性范围为1.0~50μg/L,相对偏差在1.1%~4.3%,回收率为93.6%~98.2%。结论:在面制食品中铝的测定采用石墨炉原子吸收光谱法方便、快捷、准确,结果满意。     

微波消解-石墨炉原子吸收法测定食品接触用纸制品中铅的含量

采用硝酸-过氧化氢混合溶液微波消解食品接触用纸制品,石墨炉原子吸收法测定纸制品中铅的含量。标准曲线相关系数0.9991,方法检出限0.006mg/kg,测定结果相对标准偏差2.31%~3.53%(n=6),加标回收率93.1%~102.7%。结果表明方法具有简便、准确和灵敏度高的优点。     

阳极溶出伏安法水体镉污染快速测定方法研究

建立一种快速测定水体中镉、铅、汞、砷的阳极溶出伏安法。对现场快速测定影响因素进行探讨,并主要对镉的检出限、精密度和准确度进行研究,将该方法运用到广西龙江镉污染事故应急监测中,并与多种其他方法进行比对。结果表明:该方法运用最优温度为5~40℃,水样最佳p H范围为4~9。便携式阳极溶出伏安法测定污染水样中的镉,检出限为0.1μg/L,加标回收率在80%~110%间;在实际样品质量浓度在2~110μg/L范围内准确度均满足要求,实际样品测定精密度2%~5%;与在线监测结果的相对偏差≤4%,与石墨炉原子吸收测定结果相对偏差≤1%。该方法稳定、快速,灵敏度高,准确度好,可广泛用于重金属污染事故应急监测。     

石墨炉原子吸收光谱法测定六堡茶中的铅和镉

本文用石墨炉原子吸收光谱法测定六堡茶中的铅和镉含量,优化了样品前处理条件和光谱仪的各项技术参数。结果表明:应用微波消解-石墨炉原子吸收法测定六堡茶样品中的铅和镉时,铅的加标回收率在93.1%~99.2%之间,镉的加标回收率在92.3~97.3%之间,相对标准偏差均小于5%。方法准确、方便,可满足检测六堡茶中的铅和镉要求。     

乳浊液进样-石墨炉原子吸收法快速测定牛奶中的铬

目的:快速准确测定牛奶中的铬含量。方法:前处理采用稀释液超声处理牛奶样品,并用石墨炉原子吸收法测定铬,对稀释液的配比浓度,超声时间等条件进行优化。结果:在优化后的条件下,对牛奶样品进行处理分析,测定的相关系数r=0.9997,方法检出限为0.18 ug/L,加标回收率在96.1%~102.9%。结论:本方法操作简单、快捷,具有良好的准确性和可靠性。     

饮用水中锑的检测方法——原子吸收分光光度法

本文采用石墨炉原子吸收分光光度法,外加基体改进剂Mg(NO_3)_2,测定环境水样中锑的含量,最低检测浓度为5.0μg/L。对不同的水样进行测定,回收率在98.3％-102％之间,方法灵敏度高,操作简便,易推广。     

Design method and scientific method

A recurring theme in recent design theory has been a desire to relate design method to scientific method: to create the ‘science of design’ or a ‘design science’. There is an inherent paradox in such a desire since design and science are clearly very dissimilar kinds of activities. Further, the concept of ‘scientific method’ now seems to be in epistemological chaos. For these reasons, attempts to model design method on scientific method seem misplaced. It is proposed that it would be more fruitful to regard design as a technology, rather than as a science. The paper seeks to establish the basis for such a view, drawing especially on the idea that both design and technology involve the application of types of knowledge other than the purely ‘scientific’ kind.     

动态测量不确定度贝叶斯评定的改进方法研究

动态测量不确定度的评定一直是比较复杂的问题,到目前为止,国内外有许多学者对这一问题进行了探索与研究,给出了一些评定的方法,但这些方法都存在自身的缺点与不足,还不能给出十分精确的评定结果。因此,通过对现有基于贝叶斯理论的动态测量不确定度评定方法进行分析,用最大熵原理改进其先验分布的选择与计算方法,从而有效提高计算后验分布的精度,最终提高不确定度的计算准确度。     

无机纳米材料的水热合成及其衍生方法

综述了纳米材料水热合成法的研究进展,并总结了水热合成法的优点和缺点,对水热合成法的反应机理作了初步的探讨,对水热反应中水的状态作了简要分析;对由水热法衍生出来的溶剂热和微波水热法也做了分析,介绍了溶剂热反应中经常使用的有机溶剂和微波反应中微波的加热机理;同时论述了目前这几种实验方法的实验进展和应用情况.     

Numerical manifold method based on the method of weighted residuals

Usually, the governing equations of the numerical manifold method (NMM) are derived from the minimum potential energy principle. For many applied problems it is difficult to derive in general outset the functional forms of the governing equations. This obviously strongly restricts the implementation of the minimum potential energy principle or other variational principles in NMM. In fact, the governing equations of NMM can be derived from a more general method of weighted residuals. By choosing suitable weight functions, the derivation of the governing equations of the NMM from the weighted residual method leads to the same result as that derived from the minimum potential energy principle. This is demonstrated in the paper by deriving the governing equations of the NMM for linear elasticity problems, and also for Laplaces equation for which the governing equations of the NMM cannot be derived from the minimum potential energy principle. The performance of the method is illustrated by three numerical examples.     

Combination of Newmark method and natural element method for elastodynamics

The natural element method (NEM) is a meshless method. The trial and test functions of the NEM are constructed using natural neighbor interpolations which are based on the Voronoi tessellation of a set of nodes. The NEM interpolation is linear between adjacent nodes on the boundary of the convex hull, which makes imposition of essential boundary conditions easy to implement. We investigate the performance of the NEM combined with the Newmark method for problems of elastodynamics in this article. Applications are considered for a cantilever beam with different initial load conditions. The NEM numerical results are compared with the finite element method. NEM shows promise for these applications.     

On coupling of reproducing kernel particle method and boundary element method

In this paper a new coupling method to merge the reproducing kernel particle method (RKPM) and the boundary element method (BEM) is proposed. In this formulation, the whole problem domain will first be divided into two subdomains in which the RKPM and the BEM are applied respectively. A simple and direct coupling procedure is then applied to preserve the compatibility of the solution along the interface of the two subdomains. Unlike other coupling procedures suggested previously, the present coupling procedure neither requires modification of the RKPM and the BEM formulations nor the use of finite elements along the interface boundary between the two subdomains. The validity and efficiency of the coupling procedure are demonstrated by using it to solve five benchmark elastostatic stress analysis problems. In addition, a simple analysis of the a priori convergence rate of the coupling procedure is given. Preliminary assessment of the convergence characteristics of the coupling procedure is done by carrying out uniform refinements on the benchmark problems.     

改进MBCV法在滚动轴承故障诊断中的应用EI北大核心CSCD

针对传统最大类间方差法(Maximum Between‑Class Variance,MBCV)在分离轴承故障信号过程中存在的分割阈值适应性差、分离效果不佳的问题,提出一种基于MBCV动态阈值曲线的滚动轴承故障诊断方法。该方法通过MBCV法获得频谱均分子区间的各分割阈值,然后高阶拟合各部分阈值进而获得动态阈值曲线,再通过调整优化频谱分段数量并以分离信号与原信号之间的均方根误差最小化为目标确定最优阈值曲线;依据最优动态阈值曲线将信号频谱分割为高、低两部分,对低幅值部分进行傅里叶逆变换及平方包络谱分析进而诊断故障。此方法能有效消除强干扰成分,最大化提取轴承故障特征。实验分析结果表明,相比于传统MBCV法,该方法提取的故障特征更加明显。     

The method of fundamental solutions and quasi-Monte-Carlo method for diffusion equations

The Laplace transform is applied to remove the time-dependent variable in the diffusion equation. For non-harmonic initial conditions this gives rise to a non-homogeneous modified Helmholtz equation which we solve by the method of fundamental solutions. To do this a particular solution must be obtained which we find through a method suggested by Atkinson. To avoid costly Gaussian quadratures, we approximate the particular solution using quasi-Monte-Carlo integration which has the advantage of ignoring the singularity in the integrand. The approximate transformed solution is then inverted numerically using Stehfest's algorithm. Two numerical examples are given to illustrate the simplicity and effectiveness of our approach to solving diffusion equations in 2-D and 3-D. © 1998 John Wiley & Sons, Ltd.     

基于热交换系数法的散热器等效建模方法研究

针对散热器结构复杂、建模难度大的问题,提出基于热交换系数法利用基座等效整个散热器,简化分析模型.首先由傅里叶定律和牛顿换热公式得到肋片传热的近似解和对流换热热流量,推导出自然对流和强迫对流两种情况下肋片对流换热系数的表达式,并根据能量守恒原则导出基座等效热交换系数关系式.然后用热分析软件Flotherm分别对等效前和等效后模型进行仿真,结果表明热交换系数法是一种行之有效的散热器简化建模方法.该方法同样适用于其它热仿真软件.