以最小二乘法直线度评定食品中砷测定的不确定度分析

目的:以最小二乘法直线度评定食品中砷测定过程中存在的不确定度,并找出影响不确定度的因素较大的环节。方法:根据GB/T 5009.11-2003《食品中总砷及无机砷的测定》的方法,应用最小二乘法拟合直线,进行不确定度评估,并计算出合成不确定度。结果:各分量中工作曲线变动性、移液管、样品定容过程及测量重复性引入的不确定度贡献较大,相对扩展不确定度为U=2.5%(k=2)。结论:以最小二乘法直线度评定食品中砷的不确定度,提高了评定的可信度,通过实验各环节的分析,要求操作过程必须细心、准确、规范,尽量减少不确定度。     

脉冲红外法检测钛合金中氧含量的不确定度评定

对脉冲惰性气体保护红外吸收法测定钛合金中氧含量的检测结果进行了不确定度评定,采用A类不确定度对称量过程、仪器示值和标准物质的不确定度进行评定,采用B类不确定度对连续测量和建立工作曲线引入的不确定度进行评定,对样品检测过程的不确定度分量进行分析,重点讨论了称量不确定度和线性拟合引入的不确定度进行量化评定,计算了钛合金样品中氧含量的标准不确定度和扩展不确定度,在本试验中,线性拟合过程和标准物质不确定度分量是不确定度的主要来源,对此提出了减小测量不确定度的方法.     

矢量网络分析仪相位测量的校准

提出了用标准长度空气线作相移标准校准矢量网络分析仪相位测量的方法、步骤,给出了试验结果并评定了校准不确定度。     

读数显微镜计量校准问题分析与解决

本文介绍了一种利用工具显微镜校准JC10型读数显微示值误差的方法,并通过测量不确定度评定验证这种方法的可行性。然后对JC10型读数显微镜在校准及使用中常遇的三个故障进行了分析与解决。     

高效液相色谱法测定乳及乳制品中三聚氰胺含量的不确定度评定

对国家质检总局发布的GB/T 22388-2008原料乳与乳制品中,三聚氰胺检测方法高效液相色谱法测定三聚氰胺的结果进行不确定度评定。通过建立数学模型,由鱼刺图逐层分析、计算了检测过程中引入的不确定度,运用最小二乘法对外标曲线拟合的不确定度进行评定,并将各不确定度进行合成,估计输出量接近正态分布,且有足够大自由度,取k=2计算扩展不确定度。该方法对采用外标法定量测定的气相色谱、液相色谱法具有参考意义。     

测定葡萄酒中合成着色剂含量的不确定度评定

通过对葡萄酒比对样品中四种合成着色剂同时测量的不确定度分析,建立了高效液相色谱梯度洗脱法同时测量多种组分不确定度的评定方法,并对测量过程中不确定度来源进行了详细分析和逐层合成.这种方法对液相色谱、气相色谱同时测定多组分不确定度评定具有重要的参考价值.     

痕量分析中校准曲线的探讨

在分析化学中,尤其是在痕量分析中,常常要作校准曲线.例如分光光度法和原子吸收法中作吸光度和浓度的校准曲线,极谱法中作波高和浓度的校准曲线,化学发光法中作相对发光强度和浓度的校准曲线等等,它是定量分析的直接依据,其好环直接影响分析结果的准确度.因此,校准曲线的绘制是痕量分析中非常重要的一个环节.痕量分析中常用的校准曲线大多数是直线.一般把实验点描在坐标纸上,横坐标表示被测物质的浓度,叫自变量(X);纵坐标表示测量的某种特征物理量,叫因变量(Y).在数理统计方法中,通常假设因变量是一组相互独立,且服从同一正态分布N(0,σ~2)的随机变量,然后根据坐标上的实验点(x_i,y_i)的走向,用直尺描出一条直线,这就是分析工作者习惯的绘制校准曲线的方法.从理论上讲,只有不存在实验误差时,即因变量完全依赖于自变量的改变而改变时,上述方法才是可行的.因为实验的随机误差是不可避免的,所有实验点完全落在同一直线上是不可能的,尤其是当实验误差较大,实验点较分散时,作图就困难了.用直尺根据实验点在坐标上直接作校准曲线,具有一定的主观性,可以作出无数条相近的校准曲线,但无法确定到底哪条是最好的.     

分光光度法测定污水中挥发酚的不确定度评定

为保证污水中挥发酚的检测质量,科学地评定检测结果的分散性,根据测量不确定度评定与表示的理论,评定了分光光度法测定城市污水中的挥发酚的测量不确定度。通过识别了测量过程中不确定的来源、分析各分量的产生、计算了该法的扩展不确定度U95=0.002 1 mg/L(k=2)。结果表明,合成标准不确定度主要来自仪器重复测定的分散性,其次是工作曲线拟合及样品前处理过程中引入的不确定度。因此,在运用该分析方法时,首要保证仪器运行的稳定性,提高检测的精密度,减少该过程输入的不确定度。此外,样品前处理在该测试中所引入的不确定度贡献也不可忽视。     

标准溶液稀释不确定度评定

依据测量不确定度评定与表示的理论,以砷标准溶液为例,对标准溶液稀释的不确定度进行了评定。通过识别稀释过程中的不确定度来源,分析了各个分量的产生,计算了合成标准不确定度。结果表明,移液器的不确定度是影响标准溶液稀释最主要的因素。     

直读光谱仪测量不锈钢中镍含量的不确定度评定

通过对直读谱仪测量不锈钢中镍含量不确定度的评定,分析了不确定度分量的主要来源,对各不确定度分量进行了评定.     

卡思卡特城堡

It is worthy of noting that, whilst Crookston Castle witnessed the earlier and happier portion of Mary's variegated life,     

Western and Eastern culture differences in commercial field

The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity.     

不同的吃喝玩乐

一、吃和喝吃苹果 eat an apple, 吃药 take medicine,吃糖 have some sweets,吃饭 have one's meals,吃馆子 dine out,吃惊 be surprised/     

漏洞百出的教育

Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help?     

只要努力,不要后悔

There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love.     

浅谈移民问题

Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject.     

风的曲线

Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose.     

团图为数的图中的闭团贯数

Given a graph G,a subgraph C is called a clique of G if C is a complete subgraph of G maximal under inclusion and |C|≥2. A clique-transversal set S of G is a set of vertices of G such that S meets all cliques of G. The clique-transversal number, denoted as TC (G), is the minimum cardinality of a clique-transversal set in G. The clique-graph of G, denoted as K (G), is the graph obtained by taking the cliques of G as vertices, and two vertices are adjacent if and only if the corresponding cliques in G have nonempty intersection. Let F be a class of graphs G such that F={G|K(G) is a tree}. In this paper the graphs in F having independent clique-transversal sets are shown and thus TC (G)/|G|≤1/2 for all G ∈ F.     

Sister Carrie, an Adherent of Desires

Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities.