不偏性

There are two findings summarized from previous studies:(1) the least squares estimator is a common choice of researchers, but under an unequal probability design, the estimator is biased,(2) the probability weighted estimator is consistent but may have a large variance.

过去的研究发现：(1)在不等机率抽样时，一般常用的最小平方法所得到的回归参数估计式并非不偏估计式；(2)机率加权最小平方法可以改善不偏性，然却增加估计的变异程度。

However, MLE is a biased estimator of the fold change and minimum variance estimator of the fold change exists under the log-normal distribution.

然而相对表现量在对数常态分布时应用最小变异不偏估计法较 MLE 具有不偏性和最小变异。

The nonexistence of global weak solution to elliptic equation and the evolution equation, together with the nonexistence of local weak solution to hyperbolic equation is contained in this paper.

本文运用试验函数法研究了带有非局部源的偏微分方程的全局弱解的不存在性，内容包括椭圆方程、发展方程全局解的不存在性以及双曲型方程的局部弱解的不存在性。

The simulation results also find that the Quasi-Aitken weighted least squares estimator has a smaller asymptotic variance than least squares estimator.

研究结果显示机率加权最小平方法与Quasi-Aitken机率加权最小平方法的回归参数估计式皆具有不偏性，其中Quasi-Aitken机率加权最小平方法的回归参数估计式的变异最小。

ISO834 and parametric equation approach are lack of pertinence. The results may be too conservative. The temperature obtained by zone model is low, so that it is not suitable for the performance-based fire protection design on this structure. Field model considers the heterogeneity of environmental temperature, and its result is close to the real fire, so that it is commended to the performance-based fire protection design on steel staggered-truss structure.

国际标准升温曲线和参数化室内升温曲线不考虑火源功率、建筑通风口等因素，缺乏针对性，分析结果偏于保守；区域模型所得温度偏低，不宜用于交错桁架结构的性能化抗火设计；场模型考虑了火源功率及环境温度分布的不均匀性，和实际火灾较接近，计算结果相对较为准确，可用于结构的性能化防火设计。

Based on Monte Carlo method,four different weighted function moment methods for Pearson Ⅲ distribution which were developed in China are first compared by using the evaluation standard considering unbiasness and effectiveness of parameters and design values.

利用统计试验方法，以参数及设计值不偏性、有效性为评价标准，比较了现行几种权函数参数估计法，结果与以理想样本还原准则为标准所得的结论截然相反，以不偏性、有效性标准的结论是数值积分权函数法，并未对马秀峰权函数法作出改进，还从理论上比较分析以上两种评价标准，结论是理想样本还原为标准来评判估计方法的优劣存在较大缺陷，建议今后尽量不要使用该标

Variational identity play a important role to prove nonexistence and get prior estimate of solution, In this thesis, we study following parts on the relationship of symmetry group of partial differential equations with variational structure and the variational identity.

变分恒等式在证明具有变分结构偏微分方程解的不存在性以及得到方程解的先验估计时有着非常重要的作用，本文研究了一些具有变分结构偏微分方程的对称群与其变分恒等式的关系。

The results show that under the condition of the experiments, the high KOH concentration is benefit to the formation of soluble niobate, but the high temperature is favor of the formation of insoluble niobate, and the insoluble tantalate is the sole leachin...

而KOH浓度一定，温度升高，有利于生成偏铌酸钾。浸出时间过长也将促使不溶性偏铌酸钾的形成。试验条件下，Ta2 O5在KOH高浓介质体系中只得到不溶性的偏钽酸钾。Nb2 O5和Ta2 O5混合物的浸出规律与纯Nb2 O5类似，铌、钽不能被选择性地浸出。

Proof of unbiasedness depends on our 4 assumptions – if any assumption fails, then OLS is not necessarily unbiased

无偏性的证明依赖于我们的四个假定--如果任何假定不成立，OLS未必是无偏的

Secondly, the paper carries on the destruction processes and the stress distribution situation numerical simulation of the concrete three point bending specimen with bias crack under static load function,, and analyze specimen crack expansion and the destruction mechanism, obtain the reason that the crack expanding flectional way is because the material nonuniformity, in the same time, from the specimen destruction process chart we can see that the crack bias degree has some influence on the crack expansion way.

其次论文对含偏置裂纹的混凝土三点弯曲试件在静态载荷作用下的破坏过程和应力分布情况进行了数值模拟，并对试件的裂纹扩展和破坏机理进行了分析，得出裂纹扩展的曲折性是由于材料不均匀性所引起的，同时从试件的破坏过程图中可以看出，裂纹的偏置程度对裂纹的扩展路径有一定的影响。

This one mode pays close attention to network credence foundation of the businessman very much.

这一模式非常关注商人的网络信用基础。

Cell morphology of bacterial ghost of Pasteurella multocida was observed by scanning electron microscopy and inactivation ratio was estimated by CFU analysi.

扫描电镜观察多杀性巴氏杆菌细菌幽灵和菌落形成单位评价遗传灭活率。