肥料中有机质分析方法的探讨

探讨肥料中有机质的分析方法。通过对两个肥料标准中有机质的分析方法进行比较，对各标准中有机质检验过程中的影响因素进行了分析，确定了本地区有机肥料中有机质适宜的分析方法。     

Assessing the performance of normal-based and REML-based confidence intervals for the intraclass correlation coefficient

Using normal distribution assumptions, one can obtain confidence intervals for variance components in a variety of applications. A normal-based interval, which has exact coverage probability under normality, is usually constructed from a pivot so that the endpoints of the interval depend on the data as well as the distribution of the pivotal quantity. Alternatively, one can employ a point estimation technique to form a large-sample (or approximate) confidence interval. A commonly used approach to estimate variance components is the restricted maximum likelihood (REML) method. The endpoints of a REML-based confidence interval depend on the data and the asymptotic distribution of the REML estimator. In this paper, simulation studies are conducted to evaluate the performance of the normal-based and the REML-based intervals for the intraclass correlation coefficient under non-normal distribution assumptions. Simulated coverage probabilities and expected lengths provide guidance as to which interval procedure is favored for a particular scenario. Estimating the kurtosis of the underlying distribution plays a central role in implementing the REML-based procedure. An empirical example is given to illustrate the usefulness of the REML-based confidence intervals under non-normality.     

Reliability of Space-Shuttle Pressure Vessels With Random Batch Effects

In this article we revisit the problem of estimating the joint reliability against failure by stress rupture of a group of fiber-wrapped pressure vessels used on Space-Shuttle missions. The available test data were obtained from an experiment conducted at the U.S. Department of Energy Lawrence Livermore Laboratory (LLL) in which scaled-down vessels were subjected to life testing at four accelerated levels of pressure. We estimate the reliability assuming that both the Shuttle and LLL vessels were chosen at random in a two-stage process from an infinite population with spools of fiber as the primary sampling unit. Two main objectives of this work are (1) to obtain practical estimates of reliability taking into account random spool effects and (2) to obtain a realistic assessment of estimation accuracy under the random model. Here, reliability is calculated in terms of a “system” of 22 fiber-wrapped pressure vessels, taking into account typical pressures and exposure times experienced by Shuttle vessels. Comparisons are made with previous studies. The main conclusion of this study is that, although point estimates of reliability are still in the “comfort zone,” it is advisable to plan for replacement of the pressure vessels well before the expected lifetime of 100 missions per Shuttle Orbiter. Under a random-spool model, there is simply not enough information in the LLL data to provide reasonable assurance that such replacement would not be necessary.     

Estimation and prediction from gamma distribution based on record values

In this paper, we introduce the record values arising from gamma distribution with three parameters. Next, we compute the means, variances and covariances of the lower record values. Then, we use these moments to calculate the best linear unbiased estimates (BLUEs) for the location and scale parameters of gamma distribution. By using the BLUEs, we construct confidence intervals for the location and scale parameters through Monte Carlo simulations. In addition, we discuss the point and interval prediction for the future records.     

Prediction Limits for the Inverse Gaussian Distribution

Prediction intervals for the inverse Gaussian are obtained from both a frequentist and a Bayesian viewpoint. The frequentist intervals are obtained by constructing pivotals that have the x ² and F distributions. The method involves inversion of probability statements, which results in two-sided prediction intervals. A Bayesian predictive density is obtained using a vague prior, from which one- or two-sided Bayesian prediction intervals can be determined. An example for which Bayesian prediction limits are narrower than the frequentist is given.     

A study of two estimation approaches for parameters of Weibull distribution based on WPP

Least-squares estimation (LSE) based on Weibull probability plot (WPP) is the most basic method for estimating the Weibull parameters. The common procedure of this method is using the least-squares regression of Y on X, i.e. minimizing the sum of squares of the vertical residuals, to fit a straight line to the data points on WPP and then calculate the LS estimators. This method is known to be biased. In the existing literature the least-squares regression of X on Y, i.e. minimizing the sum of squares of the horizontal residuals, has been used by the Weibull researchers. This motivated us to carry out this comparison between the estimators of the two LS regression methods using intensive Monte Carlo simulations. Both complete and censored data are examined. Surprisingly, the result shows that LS Y on X performs better for small, complete samples, while the LS X on Y performs better in other cases in view of bias of the estimators. The two methods are also compared in terms of other model statistics. In general, when the shape parameter is less than one, LS Y on X provides a better model; otherwise, LS X on Y tends to be better.     

Pivotal inference and the Bayesian controversy

Summary The theory of pivotal inference applies when parameters are defined by reference to their effect on observations rather than their effect on distributions. It is shown that pivotal inference embraces both Bayesian and frequentist reasoning.     

PJM电力市场三寡头垄断测试法

美国PJM电力市场组织结构先进完善,运营取得了较好效果,并基于市场运行经验,针对电力市场运行建立了一套比较完整的市场监管机制。其中,"三寡头垄断测试"是PJM监管电力市场运行,抑制发电商行使市场力,防范电力市场风险的有效方法之一。介绍了PJM电力市场"三寡头垄断测试法"的基本原理和方法,为电力市场的有效运行及监管制度的建设完善提供参考。     

基于支持向量机的两阶段模糊聚类在视频检索中的应用

针对视频检索应用中面临的高维特征分析问题,提出了一种能提高查全率和查准率的两阶段模糊聚类方案.该方案首先在保证查全率的前提下用颜色距离直方图进行粗粒度的视频切分,得到包含冗余信息的关键视频帧;然后通过模糊支持向量机进行细粒度聚类,以提高查准率;最后运用全局关联的数据挖掘方法去除冗余得到与用户语义相关的信息.实验表明,算法在实时视频检索的应用中能显著提高查全率和查准率.