用工业CT技术测量储层岩芯饱和度分布

认识储层岩石中含油饱和度及饱和度分布,对驱替机理的深入研究是非常重要的。为了搞清储层岩石在驱替过程中的饱和度分布情况,应用工业CT技术,提出了一种储层含油岩芯被驱替后的饱和度分布的CT密度差测量方法。在岩样的同一断面,分别对干岩样、饱和岩样及在驱替后的岩样进行CT扫描,重建相应的断层图象,测量所建图象的灰度值,计算出相应的密度值,用密度差法计算出饱和度及其分布值。在γ射线工业CT机“CD-300BG”上对某油田岩样进行了实际测量,获得的结果说明,采用CT密度差法测量饱和度分布是有效的。该方法与常规驱替法相比较,具有快速、精度高、无损岩样和能模拟地层状态测量等特点,是油田开发、油藏描述和地层评价的一种新的有效方法。     

An Additive–Multiplicative Restricted Mean Residual Life Model

The mean residual life measures the expected remaining life of a subject who has survived up to a particular time. When survival time distribution is highly skewed or heavy tailed, the restricted mean residual life must be considered. In this paper, we propose an additive–multiplicative restricted mean residual life model to study the association between the restricted mean residual life function and potential regression covariates in the presence of right censoring. This model extends the proportional mean residual life model using an additive model as its covariate dependent baseline. For the suggested model, some covariate effects are allowed to be time‐varying. To estimate the model parameters, martingale estimating equations are developed, and the large sample properties of the resulting estimators are established. In addition, to assess the adequacy of the model, we investigate a goodness of fit test that is asymptotically justified. The proposed methodology is evaluated via simulation studies and further applied to a kidney cancer data set collected from a clinical trial.     

The exponential–Weibull lifetime distribution

In this paper, we propose a new three-parameter model called the exponential–Weibull distribution, which includes as special models some widely known lifetime distributions. Some mathematical properties of the proposed distribution are investigated. We derive four explicit expressions for the generalized ordinary moments and a general formula for the incomplete moments based on infinite sums of Meijer's G functions. We also obtain explicit expressions for the generating function and mean deviations. We estimate the model parameters by maximum likelihood and determine the observed information matrix. Some simulations are run to assess the performance of the maximum likelihood estimators. The flexibility of the new distribution is illustrated by means of an application to real data.     

General results for the Kumaraswamy-G distribution

For any continuous baseline G distribution [G.M. Cordeiro and M. de Castro, A new family of generalized distributions, J. Statist. Comput. Simul. 81 (2011), pp. 883–898], proposed a new generalized distribution (denoted here with the prefix ‘Kw-G’ (Kumaraswamy-G)) with two extra positive parameters. They studied some of its mathematical properties and presented special sub-models. We derive a simple representation for the Kw-G density function as a linear combination of exponentiated-G distributions. Some new distributions are proposed as sub-models of this family, for example, the Kw-Chen [Z.A. Chen, A new two-parameter lifetime distribution with bathtub shape or increasing failure rate function, Statist. Probab. Lett. 49 (2000), pp. 155–161], Kw-XTG [M. Xie, Y. Tang, and T.N. Goh, A modified Weibull extension with bathtub failure rate function, Reliab. Eng. System Safety 76 (2002), pp. 279–285] and Kw-Flexible Weibull [M. Bebbington, C.D. Lai, and R. Zitikis, A flexible Weibull extension, Reliab. Eng. System Safety 92 (2007), pp. 719–726]. New properties of the Kw-G distribution are derived which include asymptotes, shapes, moments, moment generating function, mean deviations, Bonferroni and Lorenz curves, reliability, Rényi entropy and Shannon entropy. New properties of the order statistics are investigated. We discuss the estimation of the parameters by maximum likelihood. We provide two applications to real data sets and discuss a bivariate extension of the Kw-G distribution.     

高校思想政治教育网络教育手段的理性分析

网络技术运用于高校思想政治教育,不仅丰富了思想政治教育的途径和方式,而且也有效地拓展了思想政治教育的空间。但是由于思想观念、技术水平的差异性,网络为思想政治教育提供的手段并没有得到充分地开发利用。因此,大胆实施改革创新,不断完善网络教育手段和方式,是促使思想政治教育功能得以最大程度发挥的重要基础。     

Estimation of weibull location

A simulation study was carried out to compare the performances of two different simple estimators of the location parameter for a three-parameter Weibull distribution Both Estimators have been suggested by recent paper in the literature. Bras and mean square error are examined for many different sample-size and shape-parameter-value combinations. Strong evidence of the domination of one estimator over the other is found.     

非期望产出下我国能源消耗产出效率差异研究

提高能源消耗产出效率是新常态下经济发展的必然趋势，随机扰动和外部环境是研究能源消耗产出效率不可回避的问题，而传统的DEA模型无法剔除非期望产出对效率值的影响。本文通过构建四阶段Bootstrap-DEA-Malmquist模型，采用1990~2014年的省际面板数据作为样本数据，通过松弛指标调整能源投入，剔除外部环境和随机因素对能源效率和能源全要素生产率的扰动，并借助Bootstrap随机抽样法进一步减小由于样本差异造成的影响，从静态和动态两个维度测算了中国能源消耗产出效率和全要素生产率。研究发现，外部环境和随机扰动对能源效率的估算具有显著影响，剔除外部环境影响因素后得到的能源效率值、技术效率变化以及全要素生产率变动均有不同程度的下降，而调整初始投入后的技术进步值有所上升。此外，考虑环境因素时，能源效率值下降，但是进一步运用Bootstrap随机抽样法消除随机因素的影响后，能源效率值有所上升。本文的主要贡献在于将环境因素和随机因素从能源效率与能源全要素生产率的测算中剥离，获得更为准确的能源效率值和能源全要素生产率值。     

A note on the mean residual life of a coherent system with a cold standby component

In this paper, we investigate the effect of a cold standby component on the mean residual life (MRL) of a system. When the system fails, a cold standby component is immediately put in operation. We particularly focus on the coherent systems in which, after putting the standby component into operation, the failure of the system is due to the next component failure. For these systems, we define MRL functions and obtain their explicit expressions. Also some stochastic ordering results are provided. Such systems include k-out-of-n systems. Hence, our results extend some results in literature.     

Optimal design of repetitive group sampling plans for Weibull and gamma distributions with applications and comparison to the Birnbaum–Saunders distribution

In this paper, we propose a multiple deferred state repetitive group sampling plan which is a new sampling plan developed by incorporating the features of both multiple deferred state sampling plan and repetitive group sampling plan, for assuring Weibull or gamma distributed mean life of the products. The quality of the product is represented by the ratio of true mean life and specified mean life of the products. Two points on the operating characteristic curve approach is used to determine the optimal parameters of the proposed plan. The plan parameters are determined by formulating an optimization problem for various combinations of producer's risk and consumer's risk for both distributions. The sensitivity analysis of the proposed plan is discussed. The implementation of the proposed plan is explained using real-life data and simulated data. The proposed plan under Weibull distribution is compared with the existing sampling plans. The average sample number (ASN) of the proposed plan and failure probability of the product are obtained under Weibull, gamma and Birnbaum–Saunders distributions for a specified value of shape parameter and compared with each other. In addition, a comparative study is made between the ASN of the proposed plan under Weibull and gamma distributions.     

A new estimator of proportion with a linear function using data from two-decks randomized response model

A new estimator for estimating the proportion of a potentially sensitive attribute in survey sampling has been introduced by solving a linear equation. The proposed estimator has been compared with the estimator proposed by Odumade and Singh (2009) with equal protection to all of the respondents. The asymptotic properties of the proposed estimator are investigated through exact numerical illustrations for different choices of parameters. A non randomized response approach has been suggested. A scope for further research has also been pointed out.