Tables to Facilitate Fitting Tadikamalla and Johnson's LB Distributions

This paper is concerned with estimating the parameters of Tadikamalla-Johnson's L_B distribution using the first four moments. Tables of the parameters of the L_B distribution are given for selected values of skewness (0.0(0.05) 1.0(0.1)2.0) and corresponding available values of kurtosis at intervals of 0.2. The construction and use of these tables is explained with a numerical example.     

Combining Univariate Tests for Multivariate Location Problem

In this article, three methods of combining dependent univariate tests are studied. The Bahadur approximate efficiencies are derived under the asymptotic normal assumption. These procedures are applied to the multivariate location problem and compared with two Hotelling-type tests. A Monte Carlo study indicates that in certain cases the powers of the combination methods are much better than Hotelling's T ² and other multivariate nonparametric tests.     

A Bivariate Distribution for the Reliability Analysis of Failure Data in Presence of a Forewarning or Primer Event

This article presents a bivariate distribution for analyzing the failure data of mechanical and electrical components in presence of a forewarning or primer event whose occurrence denotes the inception of the failure mechanism that will cause the component failure after an additional random time. The characteristics of the proposed distribution are discussed and several point estimators of parameters are illustrated and compared, in case of complete sampling, via a large Monte Carlo simulation study. Confidence intervals based on asymptotic results are derived, as well as procedures are given for testing the independence between the occurrence time of the forewarning event and the additional time to failure. Numerical applications based on failure data of cable insulation specimens and of two-component parallel systems are illustrated.     

On the Alias Method for Generating Random Variables from a Discrete Distribution

The alias method of Walker is a clever, new, fast method for generating random variables from an arbitrary, specified discrete distribution. A simple probabilistic proof is given, in terms of mixtures, that the method works for any discrete distribution with a finite number of outcomes. A more efficient version of the table-generating portion of the method is described. Finally, a brief discussion on efficiency of the method is given. We believe that the generality, speed, and simplicity of the method make it attractive for use in generating discrete random variables.     

A Spectral Method for a Nonpreemptive Priority BMAP/G/1 QUEUE

Abstract

In this paper we consider a nonpreemptive priority queue with two priority classes of customers. Customers arrive according to a batch Markovian arrival process (BMAP). In order to calculate the boundary vectors we propose a spectral method based on zeros of the determinant of a matrix function and the corresponding eigenvectors. It is proved that there are M zeros in a set Ω, where M is the size of the state space of the underlying Markov process. The zeros are calculated by the Durand-Kerner method, and the stationary joint probability of the numbers of customers of classes 1 and 2 at departures is derived by the inversion of the two-dimensional Fourier transform. For a numerical example, the stationary probability is calculated.     

Workload Process,Waiting Times,and Sojourn Times in a Discrete Time MMAP[K]/SM[K]/1/FCFS Queue

Abstract

In this paper, we study the total workload process and waiting times in a queueing system with multiple types of customers and a first-come-first-served service discipline. An M/G/1 type Markov chain, which is closely related to the total workload in the queueing system, is constructed. A method is developed for computing the steady state distribution of that Markov chain. Using that steady state distribution, the distributions of total workload, batch waiting times, and waiting times of individual types of customers are obtained. Compared to the GI/M/1 and QBD approaches for waiting times and sojourn times in discrete time queues, the dimension of the matrix blocks involved in the M/G/1 approach can be significantly smaller.     

A consistent method of estimation for the parameters of the three-parameter inverse Gaussian distribution

In this paper, we propose a consistent method of estimation for the parameters of the three-parameter inverse Gaussian distribution. We then discuss some properties of these estimators and show by means of a Monte Carlo simulation study that the proposed estimators perform better than some other prominent estimators in terms of bias and root mean squared error. Finally, we present two real-life examples to illustrate the method of inference developed here.     

中国产业链供应链现代化水平的区域差异及收敛性研究

提升产业链供应链现代化水平是推动经济体系优化升级的重点任务。论文首先界定了产业链供应链现代化的内涵,并根据其内涵构建综合评价指标体系。然后,研究2011—2020年产业链供应链现代化水平的分布动态、区域差异与空间收敛性。结果表明：我国产业链供应链现代化水平在空间上呈现出“东高、中西低”的阶梯状空间分布特征;区域产业链供应链现代化水平差异主要来源于区域间差异,而区域间差异主要来源于东部-中部和东部-西部的地区差异;全国及各区域产业链供应链现代化水平在空间上无明显σ收敛特征,全国及各区域存在显著的绝对β收敛和条件β收敛,表明各区域朝着自身稳定状态发展。最后根据研究结果,提出关于产业链供应链现代化水平提升的对策建议。     

生产环节外包能否助力中国粮食安全？——来自粮食主产区的证据

在中国大力扶持和推进生产环节外包服务业发展的现实背景下,系统评估生产环节外包对中国粮食安全的影响具有重要的现实意义。聚焦粮食安全数量目标与环境目标两个维度,从农户是否参与外包、农户的外包横向参与度与农户的外包纵深参与度三个层面,理论剖析生产环节外包影响中国粮食安全的逻辑机理,并使用中国粮食主产区1211户农户的抽样调查数据和CMP方法进行实证检验。研究发现：①从三大主粮的总体估计来看,生产环节外包有助于中国粮食安全数量目标的实现,但不利于中国粮食安全环境目标的达成。在解决潜在的内生性问题后,这一结论依然成立;②从玉米、小麦和水稻的分样本估计来看,生产环节外包对中国粮食安全的多维影响在玉米和水稻生产中仍较为稳健,但对小麦的增产效果并不明显;从黑龙江、河南和湖南的分样本估计来看,生产环节外包对中国粮食安全的多维影响在三大粮食主产省均较为稳健。目前,从服务视角破解资源环境约束与农户行为约束暂未成为解决中国粮食安全环境问题的有效途径,仍需进一步推动生产环节外包服务市场的发育与完善,鼓励并引导外包供给主体的绿色生产导向。