The problem of defining changes in demographic old age in Poland in a spatial context

The author analyzes the demographic characteristics of the elderly population in Poland. The focus is on the spatial distribution of the elderly around the country.     

Demographic transformation in Poland

The author presents a general review of the demographic transition in Poland from 1750 to the present day. Official data are used to describe the fluctuations in birth and death rates over this period.     

A gold key to initiate a new situation in family planning work]

Because of the popularization of a responsible agricultural production system, the livilihood of peasants has been improving greatly, while the demands and needs of the general public are also increasing at the same time. Still under the influence of the traditional belief of carrying on one's family line and emphasis on having male children, married people prefer to have more childre, and the birth rate is now rising again. In order to solve this new problem, we need to teach the peasants national policies on population, land utilization, and food supply. In order to initiate a new situation in family planning work, we need to control this "gold key" of ideological education and propaganda. The emphasis should be placed on ideological education for cadres at all levels as well as the general public in order that they may understand the Party's strategy. Education on the national strategy should be combined with material interests of the peasants, and reward and punishment in production should also be linked up with that of family planning. Social measures are needed to reduce economic burdens of the peasants, offer better treatment for single-child households, and provide adequate care for old and retired people. Family planning projects should be consolidated and improved. Scientific management, facilities and techniques for birth control, compensation for working personnel in family planning, and other practical problems deserve immediate attention and solution.     

An integrated production and inventory model for a whole manufacturing supply chain involving reverse logistics with finite horizon period

This paper proposes a model and solution method for coordinating integrated production and inventory cycles in a whole manufacturing supply chain involving reverse logistics for multiple items with finite horizon period. A whole manufacturing supply chain involving reverse logistic consists of tier-2 suppliers supplying raw materials to tier-1 suppliers, tier-1 suppliers producing parts, a manufacturer which manufactures and assembles parts from tier-1 suppliers into finished products, distributors distributing finished products to retailers, retailers selling products to end customers and a third party which collects the used finished products from end customers, dissembles collected products into parts, and feed the parts back to the supply chain. In this system, we consider a finite horizon period. A mathematical model for representing the behaviors of the system is developed. Solution methods based on decentralized and a combination of decentralized and centralized decision making process, referred to as the semi-centralized decision making process, are proposed to solve the model while the centralized decision making process is solved by a mixed integer nonlinear programming method. A numerical example is used to demonstrate the model and the solutions based on the three types of the coordination.     

A nonparametric hypothesis test for heteroscedasticity

In this paper, a hypothesis test for heteroscedasticity is proposed in a nonparametric regression model. The test statistic, which uses the residuals from a nonparametric fit of the mean function, is based on an adaptation of the well-known Levene's test. Using the recent theory for analysis of variance when the number of factor levels goes to infinity, the asymptotic distribution of the test statistic is established under the null hypothesis of homocedasticity and under local alternatives. Simulations suggest that the proposed test performs well in several situations, especially when the variance is a nonlinear function of the predictor.     

Subsampling-extrapolation bandwidth selection in bivariate kernel density estimation

This paper focuses on bivariate kernel density estimation that bridges the gap between univariate and multivariate applications. We propose a subsampling-extrapolation bandwidth matrix selector that improves the reliability of the conventional cross-validation method. The proposed procedure combines a U-statistic expression of the mean integrated squared error and asymptotic theory, and can be used in both cases of diagonal bandwidth matrix and unconstrained bandwidth matrix. In the subsampling stage, one takes advantage of the reduced variability of estimating the bandwidth matrix at a smaller subsample size m (m < n); in the extrapolation stage, a simple linear extrapolation is used to remove the incurred bias. Simulation studies reveal that the proposed method reduces the variability of the cross-validation method by about 50% and achieves an expected integrated squared error that is up to 30% smaller than that of the benchmark cross-validation. It shows comparable or improved performance compared to other competitors across six distributions in terms of the expected integrated squared error. We prove that the components of the selected bivariate bandwidth matrix have an asymptotic multivariate normal distribution, and also present the relative rate of convergence of the proposed bandwidth selector.     

Prediction of future failures times based on Type-I hybrid censored samples of random sample sizes

In this article, we consider the prediction of future failure times based on Type-I hybrid censored samples. Point predictors and prediction intervals using different procedures are discussed for a general model. The exponential and Rayleigh distributions are used as illustrative examples to show the most simplified forms of the so obtained predictors as well as prediction intervals. Intensive simulation study and a real life dataset are presented to illustrate our findings and results.