Burn-in by environmental shocks for two ordered subpopulations

Burn-in is a widely used engineering method of elimination of defective items before they are shipped to customers or put into field operation. In conventional burn-in procedures, components or systems are subject to a period of simulated operation prior to actual usage. Then those which failed during this period are scrapped and discarded. In this paper, we assume that the population of items is composed of two ordered subpopulations and the elimination of weak items by using environmental shocks is considered. Optimal severity levels of these shocks that minimize the defined expected costs are investigated. Some illustrative examples are discussed.     

证券分析师会降低博彩型股票推荐评级吗？——来自我国A股市场的经验证据

博彩型股票具有“高风险”和“高投机性”的特点。本文以博彩型股票为研究对象,检验证券分析师是否会显著下调博彩型股票的推荐评级。在此基础上,探讨了投资者对博彩型股票推荐评级做出的反应及评级后的超额收益率情况。结果表明:分析师更可能下调博彩型股票的评级,但在投资者情绪高涨时,下调的可能性有所减小;投资者对分析师的博彩型股票评级存在反应过度的情况。本文结论对于认识证券分析师在资本市场中的作用具有重要的参考价值。     

Effects of Contrast and Character Size upon Legibility of Japanese Text Stimuli Presented on Visual Display Terminal

We examined effects of contrast and character size upon legibility of Japanese text stimuli presented on visual display terminal (VDT). In the experiment, three different character sizes were employed and the text stimulus was presented under a variety of conditions where contrast between the text and the background changed. Reading speed and the rate of readable characters were measured. Subjective rating for legibility was also evaluated. Results showed that legibility increases with luminance contrast for all character sizes examined here. A strong correlation was found between the subjective rating index and reading speed.     

Severity function describing the hydrolysis of xylan using carbonic acid

Beech wood derived xylan to hydrolyzed to predominantly xylose monomer units after exposure to hot, compressed liquid water saturated with carbon dioxide. Similar treatment without CO₂ saturation resulted in only minor hydrolysis and a smaller fraction of monomers among the hydrolysis products. Severity of the hydrolysis reaction was correlated to reaction time, temperature, and carbon dioxide partial pressure and followed a function similar to those used to characterize mineral acid systems. Results from parallel hydrolysis experiments with an aqueous system and a very dilute sulfuric acid system allowed an approximation of the dissociation constant of carbonic acid in the temperature range of 170–230°C. Results suggest that carbonic acid may be a viable reagent for promoting hydrolysis without mineral acids, especially in the case of a bioprocessing plant that produces carbon dioxide.     

SIR epidemic models with general infectious period distribution

We show how epidemics in which individuals’ infectious periods are not necessarily exponentially distributed may be naturally modelled as piecewise deterministic Markov processes. For the standard susceptible–infective–removed (SIR) model, we exhibit a family of martingales which may be used to derive the joint distribution of the number of survivors of the epidemic and the area under the trajectory of infectives. We also show how these results may be extended to a model in which the rate at which an infective generates infectious contacts may be an arbitrary function of the number of susceptible individuals present.     

IS/IT项目选择决策的灰色逼近理想解排序法

IS/IT项目选择决策是一个多属性决策问题.针对传统逼近理想解排序法(TOPSIS)在确定属性权重系数上的缺陷,并考虑到在实际IS/IT项目选择决策过程中部分决策信息的不足,提出了基于灰色TOPSIS改进算法.算法运用区间灰数表达指标权重和指标评价值,定义备择项目与正、负理想解的灰色关联度,依此计算各备则项目的贴近度并实现最终排序.仿真实例验证了该方法的合理和有效性.     

Risk-adjusted control charts for health care assessment

The recent Joint Commission on Accreditation of Healthcare Organization (JCAHO) requirement that hospital accreditation be based upon a Total Quality Management (TQM) approach has focused the attention of health care administrations on the use of techniques such as control charts. However, control charts are not typically adjusted for severity of illness. This adjustment is needed because, unlike industrial organizations, hospitals are not able to control all of their inputs and must accept variances in their patients. In this paper, we present a methodology for adjusting a health care organization's control charts to reflect their patient population's severity of illness during different time intervals. We then demonstrate that risk-adjusting expected patient outcomes can change our assessments of the relative quality of care offered by a health care organization in different time periods.     

Generalized linear models for dependent frequency and severity of insurance claims

Traditionally, claim counts and amounts are assumed to be independent in non-life insurance. This paper explores how this often unwarranted assumption can be relaxed in a simple way while incorporating rating factors into the model. The approach consists of fitting generalized linear models to the marginal frequency and the conditional severity components of the total claim cost; dependence between them is induced by treating the number of claims as a covariate in the model for the average claim size. In addition to being easy to implement, this modeling strategy has the advantage that when Poisson counts are assumed together with a log-link for the conditional severity model, the resulting pure premium is the product of a marginal mean frequency, a modified marginal mean severity, and an easily interpreted correction term that reflects the dependence. The approach is illustrated through simulations and applied to a Canadian automobile insurance dataset.     

偏t分布假设下的空间效应模型及其应用

在非寿险索赔强度预测中,目前使用最为广泛的是广义线性模型。索赔强度的广义线性模型假设因变量服从伽马分布或逆高斯分布,且在预测项中仅能考虑协变量的线性效应。这些限制性条件都有可能影响索赔强度预测结果的准确性。本文对索赔强度的广义线性模型进行了推广:用偏T分布代替常用的伽马分布和逆高斯分布;在预测项中引入惩罚样条函数来描述连续型协变量的非线性效应;考虑索赔强度在不同地区的差异性和相邻地区的相依性。最后基于一组实际的车损险数据进行了实证研究,结果表明,本文的推广模型可以明显提高索赔强度预测模型的拟合优度。     

Poly(ether–imide)/polyurethane foams reinforced with graphene nanoplatelet: Microstructure,thermal stability,and flame resistance

Novel poly(ether–imide)/polyurethane (PEI/PU)-based nanocomposite and foamed systems reinforced with graphene nanoplatelet (GNP) were developed. Field emission scanning electron microscopy revealed hexagonal nanocelluar morphology due to fine interaction between PEI/PU and functional GNP. Compression strength and modulus values were raised up to 72.3 MPa and 27.3 GPa, respectively, for PEI/PU/GNP Foam 1, thus revealing a defensive role of GNP layer against damage. T_max of PEI/PU/GNP Foam 0.1–1 was measured as 479–565°C. The UL 94 showed V-0 rating for nanocomposite, while foams attained V-1 rating. Water absorption capacity was improved steadily with time and was at maximum after 96 h for PEI/PU/GNP Foam 1 (12.3%).