概率准则下的投资决策与有效边界间的关系

本文在证券收益率服从正态分布的前提下,对于允许卖空与不允许卖空这两种情况,分别讨论了概率准则下的投资决策与有效边界间的关系,并举例予以了说明。     

基于遗传算法的概率准则组合证券模拟求解

针对概率准则意义下的组合证券投资模型,采用随机模拟技术和遗传算法相结合的思 想, 设计出求解算法, 并用Matlab 语言实现. 求解算法适用于证券收益率服从任意分布的情 况, 甚至不考虑证券收益率分布, 用实际数据进行模拟和优化. 实例证明, 该算法有很好的 收敛性及较高的计算效率.     

基准收益与证券投资的认知风险

基准收益率是证券投资决策过程中需要考虑的一个重要概念。本文基于投资者的过度自信心理构建了考虑基准收益率的证券投资认知风险模型，研究了基准收益率与证券投资认知风险的关系．研究结论表明：证券投资的基准收益率大小与证券投资的认知风险为正相关关系。     

竞争条件下企业战略投资时机的实物期权分析

在企业战略投资机会可共享可延迟情况下,引入投资成本、未来投资收益率及其波动率、投资延迟损失率、竞争企业之间的相关度等比较容易估算的假设变量,构建实物期权分析框架,量化分析企业战略投资的相对收益率区间、投资时间、投资的两阶段博弈概率.通过模型推导与数值分析,检验各假设变量的变化对投资时机的影响.最后,运用我国二家上市公司战略投资决策的实例验证了模型的实用性与有效性.     

展望理论的权重函数与证券收益率分布

证券收益率的概率受到投资者主观判断概率的影响,从而形成“尖峰厚尾”等形态特征。在展望理论的权重函数的基础上,建立了收益率分布主观概率模型,对收益率分布的“厚尾分布”、中部形态及整体形态特征进行了理论推导。并利用深圳证券市场的441支股票的实际收益率分布的概率形态进行了实证分析,实证检验的结果与提出的模型所推导的特征性质得到了一致的吻合。     

一种证券收益与风险动态模型的辨识方法

在假设证券瞬时收益率满足伊藤随机微分方程的基础上, 把证券的收益和风险分别定义为瞬时收益率的数学期望和方差. 通过利用柯尔莫哥洛夫(Ko lmogo rov) 方程, 推导出了证券收益与风险所满足的微分方程, 并且基于非参数估计理论为证券瞬时收益率方程提供了一种参数辨识方法. 最后, 把这种建模与辨识方法应用于中国证券市场的分析中, 并给出了仿真结果.     

基于贷款风险损失比的农户信贷模型与应用

在农户信用评级基础上,研究基于银行贷款风险损失比的农户信用贷款决策模型以及银行相应的信用贷款利率机制.通过以农户个体合理性和银行最大可接受的贷款风险损失比作为约束条件,分别在农户项目成功概率对银行期望收益的影响以及农户项目成功概率同时对银行期望收益和农户期望收益都产生影响两种不同情形的假设下,建立了相应的农户信用贷款决策模型,给出了两种不同的银行最优贷款利率机制.本文还举出实例,针对5级分类中农户不同的信用等级以及相应所获得的银行贷款授信,设计了4组不同的组合数据,分别在贷款申请金额、农户自有财富、银行最大可接受的贷款损失比以及农户项目期望收益率发生不同的变化时,农户最优项目成功概率以及银行最优贷款利率发生的变化.讨论了在银行不同的贷款利率下农户项目净期望收益率的变化以及农户项目期望收益率的合理区间.     

投资组合中多目标规划最优化数学模型的应用

本文通过对证券组合投资的预期收益率和投资风险进行综合定量分析,建立了证券组合投资的预期收益率和投资风险进行综合定量分析,建立了证券组合投资的预期收益率和投资风险两个目标均达到最优的多目标规划模型,并对模型进行分析,最后通过案例给出了模型的最优解。     

阶段性投资最优比例问题的实物期权方法

以研发成功的初创企业为例,针对两阶段投资决策问题,描述了柔性决策所具有的实物 期权思想,根据相应的投资准则得到项目决策的执行概率,再结合项目收益过程的分析,建立 起包括决策柔性价值在内的项目总价值的数学模型. 在此基础上可以分析投资比例对项目价 值的影响,并得到最优值. 文章结合案例进行了数值计算,并对结果做了分析.     

绝对离差证券组合投资模型及其模拟退火算法

马柯维兹均值—方差模型使用收益率的方差度量证券的风险, 但是实际分布呈尖顶胖尾 状, 使得方差可能不存在. 作为度量风险的标准, 绝对离差比方差更为合适. 用绝对离差刻画了 风险, 提出基于绝对离差的证券组合投资模型, 并用模拟退火算法求解. 为了比较在两种风险 标准下两种模型的优劣, 首次定义了风险弹性. 实证分析表明, 在不同收益率水平下, 风险弹性 的绝对值都大于1. 说明绝对离差模型比均值- 方差模型无论在理论上还是在实际效果上都要 更好. 实证分析还表明, 绝对离差模型中有近似的两基金分离现象存在.     

Criteria for selecting a production control philosophy

Logistic objectives constitute a compromise between having short leadtimes and a low volume of work in progress on the one hand and a high resource loading and due date obligation on the other. Miscellaneous production planning approaches offered today provide different combinations of logistic objectives for satisfying a manufacturing strategy. To combine the strength of the various approaches into a unified system, a new approach based on a dynamic and distributed production planning methodology is proposed. To customize the approach, various analyses and specifications have to be made and for that reason some important characteristics and criteria for analysing production control philosophies will be given.     

The social construction of the meaning of acute stressors: a qualitative study of the personal accounts of police officers using a stress counselling service

The police profession is one in which acute stressors are encountered more frequently than in other occupations. Using the personal accounts of 35 police officers attending an in-house stress counselling clinic, the aim of the present study was to provide a qualitative examination of how the institutional context of policing influenced the ways in which acute stressors signified to individual police officers experiencing felt distress. Using the framework of Rational Emotive Behaviour Therapy as an analytical tool, it is argued that beliefs contributing to the experience of felt distress are related to the way in which policing as both an identity and an activity is constructed through the police organizational culture. Not only do these constructions influence the ways in which officers perceive themselves and their environments, but they also operate at the collective level to 'normalize' some emotional responses and to 'pathologize' others which, it is argued, could impact upon the outcomes of interventions such as stress counselling.     

The moderating role of social support in Karasek's job strain model

This paper examines whether social support is a boundary-determining criterion in the job strain model of Karasek (1979). The particular focus is the extent to which different sources of social support, work overload and task control influence job satisfaction, depersonalization and supervisor assessments of work performance. Hypotheses are tested using prospective survey data from 80 clerical staff in a university setting. Results revealed 3-way interactions among levels of support (supervisor, co-worker, non-work), perceived task control and work overload on levels of work performance and employee adjustment (self-report). After controlling for levels of negative affect in all analyses, there was evidence that high levels of supervisor support mitigated against the negative effects of high strain jobs on levels of job satisfaction and reduced reported levels of depersonalization. Moreover, high levels of non-work support and co-worker support also mitigated against the negative effects of high strain jobs on levels of work performance. The results are discussed in terms of the importance of social support networks both at, and beyond, the work context.     

Job insecurity, coping resources and personality dispositions in occupational strain

This paper presents research on the relationships between the work-related stressor of perceived job insecurity and various indicators of occupational strain, taking into account employees' personality dispositions (trait negative and positive affectivity) and coping resources. Respondents were 222 Australian public servants surveyed during organizational restructuring that involved downsizing and threat to job certainty. The research was formulated within an adaptation of Osipow, Doty, and Spokane's (1985) framework of stress-strain-coping that included the possible direct as well as moderating effects of personality dispositions in reporting occupational strain (Parkes, 1990). Findings from hierarchical regression analyses indicate consistent significant independent effects of personality dispositions, coping resources and perceived job insecurity on various indicators of strain. There was also support for the moderating roles of negative affectivity and self-care in the relation between perceived job insecurity and physical strain. Implications for the role of dispositional factors, especially negative affectivity, and the utility of various coping resources in accounting for occupational strain in times of threatened job security are discussed.     

Introduction to Special Section on Sensitivity Analysis and Summary of NCSU/USDA Workshop on Sensitivity Analysis

This guest editorial is a summary of the NCSU/USDA Workshop on Sensitivity Analysis held June 11–12, 2001 at North Carolina State University and sponsored by the U.S. Department of Agriculture's Office of Risk Assessment and Cost Benefit Analysis. The objective of the workshop was to learn across disciplines in identifying, evaluating, and recommending sensitivity analysis methods and practices for application to food‐safety process risk models. The workshop included presentations regarding the Hazard Assessment and Critical Control Points (HACCP) framework used in food‐safety risk assessment, a survey of sensitivity analysis methods, invited white papers on sensitivity analysis, and invited case studies regarding risk assessment of microbial pathogens in food. Based on the sharing of interdisciplinary information represented by the presentations, the workshop participants, divided into breakout sessions, responded to three trigger questions: What are the key criteria for sensitivity analysis methods applied to food‐safety risk assessment? What sensitivity analysis methods are most promising for application to food safety and risk assessment? and What are the key needs for implementation and demonstration of such methods? The workshop produced agreement regarding key criteria for sensitivity analysis methods and the need to use two or more methods to try to obtain robust insights. Recommendations were made regarding a guideline document to assist practitioners in selecting, applying, interpreting, and reporting the results of sensitivity analysis.     

Job stress, job strain, and psychological withdrawal among Dutch university staff: towards a dualprocess model for the effects of occupational stress

This study examined the antecedents of job strain (emotional exhaustion, health complaints) and withdrawal behaviour (e.g. lowered organizational commitment) among a cross-sectional sample of 131 academic staff members of the law department of a large Dutch university. Conservation of resources theory (Hobfoll, 1989) provided the theoretical background for this study. Strains and withdrawal behaviours were expected to be most prominent among those who reported having few resources and/or who reported high job demands. Structural equation modelling revealed that this was indeed the case. As predicted, differential patterns of effects emerged for job demands and job resources. Analysis of the effects of four job-specific stressors revealed that especially the structural aspects of a staff member's teaching task (e.g. the number of students in their classes) contributed strongly to perceived job demands. Theoretical and practical implications of the study are discussed.     

Distinguishing traumatic, vicarious and routine operational stressor exposure and attendant adverse consequences in a sample of police officers

Problems in studying occupational stress within the police service are identified and the paucity of work on operational duties as potential stressors are discussed. The present study reports the results of a factor analysis of operational stressors (N = 601 serving British police officers) that revealed three factors: exposure to death and disaster; violence and injury; sexual crime. These were demonstrated to be reliable scales and were included in logistic regression models together with a range of demographic and psychological variables. Models were applied to men and women separately, which showed there to be different predictors of the likelihood of suffering distress (measured by the General Health Questionnaire, GHQ) in terms of the officer's gender and operational role. Overall the model for women officers was better at predicting psychological distress than that for men. These findings are related to aspects of the police occupational culture. Further discussion is offered that conceptualizes police operational stressors as traumatic, routine and vicarious. Finally, some implications are drawn for the provision of stress intervention in the light of this differentiation.     

Dermal Uptake of 18 Dilute Aqueous Chemicals: In Vivo Disappearance‐Method Measures Greatly Exceed In Vitro‐Based Predictions

Average rates of total dermal uptake (K_up) from short‐term (e.g., bathing) contact with dilute aqueous organic chemicals (DAOCs) are typically estimated from steady‐state in vitro diffusion‐cell measures of chemical permeability (K_p) through skin into receptor solution. Widely used (“PCR‐vitro”) methods estimate K_up by applying diffusion theory to increase K_p predictions made by a physico‐chemical regression (PCR) model that was fit to a large set of K_p measures. Here, K_up predictions for 18 DAOCs made by three PCR‐vitro models (EPA, NIOSH, and MH) were compared to previous in vivo measures obtained by methods unlikely to underestimate K_up. A new PCR model fit to all 18 measures is accurate to within approximately threefold (r = 0.91, p < 10^?5), but the PCR‐vitro predictions (r > 0.63) all tend to underestimate the K_up measures by mean factors (UF, and p value for testing UF = 1) of 10 (EPA, p < 10^?6), 11 (NIOSH, p < 10^?8), and 6.2 (MH, p = 0.018). For all three PCR‐vitro models, log(UF) correlates negatively with molecular weight (r² = 0.31 to 0.84, p = 0.017 to < 10^?6) but not with log(vapor pressure) as an additional predictor (p > 0.05), so vapor pressure appears not to explain the significant in vivo/PCR‐vitro discrepancy. Until this discrepancy is explained, careful in vivo measures of K_up should be obtained for more chemicals, the expanded in vivo database should be compared to in vitro‐based predictions, and in vivo data should be considered in assessing aqueous dermal exposure and its uncertainty.     

Systems Resilience for Multihazard Environments: Definition,Metrics, and Valuation for Decision Making

The United Nations Office for Disaster Risk Reduction reported that the 2011 natural disasters, including the earthquake and tsunami that struck Japan, resulted in $366 billion in direct damages and 29,782 fatalities worldwide. Storms and floods accounted for up to 70% of the 302 natural disasters worldwide in 2011, with earthquakes producing the greatest number of fatalities. Average annual losses in the United States amount to about $55 billion. Enhancing community and system resilience could lead to massive savings through risk reduction and expeditious recovery. The rational management of such reduction and recovery is facilitated by an appropriate definition of resilience and associated metrics. In this article, a resilience definition is provided that meets a set of requirements with clear relationships to the metrics of the relevant abstract notions of reliability and risk. Those metrics also meet logically consistent requirements drawn from measure theory, and provide a sound basis for the development of effective decision‐making tools for multihazard environments. Improving the resiliency of a system to meet target levels requires the examination of system enhancement alternatives in economic terms, within a decision‐making framework. Relevant decision analysis methods would typically require the examination of resilience based on its valuation by society at large. The article provides methods for valuation and benefit‐cost analysis based on concepts from risk analysis and management.     

UNIX系统性能监控简述及shell系统资源统计程序

本文简要阐述了unix系统中(主要以IBM的AIX为例)进行系统性能管理的几种命令行工具,并通过编写shell实例程序,运用其中提到的工具实现系统资源利用率的统计程序,为做好unix系统管理和调优提供参考.