价格-数量调节网络交通流演化模型

首次运用经济学非瓦尔拉斯均衡中的价格-数量调节原理和方法,建立网络交通流动态演化模型.假设出行者在路径选择决策时,不但受路径出行时间(价格)的影响,而且还受到路径剩余通行能力(数量)的影响,并将这种路径选择行为形成的稳定交通流模式定义为价格-数量混合调节用户均衡.论文分别建立了价格调节演化模型和数量调节演化模型,进而构建了价格-数量共同调节演化模型,证明了演化模型的稳定状态等价于价格-数量调节用户均衡,且价格调节用户均衡和数量调节用户均衡均为价格-数量调节用户均衡的特例.论文最后以一个简单的测试网络为例对文中建立的演化模型进行了计算分析,结果显示三种演化模型均可较理想地模拟路径流随时间变化的过程,且模型稳定状态分别对应三种用户均衡交通流模式.     

双目标用户均衡下的交通流逐日动态演化模型

时间和费用是出行者在路径选择时关注的两个重要目标，许多研究将两者加权组合为单目标来考虑，存在一定缺陷.在静态交通分配模型的研究中，已有学者提出将两者分开考虑的双目标用户均衡.然而，在动态交通分配模型中，现有研究仍多以传统的单目标用户均衡作为交通流演化的最终状态.因此，本文针对双目标用户均衡，提出了一种新的基于路径流量更新的交通流逐日动态演化模型，假设出行者在每天的路径选择中会将出行时间和收费分开比较以决定是否变换路径.论文从理论上证明了该模型的收敛性，以及交通流演化的最终状态会达到双目标用户均衡，同时数值算例也验证了模型的有效性.     

交通流演化动力学研究的一般框架及性质分析北大核心CSSCI

针对道路网络需求时变的交通流达到均衡的条件以及均衡状态的稳定性问题,运用演化博弈理论和动力系统稳定性理论,提出了流量演化动力学研究的一般框架,建立了多群体多准则出行选择流量演化系统的动力学模型,证明了流量演化动力学模型平衡点与动态交通流量分配模型均衡解之间的等价性,讨论了模型解的存在性、唯一性和稳定性.理论分析结果表明,流量演化动力系统的演化稳定策略等价于动态交通流分配模型的均衡解,流量演化动力系统在某个局部区域总存在着唯一解,并且在出行者个体收益参数满足一定条件的前提下,流量演化动力系统在平衡点附近会表现出不同的稳定性质,通过一个简单路网的数值算例说明了本文建立模型的合理性和有效性.本文在出行者博弈行为和动态交通分配之间建立了联系,有助于加深对于城市交通流演化规律的认识和理解.     

交通流演化动力学研究的一般框架及性质分析

针对道路网络需求时变的交通流达到均衡的条件以及均衡状态的稳定性问题,运用演化博弈理论和动力系统稳定性理论,提出了流量演化动力学研究的一般框架,建立了多群体多准则出行选择流量演化系统的动力学模型,证明了流量演化动力学模型平衡点与动态交通流量分配模型均衡解之间的等价性,讨论了模型解的存在性、唯一性和稳定性． 理论分析结果表明,流量演化动力系统的演化稳定策略等价于动态交通流分配模型的均衡解,流量演化动力系统在某个局部区域总存在着唯一解,并且在出行者个体收益参数满足一定条件的前提下,流量演化动力系统在平衡点附近会表现出不同的稳定性质,通过一个简单路网的数值算例说明了本文建立模型的合理性和有效性． 本文在出行者博弈行为和动态交通分配之间建立了联系,有助于加深对于城市交通流演化规律的认识和理解．     

基于累积前景理论的随机网络用户均衡模型

出行者行为假设对交通网络用户均衡建模具有重要影响,更符合人们的真实决策行为的累积前景理论,为随机交通网络中的路径选择行为研究提供了新的分析框架.基于累积前景理论,将出行者的路径选择决策与网络的随机性相结合,建立了随机网络用户均衡的等价变分不等式模型;提出了求解模型的算法,通过简单的算例对模型和算法的合理性进行验证.通过...     

多维动态用户最优出行选择的变分不等式模型

针对出行行为的出行模式,出发时间/路径选择三个方面,建立了基于路段的理想动态用户最优的变分不等式模型,该模型将用户的出行方案制定和实施作为一个整体进行考虑,表明了在满足动态用户最优选择条件下,交通流在出行模式、出发时间和出行路径上取得一致的动态均衡性,通过必要性和充分性的论证,得到了变分不等式模型和动态用户最优出行模式/出发时间/路径选择均衡条件的等价性,对模型解的存在惟一性成立需要满足的条件作了讨论,提出了求解的嵌套对角化算法,在此基础上,使用一个简单算例对模型进行了验证.     

ATIS环境下交通配流的动态演化模型

考虑交通网络中实现用户均衡态的过程,引入决策出行费用的概念,提出一个 ATIS 环境下的交通配流动态演化模型,模型中的 OD 需求是可变内生的.利用稳定性定理分析了该动态系统的稳定性,说明在一定条件下,系统的用户均衡态是稳定的.采用改进的欧拉法完成了模型的数值试验,结果表明该动态系统确实可以达到用户均衡态,同时也发现,某些模型参数的变化可能导致路径流量和 OD 费用演化轨迹的无规则摆动.     

基于累积前景理论的出发时间选择SDUO模型

以早高峰工作出行为研究对象,基于累积前景理论建立了一个随机动态用户最优(SDUO)交通分配模型,模型可以同时选择出发时间和出行路径,给出了等价的变分不等式,设计了求解算法并通过算例进行了验证。结果显示,路径及OD对之间的动态出发流量、出发时间选择满意函数均与到达工作地点的价值函数形态相似,绝大多数出行者(96.45%)都能在"可以接受的最早到达时刻"与"工作开始时刻"之间到达。模型拓展了传统出发时间选择模型中"时间窗"的概念和出行者完全理性假设的局限,在有限理性框架下考察出行者的决策行为,模型及算法可以为出行行为分析、动态路径诱导,以及拥挤收费和错时上下班等交通管理措施的制订提供理论依据。     

技术的演化与锁定

试用演化经济理论研究与市场用户具有动态回报递增和动态回报递减关系的两类技术的演化问题 .通过建立一个动态随机系统模型 ,论证了这类技术演化的长期均衡对应于某个函数的稳定不动点 ,提出了动态回报递增效应技术演化的多重均衡性和主导技术出现的可能性 ,分析了动态回报递减效应技术演化的不同特征 ,最后给出了一些政策含义     

基于 AＲT 及多风险规避的交通网络均衡模型

随着对交通系统不确定性认识的深入,以绝对理性为基础的“期望效用理论”在风险环境下的路径选择分析中显示出局限性,而“预期后悔理论”则为之提供了新的分析思路． 将预期后悔理论应用到风险环境下的路径选择分析中,将出行者一致风险规避的假设扩展到多风险规避,建立了基于后悔理论及多风险规避出行特征的交通网络随机用户均衡变分不等式模型,并给出了求解算法． 通过算例分析发现,后悔心理对出行者的路径选择并不总是显著的． 在非风险环境及极端风险环境中,后悔心理对出行者的路径选择影响是微弱的,但是当环境处于极端风险与非风险之间时,后悔心理对出行者路径选择有着较为显著的影响．     

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.