Uncertain Benefits Estimates for Reductions in Fine Particle Concentrations

The Environmental Protection Agency's (EPA's) estimates of the benefits of improved air quality, especially from reduced mortality associated with reductions in fine particle concentrations, constitute the largest category of benefits from all federal regulation over the last decade. EPA develops such estimates, however, using an approach little changed since a 2002 report by the National Research Council (NRC), which was critical of EPA's methods and recommended a more comprehensive uncertainty analysis incorporating probability distributions for major sources of uncertainty. Consistent with the NRC's 2002 recommendations, we explore alternative assumptions and probability distributions for the major variables used to calculate the value of mortality benefits. For metropolitan Philadelphia, we show that uncertainty in air quality improvements and in baseline mortality have only modest effects on the distribution of estimated benefits. We analyze the effects of alternative assumptions regarding the value of reducing mortality risk, whether the toxicity is above or below the average for fine particles, and whether there is a threshold in the concentration‐response relationship, and show these assumptions all have large effects on the distribution of benefits.     

Uncertainty Analysis Based on Probability Bounds (P-Box) Approach in Probabilistic Safety Assessment

A wide range of uncertainties will be introduced inevitably during the process of performing a safety assessment of engineering systems. The impact of all these uncertainties must be addressed if the analysis is to serve as a tool in the decision-making process. Uncertainties present in the components (input parameters of model or basic events) of model output are propagated to quantify its impact in the final results. There are several methods available in the literature, namely, method of moments, discrete probability analysis, Monte Carlo simulation, fuzzy arithmetic, and Dempster-Shafer theory. All the methods are different in terms of characterizing at the component level and also in propagating to the system level. All these methods have different desirable and undesirable features, making them more or less useful in different situations. In the probabilistic framework, which is most widely used, probability distribution is used to characterize uncertainty. However, in situations in which one cannot specify (1) parameter values for input distributions, (2) precise probability distributions (shape), and (3) dependencies between input parameters, these methods have limitations and are found to be not effective. In order to address some of these limitations, the article presents uncertainty analysis in the context of level-1 probabilistic safety assessment (PSA) based on a probability bounds (PB) approach. PB analysis combines probability theory and interval arithmetic to produce probability boxes (p-boxes), structures that allow the comprehensive propagation through calculation in a rigorous way. A practical case study is also carried out with the developed code based on the PB approach and compared with the two-phase Monte Carlo simulation results.     

基于鲁棒优化模型的项目调度策略遗传算法

针对任务工期不确定的资源受限项目调度问题,提出了求解该问题的鲁棒优化数学模型。在随机规划基础上,针对该鲁棒优化模型设计了遗传算法。算法通过多种任务优先规则生成初始种群以保证种群多样性。应用该遗传算法对项目实例进行了求解,分析表明所求得的项目调度策略能够有效应对任务工期不确定性导致的随机差异,具有较强的鲁棒性。参数分析表明决策者可以通过调节模型权重系数有效平衡解的可行性与最优性,有助于决策者根据风险偏好进行选择。     

基于实物期权的新技术投资决策实证研究

本文基于对我国高新技术企业的实际调研,从实物期权视角检验不同类型不确定性对企业新技术投资决策的影响。研究结果表明,市场与政策不确定性对投资的延迟作用与技术不确定性对投资的促进作用得到不同程度验证,而竞争强度与投资不可逆程度对不确定性与投资关系的调节作用则不完全符合实物期权的理论预期。论文结果揭示了我国高新技术企业进行投资决策的一般规律,可为企业应用实物期权方法提供参考。     

新兴产业政策决策过程中的不确定性管理研究——基于物联网产业的宏观政策决策过程的案例

采用纵贯研究、内容分析、深度访谈相结合的定性研究方法,以推动我国物联网产业发展的3个宏观政策决策过程为研究对象,旨在讨论政企互动是如何帮助政府进行不确定性管理的.研究结论表明:新兴产业的宏观政策决策是由数个存在递进关系的渐进式阶段组成,而每个渐进式事项的解决依赖于众多在政企互动中形成的微观政策工具的实施.政企互动帮助政策决策者通过4种机制(信息获取、行动协调、企业行动承诺和政府政策承诺)实现了对因信息缺乏以及对产业行动者资源依赖所造成的不确定性的管理.     

需求不确定和纵向约束的链与链竞争固定加价

基于需求不确定和纵向约束的链与链竞争环境,识别固定加价合同选择的绩效改进条件和博弈均衡特征,并进一步分析市场需求波动风险、市场规模、市场份额、价格竞争、零售商预测能力及固定加价比例对合同选择行为的影响。研究发现：当横向价格竞争相对较弱,零售终端的市场份额相对较大时,基于纵向约束的固定加价合同是实现供应链系统绩效改进的贝叶斯占优均衡;若此时固定加价的比例相对适中且市场需求波动风险不是很高,或者固定加价的比例较大但市场需求波动的风险相对适中,则固定加价合同是实现制造商和零售商Pareto绩效均改进的贝叶斯均衡;而若价格竞争非常激烈,则无纵向约束的批发价格合同能形成实现供应链系统绩效Pareto改进的占优贝叶斯均衡。     

Building a Human Health Risk Assessment Ontology (RsO): A Proposed Framework

Over the last decade the health and environmental research communities have made significant progress in collecting and improving access to genomic, toxicology, exposure, health, and disease data useful to health risk assessment. One of the barriers to applying these growing volumes of information in fields such as risk assessment is the lack of informatics tools to organize, curate, and evaluate thousands of journal publications and hundreds of databases to provide new insights on relationships among exposure, hazard, and disease burden. Many fields are developing ontologies as a way of organizing and analyzing large amounts of complex information from multiple scientific disciplines. Ontologies include a vocabulary of terms and concepts with defined logical relationships to each other. Building from the recently published exposure ontology and other relevant health and environmental ontologies, this article proposes an ontology for health risk assessment (RsO) that provides a structural framework for organizing risk assessment information and methods. The RsO is anchored by eight major concepts that were either identified by exploratory curations of the risk literature or the exposure‐ontology working group as key for describing the risk assessment domain. These concepts are: (1) stressor, (2) receptor, (3) outcome, (4) exposure event, (5) dose‐response approach, (6) dose‐response metric, (7) uncertainty, and (8) measure of risk. We illustrate the utility of these concepts for the RsO with example curations of published risk assessments for ionizing radiation, arsenic in drinking water, and persistent pollutants in salmon.     

基于非参多元Expectile模型的原油价格风险测度研究—宏观不确定性视角

当下政治经济环境存在诸多不确定性,原油价格随着不确定性的增加而大幅波动,因此在当前不确定性环境中建立一个有效的风险预测模型具有重要的实际意义。本文基于非参多元Expectile模型,选取2010年1月5日至2020年1月6日的美国西德克萨斯原油价格的日度数据,构建同时包含地缘政治风险、经济政策不确定性等六个宏观不确定性变量的原油价格风险预测模型。此外,引入APARCH模型和基于蒙特卡罗方法的GARCH模型,比较以上三个模型预测能力。最后,基于预测的VaR值计算调整的Sharpe比率。结论表明,整体上,非参多元Expectile模型能较好处理多个宏观变量包含的信息,具有更高的预测能力。在不确定性事件叠加发生的时期预测表现依然优于其他模型,减少了不确定性增加导致原油市场波动幅度增加带来的风险,具有更强的稳定性。因此,在经济转型的关键时期,本研究可为政策制定者和监管当局面临不确定性上升环境下建立有效的原油价格风险预测模型提供参考,制定应对政策防范化解风险,同时也为投资者在当前复杂的国际形势下提供预测参考,尽量规避损失同时获取收益。     

采购赋能情境下平台供应链的库存风险共担策略研究

近年来,平台供应链中核心企业的采购赋能行为迅速增加,这有助于帮助供应链成员降本增效,但也可能引发核心企业自身的高库存风险。本文在同时考虑供应商产出不确定和零售商需求不确定的情境下,构建了由一个平台型电商企业、一个供应商和多个零售商组成的三级供应链系统,探讨了采购赋能情境下供应链的库存风险共担机制。研究发现,引入需求风险共担契约有助于提升供应商的生产投入水平、平台的订购量以及零售商的销售努力,并提高供应商与平台的利润。其次,引入产出风险共担契约会降低供应链成员的决策水平和利润。最后,对于不同类型的供应链风险应采取差异化的应对策略。     

Flexible Backup Supply and the Management of Lead‐Time Uncertainty

We consider replenishment decisions for a constant rate demand environment from a supplier with uncertain lead times. We study the potential use of a flexible backup supplier as an emergency response to accurate lead‐time information arriving at (or close after) the beginning of the demand interval and well after an original order with the stochastic lead‐time supplier has been placed. The emergency response decisions involve whether to order and how much from the flexible backup supplier, with the objective of minimizing the cost of meeting demand. We derive the optimal emergency‐response policy and clearly outline its implications on the optimized safety lead time of the original order placement and on the cost of meeting demand. We examine the impact on the use of the flexible backup supplier of factors like the arrival time of accurate lead‐time information and the response lead time of the backup supplier. We further study the potential benefits of the use of the flexible backup supplier in a dual role: as one of the two suppliers in a redundant supply system assigned to originally meet the demand and as an emergency response to later‐arriving lead‐time information. Our numerical studies illustrate the benefits from the use of the flexible backup supplier as an emergency response, but for reasonable purchase premiums and short lead times of flexible backup supply options, their use in a dual (regular and emergency response) role often leads to improved performance over safety lead‐time single and uncertain lead‐time supplier‐replenishment strategies. The benefits of the backup supply options are accentuated the higher the lead‐time uncertainty of the stochastic lead‐time supplier is.