受内压圆柱筒体开孔-接管区应力集中的有限元分析

利用 ANSYS有限元分析软件通过三个算例对圆柱形筒体小开孔直接管区、大开孔直接管区、大开孔斜接管区的应力分布状况进行了研究 .从中了解到了最大第一主应力的变化规律 ,得出在弹性范围内的应力集中系数 ,并且得到ASME规范中的算式较好的验证     

Sampling Strategies for Toxic Air Contaminants

Annual concentrations of toxic air contaminants are of primary concern from the perspective of chronic human exposure assessment and risk analysis. Despite recent advances in air quality monitoring technology, resource and technical constraints often impose limitations on the availability of a sufficient number of ambient concentration measurements for performing environmental risk analysis. Therefore, sample size limitations, representativeness of data, and uncertainties in the estimated annual mean concentration must be examined before performing quantitative risk analysis. In this paper, we discuss several factors that need to be considered in designing field-sampling programs for toxic air contaminants and in verifying compliance with environmental regulations. Specifically, we examine the behavior of SO2, TSP, and CO data as surrogates for toxic air contaminants and as examples of point source, area source, and line source-dominated pollutants, respectively, from the standpoint of sampling design. We demonstrate the use of bootstrap resampling method and normal theory in estimating the annual mean concentration and its 95% confidence bounds from limited sampling data, and illustrate the application of operating characteristic (OC) curves to determine optimum sample size and other sampling strategies. We also outline a statistical procedure, based on a one-sided t-test, that utilizes the sampled concentration data for evaluating whether a sampling site is compliance with relevant ambient guideline concentrations for toxic air contaminants.     

Assessing Risk‐Based Upper Limits of Melamine Migration from Food Containers

Melamine contamination of food has become a major food safety issue because of incidents of infant disease caused by exposure to this chemical. This study was aimed at establishing a safety limit in Taiwan for the degree of melamine migration from food containers. Health risk assessment was performed for three exposure groups (preschool children, individuals who dine out, and elderly residents of nursing homes). Selected values of tolerable daily intake (TDI) for melamine were used to calculate the reference migration concentration limit (RMCL) or reference specific migration limit (RSML) for melamine food containers. The only existing values of these limits for international standards today are 1.2 mg/L (0.2 mg/dm²) in China and 30 mg/L (5 mg/dm²) in the European Union. The factors used in the calculations included the specific surface area of food containers, daily food consumption rate, body weight, TDI, and the percentile of the population protected at a given migration concentration limit (MCL). The results indicate that children are indeed at higher risk of melamine exposure at toxic levels than are other groups and that the 95th percentile of MCL (specific surface area = 5) for children aged 1–6 years should be the RMCL (0.07 mg/dm²) for protecting the sensitive and general population.     

The myth of price convergence under economic integration: A proposed explanation for the difference in food prices across European countries

Conventional globalization theory states that regional economic integration will precede price standardization across participating countries due to the increased buying power of large retail groups and parallel imports. The resulting price corridor should merely reflect differences in logistic costs and short-term, local competitive actions. Yet, this study uses panel data from 25 European countries to examine how hefty food and beverage price differentials between regions remained constant over the last decade. Income, store productivity, and market concentration all contribute to the explanation for regional price differences. These findings suggest that, contrary to straight-line globalization theory, large European retailers’ decisions can influence price convergence and maintain important price dispersion between economically integrated countries. We provide recommendations to enhance market integration.     

Shall we follow the money? Anti-mafia policies and electoral competition

Building upon the evidence that the mafia increases the degree of vote concentration, we use data on regional elections in Sicily to estimate the impact of anti-mafia policies on electoral competition. We find robust evidence that the reassignment for social purposes of property and assets seized to the mafia reduces the degree of electoral concentration. This result supports the hypothesis that policies that create social value, such as the reallocation to social-driven organizations, are more effective than those targeted to public and political institutions.     

Pollutant Ground Concentrations of Nonneutrally Buoyant Particles

A methodology is suggested for the estimation of the mass density and the cumulative ground deposition of a nonvolatile, nonneutrally buoyant, air pollutant (liquid or solid) released from a polluted column (following an explosion caused during routine operation in, e.g., the chemical industry or due to any kind of hostile act) and deposited on the ground via gravitational settling. In many cases, the deposited mass due to gravitational settling constitutes a significant fraction of the original inventory released from the source. Implementation of the methodology in preliminary risk assessments can serve as an efficient tool for emergency planning for both immediate and long‐term measures such as evacuation and decontamination. The methodology considers, inter alia, an estimation of the critical particle diameter, particle size, and mass distributions along the polluted column. This methodology was developed to apply in rural regions since proper application of relevant meteorological input data can be accomplished mainly for such areas.     

Identifying radon-prone building typologies by marginal modelling

Radon is a naturally occurring decay product of uranium known to be the main contributor to natural background radiation exposure. It has been established that the health risk related to radon exposure is lung cancer. In fact, radon is considered to be a major leading cause of lung cancer, second only to smoking. In this paper, we identified building typologies that affect the probability of detecting indoor radon concentration above reference values, using the data collected within two monitoring campaigns recently conducted in Northern Italy. This information is fundamental both in prevention, i.e. when the construction of a new building is planned and in mitigation, i.e. when a high concentration detected inside buildings has to be reduced. A spatial regression approach for binary data was adopted for this goal where some relevant covariates on the soil were retrieved by linking external spatial databases.     

论竞争法上当事人的确定

竞争法案件中,当事人的确定不仅关系到明确权利、义务、责任的承担者,而且是评价市场力量的重要前提,只有在确定了当事人以后,才能进行市场力量的计算,从而评价各种限制竞争行为的后果,判明其违法性。而如何在具体竞争案件中确定当事人,是一个十分复杂的问题。本文针对竞争法的主要领域,即限制竞争协议、支配地位滥用行为以及企业合并情形下当事人的确定规则,进行深入分析,而尤以企业合并情形为重点。在英文中,各种竞争案件的当事人往往称作“undertakingsconcerned”,我们在此将其称作“所涉企业”。     

超大型平台并购初创企业的反垄断法规制研究

超大型平台并购初创企业可能具有反竞争效应,然而在芝加哥学派“假阳性错误”成本大于“假阴性错误”成本的理论观点以及反垄断监管困境的双重影响下,反垄断执法机构对其长期采取宽容的态度。但是芝加哥学派的错误成本理论在应用于超大型平台并购初创企业时存在局限性。频繁实施的初创企业并购非但不会导致超大型平台走向自毁,反将进一步巩固其市场支配地位、抬高市场进入壁垒。即便市场经历漫长期间之后最终完成了自我纠正,规制不足所造成的“假阴性错误”成本也会十分高昂,平台经济领域公平竞争、行业创新发展和消费者权益保护均会受到长期不利影响。因此,在秉持“包容审慎监管”原则的前提下适度加大监管力度,应当成为对超大型平台并购初创企业进行反垄断法规制的基本取向。基于这一取向,未来对超大型平台并购初创企业的反垄断法规制思路需要进行以下调整：以初创企业市值、用户规模、流量规模等补正并购的既有申报标准;确立契合平台经济特点的竞争损害分析框架;针对超大型平台并购初创企业的不同效应建立宽严相济的法律制度;赋予反垄断执法机构更加广泛的证据收集权,强化参与并购经营者的证明责任,并通过结合这二者的方式来化解反垄断执法机构获取监管信息上的...     

Risk and diversification of nonprofit revenue portfolios: Applying modern portfolio theory to nonprofit revenue management

This study uses modern portfolio theory (MPT) to estimate the risk of nonprofit revenue portfolios and examines to what degree the revenue concentration measure based on Herfindahl–Hirschman Index is associated with the portfolio risk measure based on MPT. The findings suggest that nonprofits with greater revenue concentration have lower revenue portfolio risk in the whole sample analysis. However, it is plausible that this result is dominated by organizations reliant on commercial income, which comprise over half of the sample. In fact, when examined separately, the relationship varies by an organization's primary funding structure. While higher revenue concentration is positively associated with portfolio risk for organizations relying on donations or those without a consistent primary funding source, it appears to associate with a lower portfolio risk for commercial organizations and those relying on government grants. This study reflects on the concept of diversification derived from portfolio theory and calls attention to a more nuanced approach to nonprofit revenue strategy.