The cost of selfishness for maximizing the minimum load on uniformly related machines

Consider the following scheduling game. A set of jobs, each controlled by a selfish agent, are to be assigned to m uniformly related machines. The cost of a job is defined as the total load of the machine that its job is assigned to. A job is interested in minimizing its cost, while the social objective is maximizing the minimum load (the value of the cover) over the machines. This goal is different from the regular makespan minimization goal, which was extensively studied in a game theoretic context. We study the price of anarchy (poa) and the price of stability (pos) for uniformly related machines. The results are expressed in terms of s, which is the maximum speed ratio between any two machines. For uniformly related machines, we prove that the pos is unbounded for s>2, and the poa is unbounded for s≥2. For the remaining cases we show that while the poa grows to infinity as s tends to 2, the pos is at most 2 for any s≤2.     

The social and policy predictors of driving mobility among older adults

This research was designed to identify the impact of state driver's license renewal requirements on the driving mobility (i.e., the reduction or cessation of driving) of older (70 years or older) drivers in the United States. Nationally representative data from four waves (1993-2000) of the Asset and Health Dynamics of the Oldest Old study were linked to state policies on relicensing and used in a longitudinal logistic regression analysis. The author assessed the driving behaviors of a sample of 9,638 men and women. The findings demonstrate that the driving mobility of older people is influenced by state relicensing policies. The analysis indicates that five policies--accelerated renewal, mental testing, peripheral vision testing, renewal in person at age 70+ (as opposed to renewal by mail or online), and restricted licensing--have a significant effect on an older driver's decision to reduce or cease driving. The driving patterns of older adults are influenced not only by their health and socioeconomic backgrounds, but also by state relicensing policies. In terms of public policy, this result shows that there is a mechanism for extending the years of independent mobility for older people: restricted licensing.     

Wholesale Pricing under Mild and Privately Known Concerns for Fairness

This article studies the performance of wholesale pricing when the supply chain partners' fairness concerns are private information. We find that some properties of wholesale pricing established under complete information hold under incomplete information as well. First, wholesale pricing can coordinate the supply chain, despite the information asymmetry, when fairness concerns are strong enough. Second, in the case when an equitable profit split does not imply that the retailers profit must be higher than that of the supplier, the suppliers' equilibrium offer is never rejected. Overall, the study makes two primary contributions. First, it provides a partial characterization of the equilibrium when the conditions required for coordination do not hold, that is, when fairness concerns are mild. In this case, the model predicts that the expected market price must be exactly the same as under complete information. The channel efficiency, nevertheless, is strictly lower than under complete information. The distribution‐free lower bound on channel efficiency suggests that this efficiency loss should be quite small, though. Second, it provides an experimental test of the models' predictions as well as a direct validation of the assumptions of preferences heterogeneity and mildness by obtaining the empirical distribution of the preferences.     

Comparison as Incentive: Newsvendor Decisions in a Social Context

Explicit formal mechanisms dominate the discussion about incentives in Operations Management, yet many other mechanisms exist. Social comparison between peers may provide strong implicit incentives for individuals. Social comparison arises naturally in all social settings and may thus be unintended; however, many companies deliberately use it to motivate employees. In this study, we model a social context in which purchasers evaluate their performance relative to their peers; a feeling of inferiority results in a negative contribution to utility, whereas a feeling of superiority results in a positive contribution. We find that social comparison induces characteristic deviations from the newsvendor optimum ordering decision: if fear of inferiority outweighs anticipation of superiority, then purchasers herd together; the converse scenario incites actors to polarize away from each other. In both cases, actors will deviate from ordering the newsvendor optimum in order to satisfy social goals. Demand correlation and profit margins moderate the extent of the deviation.     

From Ideal to Real Risk: Philosophy of Causation Meets Risk Analysis

A question has been raised in recent years as to whether the risk field, including analysis, assessment, and management, ought to be considered a discipline on its own. As suggested by Terje Aven, unification of the risk field would require a common understanding of basic concepts, such as risk and probability; hence, more discussion is needed of what he calls “foundational issues.” In this article, we show that causation is a foundational issue of risk, and that a proper understanding of it is crucial. We propose that some old ideas about the nature of causation must be abandoned in order to overcome certain persisting challenges facing risk experts over the last decade. In particular, we discuss the challenge of including causally relevant knowledge from the local context when studying risk. Although it is uncontroversial that the receptor plays an important role for risk evaluations, we show how the implementation of receptor‐based frameworks is hindered by methodological shortcomings that can be traced back to Humean orthodoxies about causation. We argue that the first step toward the development of frameworks better suited to make realistic risk predictions is to reconceptualize causation, by examining a philosophical alternative to the Humean understanding. In this article, we show how our preferred account, causal dispositionalism, offers a different perspective in how risk is evaluated and understood.     

Levels of uric acid in erectile dysfunction of different aetiology

Erectile dysfunction is a common disease characterized by endothelial dysfunction. The aetiology of ED is often multifactorial but evidence is being accumulated in favor of the proper function of the vascular endothelium that is essential to achieving and maintaining penile erection. Uric acid itself causes endothelial dysfunction via decreased nitric oxide production. This study aims to evaluate the serum uric acid (SUA) levels in 180 ED patients, diagnosed with the International Index of Erectile Function-5 (IIEF-5) and 30 non-ED control. Serum uric acid was analyzed with a commercially available kit using ModularEVO (Roche, Monza, Italy). Within-assay and between-assay variations were 3.0% and 6.0%, respectively. Out of the ED patients, 85 were classified as arteriogenic (A-ED) and 95 as non-arteriogenic (NA-ED) with penile-echo-color-Doppler. Uric acid levels (median and range in mg/dL) in A-ED patients (5.8, 4.3–7.5) were significantly higher (p?p?相似文献   

放弃是为了更好地开始

Serena，居上海，曾供职于世界500强，经常出现于猎头寻访名单之上。某一日，突做决定，辞职，旅行，再求职，只为了一个虚无缥缈的词“意义”。应本刊之遨，她以文字实时记录这趟重新寻找职业意义之旅。     

Socioeconomic Inequalities and Self-Rated Health: A Multilevel Study of Italian Elderly

We adopted a multilevel approach in order to provide a comprehensive overview of the main social and economic differences associated with inequalities in self-rated health, according to the territorial context of residence. We focused on the Italian population aged 65 and over, availing of the most recent data on health conditions in Italy. This study proves the persistence in Italy, a modern welfare state that has one of the best overall healthcare systems in the world, of significant, if not enormous, socioeconomic differences in self-perceived health among the elderly. We found that each component of the socioeconomic status is autonomously correlated with individual perceptions of health, highlighting the importance of considering all of the facets of the individual socioeconomic status in measuring the extent of health inequalities. The lack of a network of relationships was also found to be strongly associated with a poor health status for elderly Italians. Our study also documented the presence of a contextual effect. The proposed multilevel modeling proved to be useful in shedding light on relevant aspects in the field of perceived health and for avoiding misleading results.