Bounds to Memory Loss

If we express our knowledge in sentences, we will find that these sentences are linked in complex patterns governed by our observations and our inferences from these observations. These inferences are to a large extent driven by logical rules. We ask whether the structure logic imposes on our knowledge restricts what we forget and what we remember. The model is a two period S5 logic. In this logic, we propose a memory loss operator: the agent forgets a sentence pif and only if he knows pat time 1 and he does not know pat time 2. Equipped with the operator, we prove theorems on the relation between knowledge and memory loss. The main results point to classes of formulas that an agent cannot forget, and classes of formulas he must forget. A desirable feature is that most results hold in the S4 logic. The results illustrate bounds to memory loss, and thus to bounded rationality. We apply the model to single-agent conventions: conventions made between an agent and himself.     

A critical look at Lo's modified R/S statistic

We report on an empirical investigation of the modified rescaled adjusted range or R/S statistic that was proposed by Lo, 1991. Econometrica 59, 1279–1313, as a test for long-range dependence with good robustness properties under ‘extra’ short-range dependence. In contrast to the classical R/S statistic that uses the standard deviation S to normalize the rescaled range R, Lo's modified R/S-statistic V_q is normalized by a modified standard deviation S_q which takes into account the covariances of the first q lags, so as to discount the influence of the short-range dependence structure that might be present in the data. Depending on the value of the resulting test-statistic V_q, the null hypothesis of no long-range dependence is either rejected or accepted. By performing Monte-Carlo simulations with ‘truly’ long-range- and short-range dependent time series, we study the behavior of V_q, as a function of q, and uncover a number of serious drawbacks to using Lo's method in practice. For example, we show that as the truncation lag q increases, the test statistic V_q has a strong bias toward accepting the null hypothesis (i.e., no long-range dependence), even in ideal situations of ‘purely’ long-range dependent data.     

美国中期选举及“茶党”兴起的影响

美国中期选举使民主党和奥巴马总统本人受到很大打击。民主党失掉众议院多数席位,奥巴马未来两年执政道路充满荆棘,竞选连任困难重重。共和党通过中期选举掌控了众议院,标志着他们说便宜话的时代结束了,未来的道路也并不好走。茶党的兴起,对美国政坛和社会的影响正在显现。美国保守主义思潮回归,金融经济危机冲击下的各种社会问题交织,其国内外政策走向正在深刻演变之中。     

试论美国法之社会立法的平等权审查标准

传统上美国法院对于社会立法内容违反平等权的问题都采取审慎的态度,一般尊重立法者的判断,避免做实质性介入。但随着社会民众福利权意识的不断提高,美国法院逐步强化了社会立法内容的合理性审查标准,检验立法目的与手段之间的合理关联性,强调差别待遇的坚实理由,限制立法的自由裁量,从而实现社会立法的平等保护。     

INSIGHTS ON SERVICE SYSTEM DESIGN FROM A NORMAL APPROXIMATION TO ERLANG'S DELAY FORMULA

We show how a simple normal approximation to Erlang's delay formula can be used to analyze capacity and staffing problems in service systems that can be modeled as M/M/s queues. The numbers of servers, s, needed in an M/M/s queueing system to assure a probability of delay of, at most, p can be well approximated by s ≅ p + z_***I-p+, where z_1-p, is the (1 - p)th percentile of the standard normal distribution and ρ, the presented load on the system, is the ratio of Λ, the customer arrival rate, to μ, the service rate. We examine the accuracy of this approximation over a set of parameters typical of service operations ranging from police patrol, through telemarketing to automatic teller machines, and we demonstrate that it tends to slightly underestimate the number of servers actually needed to hit the delay probability target—adding one server to the number suggested by the above formula typically gives the exact result. More importantly, the structure of the approximation promotes operational insight by explicitly linking the number of servers with server utilization and the customer service level. Using a scenario based on an actual teleservicing operation, we show how operations managers and designers can quickly obtain insights about the trade-offs between system size, system utilization and customer service. We argue that this little used approach deserves a prominent role in the operations analyst's and operations manager's toolbags.     

Still Partners After All These Years: Ulrich's and ISSN

Since 2000, an Ulrich's Periodicals Directory (Ulrich's) employee has been located in the Library of Congress's U.S. ISSN Center at the Library of Congress to assign ISSN and create records for both Ulrich's and the international ISSN Register/CONSER database. How this arrangement came about, how it has succeeded over the past ten years, and the broad potential for this partnership becoming a model in both organizations for future automated data sharing and data linking is the subject of this article.     

A note on Läuter-type robust design for polynomial regression models

In this paper, we consider the problem of model robust design for simultaneous parameter estimation among a class of polynomial regression models with degree up to k. A generalized D-optimality criterion, the Ψ_α‐optimality criterion, first introduced by Läuter (1974) is considered for this problem. By applying the theory of canonical moments and the technique of maximin principle, we derive a model robust optimal design in the sense of having highest minimum Ψ_α‐efficiency. Numerical comparison indicates that the proposed design has remarkable performance for parameter estimation in all of the considered rival models.     

A test statistic for weighted runs

A new test statistic based on runs of weighted deviations is introduced. Its use for observations sampled from independent normal distributions is worked out in detail. It supplements the classic χ² test which ignores the ordering of observations and provides additional sensitivity to local deviations from expectations. The exact distribution of the statistic in the non-parametric case is derived and an algorithm to compute p-values is presented. The computational complexity of the algorithm is derived employing a novel identity for integer partitions.     

Diversity in Pathways to Parenthood: Patterns,Implications, and Emerging Research Directions

This review examines and synthesizes recent research on pathways to parenthood. We begin by providing basic information about patterns, differentials, and trends and discussing adoption and new reproductive technologies. We next turn to several areas of inquiry that became particularly prominent in the last decade: the continued “decoupling” of marriage and childbearing, the parental relationship context of nonmarital childbearing, family structure stability, multiplepartner fertility, and racial and ethnic variation in childbearing patterns. We then consider the implications of this body of scholarship and identify avenues for future research. Throughout, we highlight racial/ethnic and social class variation in childbearing patterns.     

海合会国家与美国的安全合作

美国插手海湾事务,客观上使海湾各种力量重新趋于平衡。美国主导海湾防务,必然会按照美国意志行事,以使海合会国家的安全利益服从于美国全球战略利益,这与海合会国家寻求美国庇护的初衷产生了矛盾。随着时间的推移,这种矛盾越发凸显,海合会国家的不安全感也越发强烈。虽然这些问题目前不会阻碍双方安全合作的进程,但会影响双方全面合作的深度。