Estimation of Balanced Simultaneous Confidence Sets for SIR Models

Stochastic compartmental (e.g., SIR) models have proven useful for studying the epidemics of childhood diseases while taking into account the variability of the epidemic dynamics. Here, we present a method for estimating balanced simultaneous confidence sets for the mean sample path of a stochastic SIR model, thus providing a simple representation of both the typical behavior and the variability of the epidemic. The confidence sets are estimated by a bootstrap procedure, using asymptotic properties of density dependent jump Markov processes. The method is applied to chickenpox epidemics in France and the coverage probability of the confidence sets is estimated in that context.     

Bayesian Variable Selection in Markov Mixture Models

Monte Carlo simulation is used to evaluate the actual confidence levels of five different approximations for confidence intervals for the probability of success in Markov dependent trials. The approximations involve the conditional probability of success as a nuisance parameter, and the effects of substituting Klotz's (1973), Price's (1976), and a new estimator are also evaluated. The new estimator is less biased and tends to increase the confidence level. A program for calculating the estimator and the confidence interval approximations is available.     

Bayesian Capture-Recapture Analysis: An Application in Modeling Semelparity of a Neotropical Didelphid Marsupial

We develop a series of Bayesian statistical models for estimating survival of a neotropic didelphid marsupial, the Brazilian gracile mouse opossum (Gracilinanus microtarsus). These models are based on the Cormack–Jolly–Seber model (Cormack, 1964 Cormack , R. M. ( 1964 ). Estimates of survival from the sighting of marked animals . Biometrika 51 : 429 – 438 .[Crossref], [Web of Science ®] , [Google Scholar]; Jolly 1965 Jolly , G. M. ( 1965 ). Explicit estimates from capture-recapture data with both death and immigration stochastic model . Biometrika 52 : 225 – 247 .[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]; Seber 1965 Seber , G. A. F. ( 1965 ). A note on the multiple recapture census . Biometrika 52 : 249 – 259 .[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]) with both survival and recapture rates expressed as a function of covariates using a logit link. The proposed models allow taking into account heterogeneity in capture probability caused by the existence of different groups of individuals in the population. The models were applied to two cohorts (Cohort, 2000, 2001) with the first one including 14 and the second one 15 sampling occasions. The best models for each of the cohorts indicate that G. microtarsus is best described as partially semelparous, a condition in which mortality after the first mating is high but graded over time, with a fraction of males surviving for a second breeding season (Boonstra, 2005 Boonstra , R. ( 2005 ). Equipped for life: the adaptive role of the stress axis in male mammals . Journal of Mammalogy 86 : 236 – 247 .[Crossref], [Web of Science ®] , [Google Scholar]).     

Inverse Gaussian Distribution for Modeling Conditional Durations in Finance

The durations between market activities such as trades and quotes provide useful information on the underlying assets while analyzing financial time series. In this article, we propose a stochastic conditional duration model based on the inverse Gaussian distribution. The non-monotonic nature of the failure rate of the inverse Gaussian distribution makes it suitable for modeling the durations in financial time series. The parameters of the proposed model are estimated by an efficient importance sampling method. A simulation experiment is conducted to check the performance of the estimators. These estimates are used to compute estimated hazard functions and to compare with the empirical hazard functions. Finally, a real data analysis is provided to illustrate the practical utility of the models.     

A NOTE ON MODELING PROJECT INTERDEPENDENCE IN RESEARCH AND DEVELOPMENT*

This note is concerned with the problem of resource allocation under uncertainty in a research and development laboratory. A distinction is defined between project interrelationships that are specific (or internal) to certain projects and interrelationships resulting from external environmental factors. Formulations are introduced that allow both types of interrelationships to be formally included in a resource allocation optimization model. In the case of external environmental factors, an example is presented and analyzed.     

集群企业创新绩效生成的结构-行为路径研究

从中国背景下集群企业的规模、内外部连接关系等结构因素,以及集群企业探索式、利用式学习行为角度,研究集群企业创新绩效的结构和行为来源。将集群中的企业分为领导型和跟随型,研究这2类企业建立的集群内外部连接关系,以及集群企业的探索式、利用式学习行为对创新绩效的影响,揭示集群企业的不同连接关系与学习行为在生成创新绩效过程中的功能和作用。以南京市六合化工产业集群的236家企业为样本,运用结构方程模型进行了分类检验和比较。研究发现,集群企业的内外部连接关系是探索式、利用式学习行为的结构基础,并通过探索式、利用式学习行为影响其创新绩效;领导型企业通过双重学习提升创新绩效,跟随型企业则侧重于利用式学习来提升增量创新绩效;2类企业创新绩效生成的路径存在差异,集群整体创新绩效的提升依赖于二者对结构、学习行为和创新的协同作用。     

Static-dynamic uncertainty strategy for a single-item stochastic inventory control problem

We consider a single-stage inventory system facing non-stationary stochastic demand of the customers in a finite planning horizon. Motivated by the practice, the replenishment times need to be determined and frozen once and for all at the beginning of the horizon while decisions on the exact replenishment quantities can be deferred until the replenishment time. This operating scheme is refereed to as a “static-dynamic uncertainty” strategy in the literature [3]. We consider dynamic fixed-ordering and linear end-of-period holding costs, as well as dynamic penalty costs, or service levels. We prove that the optimal ordering policy is a base stock policy for both penalty cost and service level constrained models. Since an exponential exhaustive search based on dynamic programming yields the optimal ordering periods and the associated base stock levels, it is not possible to compute the optimal policy parameters for longer planning horizons. Thus, we develop two heuristics. Numerical experiments show that both heuristics perform well in terms of solution quality and scale-up efficiently; hence, any practically relevant large instance can be solved in reasonable time. Finally, we discuss how our results and heuristics can be extended to handle capacity limitations and minimum order quantity considerations.     

基于决策分析的社交网络链路预测方法

社交网络是社会媒体信息传播的骨架,对其进行链路预测的研究将有助于社会媒体平台上的信息管理和舆论控制.在既有网络链路预测方法研究的基础上,以决策分析的思想为出发点,提出了引入效用函数分析的社交网络链路预测方法;针对效用函数中参数的估计问题,进一步提出了允许一定误差度的马尔科夫链蒙特卡洛参数校准方法,并对方法的正确性进行理论上的论证.在收集到的5个腾讯QQ群的数据集上,进行了新方法的验证研究,并与既有的链路预测方法在准确性方面进行了比较分析.研究表明:本文提出的预测方法考虑了链路形成的微观行为基础,具有较好的预测准确性,并且参数估计算法中"允许误差"的引入有助于模型应用者在模型效率和准确性方面的折衷中做出合理的决策.     

参数法下中国商业银行成本X效率实证研究

X效率是关于整合技术、人力资源及其他资产来生产给定产出的管理水平的测度。研究文献表明,X效率是影响商业银行经营效率和竞争力的主要因素。我们选用参数法中的SFA法,构建超越对数成本函数,研究构成我国商业银行业主体的14家商业银行1997-2005年成本效率情况,并在此基础上,对相关的效率影响因素进行分析。实证结果表明,我国商业银行成本X效率总体呈上升趋势,国有银行经过改革后成本X效率显著提高,股份制银行总体上成本X效率高于国有银行,但梯队现象明显,少数股份制银行X效率严重低于行业平均水平。