On Properties of Percentile Bootstrap Confidence Intervals for Period Using Periodogram

Periodic functions have many applications in astronomy. They can be used to model the magnitude of light intensity of the period variable stars that their brightness vary with time. Because the data related to the astronomical applications are commonly observed at the time points that are not regularly spaced, the use of the periodogram as a good tool for estimating period is highlighted. Our bootstrap inference about period is based on maximizing the periodogram and consists of percentile two-sided bootstrap confidence intervals construction for the true period. We also obtain their coverage levels theoretically, and discuss the benefit of double-bootstrap confidence intervals for the parameter by which the coverage levels are substantially improved. Precisely, we show that the coverage error of single-bootstrap confidence intervals is of order n ^?1, decreasing to order n ^?2 when applying double-bootstrap methods. The simulation study given here is a numerical assessment of the theoretical work.     

Likelihood-Based Inference for Semi-Competing Risks

Consider semi-competing risks data (two times to concurrent events are studied but only one of them is right-censored by the other one) where the link between the times Y and C to non-terminal and terminal events, respectively, is modeled by a family of Archimedean copulas. Moreover, both Y and C are submitted to an independent right censoring variable D. We propose to estimate the parameter of the copula and some resulting survival functions using a pseudo maximum likelihood approach. The main advantage of this procedure is that it extends to multidimensional parameters copulas. We perform simulations to study the behavior of our estimation procedure and its impact on other related estimators and we apply our method to real data coming from a study on the Hodgkin disease.     

基于Bootstrap网络DEA改进方法的银行效率测度

文章运用储蓄存款作为中间变量的网络DEA模型提高效率测度准确性的同时,采用平滑Bootstrap方法进行效率纠偏来进一步改进效率测度方法,提高银行效率测度的准确性和有效性,设计了基于Bootstrap网络DEA的银行效率测度的新方法,基此实证分析了我国14家主要商业银行效率特征。实证结果显示,采用Bootstrap纠偏后的网络DEA银行效率比网络DEA银行效率有更高的准确性,国有商业银行和股份制商业银行的效率水平均呈现上升趋势,但股份制商业银行有更高的上升幅度,且于2008年超过国有商业银行的平均效率。此外,国有商业银行向有效前沿面收敛的速率降低,而股份制商业银行的收敛速率提高并超过国有股份制银行。     

环境因素对农户借贷行为的影响——来自新疆农村地区的经验证据

基于2013年国家统计局新疆调查总队农村住户调查数据,选取相关7个环境指标,运用Logit模型以及自助法(bootstrap),就环境对农户借贷行为的影响进行了实证分析,并探讨了不同收入条件和不同年龄段下环境对农户借贷行为的差异化影响。结果显示:就社会环境而言,社会不安定因素的增加会导致农户借贷行为减少;在经济环境中,农户家庭恩格尔系数与农户的借贷行为成反比关系,而财政补贴占总收入的比例、通信支出占总收入的比例与农户借贷行为的发生成正比例关系;在自然环境中,本村是否通公路、所处地势以及距离县城距离的远近均会对农户的借贷行为产生影响;在不同收入水平下,低等收入群体的借贷行为对社会环境的依赖程度较高,而中等收入群体的借贷行为受经济环境与自然环境的影响较大,但对于高收入群体来说经济环境更重要;在不同年龄层中,不论社会环境、经济环境还是自然环境对青年的借贷行为都有显著影响,而对于中年农户来说,其借贷行为主要受经济环境影响。     

Analysis and Management of Periodic Review,Order‐Up‐To Level Inventory Systems with Order Crossover

In this article, we investigate the (R, S) periodic review, order‐up‐to level inventory control system with stochastic demand and variable leadtimes. Variable leadtimes can lead to order crossover, in which some orders arrive out of sequence. Most theoretical studies of order‐up‐to inventory systems under variable leadtimes assume that crossovers do not occur and, in so doing, overestimate the standard deviation of the realized leadtime distribution and prescribe policies that can inflate inventory costs. We develop a new analytic model of the expected costs associated with this system, making use of a novel approximation of the realized (reduced) leadtime standard deviation resulting from order crossovers. Extensive experimentation through simulation shows that our model closely approximates the true expected cost and can be used to find values of R and S that provide an expected cost close to the minimum cost. Taking account of, as opposed to ignoring, crossovers leads, on average, to substantial improvements in accuracy and significant cost reductions. Our results are particularly useful for managers seeking to reduce inventory costs in supply chains with variable leadtimes.     

Estimation of Semiparametric Models when the Criterion Function Is Not Smooth

We provide easy to verify sufficient conditions for the consistency and asymptotic normality of a class of semiparametric optimization estimators where the criterion function does not obey standard smoothness conditions and simultaneously depends on some nonparametric estimators that can themselves depend on the parameters to be estimated. Our results extend existing theories such as those of Pakes and Pollard (1989), Andrews (1994a), and Newey (1994). We also show that bootstrap provides asymptotically correct confidence regions for the finite dimensional parameters. We apply our results to two examples: a ‘hit rate’ and a partially linear median regression with some endogenous regressors.     

Psychophysiological coherence training to moderate air traffic controllers’ fatigue on rotating roster

The nature of the current rotating roster, providing 24-h air traffic services over five irregular shifts, leads to accumulated fatigue which impairs air traffic controllers’ cognitive function and task performance. It is imperative to develop an effective fatigue risk management system to improve aviation safety based upon scientific approaches. Two empirical studies were conducted to address this issue. Study 1 investigated the mixed effect of circadian rhythm disorders and resource depletion on controllers’ accumulated fatigue. Then, study 2 proposed a potential biofeedback solution of quick coherence technique which can mitigate air traffic controllers’ (ATCOs’) fatigue while on controller working position and improve ATCOs’ mental/physical health. The current two-studies demonstrated a scientific approach to fatigue analysis and fatigue risk mitigation in the air traffic services domain. This research offers insights into the fluctuation of ATCO fatigue levels and the influence of a numbers of factors related to circadian rhythm and resource depletion impact on fatigue levels on study 1; and provides psychophysiological coherence training to increase ATCOs’ fatigue resilience to mitigate negative impacts of fatigue on study 2. Based on these two studies, the authors recommended that an extra short break for air traffic controllers to permit practicing the quick coherence breathing technique for 5 min at the sixth working hour could substantially recharge cognitive resources and increase fatigue resilience. Application: Present studies highlight an effective fatigue intervention based on objective biofeedback to moderate controllers’ accumulated fatigue as a result of rotating shift work. Accordingly, air navigation services providers and regulators can develop fatigue risk management systems based on scientific approaches to improve aviation safety and air traffic controller's wellbeing.