A constraint programming-based solution approach for medical resident scheduling problems

Persistent calls come from within the graduate medical education community and from external sources for regulating the resident duty hours in order to meet the obligations about the quality of resident education, the well-being of residents themselves, and the quality of patient care services. The report of the Accreditation Council for Graduate Medical Education (ACGME) proposes common program requirements for resident hours. In this paper, we first develop a mixed-integer programming model for scheduling residents’ duty hours considering the on-call night, day-off, rest period, and total work-hour ACGME regulations as well as the demand coverage requirements of the residency program. Subsequently, we propose a column generation model that consists of a master problem and an auxiliary problem. The master problem finds a configuration of individual schedules that minimizes the sum of deviations from the desired service levels for the day and night periods. The formulation of this problem is possible by representing the feasible schedules using column variables, whereas the auxiliary problem finds the whole set of feasible schedules using constraint programming. The proposed approach has been tested on a series of problems using real data obtained from a hospital. The results indicate that high-quality schedules can be obtained within a few seconds.     

Keeping up-to-date with information technology: Testing a model of technological knowledge renewal effectiveness for IT professionals

In a rapidly changing IT environment, IT professionals need to keep abreast of technological knowledge. We examined how well this is achieved by developing a motivational model of “technological knowledge renewal effectiveness.” We hypothesized that (1) renewal effectiveness was influenced by the IT professional's career orientation, perceived IT dynamism, tolerance of ambiguity, delegation; and (2) that this positively affected both intrinsic and extrinsic job satisfaction. Survey data from 126 IT professionals was used to test the hypotheses. The results generally supported the research model. We discussed the implications of these results in both research and practice.     

基于手机模块上的短信服务系统的研究和探讨

短信系统无论是在人们的现代生活中还是在企业等各行业的现代化办公中发挥越来越重要的作用,本文通过基于手机模块短信系统的现状、设计与应用功能实现的分析,结合开发商和用户需求的实际,以及对短信模块设计中一些技术设计思想要求的介绍,从多角度分析说明了现阶段手机短信系统发挥的作用、实现的价值和意义,存在的问题和以及社会对短信系统的期望和要求,希望达到的效果,并从理论和实践上说明了其可行性、实用性。     

基于系统平均停机时间的维修策略研究

文章研究了单部件可修系统的最优维修更换问题．假定系统不能“修复如新”．分别以（1）系统的故障次数N；（2）系统的工作时间T；（3）二元函数（N．T）为策略，利用几何过程确定最优的策略，使得系统经长期运行单位时间内平均停机时间达到最少．并求出了系统经长期运行单位时间内平均停机时间的明显表达式，对故障系统的维修和更换具有参考价值和指导意义．     

Reliability analysis of a repairable k-out-of-n system with some components being suspended when the system is down

A k-out-of-n system with independent exponential components is investigated. It is assumed that some working components are suspended as soon as the system is down, repair starts immediately when a component fails and repair times are independent and exponentially distributed. Formulas for various reliability indices of the system including mean time between failures, mean working time in a failure–repair cycle, and mean down time in a failure–repair cycle are derived.     

居民夏季用电需求灰色关联预测模型的研究

在定性分析北京地区GDP，居民降温设备拥有量，电费支出占可支配收入比例等因素时该地区居民夏季用电需求的基础上，应用灰色关联理论，找出了影响居民夏季用电需求增加的主要因素，建立了关于居民夏季用电需求量与这些影响因素变量的GM(1，n)模型，描述了关联因素时居民夏季用电需求的影响，为电力部门做好负荷预测，制定夏季负荷的调整方案及其电网的电力运行计划等提供了参考依据。     

高压断路器的更换技术和日本的更换量化准则

叙述了高压断路器更换的理由,高压断路器的寿命、影响寿命的因素和合理的更换时机。还介绍了日本推荐的两种更换高压断路器的量化准则。     

基于都市发展阶段论的城市居住隔离研究

本文归纳并总结我国居住隔离研究的现状,从研究成果及应用性、研究层面及针对性和规划对策三方面评述居住隔离研究存在的问题,在此基础上引入并剖析都市发展阶段论与居住隔离的内在关联,结合我国城市化特点构建基于都市发展阶段论的居住隔离研究框架,探讨我国居住隔离问题的应对策略,并着重论述框架中各类居住隔离问题的混居措施。     

Dynamic response of a beam to the train of moving forces driven by an Erlang renewal process

Dynamic response of a beam to a random train of moving forces moving with the same velocity is considered. Unlike a widely used Poisson process model, a more adequate Erlang renewal process is used as a process driving the train of forces. Normal-mode approach is used to convert the problem into that of a renewal driven train of general pulses. Consequently the modal responses are the filtered renewal processes and are expressed as integrals with respect to the response to a single pulse (passage of a force) and to the increments of the counting renewal process. The expressions for the mean values and cross-correlations of modal responses are obtained as single and double integrals, respectively. The results are presented in terms of the renewal density of the underlying Erlang counting process. Mean value and variance of the mid-span deflection of the beam are determined by numerical evaluation of the pertinent integrals. Numerical analysis is carried out for the Erlang processes with integer parameter $k=2$, $k=3$ and 4 and, for comparison, also for a Poisson process. Different traffic conditions such as the velocity and the mean arrival rate of vehicles are taken into account.     

Empowering Local Communities? An International Review of Community Land Trusts

This paper aims to investigate the premise that community land trusts (CLTs) offer a method of delivering affordable housing that empowers local communities and provides democratic management of community assets. The paper provides a comparative analysis of CLT developments in England, Scotland and the USA, reviewing the policy and literature to identify two key approaches that underpin CLTs: an approach to property development that emphasises resale restrictions used to preserve housing use for the CLT's target clientele, and an approach to citizen governance that privileges local communities. The paper identifies a variation of practices that underpin the operation of CLTs in each country and uses the advanced developments in Scotland and the USA to illustrate some of the challenges that remain if the CLT sector in England is to continue its recent growth.