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841.
This research focuses on the estimation of tumor incidence rates from long-term animal studies which incorporate interim sacrifices. A nonparametric stochastic model is described with transition rates between states corresponding to the tumor incidence rate, the overall death rate, and the death rate for tumor-free animals. Exact analytic solutions for the maximum likelihood estimators of the hazard rates are presented, and their application to data from a long-term animal study is illustrated by an example. Unlike many common methods for estimation and comparison of tumor incidence rates among treatment groups, the estimators derived in this paper require no assumptions regarding tumor lethality or treatment lethality. The small sample operating characteristics of these estimators are evaluated using Monte Carlo simulation studies. 相似文献
842.
As the field of family therapy has evolved, there has been growing recognition as to the importance of gender in family therapy. To prepare the next generation of family therapists adequately, it is important that they recognize the many and complex ways in which gender permeates their work. In this article we present an integrative model to help educators teach family therapists about gender issues. The model examines how gender influences clinical work on multiple levels, including contextual levels such as society and the marriage and family therapy field. The model also acknowledges how gender can influence individuals, including clients, therapists, and supervisors. Finally, the model attempts to capture the complexity of how gender can impact the relational dynamics between two or more individuals. 相似文献
843.
The gap between research and clinical practice is one of the key challenges facing family therapy. Clinicians often fail to incorporate research findings into their practice because they do not know how to search, evaluate, or apply research to their clinical work. The purpose of this article is to help clinicians become better consumers of research. This article explores the potential value of research to clinicians, as well as negative beliefs that clinicians may have about research. The article also describes how clinicians can use research to inform their clinical work, as well as potential challenges that can be encountered. 相似文献
844.
Berke EM Ackermann RT Lin EH Diehr PH Maciejewski ML Williams B Patrick MB LoGerfo JP 《Journal of aging and physical activity》2006,14(3):313-324
This study evaluated the effect of distance on the likelihood of initiating and maintaining regular use of a fitness-program benefit in a population of managed Medicare seniors. We studied 8,162 participants and nonparticipants in a managed-care fitness-program benefit: a structured group exercise program or an unstructured health-club membership. Participants in both programs lived significantly closer to facilities than nonparticipants did (structured, p < .001; unstructured, p = .017). Participants living closer to unstructured-program sites attended more frequently than those farther away (p = .008). Distance was not correlated with frequency of use in the structured program (p = .49). Collectively, these analyses demonstrate that distance is related to uptake and, in some cases, continued use of a fitness-program benefit. Health systems providing fitness-program benefits as a way to increase physical activity levels of their plan members should consider location of program facilities in relation to members' home addresses to maximize use of the benefit. 相似文献
845.
Umberson D Williams K Powers DA Liu H Needham B 《Journal of health and social behavior》2006,47(1):1-16
We work from a life course perspective and identify several reasons to expect age and gender differences in the link between marital quality and health. We present growth curve evidence from a national longitudinal survey to show that marital strain accelerates the typical decline in self-rated health that occurs over time and that this adverse effect is greater at older ages. These findings fit with recent theoretical work on cumulative adversity in that marital strain seems to have a cumulative effect on health over time-an effect that produces increasing vulnerability to marital strain with age. Contrary to expectations, marital quality seems to affect the health of men and women in similar ways across the life course. 相似文献
846.
A GPSS/360 model was developed to investigate the behavior of a university's motor pool dispatch fleet. Time-series data were collected and frequency distributions were constructed for vehicle request patterns and trip-duration times. Regression analysis was performed to formulate trip mileage generators as functions of service time. Appropriate statistical goodness-of-fit tests were conducted to ascertain the extent of congruence between actual system behavior and expectations based on a number of theoretical distributions. Analysis of simulated response variables indicates that the model's internal structure reproduces reality to a high degree. Fifteen years of simulated experience were generated for six alternative fleet size configurations; results suggest that reductions in existing fleet capacity could be realized without effecting undue impairment in service levels. 相似文献
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849.
Elliott F. Williams Süleyman Tüfekcli Mehmet Akansel 《Production and Operations Management》1997,6(1):74-96
Lot streaming is the process of splitting a job or lot into sublots to reduce its makespan on a sequence of machines. The goal in the lot streaming problem is to find the optimal size of each sublot that will minimize the makespan. The makespan is defined as the time the last sublot completes its processing on the last machine. If the sizes of these sublots are restricted to remain the same on all machines, the solution is called a consistent sublot solution. However, if the sizes of the sublots are allowed to vary, the solution is referred to as a nonconsistent or variable sublot solution. Also, if the machines must be in operation continuously from the first to the last sublot, the solution is a no idling solution. When setups are explicitly considered in the problem, there will be two cases. If setups on each machine require some portion of the first sublot be present by the machine, the problem is referred to as the attached setup time problem. If setups can be performed ahead of time before the first sublot reaches the particular machine, the corresponding problem is referred to as the detached setup problem. Finally, if the machines are allowed to be idle between the processing of sublots, the resultant solution is an intermittent idling solution. In this paper, the consistent sublot lot streaming problem with intermittent idling and no setups is discussed. The models developed also assume that the number of sublots are fixed and known. The m machine two sublot lot streaming problem is reviewed. An algorithm for the three sublot, m machine problem is derived using a network representation of the problem. The complexity of the algorithm is O (m2). Finally, using the insights from three sublot problem, a heuristic algorithm is provided for the m machine, n sublot problems. The results on the proposed heuristic are very encouraging; average percent deviation from optimal makespan is approximately at 0.76% on 155 randomly generated problems with different m and n values. 相似文献