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961.
Mark Ebden Armin Stranjak Stephen Roberts 《Journal of the Royal Statistical Society. Series C, Applied statistics》2010,59(1):163-173
Summary. We propose an approach for estimating the date of lost confidence of jet engines, which are devices with multiple components subject to disruption. A mixed Weibull distribution is estimated from a large data set subject to censoring at various times. Parametric uncertainty is derived analytically and mapped visually onto the functions of use in reliability theory, including the hazard function. We demonstrate the use of the method on a database of disruption times for components in 325 jet engines. 相似文献
962.
Causal inference approaches in systems genetics exploit quantitative trait loci (QTL) genotypes to infer causal relationships among phenotypes. The genetic architecture of each phenotype may be complex, and poorly estimated genetic architectures may compromise the inference of causal relationships among phenotypes. Existing methods assume QTLs are known or inferred without regard to the phenotype network structure. In this paper we develop a QTL-driven phenotype network method (QTLnet) to jointly infer a causal phenotype network and associated genetic architecture for sets of correlated phenotypes. Randomization of alleles during meiosis and the unidirectional influence of genotype on phenotype allow the inference of QTLs causal to phenotypes. Causal relationships among phenotypes can be inferred using these QTL nodes, enabling us to distinguish among phenotype networks that would otherwise be distribution equivalent. We jointly model phenotypes and QTLs using homogeneous conditional Gaussian regression models, and we derive a graphical criterion for distribution equivalence. We validate the QTLnet approach in a simulation study. Finally, we illustrate with simulated data and a real example how QTLnet can be used to infer both direct and indirect effects of QTLs and phenotypes that co-map to a genomic region. 相似文献
963.
964.
Recent studies of old-age mortality trends assess whether longevity improvements over time are linked to increasing compression of mortality at advanced ages. The historical backdrop of these studies is the long-term improvement in a population's socioeconomic resources that fueled longevity gains. We extend this line of inquiry by examining whether socioeconomic differences in longevity within a population are accompanied by old-age mortality compression. Specifically, we document educational differences in longevity and mortality compression for older men and women in the United States. Drawing on the fundamental cause of disease framework, we hypothesize that both longevity and compression increase with higher levels of education and that women with the highest levels of education will exhibit the greatest degree of longevity and compression. Results based on the Health and Retirement Study and the National Health Interview Survey Linked Mortality File confirm a strong educational gradient in both longevity and mortality compression. We also find that mortality is more compressed within educational groups among women than men. The results suggest that educational attainment in the United States maximizes life chances by delaying the biological aging process. 相似文献
965.
966.
Mentoring is being increasingly used by companies as a means of fostering employee learning and development. Limited research exists from the perspective of the mentor on these relationships. This article presents the results of a qualitative study that investigated the characteristics that the ideal mentor should possess and ways that both mentors and protégés can make mentoring relationships most effective. Findings from the study are used to frame suggestions for future research and practice. 相似文献
967.
The association between the time a mother spends at work and in different child care activities is investigated, using data from the 1981 National Longitudinal Survey of Youth (NLSY). The mothers who worked on the index day spent almost one hour less time in physical care, one-half hour less time in interactive care, and over two hours less time in passive supervision of their children. The effects of a set of predictors on time use at work, time use in physical care, interactive care, and passive supervision of children were estimated using a covariance structure model. When the effects of these predictors are controlled, the number of hours at work predicts: (a) a small reduction in time spent in interactive care, and (b) larger reductions in time spent in physical care and passive supervision. 相似文献
968.
Mark McPeak 《Nonprofit management & leadership》1999,10(2):185-201
PLAN International (PLAN) developed a methodology to ensure that its robust growth in the late 1980s and early 1990s was directed in a manner that was explicitly consistent with organizational strategy. This methodology enabled it to target its growth toward countries where child-related need was greater and in which its program approach was likely to have most impact. Managers of international nongovernmental organizations should find PLAN's experience relevant as they strive to strike a balance between organizational expansion, with its pressures and distractions, and the crucial need to maintain institutional focus. 相似文献
969.
Norman A. Eisenberg Michael P. Lee Timothy J. McCartin Keith I. McConnell Mark Thaggard Andrew C. Campbell 《Risk analysis》1999,19(5):847-876
The U.S. Nuclear Regulatory Commission (NRC) staff has developed a performance assessment capability to address three programmatic areas in nuclear waste management: high-level waste, low-level waste, and decommissioning of licensed facilities (license termination). The NRC capability consists of: (1) methodologies for performance assessment; (2) models and computer codes for estimating system performance; (3) regulatory guidance in various forms, such as regulations, Branch Technical Positions, and Standard Review Plans; and (4) a technical staff experienced in executing and evaluating performance assessments for a variety of waste systems. Although the tools and techniques are refined for each programmatic area, general approaches and similar issues are encountered in all areas. 相似文献
970.
As global markets and technology change, time‐based competitors create product development and manufacturing practices that reduce response time and enhance customization capabilities. These practices require an information‐rich internal environment that is capable of flexible resource deployment and direct and continuous feedback. To build this environment, time‐based competitors are developing end‐user capabilities and involving them in information systems (IS) activities. Data collected from 265 manufacturers were used to determine if firms with high levels of time‐based product development and time‐based manufacturing practices also have high levels of end‐user involvement in IS‐related activities, end‐user training effectiveness, and end‐user computing skills. The results of this study support that contention. 相似文献