排序方式: 共有13条查询结果,搜索用时 15 毫秒
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J. M. G. Salmerón G. Aparicio L. G. Casado I. García E. M. T. Hendrix B. G.-Tóth 《Journal of Combinatorial Optimization》2017,33(2):389-402
In several areas like global optimization using branch-and-bound methods for mixture design, the unit n-simplex is refined by longest edge bisection (LEB). This process provides a binary search tree. For \(n>2\), simplices appearing during the refinement process can have more than one longest edge (LE). The size of the resulting binary tree depends on the specific sequence of bisected longest edges. The questions are how to calculate the size of one of the smallest binary trees generated by LEB and how to find the corresponding sequence of LEs to bisect, which can be represented by a set of LE indices. Algorithms answering these questions are presented here. We focus on sets of LE indices that are repeated at a level of the binary tree. A set of LEs was presented in Aparicio et al. (Informatica 26(1):17–32, 2015), for \(n=3\). An additional question is whether this set is the best one under the so-called \(m_k\)-valid condition. 相似文献
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Whistleblowers play an important role diagnosing research misconduct, but often experience severe negative consequences. That is also true for incorrectly accused scientists. Both categories are vulnerable and deserve protection. Whistleblowers must proceed carefully and cautiously. Anonymous whistleblowing should be discouraged but cannot be ignored when the allegations are specific, serious, and plausible. When accused of a breach of research integrity it is important to be as transparent as possible. Sometimes accusations are false in the sense that the accuser knows or should know that the allegations are untrue. A mala fide whistleblower typically does not act carefully and we postulate a typology that may help in detecting them. Striking the right balance between whistleblower protection and timely unmasking false and identifying incorrect accusations is a tough dilemma leaders of research institutions have to face. 相似文献
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Goldsmith J Caffo B Crainiceanu C Reich D Du Y Hendrix C 《The annals of applied statistics》2011,5(1):337-363
We are concerned with the estimation of the exterior surface and interior summaries of tube-shaped anatomical structures. This interest is motivated by two distinct scientific goals, one dealing with the distribution of HIV microbicide in the colon and the other with measuring degradation in white-matter tracts in the brain. Our problem is posed as the estimation of the support of a distribution in three dimensions from a sample from that distribution, possibly measured with error. We propose a novel tube-fitting algorithm to construct such estimators. Further, we conduct a simulation study to aid in the choice of a key parameter of the algorithm, and we test our algorithm with validation study tailored to the motivating data sets. Finally, we apply the tube-fitting algorithm to a colon image produced by single photon emission computed tomography (SPECT) and to a white-matter tract image produced using diffusion tensor imaging (DTI). 相似文献
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Lewellyn Hendrix 《Sociological spectrum》2013,33(2):125-145
The nature‐culture issue in recent exemplary cross‐cultural works is examined from a causal modeling viewpoint. The causal models in most current explanations do not depart radically from those of the 1950s. The recent models mostly continue to emphasize the interaction of biological and sociocultural factors in producing sexual inequality. In all of the theories examined, economic production is singled out as important in the sociocultural realm. Some researchers sidestep the nature‐culture issue by dealing solely with variation, or by translating conceivably biological factors into social causes. Biosocial writers have produced the most novel causal model—one which incorporates the effect of culture on biology. These findings suggest that we need to pay attention to the causal networks of theories, rather than dichotomizing them into “biological” and “sociological” explanations. 相似文献
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Abstract. In general, the risk of joint extreme outcomes in financial markets can be expressed as a function of the tail dependence function of a high‐dimensional vector after standardizing marginals. Hence, it is of importance to model and estimate tail dependence functions. Even for moderate dimension, non‐parametrically estimating a tail dependence function is very inefficient and fitting a parametric model to tail dependence functions is not robust. In this paper, we propose a semi‐parametric model for (asymptotically dependent) tail dependence functions via an elliptical copula. Under this model assumption, we propose a novel estimator for the tail dependence function, which proves favourable compared to the empirical tail dependence function estimator, both theoretically and empirically. 相似文献
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Trajectories of body mass and self-concept in black and white girls: the lingering effects of stigma
As a stigmatizing condition, obesity may lead to the internalization of devalued labels and threats to self-concept. Modified labeling theory suggests that the effects of stigma may outlive direct manifestations of the discredited characteristic itself. This article considers whether obesity's effects on self-concept linger when obese youth enter the normal body mass range. Using longitudinal data from the National Growth and Health Study on 2,206 black and white girls, we estimated a parallel-process growth mixture model of body mass linked to growth models of body image discrepancy and self-esteem. We found that discrepancy was higher and self-esteem lower in formerly obese girls compared to girls always in the normal range and comparable to chronically obese girls. Neither body image discrepancy nor self-esteem rebounded in white girls despite reduction in body mass, suggesting that the effects of stigma linger. Self-esteem, but not discrepancy, did rebound in black girls. 相似文献
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