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Over the last 20 years the NEH heuristic of Nawaz, Enscore, and Ham published in this journal has been commonly regarded as the best heuristic for minimizing the makespan in permutation flow shops. In recent years some authors claimed to develop new heuristics that are competitive or outperform NEH. Our study reveals that these claims are not justified. We also address the issue of a fair comparison of the NEH results with those obtained by metaheuristics. Finally we conduct a thorough analysis of NEH leading to its modification which secures the optimality in the two-machine case and improves the general performance. 相似文献
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Jantine Voordouw Gerrit Antonides Margaret Fox Inmaculada Cerecedo Javier Zamora Belen de la Hoz Caballer Ewa Rokicka Judith Cornelisse-Vermaat Maciej Jewczak Pawel Starosta Marek L. Kowalska Monika J?drzejczak-Czechowicz Sonia Vázquez-Cortés Cano Escudero Bertine Flokstra de Blok Anthony Dubois Miranda Mugford Lynn J. Frewer 《Social indicators research》2012,107(3):465-482
This study estimates the effects of food hypersensitivity on individuals?? perceived welfare and well-being compared to non-food hypersensitive individuals. Study respondents were recruited in the Netherlands, Poland, Spain and UK. The difference in welfare between food hypersensitive respondents and those asymptomatic to foods was estimated using a subjective welfare approach, including income evaluation. Well-being was measured using the Cantril Ladder-of-Life Scale, and health status using the Self-Perceived Health Scale. The difference in well-being, welfare and health status between participant groups was explained further using a number of background variables. No significant within-country differences in welfare between food hypersensitive respondents and respondents asymptomatic to foods were found. In terms of well-being, adult food hypersensitive respondents and their spouses reported significantly less happiness than respondents and their spouses asymptomatic to foods in the Netherlands and Poland. In Spain, the spouses of the food hypersensitive respondents were significantly less happy than respondents aymptomatic to foods. The well-being of children did not significantly differ between groups. The degree of severity of food hypersensitivity was negatively related to overall health status. In Poland, food hypersensitive respondents reported worse health status compared to asymptomatic respondents. In Spain, the converse was true. Food hypersensitive respondents were generally less happy with their life as a whole than respondents asymptomatic to foods, presumably because they experienced more negative effects, which were not related to perceived health status. 相似文献
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ABSTRACTWe develop a new score-driven model for the joint dynamics of fat-tailed realized covariance matrix observations and daily returns. The score dynamics for the unobserved true covariance matrix are robust to outliers and incidental large observations in both types of data by assuming a matrix-F distribution for the realized covariance measures and a multivariate Student's t distribution for the daily returns. The filter for the unknown covariance matrix has a computationally efficient matrix formulation, which proves beneficial for estimation and simulation purposes. We formulate parameter restrictions for stationarity and positive definiteness. Our simulation study shows that the new model is able to deal with high-dimensional settings (50 or more) and captures unobserved volatility dynamics even if the model is misspecified. We provide an empirical application to daily equity returns and realized covariance matrices up to 30 dimensions. The model statistically and economically outperforms competing multivariate volatility models out-of-sample. Supplementary materials for this article are available online. 相似文献
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It is shown that a necessary and sufficient condition derived by Farebrother (1984)for a generalized ridge estimator to dominate the ordinary least-squares estimator with respect to the mean-square-error-matrix criterion in the linear regression model admits a similar interpretation as the well known criterion of Toro-Viz-carrondo and Wallace (1968)for the dominance of a restricted least-squares estimator over the ordinary least-squares estimator. Two other properties of the generalized ridge estimators, referring to the concept of admissibility, are also pointed out. 相似文献
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Pawel Korzynski Andrzej Krzysztof Kozminski Anna Baczynska Michael Haenlein 《European Management Journal》2021,39(2):226-235
Contrary to the previous leadership theories, which focus on specific and narrow aspects of leadership such as employee characteristics, leader’s authenticity, or boundary spanning, the bounded leadership theory is a broad and complex concept. It takes simultaneously many constraints, which are related to activities on an individual, team, organization, and stakeholder level. This study applies the bounded leadership theory to analyze the leadership constraints as the mediator of the relationship between leadership competencies and effectiveness. Our findings show that leaders’ competencies are not enough for them to be effective. Specific competencies enable leaders to overcome the set of constraints and then to increase their effectiveness. 相似文献
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Pawel R. Pordzik 《Statistical Papers》2012,53(2):299-304
Let
[^(\varveck)]{\widehat{\varvec{\kappa}}} and
[^(\varveck)]r{\widehat{\varvec{\kappa}}_r} denote the best linear unbiased estimators of a given vector of parametric functions
\varveck = \varvecKb{\varvec{\kappa} = \varvec{K\beta}} in the general linear models
M = {\varvecy, \varvecX\varvecb, s2\varvecV}{{\mathcal M} = \{\varvec{y},\, \varvec{X\varvec{\beta}},\, \sigma^2\varvec{V}\}} and
Mr = {\varvecy, \varvecX\varvecb | \varvecR \varvecb = \varvecr, s2\varvecV}{{\mathcal M}_r = \{\varvec{y},\, \varvec{X}\varvec{\beta} \mid \varvec{R} \varvec{\beta} = \varvec{r},\, \sigma^2\varvec{V}\}}, respectively. A bound for the Euclidean distance between
[^(\varveck)]{\widehat{\varvec{\kappa}}} and
[^(\varveck)]r{\widehat{\varvec{\kappa}}_r} is expressed by the spectral distance between the dispersion matrices of the two estimators, and the difference between sums
of squared errors evaluated in the model M{{\mathcal M}} and sub-restricted model Mr*{{\mathcal M}_r^*} containing an essential part of the restrictions
\varvecR\varvecb = \varvecr{\varvec{R}\varvec{\beta} = \varvec{r}} with respect to estimating
\varveck{\varvec{\kappa}}. 相似文献
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本文旨在提出用计算机模拟反映如木器厂工作的危险性,小型企业关注未使用相对安全设备的工作场地,木器厂有许多潜在的危险情况如将木材从一个地方搬用到另一地方及高速旋转的车床可能对工人的直接伤害,这种危险状况可用虚拟现实进行仿真。 相似文献
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On pre-test estimation of parametric functions in the general Gauss-Markov model with quadratic risk
Pawel Pordzik 《Statistical Papers》1999,40(4):469-478
The approach to preliminary test estimation based on comparing the weighted quadratic risk function of two competing estimators
of β under the linear regression model {y,Xβ, σ2
I} is extended to the case when a given vector of parametric functions κ=Kβ is to be estimated under the general Gauss-Markov model. 相似文献
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