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111.
We study an Inventory Routing Problem in which the supplier has a limited production capacity and the stochastic demand of the retailers is satisfied with procurement of transportation services. The aim is to minimize the total expected cost over a planning horizon, given by the sum of the inventory cost at the supplier, the inventory cost at the retailers, the penalty cost for stock-out at the retailers and the transportation cost. First, we show that a policy based just on the average demand can have a total expected cost infinitely worse than the one obtained by taking into account the overall probability distribution of the demand in the decision process. Therefore, we introduce a stochastic dynamic programming formulation of the problem that allows us to find an optimal policy in small size instances. Finally, we design and implement a matheuristic approach, integrating a rollout algorithm and an optimal solution of mixed-integer linear programming models, which is able to solve realistic size problem instances. Computational results allow us to provide managerial insights concerning the management of stochastic demand.  相似文献   
112.
Concordance correlation coefficient (CCC) is one of the most popular scaled indices used to evaluate agreement. Most commonly, it is used under the assumption that data is normally distributed. This assumption, however, does not apply to skewed data sets. While methods for the estimation of the CCC of skewed data sets have been introduced and studied, the Bayesian approach and its comparison with the previous methods has been lacking. In this study, we propose a Bayesian method for the estimation of the CCC of skewed data sets and compare it with the best method previously investigated. The proposed method has certain advantages. It tends to outperform the best method studied before when the variation of the data is mainly from the random subject effect instead of error. Furthermore, it allows for greater flexibility in application by enabling incorporation of missing data, confounding covariates, and replications, which was not considered previously. The superiority of this new approach is demonstrated using simulation as well as real‐life biomarker data sets used in an electroencephalography clinical study. The implementation of the Bayesian method is accessible through the Comprehensive R Archive Network. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
113.
通过对GX教材、教学原则进行教学实验研究,探讨了提高黎族地区初中数学教育质量问题,阐明了在黎族地区使用GX教材教法进行教学能解决海南黎族初中数学教学中存在的问题。  相似文献   
114.
本文首先对产业集群研究的历史进行了回顾 ,列举了产业集群促进区域经济发展的若干实例。通过对江西星火工业园有机硅产业集群案例的实证分析揭示了产业集群的形成因素 ,探讨了地方政府在集群规划中的作用 ,并提出了地方政府应该采取的若干对策  相似文献   
115.
为解决有限的学习时间与知识爆炸之间的矛盾,从教学本质出发,将PBL教育理念在数学建模课程的教与学方面进行了实践,并将实践结果与传统模式下的教学进行对照,发现以PBL教育理念为指导的教与学不仅能够激发学生的学习兴趣,而且有利于形成学生的创新思维与创新能力。  相似文献   
116.
At the beginning of the 1930's Sweden had one of the lowest reproduction rates in Europe, and a decline in population was regarded as imminent. Since then, however, developments have shown a different trend and the natural increase has become higher, the fears about a decrease in population thus being considerably lessened or entirely removed.  相似文献   
117.
Various methods have been proposed for smoothing under the monotonicity constraint. We review the literature and implement an approach of monotone smoothing with B-splines for a generalized linear model response. The approach is expressed as a quadratic programming problem and is easily solved using the statistical software R. In a simulation study, we find that the approach performs better than other approaches with much faster computation time. The approach can also be used for smoothing under other shape constraints or mixed constraints. Supplementary materials of the appendices and R code to implement the developed approach is available online.  相似文献   
118.
Optimal string alignment is used to discover evolutionary relationships or mutations in DNA/RNA or protein sequences. Errors, missing parts or uncertainty in such a sequence can be covered with wild cards, so-called wild bases. This makes an alignment possible even when the data are corrupted or incomplete. The extended pairwise local alignment of wild card DNA/RNA sequences requires additional calculations in the dynamic programming algorithm and necessitates a subsequent best- and worst-case analysis for the wild card positions. In this paper, we propose an algorithm which solves the problem of input data wild cards, offers a highly flexible set of parameters and displays a detailed alignment output and a compact representation of the mutated positions of the alignment. An implementation of the algorithm can be obtained at https://github.com/sysbio-bioinf/swat+ and http://sysbio.uni-ulm.de/?Software:Swat+.  相似文献   
119.
Hedayat et al. [1988a. Sampling plans excluding contiguous units. J. Statist. Plann. Inference 19, 159–170; 1988b. Designs in survey sampling avoiding contiguous units. In: Krishnaiah, P.R., Rao, C.R. (Eds.). Handbook of Statistics, vol. 6. Elsevier, Amsterdam, pp. 575–583] first introduced balanced sampling designs for the exclusion of contiguous units. Sampling plans that excluded the selection of contiguous units within a given sample, while maintaining a constant second-order inclusion probability for non-contiguous units, were investigated for finite populations of N units arranged in a circular, one-dimensional ordering. There remain many open questions about the existence of such plans and their extension to plans excluding adjacent units. We present new generation techniques and new balanced sampling plans for the exclusion of adjacent units under finite, one-dimensional, circularly and linearly ordered populations.  相似文献   
120.
标记是指某种事物的代号,是通过一一对应的方式用简洁的形式表现复杂的事物。为探讨不同标记对3-5岁幼儿数学语言理解的影响,选取某幼儿园160名3-5岁幼儿,随机分为空间标记组、序数标记组和颜色标记组,使用操作任务和《学前儿童数学语言评估》量表,测查幼儿对于数学语言的理解状况。结果表明:3-5岁幼儿在操作任务中的表现存在显著的年龄差异和组间差异;序数标记组和空间标记组的幼儿在操作任务中的得分与数学语言评估量表中的得分呈中等程度相关,且这两组幼儿在操作任务中的正确率高于数学语言评估量表中与序数、空间相关题目的正确率。在教育实践中,教师应将数学语言贯穿于幼儿数学学习的全过程、为幼儿提供适宜且有层级的支架物、重视幼儿在数学学习中的操作与表达。  相似文献   
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