A practical assessment of risk-averse approaches in production lot-sizing problems

ABSTRACT

This paper presents an empirical assessment of four state-of-the-art risk-averse approaches to deal with the capacitated lot-sizing problem under stochastic demand. We analyse two mean-risk models based on the semideviation and on the conditional value-at-risk risk measures, and alternate first and second-order stochastic dominance approaches. The extensive computational experiments based on different instances characteristics and on a case-study suggest that CVaR exhibits a good trade-off between risk and performance, followed by the semideviation and first-order stochastic dominance approach. For all approaches, enforcing risk-aversion helps to reduce the cost-standard deviation substantially, which is usually accomplished via increasing production rates. Overall, we can say that very risk-averse decision-makers would be willing to pay an increased price to have a much less risky solution given by CVaR. In less risk-averse settings, though, semideviation and first-order stochastic dominance can be appealing alternatives to provide significantly more stable production planning costs with a marginal increase of the expected costs.     

Visualization of temporal differences between dominant perceptions in temporal dominance of sensations (TDS) and temporal check-all-that-apply (TCATA) perceptions using dominance-highlighted TCATA (dTCATA) curves

The temporal dominance of sensations (TDS) method measures dynamic changes of panelists’ attention to the sensory attributes of products. The temporal check-all-that-apply (TCATA) method measures all sensory attributes perceived at each moment of an evaluation. However, unlike in TDS, significant levels cannot be calculated in TCATA. This study proposes the use of dominance-highlighted TCATA (dTCATA) curves, which are highlighted TCATA curves that show significant time periods for the TDS data of different panels. Twelve R&D panelists evaluated five commercial corn soups using the TCATA method. Then, 125 consumer panelists evaluated the same products using the TDS method. The dTCATA curves showed TCATA curves for all attributes for each product evaluated by the R&D panel highlighted with the dominance rates identified by the consumer panel in the TDS evaluation. For example, for product 1, some attributes (sweet, viscosity) showed relatively high citation proportions in the TCATA evaluations of the R&D panel and significant dominance rates in the TDS evaluations of the consumer panel. In contrast, consommé flavor showed relatively low citation proportions in TCATA but significant dominance rates in TDS. By merging TDS and TCATA data, we could compare consumers’ dominant sensations with the evaluations of R&D panelists. This comparison could provide useful insights to product developers. In some cases, we observed attributes with significant dominance rates that were under-identified by the R&D panel in TCATA. This could suggest that most of the R&D panel may not have perceived these attributes; therefore, during product development, these attributes should be carefully considered.     

基于人工免疫的机车二系调簧方法

为进一步提高电力机车二系支承载荷调整优化算法的性能,解决已有算法在加垫数量控制上的欠缺,并避免冗余计算,提出了一种基于人工免疫算法的两级结构机车二系载荷调整方法:免疫优势克隆选择多目标算法。针对调簧问题的偏好结构特点,设计具有调簧寻优阶段和可控加垫量寻优阶段的两级寻优算法,分别定义了两个阶段的寻优目标和可行域,进一步将调簧问题的先验知识作为免疫优势引入算法设计中,并结合调簧问题的具体特点以及人工免疫知识设计了特定的抗体编码形式、变异策略和免疫优势获得算法。对不同车型的多次应用试验统计结果表明:该算法不仅具有良好的优化载荷分布特性,还能稳定地控制调簧产生的加垫数量,并且能够避免冗余计算,极大地提高了调簧效率和实际应用价值。     

Efficient meta-heuristics based on various dominance criteria for a single-machine bi-criteria scheduling problem with rejection

In this paper, we try to fill in the gap between theory and practice in production scheduling by defining a new term as “rejection” and treating the corresponding scheduling problem with multi-objective optimization approach. We study a bi-objective single machine scheduling problem with rejection. At the beginning of scheduling time horizon, scheduler needs to decide which job shall be rejected due to the resource constraints regarding two objective functions: minimization of total weighted completion time of accepted jobs and total rejection penalty of rejected jobs. We develop different algorithms to find the best estimation of Pareto-optimal front for this problem. In order to improve the quality of the solutions, on the one hand, and facilitate the process of selecting best solution for the final decision maker, on the other hand, we integrate various dominance criteria into our proposed algorithms. Finally we compare the performance of those methods by testing on a large set of instances and highlight the advantages and weak points of each one.     

基于决策空间变换最近邻方法的Pareto支配性预测

为提高在决策空间运用最近邻方法预测多目标优化Pareto支配性的精度，提出一种基于决策空间变换的最近邻预测方法.在分析目标函数与决策分量相关性的基础上，提出属性变化趋势模型的构造方法，建立低计算成本的属性趋势代理模型.通过属性趋势模型引入决策空间到目标空间的映射知识，对多目标问题的决策空间进行变换，使决策空间的最近邻更有效反映目标空间的最近邻.选取具有不同相关系数特征的典型多目标优化问题，进行Pareto支配性预测的可对比实验，结果表明在新空间中运用最近邻方法可显著提高分类准确性.     

Direct Application of Rep‐PCR on Type I Sourdough Matrix to Monitor the Dominance and Persistence of a Lactobacillus plantarum Starter Throughout Back‐Slopping

This study describes the optimization and application of repetitive element‐PCR (rep‐PCR) technique directly on microbial DNA extracted from type I sourdoughs for fast monitoring of a Lb. plantarum starter strain (P1FMC) throughout daily back‐slopping. The challenge was to follow and study the performance of a starter culture directly in sourdoughs without cultivation on selective media. The extraction of good quality microbial DNA suitable for amplification from a complex matrix such as dough was the first target. In addition, the objective to obtain a clear rep‐PCR profile referable to a specific starter strain among a microbial community was pursued. Co‐inoculum trials, in flour matrix, with Lb. plantarum P1FMC and L. lactis LC71 strains and, subsequently, type I sourdough back‐slopping trials were performed. The rep‐PCR amplification profiles obtained were clearly referable to that of Lb. plantarum P1FMC starter in both co‐inoculum trials (also when it was present with one order of magnitude less with respect to L. lactis LC71) and back‐slopping trials where it dominated the fermentation process with loads of 10⁸ cfu g^?1 and prevailed on the autochthonous microbiota. Thus, the approach proposed in this paper could be considered a methodological advancement, based on a culture‐independent one‐step rep‐PCR, suitable for fast monitoring of starter performance.     

A novel approach to interval comparison and application to software quality evaluation

Owing to increasing complexity in the real world, many attributes in decision science are uncertain. The interval data are more suitable for characterising those attributes. The interval comparison is an important research topic in this background. This paper proposes a new method for comparing two intervals based on a two-dimensional geometric interpretation. The equivalence is illustrated through a proof. Some mathematical experiments are provided to illustrate the validity. The proposed method is applied to the quality evaluation of software product. The results show that the provided method has important implications in both theoretical and practical perspectives.     

Evidence that gendered wording in job advertisements exists and sustains gender inequality.

Social dominance theory (Sidanius & Pratto, 1999) contends that institutional-level mechanisms exist that reinforce and perpetuate existing group-based inequalities, but very few such mechanisms have been empirically demonstrated. We propose that gendered wording (i.e., masculine- and feminine-themed words, such as those associated with gender stereotypes) may be a heretofore unacknowledged, institutional-level mechanism of inequality maintenance. Employing both archival and experimental analyses, the present research demonstrates that gendered wording commonly employed in job recruitment materials can maintain gender inequality in traditionally male-dominated occupations. Studies 1 and 2 demonstrated the existence of subtle but systematic wording differences within a randomly sampled set of job advertisements. Results indicated that job advertisements for male-dominated areas employed greater masculine wording (i.e., words associated with male stereotypes, such as leader, competitive, dominant) than advertisements within female-dominated areas. No difference in the presence of feminine wording (i.e., words associated with female stereotypes, such as support, understand, interpersonal) emerged across male- and female-dominated areas. Next, the consequences of highly masculine wording were tested across 3 experimental studies. When job advertisements were constructed to include more masculine than feminine wording, participants perceived more men within these occupations (Study 3), and importantly, women found these jobs less appealing (Studies 4 and 5). Results confirmed that perceptions of belongingness (but not perceived skills) mediated the effect of gendered wording on job appeal (Study 5). The function of gendered wording in maintaining traditional gender divisions, implications for gender parity, and theoretical models of inequality are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

模拟电路故障诊断的信息融合新方法

针对测试信息不足造成模拟电路故障诊断准确率较低的问题,为充分利用有限测试信息,提出一种模拟电路故障诊断信息融合新方法.首先,将采集的故障样本集变换到不同特征空间,然后利用所提出的马氏距离分布熵求取各特征空间的相对优势分类集,在此基础上,定义相对优势属性约简提取各特征空间的局部最佳可分性信息,最后,对基分类器结合所提出的自适应类模糊密度赋值方法进行模糊积分融合.国际标准电路故障诊断实例表明,所提方法能有效提高模拟电路的故障诊断率.