Multi-period dynamic supply contracts with cancellation

This paper considers a class of multi-period dynamic supply contracts in which a buyer orders a product from a supplier in each period and the supplier allows the buyer to cancel a portion of an outstanding order with penalty during a planning horizon. We assume that both the buyer and the supplier have common knowledge. We first characterize the buyer's ordering and canceling policy that minimizes his expected cost during the planning horizon. We also characterize the supplier's optimal production policy under a very mild assumption on the costs of production and storage. Based on this structure, we then use simulation to show how the supplier chooses cancellation costs that minimize her expected cost during the planning horizon. Our simulation shows that both the buyer and the supplier would benefit from the contract.     

Assessing effect of global inventory planning with enterprise-wide information for a large manufacturer

This paper studies how a global manufacturer with many subsidiaries can achieve enhanced business value for the organization by sharing information within its supply chain network. Specifically, the uncertainties in the demands from the downstream distribution center affect the inventory levels at the upstream distribution center under different inventory policies, considering the uncertain lead times and the given order fill rates. With a generic simulation model and real data, we evaluate the magnitude of savings in inventory under the new inventory policy where information can be shared among subsidiaries, compared to the status quo where subsidiaries run independently with no information sharing. The results show that average inventory level at the upstream DC under the new policy would be reduced by approximately 3%. Considering the given manufacturer's global supply chain distribution network holds about $4 billion in average inventory, the 3% improvement is a very significant savings.     

A maritime inventory routing problem with stochastic sailing and port times

This paper describes a stochastic short sea shipping problem where a company is responsible for both the distribution of oil products between islands and the inventory management of those products at consumption storage tanks located at ports. In general, ship routing and scheduling is associated with uncertainty in weather conditions and unpredictable waiting times at ports. In this work, both sailing times and port times are considered to be stochastic parameters. A two-stage stochastic programming model with recourse is presented where the first stage consists of routing, loading and unloading decisions, and the second stage consists of scheduling and inventory decisions. The model is solved using a decomposition approach similar to an L-shaped algorithm where optimality cuts are added dynamically, and this solution process is embedded within the sample average approximation method. A computational study based on real-world instances is presented.     

A study on inventory replenishment policies in a two-echelon supply chain system

Inventory control plays an important role in supply chain management. Properly controlled inventory can satisfy customers’ demands, smooth the production plans, and reduce the operation costs; yet failing to budget the inventory expenses may lead to serious consequences. The bullwhip effect, observed in many supply chain management cases, causes excessive inventory due to information distortion, i.e. the order amount is exaggerated while a minor demand variation occurs, and the information amplified dramatically as the supply chain moves to the upstream. In this paper, one of the main causes of bullwhip effect, order batching, is considered. A simplified two-echelon supply chain system, with one supplier and one retailer that can choose different replenishment policies, is used as a demonstration. Two types of inventory replenishment methods are considered: the traditional methods (the event-triggered and the time-triggered ordering policies), and the statistical process control (SPC) based replenishment method. The results show that the latter outperforms the traditional method in the categories of inventory variation, and in the number of backlog when the fill-rate of the prior model is set to be 99%. This research provides a different approach to inventory cost-down other than the common methods like: information sharing, order batch cutting, and lead time reduction. By choosing a suitable replenishment policy, the number of backorder and the cost of inventory can be reduced.     

Exploring the design space of robots: Children''s perspectives

Children's perceptions and evaluations of different robot designs are an important unexplored area within robotics research considering that many robots are specifically designed for children. To examine children's feelings and attitudes towards robots, a large sample of children (N = 159) evaluated 40 robot images by completing a questionnaire for each image, which enquired about robot appearance, robot personality dimensions and robot emotions. Results showed that depending on a robot's appearance children clearly distinguished robots in terms of their intentions (i.e. friendly vs. unfriendly), their capability to understand, and their emotional expression. Results of a principal components analysis of the children's ratings of the robots' personality attributes revealed two dimensions labelled ‘Behavioural Intention’ and ‘Emotional Expression’. Robots were classified according to their scores on these two dimensions and a content analysis of their appearance was conducted in an attempt to identify salient features of different robot personalities. Children judged human-like robots as aggressive, but human–machine robots as friendly. Results on children's perceptions of the robots' behavioural intentions provided tentative empirical support for the Uncanny Valley, hypothesized by (Mori, M., 1970), reflecting a situation where robots are very human-like, but still distinguishable from humans, evoking a feeling of discomfort or repulsion. The paper concludes with a discussion of design implications for robots, and the use of robots in educational contexts.     

横向整合战略下异质车辆库存路径优化模型

以实现供货商联盟期望物流成本最小化为目标,针对需求随机波动下的多供货商多产品库存路径问题（IRP）进行了研究。基于横向整合战略,设计了供货商联盟成员间车辆配送成本的合理分摊方式。考虑零售商配送软硬时间窗和库存服务水平要求,构建了多供货商多产品的异质车辆库存路径混合整数随机规划模型,并利用需求累积分布逆函数将其转化为确定型规划模型。然后设计改进遗传算法求解该确定型规划模型。算例分析结果显示,使用异质车辆配送可以比使用同质重型和轻型车辆分别降低供货商联盟总成本8.3%和11.92%,分别提升配送车辆装载率24%和17%。敏感性分析结果表明,无论供货商供货数量占联盟总供货数量比例和零售商商品需求变异系数如何变化,采用异质车辆配送的供货商联盟总成本都能得到有效降低;且需求变异系数越大,采用异质车辆配送的优势越明显。     

Using self-organizing maps to model turnover of sales agents in a call center

This paper proposes an approach for modeling employee turnover in a call center using the versatility of supervised self-organizing maps. Two main distinct problems exist for the modeling employee turnover: first, to predict the employee turnover at a given point in the sales agent's trial period, and second to analyze the turnover behavior under different performance scenarios by using psychometric information about the sales agents. Identifying subjects susceptible to not performing well early on, or identifying personality traits in an individual that does not fit with the work style is essential to the call center industry, particularly when this industry suffers from high employee turnover rates. Self-organizing maps can model non-linear relations between different attributes and ultimately find conditions between an individual's performance and personality attributes that make him more predisposed to not remain long in an organization. Unlike other models that only consider performance attributes, this work successfully uses psychometric information that describes a sales agent's personality, which enables a better performance in predicting turnover and analyzing potential personality profiles that can identify agents with better prospects of a successful career in a call center. The application of our model is illustrated and real data are analyzed from an outbound call center.     

The influence of depression and personality on social networking

Established literature supports the notion that depressed individuals tend to be socially maladjusted and behave differently from those who aren't depressed. Yet, previous studies seem to overlook the influence of personality on behavior. Particularly, neuroticism may moderate the effect of depression on the way people behave. As one of the Big-Five factors of personality, neuroticism refers to a trait of one's capability to control emotional distress. Based on behavioral data from 393 Facebook users, current research demonstrates the interaction between depression and personality. Users engaged in activities at different levels of activities corresponding to their depression levels. Further, the effect of depression on social networking was regulated by personality: once neuroticism exceeded certain points, an increase in depression led to a decrease in social networking activities.     

The effects of need for cognition on Internet use

One of the undisputed roles of the Internet is information spreading. However, to this day there is little understanding of the interaction between the way in which information is provided on the Internet and the behavior of different human personality types. This article focuses on the impact of the need for cognition on the desired level of interactivity of a given Website and on web surfing in general. For this experiment, four commercialized Websites were used: (1) flat with no hyperlinks and no time pressure; (2) flat with time pressure; (3) interactive¹ with no time pressure; and (4) interactive with time pressure. All of the Websites contained identical information presented in different ways. The relations between need for cognition as a personality variable, time pressure as a situational stressor, the interactivity of the Web site, and several demographic variables were examined on Internet users’ behavior while surfing and on their preferences. One hundred and eighty-two experienced Web surfers took part in the experiment and were randomly assigned to one of the Websites. The number of hyperlinks used while surfing were counted by specially designed software. After surfing, the participants completed questionnaires regarding their satisfaction from the site, their willingness to return to the site, how persuasive the site was, and demographic data. It was predicted that people with high need for cognition would be more experienced in the Internet, use more hyperlinks, and stay longer in the site. People with a low need for cognition were predicted to prefer interactive over linear sites. Results support the preferences of people low in need for cognition of an interactive site. Other predictions were supported only partially. Implementations for Website design and further research are discussed.     

Electronic diary evidence on energy erosion in clinical burnout.

Burnout is generally defined as a state of severe exhaustion. So far, research has predominantly focused on relatively mild burnout in employees able to work despite their complaints. This study examines energy depletion in clinical burnout (e.g., the severest cases on extended sick leave) by comparing the diurnal patterns of fatigue and exhaustion with those of healthy individuals. Sixty clinically burned-out and 40 healthy participants kept an electronic diary for 14 days, 7 times a day, yielding a total of 8,116 diary entries. This study shows that burned-out individuals typically suffer continuously from a severe fatigue throughout the day. The resulting flattened diurnal cycles mark a stable exhaustion that is uncommon in healthy persons. The current results provide novel support for the existence of severe energy erosion in clinical burnout. (PsycINFO Database Record (c) 2010 APA, all rights reserved)