Due to the intensified price competition in an era of slow growth, cost management focusing on marginal income dealing with a single variable cost is becoming inadequate. It is necessary to rapidly grasp the changes in product cost and earnings as they correspond to changes in the market. This research proposes a method of cost management for understanding such changes structurally and in detail.  In the method, a set of activities called "transactions" is identified in a process model where the costs of materials, equipment and others are measured for each activity. The process model is converted into a cost structure matrix to clarify how to calculate the product cost and earnings when market changes are given. This method provides a cost management model that enables quantitative grounds for decision-making

View full abstract

Visual inspection is one way to ensure product quality, and although automated visual inspection has been introduced, it is costly and associated with technical issues. Thus, human visual inspection still plays a major role in visual inspection in the industry. Many studies have focused on the visual fatigue of the inspectors. However, upper limb load caused by handling objects and maintaining a specific posture is also considered a problem in visual inspection. If the inspection object is lightweight but large in size (e.g., a plastic part), the inspectors tend to maintain an awkward posture due to difficulty in handling the object. Despite these findings, few studies have elucidated the effect of upper limb load. In this study, we intended to assess the effect of inspection side and object size on upper limb load. Ten healthy male subjects were instructed to inspect objects using a combination of six inspection side conditions (i.e., the sides of front with horizontal LED, top, under, front with vertical LED, right, and left) and two object size conditions (i.e., big: a square, 450 mm each side, and small: a square, 150 mm each side). Muscle activity and joint moment were the evaluation indices. We also investigated subjective indices for burden and task difficulty. Electromyography was performed on the subjects' sternomastoid muscle, the upper part of the trapezius, the clavicular part of the pectoralis major, the middle part of the deltoid, the biceps brachii, the extensor carpi radialis, and the flexor carpi ulnaris muscle. The results showed that the muscle load of the upper limb is highest when the inspection side condition is under side. Additionally, if the object is big, the muscle load of the neck and upper limb is greater.

View full abstract

The bullwhip effect is an important phenomenon of supply chains where the demand fluctuations are amplified as they go up the supply chain. In some previous studies, it has been reported that sharing the final demand information among the participants of the supply chain is effective for suppressing the demand fluctuation amplifications. In many actual supply chains, however, there are not always capital relationships among all the participants. In such a case, it is difficult for the participants to share the final demand information, which is because the rule of profit distribution has not been established. In this paper, a new supply chain model is proposed that realizes the sharing of demand information in a different way. In this model, each participant provides the final demand information for the next participant along with its order information. Consequently, the final demand information can be relayed to every upstream participant in the supply chain although communication delays arise. Since there are business connections among each adjoining participant, it is considered to be easily realizable for each participant to transmit the final demand information along with its order information. Mathematical formulation and numerical simulations show that the proposed model suppresses the bullwhip effect despite sharing the delayed information, unlike the non-information-sharing model.

View full abstract

In most studies dealing with inventory problems, lead time is treated as fixed. However, in several practical situations, the lead time can be reduced at an added cost, which is called a “crashing cost”. By shortening the lead time, we can lower the safety stock, save inventory space, reduce the stock-out loss, and improve the customer service level. In fact, there are some studies that consider lead time reduction. Pan et al. (2002) proposed the crashing cost, which is assumed to be a function of both the order quantity and the reduced lead time. Ouyang et al. (2001) and Lee (2005) proposed the backorder rate, which is assumed to be dependent on the amount of shortages. There are no inventory models that consider both crashing cost in the Pan et al. (2002) and backorder rate in the Lee (2005). In this paper, we present an inventory model in which the order quantity, reorder point, and lead time are regarded as decision variables. The crashing cost is represented as a function of both the reduced lead time and the order quantity, and the backorder rate is assumed to be dependent on the amount of shortages. We develop an algorithm to find near optimal solutions and give numerical examples to demonstrate the effectiveness of our proposed model. Furthermore, a sensitivity analysis is also conducted to identify situations where shortening lead time is valuable.

View full abstract

Recently, the recommender system which automatically recommends product items for customers has become more important as an efficient web marketing tool. In many electronic commerce (EC) sites, the data of customers' purchases and evaluation histories are stored in a database. By using them, the system predicts user's preferences, and automatically recommends items that seem to be preferred, but have not been purchased yet. In this study, we focus on the recommender system based on collaborative filtering (CF) with a latent class model. CF recommends items by using purchase or evaluation history data. Considering real purchase activity on EC sites, most of the consumers who bought items on an EC site don't post their evaluation on the site. That means more purchase history data is stored more in the database than evaluation history data. However, most studies of CF used only evaluation data to learn the model. In this case, the purchase data is not used to construct a model even though its data size is much larger than that of evaluation history. It is more desirable to learn a model by using not only evaluation history, but also purchase data to improve the CF accuracy. The purpose of this study is to construct an effective CF model to improve the CF accuracy by formulating the estimation using both evaluation history data and abundant purchase history data which has not been used in previous CF studies. Specifically, we use the aspect model, which is one of latent class models of CF. We propose a way to estimate its parameters using both evaluation history and purchase data. To verify the effectiveness of this study, a simulation experiment was conducted using a bench mark data of recommender system. We show that the prediction accuracy of the recommendation is improved.

View full abstract

The control and maintenance of inventories are vital for many companies because the effective management of inventories can provide better customer service and improve profitability. In recent years, the number of different stock keeping units (SKUs) that must be delivered is exploding. Meanwhile, due to the spread of the electronic commerce, filling customer orders within a 24-hour period is becoming the new standard in many industries, which means that an increasing number of SKUs has to be delivered more frequently and faster. We consider a warehouse configured with a forward area, where items are stored in cases for easy retrieval by an order picker, and a reserve area, where items are stored by the case for picking and replenishing stocks in the forward area. Based on real data, this paper studies the setting of order-up-to level and reorder level in (s,S) policy and determining the proper maintenance intervals (PMIs) in order to reduce stockouts and excessive stock in a distribution center. Order-up-to and reorder levels should be decided after comprehending the trade-off between inventory space and emergency replenishment. Furthermore, we show maintenance at PMIs can lead to cost savings. Such improvements would allow the distribution center to reduce stock-outs and excessive stock, and to increase productivity.

View full abstract

Medical safety is one of the most important and basic concerns of medical services. For instance, in clinical hemodialysis, medical staff are expected to notice problems or abnormalities when the patient is undergoing medical treatment, such as falling blood pressure, and to deal with any abnormality appropriately. Experienced medical staff are able to promptly notice an abnormality and take appropriate countermeasures quickly, and they can provide safe service. Such actions are, however, based on specific knowledge obtained through their long-time experiences, and such knowledge seems sometimes like being held in a black-box as know-how. This becomes one of the educational problems of novice staff during hemodialysis treatment.  Therefore, for the sake of educating novice staff, this study focused on the process of taking judgments which are difficult for novices and clarifying the points for which novices should be trained. By clarifying the reason why these judgments are difficult for novices, this study also revealed the training items for novice staff as related to their judgments during hemodialysis treatment. These training items show the insufficient skills of novices. Experts of hemodialysis treatment, who work in a certain university hospital, evaluated these items to be useful for education. This approach diminishes the skill gap between experts and novices. Therefore, we believe it is applicable in a variety of service sites with educational problems similar to those in the case of hemodialysis treatment.

View full abstract

Some issues regarding the procurement of information systems including software have been pointed out from the buyer's viewpoint. The purpose of this research is to provide a series of techniques for buyers to select functions and outsourcing system development. The proposed techniques are effective for organizing and visualizing information on system requirements with weighted importance, technical specifications of software, and cost for software development. In addition to the above, the ordering value, derived from fulfillment and weighted importance, are helpful for buyers to make cost-effective decisions to develop software function sets. We apply the proposed techniques to a case study of technical service support software in the wireless communications industry in order to evaluate their effectiveness. The results show the advantage of treating the weighted importance taking into account timeliness for functional availability and visualizing fulfillment of the buyer's requirements.

View full abstract