In field activities such as assembling and packaging workers often use their hands to push down on materials. This type of task requires the worker to expend a relatively great effort, consequently imposing unsafe levels of musculoskeletal load on the upper limbs. The assessment of downward pushing workload is limited due to the difficulty of measuring the internal forces exerted by the worker. Additionally, when the position of the object is changed, the body site experiencing the load may also change because of the alteration in working posture, such as bending of the body trunk and elevating the upper limbs. In the present study, we attempted to quantitatively evaluate the upper limb load during a downward pushing task performed using both hands. We asked 10 subjects to push down on a load-cell plane set vertically at a pressure of 150N. The following experimental parameters were selected: plane set at three heights (chest, lower back and knee) and three distances between the plane and body trunk (100, 75 and 50% of the forearm length). The pushing force, joint moment, electromyogram and subjective assessment were evaluated. The results show that the load on the shoulder and elbow increased with as the height of the load-cell plane increased. Conversely, when the height of the plane was decreased, the lumbar load increased, while the load on the upper limbs decreased. The results of this study provide useful information that may help in improving working postures and formulating work environments that impose less workload.

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Knowledge sharing is one of the most important factors in business collaboration for improved performance, efficiency and quality of business. Business knowledge can be divided into explicit knowledge and tacit knowledge. Most explicit knowledge is found in business documents such as regulations, manuals, reports and white papers. Tacit knowledge is acquired through business experiences. As such, experienced persons such as business leaders and experts are likely to have it. In order to share tacit knowledge with all the collaboration members, it is necessary to extract this tacit knowledge and translate it into explicit knowledge. However, this is not simple to achieve. We propose a method to acquire explicit knowledge regarding evaluating alternatives using actual cases where alternatives were evaluated by a tacit-knowledge holder. The evaluation is induced through preferences for the attribute values of the alternatives. We focus on pair-wised comparisons, which are a fundamental element of relative evaluation. The evaluation knowledge is represented as rules that give the order of preference for a pair of alternatives according to their attribute values. The rules are represented as a logic function of the ordinal relationship of preferences for the attribute values. The evaluation logic function can only be derived with sufficient evaluations by the knowledge holder. We then propose a method to induce sufficient and necessary conditions of the evaluation logic function, assuming the monotony of the preference logic function for each attribute preference. We also discuss how to induce conditions closer to those of the target logic function, assuming the total order or linear order of preference for the set of alternatives. The proposed method is applied to acquire rules for evaluating portable music players, and we discuss the performance of the acquired rules and this method.

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In field activities performed using a step stool, working postures often involve single-leg lifting. This study focuses on the activities performed using step stools and aims to evaluate the effects of the operational posture on postural stability and lower-limb loads during a step-stool task involving single-leg lifting. Specifically, the task was to move an object with the right hand while the right leg was raised on an upper step. Postural stability was assessed by determining the sway in the center of gravity and the floor reaction force. Lower-limb loads were assessed via electromyograms of eight muscles and a subjective scale. The subjects were 11 male university students. The experimental factors were: the direction in which the task was performed, and the height of the step. The different directions in which the task was performed were the center of the body, left side, and right side. The different step heights used in the study were 30cm, which is the height of a real step stool, and 5cm, which was used for examining the results obtained with or without a step. The results show that the posture on the left side is unstable, and the muscle load around the ankle is higher than that at the other sites. Furthermore, the posture at a height of 5cm is more stable than that at a height of 30cm. These results show that this study is useful in formulating guidelines for step-stool work; the guidelines would be based on the nature of the task and the features of the step stool.

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As products and component lifecycles are shortened and product lines become more diversified recently, many manufacturing industries have started to adopt the concepts of product platform and concurrent engineering. Companies are faced with the issues of provide product lines that meet market needs while shortening the product development process and reducing development costs. For concurrent engineering, it is essential to exchange information among relative departments and to visualize the cross-relationship of restrictions and concerns in the product design process. This study aims to visualize the functional design processes in product developments using the information such as designers' knowledge of product design in a case study on multi-product lines of vending machine. The research was conducted on a joint basis, working with universities and a vending machine manufacturer. Furthermore, applying IDEF0, functional design procedures and sequences are organized for vending machine product lines and methods are introduced to describe the processes undertaken to design main products and to generalize those procedures based on the descriptions of multi-product lines.

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Results-based production ordering systems (RBPOSs) are production ordering systems that only use the information from actual results, that is, from actual production, actual demand, and/or actual stock at inventory points between production processes. This paper reviews the abundant literature on RBPOSs, which include systems such as the Kanban, CONWIP, base stock, and drum-buffer-rope (DBR) systems. In addition to presenting models, analysis, improvements and applications, this paper presents possible future research topics.

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The purpose of this research is to develop a decision support system for selecting transportation mode in order to reduce CO_2 emissions. In Japan, the transportation sector accounts for approximately 20% of the total CO_2 emissions. In order to reduce the CO_2 emissions in logistics, modal shift has been promoted. However, modal shift is still not promoted sufficiently because of many problems in areas such as quality and delivery. This study develops a decision support system for selecting the transportation mode while considering these problems. Through use of this system, users can choose the appropriate transportation mode or combinations of modes on the basis of preferences and conditions.

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This paper studies the effect of lead-time decision on the performance of a decentralized supply chain that consists of one supplier, one retailer, and wherein the demand is sensitive to both retail price and lead-time. Three different scenarios based on lead-time decision making are studied and compared analytically and numerically. The lead-time is decided by the retailer and the supplier in the first and second scenarios, respectively, and it is centralized in the third scenario. The modeling considers holding and tardiness costs incurred by the difference between promised and realized delivery lead-times. The supply chain is analyzed using a power distribution function. This distribution is a parametric function that models the lead-time in general environment and has the same properties as exponential distribution for specific parameters. The optimal decision variables and expected profits are characterized and compared for the three scenarios. The relative decrease of total expected profits in the decentralized chains from that in the centralized model is observed and discussed. Furthermore, the effect of own price and lead-time sensitivity demand factors are studied numerically.

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This paper discusses the construction of a mathematical model and an optimization procedure for facility location problems in a two-stage logistics system consisting of a plant, distribution centers, and shops. The model is constructed to search for the optimal locations of the distribution centers. The goal is to minimize the total distance between plants and distribution centers and between distribution centers and shops considering the demand distribution and restricted inventory capacity at the distribution centers. In addition, the model includes logistic constraints based on the demand distribution. A genetic algorithm is developed to solve the problem. The algorithm is used in a two-step procedure that modifies the grid to search for the optimal locations of the distribution centers within a reasonable computation time. The algorithm is demonstrated on a simple example to investigate its performance and the effect of grid modification.

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Supply chain contracts involve determining values for both producer and supplier sides. Either party often tends to optimize its own benefits under competitive circumstances. In the process of production, it usually involves the procurement of materials from suppliers who are located in different countries. Thus, not only the uncertainty factor in demand, but also the uncertainty in exchange rates affect the value of the contract. A flexible supply contract is preferred by the producer, regardless of the inflexible production on the supplier side. In this research, we analyze the value of procurement contracts with regard to uncertainty in demand and prices that are associated with the foreign exchange rate. The mean reversion process is assumed to replicate the dynamics of the exchange rate and is usually analyzed using a multinomial approach. This method, combined with traditional dynamic programming, makes the problem computationally infeasible even for a small number of variables and a small number of states. We propose to solve the problem using the approximation dynamic programming method. This method is effective for handling stochastic dynamic programming problems that have a large number of states. We show that the problem converges and the optimal order quantity under uncertainty can be obtained, thereby increasing the value of the contract.

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