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Reuse of product components is an effective way to conserve natural resources. Likewise, remanufacturing is a new trend in the field of environmentally friendly products. A product undergoes functional failure or physical failure in a remanufacturing environment, where the former failure is equivalent to the state in which the product cannot be used because of functional insufficiency or obsolescence and the latter failure is equivalent to the state of malfunction or breakdown of a product. A unit intended for reuse should be designed to be durable for a period equal to at least two functional lives through remanufacturing. Utilization of excess materials-for example, for improvement of unit strength-can enable a reusable unit to endure over a period equal to at least two functional lives. However, if the environmental impact of such excessive use of materials is taken into account, a strong doubt arises as to whether such a method truly reduces the environmental load from the viewpoint of lifecycle design. In order to analyse this issue, the present study examines the optimal physical life span of a reusable unit and its effect on the environment. A mathematical model of a remanufacturing system is constructed, taking into account functional and physical failures of a product. A minimization problem of the incurred total environmental impact per unit time for a reusable unit is formulated under the decision variables of a design parameter vector of the unit and the maximum number of times of reuse. The design parameter vector is closely related with physical life span. The maximum number of times of reuse can cause environmental loss if a product has a long residual physical life span brought on by the small number of times of reuse. The effects of physical life span of a reusable unit on environmental impact are analysed to show the potential value of the developed model by means of varying stochastic characteristics and the parameters of the remanufacturing environment.

Assembly errors can occur in a robotic assembly system. In this paper, a method that predicts an assembly error is proposed. It considers that assembly errors occur under the condition that the geometric trajectory of a mated part and the relational position and orientation of a base part are outside the allowable tolerance. A certain point, which is determined by using a physical light reflectance model of a mated part, is followed with two high-speed cameras. A statistical pattern recognition method in which explanatory variables are tracked points in a three-dimensional space is then employed to predict an assembly error. The proposed method is applied to a peg-in-a-hole assembly by a selective compliance assembly robot arm (SCARA)-type robot and its potential value is discussed.

This paper which consists of Parts I and II presents a general and practical fluid lubrication theory of roller bearings lubricated by Newtonian and non-Newtonian lubricants with considerations to the effect of sliding of roller and the influence of unsteady load. In Part I, the fundamental theory for the lubrication between two rotating cylinders in contact has been investigated. The load capacity and friction of a non-Newtonian lubricant, supposed to be a Bingham plastic, coincide approximately at high speed with those of a Newtonian lubricant with viscosity equivalent to the plastic viscosity of the non-Newtonian lubricant. Under unsteady loads, the squeeze action works effectively so that the load capacity increases. The amount of friction is 4/3 and the load capacity is 2/3 in the case of two rotating cylinders in contact involving sliding, compared with that involving no sliding.

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