Machines and facilities are physically or chemically degenerated by continuous usage. One of the results of this degeneration is the process mean shift. The representative type of the degeneration is wear of tool or machine. According to the increasing wear level, non-conforming products cost and quality loss cost are increasing simultaneously. Therefore a periodic preventive resetting the process is necessary. The total cost consists of three items: adjustment cost (or replacement cost), non-conforming cost due to product out of upper or lower limit specification, and quality loss cost due to difference from the process target value and the product characteristic value among the conforming products. In this case, the problem of determining the adjustment period or wear limit that minimizes the total cost is called the ‘process mean shift’ problem. It is assumed that both specifications are set and the wear level can be observed directly . In this study, we propose a new model integrating the quality loss cost, process variance, and production volume, which has been conducted in different fields in previous studies. In particular, for the change in production volume according to the increasing in wear level, we propose a generalized production quantity function g(w). This function can be applied to most processes and we fitted the g(w) to the model. The objective equation of this model is the total cost per unit wear, and the determining variables are the wear limit and initial process setting position that minimize the objective equation.

PURPOSES : The purpose of this study is to analyze the improvement effect of the distributed arrangement of a vehicle base, which is a policy on maximizing the cost efficiency and timely/spatial effectiveness of special transportation system (STS) operation for improving the mobility of the elderly and disabled. METHODS: (1) The characteristics of the current distributed arrangement of an STS vehicle base in an urban area was analyzed. (2) The quantitative improvement effect was derived by analyzing the actual measurement of operation during STS distributed arrangement test operation in Namyangju city. RESULTS : (1) Cities with large area and populations, which have a distributed living zone in an urban area, have a higher distributed arrangement ratio than urbanized smaller cities. (2) Based on the effectiveness analysis of the STS distributed arrangement test operation, the total travel time and distance decreased. CONCLUSIONS : (1) For the STS distributed arrangement, parking spots, driver standby, and restrooms must be prepared. Facilitating STS as a public institution consignment makes it easier to secure a vehicle base and management by utilizing public facilities. (2) Implementing the STS distributed arrangement of vehicle base allows for efficient response to demand through effective management of vehicles, which eventually decreases travel time and distance. This decrease not only reduces management costs but also increases supply expansion without an increase in the number of vehicles.

Elemental mercury has a very high volatility allowing easy dissipation from water or soil into air. To better understand how the kinetics of diffusion of elemental mercury through a medium, which is soil in this study, a mercury diffusion column experiment was done. The correlation between temperature and equilibrium concentrations of mercury in standardized soil samples and a pure mercury standard were determined. Total mercury concentrations were analysed using CVAFS. The effect of time and soil depth to the kinetics of mercury diffusion were determined. Differences in mercury concentrations at different sampling probes were observed during the first few gas phase analyses. Equilibrium was reached through the column after 72 hours.