• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.38 no.3
• /
• pp.8-13
• /
• 2015

One of the most usual indicators to measure the performance of any inventory policy is the mean physical stock. In general, when estimating the mean physical stock in periodic review inventory systems, approximate approaches are often utilized by practitioners and researchers. The mean physical stock is generally calculated by a simple approximation. Still these simple methods are frequently used to analyze various single stockpoint and multi-echelon inventory systems. However, such a simple approximation can be very inaccurate. This is particularly true for low service levels. Even though exact methods to calculate the mean physical stock have been derived, they are available for specific cases only and computationally not very efficient, and therefore less useful in practice. In literature, approximate approaches, such as the simple, the linear, and Simpson approximations, were derived for the periodic review inventory systems that allow backorders. This paper modifies the approximate approaches for the lost sales case and evaluates the modified approximate approaches. Through computational experiments, average (and maximum) percentage deviations of mean physical stock between the exact method and the modified approximations are compared in the periodic review inventory system with lost sales. The same comparison between the modified and the original approximations are also conducted, in order to examine the performance of modified approximations. The results show that all modified approximations perform well for high service levels, but also that the performance may deteriorate fast with decreasing service level. The modified Simpson approximation is clearly better. In addition, the comparison between the modified and the original approximations in the periodic review inventory system with lost sales shows that the modified approximation outperforms the original approximation.

• Korean Management Science Review
• /
• v.19 no.1
• /
• pp.107-116
• /
• 2002

A major challenge to supply chain managers is how to control inventories and costs along the supply chain while maximizing customer service Performance. In the literature, although the optimal management of inventory along the supply chain has received considerable attention during the past decades, the attention has been mainly given to multi-echelon control policies. A prerequisite for applying these policies is full information transparency in the supply chain, which is hard to accomplish in practice because it may require major organizational chanties. In the case that a decentralized control (local (R, S) policy) should be used at each location in multi-stave distribution systems, this paper presents the coordinating approach of determining the best policy which satisfies predetermined target customer service levels and minimizes the mean physical stock along the system.

• Journal of Industrial Convergence
• /
• v.1 no.1
• /
• pp.143-157
• /
• 2003

This paper examines the changed consumer perception to internet based channel. Internet based channel has time merit, place merit, assortment merit, compatibility merit, and so on. For seller, in the mean while, it has merits in the way of diminishing physical distribution cost, promotion cost, and reaching globally in the same time. In spite of so many merits of internet based channel, there were many types complain in past. Most of all, consumers expect that it will provide low-price merit to consumer, because it doesn't need shop, warehouse, stock, etc. Based on the empirical analyses in past, it didn't work, especially to price oriented consumer's perception. But in this research, it shows changing consumer's perception. Comparing past data with current data, we found outstanding gross in price related variables figure. But, in goods delivery related factors and personal credit information related factor, consumer recognized much more negatively yet. So, we conclude that even though some factors show improved perception, there are tasks to solve. We will observe the tuning point at that time.

• Korean Journal of Agricultural Science
• /
• v.10 no.1
• /
• pp.9-21
• /
• 1983

The structures of oak stands were studied in relation to their productivity. Three plots classified by the site quality following to altitude, were selected on the oak stand located at Naryongri Eunsanmyun Buyeogun. The site qualities of the stand studied were generally estimated to be moderate in respect to some soil physical and chemical properties. Quercus variabilis was dominant species in the vegetation composition of the stand studied. The crown densities of the stand were varied from 65.4% in plot I to 78.2% in plot III and the parts, occupied with oak trees, ranged from 44.4% in plot I to 65.9% in plot III in the density. In the contrast to crown density, the growing stocks of oak trees ranged from $3.937m^3$ in plot I (73.4% of plot total) to $2.075m^3$ in plot III (84.3% of plot total). The occupied ratios, measured by crown class, exhibited dissimilarity between crown projection area and volume, and also the ratios brought into different patterns by plot. Highly significant correlations were proved between crown projection areas and volumes of individual oak trees by plot, but not proved in the relations by crown class. The cumulative growth, current annual increment and mean annual increment displayed various patterns by plot and by crown class in the heights, D. B. H. s and volumes of oak trees. The maximum values of current annual increment of height were generally recorded in 10 to 20 years, earlier than those of D. B. H. The mean annual increment of height, D. B. H. and volume maintained similar levels after about 10 years and fluctuated irregularly. The crown projection area and volume following to thinning decreased in the order of the thinning methods of grade A < grade B < crown thinning$90m^3/ha$ in about 40 years in the productivity of volume of the oak stand studied.