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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Korean Institute of Industrial Engineers
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Korean Institute of Industrial Engineers
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Volume & Issues
Volume 29, Issue 4 - Dec 2003
Volume 29, Issue 3 - Sep 2003
Volume 29, Issue 2 - Jun 2003
Volume 29, Issue 1 - Mar 2003
Selecting the target year
Multivariate Process Capability Indices for Skewed Populations with Weighted Standard Deviations
Jang, Young Soon ; Bai, Do Sun ;
Journal of Korean Institute of Industrial Engineers, volume 29, issue 2, 2003, Pages 114~125
This paper proposes multivariate process capability indices (PCIs) for skewed populations using
rand modified process region approaches. The proposed methods are based on the multivariate version of a weighted standard deviation method which adjusts the variance-covariance matrix of quality characteristics and approximates the probability density function using several multivariate Journal distributions with the adjusted variance-covariance matrix. Performance of the proposed PCIs is investigated using Monte Carlo simulation, and finite sample properties of the estimators are studied by means of relative bias and mean square error.
Investigation of the Structure of the Strategic Net Present Value and Its Economic Interpretation through the Opportunity Cost Concept
Kim, Gyutai ; Choi, Sungho ;
Journal of Korean Institute of Industrial Engineers, volume 29, issue 2, 2003, Pages 126~134
Among a variety of models proposed by so far to calculate the real options value when the investment decision about the underlying project may be delayed, the Black-Scholes and the binomial lattice models have been widely used and discussed by academics and practitioners. However these two models do not provide us with intuition into how it is constructed and what it does really mean. In this paper, we will therefore explore its components and practically more intuitive meaning. With the components explored, we developed the mathematical model to calculate the real options value and thus strategic net present value, based on the opportunity cost concept, for which the investment decision about the underlying project is postponed by one year. We will finally present a short illustrative example for readers better understanding on the model proposed in the paper.
Traffic Modeling and Analysis for Pedestrians in Picocell Systems Using Random Walk Model
Lee, Ki-Dong ; Chang, Kun-Nyeong ; Kim, Sehun ;
Journal of Korean Institute of Industrial Engineers, volume 29, issue 2, 2003, Pages 135~144
Traffic performance in a microcellular system is much more affected by cell dwell time and channel holding time in each cell. Cell dwell time of a call is characterized by its mobility pattern, i.e., stochastic changes of moving speed and direction. Cell dwell time provides important information for other analyses on traffic performance such as channel holding time, handover rate, and the average number of handovers per call. In the next generation mobile communication system, the cell size is expected to be much smaller than that of current one to accommodate the increase of user demand and to achieve high bandwidth utilization. As the cell size gets small, traffic performance is much more affected by variable mobility of users, especially by that of pedestrians. In previous work, analytical models are based on simple probability models. They provide sufficient accuracy in a simple second-generation cellular system. However, the role of them is becoming invalid in a picocellular environment where there are rapid change of network traffic conditions and highly random mobility of pedestrians. Unlike in previous work, we propose an improved probability model evolved from so-called Random walk model in order to mathematically formulate variable mobility of pedestrians and analyze the traffic performance. With our model, we can figure out variable characteristics of pedestrian mobility with stochastic correlation. The above-mentioned traffic performance measures are analyzed using our model.
Estimation of Failure Rate and Acceleration Factor in Accelerated Life Testing under Type-I Censoring
Kong, Myung Bock ; Park, Il Gwang ;
Journal of Korean Institute of Industrial Engineers, volume 29, issue 2, 2003, Pages 145~149
We consider the estimation of failure rate and acceleration factor under type-I censoring without using acceleration model when testing is conducted in only one highly accelerated condition. Failure times of an item are assumed to be exponentially distributed. It is also assumed that the uncertainty about the acceleration factor, the failure time contraction ratio between accelerated condition and use condition, can be modeled by the uniform or gamma prior distribution of appropriate parameters. We respectively use Bayes and maximum likelihood approaches to estimate acceleration factor and failure rate in the use condition. An example is given to show how the method can be applied.
Downlink-First Scheduling of Real-Time Voice Traffic in IEEE 802.11 Wireless LANs
Jeong, Dong W. ; Lee, Chae Y. ;
Journal of Korean Institute of Industrial Engineers, volume 29, issue 2, 2003, Pages 150~156
The IEEE 802.11 MAC (Media Access Control) Protocol supports two modes of operation, a random access mode for nonreal-time data applications processed by Distributed Coordinated Function (DCF), and a polling mode for real-time applications served by Point Coordinated Function (PCF). It is known that the standard IEEE 802.11 is insufficient to serve real-time traffic. To provide Quality of Service (QoS) of real-time traffic, we propose the Downlink-first scheduling with Earliest Due Date (EDD) in Contention Free Period (CFP) with suitable admission control. The capacity and deadline violation probability of the proposed system is analyzed and compared to the standard pair system of downlink and uplink. Analytical and simulation results show that the proposed scheme is remarkably efficient in view of the deadline violation probability.
Engineering Change of Products Using Workflow Management Based on the Parameters Network
Yang, Jeongsam ; Goltz, Michael ; Han, Soonhung ;
Journal of Korean Institute of Industrial Engineers, volume 29, issue 2, 2003, Pages 157~164
The amount of information increases rapidly when working in a distributed environment where multiple collaborative partners work together on a complex product. Today's PDM (product data management) systems provide good capabilities regarding the management of product data within a single company. However, taking into account the variety of systems used at partner sites in an engineering environment one can easily imagine problems regarding the interoperability and the data consistency. This paper presents a concept to improve the workflow management using the parameters network. It shows a parameter driven engineering workflow that is able to manage engineering task across company boarders. We introduce a mechanism of workflow management based on the engineering parameters and an architecture of the distributed workspace to apply it within a PDM system. For a parameter mapping between CAD and PDM system we developed an XML-based CATIA data interface module using CAA.
Visual Search Models for Multiple Targets and Optimal Stopping Time
Hong, Seung-Kweon ; Park, Seikwon ; Ryu, Seung Wan ;
Journal of Korean Institute of Industrial Engineers, volume 29, issue 2, 2003, Pages 165~171
Visual search in an unstructured search field is a fruitful research area for computational modeling. Search models that describe relationship between search time and probability of target detection have been used for prediction of human search performance and provision of ideal goals for search training. Until recently, however, most of models were focused on detecting a single target in a search field, although, in practice, a search field includes multiple targets and search models for multiple targets may differ from search models for a single target. This study proposed a random search model for multiple targets, generalizing a random search model for a single target which is the most typical search model. To test this model, human search data were collected and compared with the model. This model well predicted human performance in visual search for multiple targets. This paper also proposed how to determine optimal stopping time in multiple-target search.
Determining the Number and the Locations of RBF Centers Using Enhanced K-Medoids Clustering and Bi-Section Search Method
Lee, Daewon ; Lee, Jaewook ;
Journal of Korean Institute of Industrial Engineers, volume 29, issue 2, 2003, Pages 172~178
In the recent researches, a variety of ways for determining the locations of RBF centers have been proposed assuming that the number of RBF centers is known. But they have also many numerical drawbacks. We propose a new method to overcome such drawbacks. The strength of our method is to determine the locations and the number of RBF centers at the same time without any assumption about the number of RBF centers. The proposed method consists of two phases. The first phase is to determine the number and the locations of RBF centers using bi-section search method and enhanced k-medoids clustering which overcomes drawbacks of clustering algorithm. In the second phase, network weights are computed and the design of RBF network is completed. This new method is applied to several benchmark data sets. Benchmark results show that the proposed method is competitive with the previously reported approaches for center selection.
Statistical Design of Experiments and Analysis: Hierarchical Variance Components and Wafer-Level Uniformity on Gate Poly-Silicon Critical Dimension
Park, Sung-min ; Kim, Byeong-yun ; Lee, Jeong-in ;
Journal of Korean Institute of Industrial Engineers, volume 29, issue 2, 2003, Pages 179~189
Gate poly-silicon critical dimension is a prime characteristic of a metal-oxide-semiconductor field effect transistor. It is important to achieve the uniformity of gate poly-silicon critical dimension in order that a semiconductor device has acceptable electrical test characteristics as well as a semiconductor wafer fabrication process has a competitive net-die-per-wafer yield. However, on gate poly-silicon critical dimension, the complexity associated with a semiconductor wafer fabrication process entails hierarchical variance components according to run-to-run, wafer-to-wafer and even die-to-die production unit changes. Specifically, estimates of the hierarchical variance components are required not only for disclosing dominant sources of the variation but also for testing the wafer-level uniformity. In this paper, two experimental designs, a two-stage nested design and a randomized complete block design are considered in order to estimate the hierarchical variance components. Since gate poly-silicon critical dimensions are collected from fixed die positions within wafers, a factor representing die positions can be regarded as fixed in linear statistical models for the designs. In this context, the two-stage nested design also checks the wafer-level uniformity taking all sampled runs into account. In more detail, using variance estimates derived from randomized complete block designs, Duncan's multiple range test examines the wafer-level uniformity for each run. Consequently, a framework presented in this study could provide guidelines to practitioners on estimating the hierarchical variance components and testing the wafer-level uniformity in parallel for any characteristics concerned in semiconductor wafer fabrication processes. Statistical analysis is illustrated for an experimental dataset from a real pilot semiconductor wafer fabrication process.