• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.11
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• pp.30-36
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• 2010

In recent memories, repair is an unavoidable method to maintain its yield and quality. Although many word oriented memories as well as embedded memories in system-on-chip (SOC) consists of multiple local memory blocks with a global spare architecture, most of previous studies on built-in redundancy analysis (BIRA) algorithms have focused on single memory block with a local spare architecture. In this paper, a new BIRA algorithm for multiple blocks with a global spare architecture is proposed. The proposed BIRA is basd on CRESTA which is able to achieve optimal repair rate with almost zero analysis time. In the proposed BIRA, all repair solutions for local memory blocks are analyzed by local analyzers which belong to each local memory block and then compared sequentially and judged whether each solution can meet the limitation of the global spare architecture or not. Experimental results show that the proposed BIRA achieves much faster analysis speed compared to previous BIRAs with an optimal repair rate.

• Journal of Applied Reliability
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• v.16 no.4
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• pp.295-304
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• 2016

Purpose: This paper presents an application of Markov Process to reliability and availability analysis. In order to do that of analysis, we set up a specific case of Tablet PC and it's usage scenario. The case has it some spares and maintenance and repair processes. Methods: Different configurations of the tablet PC and as well as their functions are defined. The system configuration and calculated failure rates of components are modeled from Windchill Quality Solution. Two models, without a spare and with spare, are created and compared using Markov Process. The Matlab numerical analysis is used to simulate and show the change of state with time. Availability of the system is computed by determining the time the system stays in different states. Results: The mission availability and steady-state condition availability in accordance with the mission are compared and the availability of the system with spares have improved availability than without spares. Simulated data shows that downtime of the system increased which results in greater availability through the consideration of spares. Conclusion: There's many techniques and methods to do reliability and availability analysis and mostly are time-independent assumptions. But Markov Process, even though its steady-state and ergodic properties, can do time analysis any given time periods.

• Journal of the Korean Society of Safety
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• v.23 no.4
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• pp.90-98
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• 2008

Presently, pedestrian's signal time models in korea are not considering Vulnerable-Pedestrian. So, the safety of Vulnerable-Pedestrian is being threatener and the number of accidents is increasing. Besides, the existing operational system for pedestrians can't offer the cross signal time in road corresponded the changing environment when the school zone is revitalized and the Silver zone is introduced for Vulnerable-Pedestrian. Conclusively, Vulnerable-Pedestrian's signal time models which are able to consider classified Vulnerable-Pedestrian speed, Vulnerable-Pedestrian perception-reaction time, Vulnerable-Pedestrian Spare(congestion-delay) time are suggested by the result of experiment in virtual crosswalk. the application of suggested models in this study to the site. It is possible to use as a basic stuff on study of pedestrian's signal time and expected to contribute the safety and mobility in future.

• Archives of design research
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• v.12 no.3
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• pp.237-246
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• 1999

The study ooramed has the meanngs as a goal, to examine a character and changes of function a "Maru" in the literatures historically. Methodically the literatures in the temporal oonsequences were selected, and the "Maru", whidl oomes into it, was interpreted in its historical oonnections. By the investigation I oould oome to the following results. First of all, those terms "Maru" and "Daechll1Q" were cfifferently used after the sizes and p1ares of the spaces concerned. I.e, the "Maru" in the center of the house is called "Daed1ung", With the Maru does not concern actually its p1are, Secondly, the functions of the spare "Maru" are characterized as follows. ·Space for the important ceremonies ·Spare for the passage and the switching of two or several spaces. ·Determination of the hierardly of spares in the whole house. ·Spare for the receipt. ·Spare for sleeping and for living. ·Spare for work, storage etc. Thirdly, the meanings of the "Maru" were dlanged as follows in the time. ·The term "Man! was used from the past to today without interrujjion. Arot.l1d 1930 the tenns "Yangsil" and "Geosil" for the tenn "Maru" were emerged. ·The different dlaraderistics for the space "Maru" are found in the cortemporary literatures only rare. This thing explains itself by the fad that the "Maru" becomes the inner-spare after 1900 by the restructuring of the dwelling spares.hing explains itself by the fad that the "Maru" becomes the inner-spare after 1900 by the restructuring of the dwelling spares.

• Journal of Korean Institute of Industrial Engineers
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• v.27 no.3
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• pp.226-232
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• 2001

This paper presents an efficient method for the problem of determining the spare inventory level of a multi-echelon repairable-item inventory system. We consider the system with two levels of inventory, two levels of service and with a general service time distribution. We propose an algorithm that determines the spare inventory level to satisfy the minimum fill rate with the minimum cost. Experimental results show that the algorithm is accurate and efficient.

• Journal of Korean Society for Quality Management
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• v.14 no.2
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• pp.21-27
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• 1986

This paper deals with a continuous review (s,S) spare part inventory system. The distributions of service life of each part and the replenishment lead time are assumed to be exponential. Assuming that there is never more than a single order outstanding, we obtain the average annual cost of operating the inventory system. If the length of stockout period is small enough to be neglected compared to the length of operating period, the optimal operating policy variables minimizing the cost rate can be calculated iteratively. For the case of one-for-one ordering (that is, s=S-1), an exact cost rate, and a closed form decision rule minimizing the cost rate are obtained for a more general situation in which more than one order is allowed to be outstanding and the distribution of the replenishment lead time is general.

• Journal of dental hygiene science
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• v.20 no.3
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• pp.126-135
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• 2020

Background: The purpose of this study is to investigate the effects of entrance exam stress on oral health behaviors and subjective oral health status in female high school students. Methods: A self-reported questionnaire was administered to 216 female high school students in the Gwangju area. We performed an independent t-test, one-way analysis of variance (ANOVA), Pearson's correlation coefficient, and multiple regression analysis using the SPSS/WIN 21.0 program. Results: The average of the entrance exam stress was 2.73, and among the sub-areas, the tension for exam/poor stress was the highest with 3.21. As a result of analysis of general characteristics and subjective oral health status, oral mucosal disease was lower in family income level (p<0.05), bad breath was significantly higher with lower academic performance (p<0.001) and family income level (p<0.05). As a result of oral health behavior and subjective oral health status analysis, dental caries has more than 4 times of caries snacks (per week) (p<0.05), bad breath was found to be more perceived when the average number of daily brushing was 2 or less (p<0.01). Factors affecting subjective oral health status were that dental caries was a patients pressure stress (β=0.202); temporomandibular disorder (β=0.227), xerostomia (β=0.342), and oral mucosal disease (β=0.190) were insufficient spare time; bad breath was academic performance (lower) (β=0.231) and insufficient spare time (β=0.184). There was a statistically significant positive correlation between the subjective oral health status and the subarea of entrance exam stress, excluding future uncertainty stress. Conclusion: It is considered that oral health education should be conducted to prevent oral diseases for students with high parental pressure and insufficient spare time stress as well as finding practical ways to reduce entrance stress.

• Korean Management Science Review
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• v.31 no.2
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• pp.1-13
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• 2014

In almost all of the organizations, the cost for acquiring and maintaining the inventory takes a considerable portion of the management budget, and thus a certain constraint is set upon the budget itself. The previous studies on inventory control for each item that aimed to improve the fill rate, backorder, and the expenditure on inventory are fitting for the commercially-operated SCM, but show some discrepancies when they are applied to the spare parts for repairing disabled systems. Therefore, many studies on systematic approach concept considering spare parts of various kinds simultaneously have been conducted to achieve effective performance for the inventory control at a lower cost, and primarily, METRIC series models can be named. However, the past studies were limited when dealing with the probability distributions for representing the situation on demand and transportation of the parts, with the (S-1, S) inventory control policy, and so on. To address these shortcomings, the Continuous Time Markov Chain (CTMC) model, which considers the phase-type distributions and the (s, Q) inventory control policies to best describe the real-world situations inclusively, is presented in this study. Additionally, by considering the cost versus the system availability, the optimization of the inventory level, based on this model, is also covered.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.33 no.3
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• pp.199-207
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• 2010

In this paper considered is the provisioning quantity determination problem of consumable concurrent spare parts (CSP) of a new equipment system to minimize the procurement cost under the operational availability constraint. When a part fails, repair of the failed part is impossible and the part is replaced and cannibalization is allowed. The failure of a part is assumed to follow a Poisson process and the operational availability in CSP is defined. The solution procedure consists of two parts. Firstly, a heuristic algorithm is developed under the assumption that the failure rate is constant during the CSP period. Secondly, proposed is a simulation search procedure which improves the heuristic solution to the near optimal solution in a reasonable amount of time. An illustrative example is shown to explain the solution procedure.

• Korean Management Science Review
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• v.13 no.3
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• pp.163-172
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• 1996

According to flying hours, aircraft engines require regular overhaul for preventive maintenance. Because of hostile defense environment of Republic of Korea, the aircraft of republic of Korea Air Force(ROKAF) have been operated at the maximum level of availability and have similar overhaul schedule in several months. The concentration of overhaul schedule in a short period demands additional spare engines far exceeding the spare engines for corrective maintenance. If ROKAF decides to purchase extra engines for the preventive maintenance, the extra engines will be used only for the preventive maintenance and will be excess inventory for the most of aircraft life ccle. Also, the procurement of extra engines is significant investment for ROKAF. To help ROKAF schedule the preventive maintenance without significant spending, this study develops a dynamic programming model that is solvable using an integer programming algorithm. The model provides the number of engines that should be overhauled for a month for multiple periods under given constraints. ROKAF actually used this model to solve a T-59 engine overhaul problem and saved about three billion won at one time. ROKAF plans to use this model continuously for T-59 and other weapon systems. Thus, saving for long term will be significant to ROKAF. Finally, with minor modification, this model can be applied to deciding the minimum number of spare engines for preventive maintenance.