• Communications for Statistical Applications and Methods
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• 제24권2호
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• pp.115-127
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• 2017

This paper proposes a Bayesian test for the equivalence of survival functions in multiple groups. Proposed Bayesian test use the model of Cox's regression with time-varying coefficients. B-spline expansions are used for the time-varying coefficients, and the proposed test use only the partial likelihood, which provides easier computations. Various simulations of the proposed test and typical tests such as log-rank and Fleming and Harrington tests were conducted. This result shows that the proposed test is consistent as data size increase. Specifically, the power of the proposed test is high despite the existence of crossing hazards. The proposed test is based on a Bayesian approach, which is more flexible when used in multiple tests. The proposed test can therefore perform various tests simultaneously. Real data analysis of Larynx Cancer Data was conducted to assess applicability.

• Journal of the Korean Data and Information Science Society
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• 제17권1호
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• pp.115-122
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• 2006

A test is suggested for detecting deviations from both multivariate normality and independence. This test can be used for assessing the normality and independence of univariate time series residuals. We derive the limiting distribution of the test statistic and a simulation study is conducted to study the accuracy of the limiting distribution in finite samples. Finally, we apply our method to a real data of time series.

• 대한전자공학회논문지SD
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• 제41권9호
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• pp.97-106
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• 2004

본 논문에서는 내장 코어 기반 SOC의 테스트를 위한 새로운 테스트 전략을 제안한다. SOC 테스트는 전체 테스트 시간을 얼마나 줄일 수 있는가에 따라서 그 성능을 평가할 수 있다. SOC를 구성하는 코어에 대한 테스트 시간은 코어에 구성된 테스트 래퍼 구조에 의해서 결정되며, 테스트 래퍼는 TAM을 사용하기 때문에 결국 TAM에 할당되어 있는 스캔 체인의 길이에 의해서 결정된다. 따라서 SOC 설계 단계에서 테스트를 고려한 설계가 이뤄져야 하며 효율적인 테스트를 위해서는 테스트 전략을 잘 세워야 한다. 기존의 테스트 기법은 모두 SOC 전체 TAM 라인들을 몇 개의 그룹으로 나누고 코어에 할당된 스캔 체인들을 TAM 라인에 적절히 분배해서 코어의 테스트 시간과 SOC 전체의 테스트 시간을 모두 최소화 할 수 있는 구조를 만드는 방법이었다 하지만 이는 NP 문제로 모든 조합에 대한 시도를 통해서 최적의 곁과를 찾는 것이 불가능하다. 본 논문에서는 이 문제에 대한 새로운 방법을 제안하고 그 효율성을 증명한다.

• 대한전자공학회논문지SD
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• 제41권3호
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• pp.93-100
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• 2004

시스템 온 칩의 테스트 스케줄링은 제한된 전력 사용량 내에서 테스트 시간을 최소화하기 위한 방법들 가운데 하나로서 매우 중요하다. 본 논문에서는 테스트 자원들을 선택하여 그룹화하고 코어 기반 시스템 온 칩 전체 전력소비량을 고려하면서 테스트 시간과 전력소모량의 곱의 크기에 기초하여 이들을 배열하여 스케줄링 하는 휴리스틱 알고리듬을 제안한다. 전력소모량은 최대이면서 제한된 전력 소모량을 초과하지 않는 테스트 자원 그룹을 먼저 선택하고 테스트 자원 그룹 내 요소들의 테스트 시작 위치를 테스트 공간의 초기 위치에 배치하여 테스트 자원들의 낭비시간을 최소화한다. ITC02 벤치마크 회로를 사용한 실험을 통해 알고리듬의 유효성을 보인다.

• 한국직업건강간호학회지
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• 제6권1호
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• pp.53-71
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• 1997

Across sectional study was performed to evaluate the chronic effects on central nerve system(CNS) of cumulative exposure of complex organic solvents, using neurobehavioral test. Subjects were 66 (male) dock yard painters of some large ship industry which is located in Ulsan. The neurobehavioral test battery used in this study was NCTB (Neurabehavioral Core Test Battery recommended by WHO(World Health Organization), which consisted of 7 items-Profile of mood states (POMS), Simple reaction time, Santa Ana dexterity test. Digit span, Digit symbol, Benton visual retention test and Pursuit aiming. The subjects were classified by 3 groups according to duration of employment(group 1 ; less than 9 years, group 2 ; 10-14 years, group 3 ; more than 15 years). The results of performance were analyzed considering of work duration, age, educational level, alcohol drinking, smoking and testing time as confounding factors. Benton visual retention test, pursuit aiming correct dot and sum of dot showed significant differences among the groups, and decreased with increasing work duration. It indicated that the mean scores of performance ability were lowering according to work duration. Besides, the tests that didn't show statistical significances but showed linear trends were depression-dejection, vigor, fatigue of POMS, slowest time of simple reaction time and digit span forward. Most of the neurobehavioral test items were correlated with age and educational level. After controlling of confounding factors-age and educational level, the results followed ; digit span backward was different significantly. Tension-anxiety, depression-dejection, anger-hostility of POMS, SD and slowest time of simple reaction time, Santa Ana dexterity test non-preferred hand, digit span forward, Benton visual retention test and pursuit aiming correct dot decreased with increasing of work duration. The correlation analysis was done in order to find out the relationship between subjective symptom and the scores of neurobehavioral core test battery. According to the results of analysis there were no items that had statistical significant relationship(p<0.05).

• 동력기계공학회지
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• 제16권3호
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• pp.44-50
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• 2012

The reliability qualification test is essential in order to ensure the life time of the product under the normal operation conditions when a new product is developed. The reliability qualification test period has an important impact on the development time of new product. Therefore, some researches to reduce the test time of reliability qualification test have been actively studied. Generally, accelerated life test is well known as one method that can save the test time of the reliability qualification test. This test is conducted under the higher stress condition than normal condition. So we need to investigate what factor affects to the higher stress condition. This paper shows the relationship between the acceleration factor and reliability qualification test period. Especially, we focused on the method to obtain effective acceleration factors under the high temperature condition. Through some experiments for a refrigerator's compressor, we were able to confirm how to increase acceleration factors and how to reduce the reliability qualification test period with minimum samples.

• Journal of Information Processing Systems
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• 제8권2호
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• pp.213-240
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• 2012

Safety critical systems, real time systems, and event-based systems have a complex set of events and their own interdependency, which makes them difficult to test ma Safety critic Safety critical systems, real time systems, and event-based systems have a complex set of events and their own interdependency, which makes them difficult to test manually. In order to cut down on costs, save time, and increase reliability, the model based testing approach is the best solution. Such an approach does not require applications or codes prior to generating test cases, so it leads to the early detection of faults, which helps in reducing the development time. Several model-based testing approaches have used different UML models but very few works have been reported to show the generation of test cases that use events. Test cases that use events are an apt choice for these types of systems. However, these works have considered events that happen at a user interface level in a system while other events that happen in a system are not considered. Such works have limited applications in testing the GUI of a system. In this paper, a novel model-based testing approach is presented using business events, state events, and control events that have been captured directly from requirement specifications. The proposed approach documents events in event templates and then builds an event-flow model and a fault model for a system. Test coverage criterion and an algorithm are designed using these models to generate event sequence based test scenarios and test cases. Unlike other event based approaches, our approach is able to detect the proposed faults in a system. A prototype tool is developed to automate and evaluate the applicability of the entire process. Results have shown that the proposed approach and supportive tool is able to successfully derive test scenarios and test cases from the requirement specifications of safety critical systems, real time systems, and event based systems.

• Journal of Biosystems Engineering
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• 제34권5호
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• pp.325-330
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• 2009

This study was performed to develop accelerated life test methods for agricultural tractor transmission receiving variable load. To acquire parameters for calculation of accelerated life test, endurance tests were performed under different torque conditions. Test results showed that the shape factor of Weibull distribution was 1.5 and fatigue damage exponent was 5.4. The calculated test time was 5,877 hours under the conditions of average life (MTBF) 3,000 hours and 90% reliability for one test sample. According to the linear cumulative damage rule, test time could be reduced using increased test load. Test time could be reduced by 252 hours when 1.2 times of the rated load compared with 0.67 times of the rated equivalent load calculated by load spectrum of the agricultural tractor. Calculated acceleration coefficient was 23.3.

• 한국신뢰성학회지:신뢰성응용연구
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• 제17권1호
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• pp.22-27
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• 2017

Purpose: The purpose of this study is to estimate the life time of OLED TV panel through electric current ADT(Accelerated Degradation Test). Methods: We performed accelerated degradation test for OLED TV Panel at the room temperature to avoid high temperature impact on the luminance. Results: we got more accurately the life time of the OLED TV when we applied ADT without temperature factor than including both current and temperature. Conclusion: Until now, the ADT of the OLED TV has been conducted with temperature and current at the same time for reducing test time and costs. We estimate incorrect life time when the temperature is adopted as an accelerated factor. Due to the high temperature impact on the luminance of the OLED TV panel. So as to solve this problem, we discard temperature and use electric current only.

• 한국도로학회논문집
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• 제8권3호
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• pp.155-162
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• 2006

시험도로 줄눈 콘크리트포장에 대하여 48시간 동안 시간에 따른 처짐의 변화를 측정하였고 이를 이용하여 컬링거동의 보정방안을 도출하였다. 임의 시간 슬래브의 중앙 처짐/줄눈 처짐이 임의 시간 중앙 처짐/기준 시간 중앙 처짐 사이의 관계를 회귀분석을 통해서 얻어내었다. 임의시간에 측정된 처짐으로부터 하루 가운데 최소 처짐이 나타나는 기준시간 처짐으로의 변환은 회귀곡선을 통해 추정 하였고 데이터 축적을 통해 컬링거동 보정 방안의 하나로 제시 할 수 있을 것으로 판단되었다.