• Journal of Applied Reliability
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• v.3 no.2
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• pp.103-116
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• 2003

We carry out reliability tests and investigate the failure mechanisms. of the wafer level vacuum packaged MEMS gyroscope sensor using an accelerated degradation test. The accelerated degradation test (ADT) is used to evaluate reliability (and/or life) of the MEMS vacuum package and to select the accelerated test conditions, which reduce the reliability testing time. Using the failure distribution model and stress-life model, we are able to estimate the average life time of the vacuum package, which is well agreed with the measured data. After improving several package reliability issues such as prevention of gas diffusion through package, we carry out another set of accelerated tests at the chosen acceleration level. The results show that reliability of the vacuum packaged gyroscope has been greatly improved and can survive without degradation of performance, which is the Q-factor in gyroscope sensor, during environmental stress reliability tests.

• Proceedings of the Korean Reliability Society Conference
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• 2005.06a
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• pp.327-337
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• 2005

Accelerated life test models and procedure are developed to assess the reliability of Door switch. The main function of door switch is to operate bulb lamp and fan motor. The accelerated life test method and test equipments are developed using the relationship between stresses and life characteristics of the products. Using the developed accelerated life test method, the parameters of the ALT model and life time distribution are estimated and the reliability of the Door S/W at use condition if assessed. The proposed accelerated life test method and procedure may be extended and applied to testing similar kinds of products to reduce test time and costs of the tests remarkably.

• Journal of Korean Society for Quality Management
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• v.36 no.1
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• pp.31-39
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• 2008

This paper proposes a method of estimating the lifetime distribution at use condition for constant stress accelerated life tests when an infant-mortality failure mode as well as wear-out one exists. General limited failure population model is introduced to describe these failure modes. It is assumed that the log lifetime of each failure mode follows a location-scale distribution and a linear relation exists between the location parameter and the stress. An estimation procedure using the expectation and maximization algorithm is proposed. Specific formulas for Weibull distribution are obtained. An illustrative example and the simulation results are given.

• Journal of Applied Reliability
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• v.11 no.2
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• pp.127-140
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• 2011

This paper presents an accelerated life test of aviation taxiway lights installed in the airport to help safe navigation of airplanes at night or in bad weather. Recently halogen lamps of taxiway lights are replaced by LED ones and their reliability needs yet to be verified. Thus, effective test conditions are designed reflecting the failure modes and mechanisms from the previous studies on LED, which include the accelerated degradation process. The test is performed under the temperature $70^{\circ}C$ and $90^{\circ}C$ for two types of LED lights, taxiway center line lights(TCLL) and taxiway edge lights (TEDL). The failure time data were analyzed using lognormal distribution and Arrhenius model to find the life-stress relationship, acceleration factor and life characteristics under the normal condition temperature $30^{\circ}C$.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.157-159
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• 2017

This paper presents a storage reliability evaluation method based on the accelerated degradation test for the engine assembly and parts of the guided missile. The test of the engine assembly is performed at accelerated conditions equivalent to the real storage period, and then the aging condition of parts is checked. For engine parts, performance degradation characteristics are measured periodically at the accelerated conditions and failure times are predicted at each condition. Storage lifetime at normal use conditions is predicted using an accelerated model and failure times at all accelerated conditions.

• Journal of Applied Reliability
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• v.14 no.2
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• pp.93-96
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• 2014

RFID (Radio Frequency IDentification) system is recognition technology which can maintain various object's information. Reliability of RFID tags is the most important factor in RFID system. In this paper, we proposed ALT (Accelerated Life Test) method for UHF RFID tags. Temperature and humidity were adopted as stress factors and the accelerated life tests were conducted in three different conditions. We performed failure analysis for identifying failure mechanism and statistical analysis of test data. In the statistical analysis, we employed Inverse Power law for relationship between tag's life and stress. Through the statistical analysis, we proposed acceleration factor for several levels of temperature-humidity. The reliability qualification test plans were also designed for the tag's target reliability.

• Journal of Applied Reliability
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• v.5 no.2
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• pp.273-287
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• 2005

Accelerated life test models and procedure are developed to assess the reliability of Refrigerator door switch. The main function of door switch is to operate bulb lamp and fan motor in the refrigerating room. The accelerated life test method and test equipments are developed using the relationship between stresses and life characteristics of the products. Using the developed accelerated life test method, the parameters of the ALT model and life time distribution are estimated and the reliability of the Door S/W at use condition if assessed. The proposed accelerated life test method and procedure may be extended and applied to testing similar kinds of products to reduce test time and costs of the tests remarkably.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.445-450
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• 2003

This study was performed 10 develop the accelerated life test method using Weibull-IPL(Inverse Power Law) model for mechanical components. Weibull-IPL model is concerned with determining the assurance life with confidence level and the accelerated life test time From the relation of weibull distribution factors and confidence limit, the testing times on the no number of failure acceptance criteria arc determined. The mechanical components generally represent wear and fatigue characteristics as a failure mode. IPL based on the cumulative damage theory is applied effectively the mechanical components to reduce the testing time and to achieve the accelerating test conditions. As the actual application example, accelerated life test method of agricultural tractor transmission was described. Life distribution of agricultural tractor transmission was supposed to follow Weibull distribution and life test time was calculated under the conditions of average life (MTBF) 3,000 hours and 90% confidence level for one test sample. According to IPL, because test time call be shorten in case increase test load test time could be reduced by 482 hours when we put the load 1.1 times of rated load than 0.73 times of rated load that is equivalent load calculated by load spectrum of the agricultural tractor. This time, acceleration coefficient was 11.7.

• Genomics & Informatics
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• v.14 no.4
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• pp.166-172
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• 2016

Although a large number of genetic variants have been identified to be associated with common diseases through genome-wide association studies, there still exits limitations in explaining the missing heritability. One approach to solving this missing heritability problem is to investigate gene-gene interactions, rather than a single-locus approach. For gene-gene interaction analysis, the multifactor dimensionality reduction (MDR) method has been widely applied, since the constructive induction algorithm of MDR efficiently reduces high-order dimensions into one dimension by classifying multi-level genotypes into high- and low-risk groups. The MDR method has been extended to various phenotypes and has been improved to provide a significance test for gene-gene interactions. In this paper, we propose a simple method, called accelerated failure time (AFT) UM-MDR, in which the idea of a unified model-based MDR is extended to the survival phenotype by incorporating AFT-MDR into the classification step. The proposed AFT UM-MDR method is compared with AFT-MDR through simulation studies, and a short discussion is given.

• Transactions of The Korea Fluid Power Systems Society
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• v.2 no.4
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• pp.14-22
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• 2005

The safety factor of hydraulic piston pumps & motors due to high pressurization, high speedization and low weight/volume realization to enhance the output density shows a tendency to decrease. Therefore more effective test methods are necessary to predict the exact life. The failure of hydraulic pumps & motors operating in high pressure and high speed mainly occurs in piston-shoe assemblies, and the major failure mode is wearout of the shoe surface. The sensitive parameters in the endurance life test are speed, pressure and temperature, and the failure production increases in proportion to the operating time. In this research, the authors propose the combined accelerated life test model using the analysis method of the combined accelerated life test results of piston-shoe assemblies by applying simultaneously high speed, high pressure and high temperature in accordance with variation of speed, pressure and temperature to reduce the life test time.