• Journal of Applied Reliability
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• v.17 no.2
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• pp.112-121
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• 2017

Purpose: The most previous works on designing accelerated life tests (ALTs) are focused on the application of a single stress. Because of the difficulty to obtain the sufficient information in a reasonable duration using single stress only, there is needed in practice to use multiple-stress ALTs frequently. This paper presents new practical plans with two stresses for Weibull distribution. Methods: The four-level practical plans based on rectangle test region are proposed and compared with the corresponding three-level statistically optimal plans. Sensitivity analyses for assumed design parameters and life-stress relationship are conducted. Results: A procedure to choose practical ALT plans is illustrated with a numerical example and guidelines for planning two-stress ALTs are provided. Conclusion: The proposed two-stress ALT plans on practical constraints to assess a quantile of Weibull lifetime distribution at the use condition are efficient and robust.

• Industrial Engineering and Management Systems
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• v.14 no.2
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• pp.183-195
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• 2015

In this paper, we propose a two-stage group acceptance sampling plan for generalized inverted exponential distribution under truncated life test. Median life is considered as a quality parameter. Design parameters are obtained to ensure that true median life is longer than a given specified life at certain level of consumer's risk and producer's risk. We also explore situations under which design parameters based on median lifetime can be used for other percentile points. Tables and specific examples are reported to explain the proposed plans. Finally a real data set is analyzed to implement the plans in practical situations and some suggestions are given.

• Journal of Electrochemical Science and Technology
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• v.15 no.3
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• pp.414-420
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• 2024

Lithium-ion batteries are widely used in many applications due to their high energy density, high efficiency, and excellent cycle ability. Once an unknown Li-ion battery is reusable, it is important to measure its lifetime and state of health. The most favorable measurement method is the cycle test, which is accurate but time- and capacity-consuming. In this study, instead of a cycle test, we present an empirical model based on the C-rate test to understand the state of health of the battery in a short time. As a result, we show that the partially accelerated charge/discharge condition of the Li-ion battery is highly effective for the degradation of battery capacity, even when half of the charge/discharge conditions are the same. This observation provides a measurable method for predicting battery reuse and future capacity degradation.

• International Journal of Reliability and Applications
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• v.6 no.2
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• pp.117-133
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• 2005

Estimations of the parameters included in a two-component system are derived based on masked system life test data, when the probability of masking depends upon the exact cause of system failure. Also estimations of reliability for the individual components at a specified mission time are derived. Maximum likelihood and Bayes methods are used to derive these estimators. The problem is explained on a series system consisting of two independent components each of which has a Pareto distributed lifetime. Further we present numerical studies using simulation.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.55-58
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• 2004

High Xe-content PDP characteristics are discussed. A high efficacy, up to 5 lm/W for a 50% Xe in Ne gas mixture, is realized in 4-inch color PDP test panel designs with low cost stripe-type barrier rib structures, that are powder blasted in soda lime glass. Furthermore, for a high Xe-content a high luminance can be obtained with a relatively small electrode area. Therefore the inter cell gap and the driving margin can be increased in a stripe-type barrier rib structure. Finally, for a high Xe-content the panel lifetime increases, due to increasing luminance and firing voltage stability. Clearly, these findings may direct the design development for next generation PDPs towards a high Xe-content

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1034-1037
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• 2006

We have developed a novel thin film encapsulation method for thin-cathode OLED by introducing organic (not polymer)/inorganic multiple thin films to protect device, which is shown to slow down the permeation rate of moisture and oxygen. From the stability test of devices, the projected lifetime of thin-cathode OLED device with thin film encapsulation was similarly to that with glass lid encapsulation.

• Journal of the military operations research society of Korea
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• v.9 no.2
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• pp.39-43
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• 1983

In this paper, we derive the likelihood function for the independent random order statistic whose underlying lifetime distribution is a two parameter Weibull form. For this purpose we first discuss the order statistic which represent a characteristic feature of most life and fatigue tests that they give rise to ordered observations. And, we describe the properties of the underlying Weibull model. The derived likelihood function is essential for establishing the statistical life test plans in the case of Weibull distribution using a likelihood ratio method.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.558-567
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• 2003

The catenary wires are damaged by periodic running of train as well as repeated stress. The wires are also degraded by atmosphere corrosion at fields. Corrosion of wires increased surface roughness and deteriorated mechanical properties by providing fatigue crack initiation sited resulting in a bad effect on service life of the wires. Fatigue test of catenary wires performed to estimate service lifetime. Also, simulation to analyze stress on catenary wires was conducted through modelling the finite elements for dynamic behaviors of wires. Fatigue life of catenary wires was estimated with fatigue and simulation tests.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.10a
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• pp.705-706
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• 2005

• Journal of the Semiconductor & Display Technology
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• v.12 no.4
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• pp.45-48
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• 2013

The electronic device, such as flat panel display (FPD), is very important in our life as a means of communication between humans. Liquid crystal display (LCD), which is categorized as a flat panel display, has been used in many display products, especially in TV industry. An LED TV is composed of several electrical components, such as liquid critical module (LCM), analog to digital convertor (AD), power supplier, and inverter board. These modules are very vulnerable to particulate contamination, and causing malfunction or visibility degradation. In this study, we developed a test method for prediction of LCM's lifetime. The test system consists of carbon particle generation flame, dilution system, test chamber, and particle concentration monitoring instrument. Since the carbon particles are the most abundant in the atmosphere and easily absorb light, soot particles are used as a challenging material for this test. The concentration of generated soot particles is set around 4,000,000 #/cc, which is 400 times higher than that of usual atmospheric particles. Through this experiment, we deduced the relationship between the dust concentration and life time of the test specimen.