• International Journal of Reliability and Applications
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• 제7권1호
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• pp.27-39
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• 2006

Many real world cases in material failure analysis do not follow perfectly the normal distribution. Forcing of the normality assumption may lead to inaccurate predictions and poor product quality. We examine the failure process of the internal bond (IB or tensile strength) of medium density fiberboard (MDF). We propose a forced censoring technique that closer fits the lower tails of strength distributions and better estimates extremely smaller percentiles, which may be valuable to continuous quality improvement initiatives. Further analyses are performed to build an accelerated common-shaped Weibull model for different product types using the $JMP^{(R)}$ Survival and Reliability platform. In this paper, a forced censoring technique is implemented for the first time as a software module, using $JMP^{(R)}$ Scripting Language (JSL) to expedite data processing, which is crucial for real-time manufacturing settings. Also, we use JSL to automate the task of fitting an accelerated Weibull model and testing model homogeneity in the shape parameter. Finally, a package script is written to readily provide field engineers customized reporting for model visualization, parameter estimation, and percentile forecasting. Our approach may be more accurate for product conformance evaluation, plus help reduce the cost of destructive testing and data management due to reduced frequency of testing. It may also be valuable for preventing field failure and improved product safety even when destructive testing is not reduced by yielding higher precision intervals at the same confidence level.

• Communications for Statistical Applications and Methods
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• 제18권3호
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• pp.277-286
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• 2011

Global companies can sell their products with dierent warranty periods based on location and times. Customers can select the length of warranty on their own if they pay an additional fee. In this paper, we consider the warranty period and the repair time limit as random variables. A two-dimensional warranty policy is considered with repair times and failure times. The repair times are considered within the repair time limit and the failure times are considered within the warranty period. Under the non-renewable warranty policy, we obtain the expected number of warranty services and their variances in the censored area by warranty period and repair time limit to conduct a warranty cost analysis. Numerical examples are discussed to demonstrate the applicability of the methodologies and results using field data based on the proposed approach in the paper.

• 한국신뢰성학회지:신뢰성응용연구
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• 제11권1호
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• pp.43-57
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• 2011

In the paper, we consider two-dimensional warranty policy with failure times and repair times. The failure times are considered within the warranty period and the repair times are considered within the repair time limit. Under the renewable warranty policy and non-renewable warranty policy, we consider the number of warranty services in the censored area by warranty period and repair time limit to conduct warranty cost analysis. We investigate the field data to check their dependency and implement our proposed approaches to conduct warranty cost analysis using the parametric methods. Numerical examples are discussed to demonstrate the applicability of the methodologies and results based on the proposed approach in the paper.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.611-612
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• 2006

Many data mining techniques have been proved useful in revealing important patterns from large data sets. Especially, data mining techniques play an important role in a customer data analysis in a financial industry and an electronic commerce. Also, there are many data mining related research papers in a semiconductor industry and an automotive industry. In addition, data mining techniques are applied to the bioinformatics area. To satisfy customers' various requirements, each industry should develop new processes with more accurate production criteria. Also, they spend more money to guarantee their products' quality. In this manner, we apply data mining techniques to the production-related data such as a test data, a field claim data, and POP (point of production) data in the automotive parts industry. Data collection and transformation techniques should be applied to enhance the analysis results. Also, we classify various types of manufacturing processes and proposed an analysis scheme according to the type of manufacturing process. As a result, we could find inter- or intra-process relationships and critical features to monitor the current status of the each process. Finally, it helps an industry to raise their profit and reduce their failure cost.

• 조명전기설비학회논문지
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• 제27권11호
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• pp.82-88
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• 2013

It is important to give lightning warning prior to a cloud-to-ground (CG) discharge within an Area of Concern (AOC) because most of lightning damage and victim are usually occurred by the first lightning in the AOC. The aim of this study is to find the optimal operation conditions of the automated lightning warning systems in order to make the best use of the available data. In this paper, the test-operated results of the automated lightning alert and risk management system (ALARM) based on detections of CG discharge and eletrostatic field and optimized at probability of lightning have been described. It was possible to obtain the following warning performance parameters: probability of detection (POD), false alarm ratio (FAR), probability of lightning (POL) and failure-to-warn rate (FTW). The data obtained from trial operation for 5months were not sufficient but the first analysis of domestic lightning warning was carried out. We have observed that the evaluated statistical results through trial operation depend on the various factors such as analysis methods and criteria, topographical conditions, etc. Also we suggest some methods for improvement of POL and POD including the finding of the optimal electric field threshold level to be used, based on the high values of FAR and FTW found in this work.

• 한국농공학회지
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• 제32권E호
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• pp.67-73
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• 1990

Many distress mechanisms in pavement are known to be caused by the poor mechanical properties of bituminous concretes. Among many mechanical properties, tensile strength is one of the more important indicates that represent the resistance of pavement to traffic loading. However, there has been no relationship established between the strength and distress mechanisms. Therefore, this study was conducted to evaluate a correlation between the tensile strength value and the intensity of distress in bituminous concrete. Distress data were collected from an extensive field investigation over 77km of a four-lane highway in South Carolina, USA, and from laboratory prepared specimens in two phases of study. Strength data were obtained from a total of more than 400 field cores taken from the same highway and from 640marshall specimens of surface course mixture prepared in the laboratory. These data were analyzed using statistical test techniques. It was found from statistical analyses that the tensile strength of bituminous concrete had a strong relation with the pavement condition in the field. In the analysis of rutting and stripping, low strength concrete showed a higher distress rate in the mixture, and mixtures under distress in the field showed obviously reduced strength values. Stripping was found to be the most significant distress mechanism that was correlated with low strength bituminous concrete. Rutting appeared more frequently in a low strength pavement section of the highway as a sign of failure due to traffic loading.

• Journal of Biosystems Engineering
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• 제27권2호
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• pp.133-142
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• 2002

This is a fundamental study to develop a sensor to detect weeds in paddy field using machine vision adopted spectralphotometric technique in order to use the sensor to spread herbicide selectively. A set of spectral reflectance data was collected from dry and wet soil and leaves of rice and 6 kinds of weed to select desirable wavelengths to classify soil, rice and weeds. Stepwise variable selection method of discriminant analysis was applied to the data set and wavelengths of 680 and 802 m were selected to distinguish plants (including rice and weeds) from dry and wet soil, respectively. And wavelengths of 580 and 680 nm were selected to classify rice and weeds by the same method. Validity of the wavelengths to distinguish the plants from soil was tested by cross-validation test with built discriminant function to prove that all of soil and plants were classified correctly without any failure. Validity of the wavelengths for classification of rice and weeds was tested by the same method and the test resulted that 98% of rice and 83% of weeds were classified correctly. Feasibility of CCD color camera to detect weeds in paddy field was tested with the spectral reflectance data by the same statistical method as above. Central wavelengths of RGB frame of color camera were tried as tile effective wavelengths to distingush plants from soil and weeds from plants. The trial resulted that 100% and 94% of plants in dry soil and wet soil, respectively, were classified correctly by the central wavelength or R frame only, and 95% of rice and 85% of weeds were classified correctly by the central wavelengths of RGB frames. As a result, it was concluded that CCD color camera has good potential to be used to detect weeds in paddy field.

• 한국산학기술학회논문지
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• 제16권5호
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• pp.3370-3377
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• 2015

전동차는 대용량 교통수단으로서 정시 운행 및 높은 안전성이 요구되기 때문에, 고장 분석을 체계적으로 수행하여 신뢰도를 향상시키기 위한 수단으로서 고장 영향의 심각도 및 치명도를 정량적으로 평가하는 FMECA (Failure Modes, Effects and Criticality Analysis) 기법이 적용되고 있다. 그러나, 아직까지 전동차에 특화된 FMECA 규격 및 절차는 정립되어 있지 않고 자동차 산업 등 다른 산업분야의 FMECA 규격을 그대로 적용하고 있기 때문에 전동차의 고유한 운영 및 유지보수 여건을 충분히 반영하지 못하고 있다. 본 논문에서는 산업계 각 분야에서 적용되고 있는 FMECA 규격에 대한 분석을 토대로, 전동차 분야에 적합한 FMECA 기법으로서 고장 영향 분석과 치명도 분석을 단계별로 나누어 수행하고 고장 영향의 심각도에 중점을 두어 치명도를 분석하는 기법을 제시하였다. 제안 기법을 전동차의 핵심 안전 장치인 고속차단기에 적용하여 도시철도 현장에서의 15년 동안의 전동차 유지보수 데이터를 이용하여 분석한 결과, 고속차단기 부품 중에서 특히 아크 슈트의 절손이 심각도 3등급, 치명도 5등급으로 위험도가 가장 높았으며, 뒤를 이어서 전자변 파손 및 접촉 불량, 실린더 파손 등이 심각도 3등급, 치명도 4등급으로 위험도가 높은 것으로 나타났다. 이상의 분석 결과는 전동차 고속차단기의 설계 및 유지보수 업무의 개선에 활용할 수 있다.

• International Journal of Railway
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• 제5권1호
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• pp.1-9
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• 2012

Reliability means that a product maintains its initial quality and performance at a certain period of time (time, distance, cycle etc) under given condition without failure. The given conditions include both environmental condition and operating condition. Environmental condition means a common natural environment such as temperature, humidity, vibration, and working condition means an artificial environment such as voltage, current load, place for installment, and hours of use, which occurs during the life of the product. In the field of railway vehicles, it is mandatory to use a part with the proved reliability as the extension of the life of vehicle become highly necessary. But the reliable assessment method for the reliability of the part is insufficient. If the reliability of the railway vehicle parts could be assessed by using the field data, the reliability of the entire system could also be evaluated reliably. In this study, life span of micro-switch for master controller is analyzed and prediction is performed based on its field data given by an operator considering the special circumstances of railway vehicles such as the operation of a large number of trains on the same line.

• 대한토목학회논문집
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• 제36권2호
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• pp.231-243
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• 2016

본 연구에서는 이용 가능한 자료가 제약이 있는 실제 농업용 저수지 붕괴에 대한 2차원 홍수범람해석의 적용성을 보여주었다. 연구 대상 유역은 2013년 파이핑 현상에 의해 붕괴가 발생한 경주 산대저수지 및 하류부 지역이다. 본 연구에서는 1차원 모형으로 파이핑 붕괴에 따른 유출수문곡선을 도출하고, 이를 2차원 수치모형의 상류단 경계조건으로 사용하여 모의를 수행하였다. 2차원 홍수파 해석을 위해서 수치지도와 위성자료를 합성하여 지형자료를 구성하였고, 건물, 도로, 운동장 등의 형상을 정확하게 반영하기 위해 $3m{\times}3m$ 크기의 정형격자를 사용하여 모의를 수행하였다. 현장조사된 저수지 붕괴유출량, 범람범위, 홍수심 그리고 홍수 전파시간과 계산치를 비교하고, 합리적인 범위의 결과를 보여줌으로써 모형의 검증을 수행하였다. 또한, 격자크기, 건물 및 조도계수가 홍수범람에 미치는 영향을 분석하였다. 본 연구는 향후 농업용 저수지의 붕괴해석 및 하류부의 비상대처계획 수립에 기초자료로 활용될 수 있을 것으로 기대된다.