• 가정과삶의질연구
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• 제1권2호
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• pp.59-73
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• 1983

The purpose of this study is to establish the family economy planning in the side of economic welfare and to discuss its problems. Hypothesis testing and survey analysis whether nuclear family have been formed in the urban communities or not are investigated. Also, survey of family economic period are classified in the following manner. First, as the beginning of family, they are interested in savings, children's education and investment of an estate. Third, as the contracting period of family, they rely upon other's financial supports. Therefore, it is desirable for each family to establish family life cycle planning. As the results of hypothesis testing, 1) Nuclear family have been formed in urban communities. 2) The age of housewives is not concerned with whether their husband's parents live in the same house or not. 3)The age of housewives is not concerned with whether their parents lived with them or not. 4) The relationship between the age of housewives and monthly income is not significant. 5) The relationship between the age of housewives and monthly expenditure is significant. 6)The relationship between the age of housewives and monthly savings is not significant.

• Industrial Engineering and Management Systems
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• 제9권1호
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• pp.54-59
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• 2010

A two-plan sampling system is proposed for a failure-censored life testing when the lifetime follows a Weibull distribution with known shape parameter. The proposed sampling system is based on a switching rule, for switching between the tightened and the normal inspection levels when lots are submitted for inspection in the order of production or in some other systematic way. The design parameters of the proposed sampling system are determined by the two-point approach considering the producer's risks and the consumer's at the specified acceptable reliability level and the lot tolerance reliability level, respectively. It has been observed that the proposed system requires only a single failure for the observation.

• International Journal of Reliability and Applications
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• 제3권4호
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• pp.185-198
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• 2002

In the traditional life testing model, it is assumed that a certain number of identical items are tested under identical condition. This is due to statistical rather than practical considerations. The proportional hazards model can be used to develop a realistic approach to determine the performance of an item. That is also capable of modeling the failure rates of accelerated life testing when the covariates are applied stresses. The proportional hazards model is typically applied for a group of items to assess the importance of factors that may influence the reliability of an item. In this paper we considered the interarrival times of an item rather than the time to first failure for grouped items and provided the availability estimation for the determination of maintenance policy and overhaul time. In order to demonstrate the proposed approach, an example is presented.

• 비파괴검사학회지
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• 제10권1호
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• pp.56-64
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• 1990

It is well-known that the defects (existing in structures) and the material degradation(caused by the fatigue load) generally initiate the failure of structures. The NDE such as ultrasonic technique which can be used to detect the size and the orientation of defects has been utilized to estimate the life and stability of structures. However, only few experimental reports made by using the ultrasonic technique have been published for the case of fatigue estimation of materials and structures. The purpose of this study is, thus, to derive the relationship between ultrasonic attenuation and fatigue behavior of Polycarbonate and PMMA through ultrasonic characterization. It is also attempted to offer NDE experimental procedure which may be useful to predict fatigue life.

• International Journal of Reliability and Applications
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• 제4권4호
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• pp.191-199
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• 2003

In the present work, a moment inequality is derived for new renewal better (worse) than used in expectation(NRBUE) (NRWUE) distributions. This inequality demonstrates that if the mean life is finite then all higher order moments exist. A new test statistics for testing exponentiality against NRBUE (NRWUE) is introduced based on this inequality. It is shown that the proposed test is simple and has high relative efficiency for some commonly used alternatives. Critical values are tabulated for sample sizes n = 5(1)30. A set of real data is used as an example to elucidate the use of the proposed test statistics for practical reliability analysis.

• Journal of the Korean Wood Science and Technology
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• 제31권6호
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• pp.45-54
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• 2003

The density and strength of wood is affected by degradations and defects, such as voids and knots. Old wooden structures such as traditional cultural properties have been deteriorated by these types of defects. They were evaluated by a visual observation that is difficult to evaluate the inner deterioration in structures. In this study, three nondestructive testing techniques were investigated to detect the wooden structural members. Ultrasonic stress wave tests, drilling resistance tests and visual inspections were used to examine the structural wood members. Patterns of Resistograph using by drilling resistance tests could indicate the features of internal wood such as voids, knots, decay, fungi, and so on. The technique just like as ultrasonic stress wave tests, however, difficult to detect exactly area where small amounts of internal deterioration in logs are. In spite of results of ultrasonic stress wave test, the internal deterioration of wooden structural members could be evaluated by the relationship between ultrasonic stress wave tests and drilling resistance tests.

• 비파괴검사학회지
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• 제24권5호
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• pp.525-531
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• 2004

본 고는 적외선 열화상의 개념과 적외선열화상 측정윈리 및 카메라 셋팅을 기술하고 적외선열화강(IRT)에 의한 비파괴검사(NDT)의 활용 및 비파괴검사의 진단에 대하여 살펴보았다. 적외선 열화상은 주어진 표면을 따라 온도에 관련된 열패턴의 평가를 통한 정기적인 비접촉, 비파괴 시험의 수행으로 초기에 장비 고장의 예방이 가능하다. 진단 활용으로서, 열적으로 가열된 내부결함이 있는 블록에 대하여 적외선열화상을 이용한 열화상 패턴을 비파괴 기법으로 평가하고, 결함과 열화상패턴간의 특성을 분석하여 열화상 평가 기법에 대하여 논하였다.

• 정보처리학회논문지D
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• 제11D권7호
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• pp.1491-1498
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• 2004

성공적인 프로젝트 계획은 활용 가능한 일정과 더불어 프로젝트를 완수하는데 요구되는 인력을 얼마나 정확히 추정하느냐에 달려있다. 새로운 또는 보다 나은 모델 개발에 많은 연구가 이루어졌지만 현존하는 소프트웨어 인력 추정 모델들은 소프트웨어 생명주기 전반에 걸쳐 투입되는 총 개발인력 또는 시간에 따른 단위시간당 개발인력 분포만을 제공하고 있다. 본 논문은 시간의 함수가 아닌 발견된 결함 수에 따라 시험단계에 투입되는 인력과 시험단계의 시험과정과 디버깅과정에 투입되는 인력을 추정하는 모델들을 제시하였다. 시험과 디버깅 과정에서 발견되는 결함에 기반한 투입 인력의 다항식 모델을 제안한다. 제안된 모델들은 5종의 다른 소프트웨어 프로젝트들에 적용되어 결정계수와 MMRE를 통해 모델의 적합성을 검증하였다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2005년도 춘계학술대회 논문집
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• pp.71-76
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• 2005

The defects evaluation of the interior and the surface would be considered as vital characteristics in predicting the total life span of the steel structure. More importantly, the understandings in the interior composite of welding zone and the notifications in the presence, the formation, and the positioning of the non-metallic inclusion are necessary as well, since there were signs of relatively high defect frequency presented in the welding zone. The ultrasonic testing is a highly recommended technique chosen from among other techniques because of variety of advantages in conducting the non-destructive testing for the welding zone. However, the ultrasonic testing had technical disadvantages referred as followings; the problems due to the couplant between the PZT and the specimen, the formations that were miniature and complex, the moving subject, and the high temperature surrounding the specimen. This research was conducted to resolve the technical disadvantages of the contact ultrasonic testing by studying the non-contact ultrasonic testing where the ultrasonic waves were transferred by the laser, and revealing the specimen defects at its interior part and its surface part. The ultimate goal of this research was to develop a non-destructive evaluation applying the laser manipulated ultrasonic method for the steel structure.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.707-712
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• 2006

Knowing the ground thermal conductivity is very importnat in designing ground heat exchangers. Knowledge of the ground soil and rock composition information dose not guarantee the prediction of accurate thermal information. In Situ testing of ground heat exchangers is becoming popular. However, in situ testing are performed at construction sites in real life. Adequate data collection and analysis are not easy mainly due to poor power quality. Power fluctuation also causes the fluctuation of received data. The power quality must be maintained during the entire in situ testing processes. To accurately analyse the test data, the understanding of the response of the power fluctuation is essential. Testing under the power quality varied by tester is very difficult. Analyzing power variation by numerical simulation is a realistic option. By varying power in a sinosuidal manner, its effects on predicting thermal conductivity from thermal response plots made from the test data are examined.