• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 가을 학술발표회논문집
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• pp.109-114
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• 2000

In this paper, an optimum design model for minimizing the life-cycle cost (LCC) of high-speed railway steel bridges is proposed The point is that it takes into account service life process as a whole, and thus the life-cycle costs include initial (design, testing, and construction) costs, maintenance costs, expected strength failure costs and expected serviceability failure costs. The problem is formulated as that of minimization of expected total life-cycle cost with respect to the design variables. By processing the optimum LCC design the effective and rational basis is proposed for calculating the total LCC and the sensitivity analysis of LCC is peformed. Based on a numerical example, it may be positively stated that the optimum LCC design of high-speed railway steel bridges proposed in this study provides a lot more rational and economical design, and thus the proposed approach will expedite the development of new concepts and design methodologies that may have important implications in the next generation performance-based design codes and standards.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2002년도 추계기술심포지움논문집
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• pp.27-32
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• 2002

In this paper, global full 3D finite element analysis fatigue models are constructed for flip-chip BGA on board to predict the creep fatigue life of solder joints during the thermal cycling test. The fatigue model applied is based on Darveaux's empirical equation approach with non-linear viscoplastic analysis of solder joints. It was estimated by the creep life as the variations of the four kinds of thermal cycling test conditions, pad structure, composition and size of solder ball. The shortest fatigue life of results was obtained at the thermal cycling testing condition of -65℃ ∼ 150℃. It was increased about 3.5 times in comparison with that of 0℃ ∼ 100℃. As the change of pad structure at the same other conditions, the fatigue life of SMD structure increased about 5.7% as compared with NSMD structure. Consequently, it was confirmed that the fatigue life became short as the creep strain energy density increased in solder joint.

• Smart Structures and Systems
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• 제29권6호
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• pp.799-805
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• 2022

Permanent magnet synchronous motors (PMSMs) are widely used in systems requiring high control precision, efficiency, and reliability. Predicting the remaining useful life (RUL) with health monitoring of PMSMs prevents catastrophic failure and ensures reliable operation of system. In this study, a model-based method for predicting the RUL of PMSMs using phase current and vibration signals is proposed. The proposed method includes feature selection and RUL prediction based on a particle filter with a degradation model. The Paris-Erdogan model describing micro fatigue crack propagation is used as the degradation model. An experimental set-up to conduct accelerated life test, capable of monitoring various signals was designed in this study. Phase current and vibration data obtained from an accelerated life test of the PMSMs were used to verify the proposed approach. Features extracted from the data were clustered based on monotonicity and correlation clustering, respectively. The results identify the effectiveness of using the current data in predicting the RUL of PMSMs.

• Journal of Genetic Medicine
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• 제4권1호
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• pp.1-5
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• 2007

Unprecedented amount of genetic information being generated from the result of Human Genome Project (HGP) and advances in genetic research is already forcing changes in the paradigm of health and disease. The ultimate goal of genetic medicine is to use genetic information and technology to develop new ways of treatment or even prevention of the disease on an individual level for 'personalized medicine'. Genetics is play ing an increasingly important role in the diagnosis, monitoring and management of common multifactorial diseases in addition to rare single-gene disorders. While wide range of genetic testing have provided benefits to patients and family, uncertainties surrounding test interpretation, the current lack of available medical options for the diseases, and risks for discrimination and social stigmatization may remain to be resolved. However an increasing number of genetic tests are becoming commercially available, including direct to consumer genetic testing, yet public is often unaw are of their clinical and social implications. The personal nature of information generated by a genetic test, its power to affect major life decisions and family members, and its potential misuse raise important ethical considerations. Therefore appropriate genetic counseling is needed for patient to be informed with the benefits, limitations and risks of genetic tests, prior to informed consent for the tests. Physician also should be familiar with the legal and ethical issues involved in genetic testing to tell patients how w ell a particular genetic risk factor relates with likelihood of disease, and be able to provide appropriate genetic counseling. Genetic counseling become a mandatory requirement as global standard for many genetic testing such as prenatal diagnosis, presymtomatic DNA diagnostic tests and cancer susceptibility gene test for familial cancer syndrome. In oder to meet the challenge of genetic medicine of 21 century in korean health care system, professional education program and certification board for medical genetics specialist including non-MD genetic counselors should be addressed by medical society and regulatory policy of national health insurance reimbursement for genetic counseling to be in place to promote the implementation of clinical genetic service including genetic counseling for proper genetic testing.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2006년도 학술발표대회 논문집
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• pp.48-54
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• 2006

In this thesis, accelerated life test (ALT) method and procedure for rubber O-ring are applied to assure specified reliability of the products at guaranteeing the life of the products. Rubber O-ring is parts that keep intensity or make machine operation smoothly on attrition portion of machine and is used to prevent that oil is leaked. Usually. Rubber O-ring used NBR that is copolymer of acrylonitrile and butadiene. this are superior oil resistance, heat resistance, durability of abrasion, cold resistance, chemical resistance etc. The accelerated life test model for rubber O-ring are developed using the relationship between stresses and life characteristics of products. Using the accelerated life test method and the acceleration life test equipment which is developed, we performed life test, collected life data and analyzed the results of tests. The proposed accelerated life test method and procedure may be extended and applied to testing similar kinds of products to reduce test times and costs of the tests remarkably.

• Human Ecology Research
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• 제59권1호
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• pp.113-125
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• 2021

Previous research on the association between marriage and life satisfaction is limited due to the lack of attempts to investigate the time profiles of life satisfaction around marriage. This study addresses unresolved questions about the positive association between marriage and life satisfaction as well as tests if it is moderated by childhood parental divorce. Using 14 waves of the Korean Welfare Panel Study(N=3,890 individuals or 25,338 person-year observations), the author first used an ordinary least squares model with clustered standard errors and found that married people reported higher life satisfaction before marriage, compared to people who remained single during the survey. This result supports a social selection perspective. Next, the author used a fixed effects regression model and found that the transition into marriage was associated with an initial rise and subsequent decline in life satisfaction. Life satisfaction increased after reaching its lowest level in the third year of marriage. Life satisfaction after the transition into marriage was significantly higher than that observed three or more years prior to marriage. The result supports a social causation perspective. Such changing patterns were not moderated by parental divorce during childhood. This study advances the current literature on marriage and life satisfaction by using a nationally representative longitudinal data set as well as by testing social selection and causation perspectives.

• Asian Journal for Public Opinion Research
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• 제8권1호
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• pp.3-21
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• 2020

This study examined the relationship between residential environmental satisfaction and quality of life, and how the relationship between variables differed depending on housing type. Residential environments can affect a person's life in a variety of ways. However, there have not been many studies on the relationship between quality of life and residential environments, which increases the importance of this study. In this study, residential environments were categorized according to amenities, safety, and neighborhood relationships, which enabled the comparison of influence between these elements. In addition, this study analyzed the moderating effect of housing type to look for improvements for low-rise housing residents. For testing the hypotheses, moderating regression analysis was conducted with data from the 1^st Gyeonggi Province quality of life survey that had 18,953 subjects. Results showed that residential environmental satisfaction had a positive effect on quality of life, with amenities having the largest influence. Furthermore, housing type had a significant moderating effect on the relationship between safety and quality of life. In other words, safety was proven relatively important in improving quality of life for low-rise housing residents. Today, with the limits to quantitative growth, qualitative development has become more important. In this respect, this study provides important implications for many developing countries undergoing urbanization.

• 대한수학회논문집
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• 제34권2호
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• pp.383-390
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• 2019

In this paper, we discuss special polynomials involving exponential distribution, which is related to life testing. We derive some identities of special polynomials such as the symmetric property, recurrence formula and so on. In addition, we investigate explicit properties of special polynomials by using their derivative and integral.

• 한국산학기술학회논문지
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• 제21권7호
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• pp.406-418
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• 2020

무기체계를 개발할 때, 개발 목적에 맞는 장비의 기능과 성능을 구현하는 것도 중요하지만, 개발 후 장비가 얼마나 신뢰성을 가지고 공백이 없이 운용유지를 할 수 있는지 매우 중요하다. 그렇기 때문에 장비의 신뢰성을 높이기 위하여 다양한 활동을 수행한다. 개발 시 높은 스펙의 부품을 사용하고, 분석을 통하여 신뢰도를 검증하며, 개발 시제품을 이용하여 시험을 통해 장비의 부족한 부분은 보강하고 개선하여 신뢰성을 강화시키기 위한 활동을 한다. 그러나 최근에는 급변하는 외부 정세 및 기술 등에 의하여 개발 일정이 단축되고, 비용 등의 문제로 인하여 충분한 신뢰성 성장활동을 수행하지 못하는 경우가 발생하고 있다. 분석적인 방법(신뢰도 분석, FMECA 등)으로만 신뢰성 활동을 하는 사업들이 그 예이다. 본 논문에서는 FMECA와 초가속수명시험(HALT)을 통하여 분석과 시험이라는 방법을 같은 장비에 각각 수행했을 때, 도출된 신뢰성 성장 활동 내용과, 그로 인한 설계변경/검토 결과가 두 방법에서 어떠한 차이를 보이는지 비교/분석하고, 신뢰성 성장 활동을 강화하기 위한 방안을 제시하고자 한다. 개발 초기부터 분석을 통한 신뢰성 성장활동 및 초기 시제 제작 완료 시 시험을 통한 신뢰성 성장활동을 모두 수행해야 한다고 분석되었다.

• 한국작물학회지
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• 제59권2호
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• pp.188-193
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• 2014

Seed viability testing provides valuable information for assessing seed lot germinability. However, most testing methods require destruction of seed prior to test. Because the dissected seeds for viability test cannot be used further evaluation, the nondestructively X-ray photography technique that can be applied for the evaluation of seed quality has been developed. In order to know the validity and accuracy of X-ray photography technique in seed evaluation test that conducted to remove the abnormal seed from a seed lot, we have compared the results from tetrazolium viability test, germination test and X-ray contrast method in cotton. Metallic salts treatment increased the efficiency of X-ray photographic method by enhancing the penetration of X-ray in abnormal or damaged seeds rather than normal seeds that have strong and well-organized tissues in seed. Cotton seeds presoaked for 16 hr in distilled water followed by soaking into metallic salt solution (5% NaI in water) for 60 min were easily classified seeds into dead seed and viable seed based on the radiography images obtained by X-ray radiation. We concluded that soft X-ray photography was reliable to find out the various defective characters due to heat and mechanical damage of seeds.