• 상하수도학회지
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• 제27권6호
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• pp.731-741
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• 2013

CCTV inspection method has been used in Korea for more than 20 years, but there is no proper assessment system for sewer failure severity that considers the domestic circumstances. This study classified the defects caused by the overburden load of reinforced concrete sewer pipes depending on severity and developed defect code by analyzing the domestic CCTV inspection videos. The defect score was assigned to each defect code, and it was classified into 5 grades for the decision-making of repair and rehabilitation. The result of this study is expected to be useful for domestic CCTV inspectors to assess the sewer condition and helpful for managers to make a decision of repair and rehabilitation.

• 한국컴퓨터정보학회논문지
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• 제20권5호
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• pp.73-81
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• 2015

소프트웨어 결함 예측 연구들의 대부분은 입력 개체의 결함 유무를 예측하는 이진 분류 모델들에 관한 것들이다. 하지만 모든 결함들이 같은 심각도를 갖지는 않으므로 예측 모델이 입력 개체의 결함경향성을 몇 개의 심각도 범주로 분류할 수 있다면 훨씬 유용하게 사용될 수 있다. 본 논문에서는 전통적인 복잡도와 크기 메트릭들을 입력으로 하는 심각도 기반 결함 예측 모델을 제안하였다. 학습 알고리즘은 많이 사용되는 네 개의 기계학습 기법들을 사용하였으며, 모델 구조는 삼진 분류 모델로 하였다. 모델 성능 평가를 위해 실험 데이터는 두 개의 NASA 공개 데이터 집합을 사용하였고, 평가 측정치는 Accuracy를 이용하였다. 평가 실험 결과는 역전파 신경망 모델이 두 데이터 집합에 대해 각각 81%와 88% 정도의 Accuracy 값으로 가장 좋은 성능을 보였다.

• Steel and Composite Structures
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• 제29권5호
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• pp.647-657
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• 2018

Geometric imperfections may be created during the production process or setting borders of single-layer graphene sheets (SLGSs). Vacancy defects are an instance of geometric imperfection, so investigating the effect of these vacancies on the mechanical properties of single-layer graphene is extremely important. Since very few studies have been conducted on the structure of imperfect graphene (with the vacancy defect) as an anisotropic structure, further study of this defective structure seems imperative. Due to the vacancy defects and for the proper assessment of mechanical properties, the graphene structure should be considered anisotropic in certain states. The present study investigates the effects of site and size of vacancy defects on the mechanical properties of graphene as an anisotropic structure using the lekhnitskii interaction coefficients and Molecular Dynamic approach. The effect of temperature on the severity of the SLGS becoming anisotropic is also investigated in this study. The results reveal that the amount of temperature has a big effect on the severity of the structure getting anisotropic even for a graphene without any defects. The effect of aspect ratio, temperature and also size and site of vacancy defects on the material properties of the graphene are studied in this research work. According to the present study, using material properties of flawless graphene for imperfect structure can lead to inaccurate results.

• 한국해양공학회지
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• 제27권3호
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• pp.61-66
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• 2013

This paper presents the results of finite element simulations of elastic wave propagation in an underwater steel plate and the verification of a proposed method utilizing elastic wave-based damage detection. For the simulation and verification, we carried out the following procedures. First, three-dimensional finite element models were constructed using a general purpose finite element program. Second, two types of damages (mechanical defects and deteriorations) were applied to the underwater steel plate and three parameters (defect location, defect width, and depth) were considered to adjust the severity of the applied damages. Third, elastic waves were generated using the oblique incident method with a Gaussian tone burst, and the response signals were obtained at the receiving point for each defect or deterioration case. In addition, the received time domain signals were analyzed, particularly by measuring the magnitudes of the maximum amplitudes. Finally, the presence and severity of each type of damage were identified by the decreasing ratios of the maximum amplitudes. The results showed that the received signals for the models had the same global pattern with minor changes in the amplitudes and phases, and the decreasing ratio generally increased as the damage area increased. In addition, we found that the defect depth was more critical than the width in the decrease of the amplitude. This mainly occurred because the layout of the depth interfered with the elastic wave propagation in a more severe manner than the layout of the width. An inverse analysis showed that the proposed method is applicable for detecting mechanical defects and quantifying their severity.

• 국제학술발표논문집
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• The 9th International Conference on Construction Engineering and Project Management
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• pp.213-221
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• 2022

Defects are the risk factors in the construction process of buildings. They cause damage, delaying the construction duration. They especially cause adverse effects on the top-down construction method. This study analyzed the degree of construction delay induced by each work type, focusing on defects in the top-down method. Then, we derived construction delay induction coefficient from different work types in order by using the severity of construction delay per defect and the occurrence probability of defect; this assessment model measures the impact of defects on construction delay for each work type. Furthermore, by comparing each work type based on the defect frequency and the construction delay induction coefficient, we found work types that need to be administered attentively. We identified that plastering work was easy to overlook, requiring caution in defect management. This study provides an efficient defect management system suitable for the buildings that are built using the top-down construction method.

• 한국산학기술학회논문지
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• 제20권3호
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• pp.56-64
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• 2019

공동주택 하자는 추가적으로 투입되는 각종 자원의 낭비, 경제적 비용손실로 연결되며, 입주자들에게는 시간적, 물질적, 정신적 피해를 주고, 기업에게는 금전적인 손실뿐만 아니라 기업 신용도를 추락하는 문제를 발생시킨다. 이러한 관점에서 본 연구에서는 다수의 하자분쟁 사례를 활용하여 공동주택 공종/하자유형/부위에 대하여 하자 빈도 및 심각도를 고려한 중요도를 산출하여 공동주택 하자관리 효율성을 제고하고, 하자분쟁을 최소화하는데 기여하고자 한다. 이를 위하여 본 논문에서는 공동주택 하자분쟁사례 48건, 약 7,548개의 하자항목 자료를 토대로 분석을 실시하였다. 분석 결과를 정리하면, 하자가 주로 발생하는 공종은 RC, 마감, MEP 공종이며, 중요도가 높은 하자유형은 균열, 누수, 오시공, 미시공 등인 것으로 확인되었다. 또한 하자부위의 경우 상대적으로 현장 설치 중심의 가구, 설비기기보다 현장 시공 중심의 외벽, 내벽, 내부 천장 및 바닥이 하자 중요도가 높은 것으로 확인되었다. 이에 따라 기본적으로 생애주기 각 단계별 품질관리를 철저히 할 필요도 있지만, 내부공간을 구성하는 부위의 경우, Pre-fabrication에 대한 활용성을 높이는 것을 고려할 필요가 있다.

• Journal of Chest Surgery
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• 제19권1호
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• pp.25-34
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• 1986

Recently, radionuclide angiocardiogram is one of the most common procedure for assessment of ventricular performance due to its distinctive advantages such as safety, accuracy, and ease of repeated studies. Also, measurement and comparison between pre and postoperative left ventricular ejection fraction [LVEF] are meaningful for assessing the severity of myocardial damage which occurred during open heart surgery and the status of myocardial recovery. We obtained pre and post operative LVEF using radionuclide angiocardiogram on 30 patients composed of atrial septal defect, ventricular septal defect, cyanotic congenital heart disease, and valvular heart disease who undergone the open heart surgery from March to august 1984. The study revealed that ventricular septal defect and mitral valvular heart disease showed 8.1% and 6.2% decreases of postoperative LVEF, respectively. But, there are little increases of postoperative LVEF in the atrial septal defect and cyanotic congenital heart disease. In ventricular septal defect, each group of Qp/Qs over 2.0 and systolic pulmonary artery pressure over 50mmHg showed significant 17% and 14.7% decreases of postoperative LVEF, respectively. Considering the duration of the aortic cross clamping times and closing methods of VSD, each group of duration over 30 min. and of patch closure showed 13.9% and 14.2% decreases of LVEF between pre and postoperative status respectively which was significant finding statistically.

• Journal of Preventive Medicine and Public Health
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• 제29권3호
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• pp.521-527
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• 1996

한식(韓式) 2중 15색상 배열기는 다른 색각검사표로 색각 이상이 발견된 사람들에서 색각이상의 분류와 그 정도를 구분하여 직업 및 사회 적성검사로 이용되고 있다. 그러나 색각이상의 분류와 정도의 판정을 2중 색상 배열기의 기록용지에 그린 색채의 착오를 기초로 정성적으로 평가하기 때문에, 수학적인 분석을 위한 적절한 정량적인 점수를 얻을 수는 없다. 이 논문은 대상자들의 색채착오를 기초로 한식(韓式) 2중 15색상 배열기의 정량적인 점수화 방법을 위한 새로운 제안이다. 이 프로그램을 이용하면 많은 2중 15색상 배열검사 결과들을 쉽고 빠르게 조작할 수 있고, 특정한 형태의 색각이상 정도를 집단간 비교할 수 있으며, 질병경과가 다양한 후천성 색각이상을 지속적으로 감시할 수 있도록 도움을 준다.

• 한국인터넷방송통신학회논문지
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• 제18권3호
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• pp.151-157
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• 2018

소프트웨어 결함 예측에 관한 기존의 연구들은 대부분 모델의 입력 모듈이 결함을 가지고 있는지 여부를 판단하는 이진 감독형 분류 모델들에 관한 것들이었다. 하지만 이진 분류 모델은 결함의 복잡한 특성들을 고려하지 않고 단순히 입력 모듈의 결함 유무만을 판단한다는 문제점이 있고, 감독형 모델은 대부분의 개발 집단이 보유하고 있지 않은 훈련 데이터 집합을 필요로 한다는 한계점이 있다. 본 논문은 이러한 두 가지 문제점을 해결하기 위해 비감독형 알고리즘을 사용한 심각도 기반 삼진 분류 모델을 제안하였으며, 평가 실험 결과 제안 모델이 감독형 모델들에 필적하는 예측 성능을 보였다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.305-306
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• 2002

In this paper, the endurance life of the rolling bearings with defective balls and their failure (flaking) phenomena are presented. It was found that the lives of ball bearings with defective balls were shorter than that of calculated L10 life as well as that of normal bearings in spite of the using standard bearing components. Although the bearings were assembled with defective balls, whereas the other parts were qualified new ones, the main failures were occurred on the inner ring raceways. Moreover, the failures were on the center of the groove curvature and the severity of failure is similar to the order of initial defect depth of the balls. These shows that the defects on the bearings can affect the life of tribologically contacted mating parts.