• 한국추진공학회지
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• 제10권2호
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• pp.102-109
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• 2006

본 논문에서 항공기용 터보 축 엔진의 결함 진단 알고리즘을 개발하기 위해 Support Vector Machine(SVM)과 인공신경망(ANN)을 이용하였다. 신경망을 이용한 시스템은 비선형성이 과도한 데이터를 학습할 때 지역 최소점(Local Minima)에 빠져 분류 정확률이 낮아질 수 있다. 이러한 위험성을 보안하기 위해 SVM에 의한 ANN의 분할 학습 알고리즘(SLA)을 제안하였다. 이것은 SVM을 이용하여 결함 위치를 판별 한 후 신경망이 선택적으로 학습을 하는 방법으로 학습 데이터의 비선형성을 줄여 분류 정확률을 높이기 때문에 신경망을 단독으로 사용할 때보다 개선된 성능을 보여주었다.

• 한국재료학회지
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• 제12권5호
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• pp.359-362
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• 2002

DBPAS has been used to characterize atomic level defect structures in materials. In this investigation the numerical analysis of the Doppler spectra was restricted to the determination of the shape parameter, S, defined as the ratio between the total amount of counts in a central portion of the spectrum and the total amount of counts. As samples were exposed by X-ray increasing from 3, 6, and 9 Gy with 6 MV, and 10 MV each and also by E-beam increasing the energies with 6 MeV, 9 MeV, 12 MeV, and 20 MeV. The S-parameter values were increased as increasing the exposed time and the energies. The S-parameters of the large and small size grains in $CaWO_4$ were measured. The S-parameter of the small size grains in $CaWO_4$ was resulted in larger values.

• Journal of Yeungnam Medical Science
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• 제12권1호
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• pp.105-112
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• 1995

During the period of 9.5 years from September, 1985 to March, 1995, 32 cases with spontaneous closure in simple ventricular septal defect(VSD) were observed and evaluated at Yeungnam University Hospital, and those were confirmed by 2D-echocardiogram. The results were as follows: 1. Among these 32 cases, there were 23 cases(71.9%) of perimembranous VSD, 8 cases(25.0%) of muscular VSD and 1 case(3.1%) of subarterial VSD. Septal aneurysms appears to be main mechanism of spontaneous closure of VSD because of the presence of septal aneurysm in all cases with spontaneous closure of a perimembranous VSD. 2. The size of the defect was variable in diameter, but 27 cases(81.2%) were less than 5 mm. 3. The mean age was 12.1 months at spontaneous closure with the range from 1 month old to 72 months. 4. The mean weight was 9.0 kg at spontaneous closure. 5. Among these 32 cases, 3 cases had the clinical evidence of cardimegaly or congestive hert failure during infancy. 6. Male to female sex ratio was 1.5:1.

• 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.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2022년도 추계학술발표대회
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• pp.625-627
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• 2022

In the construction and development of modern industrial production technology, the traditional technology management mode is faced with many problems such as low qualification rates and high application costs. In the research, an improved workpiece defect detection method based on deep learning is proposed, which can control the application cost and improve the detection efficiency of irregular defects. Based on the research of the current situation of deep learning applications, this paper uses the improved Faster R-CNN network structure model as the core detection algorithm to automatically locate and classify the defect areas of the workpiece. Firstly, the robustness of the model was improved by appropriately changing the depth and the number of channels of the backbone network, and the hyperparameters of the improved model were adjusted. Then the deformable convolution is added to improve the detection ability of irregular defects. The final experimental results show that this method's average detection accuracy (mAP) is 4.5% higher than that of other methods. The model with anchor size and aspect ratio (65,129,257,519) and (0.2,0.5,1,1) has the highest defect recognition rate, and the detection accuracy reaches 93.88%.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.919-924
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• 2001

The purpose of this study is to prepare the basic data for the development of building board with expanded perlite. Each paste was mixed with four levels of water cement ratio(30, 40, 50, 60%), and expanded perlite was substituted with four levels of substitutive ratio(20, 40, 60, 80%) for the each paste. The physical property, compressive strength, bending strength and thermal conductivity of each cement composite which is made through previously described method were analyzed and the result was as follow. In the case of 80 percent substitutive ratio, the cement composite had a mechanical defect which was resulted from lack of paste content. In the case of 40 and 60percent substitutive ratio, the cement composite had sufficient strength, light weight and low thermal conductivity for application to fire resisting board.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2017년도 춘계학술대회 논문집
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• pp.142-142
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• 2017

High Flory-Huggins interaction parameter (${\chi}$)를 가지는 polystyrene-block-dimethylsiloxane (PS-b-PDMS)는 초미세 패턴 제작과 우수한 defect density, 우수한 edge roughness 특성으로 향상된 패턴을 제공한다는 점에서 반도체 분야에서 많은 연구가 되고 있다. 하지만, PS와 PDMS 사이에 존재하는 큰 surface tension의 차이로 인해 PDMS는 PS와 air 사이에서 segregate되기 때문에 수직배향에 불리하여 high aspect ratio (HAR)을 가지는 cylinder, lamellar 패턴 제작에 있어 큰 어려움을 가진다. 본 연구에서는 이러한 문제를 해결하기 위해, PS-b-PDMS BCP 패턴과 하부 실리콘 기판 사이에 amorphous carbon layer (ACL)를 삽입하여 효과적으로 pattern transfer하는 공정을 연구하였다. 플라즈마를 이용하여 무한대에 가까운 etch selectivity를 가지는 식각 공정을 개발함으로써 낮은 aspect ratio를 가지는 PS-b-PDMS BCP 패턴의 한계점을 극복하였다. Large-x value를 가지는 BCPs를 이용하여도 매우 높은 aspect ratio를 가지면서 동시에 pattern quality를 향상시킬 수 있는 plasma process를 제시하였다.

• Journal of Chest Surgery
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• 제13권4호
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• pp.418-421
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• 1980

During the period from August 1959 to end of July 1980, 69 cases of Type I VSD were noted among 235 cases of ventricular septal defect who were operated utilizing cardiopulmonary bypass in the Department of Cardio-thoracic Surgery, College of Medicine, Seoul National University(29.4%). During the same period 1162 open heart surgery cases were experienced among whom 778 cases were congenital anomalies. There were no significent differences between Type I '||'&'||' other tvpo:s of VSD in sex and age distribution. In Type I VSD frequency of aortic regurgitation association was much higher than rest of the types. (8.7% to 2.6%). Necessity of patch closure in Type I was not different from other types. The high incidence of Type I VSD is quite similar to Japanese references which show quite higher ratio compared with from Euroamerican caucasian patients materials. All cases were operated on with bubble type oxygenator mainly Shiley**" oxygenator utilizing hypothermic hemodilution perfusion technique.echnique.

• Journal of Chest Surgery
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• 제14권1호
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• pp.9-16
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• 1981

Twenty eight patients with conpnital heart disuse underwent lung biopsy to assets pulmonary obstructive vascular disease at cardiac surpry. Thirteen patients had patent ductus arteriosus, 10, ventricular septal defects and S, atrial septal defects. The aaes were between 2 and 30 years. In patients with patent ductus arteriosus lung biopsy was performed from the IIngular Hlment. The anterior seament of the right upper lobe was blopsled in cases with ventricular septal defect and atrial septal defect. Grading of pulmonary obstructive vascular disease could not be assessed In 9 cases. In 2 cases poor quality of the slides made us impossible to evaluate and In 7 cases there were no suitable small muscular arteries to evaluate in the slides of lung tissue especially taken from the IIngular seament. Nineteen cases were evaluated pulmonary obstructive vascular disease. Among them 17 cases had Heath-Edwards changes of grade 1 and 2 patients had that of grade 3. The thickness of media was measured. It was expressed as percentage of medial thickness to outer diameter of artery. The medial thickness was correlated proportionally with elevation of pulmonary arterial pressure and pulmonary vascular resistance to systemic vascular resistance ratio. There were no complications related to the procedure of lung biopsy.

• 한국소음진동공학회논문집
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• 제13권5호
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• pp.400-408
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• 2003

This paper investigates the vibration characteristics of steam generator (SG) U-tubes with defect. The operating SG shell-side flow field conditions for determining the fluidelastic instability parameters such as added mass are obtained from three-dimensional SG flow calculation. Modal analyses are performed for the U-tubes either with axial or circumferential flaw with different sizes. Special emphases are on the effects of flaw orientation and size on the modal and instability characteristics of tubes, which are expressed in terms of the natural frequency, corresponding mode shape and stability ratio. Also, addressed is the effect of the internal pressure on the vibration characteristics of the tube.