• The Korean Journal of Financial Studies
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• v.7 no.1
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• pp.171-195
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• 2001

본 연구의 목적은 실물옵션이론을 바탕으로 정유회사의 가치평가기법을 제공하는 것이다. 정유회사는 가치평가를 위해서 회계적 가치외에 관리적 유연성(managerial flexibility)을 고려해야 하기 때문에 기존의 DCF방법을 적용하기 보다는 실물옵션방법을 이용하여야 한다. 관리적 유연성은 회사관리자가 적용가능한 생산관리적 기법으로서 회사의 미래현금흐름에 영향을 주고 따라서 회사의 가치에 영향을 미친다. DCF방법은 이러한 관리적 유연성을 적절히 고려하지 못하여 회사의 가치를 저평가하는 오류를 발생시킨다. 반면 실물옵션방법은 관리적 유연성을 가치평가에 있어서 주요 변수를 인식하기 때문에 정확한 가치평가의 수단이 된다. 옵션가격결정을 위한 기초자산은 크랙스프레드(crack Spread)이다. 크랙스프레드는 경유(heating oil)와 무연휘발유(unleaded gasoline)의 가격과 원유(crude oil) 가격의 차이를 나타내며 정유회사의 정유순익(gross refining margin)을 대표한다. 실물옵션방법에 의한 정유회사의 가치는 DCF방법에 의한 가치보다 두 배가 크다는 결론을 제시한다. 즉 관리적 유연성이 존재하는 회사의 경우는 가치평가에 있어서 실물옵션방법을 이용하여 가치를 저평가하는 오류를 범하지 않아야 한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.2
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• pp.161-168
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• 2013

Nowadays, one of the most interested area of automobile industry is the production of vehicle which has collision safety and ability to produce less amount of $CO_2$. The achievement of such a dual performance is done by choosing the materials like dual phase steel, ferrite bainite steel, etc. These steels have been used in automotive chassis and body parts, and also used to be formed by hole flanging to meet the goal of strength and design requirement. The formability of sheet material was experimented by hole expansion test and the judgement relies on human eye and his experience. This manual judgement involves many errors and large deviation. This paper develops the automatic crack recognition system which finds a crack based on CCD image to complement the problem of the current method depending on human's sense.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.4
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• pp.1289-1298
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• 2014

Pavement crack sealing method, which is one of the methods to maintain and repair the road, prevents the extending of cracks by repairing cracks in its early occurrence and has already been applied to many roadworks in advanced foreign country for a long time. But in the conventional crack sealing method, traffic accidents occur frequently during the repair because it's commonly performed on the heavy traffic road or highway. It also has some difficulties in securing the safety of workers from the risk of burns caused by heated sealant. In an effort to solve these problems, automated pavement crack sealing machines such as ARMM, OCCSM, TTLS have been developed in advanced foreign country since early 1990s. Also APCS in 2004 and ACSTM in 2013 were already developed domestically. However, since these automated crack sealers developed from a number of research institutions have different test-bed conditions and productivity measurement models, it's difficult to compare and evaluate them objectively. In this study, the image processing time of the respective machines and the movement time of each motion on the work process were estimated by using fully autonomous mapping and semi-automatic mapping in order to measure the productivity in the same environmental conditions. In addition, the productivity measurement test-bed reflected domestic road characteristics was designed to estimate and compare the productivity of the automated crack sealing machines.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.8
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• pp.1446-1450
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• 1992

A method of prediction for the fatigue life of surface crack, that is, initial cracks grow and penetrate through the thickness, was presented in the previous study of the authors. Effects of parameters such as the initial crack depth, material factors, etc., for the life were also discussed. However, in the case of adapting the concept of LBB(Leak Before Break), the break fatigue life after the penetration of the thickness must be taken into account. Hence, a method to predict the break fatigue life is presented in this paper. Effects of the parameters for the break fatigue life are discussed and compared with the penetration fatigue life.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.2
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• pp.151-157
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• 2004

Ultrasonic testing is a kind of nondestructive test to detect a crack or discontinuity in materials or on material surfaces by sending ultrasound to it. This conventional ultrasonic technique has some limitations in reliably detecting crack or accurately assessing materials in the case of complex-shaped power plant components such as a turbine blade root. An alternative method for such a difficult inspection is highly needed. In this study, application of a phased array ultrasonic testing (UT) system to a turbine blade, one of the critical power plant components, has been considered, and the particular incident angle has been determined so that the greatest track detectability and the most accurate crack length evaluation nay be achieved. The response of ultrasonic phased array was also analyzed to establish a special method to determine the track )ength without moving the transducer. The result showed that the developed method for crack length assessment is a more accurate and effective method, compared with the conventional method.

• The Journal of Korean Institute of Information Technology
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• v.17 no.9
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• pp.99-112
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• 2019

Cracks on pavement surfaces are critical signs and symptoms of the degradation of pavement structures. Image-based pavement crack detection is a challenging problem due to the intensity inhomogeneity, topology complexity, low contrast, and noisy texture background. In this paper, we address the problem of pavement crack detection and segmentation at pixel-level based on a Deep Neural Network (DNN) using gray-scale images. We propose a novel DNN architecture which contains a modified U-net network and a high-level features network. An important contribution of this work is the combination of these networks afforded through the fusion layer. To the best of our knowledge, this is the first paper introducing this combination for pavement crack segmentation and detection problem. The system performance of crack detection and segmentation is enhanced dramatically by using our novel architecture. We thoroughly implement and evaluate our proposed system on two open data sets: the Crack Forest Dataset (CFD) and the AigleRN dataset. Experimental results demonstrate that our system outperforms eight state-of-the-art methods on the same data sets.

• Journal of Ocean Engineering and Technology
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• v.5 no.2
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• pp.216-216
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• 1991

• Elastomers and Composites
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• v.47 no.4
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• pp.336-340
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• 2012

Residual stress in the injection molded part is originated from thermal shrinkage and shear stress during injection molding process. There are many measurement methods of residual stress in the plastic part. Residual stress in opaque products can be measured by chemical cracking test. This method enables the solvent and specimen to react and to cause cracks. Cracks developed according to the level of residual stress. Thus the stresses in plastic part can be quantitatively measured by counting the number of cracks or measuring the size of cracks. Relationship between stress and number of cracks in a plastic specimen has been investigated in this study. Bergen jig was used to give a strain in the specimens those were molded using PC/PBT and PC/ABS. Solvent for the chemical cracking test was prepared using tetrahydrofuran and methyl alcol with the ratio of 1 to 3. Stresses in the specimen can be calculated by strains those were imposed by Bergen jig. Cracks were developed for stress higher than certain level. The number of cracks increased by second order function for stress.

• Journal of Ocean Engineering and Technology
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• v.5 no.2
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• pp.76-84
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• 1991

본 연구는 피로수명 평가를 위한 새로운 파괴역학적 parameter의 확립에 관한 연구이다. 실질적으로 피로파괴가 일어나는 피로 균열선단의 국소영역에서 변형분포를 미소원형격자측정법을 이용하여 실험적으로 명확히 밝혀내었다. 그리고 이 결과를 기초로 하여 국소피로 변형율장을 대표할 수 있는 피로변형율 확대계수 $\Delta$A를 제안하였다. 또한 새로운 parameter $\Delta$A의 유효성을 여러 피로조건에서 검토한 결과, 균열선단 국소 영역에서 피로 변형율 확대계수 $\Delta$A에 의하여 피로 균열전파 속도평가를 일의적으로 나타낼 수 있음을 확인하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2391-2397
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• 1993

The distribution of fatigue crack growth rate is influenced by the measuring interval and methods of calculation of crack growth rate. The purpose of this paper is to suggest a method for the evaluation of crack growth rate distribution without the influence. The constant ${\Delta}P$ test and the constant .DELTA.K test are executed by using the CT specimen. The measuring interval of (${\Delta}a$/W=0.0067~0.014) crack length is not affected by methods of the calculation of the fatigue crack growth rate is suggested.