• Journal of the Korea institute for structural maintenance and inspection
• /
• v.12 no.2
• /
• pp.75-82
• /
• 2008

There are almost 18,000 dams including about 1,200 large dams in Korea. The large dams are well operated and maintained by KWATER(Korea Water Resource Corporation), KRC(Korea Rural Community & Agriculture Corporation) and KHNP(Korea Hydro & Nuclear Power Co., Ltd.). Several research reports concern with the safety of these large dams are presented but there is no paper concerned with small dams which has diversion tunnel through the dam body. The purpose of this study is to show the common defects of small dams according to various cases of degradation of dams and the repair and retrofit methods which applied to the damaged dams. And this study performed resistivity survey to evaluate the effect of retrofitting dam. Also, this study tries to present the solution which concerned with these common defects in maintenance and design steps.

• The Journal of Bigdata
• /
• v.7 no.2
• /
• pp.31-41
• /
• 2022

Steel is one of the most fundamental components to mechanical industry. However, the quality of products are greatly impacted by the surface defects in the steel. Thus, researchers pay attention to the need for surface defects detector and the deep learning methods are the current trend of object detector. There are still limitations and rooms for improvements, for example, related works focus on developing the models but don't take into account real-time application with practical implication on industrial settings. In this paper, a real-time application of steel surface defects detection based on YOLOv4 is proposed. Firstly, as the aim of this work to deploying model on real-time application, we studied related works on this field, particularly focusing on one-stage detector and YOLO algorithm, which is one of the most famous algorithm for real-time object detectors. Secondly, using pre-trained Yolov4-Darknet platform models and transfer learning, we trained and test on the hot rolled steel defects open-source dataset NEU-DET. In our study, we applied our application with 4 types of typical defects of a steel surface, namely patches, pitted surface, inclusion and scratches. Thirdly, we evaluated YOLOv4 trained model real-time performance to deploying our system with accuracy of 87.1 % mAP@0.5 and over 60 fps with GPU processing.

• The Journal of the Convergence on Culture Technology
• /
• v.10 no.1
• /
• pp.585-590
• /
• 2024

In this study, rail surface defects are increasing due to the aging of urban railway rails, but in the detailed guidelines for track performance evaluation established by the country, rail surface damage is inspected with the naked eye of engineers and simple measuring tools. With the recent enactment of the Track Diagnosis Act, a large budget has been invested and the volume of rail diagnosis is rapidly increasing, but it is difficult to secure the reliability of diagnosis results using labor-intensive visual inspection techniques. It is very important to discover defects in the rail surface through periodic track tours and visual inspection. However, evaluating the severity of defects on the rail surface based on the subjective judgment of the inspector has significant limitations in predicting damage inside the rail. In this study, the rail internal crack characteristics due to rail surface damage were studied. In field measurements, rail surface damage locations were selected, samples of various damage types were collected, and the rail surface damage status was evaluated. In indoor testing, we intend to analyze the correlation between rail surface defects and internal defects using a electron scanning microscope (SEM). To determine the crack growth rate of urban railway rails currently in use, the Gaussian probability density function was applied and analyzed.

• 한국항공운항학회:학술대회논문집
• /
• 2015.11a
• /
• pp.257-260
• /
• 2015

국적기의 사고 및 국내에서 발생한 사고를 분석해보면 많은 인명 피해가 발생된 사고의 유형들을 접할 수 있다. 운항중인 항공기에 특별한 결함이 없었음에도 불구하고 조종사의 잘못된 판단에 의한 사고는 선행연구들의 결과와 같이 많은 부분들을 차지하고 있다. 특히 비 정밀접근(Non Precision Approach)의 선회접근(Circling Approach) 및 시계접근(Visual Approach)절차에서 자주 발생되는 지상충돌 사례들을 과학적이고 객관적인 방법을 바탕으로 분석하여 유사사고 재발 방지를 위한 대안을 찾고자 한다. 이를 위해 조종사의 입장에서의 교육 및 절차에 관해 분석하여 비 정밀 접근 절차 수행의 기준을 제언하고자 한다.

• Proceedings of the Korean Society of Fisheries Technology Conference
• /
• 2001.05a
• /
• pp.77-78
• /
• 2001

선박으로부터 발생하는 해양사고는 귀중한 인명과 재산은 물론 사고 선박으로 부터 배출된 유류와 폐기물 등의 유해물질은 주변어장을 황폐화시킬 뿐만 아니라 해양생물을 멸종시키는 해양오염원이 되고 있다. 해상에서 발생하는 해양사고는 항행중 태풍이나 폭풍 등을 만나 선박이 침몰하거나 전복되는 불가항력적인 자연 재해와 선박의 구조와 설비 등의 선체 결함에 의한 요인도 있으나, 최근의 해양사고는 그 선박을 조종하고 관리하는 승무원의 항해 부주의나 직무태만, 항해정보의 부정확과 운항기술의 미숙등 인적과실에 의해 발생하는 선박해양사고가 대부분을 차지하고 있다. (중략)

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
• /
• 2008.11a
• /
• pp.165-172
• /
• 2008

Leakage incidents due to the fault of hazmat tank foundations are likely to cause the tremendous fire disaster in the national industry cluster area. The proper design and construction of tank foundation should be required to prevent the tank fire. In the study, the types of typical tank foundations were classified and modeling the individual tank type for 3D FEM analysis was performed to suggest the guideline for the design and construction of tank foundations. Matters to be attended of the foundation design and construction are reviewed through the comparison assessment of the numerical analysis results of the foundation types.

• Journal of Korea Multimedia Society
• /
• v.17 no.2
• /
• pp.170-179
• /
• 2014

Recently the U-Healthcare system has been rapidly advanced to manage emergence rescue for seniors. We can access emergency rescue systems with high quality services anytime, anywhere under ubiquitous healthcare systems. The more the various systems develop, the more software security systems become important. Therefore, the safety-critical system has been widely spread to the world by advancement of the information and communication technologies. There are a lot kind of fault analysis methods to evaluate software security systems. However due to characteristics of software that is not applied by human error, it can be prevented the enormous damages and losses from improving the safety of safety-critical system. So this paper proposes an integration method of FTA and Forward and Backward FMECA. This method has each strength of FTA and FMECA which is visual and numeric in normalization. First, by use of FTA, we can redraw FTA with Forward FMECA and Backward FMECA in consideration of occurrence, severity, detection, correctness, robustness, and security. Also according to value of NRVP at each event, we can modify FTA diagrams as shown critical paths given by severity and occurrence. Also, we propose the improved emergency rescue service platform of ubiquitous healthcare systems through identifying priorities of the criticality according to normalized risk priority values (NRPV).

• Journal of Digital Convergence
• /
• v.11 no.2
• /
• pp.115-125
• /
• 2013

Unexpected consumer dissatisfaction emerges through rapid growth and expansion of on-line shopping channel. This research focused on the fashion online retail channels' negative aspect caused by service failure which possibly disappointed consumers. We also tried to seek for appropriate service recovery types based on frequently offered recovery types on-line. Data from college students were analyzed. Results indicate that fitting problem, insufficient information, product defect, inventory problem and slow delivery were the main service failure types in apparel e-shopping. Regression analysis identified that among these types, insufficient information, product defect, and slow delivery had significant influence on channel satisfaction after post recovery effort. Results also confirmed significant relationships between channel satisfaction and channel switching. Consumers perceived benefit level causes overall channel satisfaction level to rise while perceived risk leads to lower level of channel satisfaction. Choosing desirable service recovery activities in each service failure situations is necessary in order to raise consumer's channel satisfaction in online apparel shopping.

• Proceedings of the Korea Technology Innovation Society Conference
• /
• 2017.05a
• /
• pp.71-79
• /
• 2017

조종사가 탑승하지 않고도 지정된 임무를 수행할 수 있도록 제작된 무인항공기(드론)가 다양한 장비(광학, 적외선, 레이더 센서 등)를 탑재하여 활용되고 있다. 지금까지는 국가안보 유지 수단으로서 감시 정찰 정밀공격무기의 유도 등의 임무를 수행하여 왔다. 최근에는 민간부문에서도 다양한 용도로 활용되고 있어서 정부(국토교통부 산업통상자원부)는 무인항공기의 국내경제발전의 파급효과를 인지하고, 세계 무인항공기시장에서 우선순위를 선점하기 위해 투자확대를 기해 왔다. 무인항공기시장이 산업발전과 고용촉진에 도움이 되어 국내경제에 긍정적인 효과가 많다고 하더라도 무인항공기의 안전운행을 담보할 다양한 법적 제도적인 장치의 마련이 필요하다. 따라서 무인항공기로 야기되는 다양한 유형의 사고를 검토하여 이에 대한 법적 책임에 대한 분석이 필요하다. 무인항공기의 사고는 운영자의 운영상의 과실로 인한 사고도 있고 무인항공기 자체의 결함으로 인한 사고도 발생할 수 있다. 또한 운행자의 고의과실로 인한 타인의 권리(프라이버시권 등)를 침해하는 경우나 무인항공기끼리의 충돌사고도 발생할 수 있다. 이러한 사고로 인한 책임은 민사책임으로서 대부분 지상 제3자에 대한 생명 신체 또는 재산상의 손해배상책임이다. 이러한 책임을 규율하는 국제협약으로 로마협약이 있지만 체약국이 없기 때문에 국제협약으로서의 역할을 못하고 있다. 따라서 현재로서는 각국의 국내법에 의하여 해결될 가능성이 많을 것으로 생각된다. 무인항공기 운영자의 과실로 인한 사고는 민법이나 상법이 적용될 수 있고, 무인항공기의 제작결함으로 인해 사고가 발생하였을 경우와 시스템의 오작동으로 인해 사고가 발생하였다면 제조물 책임을 물어야 할 경우도 있을 수 있다. 이러한 법적 쟁점에 대한 검토를 통하여 무인항공기 공급과 활용의 확대로 인한 다양한 사고발생과 책임범위를 명확히 하여 사고당사자들의 책임관계를 인식시키는 것이 필요하다.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.3 no.2
• /
• pp.23-32
• /
• 2001

Rock masses are usually discontinuous in nature, as a result of various geological processes they have underdone and they contain rock joints and bridges. Crack propagation and coalescence processes mainly cause rock failures in tunnels. In this study, we focused on the crack initiation, propagation and coalescence process of rock materials containing two pre-existing open cracks arranged in different geometries. During uniaxial compression, wing crack initiation stress, wing crack propagation angle, and crack coalescence stress of Diastone gypsum and Yeosan Marble specimens were examined. And crack initiation, propagation, and coalescence processes were observed. Shear, tensile and mixed (shear+tensile) types of crack coalescence occurred. To compare the experimental results with Ashby & Hallam model, crack coalescence stress was normalized and it generally agreed with the experimental results.