초음파 DAC 기법을 이용한 압력용기 용접부의 지시 크기측정 정확도 평가

김재동,임형택,도의순,Kim, Jae Dong,Lim, Hyung Taik,Doh, Eui Soon 한국압력기기공학회 2015 한국압력기기공학회 논문집 Vol.11 No.2

During refueling Outage, In-service inspections(ISIs) for the Nuclear Power Plant components are mandatory requirement in accordance with ASME Code Sec. XI. Especially, in current ultrasonic testing is one of the most important NDT techniques that are used for volumetric examination methods for nuclear power plant components, and accurate sizing of flaw indication by UT is essential to assure the integrity of the components. However, ASME code specifies minimum requirement for vessel examination procedure, and so far many different flaw sizing approaches have been tried to apply. Through the Round Robin Test(RRT), the accuracy of ultrasonic flaw sizing using DAC techniques was measured with the mock-ups simulating typical pressure vessel welds. These mock-ups contain artificially introduced flaws of known size and location. This paper shows experimental comparison data on the accuracy of techniques using such as 6dB drop, 50%DAC, 20%DAC and 20%DAC with beam spread correction, and also shows that diverse DAC techniques can be effectively applied to the assessment of the flaw sizing for pressure vessel welds in the stage of welding and fabrication.

IP 역추적 기술을 이용한 능동형 보안 시스템

김재동,채철주,이재광,Kim, Jae-Dong,Chae, Cheol-Joo,Lee, Jae-Kwang 한국정보통신학회 2007 한국정보통신학회논문지 Vol.11 No.5

최근 기술의 발전으로 인해 인터넷이 정보화사회의 기반이 되는 기술로 발전하고 있는 반면 역기능인 해킹, 바이러스, 정보변조 등과 같은 기술 또한 발전하고 있다. 이러한 역기능에 대응하기 위해 방화벽(Firewall), 침입탐지시스템(Intrusion Detection System) 등과 같은 보안 시스템이 개발되었지만 해킹 사고는 꾸준히 증가하고 있다. 기존의 이러한 수동적인 보안 시스템은 능동적인 시스템으로 발전되었다. 이에 본 논문에서는 IP 역추적 기술을 이용한 능동적 보안 시스템을 제안한다. IP 역추적을 위해 ICMP 형태의 역추적 메시지를 구현하고 지역 네트워크에 배치되는 에이전트와 관리 네트워크에 배치되는 서버 프레임워크를 설계하고, 이러한 능동형 보안 시스템을 기반으로 네트워크 기반의 침입자를 추적하고 고립화하기 위한 보안 메커니즘을 구현한다. There is a tremendous increase in the growth of Internet making people's life easy. The rapid growth in technology has caused misuse of the Internet like cyber Crime. There are several vulnerabilities in current firewall and Intrusion Detection Systems (IDS) of the Network Computing resources. Automatic real time station chase techniques can track the internet invader and reduce the probability of hacking Due to the recent trends the station chase technique has become inevitable. In this paper, we design and implement Active Security system using ICMP Traceback message. In this design no need to modify the router structure and we can deploy this technique in larger network. Our Implementation shows that ICMP Traceback system is safe to deploy and protect data in Internet from hackers and others.

2차원 이송-확산모형을 이용한 취수장 인근에서의 오염물질의 혼합거동 모의

김재동,김영도,류시완,서일원,Kim,Jae-Dong,Kim,Young-Do,Lyu,Si-Wan,Seo,Il-Won 한국방재학회 2008 한국방재학회 학술발표대회논문집 Vol.2008 No.1

하천에 위치하는 취수장의 수질관리에 있어서 오염물질의 이송-확산은 주요 관심사다. 오염물 이송에 관한 연구를 위해서는 하천의 사행에 따른 영향과 지류의 유입에 따른 혼합에 대해서 분석이 수행되어져야 한다. 본 연구의 목적은 낙동강 하류에 위치한 물금취수장 부근에서의 오염물의 혼합거동을 모의하고자 하였다. 물금취수장은 부산광역시의 음용수로써 이용되고 있으며, 물금취수장 인근에서의 흐름은 인근의 지천의 유입과 본류 유량, 그리고 하류단에 위치한 하구둑 수문개폐 여부의 영향을 받는다. 수문은 10개의 수문으로 구성되며, 평상시에는 조위에 따라서 보조수문을 개방하고 유량이 증가할 때 주수문을 함께 개방한다. 취수장 맞은편인 본류의 우안에는 지류인 대포천이 위치하는데 지류에서 발생한 오염물질은 취수장 인근에 흐름형태에 따라 취수구로 유입되기도 한다. 본 연구에서는 2차원 수치해석 결과를 바탕으로 오염사고에 대비한 적절한 취수장 운영방안을 제시하고자 하였다. The transport and dispersion of pollutants in natural river is a principal issue in intake station management. To study the pollutant transport in natural rivers, the effect of meandering and confluence of tributary on mixing process have to analyzed. The objective of this study is to simulate the mixing and transport of pollutants for operating water gate of Nakdong Estuary Barrage around the intake station. Mulgeum intake station being used as drinking water sources for Pusan. The flow around the intake station is influenced by operating water gate of Nakdong Estuary Barrage which is located downstream. The water gate system includes ten individual gates. The minor gate is usually opened according to elevation of the sea. When the river flow increases, the main water gate is opened. Daepo stream, tributary of the Nakdong river, is on opposite side of the intake station. The pollutants from Daepo stream often flows into the intake station acoording to the flow pattern. In this study, based on this simulation results, proper water gate operation which can minimize negative impact will be provided.

대형 부유구조물의 구조응답 모니터링 시스템

김재동,Kim, Jae-Dong 재료연구소 1996 機械와 材料 Vol.8 No.1

감정 인식을 위한 합성곱신경망(CNN) 최적화

김재동(Jae-Dong Kim),이상현(Sang-hyun Lee),고한석(Han-Seok Ko) 대한전자공학회 2019 대한전자공학회 학술대회 Vol.2019 No.6

In this paper, we propose a convolution neural network structure optimized for facial recognition. We optimized the structure of the hidden layer to reduce the amount of learning computation, and as a result, the learning speed was improved. In addition, we improved the emotional recognition accuracy through learning parameters and data argumentation. As a result of the final learning experiment, the predicated rate was 84.9% and the learning speed was improved compared to VGG network [1].

무가압함침법에 의한 AI2O3p / AC8A 복합재료의 제조 및 특성

김재동(Jae Dong Kim),고성위(Sung Wi Koh),정해용(Hae Yong Jeong) 한국복합재료학회 2000 Composites research Vol.13 No.6

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다구찌 기법에 의한 Cr₂O₃ 플라즈마 코팅의 공정최적화

김재동(Jae-Dong Kim),김영식(Yeong-Sik Kim) 한국동력기계공학회 2020 동력시스템공학회지 Vol.24 No.1

Laminar Flow Reactor를 이용한 수분함량에 따른 석탄 휘발분의 점화 특성에 관한 연구

김재동(Jae Dong Kim),정성재(Sung Jae Jung),김규보(Gyu Bo Kim),장영준(Young June Chang),송주헌(Ju Hun Song),전충환(Chung Hwan Jeon) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

The main objective of this study is to investigate a variation of the ignition characteristics of coals as function of moisture content in a Laminar Flow Reactor (LFR) equipped with a fuel moisture micro supplier which was designed by Pusan Clean Coal Center. The volatiles ignition position and time of coals were experimentally observed when a pulverized coal with moisture was fed into the LFR under the burning conditions similar to those in the exit of pulverizer and real boiler. The post gas temperature along the centerline of the reactor was measured with a 70 ㎛, R-type thermocouple. The μ volatile ignition position was determined based on an average of 15 to 20 images captured by CCD camera for the different moisture content by a proprietary image processing technique. The post gas temperature proportionally decreases as a function of moisture content. As moisture content increases, the volatile ignition positions were 2.92, 3.36, 3.96, 4.65㎜ which corresponded to ignition times of 1.71, 1.96, 2.32, 2.7㎳, respectively. These results indicate that ignition position and time increases exponentially. By the same token, the ignition delay time derived from adiabatic thermal explosion was qualitatively calculated showing similar trend to the experimental data.

무가압함침법으로 제조된 입자강화 금속복합재료의 마모특성

김재동(JAE-DONG KIM),정순억(SUN-UK JUNG),김형진(HYUNG-JIN KIM) 한국해양공학회 2003 韓國海洋工學會誌 Vol.17 No.1

The effect of size and volume fraction of ceramic particles, with sliding velocity on the wear properties were investigated for the metal matrix composites fabricated by the pressureless infiltration process. The metal matrix composites exhibited about 5.5 - 6 times the wear resistance compared with AC8A alloy at high sliding velocity, and by increasing the particle size and decreasing the volume fraction, the wear resistance was improved. The wear resistance of metal matrix composites and AC8A alloy exhibited different aspects. Wear loss of AC8A alloy increased with sliding velocity, linearly ; whereas, metal matrix composites indicated more wear loss than AC8A alloy at the slow velocity region. However, a transition point of wear loss was found at the middle velocity region, which shows the minimum wear loss. Further, wear loss at the high velocity region exhibited nearly the same value as the slow velocity region. In terms of wear mechanism, the metal matrix composites generally exhibited abrasive wear at slow to high sliding velocity; however, AC8A alloy showed abrasive wear at low sliding velocity and adhesive and melt wear at high sliding velocity.

실습조사선의 종합정보통신망시스템 구축에 관한 연구

김재동(JAE-DONG KIM),박수한(SOO-HAN PARK),김형진(HYUNG-JIN KIM),고성위(SUNG-WI KOH),정해종(HAE-JONG JEONG) 한국해양공학회 2004 韓國海洋工學會誌 Vol.18 No.6

A small, highly-trained crew working on the ship's automation has contributed to the improvement of operations and the labor environment on board ship. However, at the same time, having a small crew adds more responsibility to the ship's officers to safely operate and manage the ship. With the use of information and computer technology, efforts are being made towards the development of a system that will concentrate important information from the various pieces of navigational equipment. The purpose of this study is to set up and implement an integrated marine data networking and communication system on the training-research ship. Information relating to navigation, engine and office automation are investigated and analyzed, and implementation methods associated with navigation, engine and management information system were designed and presented. In addition, the networking system of the navigational signal interface unit for the integrated communication system, and the data communication method between the ship and land are also discussed.