• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.1
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• pp.73-79
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• 2009

In this paper, the structural analysis and optimization of the door supporting rail structure in the header box located at the top of the aluminum passenger safety door(PSD) at the subway station, which opens and closes regularly, is performed. In case the simple fixed boundary condition is used for the bolt fixture on the supporting rail where the glass door is moving, excessive stresses are obtained. Therefore, more realistic finite element modeling of the bolts is used at the bolt fixture in the whole structure in order to obtain the more physically acceptable FEM results. As a result, fatigue life of twenty years of the structure is obtained to satisfy the design object. Also the optimal design of cross section of the rail part is performed using the response surface method and 15% of weight of the supporting rail part on the door is reduced.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.205-205
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• 2012

Korea Superconducting Tokamak Advanced Research (KSTAR) 장치는 국내 유일의 초전도 자석을 이용한 핵융합 연구 장치로서 초고온의 플라즈마를 생성하여 차세대 에너지원인 핵융합 에너지를 획득하는 것을 목표로 두고 있다. 플라즈마를 생성부터 유지하기 위해서는 수소 동위원소를 토카막 내부로 공급해 주어야 하는데 이러한 수소동위원소를 "연료"라 부르며, 이 연료를 토카막 내부로 공급해 주는 시스템을 연료주입 시스템(Fueling System)이라고 한다. KSTAR에서는 토카막 내부로 고속의 연료 주입이 필요하고 정밀한 양의 연료를 공급하는 밸브를 사용하여야 하며, 이러한 밸브를 제어 할 수 있는 제어기를 필요로 한다. 위의 사항에 적합한 피에조 밸브(Piezoelectric Valve)는 2 msec 이내의 개폐시간과 500 Torr ${\ell}$/s 이상의 유량을 흘려줄 수 있는 피에조 밸브로 압전소자에 가해지는 전압(0~250 V)에 따라 변위의 양에 비례하여 연료가 진공용기 내로 유입된다. 압전소자의 변위는 최대 140 ${\mu}m$로 최적화되어 있어야 하며, 정전용량(Capacitance)는 30~40 nF이어야 한다. 또한 소자에 힘(Force)를 가해 최대 7 N으로 136 ${\mu}m$의 변위를 가진 소자를 사용해야 한다. 피에조 밸브의 특성으로는 아날로그 신호로 작동이 되어야 하며, 유량신호를 피드백하여 밸브의 구동 전압을 정밀하게 제어 되어야 한다. 피드백 제어를 위해 압력센서는 XCS-190 Series를 사용하여 낮은 유량에서도 민감하게 반응하도록 제작하였으며, 고전압이 유기 되었을 때 제어기를 보호하기 위한 정션박스를 설치하였다. 밸브 제어기는 피에조 밸브의 개방 속도를 높이기 위해 밸브 구동 전압을 순간적으로 높이는 POP 전압을 생성하는 기능과 유량 신호를 피드백해서 밸브 구동 전압을 정밀 제어 하는 기능을 가지고 있다. 제어장치는 아날로그 및 디지털 제어회로의 전원용 +15 V DC와 밸브 구동용 +250 V DC 출력용의 전원 공급 장치(Power supply unit), 펄스 및 트리거 신호를 생성하는 Master Programmer unit), Pop 전압과 피드백의 중요한 기능을 수행하는 Valve controller unit로 제작 되었다. 피에조 밸브와 제어기는 상호 작용하여 동작을 원활히 할 수 있도록 특성 실험을 진행하여야 하며, 진공상태에서 Lack의 유무를 확인하여야 한다. 현재 개발 제작된 밸브의 진공누설시험 및 특성실험을 진행하고 있으며, KSTAR 5차 캠페인에 적용할 계획이다.

• Informatization Policy
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• v.27 no.2
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• pp.3-19
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• 2020

Artificial intelligence(AI) and blockchain are developing as the core technology leading the Fourth Industrial Revolution. However, AI is still showing limitations in securing and verifying data and explaining the evidence for the results, and blockchain also has some drawbacks such as excessive energy consumption and lack of flexibility in data management. This study analyzed technological limitations of AI and blockchain and convergence trends to overcome them, and finally suggested ways to improve Korea's related policies. Specifically, in terms of R&D reinforcement, we proposed 1) mid- and long-term AI /blockchain convergence research at the national level and 2) blockchain-based AI data platform development. In terms of creating an innovative ecosystem, we also suggested 3) development of AI/blockchain convergence applications by industry, and 4) Start-up support for developing AI/blockchain convergence business models. Lastly, in terms of improving the legal system, we insisted that 5) widening the application of regulatory sandboxes and 6) improving regulations related to privacy protection is necessary.

• The Optical Journal
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• s.158
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• pp.48-51
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• 2015

2013년 12월 2일에 아마존의 제프 베조스가 드론을 통하여 30분 배송을 실현하겠다고 배송 테스트를 했다. 고객이 주문한 물건을 플라스틱 보호 박스에 잘 담아 드론에 싣고 고객의 마당에 떨구고 돌아오는 모습을 담았다. 미국의 모든 언론은 드론에 대하여 대서특필하였고, 30분 배송의 실현 가능성에 대한 논쟁을 벌였다. 그 해 연말, 아마존은 쇼핑특수를 누렸다. 돈 안들이고 광고를 독특하게 한 셈이다. 나는 개인적으로 아마존의 드론 배달을 '쇼'라고 생각했다. 고객들의 주거 형태, 드론 비행의 법적인 문제, 드론으로 발생되는 사고, 사람들의 인식 등등 문제가 산적해 있기 때문이다. 그런데 2015년 초부터 알리바바는 1시간 내 차(Tea) 배달 서비스를 상하이와 광저우에서 테스트 중이라고 한다. 또한, DHL이 바다를 건너 섬으로 의약품을 수송하는 시연을 했다. CES 2015에서는 드론 전용관을 만들어 많은 사람들과 언론의 주목을 받았다. 마치 꿈과 같던 것이 실현되는 느낌이었다. 드론을 띄울 수 있는 권리 외에도 드론을 떨어뜨릴 권리도 논의되고 있다. 일본 총리관저에 드론이 떨어지기도 했다. 미국에서는 소형 드론에 폭발물을 탑재하여 타격하는 영상을 보이기도 했다. 개인적인 프라이버시가 존중되어야 할 가정집 위로 카메라가 달린 드론이 날아다니기도 하며, 재소자들의 수감시설에 마약과 담배를 실어 나르다 적발되기도 하였다. 부작용도 만만치 않다는 이야기이다. 나는 학생들에게 100만 원이 넘는 드론을 구매하여 주었더니, 동력인 배터리가 20분밖에 안 된다고 투덜거린다. 영상에 그리고 비행에 소리가 너무 난다고 또 투덜거린다. 바람에 밀려 조정이 어렵다고 또한 투덜투덜하더니만, 결국은 비행 중 조절이 안 되고 떨어져서 결국 박살이 났다. 내구성이 약하다는 이야기는 곧 전반적으로 아직 한계가 있으며 개선할 점이 많다는 의미이다. 위와 같은 부정적인 요인에도 불구하고 드론은 새로운 서비스의 융합으로 신시장이 기대되는 만큼 많은 국가와 기업들이 주목하고 있다. 미국가전협회(CEA)는 2015년 세계 드론 시장이 2014년보다 무려 55% 성장한 1억 3,000만 달러의 규모로 성장하고 5년 뒤에는 10억 달러까지 증가할 것으로 전망하면서 드론 산업의 가능성을 높게 평가하기도 했다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.3
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• pp.299-308
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• 2011

In this study, we develop a pressure observer to measure the cylinder length of a harbor-construction robot. For the robot control, sensors are required to measure the length of a hydraulic cylinder. The cylinder-position sensor is relatively expensive when the operating environment prohibits external approaches for the measurement of the cylinder position. LVDT or linear scales are usually mounted on the outside of the cylinder, which causes poor durability on a construction site. We use a pressure sensor to indirectly estimate the length of the cylinder. The pressure sensor is mounted inside a hydraulic valve box so that it is protected by the box and easy to waterproof for an underwater robot. By treating oil as a compressible fluid, we derive the nonlinear pressure dynamics as a function of the cylinder position, velocity, and pressure. The recursive least squares (RLS) algorithm is applied to identify the dynamic parameters, and the pressure observer estimates the cylinder position through the pressure acting on the head and the rod of the hydraulic cylinder. The position accuracy is relatively low, but it is acceptable for a construction robot that handles large armor stones.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.8
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• pp.843-850
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• 2012

To satisfy the operational requirements of surveillance radar and the operational concept of a ship combat system, an active-array-type antenna was designed using solid-state transmitters and receivers. The arrangement of the constituent electronic components of the antenna system, considerably large in size, and therefore, the antenna needs to be housed in a box. The rotational antenna system installed on a ship mast is installed in a sealed housing to protect the interior equipment from environmental conditions. The outer shape of the housing is that the antenna should be capable of rotating normally despite strong winds. Furthermore, in recent times, designs with low radar cross section (RCS) have attracted attention from the viewpoint of improving the stealth of the ship. In this light, four types of models are proposed for the outer shape design of the antenna system, and they are investigated from the viewpoint of low RCS design as well as wind load.

• Journal of Information Technology Services
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• v.12 no.2
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• pp.171-184
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• 2013

Frequently faced with dangerous situations, for evidentiary purpose in case of civil and criminal liability challenges, car drivers in Korea have been armed with so-called 'black boxes'; however, which are just video recorders in vehicles rather than real 'black boxes' that are equipped in the airplanes. In the United States, they are called EDRs(Event Data Recorders), more technically, which means that they record data of events happened while driving, such as velocity changes, airbags deployment, seatbelt wearing etc. just like in the airplanes. EDR technology is quickly becoming more advanced, more widely available, and less expensive; however, new concerns are emerging : the privacy of drivers. In U. S., vehicle manufacturers and insurance companies and the governmental agencies including the courts and legislatures are the main parties in terms of the EDR concerns. In order to determine the best way to regulate EDR, it is necessary to balance all the merits, such as safety, privacy, truth, justice and efficiency, to support a legal framework regulating the EDR concerns. This article, in light of the regulation of EDR and experience therof in the United States, examines EDR technology itself, particularly with respect to the automobile industry, describing its history, its current state, and trends that may change it in the future; and explains how the National Highway Transportation Safety Agency (NHTSA), legislatures, courts have approached EDR data. At the early stage of regulation on EDRs in Korea, examining U. S. legal framework and usages would help for successful establishment of legislation and regulation.

• Convergence Security Journal
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• v.22 no.3
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• pp.101-110
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• 2022

As the cases of using artificial intelligence in various fields increase, attempts to solve various issues through artificial intelligence in the intrusion detection field are also increasing. However, the black box basis, which cannot explain or trace the reasons for the predicted results through machine learning, presents difficulties for security professionals who must use it. To solve this problem, research on explainable AI(XAI), which helps interpret and understand decisions in machine learning, is increasing in various fields. Therefore, in this paper, we propose an explanatory AI to enhance the reliability of machine learning-based intrusion detection prediction results. First, the intrusion detection model is implemented through XGBoost, and the description of the model is implemented using SHAP. And it provides reliability for security experts to make decisions by comparing and analyzing the existing feature importance and the results using SHAP. For this experiment, PKDD2007 dataset was used, and the association between existing feature importance and SHAP Value was analyzed, and it was verified that SHAP-based explainable AI was valid to give security experts the reliability of the prediction results of intrusion detection models.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.16 no.5
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• pp.93-106
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• 2006

With the rapid growth of the wireless Internet communication, a new generation of mobile devices have made possible the broad distribution of mobile digital contents, such as image, music, video, games and applications over the wireless Internet. Mobile devices are rapidly becoming the major means to extend communication channels without copy Protection, usage rule controlling and authentication. As a result, mobile digital contents may be illegally altered, copied and distributed among unauthorized mobile devices. In this paper, we take a look at Open Mobile Alliance (OMA) DRM v2.0 in general, its purpose and function. The OMA is uniquely the focal point for development of an open standard for mobile DRM. Next we introduces features for an active content and illustrates the difference between an active content and an inactive content. Enabling fast rendering of an active content, we propose an OMA-based DRM framework. This framework include the following: 1) Extending DCF Header for supporting an selective encryption, 2) Content encryption key management, 3) Rendering API for an active content. Experimental results show that the proposed framework is able to render an active content fast enough to satisfy Quality of Experience. %is framework has been proposed for a mobile device environment, but it is also applicable to other devices, such as portable media players, set-top boxes, or personal computer.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.4
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• pp.345-356
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• 2011

Based on the consideration of land based pollutant discharges from the basin and seawater quality related carrying capacity and the seawater quality improvement in receiving water bodies of Yeoja Bay where eutrophication and organic pollution are in progress, were evaluated. The permissible inflow loads of BOD, TN and TP by using the geographical features and box modelling method were estimated. As results, it is shown that the reduction rate of discharged BOD and TP loads were 39.3% and 30.8 %, respectively, however, 6.9% was estimated for TN. According to the pollutant loading in each tributary and generated load of the basin, it is given much weight on the land use group, and also was shown in discharged load estimation. This suggests that it is important to control nonpoint source pollutant such as livestock and land use groups as well as point source to contribute the proposition of the water quality improvement plan according to the characteristics of the bay.