• Journal of the Korean Magnetics Society
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• v.14 no.6
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• pp.207-212
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• 2004

Eddy current (EC) testing methods are widely used in a variety of applications including the inspection of steam generator tubes in nuclear power plants, aircraft parts and airframes. A key factor that affects the EC signal is lift-off which means the physical distance between a sensor and a specimen in the testing. In practice, it is difficult to keep track of the actual value of the lift -off during a specific experiment, simulation or testing in the field, which is essential for accurate interpretation of the signal to be used in the following steps. Hence it is necessary to have a scheme to render the EC signal invariant to the effects of lift-off in spite of the changes in the real world. This paper describes a new method for compensating EC signals for variations in lift-off by acquiring an invariance feature using a homomorphic operator and neural network techniques. The signals from various lift-offs are transformed to obtain a zero lift-off equivalent signal that can be subsequently used for defect characterization in the next step.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.34 no.2
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• pp.217-228
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• 2024

LiDAR(Light Detection And Ranging) sensors, which play a pivotal role among cameras, RADAR(RAdio Detection And Ranging), and ultrasonic sensors for the safe operation of autonomous vehicles, can recognize and detect objects in 360 degrees. However, since LiDAR sensors use lasers to measure distance, they are vulnerable to attackers and face various security threats. In this paper, we examine several security threats against LiDAR sensors: relay, spoofing, and replay attacks, analyze the possibility and impact of physical jamming attacks, and analyze the risk these attacks pose to the reliability of autonomous driving systems. Through experiments, we show that jamming attacks can cause errors in the ranging ability of LiDAR sensors. With vehicle-to-vehicle (V2V) communication, multi-sensor fusion under development and LiDAR anomaly data detection, this work aims to provide a basic direction for countermeasures against these threats enhancing the security of autonomous vehicles, and verify the practical applicability and effectiveness of the proposed countermeasures in future research.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1D
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• pp.89-98
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• 2010

The goal of this study is to investigate the achievement of street improvement projects based on district unit plans aiming at improving the urban streetscape. Post assessments are conducted for three streetscape improvement projects - Noyu street improvement project, Hanaro street improvement project next to Sungshin women's university, Chatgoshipun street improvement project in front of Ehwa women's university. The results of the post assessment indicate that the initial quality of streetscape has been improved after the projects. The long-term sustainability of the streetscape, however, was not achieved for the street improvement project applied at the street next to Sungshin women's university due to the lack of support from the community. It is found that the key component of success for the street improvement project is the strong cooperation between public and private parties.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.6
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• pp.9-14
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• 2008

Intentional city bands and public radio frequencies could reduce the internet transmission speed on the wired lines because AM and HF band are overlapping on the xDSL up and down data steam by way of the wired transmission lines. We were designed the adaptive common mode rejection circuit with 2 way amplifier against public radio frequency. Specially our circuits were applied for power and signal lines. We could reduced the common mode rejection up to 30dB and increased the up stream speed around 1.8 times using a our developed equipments. Also it could expanded the transmission distance up to 1.7 times than old lines.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.380-386
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• 2019

Shoulder joint pain is a very common musculoskeletal disorder, in which about 20 percent of adults experience it more than once in their lives. In this study, an objective assessment was made that subacromial space was increased by pectoralis minor stretching exercise, which has a positive effect on impingement syndrome and shoulder pain. Also, This study examined the effects on pectoralis minor length(PML) and acromio-humeral distance(AHD) following pectoralis minor self-stretching exercise in normal adults. In this study, a total of 30 subjects were recruited and randomly divided into a self-stretching exercise group(n=15) and manual stretching exercise group(n=15) to compare the immediate effects of treatment. Studies have shown that both groups have significantly increased both PML and AHD within the group(p<.05). There was no statistically significant difference in the comparison between the groups(p>.05). The results suggest that self-stretching exercise can be recommended as a treatment method for impingement syndrome and prevention of shoulder disease.

• Proceedings of the KAIS Fall Conference
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• 2011.05a
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• pp.478-481
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• 2011

본 연구는 GIS를 이용하여 물리적 공간 차원에서 특정 지역 거주자의 물리적 공간 차원에서 공공시설 향유도를 분석하여 평가하는것을 목적으로 한다. 향유도 평가를 위해서는 향유도를 측정할수 있는 지표와 (GIS를 이용한) 지표 값 계산 도구의 개발이 필요하다. 지표는 접근성 및 사용가용량이 고려된다. 사용가용량은 특정 주택으로부터 일정거리 이내에 존재하는 공공시설의 가용량의 합을 말한다. 지표 값을 계산하기 위해선은 GIS를 활용한다. GIS를 통한 향유도 평가 결과는 특정 지역 거주자가 일정거리이내 공공시설에 대한 접근성을 고려하는 동시에 공공시설에 대한 사용가용량을 종합 비교하여 보여준다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.10a
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• pp.346-348
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• 2022

Many CCTVs are needed to monitor a physically large area. When installing CCTV indoors, the wiring environment is sufficient, so many CCTVs can be installed. However, wiring is relatively difficult outdoors. In addition, when monitoring a long distance, wiring costs to the monitoring site are incurred. Therefore, when installing CCTV at a physically long distance, it is necessary to apply wireless technology. In this study, the structure of the existing CCTV system was checked and the requirements for converting it to a wireless environment were derived. And according to the requirements, a wireless-based intelligent CCTV system was proposed. As a result, it was confirmed that the wireless-based intelligent CCTV proposed in this study operates normally in a wireless environment. This study was conducted based on the wifi environment, and additional research is needed to extend it to the mobile mobile telecommunication environment.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2002.04a
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• pp.60-60
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• 2002

비행탄의 종말속도증대를 위하여 고체램제트를 이용하는 개념은 현재 세계적으로 여러나라에서 연구 중에 있다. Solid Fuel Ramjet Propulsion(고체연료 렘제트 추진)은 로켓추진에 비하여 월등히 높은 비추력을 가지며 구조적으로 매우 간단하여 탄의 사거리 및 평균속도를 증대시키는 좋은 수단으로 사용되고 있다. 그러나 간단한 구조에도 불구하고 고체렘제트의 작동은 매우 다양한 물리적 현상이 연관되므로 필요한 성능을 얻기 위해서는 이들의 상호 작용을 고려하여 설계의 최적화 및 성능 예측이 필요하다.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2006.04a
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• pp.145-149
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• 2006

모바일 맹핑시스템에 장착되어 있는 카메라와 INS의 물리적 관계 (두 좌표축 간의 거리(lever-arm) 와 각도(boresight) 캘리브레이션은 카메라 영상의 지리적 정보를 생성하기 위해 필요로 한다. 이 목적을 위해 기존연구는 카메라 캘리브레이션을 통하여 이 물리적 관계를 추정하고 있다. 카메라 캘리브레이션은 3차원 좌표가 할당된 타겟을 이용하여 움직이는 카메라의 렌즈 왜곡과 내/외부 표정 계산하는 것이다. 이 추정에서, 저가의 INS의 초기상태인 자세, 각도는 사용자의 측량에 의해 결정이 된다. 만약 정교한 측량이 없을 경우, 카메라 영상의 지리적 정보는 잘못된 정보를 제공 할 것이다. 정교한 측량의 어려움을 피하기 위해, 본 논문은 카메라와 초기상태 정보가 없는 INS간의 물리적 관계를 위한 수학적 모델을 설계하였다. 시스템에 장착된 카메라와 INS의 초기 기준 좌표계의 관계는 lever-arm과 boresight을 이용한 좌표축 변환으로 정의 될 수 있으며, 이 시스템이 이동 후, 카메라 초기 기준 좌표계에서 INS의 위치는 두 개의 벡터 경로로 정의 될 수 있다. 이 두 벡터 경로는 카메라와 INS의 상대 외부표정의 관계를 이용하여 계산된 벡터들의 조합으로 정의된다. 본 논문은 여러 쌍의 경로로부터 lever-arm과 boresight을 추정하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.589-591
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• 2005

최근에 P2P(Peer-to-Peer) 시스템에서 효율적인 자원 탐색 방범에 대해 많이 연구되고 있다. P2P overlay network 중 하나인 Chord는 자원을 효율적으로 탐색할 수 있는 간단한 P2P 프로토콜이다. 대부분의 P2P 시스템은 overlay network를 형성하므로 노드와 노드 사이의 물리적인 거리를 고려하지 않으므로 서로 이웃한 노드라도 실제 물리적인 latency가 클 수 있다는 문제점을 가지고 있다. 이 논문은 물리적으로 가까운 노드들을 하나의 subnet으로 만들어서 물리적인 latency를 감소시키고 각 subnet안에 복사본(replica)을 둠으로써 탐색(lookup)의 효율성을 향상시킨다.