• Journal of the Korean Magnetics Society
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• v.27 no.2
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• pp.63-69
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• 2017

Naval ships are particularly required to maintain acoustic and magnetic silence due to their operational characteristics. Among them, underwater magnetic field signals derived by ships are likely to be detected by threats such as surveillance systems and mine systems at close distance. In order to increase the survivability of the vessels, various techniques for reducing the magnetic field signal are being studied and it is necessary to consider not only the magnitude of the magnetic field signal but also the gradient of it. In this paper, we use the commercial electromagnetic finite element analysis tool to predict the induced magnetic field signal of ship's scaled model, and arrange the degaussing coil. And the optimum degaussing current of the coil was derived by applying the particle swarm optimization algorithm considering the gradient constraint. The validity of the optimal degaussing technique is verified analytically by comparing the magnetic field signals after the degaussing with or without gradient constraint.

• Journal of Broadcast Engineering
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• v.28 no.3
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• pp.329-332
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• 2023

3D Object Detection using deep neural network has been developed a lot for obstacle detection in autonomous vehicles because it can recognize not only the class of target object but also the distance from the object. But in the case of 3D Object Detection models, the detection performance for distant objects is lower than that for nearby objects, which is a critical issue for autonomous vehicles. In this paper, we introduce a technique that increases the performance of 3D object detection models, particularly in recognizing distant objects, by generating virtual 3D vehicle data and adding it to the dataset used for model training. We used a spherical point tracing method that leverages the characteristics of 3D LiDAR sensor data to create virtual vehicles that closely resemble real ones, and we demonstrated the validity of the virtual data by using it to improve recognition performance for objects at all distances in model training.

• The Journal of the Acoustical Society of Korea
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• v.20 no.3
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• pp.91-97
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• 2001

Since the new field information of target signal is important in the development and verification of active sonar system, experimental method and simulation technique are widely used in order to analyze the detail characteristics of target scattered echoes. Therefore, in this paper, the scale target experiment is performed to develope and Improve the target signal simulation model. Since the experimental results show that the specular reflection is the major component among scattering mechanisms, the target signal simulation model based on the Geometric Optics Theory (GOT) is developed. Complex target is separated into simple shapes, known as canonical shape. The contribution from individual canonical shapes are summed with proper phase and amplitude to produce the target strength of the whole complex body. Simulated target signal is compared with the experimental results and discussed.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.13 no.1
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• pp.31-39
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• 1995

We have various methods of measurement for a safety diagnosis of outworn structure, but these methods to find a variation of structure are not convincible with it's exactness and confidence. We have to lay out a scheme for a solution of these problems and improve a visibility of result. In this study, we studied a optimized solution for close-range photogrammetry to offer the more reliable method compare to conventional method and to improve it's confidens and visibility of output. For obtaining these effects, we manufactured the plane models and curved surface ones each devided into two types, normal case and obilique case. In this way, we got a optimum solution to increase a confidence level and visibility of photogrammetry. And actually, this study will be a good way to measure a variation of structures.

• Smart Media Journal
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• v.2 no.3
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• pp.34-38
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• 2013

Several costs including printing and management are added in commerce by vouchers. In this case that a voucher is digitalized and flown through mobile phones, these costs are diminished considerably. Also, as mobile commerce is on the increase according to the activation of smart phones, NFC technology with near distance communication is gave attention to. Therefore, researches for using NFC-based electronic vouchers to pay electronically on mobile are made. To analyze the flow path of electronic vouchers, which helps marketing strategy, this paper proposes the method to put useful data into them. The proposed method utilizes object memory model. The proposed electronic voucher includes the block for flow history data in addition to its information. In the future, we will implement and test this electronic voucher.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.9
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• pp.1843-1853
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• 1997

The channel throughput and packet delay of wireless media control (MAC) protocols with Rayleigh fading, log-normal shoadowing and near-far effects are analyzed. We consider CSMA/CA protocols as the wireless MAC protocols, since CSMA/CA protocols are based on the standard for wireless Local Area Networks (LANs) IEEE 802. 11. We have found that the performance of CSMA/CA in radion channel model is reduced above 50% than those of error free channel model in low traffic load. We also found that 4-Way Handshake CSMA/CA protocol is supterior to the other CSMA/CA protocols in high traffic load.

• The Transactions of the Korea Information Processing Society
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• v.4 no.8
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• pp.2106-2119
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• 1997

NDAS(Network Data Access System) is a system that interconnects high speed network(B-ISDN) and Local Area Network(Ethernet, FDDI). Nowadays, the request of multimedia data increases rapidly, so NDAS system must accept and process that request efficiently. Comparing with normal data traffic characteristics, multimedia data traffic characteristics are much complex, so it is necessary to implement the system that can cover such factor. In this paper, we suggest a NDAS hardware system model and also we propose a proper buffer size of NDAS system through the simulation. For measuring the proper buffer size of NDAS, we assumed two different simulation models, one is the case of using only one buffer and the other is the case of using two different buffers for Ethernet and FDDI, respectively. After comparing and analyzing simulation results, we suggest the proper NDAS system buffer size.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2015.11a
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• pp.96-99
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• 2015

본 논문에서는 중복되지 않는 서로 다른 카메라의 영상을 활용한 동일 객체 판단 및 추적 기술에 대하여 소개한다. 영상분석에서 색상 정보는 가장 기본이 되는 중요한 정보라 할 수 있다. 특히 색상 정보를 이용하는 히스토그램은 일반적으로 추적, 인식 등에 많이 사용되고 있으나 이동 객체나 조도 변화 등에 따라 성능에 차이를 보인다. 이러한 문제점을 해결하고자 본 연구에서는 동일 객체 판단을 위해 대표적으로 사용되는 히스토그램 정합의 두 알고리즘(HSV 공간에서의 Histogram matching 방법과 RGB 공간에서의MCSHR 알고리즘) 결합을 통해 분할 히스토그램은 객체를 3조각으로 나누어 전체와 각각의 히스토그램을 구하며 MCSHR을 RGB공간이 아니 Hue 공간 히스토그램으로 변경하여 유사도를 도출 하였으며 조도 변화에 강인한 모델을 만들기 위해 Controlled equalization기법을 사용하여 원 영상의 히스토그램의 확률과 평활화한 히스토그램의 확률 융합을 시도 하였다. 해당 실험의 비교 결과 기존 HSV공간에서 Histogram matching을 통한 유사도 비교보다 12.9% 향상된 정합율의 결과를 보였다. 또한 영상 정보와 스마트 기기를 통한 인식 방법의 융합을 통해 영상 내에서 동일 객체 판단에 대한 추가 정보 제공에 대해 방법론 적인 부분을 제안 하였다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.11a
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• pp.89-94
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• 2004

Up to now a lot of the study on ship collision avoidance systems has proceeded actively. However the frequency of ship collision accidents didn't decreased. If there is collision risk in close quarters situation none the less manouvering ship for collision avoidance according to the system, only use of TCPA and DCPA as input factor for collision risk decision is not useful to avoiding collision action. For the recent 5 years by the analysis of first observation distance about approaching ship in domestic collision accidents, nearly $45\%$ of accidents is close first observation less than 2 miles. Therefor it is essential part for safety navigations to study for collision avoidance action in close encounter. In this paper, as foundation study of supporting collision avoidance manoeuvring for navigators, we proposed ship collision avoidance support model in close quarters situation through analysis of collision accidents for effective getting rid of the causes.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.4
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• pp.1-10
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• 1998

The magnitudes of historical earthquake records related with house collapses are estimated considering the magnitude, epicentral distance, soil condition and aging of a house. Eighteen artificial time histories for magnitudes 6-8, epicentral distances 5 km-350 km and hard and soft soil condition were generated. Nonlinear dynamic analyses were performed for a traditional three-bay-straw-roof house. The aging effect of the house was modeled as such that the lateral loading capacity of wooden frames represented by hysteretic stiffness was decreased linearly with time. The house was idealized by one degree-of-freedom lumped mass model and the nonlinear characteristics of wooden frames were modeled by the Modified Double-Target mode. For far field earthquakes, minor damages were identified regardless of magnitude, soil condition and aging of the house. For intermediate field earthquake, earthquake magnitude greater than 6.5 caused severe damages in soil sites. For near field earthquake, severe damages occurred for magnitude greater than 6.5 regardless of soil condition and aging of the house. It is estimated that the magnitude of historical earthquakes is about 6.2. An empirical equation of magnitude-intensity relationship suitable to Korea is suggested.