• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.179.1-179.1
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• 2013

Cylindrical Rotating Magnetron Sputtering Cathode (이하 Rotary Cathode)는 기존에 사용 되던 rectangular type 보다 Target 사용 효율이 높다는 큰 이점을 가지고 있다. 높은 Target 사용 효율은 비용 절감 효과와 직접적으로 관련 된다. 이번 연구는 3D Plasma simulation(PIC-MCC)을 통한 Target 사용 효율 80% 이상의 Rotary Cathode 개발을 목적으로 한다. Plasma simulation에 External Magnetic fields를 접목하여 Electron의 이동 궤적을 제어하였고, 생성된 Ion (Ar+)의 밀도 및 속도로 Plasma의 안정성과 Erosion 계산 구간을 선정 하였다. Target Erosion Profile은 Sputtering yield Data와 Target에 충돌한 Ion 정보를 사용하여 산출 하였으며, Sputtered Particles의 Deposition Profile은 계산된 Target Erosion Profile과 The cosine law of emission을 이용하여 계산 하였다. 실험 조건은 Plasma simulation의 초기조건 바탕으로 하여 2G size의 ITO Target을 대상으로 실험 하였다. 비 Erosion 영역 최소화하기 위해 Magnet Length를 변경하여 제작 적용 하였다. Simulation 계산 시간의 제약으로 인하여 simulation에서 생성된 최대 이온 밀도는 일반적으로 알려진 값 보다 적게 계산 되었지만, Simulation으로 예측한 Erosion Profile 및 Deposition Profile은 실험 값과 유사한 형태를 나타났으며, 실험 결과는 Target 사용 효율 80%이상의 결과를 보였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.1
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• pp.57-64
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• 2021

The speed change lane is installed at the point where the roads are connected on the urban roads, reducing the relative speed to facilitate traffic communication. However, in the case of the speed limit of 30 km/h in accordance with the implementation of the safe speed "5030" in the city, the standard is ambiguous, and there are criticisms about the installation of the transmission lane. This study conducted a pilot study on the traffic patterns of the speed change lanes, focusing on the section where the safe speed "5030" policy was scheduled to be implemented after theoretical consideration of the speed change lanes. After on-site investigation, as a result of analyzing the traffic pattern according to the travel speed of the main road according to road conditions and traffic conditions, the effectiveness of the speed change lane according to the safety speed "5030" was analyzed. In this study, the installation criteria for speed change lane by speed were presented. The criteria is that "speed change lanes should not be installed when the speed limit is 30 km/h, and speed change lanes should be installed when the speed limit is 50 km/h." The criteria will be considered as a reference when establishing engineering standards for connection of other facilities in urban areas in the future. It is expected that unnecessary restrictions on individuals' exercise of private property rights will be minimized, smooth traffic flow and secure safety by the installation of speed change lanes and expansion of turning radius.

• The Journal of the Acoustical Society of Korea
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• v.7 no.4
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• pp.54-76
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• 1988

In Part Ⅰ of the paper, we have developed various block least mean-square (BLMS) adaptive digital filters (ADF's) based on a unified matrix treatment. In Part Ⅱ we analyze the convergence behaviors of the self-orthogonalizing frequency-domain BLMS (FBLMS) ADF and the unconstrained FBLMS (UFBLMS) ADF both for the overlap-save and overlap-add sectioning methods. We first show that, unlike the FBLMS ADF with a constant convergence factor, the convergence behavior of the self-orthogonalizing FBLMS ADF is governed by the same autocorrelation matrix as that of the UFBLMS ADF. We then show that the optimum solution of the UFBLMS ADF is the same as that of the constrained FBLMS ADF when the filter length is sufficiently long. The mean of the weight vector of the UFBLMS ADF is also shown to converge to the optimum Wiener weight vector under a proper condition. However, the steady-state mean-squared error(MSE) of the UFBLMS ADF turns out to be slightly worse than that of the constrained algorithm if the same convergence constant is used in both cases. On the other hand, when the filter length is not sufficiently long, while the constrained FBLMS ADF yields poor performance, the performance of the UFBLMS ADF can be improved to some extent by utilizing its extended filter-length capability. As for the self-orthogonalizing FBLMS ADF, we study how we can approximate the autocorrelation matrix by a diagonal matrix in the frequency domain. We also analyze the steady-state MSE's of the self-orthogonalizing FBLMS ADF's with and without the constant. Finally, we present various simulation results to verify our analytical results.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2013.04a
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• pp.116-116
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• 2013

마그네슘은 스마트폰, 전자기기 케이스, 내화벽돌과 아크용접봉 제조시의 첨가물 등으로 사용되고 있는데, 최근에는 재활용을 위한 마그네슘 용해로를 취급하거나 가공하는 사업장이 증가하고 있어 사고위험성이 높아지고 있다. 금속분을 취급하는 사업장에서의 금속분진은 저장이나 축적 등과 같이 주로 퇴적물로서 존재한다. 퇴적분진의 발화온도는 퇴적물 형상과 두께, 입경, 분위기 가스의 유속, 산소농도, 부유분진의 농도, 퇴적밀도, 수분 등의 많은 영향인자가 관여하기 때문에 이론적 예측이 힘들고 실험적인 측정에 의존할 수 밖에 없는 것이 현실이다. 본 연구에서는 연소성이 높고 화재폭발사고사례가 많은 마그네슘(Mg) 분진을 사용하여 승온속도 변화에 따른 열분해특성을 조사하였다. 퇴적분진의 열적특성을 조사하기 위하여 METTLER TOLEDO의 TGA/DSC1를 사용하였으며, Mg 시료의 평균입경은 38, $142{\mu}m$이다. 입경 $38{\mu}m$의 Mg 시료의 열중량분석 결과, 중량증가는 $400{\sim}500^{\circ}C$의 범위에서 시작되며 $550^{\circ}C$에서 급격하게 중량이 증가하고 있으며, 증량증가개시온도(Temperature of weight gain)는 $460^{\circ}C$에서 시작하여 $900{\sim}950^{\circ}C$ 범위에서 중량 증가 포화값에 도달하였다. 입경 $142{\mu}m$의 Mg에 대하여 공기중 승온속도를 5, 10, $20^{\circ}C/min$으로 변화시키면서 실온에서 $900^{\circ}C$까지 가열 시키는 경우의 시료의 중량 변화에 따른 열분해 특성은 승온속도가 증가할수록 2단계의 S자 곡선은 완만하게 상승을 나타내며 중량증가개시온도가 높아지는 경향을 보이고 있다. 중량증가개시온도가 승온속도에 따라 변화하는 결과를 나타내고는 있지만, 시료량의 증가에 따른 영향을 열중량분석 실험방법의 제약으로 인하여 확인할 수 가 없었다. 그러나 만일 시료량이 크게 증가하는 경우에는 동일한 승온조건에서 중량증가 개시온도는 낮아질 가능성이 있다. 중량증가는 시료의 산화반응에 의한 것이므로 시료량의 증가는 시료 내부에의 열의 축적을 용이하게 하여 보다 낮은 온도에서도 산화반응이 충분히 일어나는 조건이 형성되기 때문이다. 승온속도가 증가할수록 산화 반응한 괴상형태의 연소입자가 크게 증가하고 있는 것을 알 수 있다. 승온속도에 따른 중량개시온도 곡선을 보면 [그림 24]와 같으며 승온속도 5, 10, $20^{\circ}C/min$의 증가에 따라 중량개시온도는 각각 490, 510, $530^{\circ}C$가 얻어졌으며 승온속도의 증가에 따라 중량개시온도가 증가하는 경향을 보이고 있다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.4
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• pp.243-248
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• 2022

Weight optimization was performed for a rotorcraft shaft system using one-dimensional Euler-Bernoulli beam elements. Torsion, shaft support stiffness such as bearings, flange mass are all considered. To guarantee structural dynamic stability, eigenvalue analysis was performed to avoid critical speed and tooth mesh excitation form the gearbox. The weight optimization was performed by adjusting the thickness and radius while the length of the shaft was fixed, and the optimization process was divided into two stages. In the first, the weight is optimized with the torsional strength constraint. In the second, the difference between the primary mode of shaft and the critical speed is maximized so that the primary mode of the shaft can avoid the critical speed while the constraint on the torsional strength of the shaft is satisfied according to the standard for shaft system stability (AMC P 706-201, 1974). The proposed method was verified by comparing the results of the optimal design using the given one-dimensional beam elements with the stress results of the 3D finite element and the actual manufactured shaft.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.11a
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• pp.72-74
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• 2012

위성의 상태를 모니터링하고 임무수행 준비 및 결과를 분석하기 위해 위성에서는 주기적으로 텔레메트리 프레임을 생성하여 지상으로 전송한다. 텔레메트리 프레임을 통해 많은 데이터가 전송될수록 정확한 위성의 상태 분석이 가능하고 위성 운용을 용이하게 할 수 있다. 그러나 위성에서 지상으로 전송할 수 있는 텔레메트리의 전송속도는 하드웨어의 성능에 따라 제한되며, 특히 저궤도 위성의 경우에는 지상과 교신이 가능한 시간이 짧다는 제약으로 인해 한정된 시간 안에 정해진 전송속도로 보낼 수 있는 데이터의 양에는 한계가 있다. 이러한 제약조건 하에서 최대한 많은 정보를 효율적으로 전송할 수 있도록 위성의 텔레메트리를 생성할 때 비트 정보들을 모아 하나의 바이트로 묶어서 텔레메트리 크기를 최소화하는 방법을 이용한다. 위성비행소프트웨어는 태스크 스케쥴링, 열제어, 전력제어, 자세제어, 원격명령처리, 원격측정데이터 처리 등의 기능별로 모듈화 되어있다. 각 모듈마다 텔레메트리로 전송되는 데이터들이 존재하고 비트 정보들을 모으는 기능도 해당하는 모듈에서 각각 담당한다. 따라서 각 모듈들이 독립적이지 못하고 텔레메트리 처리를 담당하는 모듈과 다른 모듈들 간의 커플링(coupling)이 존재하게 되어 하나의 텔레메트리 데이터 변경이 여러 모듈에 영향을 미치게 된다. 본 논문에서는 모듈들 간의 커플링을 최소화하고 텔레메트리의 변경사항이 위성비행소프트웨어 코드 자체에는 영향을 주지 않도록 하기위한 데이터베이스 테이블을 이용한 텔레메트리 처리 방안에 대하여 설명한다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.3
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• pp.49-59
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• 2002

As the electronic commerce increases rapidly in the mobile communication, security issues become more important. A suitable authentication and key agreement for the mobile communication environment is a essential condition. Some protocols based on the public key cryptosystem such as Diffie-Hellman, EIGamal etc. were adapted in the mobile communication. But these protocols that are based on the difficult mathematical problem in the algebra, are so slow and have long key-length. Therefore, these have many limitation to apply to the mobile communication. In this paper, we propose an authentication and key agreement protocol based on NTRU to overcome the restriction of the mobile communication environment such as limited sources. low computational fewer, and narrow bandwidth. The proposed protocol is faster than other protocols based on ECC, because of addition and shift operation with small numbers in the truncated polynomial ring. And it is as secure as other existent mathematical problem because it is based on finding the Shortest or Closest Vector Problem(SVP/CVP).

• Geophysics and Geophysical Exploration
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• v.16 no.3
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• pp.171-179
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• 2013

An automated ultrasonic velocity measurement system adopting pulse-echo-overlap (PEO) method has been constructed, which is known to be a precise and versatile method. It has been applied to velocity measurements for 5 kinds of engineering plastic cores and compared to first arrival picking (FAP) method. Because it needs multiple reflected waves and waves travel at least 4 times longer than FAP, PEO has basic restriction on sample length measurable. Velocities measured by PEO showed slightly lower than that by FAP, which comes from damping and diffusive characteristics of the samples as the wave travels longer distance in PEO. PEO, however, can measure velocities automatically by cross-correlating the first echo to the second or third echo, so that it can exclude the operator-oriented errors. Once measurable, PEO shows essentially higher repeatability and reproducibility than FAP. PEO system can diminish random noises by stacking multiple measurements. If it changes the experimental conditions such as temperature, saturation and so forth, the automated PEO system in this study can be applied to monitoring the velocity changes with respect to the parameter changes.

• Journal of the Korea Society of Computer and Information
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• v.10 no.6 s.38
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• pp.219-226
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• 2005

This paper describes the open API with integration of semantic web service with PARLAY X based open API in 4G mobile network. It can be expected that the intelligence such as the context-awareness, adaptation and personalization in 4G mobile network will be deployed. But the existing PARLAY based network lacks in considering context-awareness, adaptation and personalization. Therefore, the object of this paper is to support the architecture and the Application Programming Interface (API) of the network service for the context-awareness, adaptation and Personalization in 4G mobile network The open API is to provide users with the adaptive network service to the changing context constraints as well as detecting the changing context and user's Preference. For instance, the open API can Provide users with QoS in network according to the detected context and user's preference, after detecting the context such as location and speed and user's preference.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.2
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• pp.121-128
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• 2021

In this paper, we propose a path generation and tracking algorithm of an unmanned air vehicle in a two-dimensional plane given the initial and final points. The path generation algorithm using the Dubins curve proposed in this work has the advantage that it can be applied in real time to an unmanned air vehicle. The path tracking algorithm is an algorithm similar to the line-of-sight induction algorithm. In order to efficiently control the direction angle, a gain related to the look ahead distance concept is introduced. Most of UAVs have the limited maximum curvature due to the structural constraints. A numerical simulation is conducted to follow the path generated by the sliding mode controller considering the angular velocity limit. The path generation and tracking performance is verified by comparing the suggested controller with conventional control techniques.