• Geophysics and Geophysical Exploration
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• v.9 no.1
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• pp.86-92
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• 2006

The full-waveform inversion algorithm using normalised seismic wavefields can avoid potential inversion errors due to source estimation required in conventional full-waveform inversion methods. In this paper, we have modified the inversion scheme to install a weighted smoothness constraint for better resolution, and to implement a staged approach using normalised wavefields in order of increasing frequency instead of inverting all frequency components simultaneously. The newly developed scheme is verified by using a simple two-dimensional fault model. One of the most significant improvements is based on introducing weights in model parameters, which can be derived from integrated sensitivities. The model-parameter weighting matrix is effective in selectively relaxing the smoothness constraint and in reducing artefacts in the reconstructed image. Simultaneous multiple-frequency inversion can almost be replicated by multiple single-frequency inversions. In particular, consecutively ordered single-frequency inversion, in which lower frequencies are used first, is useful for computation efficiency.

• Journal of KIISE:Computer Systems and Theory
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• v.35 no.6
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• pp.273-283
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• 2008

Many embedded real-time systems have adopted processors supported with dynamic voltage scaling(DVS) recently. Power is one of the important metrics for optimization in the design and operation of embedded real-time systems. We can save considerable energy by using slowdown of processor supported with DVS. In this paper, we propose heuristic algorithms to calculate task slowdown factors for an efficient energy consumption in embedded real-time systems with task synchronization. The previous algorithm has a following constraint : given the tasks are ordered in a nondecreasing order of their relative deadline, the task slowdown factors computed are in a nonincreasing order. In this paper, we relax the constraint and propose heuristic algorithms which have the same time complexity that previous algorithm has and can save more energy. Experimental results show that the proposed algorithms are energy efficient.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.138-144
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• 2020

The Army's engineers are carrying out a range of operations using various equipment, of which, artillery unit support is the representative engineering operation field. The main task of the artillery unit is to attack the enemy's center with firepower from the rear of a friendly force. The artillery must move its original position after firing several times to prevent exposure of the shooting position. This paper proposed a mathematical model and heuristic algorithm that can be used to determine the optimal allocation among engineer equipment, the team (work), and position while reflecting the constraints of the construction of an artillery position. The model proposed in this paper derived the optimal solution for the small size problems, but it takes a long time to derive the optimal solution for the problem of equipment placement of the engineer battalion and brigade scale. Although the heuristic suggested in this study does not guarantee the optimal solution, the solution could be obtained in a reasonable amount of time.

• Journal of Digital Convergence
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• v.11 no.5
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• pp.291-298
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• 2013

Metering scheme is composed of servers, clients, and an audit agency who collects the information for the clients which have been processed by servers. Although many efficient and secure metering schemes have been proposed in the literature, they do not consider the client privacy issue. To mitigate this limitation of the related work, we propose a metering scheme to protect the privacy of clients in internet. More specifically, we apply RSA based blind signature to the interaction between client and audit agency. If a client spends metering information to the server more than twice, the identity of the client is revealed by the server or audit agency.

• Journal of KIISE:Computer Systems and Theory
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• v.30 no.1
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• pp.1-11
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• 2003

Fragmentation is the main performance bottleneck of large, multi-user multicomputer system. This paper presents an L-Shaped Submesh Allocation(LSSA) strategy, which lifts the restriction on the rectangular shape formed by allocated processors in order to address the problem of fragmentation. LSSA can manipulate the shape of the required submesh to fit into the fragmented mesh system. Thus, LSSA accommodates incoming jobs faster than other strategies and results in the reduction of job response time. Extensive simulations show that LSSA performs more efficiently than other strategies in terms of the external fragmentation, the job response time and the system utilization.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.4
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• pp.873-879
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• 2012

Recently the cloud computing paradigm has been widely accepting in various applications. Data management system of cloud computing requires ability to manage tremendous data and supporting scalability. The former can be achieved by weaken consistency and limitation of transactions, and the latter needs expand or shrink of components. In this paper, we propose a transaction processing model and a scalable module management algorithm when transaction is executed in the cloud. Transaction processing model consists of a transaction management module and a data management module. Scalable module management algorithm has no redistribution of components and may alleviates loads of existed modules. With simulation results, we can see the improvement of response time and decrease abort ratio of transactions.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1217_1218
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• 2009

현재 국내를 비롯하여 세계적으로 녹색성장, 친환경 등의 열풍이 고유가와 화석연료의 고갈위기와 맞물려 활발히 진행되고 있다. 이미 미국, 영국, 프랑스, 이태리, 일본 등의 선진국에서는 자연 친화적, 경제적 실리 추구 및 편리성을 추구하면서 청정 에너지를 사용하는 "미래형 이동수단"에 큰 관심을 갖고 우리보다 한발 앞서 나가고 있다. 2005년 2월 16일 발효된 기후변화의 주 요인인 온실가스 배출 감축을 위한 교토의 정서 또한 이러한 친환경이란 말과 무관하지 않다. 교토의정서의 발효 이후 세계 각국은 의무화된 규제조항을 만족하기 위해 막대한 자본을 투입하고 있다. 우리나라의 경우 온실가스 배출량이 세계 9위에 달하고 있으며, 전체 온실가스 배출량의 82.5% 정도가 화석에너지의 사용에 의해 발생되고 있다. 이중 이산화탄소의 경우 전체 배출량의 27%를 자동차에서 배출되며, 이로 인해 세계 각국에서는 자동차에서의 배출가스를 규제하는 조항을 법제화하고 있다. 이러한 규제는 앞서 미국의 경우 캘리포니아 주정부에서 1998년부터 전기자동차 사용을 의무화하는 ZEV 규제를 입법화하면서 본격화되었고, 무공해 및 저공해 자동차의 개발이 활발하게 진행되었다. 또한 고유가 시대로 접어들면서 대체에너지에 대한 필요성이 한층 고조되고 있는 실정이다. 이중 전기자전거는 배터리를 통해 무공해, 무소음이라는 장점을 가지고 있으며, 유지관리비가 거의 들지 않고 교통체증을 완화시켜주며, 주차에 신경쓰지 않아도 되어 교통수단에 혁신을 가져다 줄 것이라 생각된다. 또한 전기자전거의 경우 배터리를 동력원으로 사용하며 전동스쿠터 등에서의 문제점인 일충전 주행거리에 제약을 받지 않아 최근 중국 등에서 보급이 급격히 확산되고 있는 추세에 있다. 하지만 대부분 납축전지, 니켈-카드뮴 등의 배터리가 사용되고 있어 중량, 수명, 중금속에 의한 환경오염 등의 다양한 문제점을 내포하고 있다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.777-780
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• 2011

The supersonic wind tunnel is a common facility to studies the aerodynamic phenomenon around the high speed vehicle or weapon system whose operating speed is greater than sonic speed. In this study, a design procedure and selecting the components of a new supersonic wind tunnel whose nozzle exit is $125mm{\times}100mm$ is considered. An operating test of this wind tunnel is being conducted to compare the result with the design values, mach number, etc.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.106-106
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• 2011

지표면으로 입사하는 태양 복사 에너지를 정확하게 산출하는 것은 에너지 수지 방법을 이용한 유역 분석의 신뢰도를 높이는데 기여할 수 있다. 태양 복사 에너지는 지형 인자와 대기 인자를 이용하여 산정할 수 있으나 기상관측장비 특성상 지점값 위주의 연구가 이루어지고 있다. 본 연구에서는 이러한 공간적 제약을 완화하기 위해 원격탐사 기법을 이용하여 지표면에 들어오는 태양 복사 에너지를 산출하고자 하였다. 시간, 공간적으로 중규모 해상도를 가지고 있는 Moderate Resolution Imaging Spectroradiometer(MODIS) 위성 관측 이미지를 이용하여 태양 복사 에너지의 시공간 분포를 산정하고 그 결과를 연구 지역인 광릉/해남 KoFlux site의 지상 관측값을 이용하여 검증함으로써 산정 모형의 국내 적용성을 확인하였다. 비교적 적은 수의 인자를 필요로 하는 Allen et al.(2007) 태양 복사 에너지 산정 모형과 36가지의 서로 다른 파장 이미지를 이용하여 산출된 MODIS 대기 자료를 이용하여 결과를 산정함으로써 모형의 간편성 및 효율성을 확인할 수 있었다. 특히 광릉/해남 KoFlux site 관측치와 모형 산정값과의 상관계수가 각각 0.95, 0.96으로 매우 높은 값을 가짐으로써 모형의 높은 신뢰성을 검토하였다. 향후 연구의 결과로써 얻어진 태양 복사 에너지의 시공간 분포특성 분석을 통해 에너지 수지 방법의 정확성을 향상시키고자 한다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.2
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• pp.51-55
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• 2015

In this paper, we proposed scheme that obtain diversity gain in the cooperative communication to mitigate, applied to the effects of fading in the vehicle communication. Relay used bus that can available in the city environment. In addition, we applied the double rayleigh fading environment so that can applied in real-environments. Therefore, proposed scheme through this paper applied to vehicle communication, user can acquire a high quality service and the operation efficiency of the network is improved. Finally, performance of the proposed protocol is analyzed in terms of bit error rate.