• Proceedings of the Korean Information Science Society Conference
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• 2004.10a
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• pp.595-597
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• 2004

점진적 검사점은 검사점 사이의 변경된 상태만을 기록하는 방식으로 검사점 오버헤드를 줄이는 기법으로 알려져 있다. 본 논문에서는 효율적인 점진적 검사점의 설계 내용과 함께 리눅스 커널 2.4.20에서 구현한 기법에 대해 설명한다. 이 논문에서 설명하는 점진적 검사점은 리눅스 운영체제에서 제공하는 페이지 쓰기 결함을 이용하여, 변경된 페이지만을 새로운 검사점에 저장한다. 이 점진적 검사점의 실험 결과는 비점진적 검사점을 사용한 것에 비하여 상당히 오버헤드를 줄일 수 있음을 보여준다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.11 s.353
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• pp.95-117
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• 2006

In this paper, we describe the optimization of the link-level performance and the complexity of floating-point and fixed-point methods in IEEE 802.16e OFDMA/TDD mobile modem. In floating-point design, we propose the channel estimation methods for downlink traffic channel and select the optimized method using computer simulation. So we also propose efficent algorithms for time and frequency synchronization, Digital Front End and CINR estimation scheme to optimize the system performance. Furthermore, we describe fixed-point method of uplink traffic and control channels. The superiority of the proposed algorithm is validated using the performances of Detection, False Alarm, Missing Probability and Mean Acquisition Time, PER Curve, etc. For fixed-point design, we propose an efficient methodology for optimized fixed-point design from floating-point At last, we design fixed-point of traffic channel, time and frequency synchronization, DFE block in uplink and downlink. The tradeoff between performance and complexity are optimized through computer simulations.

• Aerospace Engineering and Technology
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• v.4 no.2
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• pp.27-35
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• 2005

In this study, a performance analysis code was developed for the off-design performance analysis of air turbo ramjet(ATR) engine, and the analyses were performed for the pre-designed ATR engine at several operating points in the envelope. Variable intake and thrust nozzle were assumed to cover the wide envelope. Mathematical models for each components were developed to calculate their off-design performance. Simple design formulas were introduced for some components to explore the performance variation versus the design parameters. As a result, the pre-defined engine couldn't cover the entire mission profile. And it was also found that the effect of the pre-cooler was not very great, especially in the region of low Mach number.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.201-204
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• 2004

In this study, the GSP and in-house numerical codes have been used for analyses of the on-design, static off-design and dynamic off-design performances. Through the various missions including altitude, velocity, and power variations static engine performance have been investigated. The dynamic engine performances based on these complicated variations have been also analysed. Especially, the power, engine rpm and heat overload characteristics of a turbine have been estimated with the response time through the control of a throttle setting rather than a power setting. It could be applied to the FADEC system as an engine control device.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.62-67
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• 2004

This paper investigates the off-design performance of methane-fueled air turbo ramjet(ATR) engine in subsonic flight speed range. The ATR engine was modeled and simulated numerically. Each component was modeled to enable their off-design calculation. Compressor operating point was determined by flow matching with nozzle, and turbine by work matching. The ATR engine exhibited quite different off-design behavior compared to the conventional gas turbine engine.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.11c
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• pp.2341-2344
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• 2002

우편물량 처리에서 병목현상의 원인이 되고있는 수작업에 의한 순로구분 작업을 원활하고 신속하게 처리하며 집배원의 업무 부담을 경감시키기 위해 자동화가 시도되고 있다. 이러한 자동화된 순로구분기의 개발에 있어 순로구분에 필요한 주소 데이터 베이스를 관리하기 위해서는 각 배달지점에 대한 고유한 ID 부여가 필요하다. 따라서 본 논문에서는 아직 체계화되지 않은 한국 주소의 배달점 코드 설계 방안에 대해서 연구하였다. 먼저 해외 각국의 배달점 코드할당 방법을 알아보고, 배달점 코드의 기본 정의 및 설계 방향을 제시한다. 그리고 각 주소의 고유한 배달점 코드를 설계하는데 있어 여러 가지 방안을 제시하고 각 대안별 장단점 및 설계 방법을 제시하였으며 적합한 설계 방안을 선정하였다. 또한 기존의 주소체계뿐만 아니라 도입 예정인 새주소 체계와의 적합성도 고려하였다. 본 논문에서 제시한 우편번호 앞 3자리와 6자리의 일련번호를 연결한 배달점 코드가 현재의 한국 주소체계 뿐만 아니라 새주소 체계에도 적합할 것으로 판단된다. 마지막으로 몇 가지 적용 사례를 통한 제안한 방안들을 검증해 보았다.

• Journal of Aerospace System Engineering
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• v.13 no.1
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• pp.38-46
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• 2019

There is a growing interest in engine diagnostic technology for gas turbine engines. An engine simulation program, precisely simulating the engine performance, is required in order to apply it to the engine diagnosis technology for engine health monitoring. In particular, the simulation program can predict not only design point performance but also off-design point and partial load performance in accurate. So the engine simulation program for the 2-spool separate flow type turbofan engine was developed and the JT9D-7R4G engine of PW(Pratt & Whitney) was analyzed. The steady-sate performance analysis is conducted at both design and off-design points in flight path and the differences between analysis results of takeoff and cruise conditions are compared. The effect of Reynold's correction method was analyzed as a scaling method of the engine component performance. The simulation results was compared with NPSS.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.05a
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• pp.249-251
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• 2012

Augmented Reality (AR) enables the enhanced realism and interaction by providing the overlaid digital information on the user's view of the physical world. In this paper, we propose an AR-based ship design visualization system for presenting ship 3D model in smart phones or table PCs. The proposed system compute corner points and feature points by contour finding method and harris corner detector, and build a ship-design drawing database. By using SURF algorithm, key feature points are extracted from ship-design drawing image which is obtained by mobile camera. Then ship-design drawing image is recognized by matching the feature points stored in DB and extracted key feature points. 3D ship structures are visualized by overlaying the ship-design drawing image on the smart phone or table PC's screen. Compared to conventional 2D ship-design, proposed system helps to easily understand the structures of the ship and reduce the business design period. Thus, Enhanced competitiveness of business is expected.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.3
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• pp.12-18
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• 1994

Optimization in the engineering design is to select the best of many possible design alternatives in a complex design space. In order to optimize, various optimization methods have been used. One major problem of traditional optimization methods is that they often result in local optima. Recently genetic algorithm based on the mechanics of natural selection and natural genetics is used in many application fields for optimization. Genetic algorithm is more powerful to local optima, but it requires more calculation time and has difficulties in finding exact optimum point in design variable with real data type generally. In this paper. hybrid method was developed by coupling genetic algorithm and traditional direct search method. The developed method finds out a region for global optimum using genetic algorithm, and is to search global optimum using direct search method based on results obtained from genetic algorithm. By using hybrid method, calculation time is reduced and search efficient for optimum point is increased.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10b
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• pp.397-399
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• 2004

하나의 시스템의 아키텍처를 설계하기 위해서는 여러 아키텍처 스타일들이 복합적으로 결합하여 시스템의 전체적인 아키텍처를 구성하게 된다. 그러나 아키텍처 설계자 또는 개발자들이 아키텍처 설계 과정 중에 현재 설계된 아키텍처가 시스템의 요구사항을 적절히 반영하고 있는지 평가해 볼 수 있는 방법이 없다. 본 논문에서는 아키텍처 평가자와 다양한 이해관계자가 모여 아키텍처를 전반적으로 평가해 보기 전에 아키텍처 설계자가 설계과정 중에 자신이 담당한 부분의 현재의 아키텍처가 시스템의 요구사항을 적절히 반영하고 있는지 여부를 판단하여 설계 과정 중에 개선점을 도굴하고, 개선점을 재 설계에 반영하는 아키텍처 설계 방법론을 제안하고자 한다