• International Journal of Aeronautical and Space Sciences
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• 제18권1호
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• pp.70-81
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• 2017

Various components of an engine nozzle are modeled as flexible multi-body components that are operated under high temperature and pressure. In this paper, in order to predict complex behavior of an engine nozzle, thermo-fluid-flexible multi-body dynamics coupled analysis framework was developed. Temperature and pressure on the nozzle wall were obtained by the steady-state flow analysis for a two-dimensional nozzle. The pressure and temperature-dependent material properties were delivered to the flexible multi-body dynamics analysis. Then the deflection and strain distribution for a nozzle configuration was obtained. Heat conduction and thermal analyses were done using MSC.NASTRAN. The present framework was validated for a simple nozzle configuration by using a one-way coupled analysis. A two-way coupled analysis was also performed for the simple nozzle with an arbitrary joint clearance, and an asymmetric flow was observed. Finally, the total strain result for a realistic nozzle configuration was obtained using the one-way and two-way coupled analyses.

• 한국통신학회논문지
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• 제39B권7호
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• pp.425-432
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• 2014

본 논문은 멀티채널과 멀티웨이 구조를 가진 SSD의 구조적 특성을 감안한 웨어레벨링 알고리듬을 제안한다. 제안된 알고리듬은 쓰기 요청이 도착했을 때 DRAM에 저장된 데이터를 논리주소 접근 빈도에 따라 핫 데이터와 콜드 데이터로 나누고, 블록 소거횟수의 편차를 줄이도록 데이터를 할당한다. 콜드 데이터를 소거횟수가 많은 블록에 할당하여 소거횟수 증가를 억제한다. 멀티채널과 멀티웨이 구조의 SSD 시뮬레이터에 다양한 어플리케이션에서 얻어진 트레이스를 적용하여 검증한 결과, 기존의 웨어레벨링 알고리듬을 사용하는 경우에 비해 블록의 소거횟수의 차이가 평균 9.3% 줄어들고 총 소거횟수가 평균 4.6% 감소하였다.

• 한국통계학회:학술대회논문집
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• 한국통계학회 2005년도 추계 학술발표회 논문집
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• pp.59-65
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• 2005

We propose five Bayesian methods to estimate the cell expectation in an incomplete multi-way categorical table with nonignorable nonresponse mechanism. We study 3 Bayesian methods which were previously applied to one-way categorical tables. We extend them to multi-way tables and, in addition, develop 2 new Bayesian methods for multi-way categorical tables. These five methods are distinguished by different priors on the cell probabilities: two of them have the priors determined only by information of respondents; one has a constant prior; and the remaining two have priors reflecting the difference in the response mechanisms between respondent and non-respondent. We also compare the five Bayesian methods using a categorical data for a prospective study of pregnant women.

• Management Science and Financial Engineering
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• 제7권1호
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• pp.27-39
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• 2001

The multi-projective model considers attributes and the relationships among attributes called projections. The critical features of the multi-projective model are the way of relating attributes in the description of the system, the way of reasoning incomplete projections, and the determination of connected patterns between projection. In order to get a full picture of the system, we build a set of projections. The multi-projective model can be thought of as projections of a multi-dimensional reality onto simplified “model space”. The multi-projective database modeling approach used in this paper unified the ideas and terminology of various database models. Most importantly, the multi-projective modeling is presented as a tool of database design in the relational and other database models.

• 한국정보통신학회논문지
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• 제24권11호
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• pp.1550-1553
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• 2020

In this paper, we maximize the lifetime of a multi-hop path through a cooperative wireless energy sharing scheme between constituent nodes in a wireless multi-hop communication. Considering a bidirectional multi-hop communication environment, we present an optimization problem to maximize path lifetime by adjusting the amount of energy each node needs to share with its neighboring nodes. On the basis of solidarity property, i.e., the lifetime of the multi-hop path is maximized when the lifetimes of all nodes are the same, we convert the considered optimization problem into a linear programming problem and solve it easily. Simulation result shows that the proposed two-way wireless energy sharing method maximizes the path lifetime of multi-hop communications and approximately doubles the path lifetime compared with the one-way energy sharing method.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2010년도 추계학술대회
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• pp.465-467
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• 2010

This paper proposes MIMO two-way cooperative relay scheme to optimize the end to end capacity in wireless multi-hop mesh network. The basic idea is to perform data transmission via multi-hop relay nodes, in equidistant topology, this method is quite efficient. However, on one hand this topology is very rare in practical situation, on the other hand, in real practical situation where the topology is most likely non equidistant, the end to end capacity significantly degrades due to bottleneck link caused by uneven SNR. Moreover, the end to end capacity degrades at high SNR due to overreach interference from far nodes existing in multi-hop relay networks. In this paper, MIMO two-way cooperative relay in the region of non equidistant nodes is found efficient to improve the end to end capacity. The proposed scheme is validated using numerical simulation.

• Journal of information and communication convergence engineering
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• 제12권2호
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• pp.67-74
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• 2014

In multi-hop communication systems, two-way relaying is one of the solutions to mitigate the spectral efficiency loss caused by a half-duplex transmission. In this paper, a simple two-way relaying scheme is proposed for two-hop two-user multiple input multiple output (MIMO) systems. In the proposed system, a base station and a relay station (RS), both equipped with two antennas, form a point-to-point MIMO channel, while the RS and two single-antenna mobile users form a point-to-multipoint multiuser (MU)-MIMO channel. Numerical examples show that the proposed system achieves a significant sum rate gain as compared to a one-way relaying system as the distance between a relay and the two users decreases. We also show that although we can expand the proposed scheme to more than two users, its performance gain as compared to that of one-way relaying decreases with an increase in the number of users.

• 한국정보과학회논문지:데이타베이스
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• 제30권6호
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• pp.593-605
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• 2003

공간 조인은 일반적으로 많은 처리 시간을 필요로 하므로 공간 조인에 대한 처리 시간을 단축하기 위해 많은 연구가 있었다. M-다중 공간 조인에서 M 개의 R-트리를 동시에 탐색하는 M-다중 R-트리 조인(MRJ)도 그 중의 하나이다. 본 논문에서는 M-다중 공간 조인에서 간접 술어(indirect predicate)개념을 소개한다. 다중 공간 조인에서 간접 술어란 질의 조건문에 직접 나타나는 술어가 아니라 이들 직접 술어들로부터 간접적으로 유도되는 술어를 말한다. 간접 술어 개념을 M-다중 R-트리 조인에 적용함으로서 다중 공간 조인의 성능을 향상시킬 수 있다. 우리는 이러한 간접 술어를 이용한 다중 공간 조인 처리 방법을 간접 술어 여과(IPF)라 부른다. 가공 데이타와 실제 지도 데이타를 이용한 실험을 통하여 우리는 IPF 기법이 M-다중 R-트리 조인의 성능을 상당히 개선한다는 것을 보였다.

• 한국통신학회논문지
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• 제39C권7호
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• pp.566-572
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• 2014

본 논문에서는 다중 선박으로 구성된 해양 네트워크에서 선박 간 통신 거리를 확장하면서 전송률을 향상시키는 양방향 다중-홉 릴레이 기법을 제안한다. 제안 기법은 두 단계 디지털 네트워크 부호화를 기반으로 각 선박의 데이터 전송 순서와 네트워크 부호화 순서를 알맞게 설계하여 데이터 교환에 필요한 시간 슬롯 수를 줄인다. 모의실험 결과 제안하는 양방향 다중 홉 릴레이 기법은 기존 기법의 전송률을 약 5/3배 향상시킴을 볼 수 있다.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제4권1호
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• pp.34-39
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• 2004

Huffman coding which has been used in many data compression algorithms is a popular data compression technique used to reduce statistical redundancy of a signal. It has been proposed that the Huffman algorithm can decode efficiently using characteristics of the Huffman tables and patterns of the Huffman codeword. We propose a new Huffman decoding algorithm which used a multi way tree search and present an efficient hardware implementation method. This algorithm has a small logic area and memory space and is optimized for high speed decoding. The proposed Huffman decoding algorithm can be applied for many multimedia systems such as MPEG audio decoder.