• 대한기계학회논문집
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• 제10권4호
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• pp.442-449
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• 1986

본 연구에서는 소음원 및 진동원을 규명하기 위하여 사용되어 온 종래의 주파 수응답함수(Frequency Response Function`FRF)법과 소음원 및 진동원 간에 강한 상관 관계가 존재한 경우에 사용되는 기여도함수(coherence function)법을 이용한 다차원 스텍트럼해석(Multi-Dimensional Spectral Analysis`MDSA)법에 의하여 가속도응답 및 방사음과의 기여관계를 규명하였다.

• 전력전자학회논문지
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• 제22권4호
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• pp.285-296
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• 2017

This paper proposes an improved modulation scheme for the medium voltage modular multi-level converter (MMC), which operates in the nearest level control and applies in the medium voltage direct current (MVDC) system. In the proposed modulation scheme, the offset (neutral-to-zero output) voltage is adjusted, with the phase voltage magnitude, thereby maintaining a constant value with N+1 level in the controllable modulation index (MI) range. In order to confirm the proposed scheme's validity, computer simulations for the 22.9 kV - 25 MVA MMC were performed with PSCAD/EMTDC, as well as hardware experiments for the 380 V - 10 kVA MMC. The proposed modulation scheme offers to build a constant pole voltage regardless of the MI value, and to build a phase voltage with improved total harmonic distortion (THD).

• 대한전기학회논문지:전력기술부문A
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• 제55권11호
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• pp.492-497
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• 2006

Nash Equilibrium (NE) is essential to investigate a participant's bidding strategy in a competitive electricity market. The transmission line constraints make it difficult to compute the NE due to causing a mixed strategy NE instead of a pure strategy NE. Computing a mixed strategy is more complicated in a multi-player game. The competition among multi-participants is modeled by a two-level hierarchical optimization problem. A mathematical programming approach is widely used in finding this equilibrium. However, there are difficulties to solving a mixed strategy NE. This paper presents two propositions to add heuristics to the mathematical programming method. The propositions are based on empirical studies on mixed strategies in numerous sample systems. Based on the propositions a new formulation is provided with a set of linear and nonlinear equations, and an algorithm is suggested for using the prepositions and the newly-formulated equations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권4호
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• pp.1693-1713
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• 2018

An important technique used by database administrators (DBAs) is to improve performance in decision-support workloads associated with a Star schema is multi-level partitioning. Queries will then benefit from performance improvements via partition elimination, due to constraints on queries expressed on the dimension tables. As the task of multi-level partitioning can be overwhelming for a DBA we are proposing a wizard that facilitates the task by calculating a partitioning scheme for a particular workload. The system resides completely on a client and interacts with the costing estimation subsystem of the query optimizer via an API over the network, thereby eliminating any need to make changes to the optimizer. In addition, since only cost estimates are needed the wizard overhead is very low. By using a greedy algorithm for search space enumeration over the query predicates in the workload the wizard is efficient with worst-case polynomial complexity. The technology proposed can be applied to any clustering or partitioning scheme in any database management system that provides an interface to the query optimizer. Applied to the Teradata database the technology provides recommendations that outperform a human expert's solution as measured by the total execution time of the workload. We also demonstrate the scalability of our approach when the fact table (and workload) size increases.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권6호
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• pp.3208-3229
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• 2017

Rectification is an essential procedure for simplifying the disparity extraction of stereo matching algorithms by removing vertical mismatches between left and right images. To support real-time stereo matching, studies have introduced several look-up table (LUT)- and computational logic (CL)-based rectification approaches. However, to support high-resolution images, the LUT-based approach requires considerable memory resources, and the CL-based approach requires numerous hardware resources for its circuit implementation. Thus, this paper proposes a multi-level accumulation-based rectification method as a simple CL-based method and its circuit implementation. The proposed method, which includes distortion correction, reduces addition operations by 29%, and removes multiplication operations by replacing the complex matrix computations and high-degree polynomial calculations of the conventional rectification with simple multi-level accumulations. The proposed rectification circuit can rectify $1,280{\times}720$ stereo images at a frame rate of 135 fps at a clock frequency of 125 MHz. Because the circuit is fully pipelined, it continuously generates a pair of left and right rectified pixels every cycle after 13-cycle latency plus initial image buffering time. Experimental results show that the proposed method requires significantly fewer hardware resources than the conventional method while the differences between the results of the proposed and conventional full rectifications are negligible.

• 전기학회논문지P
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• 제65권4호
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• pp.326-334
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• 2016

In this paper for developing and implementing the realtime HD level video streaming transmitter which is operated on the multi-platform in all network and client environment compared to the exist video live streaming transmitter. We design the realtime HD level video streaming transmitter supporting the multi-platform using the TMS320DM386 video processor of T.I company and then porting the Linux kernel 2.6.29 and implementing the RTSP(Real Time Streaming Protocol)/RTP(Real Time Transport Protocol), HLS(Http Live Streaming), RTMP(Real Time Messaging Protocol) that can support the multi-platform of video stream protocol of the received equipments (smart phone, tablet PC, notebook etc.). For proving the performance of developed video streaming transmitter, we make the testing environment for testing the performance of streaming transmitter using the notebook, iPad, android Phone, and then analysis the received video in the client displayer. In this paper, we suggest the developed the Realtime HD(High Definition) level Video Streaming transmitter performance data values higher than the exist products.

• 전력전자학회논문지
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• 제12권2호
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• pp.139-148
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• 2007

본 논문에서는 3상 저주파 변압기를 이용한 절연형 멀티레벨 인버터를 제안한다. 제안된 인버터는 3상 절연형 변압기를 이용함으로 비절연형 멜티레벨 인버터와 달리 단일 직류 전원을 사용할 수 있는 장점이 있으며, 기존의 단상 변압기를 이용한 3상 멀티레벨 인버터에 비하여 변압기의 수를 줄일 수 있다. 또한 출력 기본주파수와 동일한 스위칭 주파수로 동작하는 스위칭 각 제어 방식을 통하여 출력 전압의 저차 고조파 성분과 스위치 손실을 줄일 수 있었다. Matlab을 이용한 시뮬레이션 및 실험을 통하여 제안된 방식의 타당성을 검증 하였다.

• 한국정보처리학회논문지
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• 제6권10호
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• pp.2809-2815
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• 1999

Level set, and active contour(snakes) models are extensively used for image segmentation or shape extraction in computer vision. Snakes utilize the energy minimization concepts, and level set is based on the curve evolution in order to extract contours from image data. In general, these two models have their own drawbacks. For instance, snake acts pooly unless it is placed close to the wanted shape boundary, and it has difficult problem when image has multiple objects to be extracted. But, level set method is free of initial curve position problem, and has ability to handle topology of multiple objects. Nevertheless, level set method requires much more calculation time compared to snake model. In this paper, we use good points of two described models and also apply multi resolution algorithm in order to speed up the process without decreasing the performance of the shape extraction.

• 정보처리학회논문지B
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• 제11B권6호
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• pp.633-644
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• 2004

본 논문에서는 기존 NTSS 알고리즘을 다중해상도(MR : Multiple Resolution)기법을 이용하여 NTSS-3 레벨 알고리즘으로 제안하였다. 고속 블록정합 알고리즘은 패턴 방식에 따라 속도에 많은 영향을 미치는데 본 논문에서는 기존 NTSS의 패턴 방식과 다른 다중해상도 기법을 이용한 레벨에 따른 블록정합 알고리즘을 제안하였다. 블록 정합알고리즘에서 국부최소화 문제(Local minima problem)로 발생하는 화질 저하를 개선하기 위해 MC(Multiple Candidate)라는 다중후보를 이용하였다. 실험 결과 제안한 기법을 FS와 비교하면 16배의 탐색 속도론 나타내었고 기존 고속 블록 정합 알고리즘인 NTSS 방식에 비교 할 때 PSNR값에 있어서는 0.11-0.12(dB) 화질이 개선되었으며 속도 면에서도 0.1배 향상되었고 탐색점 대비 화질개선이 우수함을 나타내었다.

• 정보처리학회논문지A
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• 제12A권5호
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• pp.375-384
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• 2005

연성 실시간 특성을 가진 멀티미디어 응용 프로그램이 일정한 서비스 품질을 유지하고 수행되기 위해서는 커널 수준과 사용자 수준에서 실시간 처리를 요구한다. 본 연구에서는 널리 사용되는 범용 운영체제 환경에서 멀티미디어를 지원하는데 있어서 문제가 되는 부분을 살펴보고 이를 개선할 수 있는 다단계 스케줄러를 제안한다. 다단계 스케줄러는 사용자 피드백을 기반으로 스케줄링 정보를 생성하는 상위 스케줄러와 커널에 구현된 하위 스케줄러로 구성된다. 제안한 다단계 스케줄러를 리눅스에서 구현하고 성능 분석을 수행하였으며, 실험 결과, 제안한 방식이 시스템에 성능 저하를 발생시키지 않으면서 멀티미디어의 서비스 품질을 일정하게 보장하는 것을 확인하였다.