• 한국컴퓨터정보학회논문지
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• 제11권2호
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• pp.35-42
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• 2006

본 논문에서는 Parsec을 이용하여 병렬디지털신호처리용 분산공유메모리 다중처리시스템의 성능 분석을 위한 시뮬레이터를 구현한다. 이 시뮬레이터의 특징은 TMS320C6701 DSP 칩의 DMA 기능과 빠른 접근시간을 가진 지역메모리를 사용하는 시스템의 시뮬레이션에 적합하다는 것이다. 또한 시스템의 성능 매개변수 수정과 하드웨어 구성요소들에 대한 재구성이 쉽기 때문에 다양한 실행 환경에서 시스템의 성능을 분석할 수 있다. 시뮬레이션에서는 DSP 알고리즘에서 널리 사용하는 FET, 2D FET, Matrix Multiplication, Fir Filter를 사용하여 프로세서의 수 데이터 크기, 하드웨어 요소의 변화에 따른 실행 시간을 측정한다. 그리고 그 결과를 비교함으로써 본 논문에서 구현한 시뮬레이터의 성능을 검증한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권1호
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• pp.172-185
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• 2019

In this paper, we investigate the performance of the diffusion adaptation strategies for parameter estimation in wireless adaptive networks, where the nodes exchange information over noisy and fading wireless channels. This paper shows the differences between the effect of Rayleigh and Rician fading over wireless adaptive networks and proves that the Rician fading is a more practical model in such kinds of networks. Simulation results imply that the effect of Rayleigh fading is more degrading for the estimation process than Rician fading. Also, the simulation results show the performance of adapt then combine (ATC) diffusion algorithm is better than the combine then adapt (CTA) algorithm by merely considering noise in wireless channels. While the performance of CTA prevails ATC over the wireless adaptive network in the presence of noise plus channel fading.

• Steel and Composite Structures
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• 제38권5호
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• pp.583-597
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• 2021

This article develops a nonclassical model to analyze bending response of squared perforated microbeams considering the coupled effect of microstructure and surface stress under different loading and boundary conditions, those are not be studied before. The corresponding material and geometrical characteristics of regularly squared perforated beams relative to fully filled beam are obtained analytically. The modified couple stress and the modified Gurtin-Murdoch surface elasticity models are adopted to incorporate the microstructure as well as the surface energy effects. The differential equations of equilibrium including the Poisson's effect are derived based on minimum potential energy. Exact closed form solution is obtained for bending behavior of the proposed model considering the classical and nonclassical boundary conditions for both uniformly distributed and concentrated loads. The proposed model is verified with results available in the literature. Influences of the microstructure length scale parameter, surface energy, beam thickness, boundary and loading conditions on the bending behavior of perforated microbeams are investigated. It is observed that microstructure and surface parameters are vital in investigation of the bending behavior of perforated microbeams. The obtained results are supportive for the design, analysis and manufacturing of perforated nanobeams that commonly used in nanoactuators, nanoswitches, MEMS and NEMS systems.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권12호
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• pp.4567-4583
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• 2021

This study proposes an analytical approximation algorithm based on extreme value theory (EVT) for the inverse of the power of the incomplete Gamma function. First, the Gumbel function is used to approximate the power of the incomplete Gamma function, and the corresponding inverse problem is transformed into the inversion of an exponential function. Then, using the tail equivalence theorem, the normalized coefficient of the general Weibull distribution function is employed to replace the normalized coefficient of the random variable following a Gamma distribution, and the approximate closed form solution is obtained. The effects of equation parameters on the algorithm performance are evaluated through simulation analysis under various conditions, and the performance of this algorithm is compared to those of the Newton iterative algorithm and other existing approximate analytical algorithms. The proposed algorithm exhibits good approximation performance under appropriate parameter settings. Finally, the performance of this method is evaluated by calculating the thresholds of space-time block coding and space-frequency block coding pattern recognition in multiple-input and multiple-output orthogonal frequency division multiplexing. The analytical approximation method can be applied to other related situations involving the maximum statistics of independent and identically distributed random variables following Gamma distributions.

• 대한전자공학회논문지SP
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• 제47권3호
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• pp.23-31
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• 2010

모바일 영상 서비스와 센서 네트워크와 같은 저전력, 저복잡도의 비디오 부호기를 필요로 하는 분야의 수요가 증대됨에 따라 프레임간의 상관성을 이용하지 않고 압축함으로써 낮은 복잡도로도 높은 압축률을 얻을 수 있는 분산 비디오 코딩에 대한 연구가 활발하게 진행되고 있다. 분산 비디오 코딩에서 부호기는 오류정정 부호기를 이용하여 원래 영상보다 압축된 형태의 신드롬을 생성한다. 반면, 복호기에서는 원본 영상을 추정하고 부호기에서 만들어진 신드롬을 이용하여 추정한 원본 영상의 오류를 정정한다. 이 때, 추정된 원본 영상을 보조 정보라 하며, 보조 정보는 원본 영상이 가상의 상관 채널을 통해 얻어진 영상이라 해석할 수 있다. 분산 비디오 코딩의 성능 향상을 위해서는 오류 정정 복호기와 최적 복원과정의 성능향상이 필요하며, 두 과정 모두 가상의 상관 채널의 정확도에 영향을 받는다. 본 논문에서는 오류 정정 복호기와 복원과정에서 최적의 입력값을 예측하기 위하여, 상관 채널의 구성 파라미터의 정확한 추정을 위한 효과적인 알고리즘들을 제안한다. 일반적으로 상관 채널은 라플라시안 분포로 모델링 되는데, 이 분포와 실제 채널 측정값과의 자승오류를 최소화 하는 알고리즘인 최소자승법 및 복잡도를 낮춘 변형된 알고리즘을 제안하였다. 또한, 신뢰구간 설정으로 기존의 채널 파라미터 추정 알고리즘을 사용할 때 오류를 줄이는 방법을 제안하였다. 제안된 알고리즘으로 Mother 영상과 Foreman 영상에서 각각 최대 PSNR이득 1.8 dB와 1.1 dB를 얻었으며, 특히 상관도가 낮은 영역에서 더 효과적인 성능 개선을 보인다.

• KIEE International Transaction on Systems and Control
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• 제2D권2호
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• pp.78-91
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• 2002

In the thermal power plant, there are six manipulated variables: main steam flow, feedwater flow, fuel flow, air flow, spray flow, and gas recirculation flow. There are five controlled variables: generator output, main steam pressure, main steam temperature, exhaust gas density, and reheater steam temperature. Therefore, the thermal power plant control system is a multinput and output system. In the control system, the main steam temperature is typically regulated by the fuel flow rate and the spray flow rate, and the reheater steam temperature is regulated by the gas recirculation flow rate. However, strict control of the steam temperature must be maintained to avoid thermal stress. Maintaining the steam temperature can be difficult due to heating value variation to the fuel source, time delay changes in the main steam temperature versus changes in fuel flow rate, difficulty of control of the main steam temperature control and the reheater steam temperature control system owing to the dynamic response characteristics of changes in steam temperature and the reheater steam temperature, and the fluctuation of inner fluid water and steam flow rates during the load-following operation. Up to the present time, the Proportional-Integral-Derivative Controller has been used to operate this system. However, it is very difficult to achieve an optimal PID gain with no experience, since the gain of the PID controller has to be manually tuned by trial and error. This paper focuses on the characteristic comparison of the PID controller and the modified 2-DOF PID Controller (Two-Degrees-Freedom Proportional-Integral-Derivative) on the DCS (Distributed Control System). The method is to design an optimal controller that can be operated on the thermal generating plant in Seoul, Korea. The modified 2-DOF PID controller is designed to enable parameters to fit into the thermal plant during disturbances. To attain an optimal control method, transfer function and operating data from start-up, running, and stop procedures of the thermal plant have been acquired. Through this research, the stable range of a 2-DOF parameter for only this system could be found for the start-up procedure and this parameter could be used for the tuning problem. Also, this paper addressed whether an intelligent tuning method based on immune network algorithms can be used effectively in tuning these controllers.

• Journal of Power Electronics
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• 제15권5호
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• pp.1305-1317
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• 2015

Distributed generation systems (DGSs) have been getting more and more attention in terms of renewable energy use and new generation technologies in the past decades. The self-excited induction generator (SEIG) occupies an important role in the area of energy conversion due to its low cost, robustness and simple control. Unlike synchronous generators, the SEIG has to absorb capacitive reactive power from the outer device aiming to stabilize the terminal voltage at load changes. This paper presents a novel static VAR compensator (SVC) called a magnetic energy recovery switch (MERS) to serve as a voltage controller in SEIG powered DGSs. In addition, many small scale SEIGs, instead of a single large one, are applied and devoted to promote the generation efficiency. To begin with, an expandable mathematic model based on a d-q equivalent circuit is created for parallel SEIGs. The control method of the MERS is further improved with the objective of broadening its operating range and restraining current harmonics by parameter optimization. A hybrid control strategy is developed by taking both of the stand-alone and grid-connected modes into consideration. Then simulation and experiments are carried out in the case of single and double SEIG(s) generation. Finally, the measurement results verify that the proposed DGS with SVC-MERS achieves a better stability and higher feasibility. The major advantages of the mentioned variable reactive power supplier, when compared to the STATCOM, include the adoption of a small DC capacitor, line frequency switching, simple control and less loss.

• 한국정보통신학회논문지
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• 제27권1호
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• pp.109-116
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• 2023

본 논문에서는 다중 리더 에이전트와 추종 에이전트들로 구성된 2차 다중 에이전트 시스템의 봉쇄제어 문제를 연구하였다. 봉쇄제어의 목표는 추종 에이전트들을 다중 리더 에이전트들에 의해 생성되는 convex hulll을 추종하도록 하는 데에 있다. 따라서 리더 에이전트들에 의해 전체 그룹을 제어함으로써 다중 에이전트 시스템의 군집 행동을 얻을 수 있다. 본 논문에서 리더 에이전트들은 일정한 속도로 움직이고 추종 개체들은 입력 포화가 존재하는 경우를 고려하였다. 또한 추종 에이전트들은 이웃한 에이전트들과 상태 정보를 교환할 수 있고, 이웃과의 상대 상태 정보만 이용 가능하다 가정하였다. 이러한 가정하에 움직이는 리더 에이전트들을 고려한 봉쇄제어 문제를 해결하기 위해 비례-적분 기반의 분산제어 알고리즘을 제안하였다. 또한, 라살레 불변의 법칙을 기반으로 추종 에이전트들의 리더 에이전트들에 의해 생성되는 convex hull로 수렴을 보장하는 제어 이득들에 대한 조건들을 조사하였고 시스템 파라미터의 정보만으로 설계할 수 있음을 보였다. 마지막으로 모의실험을 통한 이론적 결과를 검증하였다.

• Animal cells and systems
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• 제3권3호
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• pp.303-309
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• 1999

Inter- and intraspecific genetic relationships between Rana amurensis from Korea and Russia and other brown frogs were investigated by nucleotide sequence of a 504 base pair (bp) fragment of the mitochondrial cytochrome b gene. Nucleotide sequence similarities among Korean populations of R. amurensis ranged from 99.6% to 97.6% and 98.8% within Russian populations. The nucleotide sequence similarity between Korean and Russian R. amurensis ranged from 86.9% to 85.5%. Based on Kimura-2-parameter distance, the sequence divergence between R. amurensis from Korea and Russia was 16.18% and 18.04% among other related brown frogs. interspecific sequence divergences among R. amurensis and other related brown frogs diverged by 20.3%. Using an estimate of 2-4% mitochondrial DNA sequence divergence per million years, Korean and Russian R. amurensis diverged about 8 to 4 million years ago (Mya) and other brown frogs diverged about 9 to 5 Mya from ancestral frogs and distributed from North Asia to Sakhalin in a short time. In the neighbor-joining and UPGMA tree R. amurensis was clustered into two groups with Korean and Russian populations and the other brown frogs were grouped separately with diverged trichotomous clusters (R. dybowskii and R. pirica, R. okinavana and R. tsushimensis, and R. japonica and R. longicrus).

• 한국안전학회지
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• 제27권1호
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• pp.1-6
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• 2012

복잡한 지하철 역사에서 공기질은 승객의 안전과 건강을 좌우하는 중요한 요소이다. $CO_2$, VOCs먼지, 미생물 등의 농도는 역사의 여러 지점에서뿐만 아니라 원격지점에서도 감시 및 제어가 가능해야 하기 때문에 유무선 네트워크를 사용한 웹기반 감시 및 제어가 필요하다. 가상디바이스 네트워크(VDN) 개념에 근거한 원격 무선센서 네트워크와 디바이스 네트워크(LonWorks)를 IP 네트워크에 연동시키면 매우 강력한 분산 감시 및 제어 성능을 제공한다. 본 연구에서는 지하철역사내 공기질 감시 및 제어를 위한 유무선 네트워크의 성능평가를 실시하였다. 특히 유무선 네트워크의 데이터 전송과 지연특성을 평가하고 승객의 안전과 건강을 위한 핵심요소를 확인하였다.