• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4A
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• pp.193-199
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• 2003

In this paper, the performance of uplink WCDMA systems was analyzed using the SGA (Standard Gaussian Approximation) method and the SIGA(Simplified Improved Gaussian Approximation) method adopted for the performance analysis in conventional DS-CDMA systems. The performance of bandlimited WCDMA systems was analyzed using the SGA and SIGA method, and computer simulations were performed in AWGN environments having multiple access interference. It was shown that the performance analysis of uplink bandlimited WCDMA systems using the SIGa method may be very efficient through various computer simulations with verying spreading factors, roll-off factors, and signal-to-noise ratios.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.1
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• pp.1-7
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• 1999

In this paper, we use the FDTD method to analyze crosstalk characteristics for high speed pulse signal on MTL(Multi-Transmission Line) in time domain. The FDTD results are compared to the results of SPICE modeling method and the experimental result. The FDTD method has higher accuracy of results than other methods, and it can analyze transmission characteristics of MTL regard to loss of conductor. We analyze crosstalk characteristics for pulse on MTL for lossless and loss case.

• Optical Science and Technology
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• v.1 no.2
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• pp.56-64
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• 1997

본 기술해설에서는 초고속 반도체 레이저의 특성을 알아보고 광통신에의 응용을 검토하였다. 먼저 반도체 레이저의 동작 원리를 설명하였고, 초고속 반도체 레이저의 소신호 및 대신호 변조특성에 대해서 기술하였다. 또한, 반도체 레이저를 이용하여 극초단 펄스를 생성하는 방법으로 이득/Q 스위칭법, 외부변조기와 집적화된 반도체 레이저를 이용하는 방법, 모드 록킹법에 대해서 검토하고 펄스 압축법에 관해서도 기술하였다. 초고속 반도체 레이저의 응용으로는 초고속 광통신, 솔리톤 광통신, 전광 시분할 다중/역다중에 관해서 기술하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.1
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• pp.147-154
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• 2018

In this paper, we propose methods to acquire enemy object information, which is frequently required in multi-resolution model based war game and affects the simulation performance. In the information request method, a multi-resolution model selects information of a specific resolution and provides them to external objects. In the information announcement method, a multi-resolution model announces all information, and external objects select information of a specific resolution. In the information sharing method, external objects obtains information of a specific resolution by inquiring all information of a multi-resolution model which are stored in a shared space. Simulation results show that the information sharing method is more efficient than the information request method and the information announcement method because the information acquisition is fast. In addition, the proposed methods will increase the efficiency of war game operation by shortening the time for acquiring enemy forces' information.

• Proceedings of the Korea Inteligent Information System Society Conference
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• 2002.11a
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• pp.399-408
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• 2002

다중 에이전트 학습이란 다중 에이전트 환경에서 에이전트간의 조정을 위한 행동전략을 학습하는 것을 말한다. 본 논문에서는 에이전트간의 통신이 불가능한 다중 에이전트 환경에서 각 에이전트들이 서로 독립적으로 대표적인 강화학습법인 Q학습을 전개함으로써 서로 효과적으로 협조할 수 있는 행동전략을 학습하려고 한다. 하지만 단일 에이전트 경우에 비해 보다 큰 상태-행동 공간을 갖는 다중 에이전트환경에서는 강화학습을 통해 효과적으로 최적의 행동 전략에 도달하기 어렵다는 문제점이 있다. 이 문제에 대한 기존의 접근방법은 크게 모듈화 방법과 일반화 방법이 제안되었으나 모두 나름의 제한을 가지고 있다. 본 논문에서는 대표적인 다중 에이전트 학습 문제의 예로서 먹이와 사냥꾼 문제(Prey and Hunters Problem)를 소개하고 이 문제영역을 통해 이와 같은 강화학습의 문제점을 살펴보고, 해결책으로 신경망 SOM을 이용한 일반화 방법인 QSOM 학습법을 제안한다. 이 방법은 기존의 일반화 방법과는 달리 군집화 기능을 제공하는 신경망 SOM을 이용함으로써 명확한 다수의 훈련 예가 없어도 효과적으로 이전에 경험하지 못했던 상태-행동들에 대한 Q값을 예측하고 이용할 수 있다는 장점이 있다. 또한 본 논문에서는 실험을 통해 QSOM 학습법의 일반화 효과와 성능을 평가하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.445-447
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• 2008

본 연구에서는 다중벽 탄소나노튜브용 표면개질제를 리빙라디칼중합법을 통하여 제조하고, 이를 이용하여 표면개질되고 분산제어된 다중벽탄소나노튜브를 제조하고 염료감응형 태양전지의 대전극 재료로 사용하였다. 우선 리빙라디칼중합법 중 nitroxide mediated polymerization (NMP) 기술을 이용하여 poly(maleic anhydride-co-p-acetoxystyrene)-block-poly(p-acetoxystyrene)를 합성하고, 공중합체중의 maleic anhydride기에 이미드화 반응을 통하여 pyrene기를 도입하였다. 공중합체 중의 p-acetoxystyrene 반복단위들은 가수분해 반응을 통하여 p-hydroxystyrene 반복단위로 변환하였으며, 제조된 공중합체의 구조와 열 특성 등을 GPC, GC, $^1H$-NMR, TGA을 통하여 분석하였다. 제조된 공중합체를 이용하여 다중벽 탄소나노튜브의 표면을 polymer wrapping법으로 처리하였고, 표면개질된 탄소나노튜브의 분산성을 다양한 용매에서 비교분석하였다. 표면이 개질되고 페이스트 내에의 분산성이 향상된 다중벽탄소나노튜브를 염료감응태양전지의 대전극 제조에 응용하였으며, 표면처리 및 분산제어 여부에 따른 제작 특성 및 동작특성 등을 평가하였다.

• Journal of KIISE:Computer Systems and Theory
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• v.33 no.5
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• pp.297-305
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• 2006

Trace-driven simulation is widely used for measuring the performance of a microprocessor in its initial design phase. However, since it requires much time and disk space, the statistical simulation has been studied as an alternative method. In this paper, statistical simulations are performed for a high performance superscalar microprocessor with a perceptron-based multiple branch predictor. For the verification, various hardware configurations are simulated using SPEC2000 benchmarks programs as input. As a result, we show that the statistical simulation is quite accurate and time saving for the evaluation of microprocessor architectures with multiple branch prediction.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.3
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• pp.141-147
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• 2019

In this paper, a systematic beam splitter design for multi-beam forming is proposed. The objective of this research is to a design beam splitter that splits and focuses scattering microwaves into intense beams in multiple directions. It is difficult to split multi-beam to non-specific directions with theoretical approaches. Therefore, instead of using transformation optics(TO), which is a widely used process for controlling electromagnetic wave propagation, we used a systematic design process called the phase field design method to obtain an optimal topological structure of beam splitter. The objective function is to maximize the norm of electric field of the target areas of each direction. To avoid island structure and obtain the structure in one body, volume constraint is added to the optimization problem by using augmented Lagrangian. Target frequency is set to X-band 10GHz. The optimal beam splitter performed well in multi-beam forming and the transported electric energy of target areas improved. A frequency dependency test was conducted in the X-band to determine effective frequency range.

• Korean Journal of Optics and Photonics
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• v.13 no.6
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• pp.479-485
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• 2002

We propose a vector analysis for designing multimode-interference power splitters, which can show an arbitrary splitting ratio. Power splitting is a fundamental characteristic in integrated optical circuits and its value would be multiplied for many applications if the splitting ratio could be selected freely. Since the vector analysis utilizes a graphical method based on the previously-reported mathematical results of multimode interference, it shows an excellent advantage especially for designing power splitters with an arbitrary splitting ratio.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.47-52
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• 2011

In this paper, to evaluate the design properties of 3D optical multimode interference (MMI) couplers with ultracompact width, modal transmission line theory and effective dielectric method are combined with together. A coupling efficiency based on the composed approach is defined, and the coupling length is numerically determined for the design of 3 dB coupler, cross coupler and bar coupler. The simulation result shows that the designed MMI coupler has a low insertion loss and a high splitting ratio.