• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.5
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• pp.1076-1081
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• 2007

In this paper, we propose a new switch structure for time division duplex(TDD) system. The existing TDD structure utilizes a circulator fur isolation characteristic between ports. However, the circulator produces intermodulation distortion signals which are undesired signal because of its nonlinear properties. The proposed circuit is composed of a modified branch-line hybrid coupler which controls the signal flow while the isolated port is open-/short- terminated. In order to prove the validity of the presented structure, the switch circuit is fabricated and measured at 2.3GHz, the center frequency of Wibro service system.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.9
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• pp.851-856
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• 2011

In this paper, the fuzzy output-feedback controller is addressed for a discrete-time nonlinear interconnected systems with common input. The nonlinear interconnected system is represented by a T-S (Takagi-Sugeno) fuzzy model. Based on T-S fuzzy interconnected system, the fuzzy output-feedback controller is designed with common input. The stability condition of the closed-loop system is represented to the LMI (Linear Matrix Inequality) form. PEMFC model is given to show the verification of the controller discussed throughout the paper.

• Water for future
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• v.25 no.3
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• pp.105-113
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• 1992

The purpose of this paper is to introduce and to apply the artificial neural network theory to real hydrologic system for forecasting daily streamflows during flood periods. The hydrologic dynamic process of rainfall-runoff is identified by the iterated estimation of system parameters that are determined by adjusting the weights of the network according to the non-linear response characteristics which is formed the model. Back propagation algorithm of neural network model is applied for the estimation of system parameters with past daily rainfall and runoff series data, and streamflows are forecasted using the parameters. The forecasted results are analyzed by statistical methods for the comparison with the observed.

• ETRI Journal
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• v.5 no.3
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• pp.3-8
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• 1983

In the area of computer network planning, a location-allocation-size problem is involved. Since multi-facility location-allocation-size problems are very complex in formulating a mathematical model, it is a usual practise to adopt alternative approaches, which give no optimal results, instead of the optimal solution by mathematical approach. In this article, however, an attempt is made to formulate a mathematical model for the decision making problem of computer network design.

• Journal of the Korea Computer Industry Society
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• v.7 no.1
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• pp.39-46
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• 2006

Multipath diversity reception is applied to the compensation of the distortion of channel, which occurs in transmission of data at rapid speed. DS/BPSK systems are composed of the equipment with reception structure combined with a compensation algorithm to diversity branch. The efficiency of the system is evaluated from the point of view of average bit error rate according to SNR. In order to remove intersymbol interference, this algorithm is applied to time-invariant channel at every diversity branch with the number of L. As a result, the average bit error rate is saturated by $10^{-2}$ at the conventional compensation algorithm.

• Journal of Aerospace System Engineering
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• v.17 no.1
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• pp.24-32
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• 2023

This paper studied HART II in descending flight using rotorcraft analysis code based on geometrically exact beam (GEB) model. The present GEB model expressed by a mixed variational formulation could capture the geometrically nonlinear behavior of the blade without arbitrary assumptions. In previous results, correlation of airloads with structural moments for HART II was not as good as blade deflections. However, in present results, predictions of airloads and structural loads are fairly correlated with measured data.

• Annual Conference of KIPS
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• 2023.11a
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• pp.8-10
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• 2023

본 연구는 계층적 리스크 패리티 (Hierarchical Risk Parity, HRP) 포트폴리오 방법론과 정규화된 상호 정보 거리의 결합을 연구하였다. 이때, 한정된 이동창에서 발생할 수 있는 유한 크기 효과(finite size effects) 문제를 극복하기 위해 무작위로 섞인 NID 값에 대한 평균치를 제공함에 따라 NID 를 활용한 새로운 포트폴리오 최적화 방법을 제안한다. 본 연구의 결과는 NID 를 통합한 HRP 포트폴리오가 기존 방법론에 비해 통계적 장점과 함께 더욱 효율적이며 안정적임을 보여준다.

• The Journal of the Acoustical Society of Korea
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• v.38 no.5
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• pp.522-533
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• 2019

The compressive sensing model for range-Doppler estimation can be expressed as an under-determined linear system y = Ax. To find the solution of the linear system with the compressive sensing method, matrix A should be sufficiently incoherent and x to be sparse. In this paper, we propose a transmission waveform design method that maintains the bandwidth required by the sonar system while lowering the mutual coherence of the matrix A so that the matrix A is incoherent. The proposed method combines two methods of optimizing the sensing matrix with the alternating projection and suppressing unwanted frequency bands using the DFT (Discrete Fourier Transform) matrix. We compare range-Doppler estimation performance of existing waveform LFM(Linear Frequency Modulated) and designed waveform using the matched filter and the compressive sensing method. Simulation shows that the designed transmission waveform has better detection performance than the existing waveform LFM.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.3
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• pp.237-245
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• 2008

We developed a computational method on coupled dynamics of tracked vehicle on seafloor and long flexible pipe. The tracked vehicle is modeled as rigid-body vehicle, and the linked flexible pipe is discretized according to a lumped-parameter model. The equations of motion of the rigid-body vehicle on the soft seafloor are combined with the governing equations of flexible pipe dynamics. Four Euler parameters method is used to express the orientations of the vehicle and the flexible pipe. In order to solve the nonlinear coupled dynamics of vehicle and flexible pipe an incremental-iterative formulation is implemented. For the time-domain integration $Newmark-\beta$ method is adopted. The total Jacobean matrix has been derived based on the incremental-iterative formulation. The interactions between the dynamics of flexible pipe and the mobility of the tracked vehicle on soft seafloor are investigated through numerical simulations in time domain.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.68-77
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• 2017

High-frequency combustion instability results from a feedback coupling between the unsteady heat release rate and the acoustic waves formed resonantly in the combustion chamber. It can be modeled as thermoacoustic problems with various degrees of the assumptions and simplifications. This paper presents numerical analysis of self-excited combustion instabilities in a variable-length lean-premixed combustor and designs of passive control devices such as baffle and acoustic resonators in a framework of 3-D FEM Helmholtz solver. Nonlinear behaviors such as steep-fronted shock waves and a finite amplitude limit cycle are also investigated with a compressible flow simulation technique.