• Nuclear Engineering and Technology
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• 제55권6호
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• pp.2112-2124
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• 2023

With the rise of economic and safety standards for nuclear reactors, new concepts of Gen-IV reactors and modular reactors showed more complex designs that challenge current tools for reactor physics analysis. A Monte Carlo (MC) two-step method was proposed in this work. This calculation scheme uses the continuous-energy MC method to generate multi-group cross-sections from heterogeneous models. The multi-group MC method, which can adapt locally-heterogeneous models, is used in the core calculation step. This calculation scheme is verified using a Gen-IV modular lead-based fast reactor (LFR) benchmark case. The influence of homogenized patterns, scatter approximations, flux separable approximation, and local heterogeneity in core calculation on simulation results are investigated. Results showed that the cross-sections generated using the 3D assembly model with a locally heterogeneous representation of control rods lead to an accurate estimation with less than 270 pcm bias in core reactivity, 0.5% bias in control rod worth, and 1.5% bias on power distribution. The study verified the applicability of multi-group cross-sections generated with the MC method for LFR analysis. The study also proved the feasibility of multi-group MC in core calculation with local heterogeneity, which saves 85% time compared to the continuous-energy MC.

• 제어로봇시스템학회논문지
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• 제12권6호
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• pp.547-553
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• 2006

This paper studies digital control of biodynamic model of HIV-1 via intelligent digital redesign (IDR). The purpose of the IDR is to develop an equivalent digital fuzzy controller maintaining the satisfactory performance of an existing continuous-time fuzzy controller in the sense of the state-matching. Some conditions for the stability as well as the global state-matching are provided.. They are given by the form of the linear matrix inequalities (LMIs) and thereby easily tractable by the convex optimization techniques. The main features of the proposed method are that 1) the generalized control scheme is provided for the multirate as well as the single-rate digital controllers; 2) a new compensated block-pulse function method is applied to closely match the states of the continuous-time and the sampled-data fuzzy systems in the discrete-time domain; 3) the two-step procedure of IDR is presented to prevent the performance degradation caused by the additional stability conditions. The applicability of the proposed approach is shown through the biodynamic model of HIV-1.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.617-627
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• 2021

Underwater Acoustic Channels (UAC) have inherent sparse characteristics. The traditional adaptive equalization techniques do not utilize this feature to improve the performance. In this paper we consider the Variable Adaptive Subgradient Projection (V-ASPM) method to derive a new sparse equalization algorithm based on the Minimum Symbol Error Rate (MSER) criterion. Compared with the original MSER algorithm, our proposed scheme adds sparse matrix to the iterative formula, which can assign independent step-sizes to the equalizer taps. How to obtain such proper sparse matrix is also analyzed. On this basis, the selection scheme of the sparse matrix is obtained by combining the variable step-sizes and equalizer sparsity measure. We call the new algorithm Sparse-Control Proportional-MSER (SC-PMSER) equalizer. Finally, the proposed SC-PMSER equalizer is embedded into a turbo receiver, which perform turbo decoding, Digital Phase-Locked Loop (DPLL), time-reversal receiving and multi-reception diversity. Simulation and real-field experimental results show that the proposed algorithm has better performance in convergence speed and Bit Error Rate (BER).

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년 학술대회 논문집 정보 및 제어부문
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• pp.327-329
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• 2006

A controller is proposed for the robust adaptive backstepping control of a class of uncertain nonlinear systems using nonlinear disturbance observer (NDO). The NDO is applied to estimate the time-varying lumped disturbance in each step, but a disturbance observer error does not converge to zero since the derivative of lumped disturbance is not zero. Then the fuzzy neural network (FNN) is presented to estimate the disturbance observer error such that the outputs of the system are proved to converge to a small neighborhood of the desired trajectory. The proposed control scheme guarantees that all the signals in the closed-loop are semiglobally uniformly ultimately bounded on the basis of the Lyapunov theorem. Simulation results are presented to illustrate the effectiveness and the applicability of the approaches proposed.

• Journal of information and communication convergence engineering
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• 제3권1호
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• pp.56-61
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• 2005

In this paper, we present a video rate control scheme for storage and delivery in which the time-varying viewing interests are controlled by human gaze. To track the gaze, the pupil's movement is detected using the three-step process : detecting face region, eye region, and pupil point. To control bit rates, the quantization parameter (QP) is changed by considering the static parameters, the video object priority derived from the pupil tracking, the target PSNR, and the weighted distortion value of the coder. As results, we achieved human interfaced visual model and corresponding region-of-interest rate control system.

• 설비공학논문집
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• 제14권11호
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• pp.914-922
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• 2002

Thermo-acoustic waves can be thermally generated in a compressible flow field by rapid heating and cooling, and chemical reaction near the boundary walls. This mechanism is very important in the space environment in which natural convection does not exist. Also this may be a significant factor for heat transfer when the fluids are close to the thermodynamic critical point. In this study, the generation and transmission characteristics of thermo-acoustic waves in an air-filled confined domain with two-step pulsed heating are studied numerically. The governing equations are discretized using control volume method, and are solved using PISO algorithm and second-order upwind scheme. For the purpose of stable solution, time step was set to the order of $1\times10_-9s,\;and\;grids\;are\;50\times2000$. Results show that temperature and pressure distributions of fluid near the boundary wall subjected to a rapid heating are increased abruptly, and the induced thermo-acoustic wave propagates through the fluid until it decays due to viscous and heat dissipation. Pressure waves have sharp front shape and decay with a long tail in the case of step heating, but these waves have sharp pin shape in the case of pulsed heating.

• 한국군사과학기술학회지
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• 제16권2호
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• pp.130-137
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• 2013

In this paper, decoupled controller design for Autonomous Underwater Vehicle(AUV) and its simulated performance test results and Hardware In the Loop Simulation(HILS) results are presented. Control system design is done using the PD control scheme. Stability analysis and step response of closed loop system under uncertain parameter condition are also presented. The results of full coupled nonlinear model simulation show the well applicability of the designed controller. From the results of HILS, we can verify performance of real time processing and implemented hardware for AUV.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.280-280
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• 2000

In this paper, we propose a method of constructing equation using bio-inspired emergent and evolutionary concepts. This method is algorithm that is based on the characteristics of the biological DNA and growth of plants. Here is. we propose a constructing method to make a DNA coding method for production rule of L-system. L-system is based on so-called the parallel rewriting mechanism. The DNA coding method has no limitation in expressing the production rule of L-system. Evolutionary algorithms motivated by Darwinian natural selection are population based searching methods and the high performance of which is highly dependent on the representation of solution space. In order to verify the effectiveness of our scheme, we apply it to one step ahead prediction of Mackey-Glass time series.

• Communications for Statistical Applications and Methods
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• 제19권3호
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• pp.395-403
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• 2012

Process adjustment, also called engineering process control(EPC), is applied to maintain process output close to a target value by manipulating controllable variables, but special causes may still make the process deviate from the target and result in significant costs. Thus, it is important to detect and mediate deviations as early as possible. We propose a one-step detection method, the moving search block(MSB), with which the time and type of a special cause can be identified in short periods. A modified control rule that can entertain the effects of the special cause is proposed. A numerical example is presented to evaluate the performance of the proposed scheme.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 A
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• pp.59-62
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• 2002

Before a developed digital Power System Stabilizer(PSS) is installed to real power system, an efficient trial test for installing PSS is needed. In this paper, the performance of developed digital PSS for a single hydro-turbine generator and infinite bus system has been investigated using Real Time Digital Simulator(RTDS) in order to install PSS to real power system practically. The test system was composed of RTDS, three phase voltage/current amplifier and the PSS and the test scheme provided a very efficient way to verify the design and control performance of a PSS to be applied to real power system. The trial installation test through AVR 3% step test and three fault analysis may be guaranteed to install PSS to real power system.