• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2009년 춘계학술대회논문집
• /
• pp.75-80
• /
• 2009

The present paper focuses on the analysis of aero-acoustics characteristic by several boundary conditions. In this simulation, a high-order and high-resolution numerical schemes are used for the accurate computation of compressible flow with several boundary conditions including characteristic boundary conditions as well as extrapolation and zonal characteristic boundary condition. These boundary conditions are applied to the computation of two dimensional circular cylinder flows with Mach number of 0.3 and Reynolds number of 400. The computation results are validated with measurement datum and other computation results for the Strouhal frequency of vortex shedding, the mean drag coefficient and root-mean-square lift for the unsteady periodic flow regime. Secondary frequency is predicted by three kinds of boundary conditions characteristic.

• Industrial Engineering and Management Systems
• /
• 제10권2호
• /
• pp.170-177
• /
• 2011

We present an improved binomial method for pricing financial deriva-tives by using cell averages. After non-overlapping cells are introduced around each node in the binomial tree, the proposed method calculates cell averages of payoffs at expiry and then performs the backward valuation process. The price of the derivative and its hedging parameters such as Greeks on the valuation date are then computed using the compact scheme and Richardson extrapolation. The simulation results for European and American barrier options show that the pro-posed method gives much more accurate price and Greeks than other recent lattice methods with less computational effort.

• 한국멀티미디어학회:학술대회논문집
• /
• 한국멀티미디어학회 2000년도 춘계학술발표논문집
• /
• pp.449-452
• /
• 2000

This paper proposes a new, adaptive Dead Reckoning model, called Dynamic Dead Reckoning , for Distributed Interactive Simulation and humanoid avatar systems. The proposed model can overcome the weak points of traditional Dead Reckoning caused by a fixed threshold and strong dependency on rotation event. This paper introduces new criteria for update message filtering , named as Update lifetime. The Dynamic Dead Reckoning keeps the balance between extrapolation fidelity and filtering performance by two component models, Variable Threshold Mechanism and Rotation Event model. The experimental results show that the proposed model can lower the increment rate of update traffic to the increase of rotation frequency without any significant loss of accuracy.

• 전자공학회논문지A
• /
• 제30A권8호
• /
• pp.57-62
• /
• 1993

In this paper, both feasible power gain and power added efficiency at the operating center frequency of 12 GHz are stressed to design a power FET with double-heterjunction structure. The variable parameters or the design are the unit gate width, the gate length, the doping density of AlGaAs, the AlGaAs thickness, the spacer thickness, the Al mole fraction, and the GaAs well thickness. The results of simulation for the FET with 1.mu.m gate length show that the power gain and the power added efficiency are 10.2 dB and 36.3% at 12GHz, respectively. An extrapolation of the relation between current gain and unilateral gain yields a 17 GHz cutoff frequency and 43GHz maximum frequency of oscillation. The calculation of the current versus voltage characteristics show that the output power of the device is about 0.62W.

• 한국응용약물학회:학술대회논문집
• /
• 한국응용약물학회 1995년도 제3회 추계심포지움
• /
• pp.135-136
• /
• 1995

Resent advances in computer technology have introduced a sophisticated capability for computing the biological fate of toxicants in a biological system. This methodology, which has drastically altered risk assessment skill in toxicology, is designed using all the mechanistic information, and all claim better accuracy with extrapolating capability Iron animal to people than conventional pharmacokinetic methods. Biologically based mathematical models in which the specific mechanistic steps governing tissue disposition(pharmacokinetics) and toxic action (pharmacodynamics) of chemicals are constructed in quantitative terms by a set of equations loading to prediction of the outcome of specific toxicological experiments by computer simulation. pharmacokinetic and pharmacodynamic models are useful in risk assessment because their mechanistic biological basis permits the high-to-low dose, route to route and interspecies extrapolation of the tissue disposition and toxic action of chemicals.

• 전력전자학회논문지
• /
• 제26권3호
• /
• pp.159-166
• /
• 2021

This study compares the maximum power point tracking (MPPT) control methods of a thermoelectric generator on vehicles. The researchers conduct comparisons on five different MPPT methods, including a fractional open circuit voltage method, a perturbation and observation (P&O) method, an incremental conductance method, a linear extrapolation-based MPPT (LEMPPT) method, and a LEMPPT/P&O hybrid method. These five MPPT methods are theoretically analyzed in detail, and the comparisons are conducted through MATLAB/Simulink simulation results. The comparison outcomes reveal that linear MPPT methods, including LEMPPT and LEMPPT/P&O hybrid methods, are more suitable for a thermoelectric generator on vehicles than the other MPPT methods examined in this work.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
• /
• pp.346-351
• /
• 1998

In design of a digital current controller for a 3-phase (3 ) voltage-source (VS) PWM converter, its conventional model, i.e., stationary or synchronous reference frame model, is used in obtaining its discretized version. It introduces, however, inherent errors since the following practical problems are not taken into consideration: the characteristics of the space vector-based pulse-width modulation (SVPWM) and the time delays in the process of sampling and computation. In this paper, the new hybrid reference frame model of the 3 VS PWM converter is proposed considering these problems. In addition, the direct digital current controller based on this model is designed without any prediction or extrapolation algorithm to compensate the time delay. So the control algorithm is made very simple. It represents no steady-state error in input current control and has the optimized transient responses. The validity of the proposed algorithm is proved by the computer simulation and experimental results.

• Nuclear Engineering and Technology
• /
• 제56권3호
• /
• pp.916-921
• /
• 2024

The control rod worth sensitivity to the neutron detector position in the rod drop experiment is studied by the time-dependent Monte Carlo (TDMC) neutron transport calculations for AGN-201K educational reactor and the Kyoto University Critical Assembly. The TDMC simulations of the rod drop experiments are conducted by the Seoul National University Monte Carlo (MC) code, McCARD, yielding time-dependent neutron densities at detector positions. The detector-position-dependent results of the total control rod worth calculated by the extrapolation, the integral counting, and the inverse methods are compared with the numerical reference using the MC eigenvalue calculations and the experimental results. From these comparisons, it is observed that the total control rod worth can be estimated with a considerable difference depending on the detector position through the rod drop experiment. The proposed TDMC simulation of the rod drop experiment can be applied for searching a better detector position or quantifying a bias for the control rod worth measurement.

• 대한조선학회논문집
• /
• 제33권1호
• /
• pp.145-152
• /
• 1996

본 연구에서는 해상 구조물에 작용하는 설계 파랑 하중을 산정하기 위하여 해상에서 관측되거나 또는 예측된 파랑 자료를 사용하여 해상 구조물의 설계 생존 기간 동안 만나게 될 극한 설계파를 산정하는 기법을 개발하였다. 주어진 파랑 자료에 Order Statistics와 Monte Carlo Simulation 기법을 적용하여 가장 알맞은 파랑 자료의 극한 분포식을 선택하여 이 분포식으로부터 원하는 회귀 주기에 해당하는 극한 설계파를 결정하고 결정된 극한 설계 파고의 불확실성에 대한 범위를 설정함으로서 설계 파고의 여유를 줄 수 있다. 이와 같은 기법을 우리나라 남해안의 1938년부터 1987년까지 태풍에 의한 파랑 자료에 적용하여 극한 설계파를 산정하는 예를 보였다. 이상과 같은 방법을 이용함으로서 대형 해양 구조물을 설계함에 있어 극한 하중 상태를 산정할 수 있는 정보를 설계 초기 단계에 제공할 수 있으며 해당 구조물의 주요 요목, 구조 등의 설계 인자들을 산정할 수 있다.

• 한국항공우주학회지
• /
• 제41권1호
• /
• pp.10-16
• /
• 2013

본 논문에서는 풍동 실험을 통해 취득한 소음측정 결과에서 실제 비행에 기체에서 발생되는 소음을 예측하는 과정에 대하여 다루었으며 정지된 소음원을 비행하는 것과 같은 상태로 시뮬레이션 할 수 있는 방법에 대하여 소개하고 실험을 통하여 검증하였다. 또한 국제민간항공기구(이하 ICAO)에서 규정한 절차에 따라 틸트로터 항공기 및 무인항공기의 환경소음을 평가할 수 있는 방안을 제시하였다. 제시한 평가 방안을 검증하기 위해서 풍동실험과 비행시험에 대한 소음실험 시뮬레이션 프로그램을 구성하였으며 7kg급 무인항공기를 통한 풍동 실험 및 비행 실험을 수행하였으며 풍동 실험 결과로부터 비행 상태의 소음예측이 가능하다는 것을 확인 할 수 있었다.