• 자동차안전학회지
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• 제5권2호
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• pp.11-16
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• 2013

This paper presents a unified control algorithm of independent braking and steering for collision avoidance. The desired motion of the vehicle in the yaw plane is determined using the probabilistic risk assessment method based on target state estimation. For the purpose of coordinating the independent braking and steering, a non-linear vehicle model has been developed, which describes the vehicle dynamics in the yaw plane in both linear and extended non-linear ranges of handling. A control allocation algorithm determines the control inputs that minimize the difference between the desired and actual vehicle motions, while satisfying all actuator constraints. The performance of the proposed control algorithm has been investigated via computer simulations conducted using the vehicle dynamics software CARSIM and Matlab/Simulink.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제16권4호
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• pp.427-441
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• 2009

The method of Lattice Dynamical System is used to establish a global model on an infinite chain of many local markets interacting each other through a diffusion of prices between them. This global model extends the Walrasian evolutionary cobweb model in an independent single local market to the global market evolution. We assume that each local market has linear decreasing demands and quadratic supplies with naive predictors, and investigate the stationary behaviors of global price dynamics and show that their dynamics are conjugate to those of $H{\acute{e}}non$ maps and hence can exhibit complicated behaviors such as period-doubling bifurcations, chaos, and homoclic orbits etc.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제17권1호
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• pp.93-106
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• 2010

We employ the methods of Lattice Dynamical System to establish a global model extending the Walrasian evolutionary cobweb model in an independent single local market to the global market evolution over an infinite chain of many local markets with interaction of each other through a diffusion of prices between them. For brevity of the model, we assume linear decreasing demands and logistic supplies with naive predictors, and investigate the traveling wave behaviors of global price dynamics and show that their dynamics are conjugate to those of H$\acute{e}$non maps and hence can exhibit complicated behaviors such as period-doubling bifurcations, chaos, and homoclic orbits etc.

• Computers and Concrete
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• 제31권5호
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• pp.371-384
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• 2023

Precast roofing systems employing prestressed elements often serve as smart structural solutions for the construction of industrial buildings. The precast concrete elements usually employed are highly engineered, and often consist in thin-walled members, characterised by a complex behaviour in fire. The present study was carried out after a fire event damaged a precast industrial building made with prestressed beam and roof elements, and non-prestressed curved barrel vault elements interposed in between the spaced roof elements. As a consequence of the exposure to the fire, the main elements were found standing, although some locally damaged and distorted, and the local collapse of few curved barrel vault elements was observed in one edge row only. In order to understand and interpret the observed structural performance of the roof system under fire, a full fire safety engineering process was carried out according to the following steps: (a) realistic temperature-time curves acting on the structural elements were simulated through computational fluid dynamics, (b) temperature distribution within the concrete elements was obtained with non-linear thermal analysis in variable regime, (c) strength and deformation of the concrete elements were checked with non-linear thermal-mechanical analysis. The analysis of the results allowed to identify the causes of the local collapses occurred, attributable to the distortion caused by temperature to the elements causing loss of support in early fire stage rather than to the material strength reduction due to the progressive exposure of the elements to fire. Finally, practical hints are provided to avoid such a phenomenon to occur when designing similar structures.

• 대한기계학회논문집B
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• 제32권3호
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• pp.181-189
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• 2008

GaAs film growth process from trimethylgallium(TMGa) and tertiary-butylarsine(TBAs) using a horizontal MOCVD reactor was numerically studied to explain the experimental result that the decreasing surface reaction rate as the increasing partial pressure of group III species. Using the non-linear model based on the Langmuir isotherm which considers the adsorption and desorption of molecules, film deposition over the entire reactor scale was predicted by computational fluid dynamics (CFD) with the aid of the parameters obtained from the selective area growth (SAG) technique. CFD Results using the non-linear surface reaction model with the parameters determined from the SAG experiments predicted too high film growth rate compared to the measured values at the downstream region where the temperature was decreased abruptly. The pairs of ($k_s^n$, K) from the numerical simulations was $(2.52{\times}10K^{-6}mol/m^2/s,\;1.6{\times}10^5m^3/mol)$, whereas the experimentally determined was $(3.58{\times}10^{-5}mol/m^2/s,\;6.9{\times}10^5m^3/mol)$.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.468-471
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• 1997

In this paper, we investigate the time-sampling effects on the digital implementation of singular perturbation based STT autopilot with excellent performance and propose a compensation method for the time-sampling effects. In digitization of analog STT autopilot, it is found that the stability margin of the fast dynamics is mostly affected to lead to rapid decrease. Under the this analysis, a composite digital controller with additional compensator for fast dynamics is proposed to improve the time-sampling effect and a simulation verifies the result.

• 한국환경생물학회:학술대회논문집
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• 한국환경생물학회 2001년도 학술대회
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• pp.134-134
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• 2001

• 제어로봇시스템학회논문지
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• 제3권5호
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• pp.476-481
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• 1997

본 논문에서는 비구동 관절을 가지는 2링크 매니퓰레이터의 동력학 해석과 운동제어를 제1적분을 기초로 하여 전개하고 있다. 매니퓰레이터의 운동이 제1적분의 적분상수에 의해서 기술되는 것을 보이고, 제1적분을 이용하여 매니퓰레이터의 동력학을 해석하고 있다. 그리고 해석된 동력학을 적극적으로 이용하는 운동제어 알고리즘을 구성하고 시뮬레이션을 통하여 확인하고 있다. 끝으로 비구동 관절에 마찰이 작용하는 경우, 브레이크등의 보조수단을 이용하지 않고도 매니퓰레이터의 제어가 가능함을 보이고 있다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1999년도 춘계학술대회 논문집
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• pp.358-364
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• 1999

A wheel/rail contact module for dynamics analysis of railway vehicles is developed. The developed module is based on non-linear contact and FASTSIM algorithm which calculates contact forces. And the module is incorporated into the general purpose program DADS using user-defined subroutines. The simulation results of this developed program is compared to those of the railway vehicle dynamics analysis program AGEM. Since the module is based on DADS, various simulation environments can be considered.

• 경제분석
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• 제24권3호
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• pp.1-36
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• 2018

재고투자와 경기변동의 관계를 설명하는데 있어 생산평활(production smoothing) 가설과 재고소진 회피(stock-out avoidance) 가설은 서로 상반된 입장을 취하고 있다. 기업의 재고 투자에 관한 의사결정은 두 가지 동기 모두에 의해 영향받을 것으로 생각되지만 경기국면에 따라 각각의 영향력의 상대적 크기 혹은 방향성이 다르게 나타날 수 있다. 이에 본고는 재고투자 동학에서 생산평활 동기와 재고소진 회피동기의 상대적 유의성을 실증적으로 검증하되 경기국면별 비대칭성의 존재와 형태를 규명하는 데 분석의 초점을 둔 점에서 기존 연구와 차별성을 지닌다. 이를 위해 기존의 선형 재고투자 모형을 확장한 비선형 모형을 설정하였으며 이러한 방식이 기존 방식에 비해 우수한 지를 모형의 예측력을 비교 평가하여 확인하였다. 분석 결과, 재고투자 동학의 경기국면별 비대칭적 특성을 확인하였다. 경기 호황기에는 재고소진 회피동기가 나타나지만 생산평활 동기는 유의하지 않았다. 반대로 경기 불황기에는 재고소진 회피동기는 유의하지 않지만 Ramey (1991)에서 제시된 생산비용의 비볼록성에 의하여 재고변화가 경기침체를 심화시키는 경기 의존적 특성을 발견하였다. 경기국면별 비대칭성을 모형에 고려함으로써 그렇지 않은 모형에 비해 예측력을 향상시킬 수 있음을 표본 내 및 표본 외 예측, 다양한 예측력 검정을 통해 확인하였다. 본 연구의 결과는 재고투자의 동학과 경기 불안정화 특성에 대한 이해를 제고하여 경제전망 등에 활용될 수 있을 것으로 기대된다.