• 설비공학논문집
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• 제20권3호
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• pp.205-212
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• 2008

This paper describes the application of an inverse building model to a calibrated forward building model using EnergyPlus program. Typically, inverse models are trained using measured data. However, in this study, an inverse building model was trained using data generated by an EnergyPlus model for an actual office building. The EnergyPlus model was calibrated using field data for the building. A training data set for a month of July was generated from the EnergyPlus model to train the inverse model. Cooling load prediction of the trained inverse model was tested using another data set from the EnergyPlus model for a month of August. Predicted cooling loads showed good agreement with cooling loads from the EnergyPlus model with root-mean square errors of 4.11%. In addition, different control strategies with dynamic cooling setpoint variation were simulated using the inverse model. Peak cooling loads and daily cooling loads were compared for the dynamic simulation.

• 대한교통학회지
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• 제22권5호
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• pp.123-137
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• 2004

시간에 따라 변화하는 네트워크 상황을 반영하는 통행배분 연구가 활발히 진행되고 있다. 이러한 연구의 배경에는 통행배분 모델이 도로망 계획이라고 하는 하드웨어 분야의 계획에만 그치지 않고 교통관리나 제어라고 하는 소프트웨어 분야의 계획에도 활용하고자 하는 사회적 필요성의 증가 때문이다. 또한, 통행배분 모형의 이론과 현실 사이의 괴리를 줄이고자 하는 차원에서 연구되고 있는 모형으로 다중계층 통행배분 모형이 있다. 이 모형은 다중 운전자 계층과 다차종 계층으로 구분되며 이중에서 동적모형과 결합될 수 있는 보다 현실성 있는 분야는 다차종 분야이다. 이러한 배경에서 본 연구의 목적은 이 두 분야를 결합한 다차종 동적 통행배분 모형을 구축하고자 한다. 이것은 동적 이용자 균형 배분 모형이 현재 이슈화 되고 있는 첨단교통체계(ITS)의 이론적 지주가 되고 있으며 따라서 이러한 동적모형을 다중계층 모형과 결합시킴으로써 보다 현실성 있는 동적 모형이 구축될 수 있을 것으로 기대되기 때문이다. 그렇지만 다수의 차종을 고려하게 되는 경우 기존의 동적 배분 모형의 구축을 위하여 필요한 FIFO가 위반된다. 이것은 FIFO 제약 조건하에 구축되는 기존의 동적 배분 모델링 방법으로는 다차종 동적모형의 구축이 불가능함을 의미한다. 따라서 본 연구에서는 FIFO 제약조건을 완화 시킬 수 있는 동적 네트워크의 모형을 구축하였으며 동시에 기존의 네트워크 부화 기법의 하나인 시뮬래이션 기법을 수정하여 본 연구의 모형에 적용될 수 있도록 고안하였다. 또한 해법(알고리즘) 분야오 기존의 최단경로 산정 알고리즘을 수정한 시간종속적인 최단경로 알고리즘과, 기존의 MSA를 수정한 알고리즘도 구축하였다. 이렇게 구축된 모형과 알고리즘을 격자형 격자형 네트워크에 적용하여 동적이용자 균형해를 산정하여 구축된 알고리즘의 수렴성을 검증하였다.

• 한국철도학회논문집
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• 제14권1호
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• pp.11-18
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• 2011

본 논문은 열차의 타고오름 해석을 위한 새로운 2차원 다물체 동역학 모델링 방법을 제안하였다. 본 동역학 모델은 에너지 흡수구조/부품뿐만 아니라 차체의 변형도 고려하여 비선형 스프링, 댐퍼, 질량으로 구성되며 철도차량의 충돌에너지흡수량, 승객구간의 가속도, 연결 장치의 충격력, 차량간 타고오름 변위 등을 잘 예측할 수 있다. 제안된 방법으로 한국형고속열차를 차체 각 부분의 압괴 특성을 구하고 2차원 다물체 충돌동역학 모델을 구성하였다. 열차 대 열차 충돌 시나리오조건으로 2차원 동역학 모델을 시뮬레이션하고 3차원 가상시험 모델로 평가하였다. 그 결과 2차원 동역학 모델은 타고오름 거동을 잘 예측하였으며 차체변형을 고려한 모델링 기법이 타고오름 평가에 중요함을 확인하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권2호
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• pp.227-243
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• 2015

In this paper, the effects of nonlinear soft clay on dynamic embedment of offshore pipeline were investigated. Seabed embedment by pipe-soil interactions has impacts on the structural boundary conditions for various subsea structures such as pipeline, riser, pile, and many other systems. A number of studies have been performed to estimate real soil behavior, but their estimation of seabed embedment has not been fully identified and there are still many uncertainties. In this regards, comparison of embedment between field survey and existing empirical models has been performed to identify uncertainties and investigate the effect of nonlinear soil parameter on dynamic embedment. From the comparison, it is found that the dynamic embedment with installation effects based on nonlinear soil model have an influence on seabed embedment. Therefore, the pipe embedment under dynamic condition by nonlinear parameters of soil models was investigated by Dynamic Embedment Factor (DEF) concept, which is defined as the ratio of the dynamic and static embedment of pipeline, in order to overcome the gap between field embedment and currently used empirical and numerical formula. Although DEF through various researches is suggested, its range is too wide and it does not consider dynamic laying effect. It is difficult to find critical parameters that are affecting to the embedment result. Therefore, the study on dynamic embedment factor by soft clay parameters of nonlinear soil model was conducted and the sensitivity analyses about parameters of nonlinear soil model were performed as well. The tendency on dynamic embedment factor was found by conducting numerical analyses using OrcaFlex software. It is found that DEF was influenced by shear strength gradient than other factors. The obtained results will be useful to understand the pipe embedment on soft clay seabed for applying offshore pipeline designs such as on-bottom stability and free span analyses.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.353-356
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• 2005

We developed a dynamic model of PEM fuel cell system which can analyze its transient response to dynamic load current. System components such as compressor, air cooler, humidifier, and stack were modeled based on their dynamic equations and performance maps by using Matlab Simulink platform. Through this simulation model, dynamic characteristics of fuel cell system including oxygen excess rat io, stack voltage, and system efficiency were shown. In addition to that, we briefly analyzed the humidity effect on cathode pressure and system efficiency, expecting that this model can be further used to optimize fuel cell system parameters just like operating pressure and temperature, humidity and oxygen excess ratio.

• 한국멀티미디어학회논문지
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• 제11권6호
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• pp.729-736
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• 2008

Using video synthesis to depict flowing water is useful in virtual reality, computer games, digital movies and scientific computing. This paper presents a novel algorithm for synthesizing dynamic water scenes through a sample video based on a dynamic texture model. In the paper, we treat the video sample as a 2-D texture image. In order to obtain textons, we analyze the video sample automatically based on dynamic texture model. Then, we utilize a linear dynamic system (LDS) to describe the characteristics of each texton. Using these textons, we synthesize a new video for dynamic flowing water which is prolonged and non-fuzzy in vision. Compared with other classical methods, our method was tested to demonstrate the effectiveness and efficiency with several video samples.

• Journal of Radiation Protection and Research
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• 제28권3호
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• pp.239-245
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• 2003

Every nuclear power plant measured concentrations of tritium in groundwater and surface water around the plants periodically. It was not easy to predict the tritium concentration only with these measurement data in case of various release scenarios. KAERI developed a new approach to find the relationship between the tritium release rate and tritium concentration in the environment. The approach was based upon a dynamic compartment model. In this paper the dynamic compartment model was modified to predict the tritium behavior more accurately. The mechanisms considered for the transfer of tritium between the compartments were evaporation, groundwater flow, infiltration, runoff, and hydrodynamic dispersion. Time dependent source terms of the compartment model were introduced to refine the release scenarios. Also, transfer coefficients between the compartments were obtained using realistic geographical data. In order to illustrate the model various release scenarios were developed, and the change of tritium concentration in groundwater and surface water around the nuclear power plants was estimated.

• 대한교통학회지
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• 제27권6호
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• pp.129-137
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• 2009

첨단교통체계의 기술발전과 교통 분석의 수준이 상세해짐에 따라 동적 교통 분석에 대한 필요성이 증가하고 있다. 기존의 정적인 분석이 하루 평균 개념의 통행특성과 네트워크 상태를 묘사한 반면, 동적 분석에서는 시간흐름에 따른 네트워크의 상태를 분석한다. 본 논문에서는 교통시스템 동적 분석의 필요성을 인식하여, 고속도로망을 대상으로 FTMS 자료를 활용한 분석 방법론을 개발하였다. 개별 차량의 실제 통행기록 자료인 TCS 자료를 이용하여 전국 고속도로망을 대상으로 동적 기종점 통행량을 구축하였으며, 시뮬레이션 연산시간 문제 해결을 위해 분석범위를 설정한 Subarea 분석을 활용하였다. 이를 위해 전국 고속도로망을 대상으로 구축된 시간대별 기종점 통행량을 Subarea 기종점 통행량으로 전환하기 위한 방법론을 개발하였다. 구축된 모형의 적용을 위해 시나리오 분석을 실시하였으며, 이를 통해 각각의 시나리오에 대하여 기존의 단편적인 효과분석과 달리 하루 중 시간대별 교통여건에 따른 네트워크 상태분석을 수행하였다. 본 연구는 동적 교통 분석의 초기 시도라는 점과 실제 기종점 자료인 FTMS 자료를 활용한 분석이라는 점에서 의미를 가지며, 현재 교통 분석의 큰 흐름인 동적 교통 분석의 필요성을 부각시키고자 한다. 향후 고속도로뿐만이 아닌 기타 도로를 포함한 모형 구축이 필요하며, Hybrid 모형 및 프로그램 개발을 통해 궁극적인 목표인 실시간동적 분석 모형 개발을 위한 연산시간 문제 해결이 필요할 것이다.

• Journal of Welding and Joining
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• 제19권4호
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• pp.399-405
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• 2001

A dynamic force balance model is proposed in this work as an extension of the previous static force balance model to predict metal transfer in arc welding. Dynamics of a pendant drop is modeled as the second order system, which consists of the mass, spring and damper. The spring constant of a spherical drop at equilibrium is derived in the closed-form equation, and the inertia force caused by drop vibration is included in the drop detaching condition. While the inertia force is small in the low current range, it becomes larger than the gravitational force with current increase. The inertia force reaches half of the electromagnetic force at transition current, and has considerable effects on drop detachment. The proposed dynamic force balance model predicts the detaching drop size more accurately than the static force balance model.

• Steel and Composite Structures
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• 제51권6호
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• pp.697-712
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• 2024

In this paper, the dynamic flexural stiffness of concrete-filled steel tubular (CFST) members is investigated based on vibration modal testing and a Bayesian model updating procedure. To reflect the actual service states of CFST members, a 3-stage modal testing procedure is developed for 6 circular CFST beam-columns, in which the modal parameters of the specimens under varying axial load levels are extracted. In the model updating procedure, a Timoshenko beam element model is first established, in which the influence of shear deformation and rotational inertia are incorporated. Subsequently, a 2-round Bayesian model updating strategy is proposed to calculate the dynamic flexural stiffness of the specimens, which could effectively consider the influence of physical constraints in the updating process and achieve reasonably well results. Analysis of the updating results shows that with the increase of the axial load level, degradation of the flexural stiffness is significantly influenced by the load eccentricity. It shows that the cracking of the core concrete is the primary reason for the flexural stiffness degradation of CFST beam-columns. Finally, based on comparison with equations proposed by several design standards, the calculation methods for the dynamic flexural stiffness of CFST members is recommended.