• Structural Engineering and Mechanics
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• 제12권3호
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• pp.267-281
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• 2001

Transient and quasi-steady-state vertical vibrations of a multi-span beam steel bridge located on a single-track railway line are considered, induced by a superfast passenger train, moving at speed 120-360 km/h. Matrix dynamic equations of motion of a simplified model of the system are formulated partly in the implicit form. A recurrent-iterative algorithm for solving these equations is presented. Excessive vibrations of the system in the resonant zones are reduced effectively with passive dynamic absorbers, tuned to the first mode of a single bridge span. The dynamic analysis has been performed for a series of types of bridges with span lengths of 10 to 30 m, and with parameters closed to multi-span beam railway bridges erected in the second half of the $20^{th}$ century.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1722-1724
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• 2005

The focus of this paper is to develop a mathematical model for investigating the dynamic performance of a polymer electrolyte membrane fuel cell. The model in this work is based on physical laws having clear significance in replicating the fuel cell system and can easily be used to set up different operational strategies. Simulation results display the transient behavior of the voltage within each single cell, and also within a number of such single cells combined into a fuel cell stack system. A linear as well as a nonlinear analysis of the polymer electrolyte membrane fuel cell system(PEMFC) has been discussed in order to present a complete and comprehensive view of this kind of modeling. Also, a comparison of the two kinds of analysis has been performed. Finally, the various characteristics of the fuel cell system are plotted in order to help us understand its dynamic behavior. Results indicate that there is a considerable amount of error in the modeling process if we use a linear model of the fuel cell. Thus, the nonlinearities present in the fuel cell system should be taken into account in order to obtain a better understanding of the dynamic behavior of the fuel cell system.

• 한국지반공학회논문집
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• 제18권1호
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• pp.127-132
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• 2002

사질토 지반에 근입된 모형말뚝에 대한 진동대 실험을 수행하여 말뚝지반 동적 상호작용 현상을 분석하고 동적군말뚝 효과를 산정하였다. 실험은 단말뚝과 말뚝간격을 말뚝직경의 3~8배로 변화시킨 $3\times3$ 군말뚝에 대하여 수행하였다. 동적 군맡뚝 효과는 단말뚝과 군말뚝의 동적 p-y곡선의 중심 기울기를 비교하여 산정하였고, 실험에서 얻어진 p-y곡선은 API의 반복 p-y곡선과 비교하였다. 실험결과 말뚝 간격, 입력 지진파의 주파수와 진폭 변화에 따른 동적 군말뚝 효과를 산정할 수 있었다.

• Structural Engineering and Mechanics
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• 제48권1호
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• pp.57-75
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• 2013

It is still inadequate for investigating the highly nonlinear and complex mechanical behaviors of single-layer latticed domes by only performing a force-based demand-capacity analysis. The energy-based balance method has been largely accepted for assessing the seismic performance of a structure in recent years. The various factors, such as span-to-rise ratio, joint rigidity and damping model, have a remarkable effect on the load-carrying capacity of a single-layer latticed dome. Therefore, it is necessary to determine the maximum load-carrying capacity of a dome under extreme loading conditions. In this paper, a mechanical model for members of the semi-rigidly jointed single-layer latticed domes, which combines fiber section model with semi-rigid connections, is proposed. The static load-carrying capacity and seismic performance on the single-layer latticed domes are evaluated by means of the mechanical model. In these analyses, different geometric parameters, joint rigidities and roof loads are discussed. The buckling behaviors of members and damage distribution of the structure are presented in detail. The sensitivity of dynamic demand parameters of the structures subjected to strong earthquakes to the damping is analyzed. The results are helpful to have a better understanding of the seismic performance of the single-layer latticed domes.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제24회 KOSCO SYMPOSIUM 논문집
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• pp.68-75
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• 2002

The dynamic behaviors of the single vortex and flame-vortex interaction in a $CH_4/Air$ diffusion flame with addition of $CO_2$ were investigated numerically. The numerical method was based on a predictor-corrector for low Mach number flow. A two-step global reaction mechanism was adopted as a combustion model. Through comparison of results by effect of $CO_2$ added either on the fuel or oxidizer side, it was found that the growth of single vortex and entrainment of surrounding fluid by $CO_2$addition on the fuel side are larger than those by $CO_2$ addition on oxidizer side. Also, when $CO_2$ is added on fuel side, flame-vortex interaction becomes more significant than on air side.

• Earthquakes and Structures
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• 제7권4호
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• pp.511-525
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• 2014

The main object of this study is to determine and compare the structural behavior of base isolated long span highway bridge, $G\ddot{u}lburnu$ Highway Bridge, using single concave friction pendulum (SCFP) and triple concave friction pendulum (TCFP). The bridge is seismically isolated in the design phase to increase the main period and reduce the horizontal forces with moments using SCFP bearings. In the content of the paper, firstly three dimensional finite element model (FEM) of the bridge is constituted using project drawings by SAP2000 software. The dynamic characteristics such as natural frequencies and periods, and the structural response such as displacements, axial forces, shear forces and torsional moments are attained from the modal and dynamic analyses. After, FEM of the bridge is updated using TCFP and the analyses are performed. At the end of the study, the dynamic characteristics and internal forces are compared with each other to extract the TCFP effect. To emphasize the base isolation effect, the non-isolated structural analysis results are added to graphics. The predominant frequencies of bridge non-isolated, isolated with SCFP and isolated with TCFP conditions decreased from 0.849Hz to 0.497Hz and 0.338Hz, respectively. The maximum vertical displacements are obtained as 57cm, 54cm and 44cm for non-isolated, isolated with SCFP and isolated with TCFP conditions, respectively. The maximum vertical displacement reduction between isolated with TCFP bearing and isolated with SCFP bearing bridge is %23. Maximum axial forces are obtained as 60619kN, 18728kN and 7382kN, maximum shear forces are obtained as 23408kN, 17913kN and 16249kN and maximum torsional moments are obtained as 24020kNm, 7619kNm and 3840kNm for non-isolated, isolated with SCFP and isolated with TCFP conditions, respectively.

• 한국정밀공학회지
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• 제11권5호
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• pp.189-198
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• 1994

The achievable machining accuracy depends upon the level of the micro-engineering, and the today's accuracy targets are dimensional tolerances in the order of 10nm and surface roughness in the order of 1nm. Such requirements cannot be satisfied by the conventional machining processes. Single point diamond turning is the one of new techniques which can produce the parts with such accuracy limits. The aims of this thesis are to get a better understanding of the complex cutting process with a diamond tool and, consequently, to develope a predicting model of a turned surface profile. In order to predict the turned surface profile, a numerical model has been developed. By means of this model, the influence of the operational settings-the material properties of the workpiece, the geometry of the cutting tool and the dynamic behaviour of the lathe-and their influences via the cutting forces upon the surface roughness have been estimated.

• 대한교통학회지
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• 제11권1호
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• pp.67-86
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• 1993

A formulation of dynamic traffic assignment between multiple origins and single destination was first introduced in 1987 by Merchant and Nemhauser, and then expanded for multiple destination in the late 1980's (Carey, 1987). Based on behavioral choice theory which provides proper demand elasticities with respect to changes in policy variables, traffic phenomena can be analysed more realistically, especially in peak periods. However, algorithms for these models are not well developed so far(working with only small toy network) and solutions of these models are not unique. In this paper, a new model is developed which keeps the simplicity of static models, but provides the sensitivity of dynamic models with changes of O-D flows over time. It can be viewed as a joint departure time and route choice model, in the given time periods(6-7, 7-8, 8-9 and 9-10 am). Standard multinomial logit model has been used for simulating the choice behavior of destination, mode, route and departure time within a framework of the incremental network assignment model. The model developed is workable in a PC 386 with 175 traffic zones and 3581 links of Seoul and tested for evaluating the exclusive use of Namsan tunnel for HOV and the left-turn prohibition. Model's performance results and their statistical significance are also presented.

• Korean Chemical Engineering Research
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• 제61권1호
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• pp.89-96
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• 2023

동적 선형 블록과 정적 비선형 블록이 직렬로 연결되어 있는 Wiener형 비선형 모델은 여러 화학 공정의 동특성을 묘사하는데 널리 사용되는데, Wiener형 비선형 공정의 모델 확인은 다소 긴 공정 활성화 데이터가 필요하다. 본 연구는 이러한 단점을 보완하기 위하여 단일 계단 응답으로부터 Wiener형 비선형 공정 모델을 찾아낼 수 있는 새로운 모델 확인 방법을 제안한다. 제안된 방법은 계단 응답의 초기 응답으로부터 선형 동적 블록의 예측 응답을 얻어 선형 동적 블록의 모델을 확인하고, 이어서 비선형 정적 블록의 모델을 확인한다. 본 방법은 단일 계단 응답만을 사용하여 공정 모델 확인을 위해 필요한 공정 응답을 얻는 과정에서 시간과 비용적으로 큰 이득을 얻을 수 있다. 제안된 공정 확인 방법의 성능은 대표적인 Wiener형 비선형 공정인 pH 적정 공정과 액위 공정을 대상으로 검증되었다.

• 대한핵의학회지
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• 제29권1호
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• pp.48-53
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• 1995

Rb-82 dynamic PET과 이중적분법에 의한 국소 심근 혈류측정 연구를 시행하고자 실험 개를 이용한 심근 혈전증 모델에서 좌심실 입력함수에 의한 정상 및 관류결손 심근에서의 혈류를 측정하였다. 이중적분법이 선형회귀모델에 의한 혈류측정방법에 비하여 실현이 간단하고 심근내 혈류가 선형적인 가정을 배제할 수 있어 더욱 정확한 방법이 될 수 있음을 확인하였다.