• 대한토목학회논문집
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• 제28권6D호
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• pp.801-807
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• 2008

본 연구는 시간-면적 방법론을 적용하여 도시교통수단의 토지소모 효율성을 비교분석하고자 하였다. 도시의 주요 교통수단을 대상으로 그간의 연구와 달리 각 수단에 적합한 교통조건과 운행여건을 고려한 토지소모효율성 산정식을 도출하였고, 도출된 식을 이용하여 각 수단별 1km 통행시의 인당 시간-면적 소모량을 계산하여 비교하였다. 또한 산정식을 이용하여 소모량과 운행속도와의 관계를 분석하여 각 수단의 소모량의 범위를 비교하였으며, 주차에 의한 시간-면적 소모량을 명확히 제시하기 위해 외곽으로부터 도심으로 통행하는 통근자의 가상 왕복통행을 가정하여 수단별 통행에 따른 총 시간-면적소모량을 비교분석하였다. 연구의 결과, 이용시설에 상관없이 승용차 이용자가 가장 소모량이 많은 것으로 나타났고, 도시철도를 포함한 대중교통수단의 효율성이 우수한 것으로 나타났다. 예상과는 달리 도보와 자전거는 높은 소모량을 보였다. 그럼에도 불구하고 단거리 통행시 버스를 대체할 수 있는 수단으로 나타났다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.318-322
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• 1996

This paper presents a technique to control a robot which has a flexible manipulator moving in a vertical plane. The flexible manipulator is modeled as an Euler-Bernoulli beam. Elastic deformation is represented using the assumed modes method. A comparison function which satisfies all geometric and natural boundary conditions of a cantilever beam with an end mass is used as an assumed mode shape. Lagrange's equation is utilized for the development of a discretized model. A control algorithm is developed using a simple PID control technique. The proportional, integral and derivative control gains are determined based on the dominant pole placement method and tuned to show no overshoot and having a short settling time. The effectiveness of the developed control scheme is showed experimentally. In the position control experiment, three different end masses are used. The experimental results shows little overshoot, no steady state error, and less than 2.5 second settling time in case of having an end mass which is equivalent to 45% of the total system weight. Also the residual vibration of the end point is effectively controlled.

• 소음진동
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• 제10권2호
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• pp.361-366
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• 2000

In this paper, a new finite annular plate element is developed, which considers the effects of the slight deviation from a perfect axisymmetry. It is assumed that, when a local deviation is introduced to an axisymmetric plate, the natural modes are separated into the symmetric and asymmetric modes. The proposed method is very efficient because a few elements are demanded and lots of active degrees of freedom are reduced in comparison with commercial numerical analysis programs. In addition, when the deviation is small enough. It is more accurate than the result of using usual plate elements of commercial FEM programs.

• Journal of Welding and Joining
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• 제20권1호
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• pp.83-90
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• 2002

Metal Transfer in gas metal arc (GMA) welding is a complex phenomenon affected by many parameters of the welding conditions and material properties. In this research, the correlation equation between the welding condition and detaching droplet size and detaching velocity in GMA welding was studied via recession analysis on the results of numerical analysis using the volume-of-fluid (VOF) method. Welding parameters and material properties were grouped into three dimensionless numbers and detaching droplet size was expressed as the function of them. Second order and exponential multi-variable correlation forms were assumed, and the coefficients of these equations were calculated for globular and spray modes as well as entire transfer modes. Applying correlation equation into available experimental data, it shows good agreement.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권4호
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• pp.763-774
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• 2014

A simple and efficient vibration analysis procedure for stiffened panels with openings and arbitrary boundary conditions based on the assumed mode method is presented. Natural frequencies and modes are determined by solving an eigenvalue problem of a multi-degree-of-freedom system matrix equation derived by using Lagrange's equations of motion, where Mindlin theory is applied for plate and Timoshenko beam theory for stiffeners. The effect of stiffeners on vibration response is taken into account by adding their strain and kinetic energies to the corresponding plate energies whereas the strain and kinetic energies of openings are subtracted from the plate energies. Different stiffened panels with various opening shapes and dispositions for several combinations of boundary conditions are analyzed and the results show good agreement with those obtained by the finite element analysis. Hence, the proposed procedure is especially appropriate for use in the preliminary design stage of stiffened panels with openings.

• Structural Engineering and Mechanics
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• 제71권4호
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• pp.445-458
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• 2019

This study mainly aims to assess the performance of soil-structure systems designed by direct displacement-based method coupled with strong column-weak beam design concept through various system identification techniques under strong ground motions. To this end, various system identification methods are employed to evaluate the dynamic characteristics of a structure (i.e., modal frequency, system damping, mode shapes, and plastic hinge formation pattern) under a strong seismic excitation considering soil-structure interaction for different site conditions as specified by ASCE 7-10. The scope of the study narrowed down to the code-complying low- to high-rise steel moment resisting frames with various heights (4, 8, 12, 16-story). The comparison of the result of soil-structure systems with fix-based support condition indicates that the modal frequencies of these systems are highly influenced by the structure heights, specifically for the softer soils. This trend is more significant for higher modes of the system which can considerably dominate the response of structures in which the higher modes have more contribution in dynamic response. Amongst all studied modes of the vibration, the damping ratio estimated for the first mode is relatively the closet to the initial assumed damping ratios. Moreover, it was found that fewer plastic hinges are developed in the structure of soil-structure systems with a softer soil which contradicts the general expectation of higher damageability of such structural systems.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.221-226
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• 2005

In this paper, a dynamic model for the rotor shaft-coupling-blade system is developed. The blades are attached to a disk and driven by an electric motor shaft which is flexible in torsion. We assumed that the shaft torsional flexibility is lumped in the flexible coupling which is usually adopted in rotor systems. The Lagrangian approach with the small deformation theory for both blade-bending and shaft-torsional deformations is employed for developing the equation of the motion. The assumed modes method is used for estimating the blade transverse deflection. The numerical results highlight the effects of both structural damping of the system and the torsional stiffness of the flexible coupling to the dynamic response of the blade. The results showed strong coupling between the blade bending and shaft torsional vibrations in the form of inertial nonlinearif, stiffness hardening and softening.

• 한국소음진동공학회논문집
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• 제15권9호
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• pp.1023-1029
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• 2005

In this paper, a dynamic model for the rotor shaft-coupling-blade system was developed. The blades are attached to a disk and driven by an electric motor shaft which is flexible in torsion. We assumed that the shaft torsional flexibility was lumped in the flexible coupling which is usually adopted in rotor systems. The Lagrangian approach with the small deformation theory for both blade-bending and shaft-torsional deformations was employed for developing the equation of the motion. The Assumed Modes Method was used for estimating the blade transverse deflection. The numerical results highlight the effects of both structural damping of the system and the torsional stiffness of the flexible coupling to the dynamic response of the blade. The results showed strong coupling between the blade bending and shaft torsional vibrations in the form of inertial nonlinearity, stiffness hardening and softening.

• 한국항행학회논문지
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• 제4권2호
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• pp.103-113
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• 2000

유연체 부착물을 갖는 인공위성의 수학적 모델링에 관한 방법은 몇 가지들이 있다. 본 논문에서는 FEM에 비해 차수가 낮아 계산시간을 줄일 수 있는 근사화 방법중 하나인 추측모드법을 사용한 하이브리드 라그랑지 방정식을 유도하였다. 이것들은 각속도에 관한 세개의 식들과 유연변위에 관한 두개의 식들로 이루어지며, 위성 본체와 태양전지판의 상호작용을 표현한다. 자세제어에 있어서, 제어법칙은 제어입력뿐만 아니라 진동억제를 포함한 성능지수를 최소화하도록 설계하였다. 이 목적을 위해 본 논문은 LQG와 LQG/LTR 제어기를 사용하였고, 결과로는 진동억제를 고려한 소각선회 성능을 보여준다. 특히, 본 논문에서는 특이시스템을 특이값 분리에 의한 비특이시스템 가정법을 통한 LQG/LTR 설계를 보여준다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.547-551
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• 1996

In this paper, robust vibration control of a one-link flexible robot arm based on variable structure system is discussed. We derive dynamic equations of it using a Lagrangian assumed modes method based on Bernoulli-Euler Beam theory. The optimal sliding surface is designed and the problem of chattering is also solved by the adoption of a continuous control law within a small neighborhood of the switching hyperplane.