• Journal of Electrical Engineering and Technology
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• 제4권3호
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• pp.315-322
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• 2009

Penetration and installation of a new dynamic technology known as Flexible AC Transmission Systems (FACTS) in a practical and dynamic network requires and force expert engineer to develop robust and flexible strategy for planning and control. Unified Power Flow Controller (UPFC) is one of the recent and effective FACTS devices designed for multi control operation to enhance the power system security. This paper presents a dynamic strategy based on Particle Swarm Optimization (PSO) for optimal parameters setting of UPFC to enhance the system loadability. Firstly, we perform a multi power flow analysis with load incrementation to construct a global database to determine the initial efficient bounds associated to active power and reactive power target vector. Secondly a PSO technique applied to search the new parameters setting of the UPFC within the initial new active power and reactive power target bounds. The proposed approach is implemented with Matlab program and verified with IEEE 30-Bus test network. The results show that the proposed approach can converge to the near optimum solution with accuracy, and confirm that flexible multi-control of this device coordinated with efficient location enhance the system security of power system by eliminating the overloaded lines and the bus voltage violation.

• Structural Engineering and Mechanics
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• 제45권1호
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• pp.95-110
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• 2013

In the recent decade, practical of wavelet technique is being utilized in various domain of science. Particularly, engineers are interested to the wavelet solution method in the time series analysis. Fundamentally, seismic responses of structures against time history loading such as an earthquake, illustrates optimum capability of systems. In this paper, a procedure using particularly discrete Haar wavelet basis functions is introduced, to solve dynamic equation of motion. In the proposed approach, a straightforward formulation in a fluent manner is derived from the approximation of the displacements. For this purpose, Haar operational matrix is derived and applied in the dynamic analysis. It's free-scaled matrix converts differential equation of motion to the algebraic equations. It is shown that accuracy of dynamic responses relies on, access of load in the first step, before piecewise analysis added to the technique of equation solver in the last step for large scale of wavelet. To demonstrate the effectiveness of this scheme, improved formulations are extended to the linear and nonlinear structural dynamic analysis. The validity and effectiveness of the developed method is verified with three examples. The results were compared with those from the numerical methods such as Duhamel integration, Runge-Kutta and Wilson-${\theta}$ method.

• Steel and Composite Structures
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• 제16권2호
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• pp.135-156
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• 2014

In this research the effect of seismic design level as a practical approach for progressive collapse mitigation and reaching desired structural safety against it in seismically designed concentric braced frame buildings was investigated. It was achieved by performing preliminary and advanced progressive collapse analysis of several split-X braced frame buildings, designed for each seismic zone according to UBC 97 and by applying various Seismic Load Factors (SLFs). The outer frames of such structures were studied for collapse progression while losing one column and connected brace in the first story. Preliminary analysis results showed the necessity of performing advanced element loss analysis, consisting of Vertical Incremental Dynamic Analysis (VIDA) and Performance-Based Analysis (PBA), in order to compute the progressive collapse safety of the structures while increasing SLF for each seismic zone. In addition, by sensitivity analysis it became possible to introduce the equation of structural safety against progressive collapse for concentrically braced frames as a function of SLF for each seismic zone. Finally, the equation of progressive collapse safety as a function of bracing member capacity was presented.

• 한국철도학회논문집
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• 제14권1호
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• pp.39-48
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• 2011

본 논문에서는 열차가 주행할 때 궤도를 통해 전달되는 진동크기가 구조물의 안전성뿐 만아니라 선로 인근주민, 가축 및 건물에게 미치는 영향을 최소화하기 위해 규정된 진동한계범위에 도달하는 가를 다양한 지반과 궤도구조물의 상호작용에 의한 3D 수치해석을 통해 정확히 예측하고 다양한 지반에 적절한 진동저감을 가져오는 궤도의 단면 및 형태를 결정하는 방법에도 이결과를 사전에 활용할 수 있도록 하였다. 예로서 열차운행으로 인해 발생되는 터널, 성토 및 교량 3종류의 서로 다른 시설물의 진동을 지반-구조물의 상호작용에 의한 3D수치해석을 통해 Spec과 비교분석하여 평가하였으며 주변 환경에 적합한 토층의 변화를 통해 진동저감방법의 한예를 수행하였다.

• 조명전기설비학회논문지
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• 제25권3호
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• pp.50-64
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• 2011

In this paper, a DC-coupled photovoltaic (PV), fuel cell (FC) and ultracapacitor hybrid power system is studied for building microgrid. In this proposed system, the PV system provides electric energy to the electrolyzer to produce hydrogen for future use and transfer to the load side, if possible. Whenever the PV system cannot completely meet load demands, the FC system provides power to meet the remaining load. The main weak point of the FC system is slow dynamics, because the power slope is limited to prevent fuel starvation problems, improve performance and increase lifetime. A power management and control algorithm is proposed for the hybrid power system by taking into account the characteristics of each power source. The main works of this paper are hybridization of alternate energy sources with FC systems using long and short storage strategies to build an autonomous system with pragmatic design, and a dynamic model proposed for a PV/FC/UC bank hybrid power generation system. A simulation model for the hybrid power system has been developed using Matlab/Simulink, SimPowerSystems and Matlab/Stateflow. The system performance under the different scenarios has been verified by carrying out simulation studies using a practical load demand profile, hybrid power management and control, and real weather data.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1992년도 가을 학술발표회 논문집
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• pp.218-223
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• 1992

Some aspects of the design procedures of reinforced concrete slabs concerning microvibration behavior have to be considered. In this study, a numerical algorithm for the analysis of slabs to withstand the microvibration effects is developed. First, the evaluation criteria for controlling the microvibration of slabs is given from the literature survey. Second, the human-induced load model is developed by the experimental results. Finally, the procedure for the analysis of reinforced concrete slabs, with particular emphasis to the slab subject to human-induced dynamic load, is developed by the finite element method and is then examined by using the slab model tests, In addition, the effects of elastic modulus, mass, shape of slab, and support conditions on the microvibration behavior of reinforced concrete slabs are analyzed. It is concluded that the developed analysis procedure showns in accecptable accuracy compared with the experiments and the analysis procedure cab be easily appkied to the practical microvibration problems.

• 한국정밀공학회지
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• 제17권5호
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• pp.100-107
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• 2000

The hydraulic couplings have been widely used in industries, automobile, and power-station drives including ships. A mathematical analysis by which the design and application of hydraulic couplings are made is used in conventional design formulae and general roto-dynamic theories. The fluid flow of hydraulic couplings can be considered to have two component, one circumferentially about the coupling axis, and the other passing fluid from the pump to the turbine in the plane of the coupling axis. Tests have been carried out on the full-scale production coupling. The performance test consists of taking measurement of torque of the fluid coupling for three different amount of working fluid inside with various loads to the output shaft. The purpose of this research is to construct the experimental test equipments and to establish a series of performance test for the domestically developed hydraulic couplings, and to obtain experimental results which can be used to improve the performance of the hydraulic coupling and to solve the practical problems confronted in operation.

• 대한토목학회논문집
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• 제12권2호
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• pp.43-54
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• 1992

낮은 아치는 동하중 재하시 재료는 탄성범위 내에 있더라도 큰 변형이 발생할 수 있으며, 좌굴 가능성이 높기 때문에 선형해석으로는 정확한 거동을 구명하기 어렵다. 본 연구에서는 이에 따라 낮은 아치의 동적 비선형 해석방법 및 좌굴판단기준을 제시하였으며, 제시된 방법을 토대로 낮은 아치의 동적 비선형 해석을 수행하고 임계좌굴하중을 구하였다. 형상의 비선형성은 Lagrangian 운동좌표를 고려하여 해석하였으며 동적운동방정식을 풀기 위하여 유한요소법을 사용하였다. 이 때, 동적 운동방정식의 시간적분으로 Newmark 해법을 채택하였다. 프로그램은 만재 방사형 등분포하중을 받는 낮은 원호 아치를 해석하여 그 결과치를 다른 연구결과와 비교하여 검증하였다. 모형해석을 통해서는 큰 동하중을 받는 원호 아치는 기하학적 비선형 거동을 고려하여 해석되어야 하며, 아치가 낮아질수록 좌굴발생 가능성이 높아짐을 알았다. 여러가지 형상의 아치에 대한 좌굴해석을 실시하여 임계 좌굴하중을 구하였으며 기존의 연구와 비교하여 정확성을 확인하였다. 원호 아치의 거동을 본 연구에서 사용한 무차원 매개변수를 이용하여 해석한 결과로 부터, 동일한 형상매개변수를 가진 아치들은 실제하중을 하중매개변수로 환산하여 같은 하중매개변수를 재하했을 때 시간매개변수에 따라 처짐비를 기준으로 같은 거동을 함을 알았으며, 좌굴현상도 같은 하중매개변수에서 나타남을 확인하였다. 또한, 포물선형상의 아치와 연직하중이나 집중하중이 재하된 경우의 해석에도 개발된 프로그램이 유용하게 사용될 수 있음을 해석예를 통하여 밝혔다.

• International Journal of Aeronautical and Space Sciences
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• 제12권3호
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• pp.225-240
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• 2011

Active and shape morphing aerospace structures are discussed with a focus on activities aimed at practical implementation. In active structures applications range from dynamic load alleviation in aircraft and spacecraft up to static and dynamic shape control. In contrast, shape morphing means strong shape variation according to different mission status and needs, aiming to enhance functionality and performance over wide flight and mission regimes. The interaction of required flexible materials with the morphing structure and the actuating mechanisms is specifically addressed together with approaches in design and simulation.

• Structural Engineering and Mechanics
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• 제37권5호
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• pp.475-487
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• 2011

In a flexible multi-body dynamic system the typical topological optimization method for structures cannot be directly applied, as the stiffness varies with position. In this paper, the topological optimization of the flexible multi-body dynamic system is converted into structural optimization using the equivalent static load method. First, the actual boundary conditions of the control system and the approximate stiffness curve of the mechanism are obtained from a flexible multi-body dynamical simulation. Second, the finite element models are built using the absolute nodal coordination for different positions according to the stiffness curve. For efficiency, the static reanalysis method is utilized to solve these finite element equilibrium equations. Specifically, the finite element equilibrium equations of key points in the stiffness curve are fully solved as the initial solution, and the following equilibrium equations are solved using a reanalysis method with an error controlled epsilon algorithm. In order to identify the efficiency of the elements, a non-dimensional measurement is introduced. Finally, an improved evolutional structural optimization (ESO) method is used to solve the optimization problem. The presented method is applied to the optimal design of a die bonder. The numerical results show that the presented method is practical and efficient when optimizing the design of the mechanism.