• 한국항행학회논문지
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• 제23권4호
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• pp.309-315
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• 2019

본 논문은 1:3과 1:4 분배 비율을 갖는 비대칭 분배기를 CPW와 offset 결합 전송선로를 이용하여 다단 구조로 구현한 것이다. 이 분배기는 다단 구조의 전송선로와 캐패시터와 저항이 병렬로 연결된 회로로 구성되어 있다. 다단 전송선로는 임의의 임피던스로 종단된 ${\lambda}/4$ 단일 전송선로를 분해하여 그것을 $90^{\circ}$ 전기적 길이보다 짧은 다단 전송선로로 정합시키는 방법으로 구현하였고, RC 병렬회로는 출력 포트의 반사계수와 출력 포트 사이의 고립 특성을 얻기 위해서 전송선로 사이에 연결하였다. 이러한 방법으로 2 GHz에서 설계된 전력분배기는 각 단의 전송선로는 ${\lambda}/4$보다 짧게 구현되어 기존 것 보다 최소 27% 작게 구현하였고, 광 대역 특성을 얻을 수 있음을 확인하였다.

• 한국해양공학회지
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• 제37권6호
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• pp.273-281
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• 2023

Recently, offshore structures for eco-friendly energy, such as wind and solar power, have been developed to address the problem of insufficient land space; in the case of energy generation, they are designed on a considerable scale. Therefore, the scalability of offshore structures is crucial. The Korea Research Institute of Ships & Ocean Engineering (KRISO) developed multi-linked floating offshore structures composed of floating bodies and connection beams for floating photovoltaic systems. Large-scale floating photovoltaic systems are mainly designed in a manner that expands through the connection between modules and demonstrates a difference in structural response with connection conditions. A fluid-structure coupled analysis was performed for the multi-linked floating offshore structures. First, the wave load acting on the multi-linked offshore floating structures was calculated through wave load analysis for various wave load conditions. The response amplitude operators (RAOs) for the motions and structural response of the unit structure were calculated by performing finite element analysis. The effects of connection conditions were analyzed through comparative studies of RAOs and the response's maximum magnitude and occurrence location. Hence, comparing the cases of a hinge connection affecting heave and pitch motions and a fixed connection, the maximum bending stress of the structure decreased by approximately 2.5 times, while the mooring tension increased by approximately 20%, confirmed to be the largest change in bending stress and mooring tension compared to fixed connection. Therefore, the change in structural response according to connection condition makes it possible to design a higher structural safety of the structural member through the hinge connection in the construction of a large-scale multi-linked floating offshore structure for large-scale photovoltaic systems in which some unit structures are connected. However, considering the tension of the mooring line increases, a safety evaluation of the mooring line must be performed.

• Journal of Power Electronics
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• 제13권2호
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• pp.214-222
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• 2013

This paper proposes a high efficiency step-down flyback converter using a coaxial-cable coupled-inductor which has a higher primary-secondary flux linkage than sandwich winding transformers. The structure of the two-winding coaxial cable transformer is described, and the coupling coefficient of the coaxial cable transformer and that of a sandwich winding transformer are compared. A circuit model of the proposed transformer is also obtained from the frequency-response curves of the secondary short-circuit and of the secondary open-circuit. Finally, the performance of the proposed transformer is validated by the experimental results from a 35W single-output flyback converter prototype. In addition, the proposed two-winding coaxial transformer is extended to a multiple winding coaxial application. For the performance evaluation of the extended version, 35W multi-output hardware prototype of the DC-DC flyback converter was tested.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 Proceedings of the Korea Automatic Control Conference, 11th (KACC); Pohang, Korea; 24-26 Oct. 1996
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• pp.380-384
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• 1996

This paper represents an adaptive position controller with the disturbance observer for multi-axis servo system. The overall control system consists of three parts : the position controller, the disturbance observer with free parameters and cross-coupled controller which enhances contouring performance by reducing errors. Using two-degrees-of freedom conception, we design the command input response and the closed loop characteristics independently. The servo system can improve the closed loop characteristics without affecting the command input response. The characteristics of the closed loop system is improved by suppressing disturbance torque effectively with the disturbance observer. Moreover, the cross-coupled controller enhances tracking performance. Thus total position control performance is improved. Finally, the performance of the proposed controller shows that it improves the contouring performance along with the reference trajectory in the XY-table.

• 한국군사과학기술학회지
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• 제3권1호
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• pp.155-163
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• 2000

A general characterization procedure based on the extraction of a 2n-port admittance matrix corresponding to n uniform coupled lines on the multi-layered substrate using the Finite-Difference Time-Domain (FDTD) technique is presented. The frequency-dependent normal mode parameters are obtained from the 2n-port admittance matrix, which in turn provides the frequency-dependent distributed inductance and capacitance matrices. To illustrate the technique, several practical coupled line structures on multi-layered substrate, including a three-line structure, have been simulated. It is shown that the FDTD based time domain characterization procedure is an excellent broadband simulation tool for the design of multiconductor coupled lines on multilayered PCBs as well as thick or thin hybrid structures.

• Structural Engineering and Mechanics
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• 제28권4호
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• pp.479-489
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• 2008

In this study an approximate method based on the continuum approach and transfer matrix method for static and dynamic analyses of stiffened multi-bay coupled shear walls is presented. In this method the whole structure is idealized as a sandwich beam. Initially the differential equation of this equivalent sandwich beam is written then shape functions for each storey is obtained by the solution of differential equations. By using boundary conditions and storey transfer matrices which are obtained by these shape functions, system modes and periods can be calculated. Reliability of the study is shown with a few examples. A computer program has been developed in MATLAB and numerical samples have been solved for demonstration of the reliability of this method. The results of the samples show the agreement between the present method and the other methods given in literature.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2017년도 전력전자학술대회
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• pp.88-89
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• 2017

This paper investigates the design of multi-winding coupled inductor for minimum inductor current ripple in rapid traction battery charger systems. Based on the general circuit model of multi-winding coupled inductor together with the operating principles of dc-dc converter, the relationship between the ripple size of inductor current and the coupling factor is derived under the different duty ratio. The optimal coupling factor which corresponds to a minimum inductor ripple current becomes -(1/n-1), i.e. a complete inverse coupling without leakage inductance, as the steady-state duty ratio operating point approaches 1/n, 2/n, … or (n1)/n. In an opposite manner, the optimal coupling factor value of zero, i.e. zero mutual inductance, is required when the steady-state duty ratio operating point approaches either zero or one.

• International Journal of Control, Automation, and Systems
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• 제4권2호
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• pp.255-270
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• 2006

In this paper, a design method of nonlinear autopilot for ship-to-ship missiles is proposed. Ship-to-ship missiles have strongly coupled dynamics through roll, yaw, and pitch channel in comparison with general STT type missiles. Thus it becomes difficult to employ previous control design method directly since we should find three different solutions for each control fin deflection and should verify the stability for more complicated dynamics. In this study, we first propose a control loop structure for roll, yaw, and pitch autopilot which can determine the required angles of all three control fins. For yaw and pitch autopilot design, missile model is reduced to a minimum phase model by applying a singular perturbation like technique to the yaw and pitch dynamics. Based on this model, a multi-input multi-output (MIMO) nonlinear autopilot is designed. And the stability is analyzed considering roll influences on dynamic couplings of yaw and pitch channel as well as the aerodynamic couplings. Some additional issues on the autopilot implementation for these coupled missile dynamics are discussed. Lastly, 6-DOF (degree of freedom) numerical simulation results are presented to verify the proposed method.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1992년도 봄 학술발표회 논문집
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• pp.58-64
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• 1992

It is usual that underground structures are constructed within multi-layered medium. In this paper, an efficient numerical model ling of multi-layered structural systems is studied using coupled analysis of finite elements and boundary elements. The finite elements are applied to the area in which the material nonlinearity is dominated, and the boundary elements are applied to the far field area where the nonlinearity is relatively weak. In the boundary element model 1 ins of the multi-layered medium, fundamental solutions are restricted. Thus, methods which can utilize existing Kelvin and Melan solution are sought for the interior multi-layered domain problem and semi infinite domain problem. Interior domain problem which has piecewise homogeneous layers is analyzed using boundary elements with Kelvin solution; by discretizing each homogeneous subregion and applying compatibility and equilibrium conditions between interfaces. Semi-infinite domain problem is analyzed using boundary elements with Melan solution, by superposing unit stiffness matrices which are obtained for each layer by enemy method. Each methodology is verified by comparing its results which the results from the finite element analysis and it is concluded that coupled analysis using boundary elements and finite elements can be reasonable and efficient if the superposition technique is applied for the multi-layered semi-infinite domain problems.

• Nuclear Engineering and Technology
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• 제56권3호
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• pp.980-992
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• 2024

Steam line break accident (SLB) in the nuclear reactor is one of the representative Non-LOCA accidents in which thermal-hydraulics and neutron kinetics are strongly coupled each other. Thus, the multi-scale and multi-physics approach is applied in this study in order to examine a realistic safety margin. An entire reactor coolant system is modelled by system scale node, whereas sub-channel scale resolution is applied for the region of interest such as the reactor core. Fuel performance code is extended to consider full core pin-wise fuel behaviour. The MARU platform is developed for easy integration of the codes to be coupled. An initial stage of the steam line break accident is simulated on the MARU platform. As cold coolant is injected from the cold leg into the reactor pressure vessel, the power increases due to the moderator feedback. Three-dimensional coolant and fuel behaviour are qualitatively visualized for easy comprehension. Moreover, quantitative investigation is added by focusing on the enhancement of safety margin by means of comparing the minimum departure from nucleate boiling ratio (MDNBR). Three factors contributing to the increase of the MDNBR are proposed: Various geometric parameters, realistic power distribution by neutron kinetics code, Radial coolant mixing including sub-channel physics model.