• 한국소음진동공학회논문집
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• 제19권11호
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• pp.1110-1118
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• 2009

This paper presents an optimal design of magnetorheological(MR) damper based on analytical methodology and finite element analysis. The proposed MR damper consists of MR valve and gas chamber. The MR valve is constrained in a specific volume and the optimization problem identifies geometric dimensions of the valve structure that maximize the pressure drop of the MR valve or damping force of the MR damper. In this work, the single-coil annular MR valve structure is considered. After describing the schematic configuration and operating principle of MR valve and damper, a quasi-static model is derived based on Bingham model of MR fluid. The magnetic circuit of the valve and damper is then analyzed by applying the Kirchoff' s law and magnetic flux conservation rule. Based on the quasi-static modeling and the magnetic circuit analysis, the optimization problem of the MR valve and damper is built. The optimal solution of the optimization problem of the MR valve structure constrained in a specific volume is then obtained and compared with the solution obtained from finite element method.

• Wind and Structures
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• 제29권6호
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• pp.441-455
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• 2019

In this study, vortex induced vibrations of a cylinder mounted on a flexible rod are analyzed. This simple configuration represents the key element of new conception bladeless wind turbine (Whitlock 2015). In this study the structure oscillations equation coupled to the wake oscillation equation for this configuration are solved using analytical perturbation method, for the first time. An analytical expression that predicts the lock-in phenomena range of wind speed is derived. The discretized equations of motion are also solved using RKF45 numerical method. The equations of motion are discretized by Galerkin method. Free vibration mode shape of the structure taking into account the discontinuity of the cross section are used as comparison function. Numerical results are compared to the analytical results, and they show a satisfying agreement. The effect of system parameters on the oscillations of structure and wake as well as on the lock-in domain are presented. Moreover, it is shown that the values of wind speed triggering the start and the stop of the lock-in phenomenon, for increasing wind speed are different from those values obtained during the reverse process, i.e., when the wind speed decreases.

• 한국해안해양공학회지
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• 제19권5호
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• pp.436-445
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• 2007

연속방정식 및 운동방정식을 사용하여 임의의 수심에 적용이 가능한 장파의 해를 해석적인 방법을 사용하여 유도하였다. 수심이 선형적으로 변화할 경우 지배 방정식의 해가 Bessel 함수로 표현된다는 사실을 응용하여 임의의 수심을 선형적으로 변화하는 구간의 연속으로 가정하여 해를 유도하였다. 기존에 유도된 해석 해와 비교를 하여 본 논문에서 유도된 해석 해의 타당성을 검증하였으며, 직립 구조물에 적용하여 해저 지형이 직립구조물의 처오름에 끼치는 영향을 조사하였다.

• 한국물환경학회지
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• 제20권6호
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• pp.555-562
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• 2004

This paper presents the development and application of a riparian buffer zone design model(RBZDM). The model was developed as a decision-making tool for watershed management, by integrating geographic information system(GIS) and analytical hierarchy process(AHP) theory. Several factors for watershed management, such as pollution removal capacity, land aquisition cost, distribution of point and non-point pollution sources, and possibility of new pollution source location, were analyzed based on AHP theory. The vegetated buffer zone width was designed using GIS-based riparian buffer analysis. The developed model was applied to the Kyoungan Stream watershed, which is an important part of Paldang lake catchment area. The Kyoungan stream watershed was divided into sixteen subbasins. Six of them belong to the main stem, where the model was applied. Ten alternatives of buffer zone width and five hierarchial levels were designed. The relative importance and the relative preference were computed by pair-wise comparison of evaluation criteria given in hierarchial levels. The buffer zone width was determined by linear function of the given alternatives and relative preferences. From this study, it was determined that the six buffer zone widths of Kyoungan main stems would be 1,594, 1,744, 1,856, 1,782, 1,338, 1,780 meter, from upstream to downstream.

• Journal of Magnetics
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• 제19권2호
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• pp.130-139
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• 2014

This paper focuses on the modeling and analysis a novel two-axis rotary normal-stress electromagnetic actuator with compact structure for fast steering mirror (FSM). The actuator has high force density similar to a solenoid, but its torque output is nearly a linear function of both its driving current and rotation angle, showing that the actuator is ideal for FSM. In addition, the actuator is designed with a new cross topology armature and no additional axial force is generated when the actuator works. With flux leakage being involved in the actuator modeling properly, an accurate analytical model of the actuator, which shows the actuator's linear characteristics, is obtained via the commonly used equivalent magnetic circuit method. Finally, numerical simulation is presented to validate the analytical actuator model. It is shown that the analytical results are in a good agreement with the simulation results.

• Journal of Pharmaceutical Investigation
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• 제38권6호
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• pp.399-403
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• 2008

The aim of this study was to evaluate the difference of analytical methods for the pharmacokinetic study of bromosulfophthalein (BSP), an indicator of hepatobiliary function. The plasma and bile concentrations of BSP after intravenous administration were measured according to custom UV spectroscopy and HPLC, respectively. Plasma concentration of BSP measured by UV spectroscopy was similar to that measured by HPLC. There was no significant difference in the distribution volume, total body clearance, area under the curve and mean residence time of BSP between different analytical method groups. However, bile concentration of BSP measured by UV spectroscopy was overestimated compared with concentration measured by HPLC method. Biliary clearance of BSP obtained from UV spectroscopy method was almost 3 times higher than that obtained from HPLC method. Thus, a feasibility of UV spectroscopy method for high throughput pharmacokinetic evaluation of BSP was limited to the study based on the plasma concentration of BSP, not bile concentration.

• 드라이브 ㆍ 컨트롤
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• 제15권2호
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• pp.22-31
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• 2018

This study deals with verifying the design feasibility, of an independently driving hydraulic system for disaster response purposes, through an analytical approach. The development target is a system in which four traveling motors are driven independently, and must be easy to operate even under conditions in which different loads are applied to the traveling motors. In order to be suitable for complex work, the hydraulic system was designed using the main control valve with a pressure compensation function. If we can develop an analytical model that reflects the specifications and functions of the parts through the analysis program, we can verify the validity of the design before we make the prototype. The purpose of this study therefore, is to verify the feasibility of designing an independent drive hydraulic system through the development of an analysis model from the viewpoint of complex work. The analysis program uses Simulation X.

• 대한전자공학회논문지SD
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• 제46권6호
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• pp.1-5
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• 2009

6H-SiC 전자 및 정공의 이온화계수로부터 유효이온화계수를 추출하여 6H-SiC PN 다이오드의 항복전압과 온-저항을 위한 해석적 표현식을 유도하였다. 해석적 모형으로부터 구한 항복전압을 $10^{15}{\sim}10^{18}\;cm^{-3}$의 도핑 농도 범위에서 실험 결과와 비교하여 10% 이내의 오차로 일치하였고, 농도 함수의 온-저항의 해석적 결과도 $5{\times}10^{15}{\sim}10^{16}\;cm^{-3}$의 범위에서 이미 발표된 수치적 결과와 매우 잘 일치하였다.

• Structural Engineering and Mechanics
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• 제73권4호
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• pp.407-426
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• 2020

In this present paper, a semi-analytical mesh-free method is employed for the three-dimensional free vibration analysis of a bi-directional functionally graded piezoelectric circular structure. The dependent variables have been expanded by Fourier series with respect to the circumferential direction and have been discretized through radial and axial directions based on the mesh-free shape function. The current approach has a distinct advantage. The nonlinear Green-Lagrange strain is employed as the relationship between strain and displacement fields to observe thermal impacts in stiffness matrices. Nevertheless, high order terms have been neglected at the final steps of equations driving. The material properties are assumed to vary continuously in both radial and axial directions simultaneously in accordance with a power law distribution. The convergence and validation studies are conducted by comparing our proposed solution with available published results to investigate the accuracy and efficiency of our approach. After the validation study, a parametric study is undertaken to investigate the temperature effects, different types of polarization, mechanical and electric boundary conditions and geometry parameters of structures on the natural frequencies of functionally graded piezoelectric circular structures.

• Coupled systems mechanics
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• 제9권6호
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• pp.539-562
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• 2020

In this paper the linear elastic coupling between a 2 degree of freedom shear-type frame system and a rigid block is analytically and experimentally investigated. As demonstrated by some of the authors in previous papers, it is possible to choose a coupling system able to guarantee advantages, whatever the mechanical characteristics of the frame. The main purpose of the investigation is to validate the analytical model. The nonlinear equations of motion of the coupled system are obtained by a Lagrangian approach and successively numerically integrated under harmonic and seismic excitation. The results, in terms of gain graphs, maps and spectra, represent the ratio between the maximum displacements or drifts of the coupled and uncoupled systems as a function of the system's parameters. Numerical investigations show the effectiveness of the nonlinear coupling for a large set of parameters. Thus experimental tests are carried out to verify the analytical results. An electro-dynamic long-stroke shaker sinusoidally and seismically forces a shear-type 2 d.o.f frame coupled with a rigid aluminium block. The experimental investigations confirm the effectiveness of the coupling as predicted by the analytical model.