• Journal of Ocean Engineering and Technology
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• v.18 no.6 s.61
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• pp.1-7
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• 2004

This paper deals with the performance analysis of the impulse turbine for a owe type wave energy conversion device. Numerical analysis was performed using the commercially-available software FLUENT. This parametric study includes variation of the setting angle of the guide vane. Since parametric study at various flow coefficients requires a tremendous amount of computing time, two-dimensional cascade flow approximation was employed to determine the optimum principal particulars in a rather simple manner. A Full three-dimensional calculation was also performed for several cases to confirm the validity of the two-dimensional approach. Results were compared to other experimental data, such as Setoguchi et al. (2001)'s extensive set of data, and found that the usefulness of 2-D analysis was well demonstrated. The advantages of each method were also evaluated.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.8
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• pp.821-827
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• 2015

This study concentrates on a wave energy converter with floaters that extracts the ocean's energy by moving up and down with the wave motion. The floater is connected to an arm structure, including a hydraulic cylinder that drives a hydraulic generator. This study focuses on a structural analysis of the floater unit, including arm and cylinder components, platform and jack-up system, along with spud columns. Previous studies have been conducted for miniature models for experimentation, but this study focuses on the full-scale model structural analysis. Static structural analysis is conducted using fine numerical grids. Due to the complexity of the whole model, it is analyzed in separate pieces. The floater unit, with arm and cylinder, are combined into one system. The platform is analyzed separately as a single system. There are four jack-up systems for each spud column; only one jack-up system is analyzed, as uniform loads are assumed on each system. There are several load cases for each system, all of which are analyzed thoroughly for stress (von Mises, shear, and normal) and deformation. Acceptable results were obtained for most of the components; unsafe components were redesigned.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.6
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• pp.35-42
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• 2010

We use conformal mapping method to derive the analytical expressions for calculating electrostatic fields and electric potentials surrounding the conductor-backed coupled coplanar waveguide(CBCCPW) structure. Using the derived expressions, the electrostatic fields and potentials are computed at various points of the CBCCPW's geometry and the field and potential distributions are analyzed. The proposed method provides a faster and simpler calculation of the field distributions than the full-wave analysis method because no iterations are required. This method can be widely applied to the analysis of microwave integrated circuits using coupled line, such as coupler, filter, and microstrip antenna.

• Journal of the Korea Institute of Military Science and Technology
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• v.9 no.2 s.25
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• pp.26-33
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• 2006

A sonar dome is basically designed and installed to protect sonar array from shocks, sea wave slaps and floating matters. The acoustic wave passing through sonar dome, however, can be distorted in magnitude and phase. This paper presents a numerical method for predicting the steady-state sound pressure on the surface of transducer array in the sonar dome and typical results of sonar beam pattern affected by sonar dome. A beam tracing model with phase information and a multi-layered elastic boundary model are involved. A full three-dimensional sonar dome is modeled as a GRP acoustic window, a rubber coated steel baffle and a rubber coated steel hull. A transducer array is modeled as thick steel cylinder. There are some assumptions such as incidence of plane wave, specular reflection on boundary and directionality of transducer element.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.3 s.357
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• pp.26-34
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• 2007

This Paper describes a chip design technique for body composition analyzer based on the BIA (Bioelectrical Impedance Analysis) method. All the functions of signal forcing circuits to the body, signal detecting circuits from the body, Micom, SRAM and EEPROMS are integrated in one chip. Especially, multi-frequency detecting method can be applied with selective band pass filter (BPF), which is designed in weak inversion region for low power consumption. In addition new full wave rectifier (FWR) is also proposed with differential difference amplifier (DDA) for high performance (small die area low power consumption, rail-to-rail output swing). The prototype chip is implemented with 0.35um CMOS technology and shows the power dissipation of 6 mW at the supply voltage of 3.3V. The die area of prototype chip is $5mm\times5mm$.

• Journal of the Korean Geotechnical Society
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• v.25 no.4
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• pp.5-17
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• 2009

In HWAW method, experimental dispersion curve is obtained through time-frequency analysis, and inversion procedure is based on the forward modeling which considers full wavefield. Therefore, it enables us to use relatively short testing setup and has advantage for two dimensional subsurface imaging compared with another surface wave methods. Numerical study was performed to verify that the HWAW method can be applied to non-horizontally layerd soil structure. The experimental dispersion curves obtained from HWAW method agreed with the theoretical dispersion curves based on full wavefield. Experimental dispersion curves are mainly more affected by the region between two receivers than by the region from source to the first receiver. Fluctuation phenomena of dispersion curve can be reduced by adequate receiver spacing setup. From numerical study, it was thought that reliable Vs distribution map can be constructed by HWAW method and finally subsurface imaging was tried in the real field.

• Journal of Aerospace System Engineering
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• v.15 no.6
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• pp.59-65
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• 2021

In this paper, the transmission characteristics of the multi-layered composite material with wire mesh and honeycomb core for aircraft applications have been analyzed with the proposed method. The proposed method converts the conductive wire mesh into effective layer, while for the dielectric honeycomb core, effective permittivity has been derived based on volume fraction with the proposed method. The proposed method has been verified through comparison with full-wave simulation and revealed excellent. In addition, the calculation time of the proposed method is a few order of magnitude faster in comparison with the full-wave simulation.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.2
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• pp.146-151
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• 2016

This study concentrates on the design of floater for 15kW-class wave energy converter that extracts the ocean energy by oscillating vertically along the wave motion. The floater connects to a arm structure that connects to a hydraulic cylinder, which drives a hydraulic generator. The study mainly focuses on the structural analysis of the floater. Previous studies have been conducted using a miniature model; however, this study focuses on the size selection of the floater for a full scale model. Static structural analysis is conducted using fine numerical grids. Due to the complexity of the whole model, it is analyzed as a separate component. There are several load cases for each floater size, and they are analyzed thoroughly for stress (von-mises, shear, and normal) and deformation. The initial design was conducted by scaling up from the miniature model of the previous study, and the final design has been redesigned by changing the thickness and internal support structure shape.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.4
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• pp.101-112
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• 2004

In this paper, we developed a numerical analysis model by using ADI-FDTD method to analyze three-dimensional interconnect structure. We discretized maxwell's curl equation by using ADI-FDTD. Using ADI-FDTD method, a sampler circuit designed from 3.3 V CMOS technology is simplified to 3-metal line structure. Using this simplified structure, the time delay and signal distortion of complex interconnects are investigated. As results of simulation, 5∼10 ps of delay time and 0.1∼0.2 V of signal distortion are measured. As demonstrated in this paper, the full-wave analysis using ADI-FDTD exhibits a promise for accurate modeling of electromagnetic phenomena in high-speed VLSI interconnect.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.4
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• pp.775-786
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• 2002

A Mixed Volume and Boundary Integral Equation Method is applied for the effective analysis of elastic wave scattering problems and plane elastostatic problems in unbounded solids containing general anisotropic inclusions and voids or isotropic inclusions. It should be noted that this newly developed numerical method does not require the Green's function for anisotropic inclusions to solve this class of problems since only Green's function for the unbounded isotropic matrix is involved in their formulation for the analysis. This new method can also be applied to general two-dimensional elastodynamic and elastostatic problems with arbitrary shapes and number of anisotropic inclusions and voids or isotropic inclusions. In the formulation of this method, the continuity condition at each interface is automatically satisfied, and in contrast to finite element methods, where the full domain needs to be discretized, this method requires discretization of the inclusions only. Finally, this method takes full advantage of the pre- and post-processing capabilities developed in FEM and BIEM. Through the analysis of plane elastostatic problems in unbounded isotropic matrix with orthotropic inclusions and voids or isotropic inclusions, and the analysis of plane wave scattering problems in unbounded isotropic matrix with isotropic inclusions and voids, it will be established that this new method is very accurate and effective for solving plane wave scattering problems and plane elastic problems in unbounded solids containing general anisotropic inclusions and voids/cracks or isotropic inclusions.