• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.1
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• pp.100-110
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• 1994

In this paper, we present a new analysis of monolithic laser-waveguide coupling structure employing the beam propagation method. Monolithic laser-waveguide coupler has both passive and active components It has too many parameters to consider for an analysis. So we present proper model of coupler by use of directional coupler. We employ the beam propagation method th analyze the proposed structure, we could employ the coupled mode theory but we thought in the case of this paper the beam propagation method is more appropriate than coupler mode theorybecause a number of variables which to consider is too many for the coupled mode theory. Also we use finite difference method to calcurate trial field which is a starting point of beam propagation analysis. Through this approach, we can consider more parameters. And we propose a new structure of monolothic laser-waveguide coupler which has taper structure between the distance in which coupling is taking place and passive waveguide. We can obtain 79% high coupling efficiency from our structure.

• Journal of Astronomy and Space Sciences
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• v.24 no.4
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• pp.397-408
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• 2007

Diplexer is one of core devices needed to communicate with satellite using single ground antenna by separating uplink and downlink signal. This paper presents the design of the S-band diplexer for LEO TT&C application, especially for KOMPSAT (KOrea Multi-Purpose SATellite). To cope with requirements such as high handling power, low insertion loss, air-cavity resonator with high quality factor was considered as one of design drivers. Design was started with predicting unloaded Q and equivalent circuit from the structure of air-cavity resonator. For the convenience of adjustment, the coupling factor placed between resonators was estimated from COTSEM (Electro-Magnetic) simulator, EESOF $ADS^{TM}$, and expressed with 2-order polynomial regression. To improve the isolation between transmitting part (Tx) and receiving part (Rx), the inductive and capacitive attenuation poles were inserted between $4^{th}\;and\;6^{th}$ resonator respectively. The fabricated diplexer consists of two bandpass filters and each filter has eight resonants. From the measurement, it was shown that major requirements such as 0.5dB of insertion loss, 20dB of return loss and 100dB of isolation were fully satisfied within passband.

• Journal of Korean society of Dental Hygiene
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• v.12 no.2
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• pp.235-249
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• 2012

Objectives : The purpose of this research is to use data from the third year of the 4th National Health and Nutrition Examination Survey to study relationship between oral disease and chronic disease that generally persist from 6 months to over a year, or more specifically, circulatory disease, diabetes, and osteoporosis. Methods : Of the data from the third year of the 4th National Health and Nutrition Examination Survey, 7,893 adults over 19 years old who completed medical examination, health survey, and nutrition survey were selected as the final research subjects. Relationship between chronic disease and oral disease was analyzed by cross tabulation (2-test) and logistic regression analysis using SPSSWIN ver 18.0. Results : 1. Differences in the rate of prevalence of periodontal disease and the rate of prevalence of missing teeth were statistically significant with respect to age, gender, marital status, education level, residential area, income level, and occupation. Rate of prevalence of dental caries was statistically significant with respect to age, education level, and income level. 2. After examining the relationship between existence of chronic disease as diagnosed by doctor with oral disease, rate of prevalence of periodontal disease and missing teeth, hypertension, hyperlipidemia, stroke, myocardial infarction, angina, diabetes, and osteoporosis showed statiscally significant difference. 3. Examination of rate of prevalence of chronic disease with respect to oral disease, periodontal disease and missing teeth exerted statistically significant influence on hypertension, hyperlipidemia, stroke, myocardial infarction, angina, diabetes, and osteoporosis (p<0.05), while dental caries did not have statistically significant effect. 4. Analysis of coupling effect of periodontal disease and missing teeth on chronic disease showed that they were related in all chronic diseases examined in this study (hypertension, hyperlipidemia, stroke, myocardial infarction, angina, diabetes, and osteoporosis) (p<0.05). Conclusions : Periodontal disease and missing teeth were found to increase the rate of prevalence of chronic disease.

• Structural Engineering and Mechanics
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• v.72 no.4
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• pp.421-432
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• 2019

In high-speed railway (HSR) system, the structure-borne noise inside viaduct at low frequency has been extensively investigated for its mitigation as a research hotspot owing to its harm to the nearby residents. This study proposed a novel acoustic optimization method for declining the structure-borne noise in viaduct-like structures by separating the acoustic contribution of each structural component in the measured acoustic field. The structural vibration and related acoustic sourcing, propagation, and radiation characteristics for the viaduct box girder under passing vehicle loading are studied by incorporating Finite Element Method (FEM) with Modal Acoustic Vector (MAV) analysis. Based on the Modal Acoustic Transfer Vector (MATV), the structural vibration mode that contributes maximum to the structure-borne noise shall be hereinafter filtered for the acoustic radiation. With vibration mode shapes, the locations of maximum amplitudes for being ribbed to mitigate the structure-borne noise are then obtained, and the structure-borne noise mitigation performance shall be eventually analyzed regarding to the ribbing conduction. The results demonstrate that the structural vibration and structure-borne noise of the viaduct box girder mainly occupy both in the range within 100 Hz, and the dominant frequency bands both are [31.5, 80] Hz. The peak frequency for the structure-borne noise of the viaduct box girder is mainly caused by $16^{th}$ and $62^{th}$ vibration modes; these two mode shapes mainly reflect the local vibration of the wing plate and top plate. By introducing web plate at the maximum amplitude of main mode shapes that contribute most to the acoustic modal contribution factors, the acoustic pressure peaks at the field-testing points are hereinafter obviously declined, this implies that the structure-borne noise mitigation performance is relatively promising for the viaduct.

• Nuclear Engineering and Technology
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• v.55 no.6
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• pp.2230-2245
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• 2023

KANT (KAIST Advanced Nuclear Tachygraphy) is a PWR core simulator recently developed at Korea Advance Institute of Science and Technology, which solves three-dimensional steady-state and transient multigroup neutron diffusion equations under Cartesian geometries alongside the incorporation of thermal-hydraulics feedback effect for multi-physics calculation. It utilizes the standard Nodal Expansion Method (NEM) accelerated with various Coarse Mesh Finite Difference (CMFD) methods for neutronics calculation. For thermal-hydraulics (TH) calculation, a single-phase flow model and a one-dimensional cylindrical fuel rod heat conduction model are employed. The time-dependent neutronics and TH calculations are numerically solved through an implicit Euler scheme, where a detailed coupling strategy is presented in this paper alongside a description of nodal equivalence, macroscopic depletion, and pin power reconstruction. For validation of the steady, transient, and depletion calculation with pin power reconstruction capacity of KANT, solutions for various benchmark problems are presented. The IAEA 3-D PWR and 4-group KOEBERG problems were considered for the steady-state reactor benchmark problem. For transient calculations, LMW (Lagenbuch, Maurer and Werner) LWR and NEACRP 3-D PWR benchmarks were solved, where the latter problem includes thermal-hydraulics feedback. For macroscopic depletion with pin power reconstruction, a small PWR problem modified with KAIST benchmark model was solved. For validation of the multi-physics analysis capability of KANT concerning large-sized PWRs, the BEAVRS Cycle1 benchmark has been considered. It was found that KANT solutions are accurate and consistent compared to other published works.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.7
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• pp.748-756
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• 2007

In SIR filter, fringing capacitances and discontinuities yield a distorted frequency response from those expected by design formulas, especially in higher frequencies. In this paper, a procedure is presented in order to compensate for fringing capacitances and step impedance discontinuities by EM simulation for a 5th order SIR filter. This method propose the procedure of tuning the coupling and the length of individual resonator by EM simulation. For the filter composed by the tuned resonators, no further tuning is required. The procedure is experimentally justified by comparing the measured data of the fabricated filter with the simulation results.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.343-349
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• 2011

A loosely coupling method is adopted to combine a computational fluid dynamics (CFD) solver and the comprehensive structural dynamics (CSD) code, CAMRAD II, in a systematic manner to correlate the airloads, vortex trajectories, blade motions, and structural loads of the HART I rotor in descending flight condition. A three-dimensional compressible Navier-Stokes solver, KFLOW, using chimera overlapped grids has been used to simulate unsteady flow phenomena over helicopter rotor blades. The number of grids used in the CFD computation is about 24 million for the isolated rotor and about 37.6 million for the rotor-fuselage configuration while keeping the background grid spacing identical as 10% blade chord length. The prediction of blade airloads is compared with the experimental data. The current method predicts reasonably well the BVI phenomena of blade airloads. The vortices generated from the fuselage have an influence on airloads in the 1st and 4th quadrants of rotor disk. It appeared that presence of the pylon cylinder resulted in complex turbulent flow field behind the hub center.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.4
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• pp.382-389
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• 1997

We present the results on the applicability of the polycrystalline AIN thin films for a surface acoustic wave filter operating at 800 MHz frequency. The films show the FWHM of 3 .deg. from th X-ray rocking curve, which indicates that the c-axis of the films is pre- ferentially oriented along the growth direction. The fabricated band pass filters exhibit the center frequency of 865 MHz with 3dB band-width of 45 MHz. From the measured frequency response, the electro-mechanical coupling constant of 0.8% and the SAW velocity of 5,709 m/s are obtained. Thus, we conclude that the sputtered AIN films are feasible for the fabrication of uper UHF band SAW filters.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.6 s.150
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• pp.631-637
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• 2006

This paper presents a numerical method to solve the ship motion coupled with internal fluid flow. Physically the internal fluid motion is coupled with the ship motion. Hitherto the previous numerical results of the coupled motion predict only the general tendency with experiments. The main reason of inaccuracy is that the coupled dynamics of ship motion and internal water motion is not accurately accounted. In this study CFD technique based on VOF is employed for the accurate analysis of flooding water motion. Some cases of the 24th ITTC stability committee's benchmark.study for tanker with internal fluid are analyzed by coupling the ship motion and sloshing dynamics. The calculated ship motion is compared with the experimental result to validate the coupled scheme and is in agreement with the experimental result.

• Journal of Sensor Science and Technology
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• v.5 no.6
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• pp.68-73
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• 1996

ZnO thin films were prepared on glass and (012) sapphire substrates by rf magnetron sputtering. Polycrysralline ZnO films with a (002) orientation were obtained on glass substrates. (110) ZnO films were epitaxially grown on the (012) sapphire substrates. Surface acoustic wave properties were also measured for propagating along the c axis of ZnO film on the glass and sapphire substrates. The phase velocities ($V_{p}$) on glass and sapphire substrate at center frequency were 2680 m/sec and 5980 m/sec and the effective coupling coefficient ($k^{2}$) on the 0th mode were 0.98 % and 1.43 %, respectively.