• Journal of the Korean Society of Visualization
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• v.22 no.2
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• pp.35-43
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• 2024

Microparticle separation has demonstrated significant potential for biological, chemical, and medical applications. We introduce a surface acoustic wave (SAW)-based microfluidic device for separation of elastic and rigid microspheres based on their property and size. By tuning the SAWs to match the resonant frequencies of certain microspheres, those particles could be selectively separated from the other microspheres. When microspheres are exposed to an acoustic field, they experience the SAW-induced acoustic radiation force (ARF), whose magnitude is dependent on the microparticle size and properties. We modeled the SAW-induced ARF based on elastic sphere theory and conducted a series of experiments to separate elastic and rigid microspheres. We further utilized the acoustofluidic method for the separation of Thalassiosira Eccentrica microalgae based on the differences in their sizes with purity exceeding 90%. We anticipate that our technique will open up new possibilities for sample preparation, detection, and diagnosis in various emerging biological and medical analyses.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.2
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• pp.114-125
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• 2009

Effect of a finite square substrate plane on the radiation characteristics of a microstrip patch antenna is investigated. Effect of a finite square substrate plane on the resonance frequency and bandwidth is very small, while that on the radiation pattern is very large. The gain of front radiation and the direction of the maximum gain vary almost periodically with the length of a square substrate plane. The length of a square substrate plane for the maximum gam and the minimum gain of front radiation decrease as the electrical thickness of a substrate increases. The variation of the gain of front radiation with the length of a square substrate plane increases as the electrical thickness of a substrate increases. The variation of the radiation pattern with the length of a square substrate plane is almost determined by the electrical thickness of a substrate.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.4
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• pp.43-52
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• 2008

Radiation characteristics of microstrip patch antennas integrated with mushroom-like EBG structures in length direction, width direction and all directions are analyzed. Patch antennas integrated with EBG structures in length direction shows the best radiation characteristics among the cases integrated in three directions. The case for the feed point of a patch antenna located in the center of both EBG structures integrated with a patch antenna shows better symmetric E-plane radiation pattern, higher forward radiation intensity, and lower backward radiation intensity compared to the case for the center of a patch antenna located in the center of both EBG structures. The variation of the radiation characteristics of patch antennas integrated with EBG structures more than 4 periods versus number of periods of EBG structures integrated is very small.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.6
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• pp.350-362
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• 2017

The Eulerian nearshore current model is more advantageous than the Lagrangian model in the way that numerical results from the Eulerian model can be directly compared with the measurements by the stationary equipment. It is because the wave mass flux is not included in the computed mass flux of Euleran nearshore current model. In addition, the Eulerian model can simulate the longshore currents with depth varying parabolic profile. However, the numerical models proposed by different researcher have different forms of the wave stress terms. For example, wave stresses in Newberger and Allen's (2007) model is constant over the depth, while those of Chun (2012) are vertically distributed. In the present study, these wave stress terms were compared against Hamilton et al.'s (2001) laboratory experiments to see the effects of different wave stress terms performed on the computation of nearshore currents.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.1
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• pp.79-90
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• 2009

This paper presents the development of dynamically combined Typhoon generated surge-tide-wave numerical model which is applicable from deep to shallow water. The dynamically coupled model consists of hydrodynamic module and wind wave module. The hydrodynamic module is modified from POM and wind wave module is modified from WAM to be applicable from deep to shallow water. Hydrodynamic module computes tidal currents, sea surface elevations and storm surges and provide these information to wind wave module. Wind wave mudule computes wind waves and provides computed information such as radiation stress, sea surface roughness and shear stress due to winds. The newly developed model was applied to compute the surge, tide and wave fields by typhoon Maemi. Verification of model performance was made by comparison of measured waves and tide data with simulated results.

• Journal of Astronomy and Space Sciences
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• v.39 no.1
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• pp.11-22
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• 2022

It is suggested that magnetosonic waves (also known as equatorial noise) can scatter radiation belt electrons in the Earth's magnetosphere. Therefore, it is important to understand the global distribution of these waves between the proton cyclotron frequency and the lower hybrid resonance frequency. In this study, we developed an empirical model for estimating the global distribution of magnetosonic wave amplitudes and wave normal angles. The model is based on the entire mission period (approximately 2012-2019) of observations of Van Allen Probes A and B as a function of the distance from the Earth (denoted by L^*), magnetic local time (MLT), magnetic latitude (λ), and geomagnetic activity (denoted by the Kp index). In previous studies the wave distribution inside and outside the plasmasphere were separately investigated and modeled. Our model, on the other hand, identifies the wave distribution along with the ambient plasma environment-defined by the ratio of the plasma frequency (f_pe) to the electron cyclotron frequency (f_ce)-without separately determining the wave distribution according to the plasmapause location. The model results show that, as Kp increases, the dayside wave amplitude in the equatorial region intensifies. It thereby propagates the intense region towards the wider MLT and inward to L^* < 4. In contrast, the f_pe/f_ce ratio decreases with increasing Kp for all regions. Nevertheless, the decreasing aspect differs between regions above and below L^* = 4. This finding implies that the particle energy and pitch angle that magnetosonic waves can effectively scatter vary depending on the locations and geomagnetic activity. Our model agrees with the statistically observed wave distribution and ambient plasma environment with a coefficient of determination of > 0.9. The model is valid in all MLTs, 2 ≤ L^* < 6, |λ| < 20°, and Kp ≤ 6.

• The Journal of the Korea Contents Association
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• v.10 no.5
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• pp.343-350
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• 2010

We measured the radiation exposure for 55 persons (male: 36, female: 19) who was diagnosed with kidney and ureter stones and received ESWL. The absorbed dose was measured at the organ which is expected to absorb relatively much radiation (kidney, bladder, liver). The radiation dose measurement voltage 80kVp, current of 5mA as a fixed model of the human body by using the Rando phantom with Radiophotoluminescent Glass Dosimeter. Absorbed dose was measured for two times (5 minute and 10 minute, each) and converted to effective dose. Mean number of treatment was 1.8 times (1~4) per patient was the mean time of radiation exposure533 seconds (248-2516). For the treatment of right renal stone, the effective dose of right kidney, left kidney, liver and bladder was 2.458mSv, 0.152mSv, 1.404 mSv and 0.019mSv, respectively. For the treatment of left renal stone, the effective dose of right kidney, left kidney, liver and bladder was 2.496mSv, 0.252mSv, 0.178 mSv, and 0.017mSv, respectively. For the treatment of distal ureter stone, the effective dose of right kidney, left kidney and bladder was 0.009mSv, 0.01mSv and 3.742mSv, respectively.

• Journal of the Korea Knowledge Information Technology Society
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• v.12 no.4
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• pp.539-550
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• 2017

In this paper, we designed, fabricated and tested an UHF band cylindrical dipole array antenna. In the proposed antenna, cylindrical dipoles were vertically arranged in four stages. A parallel structure feeding circuit was installed inside the cylindrical dipole and mounted so as to be broadband matching. The feeding circuit was installed at the center of the cylindrical dipole to optimize the gain flatness characteristic of the azimuth direction omnidirectional radiation pattern. Minimizing the difference between the signals branched from the feeding circuit and realizing the symmetry of the radiation pattern. The required specifications are more than 11.2% bandwidth in UHF band, above 6dBi antenna gain, standing wave ratio of 2:1 or less, less than ${\pm}1dB$ gain flatness in azimuth radiation pattern, more than 13 degrees in elevation radiation pattern of 3dB beamwidth. We confirmed the possibility of implementation through M&S and verified the result of M&S through production and testing. The test results are 11.2% bandwidth in the UHF band, 6.30 to 8.31 dBi gain, 1.53:1 standing wave ratio or less, within ${\pm}0.2dB$ gain flatness in the azimuth radiation pattern, elevation radiation pattern of 3dB beam width was 15.62 to 15.84 degrees. The test result meets all requirements specifications.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.677-680
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• 2008

The paper deals with the analysis of radiation characteristics of antenna in the multi-layered media structures. The dyadic Green's function for three layer medium is complex because the Green's functions belonging to the kernel of the integral equation are expressed as Sommerfeld integrals, in which surface wave effects are automatically included. When certain condition are met, the integral can be evaluated approximated by the method of Saddle-point integration. In this study, we propose a method to calculate a radiation pattern for several antennas by using the method of Saddle-point integration. Numerical results show how the radiation characteristics are affected by parameter of dielectric media.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.6
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• pp.658-662
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• 2001

The classification of surface flaw types was performed on the basis of angular dependence of backscattered ultrasound. The copper line adhered on the surface, cower line filled in groove, pure groove and the normal edge were adopted as various surface flaw patterns of glass specimen. A backward longitudinal profile was formed probably by the longitudinal wane scattering at and near 1st critical angle. The wave trains at the peak angles of the backward radiation profiles showed different shapes according to the superposition ratio of scattered and leaky waves. The asymmetry of the backward radiation profile arose due to the scattering effect of flaw. The additive resonance effect of copper line appeared in the left side of the profile. The peak angles of both the longitudinal and radiation profiles were shifted toward small angle by the scattering effect.