• Proceedings of the KIEE Conference
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• 1992.07a
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• pp.501-502
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• 1992

This paper deals with the experiment of CW YAG laser for processing. The YAG laser is spotted very small size beam compared with $CO_2$ laser having short wave-length. That is used broadly in material processing because of easy reaction to the materials, and the maintenance is very simple. The power delivery and focussing is done conventional optical components, and splitting beam is used many point stop-welding. In these studies, especial interest is nesessary to perpare for future technology. Our study aims to develop the YAG laser system and to accumulate design and construction technology. In basic experiments, we obtain the maximum output power of 50 W with the single elliptical cylinder.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.21-24
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• 2008

The present study numerically investigates the glottal airflow characteristics as well as acoustic features of phonation fully coupled with dynamic behavior of vocal folds. The vocal folds are described by a low-dimensional body-covered model characterized by bio-mechanical parameters such as glottal width, vocal folds stiffness, and subglottal pressure. The flow in the vocal tract is modeled as an incompressible, axisymmetric form of the Navier-Stokes equations (INS), while the acoustic field is predicted by the linearized perturbed compressible equations (LPCE). The computed result shows that a two-mass model of vocal folds is sufficient to reproduce temporal variations in oral airflow and glottis motion produced by female speakers. It is also found that i) the glottal width has a significant effect on the amplitude of glottal flow, and thus on the amplitude of acoustic wave in the vocal tract, ii) the vocal fold tension is the main control parameter for the fundamental frequency of phonation, iii) the subglottal pressure plays an appreciable role on reproduction of the self-sustained oscillation of vocal folds, and iv) the strength of pulsating airflow and vortical structures are primarily affected by glottal width and subglottal pressure, and are closely related to pitch, loudness, and voice quality. Finally, more comprehensive explanation about the difference between one- and two-mass models is presented with discussion of effectiveness of vocal folds oscillation and voice quality.

• Journal of Advanced Navigation Technology
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• v.22 no.5
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• pp.359-366
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• 2018

In this paper, the noise is removed by using CTLS aircraft installed FBG sensor inside the aircraft wing. We suggest a normal wavelet transform scheme with motion - invariant characteristics for noise reduction. In the case of installing FBG sensors inside the composite material as in CTLS, large and small empty spaces and parts or sections are generated between the adhesive layers, and a signal splitting problem occurs. FBG sensor is not affected by noise. but eletromagnetic, light source, light detector and signal processing device are influeced by noise because these are eletronic components what affected by eletromagnetic wave. because of this, errors are occured. Experimental results show that the noise can be removed using normal wavelet transform and more accurate data detection is possible.

• Journal of computational fluids engineering
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• v.19 no.3
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• pp.91-97
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• 2014

A high resolution numerical method aimed at solving cavitating flow was proposed and applied to gas-liquid two-phase shock tube problem with arbitrary void fraction. The present method with compressibility effects employs a finite-difference 4th-order Runge-Kutta method and Roe's flux difference splitting approximation with the MUSCL TVD scheme. The Jacobian matrix from the inviscid flux of constitute equation is diagonalized analytically and the speed of sound for the two-phase media is derived by eigenvalues. So that the present method is appropriate for the extension of high order upwind schemes based on the characteristic theory. By this method, a Riemann problem for Euler equations of one dimensional shock tube was computed. Numerical results of high speed flow phenomena such as detailed observations of shock and expansion wave propagations through the gas-liquid two-phase media and some data related to computational efficiency are made. Comparisons of predicted results and solutions at isothermal condition are provided and discussed.

• Korean Journal of Optics and Photonics
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• v.14 no.4
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• pp.392-398
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• 2003

We present a novel concept of a phase-shifting diffraction-grating interferometer, which is intended for the optical testing of concave mirrors with high precision. The interferometer is configured with a single reflective diffraction grating, which performs multiple functions of beam splitting, beam recombination, and phase shifting. The reference and test wave fronts are generated by means of reflective diffraction at the focal plane of a microscope objective with large numerical aperture, which allows testing fast mirrors with low f-numbers. The fiber-optic confocal design is adopted for the microscope objective to focus a converging beam on the diffractive grating, which greatly reduces the alignment error between the focusing optics and the diffraction grating. Translating the grating provides phase shifting, which allows measurement of the figure errors of the test mirror to nanometer accuracy.

• Journal of the Korean Magnetics Society
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• v.1 no.1
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• pp.1-5
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• 1991

The magnetic properties of the polycrystalline ${(Fe_{2}O_{3})}_{1-x-y}{(In_{2}O_{3})}_{x}{(Eu_{2}O_{3})}_{y}$(x=0.01, y=0.02과 x=0.02, y=0.03) have been studied by the methods of X-ray diffraction, $M\"{o}ssbauer$ effect, and magnetic hysteresis measurement. The X-ray diffraction patterns show that the samples have a same crystal structure as $\alpha-Fe_{2}O_{3}$. From the analysis of the temperature dependence of the quadrupole splitting and average half-width, it is found that the Morin transition occurs in the sample of x=0.01 and y=0.02 and the spin angle defined as the angle between the [111] crystal axis and antiferromagnetic vector, changes from about $35^{\circ}$ to the (111) plane as increasing the temperature in the sample of x=0.02 and y=O.03. The temperature dependence of magnetic hyperfine field is analyzed by using the spin-wave theory. The isomer shift values at room temperature are found to be given by about 0.35mm/s for the samples which means that the Fe ions belong to $3^{+}ion$. The temperature dependence of isomer shift was analyzed by using the Debye model.

• The KIPS Transactions:PartC
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• v.9C no.3
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• pp.439-444
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• 2002

In this paper, we present both the link budget analysis according to system parameters and the cell coverage according to transmitter power and modulation scheme of digital MMDS among the wireless CATV system methods which is bated on the wireless internet service. Also, in this paper, we present C/I and number of subscriber according to splitting cell. In this paper, the cell coverage of which obtain the results according to both transmitter power from 0dBW to -9dBW and modulation scheme of QPSK, 16QAM and 64QAM based on link budget was analysis for system parameter of digital MMDS was able to provide from maximum 134km to minimum 4.3km. Also, in this paper, the number of subscriber of which obtain the results according to polarization wave, frequency of frequency reuse and C/I in 4. 6 and 8 sectors was able to provide from maximum 5,200DSI to minimum 1,300DSI.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.5
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• pp.1145-1158
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• 1994

A three-dimensional, finite difference, numerical model with free surface was developed on ${\sigma}$-coordinate. A semi-implicit numerical scheme in time has been adopted for computational efficiency. The scheme is essentially independent of the stringent stability criteria (CFL condition) for explicit schemes of external surface gravity wave. Implicit algorithm was applied for vertical shear stress, Coriolis force and pressure gradient terms. The reliability of the model with vertically variable grid system was checked by the comparison of simulation results with analytic solution of wind-driven currents in a one-dimensional channel. Sensitivity analysis of differencing parameters was carried out by applying the model to the calculation of wind-driven currents in a square lake.

• Journal of the Korean Magnetics Society
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• v.9 no.1
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• pp.7-16
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• 1999

Stoichiometric and nonstoichiometric $Y_{3-x}Fe_{5+x}O_{12})$ polycrystalline samples (x=0.00, 0.05, 0.10, 0.30, -0.05, -0.10, -0.30) were prepared by solid state reaction method. The magnetic properties of the sample were investigated by FMR (ferromagnetic resonance) technique at microwave frequency 5.11 GHz (G-band) and 23.39 GHz (K-band) respectively. The spectroscopic splitting factor g were estimated to be 2.04~2.35 from the derivative absorption lines. As the samples became yttrium $(Y^{3+})$ excess and iron $(Fe^{3+})$ excess, Magnetizations were decreased. But resonance linewidth were increased. To investigate the anisotropy, the angular dependence of resonance magnetic fields were measured. Angular dependence of effective magnetizations were measured by FMR from 77 K to 300 K at K-band microwave frequency (23.39 GHz) and the saturation magnetizations were measured by VSM. The Bloch coefficients B and C were determined by fitting. $M_{eff}(0)$ was obtained by the extrapolation from 80 K. From this result, the spin wave stiffness constant D $(about\; 162~206 \;eV{\AA}^2)$and average square range of exchange interaction $$$(about \;5.84~12.13\;{\AA}^2)$ were determined.

• Proceedings of the KSRS Conference
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• v.2
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• pp.827-830
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• 2006

The tsunami from the megathrust earthquake magnitude 9.3 on 26 December 2004 is the largest tsunami the world has known in over forty years. This tsunami destructively attacked 13 countries around Indian Ocean with at least 230,000 fatalities, displaced people 2,089,883 and 1.5 million people who lost their livelihoods. The ratio of women and children killed to men is 3 to 1. The total damage costs US$ 10.73 billion and rebuilding costs US$ 10.375 billion. The tsunami's death toll could have been drastically reduced, if the warning was disseminated quickly and effectively to the coastal dwellers along the Indian Ocean rim. With a warning system in Indian Ocean similar to that operating in the Pacific Ocean since 1965, it would have been possible to warn, evacuate and save countless lives. The best tribute we can pay to all who perished or suffered in this disaster is to heed its powerful lessons. UNESCO/IOC have put their tremendous effort on better disaster preparedness, functional early warning systems and realistic arrangements to cope with tsunami disaster. They organized ICG/IOTWS (Indian Ocean Tsunami Warning System) and the third of this meeting is held in Bali, Indonesia during $31^{st}$ July to $4^{th}$ August 2006. A US$ 53 million interim warning system using tidal gauges and undersea sensors is nearing completion in the Indian Ocean with the assistance from IOC. The tsunami warning depends strictly on an early detection of a tsunami (wave) perturbation in the ocean itself. It does not and cannot depend on seismological information alone. In the case of 26 December 2004 tsunami when the NOAA/PMEL DART (Deep-ocean Assessment and Reporting of Tsunami) system has not been deployed, the initialized input of sea surface perturbation for the MOST (Method Of Splitting Tsunami) model was from the tsunamigenic-earthquake source model. It is the first time that the satellite altimeters can detect the signal of tsunami wave in the Bay of Bengal and was used to validate the output from the MOST model in the deep ocean. In the case of Thailand, the inundation part of the MOST model was run from Sumatra 2004 for inundation mapping purposes. The medium and high resolution satellite data were used to assess the degree of the damage from Indian Ocean tsunami of 2004 with NDVI classification at 6 provinces on the Andaman seacoast of Thailand. With the tide-gauge station data, run-up surveys, bathymetry and coastal topography data and land-use classification from satellite imageries, we can use these information for coastal zone management on evacuation plan and construction code.