• Journal of the Korean Vacuum Society
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• v.16 no.4
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• pp.273-278
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• 2007

For the simulation of active region in the quantum cascade lasers (QCL), we solved Schrodinger equation utilizing Runge-Kutta method and Shotting method. Wavelength, phonon resonant energy, and dipole matrix element were simulated with the variation of active region thickness. As a result of such simulation, it was suggested the tolerance range of epi-layer thickness error when 3-quantum well QCL structures are grown.

• Journal of the Korean Geotechnical Society
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• v.18 no.3
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• pp.13-21
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• 2002

An extensive tension experiment was carried out to examine the variation of tensile strength in moist sand having moisture contents in the range of 0.5% < w < 4.0% with newly developed direct tension apparatus. It was observed that tensile strength of sand varied as functions of moisture content, relative density, presence of fines, and level of precompression. Tensile strength increases with increasing moisture content and fines, and this trend is more noticeable at increasing relative densities. However, the influences of relative density and fines on the tensile strength are substantially dependent on the water content. These effects are reduced at low moisture levels (w < 0.5%). The precompression effects also depend on the water content but less on the duration and level of the precompression.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.10
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• pp.998-1004
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• 2002

This paper reports a design of feedforward linear power amplifier using pilot tone for IMT-2000 band repeaters accepting multi-carrier. As this time pilot tone is applied to the circuit differently from the existing method. Only one pilot tone is used in both 1-st loop(IMD abstraction loop) and 2-nd loop(IMD cancellation loop) to cancell IMD signals automatically according to variation of frequency or power level of input signals. As an experiment, in range of 2110 MHz - 2170 MHz at LPA output power of $20 W_{avg}$, IMD characteristics of over 20 dB was improved maintaining below -60 dBc considering respective 20 MHz. Therefore the supposed feedforward linear power amplifier can be used for linear power amplifier in IMT-2000 band repeaters.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1459-1461
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• 1997

The microwave dielectric ceramic properties of $CaTiO_3-(Li_{1/2}Nd_{1/2})TiO_3$ were investigated. The solid solution of $CaTiO_3-(Li_{1/2}Nd_{1/2})TiO_3$ had the perovskite structure in the range of all composition. The dielectric constant and temperature coefficient of resonant frequency of solid solution were decreased with the contend of $(Li_{1/2}Nd_{1/2})TiO_3$, whereas, the $Q{\times}f$ value was increased. In the $(1-X)CaTiO_3-X(Li_{1/2}Nd_{1/2})TiO_3$ system, the microwave properties could be controlled by the variation of X, X is weight fraction. Typical value of K=119, $Q{\times}f=2970$ and $TCF=14ppm/^{\circ}C$ were obtained for $0.2CaTiO_3-0.8(Li_{1/2}Nd_{1/2})TiO_3$.

• Geomechanics and Engineering
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• v.1 no.3
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• pp.205-218
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• 2009

The bearing capacity factor $N_{\gamma}$ is computed for a rough conical footing placed over horizontal ground surface. The axisymmetric lower bound limit analysis formulation, in combination with finite elements and linear programming, proposed recently by the authors is used in this study. The variation of $N_{\gamma}$ with cone apex angle (${\beta}$), in a range of $30^{\circ}-180^{\circ}$, is obtained for different values of ${\phi}$; where ${\phi}$ is soil friction angle. For ${\phi}&lt;30^{\circ}$, the magnitude of $N_{\gamma}$ is found to decrease continuously with an increase in ${\beta}$ from $30^{\circ}$ to $180^{\circ}$. On the other hand, for ${\phi}&gt;30^{\circ}$, the minimum magnitude of $N_{\gamma}$ is found to occur generally between ${\beta}=120^{\circ}$ and ${\beta}=150^{\circ}$. In all the cases, it is noticed that the magnitude of $N_{\gamma}$ becomes maximum for ${\beta}=30^{\circ}$. For a given diameter of the cone, the area of the plastic zone reduces generally with an increase in ${\beta}$. The obtained values of $N_{\gamma}$ are found to compare quite well with those available in literature.

• 한국태양에너지학회:학술대회논문집
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• 2011.04a
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• pp.195-198
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• 2011

Liquid desiccant material, such as lithium chloride (LiCl) or halide slits are usually used on air conditioning application for controlling the humidity of high Outdoor Air (OA). Solar energy is usually used to heat the liquid in regeneration process of those desiccant. The mass transfer it self is driven by the temperature different between the liquid desiccant and the input air. This experiment study is analyzing the characteristic of the aqueous LiCl-air temperature different in variance specific gravity, especially in range of temperature different using the solar energy as the heat generator. The experiment has done by variating the concentration of the LiCl with specific gravity 1.210 and 1.150. For the comparison the pure water is also used. The result show that the mass transfer rate is increased in every variation as the increases of the temperature different, and the weeker aqueous solution of the LiCl the highest mass transfer coefficient.

• The Journal of the Acoustical Society of Korea
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• v.22 no.4E
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• pp.167-175
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• 2003

Shear wave velocity was measured and grain size analysis was conducted on two core samples obtained in unconsolidated marine sediments of the western continental margin, the East Sea. A pulse transmission technique based on the Hamilton frame was used to measure shear wave velocity. Duomorph ceramic bender transducer-receiver elements were used to generate and detect shear waves in sediment samples. Time delay was calculated by changing the sample length from the transducer-receiver element. Time delay is 43.18 μs and shear wave velocity (22.49 m/s) is calculated from the slope of regression line. Shear wave velocities of station 1 and 2 range from 8.9 to 19.0 m/s and from 8.8 to 22 mis, respectively. Shear wave velocities with depth in both cores are qualitatively in agreement with the compared model〔1〕, although the absolute value is different. The sediment type of two core samples is mud (mean grain size, 8-9Φ). Shear wave velocity generally increases with sediment depth, which is suggesting normally consolidated sediments. The complicated variation of velocity anisotropy with depth at station 2 is probably responsible for sediment disturbance by possible gas effect.

• Solar Energy
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• v.5 no.2
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• pp.77-83
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• 1985

An analysis is performed to investigate the influence of the buoyancy force and the thickness variation of melting layer in the containment that is filled with phase-change Material surrounding a cylindrical heating tube during melting process. The phase-change material is assumed to be initially solid at its phase-change temperature and the remaining solid at any given time is still at the phase-change temperature and neglecting the effect of heat transfer occuring within the solid. At the start of melting process, the thickness of melting layer is assumed to be a stefan-problem and after the starting process, the change of temperature and velocity is calculated using a two dimensional finite difference method. The governing equations for velocity and temperature are solved by a finite difference method which used SIMPLE (Semi Implicit Method Pressure linked Equations) algorithm. Results are presented for a wide range of Granshof number and in accordance with the time increment and it is founded that two dimensional fluid flow occurred by natural convection decreases the velocity of melting process at the bottom of container. The larger the radius of heating tube, the higher heat transfer is occurred in the melting layer.

• Journal of the Korean Ceramic Society
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• v.18 no.3
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• pp.171-181
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• 1981

Alkaline-earth porcelains have been prepared from mixture of kaolin, quartz, and synthetic calcines obtained by calcining a mixture of kaolin and more than two different kinds of alkaline-earth carbonates. They were magnesium, calcium and barium carbonates which are inexpensive and readily available. The vitrification behavior of the batch mixes was investigated in the firing range of 1240$^{\circ}$to 1380$^{\circ}$, in relation to the body compositions. It appeared that the density and the firing temperature depended largely on the content of alkaline-earth oxides in the body. These porcelains posses excellant dielectric properties, and are especially valuable as bases for deposited carbon resistors for which they were developed. An illustrative composition is 50% Dong Hwa kaolin, 22.4% Chang Shin quartz, 27.6% calcine. The composition of the calcine is 70% Dong Hwa kaolin, 10.7% BaCO3, 13.5% CaCO3, 5.8% MgCO3. The specific resistance of this body is $1.2{\times}10^{15}$ ohm-cm at 5$0^{\circ}C$, $2.5{\times}10^{14}$ ohm-cm 10$0^{\circ}C$, $2.5{\times}10^{13}$ ohm-cm at 15$0^{\circ}C$, $1.8{\times}10^{12}$ohm-cm at 20$0^{\circ}C$.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1682-1686
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• 2004

A slit-flow apparatus with laser diffraction method has been developed with significant advances in ektacytometry design, operation and data analysis. In the slit-flow ektacytometry (or laser-diffractometry), the deformation of red blood cells subjected to continuously decreasing shear stress in slit flow is measured. A laser beam traverses a diluted blood suspension flowing through a slit and is diffracted by RBCs in the volume. The diffraction patterns are captured by a CCD-video camera, linked to a frame grabber integrated with a computer, while the differential pressure variation is measured by a pressure transducer. Both measurements of laser-diffraction image and pressure with respect to time enable to determine deformation index and the shear stress. The range of shear stress of 0 ${\sim}$ 35 Pa and measuring time is less than 2 min. When deforming under decreasing shear stress, RBCs change gradually from the prolate ellipsoid towards a circular biconcave morphology. The Deformation Index (DI) as a measure of RBC deformability is determined from an isointensity curve in the diffraction pattern using an ellipse-fitting program. The advantages of this design are simplicity, i.e., ease of operation and no moving parts, low cost, short operating time, and the disposable kit which is contacted with blood sample.