• New Physics: Sae Mulli
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• v.68 no.11
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• pp.1183-1191
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• 2018

The plasmon behaviors in a superlattice of $GaAs/Al_xGa_{1-x}As$ multiple quantum wells with a half-parabolic confining potential due to different dielectric interfaces are studied under magnetic and electric fields perpendicular and parallel to the superlattice axis by using a previously published theoretical framework. From the density-density correlation functions by considering the intrasubband and the inter-subband transitions under the random phase approximation, we calculate the dispersion energies of the surface and the bulk states as functions of the composition of the multiple quantum well structure and of the magnetic field strength and the average electric field strength over the quantum well. The Raman intensities for various magnetic field strengths and average electric field strengths over the quantum well are also obtained as a function of the energy of the incoming light for these states.

• Journal of the Korean Vacuum Society
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• v.16 no.2
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• pp.134-140
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• 2007

Optical structure of $V_{2}O_{5}$ thin films were analyzed and confirmed, the films were deposited in oxygen partial pressure 0% and 10% by RF magnetron sputtering system. Measurements of the elliptic constants were made in the range of $0.75{\sim}4.0\;eV$ by using phase modulated spectroscopic ellipsometer. The elliptic constants of the thin films were analyze by Double Amorphous dispersion relation. The calculated n, k spectra of $V_{2}O_{5}$ layer were obtained over the range of $0.75{\sim}4.0\;eV$ photon energy. SEM and XRD measurements were also made to validate the ellipsometric analysis and they give good agreement with the structural properties of the films. It was found that optical structure of the $V_{2}O_{5}$ layer has a 3 phase(roughness/film/substrate) and optical absorption properties are greatly depend on the partial pressure of the oxygen.

• Journal of Biomedical Engineering Research
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• v.19 no.5
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• pp.511-518
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• 1998

In order to develop the aerosol bolus technique which is thought to be a potential tool for probing geometries or abnormalities of small airways, an experimental system of measuring fast time variations of particle concentration in the inhaled and exhaled breathing air was developed. The system generates monodisperse sebacic acrid particles of 1 micron size and 1.2 of geometric standard deviation in high concentration of $10^8$ particles/cc, delivers a short pulse of particles at the controlled instant during inhalation using a solenoid valve, and measures the fast change of particle concentration in using the laser light scattering. Successful operation of the generator and the measuring system was confirmed by smooth concentration profiles in inhalation. It was also confirmed that maintaining a constant breathing rate is essential to stable outputs and any disturbance in flow rate near the mode (maximum concentration) induces a large number of spurious peaks in the exhalation. Experimental data without strict control of breathing flow rate showed a substantial amount of scatter. The measured results showed an improvement in scatter over the existing results. When compared with theoretical predictions from 1-D convective diffusion equation and other experiments, general characteristics of dispersion for several penetration depths showed a good agreement, but there exists some difference in absolute values, which is attributed to the difference in body conditions. Improvements are needed in the theory, especially in relation to correcting for the effect of breathing flow rate.

• Journal of Korea Water Resources Association
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• v.43 no.7
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• pp.635-643
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• 2010

A representative unit hydrograph responding to a small basin is used to calculate the flood discharge in the basin. The peak discharge and the time to peak of the unit hydrograph are dealt with its characteristic values. In this study it is shown and analyzed the fluctuations at peak discharges and times to peak of unit hydrographs by rainfall storms in a small national basin $8.5\;km^2$ wide are no small. And on assumption that a major factor in the fluctuations of the unit hydrographs in a small basin be rainfall intensity of a rainstorm, both relations of peak discharge and time to peak with rainfall intensity are suggested as exponential functions respectively. In this result although it is a limit of the study in which its result is accompanied with not small dispersion in the peak values of unit hydrograph due to a defect in used data it is sure an averaging regression relation between peak discharge and time to peak with rainfall intensity as identified in this study has hydrological worth from the complementary viewpoint of the theory of unit hydrograph.

• Journal of Preventive Medicine and Public Health
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• v.7 no.2
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• pp.299-304
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• 1974

The physical status (standing height, body weight, chest girth, sitting height, length of leg, length of thigh, thigh girth, length of crus, length of arm, brachial length, antebrachial girth and skinfold thickness) of 360 healthy middle and high school boys aged between 12 and 17 years in Taegu area was measured and evaluated by means of dispersion. For regression equation and coefficient ofidetermination of each status against standing height were computed. The growth progress of physical status had a tendency to be exponential and, generally, between 13 and 14 years of age the fastest progress was observed. The regression coefficient of body weight against standing height (0.90) was largest and that of skinfold thickness against standing height (0.09) was smallest. In general, the dimension of the regression coefficient was accordant with the dimension of respective physical status. Except in length of thigh and skinfold thickness, coefficient of determination of each physical status against standing height was almost 1 and the regression line could express the relation between standing height and each physical status very satisfactorily. But the regression curve was more desirable for the elucidation of the relation between standing height and skinfold thickness.

• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.3
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• pp.19-30
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• 1990

This note describes an application of Hamiton's principle to nonlinear free-surface flow problems. Two functionals are constructed based on classical Hamilton's principle with a modification due to the presence of a free surface. As an effort towards the development of an efficient numerical scheme for our problem, we present the following three test results: i) The bounding principles of the eigenvalues for the linear dispersion relation. ii) By assuming steady solitary waves, an approximate relation between the amplitudes and the speeds of solitary waves are derived from the two functionals constructed. Their numerical results are compared with those of Longuet-Higgins & Fenton(1974). iii) The shapes and charicteristics of solitary waves are computed from two sets of functionals by varying the number of total finite elements in the fluid domain.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.2
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• pp.167-175
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• 2013

The wave propagation characteristics of an acoustic metamaterial composed of periodically repeated one-dimensional Helmholtz resonator array was investigated considering the effects of dimensional changes of the resonator geometry on the transmission coefficient and band gap. The effective impedance and transmission coefficient of the acoustic metamaterials are obtained based on the acoustic transmission line method. The designed acoustic metamaterials exhibit band gaps and negative bulk modulus that are non-existent properties in the nature. The band gap of the acoustic metamaterial is strongly dependent on the geometry parameters of Helmholtz resonators and lattice spacing. Also, a new type of metamaterial that is periodically constructed with two different resonators was designed to open the local resonance band gap without change of Bragg scattering.

• Steel and Composite Structures
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• v.27 no.1
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• pp.109-122
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• 2018

In This work an analysis of the propagation of waves of functionally graduated plates is presented by using a high order hyperbolic (HSDT) shear deformation theory. This theory has only four variables, which is less than the theory of first order shear deformation (FSDT). Therefore, a shear correction coefficient is not required. Unlike other conventional shear deformation theories, the present work includes a new field of displacement which introduces indeterminate integral variables. The properties of materials are supposed classified in the direction of the thickness according to two simple distributions of a power law in terms of volume fractions of constituents. The governing equations of the wave propagation in the functionally graded plate are derived by employing the Hamilton's principle. The analytical dispersion relation of the functionally graded plate is obtained by solving an eigenvalue problem. The convergence and the validation of the proposed theoretical numerical model are performed to demonstrate the efficacy of the model.

• Journal of the Korean Chemical Society
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• v.41 no.9
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• pp.449-459
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• 1997

The bonded state polarizabilities of ions in the alkali halides are estimated by using the Seitz and Ruffa (SR) energy level analysis relation. The effective number of electrons $(N_{eff})$ in the Slater-Kirkwood formula are used for all members of an isoelectronic sequence. The effective dispersion coefficients $(C_6^{eff})$ are calculated by the use of the empirical formula (J. Chem. Phys. 1991, 95, 1852) estimating $(N_{eff})$ values to reproduce the experimental $(C_6^{eff})$ for atom-atom (or molecule) interactions. In the framework of the T-Rittner model the model potential is constructed and used to calculate the values of dissociation energy and dipole moment. The results obtained in the present study are in good agreement with the experiment one.

• Journal of The Korean Astronomical Society
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• v.28 no.1
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• pp.45-59
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• 1995

In the best observed Pleiades cluster, the luminosity function(LF) and mass function(MF) for main sequence(MS) stars extended to $Mv{\approx}15.5(V{\approx}21)$ are very similar to the initial luminosity function(ILF) and initial mass function(IMF) for field stars in the solar neighborhood showing a bump at log $m{\simeq}-0.05$ and a dip at log $m{\simeq}-0.12$. This dip is equivalent to the Wielen dip appearing in the LF for the field stars. The occurence of these bump and dip is independent of adopted mass-luminosity relation(MLR) . and their characteristics could be explained by a time-dependent bimodal IMF. The model with this IMF gives a total cluster mass of $\~700M_\bigodot,\;\~25$ brown dwarfs and $\~3$ white dwarfs if the upper mass limit of progenitor of white dwarf is greater than $4.5M_\bigodot$. The cluster age on the basis of LF for brightest stars is given by $\~8\times10^7yr$ and all stars in the cluster lie along the single age sequence in the C-M diagram without showing a large dispersion from the sequence.