• Journal of Korean Society for Atmospheric Environment
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• v.2 no.2
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• pp.19-30
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• 1986

This study was performed to develop a long-term air pollution dispersion model based on CDM program for use in the personal computer. The model CDM.PC, developmented for use of this study, simplified the plum equation of point pollution source in a windy state and sindless state. We used the classified 8 class stability, 16 wind direction and 4 class wind speed for the computer input climatological data. The plum rise equation is applied for CONCAWE's equation above 2,000 Kcal/sec of the exhaust calorie and Moses-Carson's equation below 2,000Kcal/sec at windy state, and Brigg's equation at calm. The time required is 200 minutes for drawing the air pollution contour for treating ten stacks under the above-stated conditions. It is the weakness of using personal computer that the operation time is longer than a large-size computer. But it strength is that the personal computer is used widely. To compare the treatment results of CDM.PC with TCM, we comfirmed that the shape of $SO_2$ pollution contour is similar but the concentration distribution is quite different because of characteristics of each models. Estimated and measured $SO_2$ concentration were similar, namely, Cest/Cob ratio of CDM.PC and TCM were respectively $0.96 \pm 0.25 (mean\pmS.D)$ and $1.08\pm0.26$.

• Current Optics and Photonics
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• v.5 no.3
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• pp.322-328
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• 2021

In this paper, a pretreatment method for a matrix in convex optimization is proposed to optimize the spectral reconstruction process of a disordered dispersion spectrometer. Unlike the reconstruction process of traditional spectrometers using Fourier transforms, the reconstruction process of disordered dispersion spectrometers involves solving a large-scale matrix equation. However, since the matrices in the matrix equation are obtained through measurement, they contain uncertainties due to out of band signals, background noise, rounding errors, temperature variations and so on. It is difficult to solve such a matrix equation by using ordinary nonstationary iterative methods, owing to instability problems. Although the smoothing Tikhonov regularization approach has the ability to approximatively solve the matrix equation and reconstruct most simple spectral shapes, it still suffers the limitations of reconstructing complex and irregular spectral shapes that are commonly used to distinguish different elements of detected targets with mixed substances by characteristic spectral peaks. Therefore, we propose a special pretreatment method for a matrix in convex optimization, which has been proved to be useful for reducing the condition number of matrices in the equation. In comparison with the reconstructed spectra gotten by the previous ordinary iterative method, the spectra obtained by the pretreatment method show obvious accuracy.

• Journal of Korean Society for Atmospheric Environment
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• v.16 no.3
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• pp.237-246
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• 2000

An experimental study has been carried out using a rotating water channel in order to investigate the effect of surface roughness on the vertical dispersion of plume within boundary layer. Dispersion measurements of tracers released from two sources with different height at neutral conditions over various rough terrain ranging from rural to urban have been performed. Various values of roughness length were simulated by combining of 4 stream velocities and 3 roughness element conditions. Dispersion measurements have also been made for rough terrain where high buildings are locally concentrated. Values of $\sigma$z increase with roughness and this tendency appears to apply both cases of with and without locally concentrated high buildings. The comparisons of the Bowne's nomogram on $\sigma$2 vs x relationship and the measurements of $\sigma$2 with roughness show good accordance in $\sigma$2 distribution at stability D class over rural, suburban and urban terrain. For constant roughness length the $\sigma$2 values of plumes from lower source height are smaller than those of plumes from higher source at short downwind distance, but this relationship becomes reverse as distance increases. Crossing appears to be made before about 2km. The value of constant I in McMullen's equation $\sigma$2=exp [I+J(In x) + K(In x)2] appears to increase with roughness length, however, the relationships between other constants and roughness have been confirmed. The values of $\sigma$2 for various downwind distances, estimated by using an equation which is employed in ISC (Industrial Source Complex) dispersion model for areas where high buildings are locally assembled, are in accordance with measurements from water channel experiments.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.16 no.2
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• pp.57-63
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• 2004

Wave lengths of tsunamis are shorter than those of tides, and the dispersion effect of tsunamis is relatively strong. Thus, it should be properly considered in the numerical simulation of distant tsunami propagation for better accuracy. In the present study an active dispersion-correction scheme using explicit scheme is developed to take into account the dispersion effect in the simulation of tsunami propagation using one-dimensional finite element method based on wave equation. The validity of the dispersion-correction scheme proposed in this study is confirmed through the comparision of numerical solutions calculated using the present scheme with analytical ones considering dispersion effect of waves.

• Journal of the Korea Society for Simulation
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• v.28 no.3
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• pp.83-89
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• 2019

This research describes quantitative effects of initial dispersion conditions upon the dispersion randomness of Magnus rotor bomblets. Ratios of the missile spin rate to the missile velocity, a, flight path angles, ${\gamma}$ and altitudes, h, were changed to investigate their effects on dispersion randomness. Dispersion was analyzed through calculation of 6 degree of freedom motion equation with aerodynamic coefficients from wind tunnel experiments. In order to analyze the randomness, regression analysis is adopted to calculate the coefficient of determination. The optimized ratio of the missile spin rate to the missile velocity and flight path angle were obtained and the dispersion altitudes had more effect on the dispersion diameter and had less effect on dispersion than other parameters.

• Journal of Distribution Science
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• v.20 no.4
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• pp.111-119
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• 2022

Purpose: This study seeks to address the omission through examining the manner in which demographic similarity affects the responses of employees in the retail sector towards horizontal pay dispersion. Through doing so the study will be effective in bolstering the recent efforts of more careful exploration of conditions. Research design, data, and methodology: Scant past studies are available to guide for practitioners in retail sector which compensation strategy might lead adequate job performance for retail sales workers. To suggest possible solution, the present authors used variables of pay dispersion and obtained 317 US retail sale workers in distribution channels to measure the association between pay dispersion and employee job performance. Results: The statistical findings indicated both first and second hypothesis could be acceptable with favorable Beta and T values, resulting high degree of pay dispersion leads a low level of job performance, while a low degree of pay dispersion can motivate retail sales workers to improve their performance. Conclusions: The findings of this study raises an argument that processes of social comparison work in a more vigorous manner. This is thus a representation of the propensity of a retail sales worker to voluntarily resign from an organization when dispersion rates are higher.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.697-698
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• 2002

The dispersion of an aerosol bolus in acinus is analyzed numerically. Model geometry is a straight duct surrounded by an axisymmetric semicircular annulus which is expanding or contracting with breathing. Unsteady Wavier-Stokes equation is solved by CFX-F3D, an FVM commercial code and the trajectory of massless particle Is computed by Lagrangian method. For steady flow with no wall motion, mean velocity of aerosol bolus in alveolated duct is a little smaller than that in straight duct and dispersion in alveolated duct is comparable with the dispersion in straight tube. For expanding duct mean velocity of aerosol bolus approaches half of that in straight tube and effective diffusivity is smaller than that of straight tube. For contracting duct mean velocity of aerosol bolus becomes slightly larger than that in straight tube and effective diffusivity is comparable with the case of straight tube.

• Journal of the Optical Society of Korea
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• v.14 no.4
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• pp.351-356
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• 2010

We investigated the combined effect of fiber chromatic dispersion and self-phase modulation (SPM) in multi-channel subcarrier multiplexed (SCM) optical transmission systems. We theoretically analyzed the transmission characteristics of the SCM signals with the effect of SPM and chromatic dispersion in a single-mode optical fiber by numerical simulations based on the nonlinear Schrodinger equation. The numerical simulation results revealed that the effect of fiber dispersion and SPM could occur independently between subcarrier channels in two-channel SCM systems for small optical modulation index (OMI) and large channel spacing. However, for large OMI, small channel spacing, and large fiber launching power, we found a performance degradation of the two-channel system compared to that of a single-channel system. These parameters are therefore important for the optimization of multi-channel SCM systems applicable to radio over fiber networks.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.899-904
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• 2003

A new model for dense gas dispersion is formulated within the Lagrangian framework. In several accidental released situations, denser-than-air vapour clouds are formed which exhibit dispersion behavior markedly different from that observed for passive atmospheric pollutants. For relevant prediction of dense gas dispersion, the gravity and entrainment effects need to implemented. The model deals with negative buoyancy which is affected by gravity. Also, the model is subjected to entrainment. The mean downward motion of each particle was accounted for by considering the Langevin equation with buoyancy correction term.

• Proceedings of the Korea Water Resources Association Conference
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• 1993.07a
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• pp.151-157
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• 1993