• Geophysics and Geophysical Exploration
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• v.13 no.4
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• pp.330-335
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• 2010

In order to estimate the confidence level of the velocity distribution shown in a velocity image reconstructed from a travel-time tomography, the ray coverage and the inversion characteristics of the system matrix were investigated. The targets of the analysis is the first arrival travel-time, the raypath information, and the resulting velocity model. The ray coverage, degree of ray and model coupling, was estimated by the number of rays and total ray length in a velocity grid, and information regarding the resolution and uncertainties involved in the reconstructed velocity model was derived from the results of the SVD analysis of the system matrix that relates the data space (first arrival travel times) to the model space (velocity distribution in tomogram).

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.548-554
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• 2000

The aim of this paper is to understand the time averaged pressure distributions in a high-speed centrifugal compressor channel diffuser at design and off-design flow rates. Pressure distributions from the impeller exit to the channel diffuser exit are measured and discussed far various flow rates from choke to near surge condition, and the effect of operating condition is discussed. The strong non-uniformity in the pressure distribution is obtained over the vaneless space and semi-vaneless space caused by the impeller-diffuser interaction. As the flow rate increases, flow separation near the throat, due to large incidence angle at the vane leading edge, increases aerodynamic blockage and reduces the aerodynamic flow area downstream. Thus the minimum pressure location occurs downstream of the geometric throat, and it is named as the aerodynamic throat. And at choke condition, normal shock occurs downstream of this aerodynamic throat. The variation in the location of the aerodynamic throat is discussed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.140-141
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• 2022

CFD analysis was performed to analyze the temperature distribution of the inner space of the curing house according to blocking the opening of the gang-form with a tent in case of concrete pouring and heat curing of the apartment house during the winter season. If the gang-form opening is closed with a tent during internal heating using a hot air blower in the winter, the internal temperature rises compared to the non-reserved due to air-tightness of the curing spaces, and uniform temperature distribution can be ensured. In addition, it is possible to increase curing efficiency by reducing the amount of heat supplied and shortening the heating time.

• Fire Science and Engineering
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• v.11 no.4
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• pp.3-14
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• 1997

The smoke filling process for the atrium space containing a fire source is simulated using two types of deterministic fire model : Zone model and Field model. The zone model used is the CFAST(version 1.6) model developed at the Building and Fire Research Laboratories, NIST in the USA. The field model is a self-developed frie field model based on Computational Fluid Dynamic (CFD) theories. This article is focused on finding out the smoke movement and temperature distribution in atrium space which is cubic in shape. For solving the liked set of velocity and pressure equation, the PISO algorithm, which strengthened the velocity-pressure coupling, was used. Since PISO algorithm is a time-marching procedure, computing time si very fast. A computational procedure for predicting velocity and temperature distribution in fire-induced flow is based on the solution, in finite volume method and non-staggered grid system, of 3-dimensional equations for the conservation of mass, momentum, energy, species and so forth. The fire model i.e Zone model and Field model predicted similar results for clear heights and the smoke layer temperature.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.5
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• pp.94-101
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• 1996

The purpose of this paper is to analyze the field distribution and the current distribution of leaky coaxial cable with the finite difference-tiem domain(FDTD) algorithm. finite difference equations of maxwell's equations are defined in cylindrical coordinate systems. To simulate the unbounded problem like a free space, the Mur's absorbing boundary conditon is also used. After modeling the leaky coaxial cable with the three dimensional grid structure, the transient resoponse of th efield distribution and the current distribution are depicted in the time domain.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.1174-1179
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• 2004

In general, the national rail system put an emphasis on distribution planing of stations for smooth operation of transporting goods, train allocation, parking, and maintenance. Since the national rail system is operated on the ground level, it is feasible to improve various aspects of the system during its operation. On the contrary, urban rail system is operated in the limited space under the ground, and thus, improving various aspects of the system during its operation is infeasible. Specifically, the urban subway system must have a comprehensive track distribution plan because the urban subway system has to operate in a limited environment such as it operates in a much shorter time period, The subway system has to be ready for various operations and events such as trains returning in the opposite direction. parking trains that need repair, parking during night time, storing various maintenance equipments, and connections to other tracks. Furthermore, considering the future extension of tracks, a comprehensive track distribution plan is a must.

• 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 Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.47.3-48
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• 2016

The zodiacal light (ZL), combination of the sunlight scattered by and the infrared light emitted by the interplanetary dust (IPD) particles, changes with time due to the asymmetric distribution of the particles with respect to the Earth's orbit. Especially, the variation of the ZL brightness toward the ecliptic poles are useful to probe the properties of the global distribution of the IPD because we can evade the effect of the small scale structures, such as the asteroidal dust bands. The ecliptic poles are frequently visited by the infrared (IR) space telescopes owing to their sun-synchronous orbits or for specific purposes. We collect and analyze the observations toward the ecliptic poles by COBE/DIRBE, AKARI, and MIRIS, covering the wavelengths from about 1 to $25{\mu}m$. The observed seasonal variations of the ZL are modeled with a simple IPD cloud model to derive cloud parameters. The parameters are compared with those of the empirical cloud models by Kelsall et al. (1998) and Kondo et al. (2016), and the discrepancies are discussed.

• Korean Journal of Materials Research
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• v.24 no.2
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• pp.111-115
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• 2014

Titanium and its alloys are useful for implant materials. In this study, porous Ti-Nb-Zr biomaterials were successfully synthesized by powder metallurgy using a $NH_4HCO_3$ as space holder and $TiH_2$ as foaming agent. Consolidation of powder was accomplished by spark plasma sintering process(SPS) at $850^{\circ}C$ under 30 MPa condition. The effect of high energy milling time on pore size and distribution in Ti-Nb-Zr alloys with space holder($NH_4HCO_3$) was investigated by optical microscope(OM), scanning electron microscope(SEM) & energy dispersive spectroscopy(EDS) and X-ray diffraction(XRD). Microstructure observation revealed that, a lot of pores were uniformly distributed in the Ti-Nb-Zr alloys as size of about $30-100{\mu}m$ using mixed powder and milled powders. In addition, the pore ratio was found to be about 5-20% by image analysis, using an image analyzer(Image Pro Plus). Furthermore, the physical properties of specimens were improved with increasing milling time as results of hardness, relative density, compressive strength and Young's modulus. Particularly Young's modulus of the sintered alloy using 4h milled powder reached 52 GPa which is similar to bone elastic modulus.

• Journal of The Korea Institute of Healthcare Architecture
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• v.24 no.2
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• pp.15-25
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• 2018

Purpose: The important things in space plan of a screening center are improving the spatial awareness by space systemization and minimizing the examination time for customers, and reducing the required time of screening work and maximizing the capacity for the screening center. Therefore, we tried to solve the problem of improving spatial awareness and reducing the examination time by using the pedestrian based discrete event simulation at the minimum cost. Methods: We have analyzed the drawbacks and the supplement points by comparing the floor plan at the time of opening and the current floor plan. Based on the analysis, we propose an improved plan which changes the location of the examination rooms and the number of services, and we also verify the improved plan based on simulation analyses. Results: 1) Through the analyses, we derived the drawbacks of the floor plan at the time of opening, and we realized that the current floor plan reflects the drawbacks. 2) The major reasons of the long examination time are the human traffic jam and the occurrence of queues due to unreasonable allocation of services. 3) Through the discrete event simulation analyses, it was possible to specify the place of the queues manually so as to use the given space fairly. 4) Using the discrete event simulation, it was possible to reduce the examination time and to improve the spatial awareness effectively at the minimum cost. Implications: Although the proposed simulation methodology in this paper is an analysis of the existing screening center, we expect that the proposed methodology will be used to develop a more efficient architectural design process by pre-applying the method to the course of designing a screening center and finding the suitability of the proposed method with the matched number of services.