• Journal of the Korean Society of Hazard Mitigation
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• v.1 no.1 s.1
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• pp.157-163
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• 2001

The objective of the present study is to predict the characteristics of the fire and smoke propagations in a clean room. Numerical calculations have been performed by using the finite volume method to obtain temperature and velocity distributions in the clean room. In odor to account for the turbulent flow characteristics, the standard $k-{\varepsilon}$ model is used. From this study, it was found that the fire propagation could be fully developed only after 150 seconds when the ventilation system in the clean room was off. And the smoke mass fraction showed a similar distribution as the gas temperature. Since the simulated fire was proceeded up to $20{\sim}30%$ of the room within 60 seconds. it could be recommended that the occupants should be evacuated from the room within 30 seconds.

• International Journal of Highway Engineering
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• v.8 no.3 s.29
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• pp.29-37
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• 2006

The primary objective of this study is to characterize traffic axle loadings that consider Korea specific traffic conditions for developing mechanistic-based pavement design method as a part of Korea Pavement Research Program(KPRP). Although the concept of equivalent single axle load(ESAL) has been generally used since the 1960s for the pavement design, the mechanistic-based pavement design procedure requires more accurate axle loading data on the specific pavement. In this study, axle loading data were collected according to vehicle type and highway functional classification. Axle-load spectrum was then standardized by cumulative density function(cdf), because the axle load spectrum could vary from the observed site, truck traffic volume, and truck type, Finally, this study presented the procedure and S-shaped exponential models for characterizing axle load spectra according to vehicle type and highway functional classification.

• Resources Recycling
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• v.11 no.6
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• pp.12-17
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• 2002

Solvent extraction experiments have been performed to separate copper from $CuCl_2$-$NiCl_2$-$CoCl_2$$ solutions using Alamine336 and LIX84. The complex formation tendency between metal ions and chloride ion had a great effect on the distribution coefficients of Cu, Co and Ni ions and separation factor of Cu to Co and Ni. In the experimental ranges of chloride ion concentration from 0.5 to 4.0 M, LIX84 was superior to Alamine336 in separating copper from cobalt. When the volume percentage of LIX84 and Alamine336 was varied from 5 to 40%, LIX84 was more effective than Alamine336 in separating Cu from Co and Ni in solutions in which the chloride ion concentration was 1.0 M.

• Economic and Environmental Geology
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• v.49 no.3
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• pp.225-242
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• 2016

Rock physics serves as a useful tool for seismic reservoir characterization and monitoring by providing quantitative relationships between rock properties and seismic data. Rock physics models can predict effective moduli for reservoirs with different mineral components and pore fluids from well-log data. The distribution of reservoirs and fluids for the entire seismic volume can also be estimated from rock physics models. The first part of this report discusses the Voigt, Reuss, and Hashin-Shtrikman bounds for effective elastic moduli and the Gassmann fluid substitution. The second part reviews various contact models for moderate- to high-porosity sands. In the third part, constant-cement model, known to work well for the sand that gradually loses porosity with deteriorating sorting, was applied to the well-log data from an oil field in the North Sea. Lastly, the rock physics template constructed from the constant-cement model and the results from the prestack inversion of 2D seismic data were combined to predict the lithology and fluid types for the sand reservoir of this oil field.

• Journal of Cadastre & Land InformatiX
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• v.51 no.2
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• pp.141-150
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• 2021

Fine dust is a substance that greatly affects human health, and various studies have been conducted in this regard. Due to the human influence of particulate matter, various studies are being conducted to predict particulate matter grade using past data measured in the monitoring network of Seoul city. In this paper, predictive model have focused on particulate matter concentration in May, 2019, Seoul. The air pollutant variables were used to training such as SO₂, CO, NO₂, O₃. The predictive model based on Adaboost, and training model was dividing PM₁₀ and PM_2.5. As a result of the prediction performance comparison through confusion matrix, the Adaboost model was more conformable for predicting the particulate matter concentration grade. Although air pollutant variables have a higher correlation with PM2.5, training model need to train a lot of data and to use additional variables such as traffic volume to predict more effective PM₁₀ and PM_2.5 distribution grade.

• Journal of Industrial Convergence
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• v.21 no.8
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• pp.51-58
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• 2023

Blockchains have recently struggled to design for the ideal distributed trust networks by solving scalability trilemma. However, local conflicts between some countries lead to imbalance on energy distribution. Besides, blockchain networks (e.g., Bitcoin) currently consume enormous energy for transaction and mining. The existing data volume based trust model evaluated an increasing blockchain size better than Lubin's trust model in scalability trilemma. In this paper, we propose a scalability based energy model to evaluate sustainability for blockchain networks, considering energy consumption for transaction, time duration, and the blockchain size of growing blockchain networks. Through the rigorous numerical analysis, we compare the proposed scalability based energy model with the existing model for the satisfaction and optimal blockchain size. Thus, the scalability based energy model will provide an assessment tool to choose the proper blockchain networks to solve scalability trilemma problem and prove sustainability.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.7
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• pp.105-116
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• 2004

The design of pico-/nano-satellites is particularly challenging due to constraints in mass, volume, power, and surface area. An efficient low-cost picosatellite HAUSAT-1 Electrical Power Subsystem (EPS) is developed to supply the power for various loads during the full mission life. This paper addresses design and analysis results of solar arrays, batteries, power conditioning and distribution units. The component selection, manufacturing and test results are presented by considering appropriate development cost and performance. The simulation results of power system are also illustrated, according to operational modes, through energy balance analysis. Finally, the EFS design feasibility is verified by comparing analysis results with functional and environmental test results at the system and component levels, respectively.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.3
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• pp.11-18
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• 2000

When supersonic underexpanded jets are exhausted from the nozzle, complex shock cell configurations such as barrel shock, expansion fan, Mach disc, and exhaust-gas jet boundary are appeared repetitively. The shock cell is smeared by turbulence dissipation and disappeared in long distance from the nozzle. When underexpanded jet is suddenly impinged on a flat plate, it forms very complex flow structure. In this paper, we solve compressible Wavier-Stokes equation adapting finite volume method to obtain jet impingement flow structure and compare calculated data with experimental ones. It is shown that numerical simulation data are in good agreement with experimental one in a short distance between nozzle exit and flat plate and little influence of underexpanded ratio is appeared in jet impingement now distribution.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.4
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• pp.695-704
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• 2018

The rainfall cases were identified by rainfall estimation techniques which were developed by using X - band marine radar. A digital signal converter was used to convert the signal received from the marine radar into digital reflectivity information. The ground clutter signal was removed and the errors caused by beam attenuation and beam volume changes were corrected. The reflectivity showed a linear relationship with the rain gauge rainfall. Quantitative rainfall was estimated by converting the radar signal into an cartesian coordinate system. When the rainfall was recorded more than $5mm\;hr^{-1}$ at three automatic weather stations, the rain cell distribution on the marine radar was consistent with that of the weather radar operated by Korea meteorological Adminstration.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.148-158
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• 2011

As critical infrastructure, bridges play an indispensable role in facilitating the distribution of goods. When bridges reach their end of useful life or get damaged by natural disasters such as earthquakes or storms, they have to be removed and reconstructed. When bridges in service need to be reconstructed, user costs occur from vehicle detours and traffic congestions, and social costs occur from noise and dust during construction periods. However, these user and social costs are not considered during reconstruction and the evaluation methods of those costs are vague. Thus, there is lack of appropriate bridge types that consider these costs. Therefore, this paper identifies the social overhead costs that occur during bridge reconstruction, which is also called, users' socioeconomic values. Next, it proposes a method to evaluate user costs during bridge reconstruction, and appraises the method. User costs are evaluated based on traffic information, social and material volumes including the bridge's daily traffic volume, peak hours, detour distance and time. In addition, time delay costs due to traffic operational costs and bridge reconstruction are also taken into consideration.