• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1801-1806
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• 2004

Stochastic nature of subgrid-scale stress causes the predictability problem in large eddy simulation (LES) by which the LES solution field decorrelates with field from filtered directnumerical simulation (DNS). In order to evaluate the predictability limit in a priori sense, the information on the interplay between resolved scale and subgrid-scale (SGS) is required. In this study, the analysis on the inter-scale interaction is performed by applying tophat and cutoff filters to DNS database of flow over a circular cylinder at Reynolds number of 3900. The effect of filter shape is investigated on the interpretation of correlation between scales. A critique is given on the use of tophat filter for SGS analysis using DNS database. It is shown that correlations between Karman vortex and SGS kinetic energy drastically decrease when the cutoff filter is used, which implies that the small scale universality holds even in the presence of the large scale coherent structure.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.7
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• pp.1691-1701
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• 1995

Two aspects of Large-Eddy Simulation(LES) are investigated in order to improve its performance. The first one is on how to determine the model coefficient in conjunction with a dynamic subgrid-scale model, and the second one is on a wall-layer model(WLM) which allows one to skip near-wall regions to save a large number of grid points otherwise required. Especially, a WLM suitable for a separated flow is considered. Firstly, an averaging technique to calculate the model coefficient of dynamic subgrid-scale modeling(DSGSM) is introduced. The technique is based on the concept of local averaging, and useful to stabilize numerical solution in conjunction with LES of complex turbulent flows using DSGSM. It is relatively simple to implement, and takes very low overhead in CPU time. It is also able to detect the region of negative model coefficient where the "backscattering" of turbulence energy occurs. Secondly, a wall-layer model based on a local turbulence intensity is considered. It locally determines wall-shear stresses depending on the local flow situations including separation, and yields better predictions in separated regions than the conventional WLM. The two techniques are tested for a turbulent obstacle flow, and show the direction of further improvements.rovements.

• International Journal of CAD/CAM
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• v.9 no.1
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• pp.111-120
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• 2010

In this paper, we propose a volume rendering method using grid computing for large-scale volume data. Grid computing is attractive because medical institutions and research facilities often have a large number of idle computers. A large-scale volume data is divided into sub-volumes and the sub-volumes are rendered using grid computing. When using grid computing, different computers rarely have the same processor speeds. Thus the return order of results rarely matches the sending order. However order is vital when combining results to create a final image. Job-Scheduling is important in grid computing for volume rendering, so we use an obstacle-flag which changes priorities dynamically to manage sub-volume results. Obstacle-Flags manage visibility of each sub-volume when line of sight from the view point is obscured by other subvolumes. The proposed Dynamic Job-Scheduling based on visibility substantially increases efficiency. Our Dynamic Job-Scheduling method was implemented on our university's campus grid and we conducted comparative experiments, which showed that the proposed method provides significant improvements in efficiency for large-scale volume rendering.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1511-1516
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• 2009

In recent years, the large-scale shaft have been appling in domestic mine for mass production using a large machine, the safety of mine also have been increasing. And the new trial that shotcrete of tunnel field was apply to mine support was progressed. But, the conditions of domestic mine was different from that of tunnel, so, the batch plant of tunnel could not be installed in mine field because of low economical efficiency and difficulty for selection of site. Ready-mixed Shotcrete that mixed with high quality materials and could be controled shotcrete quality is producted in plants and transported to field, so do not need to batch plant. In this study, The Field test of the Ready-mixed Shotcrete was performed in the large-scale mine and was compared with the quality of Field mix shotcrete. As the result of the Field test, compressive strength and rebound of Ready-mixed Shotcrete were superior to these of Field mix shotcrete.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.8
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• pp.418-425
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• 2015

The Korean government plans to establish large-scale horticultural facilities using reclaimed land to improve the competitiveness of the national agricultural sector at the government level. One of the most significant corresponding problems is the ongoing dependence of these facilities on fossil fuel, whereby constant heating is necessary during the winter season to provide the necessary breeding conditions for greenhouse crops. In particular, high-level energy consumption is incurred from the use of heating-related coverings with large heat-transmission coefficients such as those composed of vinyl and glass. This study investigated the potential applicability of waste-incineration heat for use in large-scale horticultural facilities by evaluating the hot-water temperature, heat loss, and available greenhouse area as functions of the distance between the incineration facility and the greenhouse. In conclusion, waste-incineration heat from a HDPE pipe can heat a horticultural facility of 10 ha if the distance is less than 8 km.

• Korean Journal of Materials Research
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• v.16 no.10
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• pp.633-638
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• 2006

Silica powders with spherical shape and narrow size distribution were prepared by large-scale ultrasonic spray pyrolysis applying the droplet classification apparatus. On the other hand, silica powders prepared by large-scale ultrasonic spray pyrolysis without droplet classification apparatus had broad size distribution. Droplet classification apparatus used in this paper applied the principles of cyclone and dispersion plate with small holes. The droplets formed from the ultrasonic spray generator applying the droplet classification apparatus had narrow size distribution. The droplets with fine and large sizes were eliminated by droplet classification apparatus. The optimum flow rate of the carrier gas and diameter of the hole of the dispersion plate were studied to reduce the size distribution of the silica powders prepared by large-scale ultrasonic spray pyrolysis. The size distribution of the silica powders prepared by large-scale ultrasonic spray pyrolysis at the optimum preparation conditions was 0.76.

• Fire Science and Engineering
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• v.20 no.4 s.64
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• pp.65-71
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• 2006

Some major properties such as a heat release rate have been measured experimentally for the validation of fire model and the clarification of fire phenomena as the study is more rigorous recently. Although the reduced-scale experiment also provides the basic data and the physical understanding in fire study, it is not enough to explain real fire problem directly because there is no exact analogy theory between a real fire and the reduced scale model. Therefore, large cone calorimeter have been built and used in a few foreign countries for the measurement of large scale fire. This paper addressed the theoretical background and the description of key features in the design of the facility. It will be a useful guide for implementation of the large scale cone calorimeter in the future.

• Transactions of the Korean hydrogen and new energy society
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• v.35 no.1
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• pp.14-26
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• 2024

Global efforts continue with the goal of transition to a "carbon neutral (net zero)" society with zero carbon emissions by 2050. For this purpose, the technology of water electrolysis is being developed, which can store electricity generated from renewable energies in large quantities and over a long period of time as hydrogen. Recently, various research and large-scale projects on 'green hydrogen', which has no carbon emissions, are being conducted. In this paper, a comparison of water electrolysis technologies was carried out and, based on data provided by the International Energy Agency (IEA), large-scale water electrolysis demonstration projects were analyzed by classifying them by technology, power supply, country and end user. It is expected that through the analysis of large-scale water electrolysis demonstration projects, research directions and road maps can be provided for the development/implementation of commercial projects in the future.

• Journal of Information Management
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• v.43 no.4
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• pp.31-48
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• 2012

Social network analysis was performed on 545 job descriptions in 32 university libraries in Seoul, and drew the job distribution and their relations. Furthermore, for finding the differences according to scale of libraries, this study performed secondary analysis by dividing them two groups. Results show that large scale library show lower density and loose connectivity than small scale library. And while jobs of small scale library were clustered 3 groups, large scale university cluster 4 groups containing 1 technical job and 3 diverse user services. And the jobs that has high specificity, such as catalog or classification, shows high degree centrality in the case of small scale library. Whereas in large scale library they show lower degree centrality, so it can be said that these jobs were performed somewhat independently in large scale libraries.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.06a
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• pp.65-81
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• 2003

During the last few decades in Korea, the development of hillside or mountain areas has rapidly increased for infrastructure construction such as railroads, highways and housing. Many landslides have occurred during these constructions. Also, the amount and scale of damage caused by landslides have increased every year. In the case of Far East Asia including Korea, the damage of landslides is consequently reported during the wet season. In this paper, the effect of stabilizing piles on slope stability is checked and the behavior of slope soil and piles are observed throughout the year by field measurements in the large-scale cut slopes. In particular a large-scale cut slope situated on the construction site for the express highway in Donghae, Korea. First of all, The behavior of the slope soil was measured by inclinometers during slope modification. Landslides occurred in this area due to the soil cutting for slope modification. The horizontal deformations of slope soil gradually increased and rapidly decreased at depth of sliding surface indicating that the depth of sliding surface below the ground surface can be predicted. On the basis of being able to predict the depth of the sliding surface, stabilizing piles were designed and constructed in this slope. To ensure the stability of the reinforced slope using stabilizing piles, an instrumentation system was installed. The maximum deflection of piles is measured at the pile head and it is noted that the piles deform like deflection on a cantilever beam. The maximum bending stress of piles is measured at the soil layer. The pile above the soil layer is subjected to lateral earth pressure due to driving force of the slope, while pile below soil layer is subjected to subgrade reaction against pile deflection. As a result of research, the effect and applicability of stabilizing piles in large-scale cut slopes could be confirmed sufficiently.