• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.2
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• pp.169-174
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• 2007

In process of reinforced concrete (RC) box structure, the heat of hydration may cause serious thermal cracking. This paper reports results of hydration heat control in mass concrete using the oscillating heat pipe. There were three RC box molds ($1.2m{\times}1.8m{\times}2.4m$) which were different from each other. One was not equipped with pulsating heat pipe. The others were equipped with pulsating heat pipe. All of them were cooled with natural air convection. The pulsating heat pipe was composed of 10 turns of serpentine type copper pipe whose outer and inner diameters were 4 and 2.8 mm respectively. The working fluid was R-22 and charging ratio was 40% by volume. The temperature of the concrete core was approximately $55^{\circ}C$ in the winter without pulsating heat pipe. For a concrete with pulsating heat pipe, however, the temperature difference with the outdoor one reduced up to $12^{\circ}C$. The index figure of crack was varied from 0.75 to 1.38.

• Journal of Environmental Impact Assessment
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• v.20 no.3
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• pp.381-395
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• 2011

Present work aims to establish an integrated management system of environmental data base for nine typical wind holes or air holes in Korea. It basically deals with definition, geographical distribution, morphological pattern, physical characteristics and anthropogenic environments of wind hole to propose systematic preservation strategy of their periglacial landscape and flora, which are known to be sensitive to global warming. Wind hole, in which cool air blows out during the summer, but mild air comes out during the winter from a cave or hole, is frequently found on northwest- and north-facing slopes on the terminal point of steep talus, block field, and block stream, and can be categorized into three types, i.e., talus, cave and sink types. Environmental characteristics of nine wind holes are analyzed on the basis of their geology, landform, climate, soil, hydrology, vegetation, road, footpath, land-use, and management system, and relevant DB are prepared. Wind hole areas with unique landscape and ecological values need to be designated as a nature reserve, and zoning of core, buffer, and transitional zones are required for the multi-dimensional preservation of periglacial landscape and ecosystem. Phytogeographical values of glacial relict plants, including mountain cranberry(Vaccinium vitis-idaea) at its global southernmost limit at Bangnaeri wind hole, Hongchon County, Gangwon Province of Korea are discussed in detail as a floristic refugia in connection with climate change during the Pleistocene Epoch and potential in-situ and ex-situ preservation sites in the future.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.8
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• pp.541-548
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• 2019

In this paper, the required amount of heat for an anti-icing system of a Flush Air Data Sensing(FADS) system is predicted. For an efficient prediction during the early stage of a design process, a handbook method is used. A program of which inputs are flight conditions is developed to predict the required amount of heat. A CFD analysis is conducted to compute the water catch efficiency which is one of the core parameters used in the handbook method. Kriging method, one of well-known regression mothods, is utilized to construct a surface contour database to evaluate impingements of droplets. To predict the trajectories of droplets, the database of a flow field around the surface is built using Kriging method as well.

• Korean Journal of Agricultural Science
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• v.14 no.1
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• pp.81-97
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• 1987

Two nozzles with different size (Figure 2) were particularly designed to supply air through the swirl core into the central part of the liquid stream in the same parallel direction to produce a well-mixed air and water in the whirl chamber as spray liquid in bubble formation. Atomization was attempted to improve by using both the preliminary break-up process with less viscosity and less surface tension in the whirl chamber and the effects of increased frequency of the band of drops with the raised ambient air density in front of the nozzle orifice. The volumetric ratio between spray liquid and air on four levels was used to investigate the effects of air as a component of the mixture on atomization. The results of the experiment were summarized as follows; Droplet size became progressively finer as the operating pressure was increased in the range of $0.70kg/cm^2$ to $6.33kg/cm^2$, which was similar to the previous works. The new atomizing mechanism so-called 'air-center nozzle' gave a narrower range in droplet size distribution with smaller volumetric median diameter (VMD) than that of the existing spray system at a given pressure, which showed the possibility of improvement of atomization in a certain limit. The volumetric median diameter produced by the new atomizing mechanism was decreased from the central region toward the exterior edges across the spray pattern.

• Journal of Intelligence and Information Systems
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• v.21 no.1
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• pp.65-82
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• 2015

Recently, there has been a surge of interest in finding core issues and analyzing emerging trends for the future. This represents efforts to devise national strategies and policies based on the selection of promising areas that can create economic and social added value. The existing studies, including those dedicated to the discovery of future promising fields, have mostly been dependent on qualitative research methods such as literature review and expert judgement. Deriving results from large amounts of information under this approach is both costly and time consuming. Efforts have been made to make up for the weaknesses of the conventional qualitative analysis approach designed to select key promising areas through discovery of future core issues and emerging trend analysis in various areas of academic research. There needs to be a paradigm shift in toward implementing qualitative research methods along with quantitative research methods like text mining in a mutually complementary manner. The change is to ensure objective and practical emerging trend analysis results based on large amounts of data. However, even such studies have had shortcoming related to their dependence on simple keywords for analysis, which makes it difficult to derive meaning from data. Besides, no study has been carried out so far to develop core issues and analyze emerging trends in special domains like the aviation industry. The change used to implement recent studies is being witnessed in various areas such as the steel industry, the information and communications technology industry, the construction industry in architectural engineering and so on. This study focused on retrieving aviation-related core issues and emerging trends from overall research papers pertaining to aviation through text mining, which is one of the big data analysis techniques. In this manner, the promising future areas for the air transport industry are selected based on objective data from aviation-related research papers. In order to compensate for the difficulties in grasping the meaning of single words in emerging trend analysis at keyword levels, this study will adopt topic analysis, which is a technique used to find out general themes latent in text document sets. The analysis will lead to the extraction of topics, which represent keyword sets, thereby discovering core issues and conducting emerging trend analysis. Based on the issues, it identified aviation-related research trends and selected the promising areas for the future. Research on core issue retrieval and emerging trend analysis for the aviation industry based on big data analysis is still in its incipient stages. So, the analysis targets for this study are restricted to data from aviation-related research papers. However, it has significance in that it prepared a quantitative analysis model for continuously monitoring the derived core issues and presenting directions regarding the areas with good prospects for the future. In the future, the scope is slated to expand to cover relevant domestic or international news articles and bidding information as well, thus increasing the reliability of analysis results. On the basis of the topic analysis results, core issues for the aviation industry will be determined. Then, emerging trend analysis for the issues will be implemented by year in order to identify the changes they undergo in time series. Through these procedures, this study aims to prepare a system for developing key promising areas for the future aviation industry as well as for ensuring rapid response. Additionally, the promising areas selected based on the aforementioned results and the analysis of pertinent policy research reports will be compared with the areas in which the actual government investments are made. The results from this comparative analysis are expected to make useful reference materials for future policy development and budget establishment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.666-671
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• 2018

A honeycomb panel is a plate made by attaching two surface plateson eitherside of a honeycomb core. The honeycomb plate hasexcellent specific strength and energy absorption and is suitable for use in regions where good impact resistance is required. Recently, with the increasing the need for a lightweight design to facilitate transportation, numerous studies have been conducted using aluminum honeycomb plates as body materials for vehicles such as automobiles and high-speed trains. In addition, honeycomb plates have excellent sound deadening properties, as well as excellent heat insulation and durability. Savings in weight using lightweight materials such as aluminum alloy for honeycomb panel's skin can lead to increase fuel economy and reduction in air pollution. In this study, in order to improve the design technology of the honeycomb plate material, the manufacturing technology of the aluminum honeycomb core and honeycomb plate material and various mechanical properties of the honeycomb plate were evaluated. From the results, it was found that the design of the manufacturing process of the aluminum honeycomb plate, as well as itsproduction and characteristics, were improved. The resulting excellent energy absorption capability of the honeycomb plate was due to the repetitive core buckling, indicating that the higher the compressive strength, the higher the strength per bonded area.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.10
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• pp.574-580
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• 2020

An inorganic binder is eco-friendly because it can be cured at low temperatures and does not emit harmful gases. In addition, related research is progressing rapidly owing to the small defects in the core. On the other hand, inorganic binders based on silicates (SiO₂-Na₂O) have unique absorbent properties. This results in the absorption of moisture from the air and the weakening of the bonding force. In particular, the castings used in cast steel require high-strength properties because of the higher temperatures than aluminum castings. In this study, waxes containing ester groups were selected to improve the absorption of moisture of inorganic binders. The inorganic binder was characterized by X-ray fluorescence and thermogravimetric analysis-differential thermal analysis. The inorganic binder core strength was then evaluated. In the case of an inorganic binder containing wax, the water resistance increased to 216 N/㎠, confirming the up to 55% improvement in strength. Excellent casting characteristics were confirmed through steel castings.

• Journal of the Korean Magnetics Society
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• v.16 no.6
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• pp.300-304
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• 2006

The varied heating temperatures were used for magnetic core materials, which nano sized ${\alpha}-Fe$ crystalline was created in nanocrystalline Fe-Si-B-Nb-Cu materials, with hish permeability and low power loss. The highest permeability and lowest power loss were obtained to the specimen heat-treated at $510^{\circ}C$. The signal transmission characteristics of inductive coupler, which was manufactured by using the magnetic core materials prepared in this study, at low frequency range, was influenced strongly by magnetic property of magnetic core materials as this result is corresponding to the permeability as a function of heat treatment temperature, as well, it was improved by impedance matching at high frequency range. Over $500{\mu}m$ of air gap in coupler is required to maintain the magnetic properties without magnetic saturation on the subterranean line transferred hish current of 300 A. The inductive coupler for PLC, which has an attenuation characteristics of less than 5dB, was manufactured using nano-crystalline magnetic core materials through the above mentioned research results.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3056-3061
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• 2007

The technology of AC solenoid valves is now considered as a core technology in the fields of the production line of semi-conductor chips and the micro fluid chips for medical applications. And AC solenoid valves, which operate by compressed air, are characterized by high speed response, great repeatability and that the pressure on the cross sectional area of poppet is kept constant regardless of the fluctuation of the pressure exerted on the ports. In this study, AC solenoid valves that posses the high-speed responsibility and the high rate of flow have designed and analyzed through the law of equivalent magnetic circuit and Finite Element Method (FEM) respectively. In case of poppet, Flow field characteristic was analyzed by the variation of poppet and it was able to display flow field by changing the location of the poppet. Also, we verified possibility of the design through the static and dynamic pressure and the 3D distribution curve of the force by working the front poppet.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.4
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• pp.99-106
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• 2005

In this study, the electromagnetic characteristics of a flat-type two-dimensional proportional solenoid were analyzed by the magnetic reluctance method. The equivalent magnetic circuit equation for the solenoid was derived by modeling the reluctance of air gaps and magnetic structural components such as pole core, armature and yoke. It was solved iteratively because of the nonlinear magnetization properties of the iron parts. The solutions showed good agreement with experimental data. Based on the equivalent magnetic circuit equation, the influence of design parameters on the force-to-armature displacement curves was mathematically derived and experimentally verified. In this way, dominant design parameters could be analytically determined.