• Journal of the Korean Institute of Landscape Architecture
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• v.38 no.3
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• pp.23-32
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• 2010

The purpose of this study is to quantify human energy budgets for different structures of outdoor spatial surfaces affecting thermal comfort, to analyze the impacts of tree shading on building energy savings, and to suggest desirable strategies of urban greenspace planning concerned. Concrete paving and grass spaces without tree shading and compacted-sand spaces with tree shading were selected to reflect archetypal compositional types for outdoor spatial materials. The study then estimated human energy budgets in static activity for the 3 space types. Major determinants of energy budgets were the presence of shading and also the albedo and temperature of base surfaces. The energy budgets for concrete paving and grass spaces without tree shading were $284\;W/m^2$ and $226\;W/m^2$, respectively, and these space types were considerably poor in thermal comfort. Therefore, it is desirable to construct outdoor resting spaces with evapotranspirational shade trees and natural materials for the base plane. Building energy savings from tree shading for the case of Daegu in the southern region were quantified using computer modeling programs and compared with a previous study for Chuncheon in the middle region. Shade trees planted to the west of a building were most effective for annual savings of heating and cooling energy. Plantings of shade trees in the south should be avoided, because they increased heating energy use with cooling energy savings low in both climate regions. A large shade tree in the west and east saved cooling energy by 1~2% across building types and regions. Based on previous studies and these results, some strategies including indicators for urban greenspace planning were suggested to improve thermal comfort of outdoor spaces and to save energy use in indoor spaces. These included thermal comfort in construction materials for outdoor spaces, building energy savings through shading, evapotranspiration and windspeed mitigation by greenspaces, and greenspace areas and volume for air-temperature reductions. In addition, this study explored the application of the strategies to greenspace-related regulations to ensure their effectiveness.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 2000.06a
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• pp.195-214
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• 2000

The high-speed steel (shorten as HSS) consists of Fe and several kinds of transition metal carbides. The cutting tools or wear-resistant materials made from HSS experience relatively high thermal shock because a coolant such as water or oil is flowed over the surface of heated HSS. The purpose of this research is to increase the hardness, strength, fracture toughness and thermal shock resistance of HSS. A possible strategy is to incorporate a hard ceramic material with high strength in HSS matrix. This paper describes the processing, microstructure and mechanical properties of the oriented unidirectional mullite fiber/HSS composite. The unidirectional mullite fibers of 10${\mu}{\textrm}{m}$ diameter were dispersed by the ultrasonic irradiation of 38 kHz in an ethylenglycol suspension containing HSS powder of 11${\mu}{\textrm}{m}$ median size. The dried green composites with 4-68 vol% fibers were hot-pressed for 2h at 100$0^{\circ}C$ in Ar atmosphere under a pressure of 39 MPa. The higher density was achieved in the composite with a lower content of fibers. The oriented unidirectional fibers were well dispersed in the HSS matrix. The average distance between the center of fibers in the cross section was close to the value calculated from the fiber fraction. No reaction occurred at the interfaces between HSS and mullite fibers in the composites. The composite with 13.6 vol% fibers showed 100 MPa of four point flexural strength at room temperature. The thermal expansion of composite with heating was influenced by the orientation of mullite fibers.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.6
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• pp.263-268
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• 2005

The ceramic balls impregnated with $20{\sim}40nm$ sized Ag colloid were examined for heavy metals absorption and antibacterial activities in the drinking water. The preparation conditions of ceramic ball that the porosity was excellent were as follows: starting material: 85 wt% $Ca_{10}(PO_4)_6(OH)_2$, binder: 5 wt% PVA and 15 wt% ${\alpha}-Ca_3(PO_4)_2$, heating temperature: $1000^{\circ}C$, duration: 3 hrs. The ceramic balls obtained under these conditions showed specific surface area of $110m^2/g$, pore size of $120{\mu}m$ and porosity of 80%. Also, as the results of a performance test on a rate of adsorbing and removing heavy metals in the drinking water by using the.AAS, heavy metals such as Zn, Mn, Fe and Cu were removed to the extent that their content became 0.03mg/l or lower after 1 day and they showed an excellent bactericidal activity that all coliforms were killed after 3 hrs.

• Journal of the Korean Chemical Society
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• v.23 no.2
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• pp.88-93
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• 1979

The adsorption of propylene on copper(II)-exchanged zeolite Y was studied by temperature programmed desorption (TPD) technique and electron spin resonance. The amount of propylene adsorbed increased with increasing copper ion content. Four TPD peaks with desorption temperature maxima at $108^{\circ}C({\alpha})$, $243^{\circ}C({\beta})$, $284^{\circ}C({\gamma})$ and $420^{\circ}C({\delta})$ were observed (heating rate: $6.4^{\circ}C$/min). ${\alpha}$Peak which was also observed in the TPD of propylene from NaY may be assigned to propylene physically adsorbed on the zeolite surface, ${\beta}$ and ${\gamma}$ peaks to the chemisorbed propylene either on copper ion or Bronsted acid site produced by copper ion, and $\delta$ peak to cracking products from the polymeric material formed from propylene adsorbed.

• Korean Journal of Materials Research
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• v.22 no.6
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• pp.280-284
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• 2012

Bismuth antimony telluride (BiSbTe) thermoelectric materials were successfully prepared by a spark plasma sintering process. Crystalline BiSbTe ingots were crushed into small pieces and then attrition milled into fine powders of about 300 nm ~ 2${\mu}m$ size under argon gas. Spark plasma sintering was applied on the BiSbTe powders at 240, 320, and $380^{\circ}C$, respectively, under a pressure of 40 MPa in vacuum. The heating rate was $50^{\circ}C$/min and the holding time at the sintering temperature was 10 min. At all sintering temperatures, high density bulk BiSbTe was successfully obtained. The XRD patterns verify that all samples were well matched with the $Bi_{0.5}Sb_{1.5}Te_{3}$. Seebeck coefficient (S), electric conductivity (${\sigma}$) and thermal conductivity (k) were evaluated in a temperature range of $25{\sim}300^{\circ}C$. The thermoelectric properties of BiSbTe were evaluated by the thermoelectric figure of merit, ZT (ZT = $S^2{\sigma}T$/k). The grain size and electric conductivity of sintered BiSbTe increased as the sintering temperature increased but the thermal conductivity was similar at all sintering temperatures. Grain growth reduced the carrier concentration, because grain growth reduced the grain boundaries, which serve as acceptors. Meanwhile, the carrier mobility was greatly increased and the electric conductivity was also improved. Consequentially, the grains grew with increasing sintering temperature and the figure of merit was improved.

• Journal of the Korean Geosynthetics Society
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• v.12 no.4
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• pp.143-147
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• 2013

Geothermal energy is easy to take advantage of renewable energy stored in the earth and the heat exchanger can be collected through a heat exchange piping system. In this study, have been developed a heat exchange pipe loop system which it could be installed in tunnel segmental linings to collect geothermal energy around the tunnel. The heat exchange pipe loop system incorporated in the tunnel segments circulate fluid to transport with heat from the surrounding ground and the heat can be used for heating and cooling of nearby structures or districts. The segmental lining incorporating heat exchange pipe loop system are called as ELS (Energy Lining Segment). There are a number of examples incorporating a heat exchange pipe loop system in a tunnel lining in Europe. In this study, a field case using Energy Lining Segment in Germany and applications in urban area are thoroughly examined. In addition, a CFD (Computational Fluid Dynamics) analysis was carried out to investigate heat flow in Energy Lining Segment.

• Fire Science and Engineering
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• v.15 no.4
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• pp.78-85
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• 2001

This dissertation is research on the fireproof characteristic of molded transformer and the extinguishable characteristics of the NAF S-III. As the research method, a theoretical examination has been made for the combustion process of epoxy resin, which was the main material of molded transformer, and extinguishing process of NAF S-III, which has recently been used in the clean extinguishable chemicals. Furthermore, for its proof, the experiments on combustion and extin-guishment on molded transformer has been performed. By installing the actual molded transformer in and artificial the horizontal heating furnace which has similar conditions with the electrical substation, and after subsequently ignited, the extinguishing process has been observed by classifying it into the natural extinguishment of the ignited transformer, and extinguishable chemical in NAF S-III has been injected. The volume of injected extinguishable chemical was the economical amount which was equipped with the extinguishable capability on the molded transformer under combustion, and it was calculated with the Announcement of the Ministry of Government Administration and Home Affairs as the basis. With the injection of the calculated extinguishable chemicals, the ignited transformer has completely extinguished within one minute.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.1
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• pp.113-118
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• 1999

Aluminum hydrates were synthesized using $AlCl_3$.$6H_2O$as starting material by precipitation method. The phases of obtained powder were amorphous, boehmite, bayerite, nordstrandite depending on the pH of solutions. Aluminum hydrates transformed to $\alpha-Al_2O_3$via $\gamma$- $Al_2O_3$,$\delta$- $Al_2O_3$,and $\theta$-$Al_2O_3$,and particle sizes were grown by increment of heating temperature. The TEX>$\gamma$- $Al_2O_3$ powder was coated on intermediate layer of ceramic membrane by the dip-coating method, and unsupported membrane was also prepared for comparison. The supported layer showed porous structure with small grains, but the unsupported layer revealed interconnected larger grains. Grain growth is dominant in the unsupported layer than in the supported one.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.1
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• pp.28-34
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• 2016

Far-infrared radiation ceramic is an attractive material that provides thermal therapy by permeating the infrared rays into the deep inside of the human skin. Therefore, it is currently used for thermal therapy devices, thermal mat, heating equipment and so on. This work aims to optimize the sintering process of the far-infrared radiation ceramic with the process parameters of temperature and time. A variety of characterization tools have been used to investigate the optimal sintering condition of far-infrared radiation. The phase of far-infrared radiation ceramic was characterized by using X-ray diffraction (XRD) and microstructure of fracture surface was studied by scanning electron microscopy (SEM). The FT-IR was also performed to measure the far-infrared emissivity.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.6
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• pp.91-97
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• 2016

Evaluation on the test of actual concrete member to confirm the fire resistance of the concrete member using ultra-high strength concrete is required. However, test equipment which has large loading capacity is needed to the actual member experiment. So, many researchers evaluated the fire performance through analytical studies using the material models. This study experimentally evaluated strain properties on ultra-high-strength concrete of 80, 130 and 180 MPa with heating and examined to apply the existing strain model about ultra-high-strength concrete. As a results, constants are drawn by method of least squares applying experimental values and calculated values by the existing strain model, it proposed strain model that can be applied to ultra-high-strength concrete.