• Korean Journal of Materials Research
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• v.11 no.10
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• pp.863-868
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• 2001

The present study was carried out to investigate the effect of MA processing variables on the microstructural properties of composite powders and the coefficient of thermal expansion of pulse electric current sintered AlN-Cu powder compacts. The AlN-Cu powders had a size of less than 15 $\mu\textrm{m}$ with 25 nm size of copper crystallite after MA 32 hours. The finely distributed AlN-Cu powder compacts were completely achieved after PECS. The residual oxygen was considerably removed after hydrogen reduction treatment. The residual carbon was completely removed to 97%. The CTE of AlN-Cu powder compacts showed a good consistency with Kingery-Tuner model when the volume fraction of copper was less than 60%. When it was more than 60%, the CTE had a good agreement with Series model.

• Applied Chemistry for Engineering
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• v.19 no.4
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• pp.397-401
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• 2008

To verify model adaptation and flexibility, non-isothermal simulation for perlite expansion has been carried out. Temperature-dependent perlite properties are applied to energy equations for bubble temperature change and perlite melt temperature gradient. Bubble temperature is changed with volume change, water evaporation, and heat flux from melt. Temperature gradient of perlite melt is affected by decreasing bubble temperature. As a result, prediction model and code have been developed below 1100 K with 5% accuracy. At 1100~1400 K, lower 7% accuracy has been obtained from the calculation results.

• Journal of Hydrogen and New Energy
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• v.15 no.4
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• pp.257-265
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• 2004

Numerical analysis, as EAM(Embedded Atom Method), in the atomic level is necessary to analyze the relation between the hydrogen and hydrogen absorption metals. EAM established on density functional theory was developed as a new means for calculating various properties and phenomena of realistic metal systems. In this study, we had constructed the EAM program from constitutive formulae and parameters of the hydrogen, nickel and palladium for the purpose of predicting the expansion behavior on hydrogen absorbing. In result, not only the ground state properties of metals but also lattice constants and the volume expansion ratio of metal hydrides show good agreement with Daw's data and experiment data.

• International Journal of Air-Conditioning and Refrigeration
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• v.10 no.4
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• pp.220-228
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• 2002

The cool-down performance after soaking is very important in an automotive air-conditioning system and is considered as a key design variable. Therefore, transient characteristics of each system component are essential to the preliminary design as well as steady-state performance. The objective of this study is to develop a computer simulation model and ostinato theoretically the transient performance of an automotive air-conditioning system. To do that, the mathematical modelling of each component, such as compressor, condenser, receiver/drier, expansion valve, and evaporator, is presented first of all. The basic balance equations about mass and energy are used in modelling. For detailed calculation, condenser and evaporator are divided into many sub-sections. Each sub-section is an elemental volume for modelling. In models of expansion valve and compressor, dynamic behaviors are not considered in this analysis, but the quasisteady state ones are just considered, such as the relation between mass flow rate and pressure drop in expansion device, polytropic process in compressor, etc. Also it is assumed that there are no heat loss and no pressure drop in discharge, liquid, and suction lines. The developed simulation model is validated by comparing with the laboratory test data of an automotive air-conditioning system. The overall time-tracing properties of each component agreed well with those of test data in this case.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.11
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• pp.1089-1096
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• 2001

The cool-down performance after soaking is very important in an automotive air-conditioning system and is considered as the key design variable. Therefore, understanding of the overall transient characteristics of the system is essential to the preliminary design as well as steady-state characteristics. The objective of this study is to develop a computer simulation model and estimate theoretical1y the transient performance of an automotive air-conditioning system. To accomplish this, a mathematical modelling of each component, such as compressor, condenser, expansion valve, and evaporator, is presented first of all. For a detailed calculation, condenser and evaporator are divided into many subsections. Each sub-section is an elemental volume for modelling. In models of expansion valve and compressor, dynamic behaviors are not considered in an attempt to simplify the ana1ysis, but the quasi-static ones are just considered, such as the relation between mass flow rate and pressure drop in expansion device, polytropic process in compressor, etc. The developed simulation model is validated with a comparison to laboratory test data of an automotive air-conditioning system. The overall time-tracing properties of each component agreed fairly well wish those of test data in this case.

• Journal of Navigation and Port Research
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• v.43 no.5
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• pp.320-327
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• 2019

This study examined the port expansion plan for the fishery port at the east coast of Korea, in accordance with permission conditions for coastal ports such as a limit on the cargo volume and passenger demand for the coastal tourism belt formation. The site was chosen as a municipal coastal port attracting the new ocean industry and building waterfront zone as a hub of new marine tourism. Two different numerical models (Swan and Bouss 2D) were used. Before applying to the target sea area, some numerical tests were conducted for the variation according to Bouss-2D's strong/weak and nonlinear technique compared to the irregular diffraction of semi-infinite breakwater with a theoretical solution. As a result, there was a difference in strong nonlinearity with breaking waves and it was necessary to experiment with a strong nonlinear analysis technique for the actual site. Two numerical models were applied to the fishery port site and the tranquility of some alternatives were analyzed. The numerical results show the most suitable plan was ALT-1, with satisfied harbor tranquility and reasonable economic sense. The extension of the east breakwater and enlarged turning basin of the F-Land plan have brought generally more stable harbor tranquility than the ALT-1. The result can be used as a reference for the port expansion plan in the future.

• Archives of Plastic Surgery
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• v.32 no.1
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• pp.29-36
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• 2005

Craniosynostosis is the premature fusion of one or more sutures of either cranial vault or base. Fused sutures may impede normal growth of the calvaria, leading to characteristic skull deformities; Morphological craniosynostosis is classified descriptively. Being craniosynostosis uncorrected the deformity progresses continuously and causes an increase of intracranial pressure. The surgical involvement aims at the expansion of intracranial space as well as satisfactory achievement of craniofacial shape. Early surgical correction in infancy prevents the deformity from the further progression and possible associated complication of high intracranial pressure. A long period of follow-up is essential to asses the outcome of an effectiveness of the surgery. measurement of intracranial volume has been concerned in medical personnel and anthropologists for many years. A reliable and accurate measurements of the intracranial volume facilitates to make a diagnosis and treatment of craniosynostosis. Pre-and postoperative change of intracranial volume was evaluated with 3D CT scanning in 12 cases of craniosynostosis who underwent frontal advancement and total cranial vault remodeling. Increased intracranial volume is attributed to surgical release of craniosynostosis and natural growth. We conceive that the intracranial volume is significantly increased after surgical correction of fused cranial sutures and along with natural growing. A procedure of frontal advancement and total cranial vault remodeling is very useful to correct such a deformity as craniosynostosis. And also 2 cases out of five mentally retarded patients improved remarkably and Forehead retrusion or temporal depression followed in another two cases.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1042-1044
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• 1995

This paper provides the results and analyses of investigations into porcelain suspension insulators failures on the KEPCO system. The high failure rate of suspension insulators on distribution lines has been attributed to the volume expansion of the cement, the insulation puncture breakdown of the porcelain and the power arc failure. The utility must use only the good insulators and at least reduce the insulator failure rate. So, this paper recommends that the utility make test criteria(cement expansion test, steep front-of-wave flashover voltage test and power arc test. etc) on the suspension insulators.

• Journal of the Korean Society of Visualization
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• v.9 no.4
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• pp.69-73
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• 2011

Butterflies have been known to suck viscous liquids through a long, cylindrical proboscis using the large pressure difference formulated by the cyclic expansion and contraction of a muscular pump located inside their head. However, there are few studies on the liquid-feeding phenomena in a live butterfly, because it is hard to observe the internal morphological structures under in vivo condition. In this study, the dynamic motion of the pump system in a butterfly was in vivo visualized using synchrotron X-ray micro-imaging technique to analyze the liquid-feeding mechanism. The period of the liquid-feeding process is about 0.3sec. The expansion stage is about two times larger than the contraction stage in one cycle. The cyclic variation of pump volume generate large negative suction pressure and the pressure difference inside the long proboscis of a butterfly is estimated to be larger than 1atm.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.233-236
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• 1999

In this paper, we carried out fundamental experiments to use the steel manufacturing slag as a concrete aggregate. Generally there are two types of slag, the blast-furnace slag and the steel manufacturing slag. The latter is classified by the difference of manufacturing method of steel into the convertor slag and the electric-furnace slag. The steel manufacturing slag mainly contains SiO2 and CaO as the chmical composition. The reaction with water and a little of free CaO in the steel manufacturing slag makes the expansion of volume change. Therefore, we primarily investigated physical properties, expansion mechanism, pH value, aging effects and aging methods in the steel manufacturing slag. Then compressive strength of concrete with steel slag aggregate is measured.