• Transactions of the Korean hydrogen and new energy society
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• v.22 no.2
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• pp.206-212
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• 2011

The effect of process parameters on $H_2$ production from water vapor excited by HF ICP has been qualitatively examined for the first time. With the increase of ICP power, characteristics of $H_2$ production from $H_2O$ dissociation in plasma was divided into 3 regions according to both reaction mechanism and energy efficiency. At the edge of region (II) in the range of middle ICP power, energy effective hydrogen production from $H_2O$ plasma can be achieved. Furthermore, within the region (II) power condition, heating of substrate up to $500^{\circ}C$ shows additional increase of 70~80% in $H_2$ production compared to $H_2O$ plasma without substrate heating. This study have shown that combination of optimal plasma power (region II) and wall heating (around $500^{\circ}C$) is one of effective ways for $H_2$ production from $H_2O$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.252-252
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• 2008

The microhotplates consisting of a Pt-ased heating element on AlN/poly 3C-SiC layers were fabricated. The microhotplate has a $600{\mu}m{\times}600{\mu}m$ square shaped membrane which made of $1{\mu}m$ thick ploycrystalline 3C-SiC suspended by four legs. 3C-SiC is known for excellent chemical durability, mechanical strength and sustaining of high temperature. The membrane is fabricated by surface micromachining using oxidized Si sacrificial layer. The Pt thin film is used for heating material and resist temperature sensor. The fabrication methodology allows intergration of an array of heating material and resist temperature detector. For reasons of a short response time and a high sensitivity a uniform temperature profile is desired. The dissipation of microhotplate was examined by a IR thermoviewer and the power consumption was measured. Measured and simulated results are compared and analyzed. Thermal characterization of the microhotplates shows that significant reduction in power consumption was achieved using suspended structure.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.958-964
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• 2001

It is difficult to apply a conventional selection guide for diffusers when the diffuser is installed in a perimeter zone, because the ADPI(Air Diffusion Performance Index) vs. T/L(Throw/Length) curve listed in conventional guide does not consider the perimetric heating load. The objective of this study is to evaluate the effect of the perimetric heating load on the ADPI and to propose a selection guide for proper diffuser when perimetric heating load exists. The velocity and temperature distributions and the ADPI value are obtained numerically with various heat load ratios and air flow rates. The ADPI values by numerical result were compared with existing experimental data to verify the method for evaluation of ADPI proposed in present study. In case of a high side wall diffuser, the ADPI decreased with increases of the flow rate on every heat load ratio of present study except 0.75. Also, the ADPI vs. T/L curves have been proposed for the heat load ratios of 0.25, 0.5, 0.75 to guarantee comport thermal environment when diffusers are installed in perimeter zone.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.3
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• pp.450-458
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• 2000

This study deals with the unsteady close-contact melting of solid blocks on a flat surface subject to convective heating. Normalizing the model equations in reference to the steady solution successfully leads them to cover constant heat flux and isothermal limits at small and large extremes of the Biot number, respectively. The resulting equations admit a compactly expressed analytical solution, which includes the previous solutions as a subset. Based on the steady solution, the characteristics of close-contact melting can be categorized into constant heat flux, transition, and isothermal regimes, the boundaries of which appear to be nearly independent of the contact force. The unsteady solutions corresponding to Biot numbers in the transition regime show intermediate behaviors between those of the two limits. With a proper approximation, the present solution procedure can cope with the case of variable fluid temperature and heat transfer coefficient. Regardless of imposed conditions, the mean normalized Nusselt number during the unsteady process asymptotically approaches to a constant value as the Biot number comes close to each limit.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.4
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• pp.79-84
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• 2020

Induction bending via high-frequency heating is widely used for manufacturing pipe and section steel bends. It allows productivity improvement, unit cost reduction, delivery time compliance, and good mechanical properties. The recent increase in high-end vessels and offshore plants has raised the demand for high-frequency bending, which should improve the product quality and reduce the costs by simplifying the fabrication process; therefore, the characteristics and performance of this technique must be studied and proper design technology is required. During hot pipe bending via induction heating, the outward wall thickness of the pipe is thinned due to tensile stress and this thickness reduction cannot exceed 12.5%. This study focused on pipe bends with a bending curvature of 5D and their optimization design; in particular, the conditions that can both improve the productivity of the high-frequency bending process and keep the maximum thickness reduction below 12.5% were determined.

• Korean journal of food and cookery science
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• v.6 no.2
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• pp.67-76
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• 1990

To observe the propability as the frying oil and oxidative stability of red pepper seed oil, some physico-chemical tests of the oil were examined during 21 days storage period at 5$^{\circ}C$, 15$^{\circ}C$ and 30$^{\circ}C$, and AOM value determined and after heating the oil at 180${\pm}$5$^{\circ}C$ for 40 hours with or without antioxidants. The analysis storage stability of red pepper seed oil showed that the quality of storage group at 5$^{\circ}C$ was almost as good as fresh oil, and the storage group at 30$^{\circ}C$ showed certain degree of rancidity. Change of physico-chemical characteristic during storage were so small so that storage stability of red pepper seed oil was found to be good. AOM stability of red pepper seed oil was 7 hours which is lower than other vegetable oil, but the degree of stability grew greatly after adding phenolic antioxidants, such on TBHQ or PG. As for the chemical change after heating continuously for 40 hours, acid value, peroxide value and refractive index increased, but iodine value decreased as the heating processed. The fatty acid composition also showed the remarkable reduction of linoleic acid. The addition of antioxidants resulted in the delay of oxidation, the degree of which was greater in TBHQ than in PG.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.177-182
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• 2009

The purpose of this study is to investigate planning of urban energy supply systems configuration and operating conditions for the district heating and cooling system using combined heat and power system. Generally the district heating and cooling system has been known to one of the effective way for energy saving, cost reduction and demand side management of energy. Economical analyses were carried out and operating characteristics for some systems were examined in terms of GER factor which represents to the ratio of gas and electricity costs. Rates of the energy consumption and the $CO_2$ emission were compared from the system configuration of the energy supply system with new district cooling system with the conventional one.

• Journal of Power System Engineering
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• v.18 no.1
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• pp.45-50
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• 2014

This study focuses on the analysis of the cooling and heating load in accordance with apartment houses arrangement type using Ecotect Analysis. Korea have to reduce energy consumption part of building except in industry and transport because the rate of dependence on imports amounts to 94%, Apartment houses built in various forms in order to reduce energy are modelled in each window area ratio, shape, orientation, and climate through simulation. Through this study, we can analyze the cooling and heating load by form, window area ratio, orientation, and climate change and know the optimal elements by the form. In particular, although there have been done research on the window area ratio and the arrangement form, the research of the regional climate characteristics and the direction are hardly carried out. To supplement those problem, adding to seven direction and climatic element of southern region is characteristic(L Type, Y Type, - Type) of this study. The form of apartment houses built 10 years ago is modelled for simulation.

• Journal of electromagnetic engineering and science
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• v.17 no.4
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• pp.169-177
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• 2017

The role of electromagnetic (EM) waves in magnetic fusion plasma-ranging from radio frequency (RF) to microwaves-has been extremely important, and understanding of EM wave propagation and related technology in this field has significantly advanced magnetic fusion plasma research. Auxiliary heating and current drive systems, aided by various forms of high-power RF and microwave sources, have contributed to achieving the required steady-state operation of plasmas with high temperatures (i.e., up to approximately 10 keV; 1 eV=10000 K) that are suitable for future fusion reactors. Here, various resonance values and cut-off characteristics of wave propagation in plasmas with a nonuniform magnetic field are used to optimize the efficiency of heating and current drive systems. In diagnostic applications, passive emissions and active sources in this frequency range are used to measure plasma parameters and dynamics; in particular, measurements of electron cyclotron emissions (ECEs) provide profile information regarding electron temperature. Recent developments in state-of-the-art 2D microwave imaging systems that measure fluctuations in electron temperature and density are largely based on ECE. The scattering process, phase delays, reflection/diffraction, and the polarization of actively launched EM waves provide us with the physics of magnetohydrodynamic instabilities and transport physics.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.7
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• pp.1731-1740
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• 1995

Experimental investigations have been made to study the double-diffusive nature of convection of an initially stratified salt-water solution due to heating from below in a rotating cylindrical cavity. The objective is to examine the flow phenomena and the heat transfer characteristics according to the changes in temperature gradient, concentration gradient and rotating velocity of cavity. Thermal and solutal boundary conditions at side wall are adiabatic and impermeable, respectively. The top and bottom plate are maintained each at constant temperature and concentration. The cavity is put into a state of solid body rotation. Like the stationary case, the types of initially-formed flow pattern are classified into three regimes depending on the effective Rayleigh number and Taylor number; stagnant flow regime, single mixed-layer flow regime and successively formed multi-mixed layer flow regime. At the same effective Rayleigh number, the number of initially-formed mixed layer and its growth rate decrease as the effect of rotation increases. The temperature and concentration profiles are both uniform in each layer due to convective mixing in the layered-flow regime, but look both liner in stagnant flow regime and single mixed-layer flow regime. At the interface between adjacent layers, the temperature changes smoothly but the concentration changes rapidly.