• Korean Journal of Materials Research
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• v.11 no.8
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• pp.641-646
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• 2001

The $CoSi_2$ layers have been in-situ grown on undoped poly-Si by the reactive chemical vapor deposition of $Co({\Eta}^5-C_5H_5)(CO)_2$ at $650^{\circ}C$ and their thermal stabilities have been investigated in the temperature range of 800 to $1000^{\circ}C$. The $CoSi_2$ layer grown by the in-situ method had grains with large area of (111) plane, while grains with little area of (111) plane appeared on the $CoSi_2$ layer grown by the conventional two-step method where $CoSi_2$ formed first and transformed to $CoSi_2$. The thermal stability of the $CoSi_2$ layer grown by the in- situ process was improved by more than $100^{\circ}C$ higher than that of the $CoSi_2$ layer grown by the conventional two-step process. The $CoSi_2$ layer grown in situ on a large-grained Poly-Si was stable up to $950^{\circ}C$. The effect of stability improvement by the in situ growth was more pronounced when the grain sizes of the poly-Si substrate were small. The improved thermal stability of the in-situ grown $CoSi_2$ layer could be mainly due to the formation of a uniform $CoSi_2$ layer with the $CoSi_2$ grains, which are in the form of epitaxial-like growth on the each poly-Si grains, causing a reduction of the interfacial energy of the system.

• New & Renewable Energy
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• v.2 no.4 s.8
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• pp.33-38
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• 2006

The Dish/Stirling system with the Stirling engine is currently used to convert solar energy directly to electrical energy. Successful operation of dish/Stirling system is supported by hybrid system, which will allow continuous operation driven by solar and combustion heating. The hybrid Receiver has to be provided with an additional combustion system. The heat pipe receiver and conbustion system were manufactured and tested for thermal characteristics of receiver. Maximum temperature difference along the heat pipe surface is $200^{\circ}C$. Emission measurements showed low NOx values of 28 to 46 ppm and very high CO values of 18 to 201 ppm.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.816-817
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• 2007

As UNFCC(United Nations Framework Convention on Climate Change) is enhanced, Korea will perform a CO2 reduction duty. The CO2 reduction duty will effect Korea power system because coal and oil thermal generations emit large CO2 form about 46% of total CO2 emission. Moreover various alternatives should be designed to comply with CO2 reduction duty. In this paper, we analysis resource planning considering CO2 emission constraints and emission trading. And we analysis resource planning under using LP(Linear Programing) and MIP(Mixed Integer Programing).

• Journal of Powder Materials
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• v.2 no.3
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• pp.223-230
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• 1995

The effects of Mn and Co additions up to 0.6 and 2.0 wt% respectively and the amount of cold-rolled reduction on the thermal expansion coefficient (TEC) of powder rolled Fe-Ni Invar strips were investigated. The compacted strips were sintered, homogenized and cold-rolled to the final thickness of 0.8 mm, 0.65 mm and 0.4 mm. All the strips reached full density except the case of 0.8 mm sample which has a very few porosities. The interstitials which are well known to increase TEC were minimized to the level of 10 rpm C,5 and N,0 by the processing. TEC was found to decrease by increasing the cold reduction. The Mn content had little effect on the TEC. But in Fe-Ni-Co system, TEC decreased with Co content up to 0.4 wt% and then increased, yielding the minimum value of $0.2 {\times} 10-6/^{\circ}C$ at 0.4 wt% Co. This value is much lower than that of commercial Invar product. Such effect of Co is considered to be related with the maxiumum spontaneous- magnetostriction effect.

• Journal of the Korean Magnetics Society
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• v.10 no.4
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• pp.159-163
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• 2000

MR characteristics in magnetic tunnel junction using CoO as the oxide barrier were investigated. Spin-dependent tunnel junctions were fabricated on 4$\^$o/ tilt-cut (111)Si substrates in 3-gun magnetron sputtering system. The top and bottom ferromagnetic electrodes were Ni$\_$80/Fe$\_$20/(300 $\AA$) and Co(300 $\AA$), respectively. The oxide barriers (CoO) were formed by the thermal oxidation at room temperature in an O$_2$ atmosphere and the plasma oxidation. The increase of coercive field due to antiferromagnetic-ferromagnetic coupling has been observed in O$_2$plasma-oxidized CoO based junctions at room temperature. At a sensing current of 1 mA, MR ratios of O$_2$plasma-oxidized CoO based junction and thermal-oxidized CoO based junction at room temperature were 1% and 5%, respectively. Larger MR ratios are observed in magnetic tunnel juctions with thermal oxidized CoO when sensing current more than applied 1.5 mA. At a sensing current of 1.5 mA, we have observed MR value of 28 % and specific resistance (RA=R$\times$A) value of 10.9 ㏀$\times$㎛$^2$. When specific resistance values reached 2.28 ㏀$\times$㎛$^2$, we have observed that MR ratios become as high as 120%.

• Korean Journal of Optics and Photonics
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• v.1 no.1
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• pp.107-113
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• 1990

Characteristics and applications of three major types of lasers are discussed. They are chemical-metabolic, thermal destructive, and nonthermal mechanical lasers. The thermal destructive lasers ($CO_2$, Argon, and Nd:YAG) are especially explained in detail with regard to energy density, wavelength, fluence, stage of thermal destruction, and advantages of laser surgery. Excimer and Q-swiched lasers are discussed as nonthermal mechanical ones. Delivery system, optical fiber and articulated arm, is also discussed. Finally, recent advancements of medical laser are included in the conclusion.

• Journal of Environmental Science International
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• v.25 no.3
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• pp.385-393
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• 2016

Oxidative and thermal degradation of alkanolamines for a promising $CO_2$ capture technology of absorption might cause decrease in $CO_2$ capture efficiency and formation of hazardous byproducts. In this study, characteristics of a representative absorbent of monoehtanolamine (MEA) were examined for a long term operation using a laboratory scale absorption system. An $CO_2$ absorption system with ID 56 mm and absorption zone height 100 cm was developed for the characterization. Absorption solution of 30 wt% MEA was circulated at 100 mL/min to treat air with 15% $CO_2$ and 1 ppm NO at 10 L/min. Temperatures of absorber and stripper were maintained at $40^{\circ}C$ and $120^{\circ}C$, respectively. For the course of 5 weeks continuous operation, MEA concentration was decreased approximately by 70% and $CO_2$ removal efficiency was dropped from 95% to 65%. Ionic byproducts of $NH_4{^+}$, $NO_2{^-}$, and $NO_3{^-}$ were accumulated up to 48 g/mL, 0.2 g/mL, and 1.5 g/mL, respectively, tracking the variation of MEA concentration. Formation of various organic byproducts were also observed.

• Nuclear Engineering and Technology
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• v.54 no.4
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• pp.1482-1494
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• 2022

Power conversion cycles (Subcritical Steam, Supercritical Steam, Open Air Brayton, Recuperated Air Brayton, Combined Cycle, Closed Brayton Supercritical CO₂ (sCO₂), and Stirling) are evaluated for land-based nuclear microreactors based on technical maturity, system efficiency, size, cost and maintainability, safety implications, and siting considerations. Based upon these criteria, Air Brayton systems were selected for further evaluation. A brief history of the development and applications of Brayton power systems is given, followed by a description of how these thermal-to-electrical energy conversion systems might be integrated with a nuclear microreactor. Modeling is performed for optimized cycles operating at 3 MW(e) with turbine inlet temperatures of 500 ℃, 650 ℃ and 850 ℃, corresponding to: a) sodium fast, b) molten salt or heat pipe, and c) helium or sodium thermal reactors, coupled with three types of Brayton power conversion units (PCUs): 1) simple open-cycle gas turbine, 2) recuperated open-cycle gas turbine, and 3) recuperated and intercooled open-cycle gas turbine. Aeroderivative turboshaft engines employing the simple Brayton cycle and two industrial gas turbine engines employing recuperated air Brayton cycles are also analyzed. These engines offer mature technology that can facilitate near-term deployment with a modest improvement in efficiency.

• Journal of Electrical Engineering and Technology
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• v.13 no.6
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• pp.2402-2411
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• 2018

Fluoronitriles-$CO_2$ gas mixtures are promising alternatives to $SF_6$ in environmentally-friendly gas-insulated transmission lines (GILs). Insulating gas heat transfer characteristics are of major significance for the current-carrying capacity design and operational state monitoring of GILs. In this paper, a three-dimensional calculation model was established for a GIL using the thermal-fluid coupled finite element method. The calculated results showed close agreement with experimentally measured data. The temperature distribution of a GIL filled with the Fluoronitriles-$CO_2$ mixture was obtained and compared with those of GILs filled with $CO_2$ and $SF_6$. Furthermore, the effects of the mixture ratio of the component gases and the gas pressure on the temperature rise and current-carrying capacity of the GIL were analyzed. Results indicated that the heat transfer performance of the Fluoronitriles-$CO_2$ gas mixture was better than that of $CO_2$ but worse than that of $SF_6$. When compared with $SF_6$, use of the Fluoronitriles-$CO_2$ gas mixture caused a reduction in the GIL's current-carrying capacity. In addition, increasing the Fluoronitriles gas component ratio or increasing the pressure of the insulating gas mixture could improve the heat dissipation and current-carrying capacity of the GIL. These research results can be used to design environmentally-friendly GILs containing Fluoronitriles-$CO_2$ gas mixtures.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.1022-1028
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• 2024

A neutronics study of a supercritical CO₂-cooled fast reactor core for nuclear propulsion has been performed in this work. The thermal power of the reactor core is 30 MWth and a ceramic UO₂ fuel can be used to achieve a 20-year lifetime without refueling. In order to make a compact core with inherent safety features, the drum-type reactivity control system and folding-type shutdown system are adopted. In addition, we suggest a cold shutdown system using gadolinium as a spectral shift absorber (SSA) against flooding. Although there is a penalty of U-235 enrichment for the core embedded with the cold shutdown system, it effectively mitigates the increment of reactivity at the flooding of seawater. In this study, the neutronics analyses have been performed by using the continuous energy Monte Carlo Serpent 2 code with the evaluated nuclear data file ENDF/B-VII.1 Library. The supercritical CO₂-cooled fast reactor core is characterized in view of important safety parameters such as the reactivity worth of reactivity control systems, fuel temperature coefficient (FTC), coolant temperature coefficient (CTC), and coolant temperature-density coefficient (CTDC). We can say that the suggested core has inherent safety features and enough flexibility for load-following operation.