• Journal of Power System Engineering
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• v.9 no.1
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• pp.5-13
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• 2005

Acoustic emission(AE) is defined as the transient elastic waves thar are generated by the rapid release of energy. The advantage of AE is that very early crack growth can be detected well before a highly stressed component may fail. At present, an exact diagnosis is the most reliable means for determining the soundness of structures during power plant operations. AE monitoring has been applied successfully in power plants to determine mechanical problems, pressure vessel integrity and external valves leaks, vacuum leaks, the onset of cavitation in pumps and valves, the presence of flow(or no flow) in piping and heat exchange equipment, etc. Acoustic emission(AE) technology has recently strengthened its application base, and practitioners' understanding of the technique's fundamentals. This paper introduces the methods of a survey and assessment on AE monitoring applications in nuclear, fossil and hydraulic power plant. The main objective of this paper was to obtain information on various applications of AE technology in power plant.

• Journal of Powder Materials
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• v.1 no.2
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• pp.153-158
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• 1994

The effect of the role of alloyed components on the densification of two kind of high speed steel (mixed and prealloyed powder), which were sintered at 1403~ 1573 K for 7.2 ks in vacuum, was investigated. The results obtained were as follows. (1) Without the presence of Vanadium (V), the relative density of sintered compacts (Ds) could not reached the density of 100% regardless of the. elements in the compacts. (2) The addition of V up to 2 mass% did not result In the complete densification when the carbon content was fixed at 2% in the compact. (3) With the fixed amount of V of 7%, Ds decreased with the increase of the carbon content. (4) The addition of mixed fine powder to the prealloyed powder in the range of 20 to 40% provided the complete densification and carbide panicles of 1~2 $\mu\textrm{m}$ through the solid phase sintering. (5) The V element played important role in controlling the complete or incomplete densification of the sintered compacts in the alloyed component because of its formation of stable oxide and carbide as well as the low equilibrium pressure of CO gas.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1454-1460
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• 2009

Ultra-speed tube train, which runs in vacuum atmosphere to overcome aero-dynamic dragging force, is considered as a high-speed ground transportation system to back up long-distance air travel. To realize the ultra-speed tube train, feasibility study of currently available Maglev technologies especially for propulsion and levitation system is needed. Propulsion by linear synchronous motor(LSM) and levitation by electro-dynamic suspension(EDS) which are utilized in the Japan's MLX system could be one of candidated technologies for ultra-speed tube train. In the LSM-EDS system, the key component is superconducting magnet, and its reliability and performance is very important to guarantee the safe-operation of Maglev. As the initiative of the feasibility study, this paper deals with the basic structure of superconducting magnet and core technologies to design and operate it. And by surveying the current R&D achievement in Korea, the nation's capability to develop advanced superconducting magnet for Maglev is presented.

• Journal of the Korean Society of Food Science and Nutrition
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• v.28 no.2
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• pp.319-325
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• 1999

Volatile flavor compounds in Korean salt fermented shrimp on the market were analyzed by vacuum simultaneous distillation solvent extraction/gas chromatography/mass spectrometry/olfac tometry(V SDE/GC/MS/O) and aroma extract dilution anlaysis(AEDA). A total of 32 volatile com pounds were detected by GC/O analysis. Of these, 18 were positively identified, and composed of S containing compounds(5), aldehydes(4), ketones(3), N containing compounds(3), ester(1), alcohol(1) and aromatic hydrocarbon(1). Predominant odorants(Log3FD$\geq$4) in salt fermented shrimp were 2,3 butanedione(sour/buttery), 1 octen 3 one(earthy/mushroom like), dimethyl trisulfide(cooked cabbage /soy sauce like) and 2 acetylthiazole(grainy/nutty). Predominant free amino acids were aspartic acid, glutamic acid(sour and umami taste), arginine, methionine(bitter) and lysine(sweet and bitter) in evaluation of taste value.

• Journal of the Korean Solar Energy Society
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• v.23 no.2
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• pp.81-90
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• 2003

UTAC(unglazed transpired air collector) system has unique advantage for space heating and tempering ventilation air over the conventional collector system such as flat plate and vacuum collector. UTAC can improve radiative and convective loss due to nonglazed component and enhanced plate surface configuration. and heating energy and its equivalent green house emission performance can be improved from the use of this like collector in building application. The Option D Calibration simulation approach of IPMVP(International Performance Measurement and Verification Protocol) in ESCO businesses has been recommended to use of the calibrated computer modules like these Energy-10. DOE2.1E and TRNSYS(transient system simulation). This study is to develop subroutine type-203 of TRNSYS15.2 program and appraise thermal performance of UTAC. With newely addeded subroutine type-203. 1) Thermal performance of unglazed transpired collector could be possible based on dimensionless variables such as efficiency and heat exchanger effectiveness. and 2) Assessement of energy consists of solar useful and insulation saving for UTAC could be possible.

• Applied Science and Convergence Technology
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• v.23 no.1
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• pp.14-26
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• 2014

Copper is an important component from coin metal to electronic wire, integrated circuit, and to lithium battery. Copper oxides, mainly including $Cu_2O$ and CuO, are important semiconductors for the wide applications in solar cell, catalysis, lithium-ion battery, and sensor. Due to their low cost, low toxicity, and easy synthesis, copper oxides have received much research interest in recent year. Herein, we review the crystallization of copper oxides by designing various chemical reaction routes, for example, the synthesis of $Cu_2O$ by reduction route, the oxidation of copper to $Cu_2O$ or CuO, the chemical transformation of $Cu_2O$ to CuO, the chemical precipitation of CuO. In the designed reaction system, ligands, pH, inorganic ions, temperature were used to control both chemical reactions and the crystallization processes, which finally determined the phases, morphologies and sizes of copper oxides. Furthermore, copper oxides with different structures as electrode materials for lithium-ion batteries were also reviewed. This review presents a simple route to study the reaction-crystallization-performance relationship of Cu-based materials, which can be extended to other inorganic oxides.

• Applied Science and Convergence Technology
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• v.23 no.3
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• pp.151-159
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• 2014

We investigated the effects of the chemical composition and the relative density on the plastic deformation behavior of sintered Fe-based alloys by means of compressive tests. Overall compressive stresses increased as the amount of alloying elements and the relative density were respectively increased. Addition of alloying elements except for Mo increased the yield stress regardless of the relative density. The relationship between the effects of the chemical composition and the relative density and the mean rate of the stress increase was analyzed. A constitutive equation based on the Ludwik equation with the regressed parameters was proposed to predict the compressive true stress-true strain curves of the sintered Fe-based alloys. The K and n values used in the proposed equation were regressed as a function of the alloying elements and the relative density based on the individual K and n values. The plastic deformation behavior predicted using the proposed constitutive equation showed reliable accuracy compared with experimental data.

• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.3
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• pp.115-118
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• 2005

Currently, molecular devices are reported utilizing active self-assembled monolayers (SAMs) containing the nitro group as the active component, which has active redox centers [1]. SAMs are ordered molecular structures formed by the adsorption of an active surfactant on a solid surface. The molecules will be spontaneously oriented toward the substrate surface and form an energetically favorable ordered layer. During this process, the surface-active head group of the molecule chemically reacts with and chemisorbs onto the substrate In this paper, the electrical properties of the 4'4- di(ethynylphenyl)-2'-nitro-1-benzenethiolate was confirmed. This material is well known as a conducting molecule having possible application to molecular level negative differential resistance (NDR) device. To deposit the self-assembly monolayers onto the gold electrode, the prefabricated Au(1 l l) substrates were immersed into 0.5[mM/l] self-assembly molecule in THF solution. Then, the electrical properties and surface morphologies of 4' 4-di(ethynylphenyl)-2' -nitro-1-benzenethiolate were measured by using the ultra-high vacuum scanning tunneling microscopy (UHV-STM).

• Food Science and Preservation
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• v.4 no.1
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• pp.69-75
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• 1997

Peony is a medicinal herb which have utilized widely as chineses medicine. The paeoniflorin is the predominant component In peony root, monoterpene glucoside containing pinane structure. The effective components were extracted with the cold water from the intact peony roots, and effectively extracted with 70% ethanol from the dry powder of peony roots. The changes of paeoniflorin contents were investigated during the drying process of peony roots and processing of peony extract by the heat-treatment. Air-drying was the best condition for the preservation of paeoniflorin content among the drying processes of peony roots. But convective drying at 6$0^{\circ}C$ was recommended for the drying process of peony roots in large scale. The paeoniflorin in peony extracts was not destroyed by the treatment at 6$0^{\circ}C$ and 8$0^{\circ}C$ for 5 hrs, but destroyed 30%, 28% and 40% of paeoniflorin by treatment at 10$0^{\circ}C$ for 5 hrs, 115$^{\circ}C$ and 121$^{\circ}C$ for 10 minutes, respectively. The paeoniflorin was continueously extracted for 4 hrs from the dry pieces of peony roots(0.5$\times$0.5$\times$0.5cm) in boiling water but destroyed gradually after 4 hrs at 10$0^{\circ}C$. Paeoniflorins in 70% ethanol extracts of peony root were not destroyed at all in the process of concentration to dry powder at 60"C on vacuum.cuum.

• Food Science and Preservation
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• v.30 no.4
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• pp.669-682
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• 2023

The production of distilled soju by fermenting nonsteamed rice was evaluated using commercial enzyme products. White koji and modified nuruk had alpha-amylase activities of 31.90 U/g and 3,532.71 U/g, respectively, and gluco-amylase activities of 698.32 U/g and 4,899.58 U/g, respectively. The enzyme products had activities of 5,604.15-225,182.00 U/g and 13,517.41-120,822.41 U/g, respectively. At enzyme concentrations of >800 mg/L, the Chung-moo-purified enzyme had an alcohol productivity of ≥19%. Nurukzyme R400, Sanferm Yied, and Diazyme X4 exhibited alcohol productivities of >19% at concentrations of >600 mg/L. The alcohol content of the vacuum distillates was 41.31%-44.86%. The volatile component with the alcohol content adjusted to 25% was analyzed and principal component analysis was performed. The volatile components in white koji, Diazyme X4, and Sanferm Yield were similar. The modified nuruk treatment group had a relatively high ethyl lactate content compared to the white koji treatment group. The Nurukzyme R400 treatment group had high contents of butyric acid and ethyl butyrate. The Chung-moo-purified enzyme was characterized by a low component content. Thus, when enzyme products were used in nonsteamed rice fermentation, no effect on the alcohol productivity and quality of vacuum distilled soju was observed, suggesting that it can replace white koji and modified nuruk.