• Journal of Powder Materials
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• v.17 no.4
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• pp.312-318
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• 2010

High speed steels (HSS) were used as cutting tools and wear parts, because of high strength, wear resistance, and hardness together with an appreciable toughness and fatigue resistance. Conventional manufacturing process for production of components with HSS was used by casting. The powder metallurgy techniques were currently developed due to second phase segregation of conventional process. The powder injection molding method (PIM) was received attention owing to shape without additional processes. The experimental specimens were manufactured with T42 HSS powders (59 vol%) and polymer (41 vol%). The metal powders were prealloyed water-atomised T42 HSS. The green parts were solvent debinded in normal n-Hexane at $60^{\circ}C$ for 24 hours and thermal debinded at $N_2-H_2$ mixed gas atmosphere for 14 hours. Specimens were sintered in $N_2$, $H_2$ gas atmosphere and vacuum condition between 1200 and $1320^{\circ}C$. In result, polymer degradation temperatures about optimum conditions were found at $250^{\circ}C$ and $480^{\circ}C$. After sintering at $N_2$ gas atmosphere, maximum hardness of 310Hv was observed at $1280^{\circ}C$. Fine and well dispersed carbide were observed at this condition. But relative density was under 90%. When sintering at $H_2$ gas atmosphere, relative density was observed to 94.5% at $1200^{\circ}C$. However, the low hardness was obtained due to decarbonization by hydrogen. In case of sintering at the vacuum of $10^{-5}$ torr at temperature of $1240^{\circ}C$, full density and 550Hv hardness were obtained without precipitation of MC and $M_6C$ in grain boundary.

• The Korean Journal of Mycology
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• v.25 no.4 s.83
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• pp.297-304
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• 1997

Effects of cultural conditions on the production of xylanase by Tremella fuciformis, symbiotic fungi and mixed fungi were investigated. The optimum carbon source for high production of xylanase by T. fuciformis, symbiotic fungi and mixed fungi was xylose. The optimum nitrogen source for both T. fuciformis and symbiotic fungi was $KNO_3$, whereas mixed fungi was $(NH_4)_2SO_4$. The optimum culture period for high production of xylanase was 5 days for both T. fuciformis and mixed fungi, and 6 days for symbiotic fungi, respectively. The optimum temperature for T. fuciformis and symbiotic fungi was $40^{\circ}C$, and the corresponding value for mixed fungi was $45^{\circ}C$. Xylanase activity was high at pH 6 for T. fuciformis and symbiotic fungi, and pH 7 for mixed fungi. Except $Hg^{2+}$ and $Pb^{2+}$, metal ions in T. fuciformis inhibited the activity of xylanase, and, thermal stability of xylanase in T. fuciformis, symbiotic fungi and mixed fungi maintained 80% of activity until $50^{\circ}C$. The Michaelis constant (Km) of xylan was $6.25{\times}10^{-5}\;M$ in T. fuciformis, $5.6{\times}10^{-2}\;M$ in symbiotic fungi, $5.2{\times}10^{-2}\;M$ in mixed fungi.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.7
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• pp.1453-1460
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• 2002

Creep-fatigue crack growth models have been proposed employing $(C_t)_{avg}$ as a crack tip parameter characterizing the time-dependent crack growth. The basic assumptions made in these previous models were ideal creep reversal conditions such as no creep reversal and complete creep reversal condition. Due to this assumption, the applicability of the models was limited since they did not consider partial creep reversal condition which is usually observed in many engineering metals at high temperature. In this paper the creep reversal parameter, Temperature;$C_R$, which was defined by Grover, is critically evaluated to quantity the extent of partial creep reversal at the crack tip. This approach does not rely on any simplifying assumptions regarding the extent of the amount of creep reversal during the unloading part of a trapezoidal fatigue cycles. It is shown that the $(C_t)_{avg}$ value calculated for 9Cr steel agrees well with the experimentally measured one. It is argued that the extent of improvement is not significant when the result is compared with that of the conventional model which has an assumption of full creep reversal behavior.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.10
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• pp.901-907
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• 2000

The conceptual determination of mixed-refrigerant (MR) for a closed Joule-Thomson cryocooler is described in this paper. The thermodynamic cycle design was mainly considered to develop a cryocooler by using a compressor of domestic air-conditioning unit. The target cooling performance of the designed cryocooler is 10 W around 70 K with less than 5 kJ/kg enthalpy rise. The systematic approach of choosing a proper refrigerant among 20 different kinds of mixture for such cryogenic temperature was introduced in detail. The main components of the cryocooler are compressor, evaporator, oil separator, after-cooler, counterflow heat exchanger, and J-T expansion device. Due to the limitation of the compressor operation range, the temperature after the compression was limited below $117^{\circ}C$ (390 K) and the temperature before compression was restricted above $5^{\circ}C$ (278 K). 20 atm of discharging pressure (high pressure) and less than 3 atm suction pressure (low pressure) were the design conditions. The inlet temperature of a counterflow heat exchanger in the high Pressure side was about 300 K. The proper composition of the mixed refrigerant for the designed J-T cryocooler is 15% mol of$ N_2, 30% mol of $CH_4,\; 30% mol\; of C^2H^ 6,\; 10%\; mol\; of\; C_3H_8\; and \;15%\; mol\; of\; i-C_4H_10$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.503-506
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• 2015

In accordance with IoT(Internet of Things) commercialization, the need to design SoC-based hardware platform with wireless communication is increasing. This paper therefor proposes an SoC platform architecture with Smart Frame System inter-communicating between devices. Wireless communication functions and high-performance real-time image processing hardware structure was applied to existing digital photo frame. We developed a smart phone application to control the smart frame through Bluetooth communication. The SoC platform hardware consists of CIS controller, Memory controller, ISP(Image Signal Processing) module for image scaling, Bluetooth Interface for inter-communicating between devices, VGA/TFT-LCD controller for displaying video. The Smart Frame System to support the IoT services was implemented and verified using HBE-SoC-IPD test board equipped with Virtex4 XC4VLX80 FPGA. The operating frequency is 54MHz.

• Electronics and Telecommunications Trends
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• v.35 no.5
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• pp.43-56
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• 2020

The 5G system standardization body has been developing standard functions to provide ultra-high speed, ultra-high reliability, ultra-low latency, and ultra-connected services. In 3GPP Rel-16, which was recently completed, this system has begun to develop ultra-high reliability and ultra-low latency communication functions to support the vertical industry. It is expected that the trend in the adoption of mobile communication by the vertical industry will continue with the introduction of 5G. In this paper, we present the industrial Internet-of-Things (IIoT) service scenarios and requirements for the adoption of 5G systems by the vertical industry and the related standardization trend at present. In particular, we introduce the 5G time-sensitive networking standard technology, a core technology for realizing 5G-based smart factories, for IIoT services.

• Toxicological Research
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• v.18 no.3
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• pp.227-232
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• 2002

In order to find out the appropriate in vitro method for high correlation with in vivo, we com-pared the sensitivities of phototoxicity (PT) in vitro method between in human keratinocytes, HaCaT cells and in 3T3 fibroblast cells derived from Balb/c mice. Both cells were exposed to six known phototoxic chemicals : promethazine, neutral red, chlortetracycline, amiodarone, bithionol, 8-methoxypsoralen, or non-phototoxic chemical, ALS (ammonium laureth sulfate) and then irradiated with 5 J/$cm^2$ of UVA. Cell viability ($IC_{50}$ ) was measured by neutral red uptake (NRU) assay. The ratio of $IC_{50}$ value of chemicals in the presence and absence of UVA was determined by the cut-off value. The phototoxic potential of test chemicals in NRU assay was determined by measuring the photoirriation factor (PIF) with a cut-off value of 5. In both 3T3 and HaCaT cells, all known phototoxic chemicals were positive (over 5 of PIF value), except that bithionol was found to be non-phototoxic to HaCaT cells, and ALS, non-phototoxic chemical was negative. These results suggest that Balb/c 3T3 cell was more sensitive than HaCaT cell to predict phototoxicity potential.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.547-550
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• 2008

Precipitation characteristics of the Fe-36Ni based high strength Invar alloy for power transmission wire was investigated in this study. High strength can be obtained in this alloy through precipitation hardening and strain hardening by cold working. $FactSage{(R)}$ in this study, revealing that equilibrium phases which can be formed are two kind of MC-type precipitates and MoC carbide. The latter stoichiometric carbide was expected to be formed at relatively lower temperature $770^{\circ}C$. High strength above 1000MPa and 40% of elongation were obtained at room temperature in both cases.

• Journal of Convergence for Information Technology
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• v.11 no.4
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• pp.111-121
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• 2021

In order to determine the possibility that Chrysanthemum indicum L. cultured with Lactococcus lactis (CILL) is a material for obesity suppression food, the body weight, body fat mass, and T cells were determined in C57BL/6 mice induced by a high fat diet. The CILL (25.15±2.44 g) demonstrated weight loss from week 4 onward and maintained a low weight gain from week 1 to week 8 (1.00±0.53 g). The 8-week body weight (30.38±4.17 g) indicated loss of 13.15% when compared to the HFD (60% high fat diet, 34.99±2.09 g). Fat mass decreased to 10.3022±2.8813 g, and the absolute liver weight decreased relative to that in the HFD. CD4+ T cells were 4.84±1.33%, CD8+ T cells 7.02±2.26%, and CD4+CD8+ T cells 1.46±0.81%, which were all higher than those in the HFD. As a result, CILL can be used as a material for preventing obesity as an effective measure toward reducing weight when consumed orally.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.5
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• pp.475-479
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• 1999

Langasite ($La_{3}Ga_{5}SiO_{14}$) was found to have wide application as a promising piezoelectric material. It has high thermal stability of the frequency and large electromechanical coupling factor. For the further development of new compounds with langasite type structure, powders in the La-Al-Si-O system were synthesized by a modified Pechini process. The evolution of the crystalline phase during calcination was studied using TG-DTA, XRD and TEM for the precursor powders. Decomposition proceeded via dehydration and removal of excess solvents at low temperatures ($T<500^{\circ}C$), followed by the crystallization of lanthanum aluminum silicate ($T>800^{\circ}C$) and phase transformation to $LaAlO_{3}$ phase ($T>1200^{\circ}C$). Transmission electron microscopy (TEM) of the calcined powders showed diffuse hollow rings corresponding to an amorphous phase at $800^{\circ}C$ and clear diffraction patterns corresponding to a crystalline phase from the P321 space group ($T<1200^{\circ}C$) and the R3m ($T<1200^{\circ}C$).