• 한국분말재료학회지
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• 제17권4호
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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.

• 한국균학회지
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• 제25권4호통권83호
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• pp.297-304
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• 1997

흰목이균, 공생균, 혼합균(흰목이균과 공생균)의 xylanase 생산 최적 탄소원은 xylose이었고 흰목이균, 공생균의 질소원은 $KNO_3$, 혼합균의 질소원은 $(NH_4)_2SO_4$이었다. Xylanase 생산 최적 배양일수는 흰목이균과 혼합균은 5일, 공생균은 6일이었으며 최적온도는 흰목이균과 공생균이 $40^{\circ}C$, 혼합균이 $45^{\circ}C$이었다. Xylanase 생산 최적 pH는 흰목이균과 공생균이 pH 6.0, 혼합균이 pH 7.0이었으며, 금속이온의 영향은 흰목이균에서는 $Hg^{2+}$, 혼합균에서는 $Pb^{2+}$를 제외하고는 금속이온이 저해적으로 나타났다. 흰목이균, 공생균, 혼합균의 xylanase 열안전성은 $50^{\circ}C$까지 80% 이상 안정하였으며, 기질(Birchwood) 특이성에 관해서는 Birchwood로부터의 xylan이 가장 활성이 높았다. 흰목이균, 공생균, 혼합균의 xylanase 기질농도는 20mg/ml, 반응시간은 45분까지 활성이 급속히 상승하다가 그후 매우 완만한 반응속도를 나타내므로서 이를 기초로 하여 Km값을 얻은 결과, 흰목이균은 $6.25{\times}10^{-5}\;M$, 혼합균은 $5.2{\times}10^{-2}\;M$, 공생균은 $5.6{\times}10^{-2}\;M$로 흰목이균, 혼합균, 공생균 순으로 효소 기질과의 친화력이 약하였다.

• 대한기계학회논문집A
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• 제26권7호
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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.

• 설비공학논문집
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• 제12권10호
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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 $CH_4,\; 30% mol\; of C^2H^ 6,\; 10%\; mol\; of\; C_3H_8\; and \;15%\; mol\; of\; i-C_4H_10$.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2015년도 추계학술대회
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• pp.503-506
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• 2015

IoT(Internet of Things) 상용화에 따라 무선 통신이 가능한 하드웨어 구조 개발의 필요성이 증가하고 있다. 따라서 본 논문에서는 디바이스 간 연동이 가능한 Smart Frame System이 내장된 SoC(System on a Chip) 플랫폼 하드웨어 구조를 제안한다. 기존 디지털 액자에 무선통신 기능과 실시간 처리가 가능한 하드웨어 구조를 적용하였고, Bluetooth를 이용하여 제어할 수 있는 스마트폰 어플리케이션을 개발하였다. 제안하는 SoC 플랫폼의 하드웨어 구조는 CIS(CMOS Image Sensor) Controller 모듈, Memory Controller 모듈, 확대, 축소, 회전 등의 다양한 영상처리를 위한 ISP(Image Signal Processing) 모듈, 디바이스 간 통신을 위한 Bluetooth Interface, 영상 출력을 위한 VGA Controller 모듈, TFT-LCD Controller 모듈로 구성된다. IoT 서비스를 지원하는 Smart Frame System은 Virtex4 XC4VLX80 FPGA 디바이스가 장착된 HBE-SoC-IPD 테스트 보드를 사용하여 구현 및 검증하였으며, 동작 주파수는 54MHz이다.

• 전자통신동향분석
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• 제35권5호
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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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• 제18권3호
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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.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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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.

• 융합정보논문지
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• 제11권4호
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• pp.111-121
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• 2021

감국의 유산균 발효를 통한 감국 배양물(CILL)의 비만억제 식품의 소재로서 가능성을 알아보기 위해 고지방식이로 유도된 C57BL/6 mice에서의 체중, body fat mass, T cell 등을 측정하였다. 체중 변화에서 CILL 군 (25.15±2.44 g)은 4주부터 체중 감소를 보였으며, 1주차부터 8주차까지 낮은 증체량을 유지했다(1.00±0.53 g). 8주 체중(30.38±4.17 g)은 HFD 군(60% high fat diet, 34.99±2.09 g) 대비 13.15%의 체중 감소를 보였다. Fat mass는 10.3022±2.8813 g로 감소했으며, 간 절대 중량에서 HFD 군에 비해 감소하였다. CD4+ T cell 4.84±1.33%, CD8+ T cell 7.02±2.26%, CD4+CD8+ T cell 1.46±0.81%로 HFD 군에 비해 높게 측정되었다. 결과적으로 CILL은 비만억제 효과가 있으며, CILL내의 비만억제 물질을 선별한다면 효과적인 비만억제 식품 소재로서의 가능성이 있을 것으로 사료된다.

• 한국결정성장학회지
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• 제9권5호
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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 ($T<1200^{\circ}C$).