Microstructure and High Temperature Mechanical Property of Fe–Cr–B Based Metal/Ceramic Composite Manufactured by Metal Injection Molding Process

Kee‑Ahn Lee,Jin‑Han Gwon,윤태식 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.2

This study investigated the microstructure and the room and high temperature mechanical properties of Fe–Cr–B alloy manufacturedby metal injection molding. In addition, hot isostatic pressing was performed to increase the density of the material,and a comparison of properties was made. Microstructural observation confirmed a bi-continuous structure composedof a three-dimensional network of α-Fe phase and (Cr,Fe)2B phase. The HIPed specimen featured a well-formed adhesionbetween the α-Fe phase and boride, and the number of fine pores was significantly reduced. The tensile results confirmed thatthe HIPed specimen (RT to 900 °C) had higher strengths compared to the as-sintered specimen, and the change of elongationstarting from 700 °C was significantly greater in the HIPed specimen. Fractography suggested that cracks propagatedmostly along the interface between the α-Fe matrix and boride in the as-sintered specimen, while direct fracture of boridewas observed in addition to interface separation in the HIPed specimen.

Two Stage 발효에 의한 고산도 식초 생산

이영철,이금용,김형찬,박기범,유익제,안평욱,최춘언,손세형 한국산업미생물학회 1992 한국미생물·생명공학회지 Vol.20 No.6

산업적으로 산도 17.0% 이상의 고산도 식초를 생산하기 위하여 반연속식인 1st stage와 유가식인 2nd stage로 구성된 two stage 초산 발효를 온도 30 ℃, 교반속도 600 rpm, 통기량 0.1 vvm에서 실시하였다. 1st stage에서 초기 에탄올 농도를 50.0 g/ℓ, 잔류 에탄올 농도를 5.0 g/ℓ로 정하여 반연속적으로 초산발효를 하고, 2nd stage 에서 발효시간의 경과에 따라 에탄올을 유가식으로 첨가하여 초산발효액내의 에탄올 농도를 5.0 g/ℓ에서 10.0 g/ℓ로 유지했을 때 산도가 17.6%인 고산도 식초를 생산할 수 있었으며, 또한 이 ??의 최대 초산 생산성은 3.3 g/ℓ·hr였다. The production of vinegar containing 16.0 ∼18.0% of acetic acid was examined in two stage fermentation consisting of semi-continuous and fed-batch type. The optimum conditions were obtained when the fermentation was carried out at agitation of 600 rpm, aeration of 0.1 vvm and temperature of 30℃. The initial and residual ethanol concentration in 1st stage were 50.0 g/ℓ and 5.0 g/ℓ, respectively, and the ethanol concentration in 2nd stage was maintained from 5.0 to 10.0 g/ℓ. The maximum productivity was 3.3 g/ℓ-hr and the acidity was 17.6% after the two days of acetic acid fermentation.

고속핵에서 GABA가 동맥압에 미치는 영향

이정헌,오기화,안동국,박재식 慶北大學校 醫科大學 1996 慶北醫大誌 Vol.37 No.3

목적 : NTS (nucleus tractus solitarius)는 압감수성 반사 구심성 신경이 처음 시냅스를 형성하는 곳으로 동맥압 조절에 중요한 역할을 한다. NTS에서 어떤 특정 물질이 동맥압 조절에 관여하는지는 정확히 밝혀지지는 않았지만, NTS에 존재하는 많은 물질들이 이들 과정에 관여하고 있다. 그중 하나인 GABA성 약물이 NTS에서 순환계에 미치는 영향을 구명하고자 본 실험을 시행하였으며 아울러 반대편 NTS를 lidocaine으로 억제하였을 경우의 변화를 관찰하여 NTS에서 신경회로 일단을 밝히고자 하였다. 대상 및 방법 : 실험동물은 체중 300-500g 되는 숫컷 Wistar쥐를 사용하였다. 동맥압 측정과 약물 주입을 위하여 대퇴 동정맥에 삽관하였다. 이어서 기관지절개술을 시행하였으며 체온을 36-37℃ 되게 열판을 이용하여 조절하였다. 쥐를 뇌 정위 고정 장치에 두고 머리를 45°숙여 NTS를 노출시킨 다음 약물을 10초간에 걸쳐 80nl주입하였다. 결과 : 인공 뇌척수액을 주입하면 동맥압의 변화가 거의 없었으나 동량의 GABA를 NTS에 주입하면 동맥압이 증가하였다. GABA에 의해 동맥압이 증가된 상태에서 반대측 NTS에 lidocaine을 주입하여 한쪽 기능을 억제시키면 동맥압이 더욱 증가하였다. 또한 lidocaine주입 후 반대쪽의 건전한 NTS에 GABA를 재차 주입하면 동맥압 증가가 적었다. 그리고 GABA를 NTS에 주입 후 정맥으로 nitroprusside를 주입하면 GABA 주입이 없는 대조군에 비해 동맥압 감소가 더 컸으며, lidocaine으로 마취하여 한쪽 NTS의 기능을 차단한 후 반대쪽 건전한 NTS에 GABA를 주입한 경우는 동맥압 감소가 적었다. 동일한 방법으로 lidocaine을 주입한 후 phenylephrine으로 승압을 시키면 동맥압 증가가 적었다. 압감수성 반사는 NTS에 GABA를 주입하거나 또는 반대편 NTS를 lidocaine으로 마취하여 기능을 억제시킨 경우에 둔화되었다. 결론: NTS에서 GABA가 동맥압의 조절 인자로 작용하며, 양쪽 NTS는 상호작용하고 있는 것으로 보인다. The nucleus tractus solitarius (NTS), the site of termination within the brain of baroreceptor afferent fibers, has been shown to be involved in the regulation of arterial pressure (AP). Many neuroactive substances present within the NTS have been shown to be involved in this process, although the manner in which any specific neurotransmitter acts physiologically in the regulation of AP has not been completely elucidated. The present study was intended to clarify the mechanism of action of GABA in the NTS and also to examine the cardiovascular response to inhibition of the contralateral NTS by lidocaine. Male Wistar rats weighing 300-500 g were employed for the experiment. The femoral artery and vein were cannulated to record the arterial pressure (AP) and to inject nitroprusside or phenylephrine, respectively. The tracheotomy was performed and body temperature was kept to 36-37℃. Rats were mounted in a stereotaxic frame with the head flexed downward to an angle of 45°. After the NTS was exposed. GABA or lidocaine was microinjected into the NTS in a volume of 80 nl over 10 seconds through a glass micropipette (outer diameter of the tip 50 ㎛) connected to a 1 ㎕ Hamilton microsyringe. The results obtained are summarized as follows. Microinjection of artificial CSF into the ipsilateral NTS did not alter basal AP. In contrast, microinjection of the same volume of GABA into the NTS produced a significant increase in the AP. The results presented thus far indicated that the volume injected did not affect AP. In animals with elevated AP by GABA injection, injection-of lidocaine into the contralateral NTS resulted in a further increase in AP. After the contralateral NTS was inhibited with lidocaine. injection of GABA into the NTS produced a less increase in AP. After microinjection of GABA into the NTS, the nitroprusside administered i.v. accentuated the increase of AP but not after microinjection of lidocaine into the contralateral NTS. Similar results were obtained with i.v. injection of phenylephrine after pretreatment of lidocaine into the NTS. The baroreflex sensitivity was reduced by microinjection of GABA into the NTS or microinjection of lidocaine into the contralateral NTS. These results suggest that alterations in GABA-mediated neural transmission in the NTS contribute to the regulation of AP and the NTS of both sides have a mutual interaction.

甲狀腺 홀몬의 受容體에 關한 硏究

李民化,安鳳煥,李起榮,朴鐘一 全南大醫大 1980 전남의대학술지 Vol.17 No.1

Fe-29%Ni-17%Co 코바 합금의 고온 내산화성 및 열간 가공성에 미치는 Mo 첨가의 영향

이기안,조창완,성병근,김병문,김문철 대한금속ᆞ재료학회 2006 대한금속·재료학회지 Vol.44 No.3

저열팽창성 Fe-29Ni-17Co 코바 합금의 고온균열 발생과 고온연성에 미치는 S 및 Mn의 영향

이기안,박종혁,조봉현,남궁정,김문철 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.12

The effect of S & Mn on the hot ductility of Fe-29Ni-17Co Kovar alloy and the mechanism of high temperature cracking occurrence were investigated. It has been found that the brittle intergranular fracture at high temperature cracking is closely associated with the sulfide along grain boundary. Experimental results showed, especially when the S content was high and the Mn content was free, that small cavities could be nucleated easily on FeS particles along grain boundary and propagated fast at high temperature. The hot ductility of Kovar alloy was drastically increased with the addition of Mn and it was also increased with decreasing S content. SEM and FE-SEM analyses showed that the Mn addition in this alloy could cause ductile intergranular fracture appearance below 1150℃ by the precipitation of MnS. It was proposed from the results that the addition of Mn and optimum S content (below 30 ppm) in Kovar alloy was necessary in order to reduce the hot cracking susceptibility.

β-CuZn 합금의 인장 및 파괴 거동에 미치는 변형률 속도와 온도의 영향

이기안,이종수 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.12

A series of tensile tests were carried out on a B2-type b-CuZn alloy in the temperature range, room temperature to 400oC at three different strain rates (10^(-5) sec^(-1), 10^(-4) sec^(-1), 5.2x10^(-2) sec^(-1)). The stress-strain curves could be divided into three types. Type I indicates a remarkably linear sustained work hardening to fracture, type II work hardening and subsequent necking, type III yield drop behavior and stress saturation, respectively; corresponding to the insensitive yield stress region, anomalous yield stress region, and yield stress decreasing region, in the yield strength vs. temperature graph. The ultimate tensile strength basically decreased as temperature increased, only showing characterized strength hump-up region just below T_(p). The fracture mode was changed mainly from transgranular at room temperature to intergranular at high temperatures. The elongation increases with increasing temperature in region I, and then slightly decreases in region II (anomalous yield stress region). When the specimens were tensile-fractured at high temperatures (region III, above Tp), the elongation drastically increased with decreasing strain rate, for instance from 12% at 5.2x10^(-2) sec^(-1) to 87% at 10^(-5) sec^(-1). The dependence of ductility on strain rate was mainly attributed to the thermally activated <100> dislocation climb, inducing stress relief at the grain boundaries, as evidenced by microvoids at grain facets.

非特異性 PHOSPHATASE에 關한 硏究 : 사람 胎盤 Alkaline Phosphatase의 燐蛋白 燐酸水解活性에 關하여

李民化,安鳳煥,李起榮,曺仲東 全南大醫大 1980 전남의대학술지 Vol.17 No.2

몇가지 작물중 침투성 살충제 Carbofuran의 잔류량 분석

이재구,최신종,경기성,안기창,권정욱 충북대학교 농업과학기술연구소 1999 農業科學硏究 Vol.16 No.-

In order to ascertain the safety of the systemic insecticide carbofuran - treated crops. garlic, peanut and potato were collected randomly from markets near the major producing farms and analyzed for the residues of carbofuran and its main metabolite, 3-hydroxycarbofuran. The in vitro metabolism of carbofuran in phosphate buffer extracts of the crops was investigated. The results obtained were as follows. 1.The recoveries of carbofuran and 3- hydroxycarbofuran from the spiked samples were 92~ 100% in all samples. The detection limit and minimum amount of carbofuran detected were 0.02ppm and 0.1ng, and those of 3-hydroxycarbofuran 0.06ppm and 0.3ng, respectively. 2.Two mature garlic samples out of 20 contained 0.13 and 0.07ppm of carbofuran, respectively, showing a detection frequancy of 10%. The residue level was less than the maximum residue limit(0.5ppm) set by the health authorities in Korea. Only one mature garlic sample out of 20 contained 0.13ppm of 3-hydroxycarbofuran. 3.The residues of carbofuran and 3-hydroxycarbofuran in the immature garlic, peanut and potato samples were less than the detection limits. 4.The application of carbofuran to the fields of garlic, peanut and potato would be safe, considering that the estimated maximum acceptable daily intake of carbofuran from garlic was 0.0007mg which is 0.13% of the maximum acceptable daily intake(0.55mg) . 5.Carbofuran was hydrolyzed in vitro mainly to carbofuran phenol(m/z 164) in phosphate buffer extracts of the three crops in contrast to the major oxidative metabolism in situ. The amount of the metabolite increased with the incubation time.

질화 분위기에서 결정화 된 Fe_(73.5)Si_(13.5)B_(9)Cu₁Nb₃ 연자성 합금의 자기적 성질

이기선,박인수,이기안,김문철,장석훈 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.11

Amorphous Fe_(73.5)Si_(13.5)B_(9)Cu₁Nb₃ alloy was crystallized in nitriding atmosphere of mixture gas of NH₃ and hydrogen. The crystallization at 823K showed the high electrical resistivity ranging from 494 to 538 mW-cm, which was higher level compared with nano-crystalline Fe_(73.5)Si_(13.5)B_(9)Cu₁Nb₃ alloy with a resistivity of about 110 mW-cm. Through the nitridation treatments, the amorphous alloy was transformed into nano-sized crystalline Fe3Si including iron nitrides such as γ' -Fe₄N phases. EPMA-concentration depth profiles confirmed an existence of nitrogen-rich region on the surface of the alloy ribbon, leading to the preferential formation of g -Fe4N phase. The formation of γ' -Fe₄N phase leaded to an increase of the resistivity and provided stable permeability and a low core loss at high frequency.