Study on Microstructure and Mechanical Properties of the Al–25Cr–5Si (at%) Alloy Powder Using Gas-Atomization and SPS Process

Yong‑Ho Kim,Hyo‑Sang Yoo,Jeong‑Han Lee,Ik‑Hyun Oh,Hyun‑Kuk Park,Hyeon‑Taek Son 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7

In order to investigate the microstructure and mechanical properties on Al–25Cr–5Si (at%) alloy, a mixed powder with pureelements and an alloy powder using a gas atomization process were used. Fine and high purity Al–25Cr–5Si (at%) alloypowder was successfully prepared by gas atomization and densified using a spark plasma sintering (SPS) process. The overallpowder size distribution of the mixed Al, Cr, and Si elemental powders was in the range of 10–15 μm. The atomized Al–Cr–Sialloy powder was fine and spherical in morphology and difficult to be formed by intermetallic formation. Densification wasclearly confirmed at 1000 °C, with almost isolated pores formed, by clear removal of pores between particles, deformationof particles, an increase in the number of contacts, and a change in size between particles. As a result of XRD analysis ofthe sintered compacts, single phase was observed using the mixed powder, but the compact using gas atomization remainedthe alloy phase even at the process temperature. The Vickers hardness of the compacts by mixed powder was observed at59.70 Hv and the compact using gas atomized powders on the temperature 1000 °C of the Vickers hardness increased to702.6 Hv. The compressive yield strength of the compact with mixed powder was 195.24 MPa and the compressive strengthof the compact with gas atomized powder increased to 802.07 MPa. It is considered not to be decomposed by the AlCrSi,Al13Cr4Si4and Al8Cr5phases sintering process, resulting from the improvement of mechanical properties.

γ-Alumina에 담지된 산화구리에 의한 SO_2의 제거에 관한 연구

鄭一鉉,尹龍水,全法柱 단국대학교 1992 論文集 Vol.26 No.-

In the case of SO_2 removal from the flue gases by fixed beds of coper oxide in two types or γ-Aluminas with different pore size distribution, the reactive sorption capability were correlated with not only porosity and pore size distribution in the reacting solid but impregnated concentration of the reacting solid but impregnated concentration of the copper oxide. The effect of change of pore structures on the kineticc of gas-solid reaction was investigated through the random pore model. Mathematical model og gas-solid noncatalytic reaction for the concentration vs. time relationship in corporating chemical reaction, product layer diffusion, and the effect of structural change due to chemical reaction has been derived. Numerical solution were obtained to the model equations for various values of the parameters characterizing the pore structure, effective internal diffusion, and the chemical reaction constant. From the results, the conversion was decreased cause of pore closure at the surface of reactiong particles, reduction of porosity and surface area of reaction, and increase of effective diffusion coefficient in the solid with the progress of reaction, Conversion was increased with rised concentration of flue gas since that CuO-SO_2 reaction mechanism assumed to be first order. Total conversion was strongly dependent on the local conversion at surface. According to decreas of impregnated concentration of the copper oxide and increase of the flue gases concentration, total conversion was increased. The conversion was affected by gas flow rate and pore size distribution in the reacting solid.

VES-LMC 덧씌우기를 이용한 콘크리트 포장 보수

정원경,김용곤,김기헌,윤경구 강원대학교 산업기술연구소 2005 産業技術硏究 Vol.25 No.B

Since in 1970, the length of concrete pavements(JCP, JRCP and CRCP) are growing rapidly at both of main highways and local roads. Many of them are deteriorated and old enough to be repaired or replaced. The pavement is more important than the other infrastructures and it is very difficult to go around or block the traffic during the rehabilitation. The very-early strength latex-modified concrete(VES-LMC)may offer the advantages of high-early-strength, higher flexural strength, higher bond strength, and improved durability. The VES-LMC could be used at a kind of fast track ofr early opening to the traffic after 3 hours of concrete placement. The installation of VES-LMC overlay at Jung-Boo highway was successfully done from April 28 to 29, 2005. The traffic was closed at 07:00 PM and opened to traffic at 08:30 AM. The compressive and flexural strength of VES-MC were more than 28MPa, 6.2MPa after 4 hours, respectively.

胃食道 異物의 內視鏡的 除去

정현용,이헌영,김영건 충남대학교 의과대학 지역사회의학연구소 1993 충남의대잡지 Vol.20 No.2

Gastrointestinal foreign bodies present a significant problem, causing a surprising amount of morbidity and mortality. The clinician is presented with the problem of expectant management, endoscopy, and surgery, to obtain an optimal outcome. We have assessed the efficacy of endoscopic removal in the gastroesophageal foreign body. A total 19 cases admitted at CNUH hospital from january 1991 to december 1993 were included in this treatment model and the following results were obtained : 1) The age distribution varies 10 months to 74 years old, prevalence rate under 5 years of age was 4 cases(21%). 2) Foereign bodies were :lodged in the esophagus 12 cases(normal anatomy 7 cases, benign stricture 5 cases) and in the stomach 7 cases. 3) Nature of foreign bodies was meat ball, marble, check, coin, fish bone, animal bone, video key and bean. 4) Patients with esophageal foreign body were always complained dysphagia or odynopgagia, patients with stomach foreign body were chiefly asymptomatic. 5) Accessory using in endoscopic removal were grasping forceps, alligator forceps, stone extraction baskets, polypectomy snare and laser equipment. 6) All cases were successfully removed by endoscopy, there were no complication during procedure.

石菖蒲가 血壓 및 局所腦血流量에 미치는 影響

鄭鉉雨,康城溶,白承化 대한본초학회 1999 大韓本草學會誌 Vol.14 No.2

Rhizoma Acori Graminei(RAG) has been used in Korea for many centuries as a therapeutic agent for cerebral disease. The effect of RAG on the vascular system is not known. The purpose of this study was to determine the effect of RAG on Blood Pressure(BP) and regional Cerebral Blood Flow(rCBF) of male Sprague-Dawely rats. The changes in rCBF were determinated by Laser-Doppler Flowmetry(LDF). The results were as follows : 1. Blood pressure was not affected by RAG in rats. 2. rCBF was increased by RAG in a dose-dependent manner. 3. Pretreatment with propranolol significantly inhibited RAG induced increased rCBF. 4. Pretreatment with methylen blue and ODQ significantly inhibited RAG induced increased rCBF. 5. Pretreatment with L-NNA significantly inhibited RAG induced increased rCBF. These results suggest that RAG causes a diverse response of blood pressure and regional cerebral blood flow(rCBF). The increased in rCBF is also mediated by adrenergic β-receptor, nitric oxide synthease and guanylate cyclase.

소화성 궤양 환자에 대한 염산 베넥세이트(울굿^(�)) 임상 효과

정현용,육은주,이헌영,노홍구,김영건 최신의학사 1993 最新醫學 Vol.36 No.8

소화성 궤양 환자에 대한Lansoprazole의 치료 효과

정현용,김진희 최신의학사 1997 最新醫學 Vol.40 No.6

일부 종합병원 병리조직실 공기 중 포름알데히드 농도

정규현,하안례,이용환 고신대학교 보건과학연구소 2002 보건과학연구소보 Vol.12 No.-

Formaldehyde irritiates mucous membranes in the eyes, nose, and upper respiratory tract, and it is a potential carcinogen. The purpose of this study was to assess the time-weighted average (TWA) and short-term exposure limit (STEL) concentration to formaldehyde exposure and to suggest proper improvement strategy to minimize exposure. This study was conducted at 3 histopathology laboratories in the hospitals located in Busan from January 20 to March 10, 2002. Formaldehyde and organic solvents (ethanol and xylene) were sampled by personal air sampler and analyzed by gas chromatography. The obtained results were as follows. 1. TWA concentrations of formaldehyde ranged from 0.28 to 10.64 ppm and those of two laboratories out of 3 were exceeded the threshold limit value (TLV). 2. In one laboratory, STEL concentrations was exceeded threshold limit value (TLV), as 2.39 ppm. 3. TWA concentrations of ethanol and xylene were under the TLVs. It is necessary to improve the local ventilation systems and other facilities to prevent the personnels in the laboratories from the diseases due to formaldehyde exposure.

상부위장관출혈에서 Hypertonic Saline-Epinephrine 용액 국소주사의 지혈효과

정현용,이헌영,김영건 충남대학교 의과대학 지역사회의학연구소 1990 충남의대잡지 Vol.17 No.2

We have assessed the hemostatic efficacy of endoscopic HS-E solution injection sclerosis in the upper gasrointestinal bleeding. A total 27 cases admitted to CNUH internal medicine department from november 1989 to october 1990 were included in this treatment model and the following results were obtained : 1. The causes of bleeding were gastric ulcer(44%), duodenal ulcer(25.9%), Dieulafoy's ulcer (18.5%), advanced gastric cancer(3.7%), Mallory-Weiss syndrome(3.7%) and angiodysplasia(3. 7%). 2. The locations of bleeding were high body(25.9%), angle(18.5%), bulb(18.5%), antrum(14.8%), midbody(3.7%), cardia(3.7%), pyloric canal(3.7%) and stoma(3.7%). 3. Endoscopic findings of UGI bleeding showed active bleeding in 51.9% (14/27 cases) as spurting (11.1%). pulsating(22.2%) and oozing(18.9%). Stigmatas of recent bleeding were 48.1% (13/27cases) as denuded vessels(29.6%) and fresh blood clots(18.9%). 4. The hemostatic effect of HS-E solution injection sclerosis was 92.6%(25/27 cases). The sussess rate of first injection was 70.3%(19/27), second injection 14.8% and third injection 7.4%. Two cases(7.4%) were operated for hemostasis. 5. According to bleeding types viewed endoscopically, hemostatic effects were following sussess rate ; spurting cases 67% (2/3), pulsating cases 83% (5/6), oozing 100% (5/5). Others showed 100% of sussess rates.

위암조직에서 Carcinoembryonic Antigen 측정의 의의

정현용,윤세진,이헌영,김영건 충남대학교 의과대학 지역사회의학연구소 1991 충남의대잡지 Vol.18 No.2

To estimate tumor CEA expression of stomach cancers in relation to normal mucosa CEA, degree of cellular differentiation, pathologic stage and other clinicopathologic findings, we measured CEA concentrations in tissue extracts by radioimmunoassay for 24 cases of stomach cancer. The results were as follows: 1. Ranges of tissue CEA concentrations in normal stomach mucosa was from 6.Ong/gm to 15.4 ng/gm(mean 10.2ng/gm). 2. Mean conceatrations of cancer tissue CEA was 42.1ng/gm(from 2.9 ng/gm to 414.Ong/gm), 4 times higher than normal mucosa. In 46% of stomach cancers, tissue CEA concentrations was above normal cut off value(18.7ng/gm). 3. Tiuse CEA concentrations of stomach cancer was significantly high as high CEA levels of normal mucosa(r=0.6954), not related to serum CEA concentrations. 4. Tissue CEA concentrations of stomach cancer was high as high TNM stage, but was not related to wall invasion depth, lymph node metastasis, cellular differentiation and other clinicopathologic findings. In conclusion, the production of CEA in stomach cancers was significantly increased in half cases, CEA expression of tumor was related to pathologic stage rather than cellular differentiation. The factors determined CEA production was considered more higher levels such as DNA profile. To estimate prognostic values of tissue CEA concentrations, follow up of included patients and further study should be pursued.