AZ91D 합금의 기계적 특성에 미치는 유지온도 및 전단변형속도의 영향

박훈모,남태운 漢陽大學校 工學技術硏究所 1999 工學技術論文集 Vol.8 No.1

본 논문은 낮은 밀도, 높은 비강도, 우수한 기계 가공성, 진동 흡수성, 치수 안정성 등으로 인하여 크게 주목받고 있는 경량금속인 AZ91D합금의 레오캐스팅(Rheo casting)시 유지온도와 전단변형속도등의 공정변수가 재료의 미세조직과 인장강도와 경도등의 기계적 특성에 미치는 영향에 대하여 고찰하였다. 그 결과 교반에 의해 수지상정(dendrite)이 파쇄되고 구형화됨을 관찰할수 있었고, 교반속도가 증가함에 따라 입자간의 응집을 파괴하는 전단응력이 증가하여 초정입자의 크기가 감소하고 β상(Mg17Al12)의 입계석출이 증가함을 알 수 있었다. 또한 온도가 낮고 교반속도가 증가할수록 입자미세화와 β상의 석출 중가로 인하여 경도는 증가하였으나, 입계에 주로 석출하기 때문에 인장강도와 항복강도, 연신율은 감소하였다. In this study, the rheocasting solidification process was applied in the production of AZ91D alloy with low density, high strength, good castability, and damping capacity. Changes of microstructure and mechanical properties with different holding temperature and shear strain rates were investigated. Dendritic α-phase was fragmentated by stirring, the size was decreased with increasing shear strain rate, and precipitation of Mg17Al12 phase was increased with decreasing holding temperature and increasing shear strain rate. In tensile test, U.T.S and Y, S were decreased while hardness was increased with decreasing holding temperature and increasing shear rate. This tendency of mechanical properties was closely related with the behavior of Mg17Al12 phase.

이차원 입 ·출구를 갖는 직육면체 공간내로 평행유동 유입시 형성되는 유동장에 관한 연구

이창훈,박운진 한국기술교육대학교 2001 論文集 Vol.8 No.1

Abstract The flowfields generated by a parallel flow into rectangular hexahedral enclosures with a two-dimensional inlet and outlet were studied both numerically by use of FLUENT (CFD package) and experimentally in a wind tunnel at Reh=3.16X103 and 6.32X103 to obtain basic data required for optimal design of air ventilation systems. By varying the size of 2-D outlet and freestream velocity, the flow pattern generated in enclosure models did not sensitively changed within the range of measurements and simulations. Large recirculation regions were identified by both experiments and CFD simulations in enclosure models just downstream of a 2-D inlet, under the direction of main stream formed diagonally between an inlet and an outlet. In general, both results of experiments and simulations were reasonably well matched each other for the prediction of mean velocity profiles in enclosure models except some minor mismatches in details.

고속 패킷 스위치 설계를 위한 향상된 윈도우 기법

김훈,정운석,박광채 조선대학교 에너지.자원신기술연구소 1999 에너지·자원신기술연구소 논문지 Vol.21 No.1

Output buffered switch structure and common buffered switch structure have many problems to design the high speed packet switch, but input buffered switch has more characteristic than these two method before. but the input buffered switch using the initial stage FIFO(First In First Out) memory structure has pointed the throughput limitation to the percent of 58.6 due to HOL(Head of Line) blocking, and give the difficulty to control system in proceeding the priority of majority and the complicated cell scheduling. HOL blocking is the result of FIFO queueing principle using the input buffered switch, and can reduce by using the window policy. In this paper, to design the high speed packet switch we gained the improved throughput, the compatible fairness and the ease of implementation by using the common buffered in DBP(Dedicated Buffer with Pointer) method, one of the window policy, in input buffered switch structure.

이차원쐐기형 칼만 와류발생기의 후류 유동장에 대한 실험적 연구

백남영,이창훈,박운진 한국기술교육대학교 2000 論文集 Vol.7 No.1

The wake flowfields behind 2-D wedge-type Karman vortex generators were experimentally studied in a wind tunnel at Red=1.89×103 and 3.78×103 to obtain basic data required for the optimal design of air-flow sensors (AFS) utilized in automotive systems. The wake generated by an isosceles triangular wedge became stabilized along the downstream direction slightly faster than those of by equilateral triangular wedges in a near wake region. The momentum thickness of the wake generated bur an isosceles model was slightly thicker than those of by equilateral models. It was revealed that the variance of Strouhal number vs. Reynolds number was not sensitive to the shapes of the wedge-type vortex generators. Strouhal number of the wakes behind wedge models was observed in the range of 0.205〈St〈0.215 and nearly invariant as the change of Reynolds number in the range of 6×102〈Red〈1×104.

Caspase 9 promoter polymorphisms and risk of primary lung cancer

Park, Jae Yong,Park, Jung Min,Jang, Jin Sung,Choi, Jin Eun,Kim, Kyung Mee,Cha, Sung Ick,Kim, Chang Ho,Kang, Young Mo,Lee, Won Kee,Kam, Sin,Park, Rang Woon,Kim, In San,Lee, Jae-Tae,Jung, Tae Hoon IRL Press 2006 Human molecular genetics Vol.15 No.12

<P>Caspase-9 (CASP-9) is an initiator CASP in the apoptosome-driven apoptosis pathway and plays an important role in the development and progression of cancer. Polymorphisms in the promoter region of the <I>CASP-9</I> gene may influence the promoter activity of this gene, thereby modulating susceptibility to lung cancer. To test this hypothesis, we examined the association of four polymorphisms [−1263A>G, −905T>G, −712C>T and −293_−275delCGTGAGGTCAGTGCGGGGA (−293del)] in the <I>CASP-9</I> promoter with the risk of lung cancer in a Korean population. The <I>CASP-9</I> genotypes were determined in 432 lung cancer patients and 432 healthy controls that were frequency-matched for age and gender. The −1263 GG genotype was associated with a significantly decreased risk of lung cancer compared with the −1263 AA genotype or combined −1263 AA+AG genotype [adjusted odds ratio (OR)=0.64, 95% confidence interval (95% CI)=0.42–0.98, <I>P</I>=0.04 and adjusted OR=0.67, 95% CI=0.46–0.97, <I>P</I>=0.01, respectively]. For the −712C>T polymorphism, individuals with at least one −712T allele were at a significantly increased risk of lung cancer compared with those harboring the −712 CC genotype (adjusted OR=1.42, 95% CI=1.06–1.89, <I>P</I>=0.02). Consistent with the results of genotype analyses, the −1263G/−712C (G-C) haplotype was associated with a significantly decreased risk of lung cancer [adjusted OR=0.59, 95% CI=0.47–0.75, <I>P</I> and Bonferroni corrected <I>P</I> (<I>P</I><SUB>c</SUB>)<0.001]. Moreover, the risk of lung cancer decreased in a dose-dependent manner as the number of the G-C haplotypes increased (adjusted OR=0.60, 95% CI=0.45–0.81, <I>P</I>=0.0007 and <I>P</I><SUB>c</SUB>=0.0014 for the G-C heterozygotes and adjusted OR=0.34, 95% CI=0.17–0.68, <I>P</I>=0.0023 and <I>P</I><SUB>c</SUB>=0.0046 for the G-C homozygotes; <I>P</I><SUB>trend</SUB><0.001). The promoter assay revealed the G-C haplotype to have a significantly higher promoter activity than the −1263G/−712T and −1263A/−712C haplotypes. These results suggest that <I>CASP-9</I> promoter polymorphisms affect <I>CASP-9</I> expression and contribute to genetic susceptibility to lung cancer.</P>

Longer capsule endoscopy operation time increases the rate of complete examination of the small bowel.

Park, Jeong Youp,Kim, Hee Man,Choi, Yun Ah,Jeon, Tae Joo,Oh, Tae-Hoon,Kim, Chang Hoon,Youn, Young Hoon,Bang, Seungmin,Kim, Hyung Gil,Lee, Don Haeng,Shin, Yong Woon,Song, Si Young G. Thieme 2010 Hepato-gastroenterology Vol.57 No.101

<P>BACKGROUND/AIMS: Wireless capsule endoscopes (CEs) have become a useful diagnostic tool for small bowel diseases, but they may fail to examine the entire small bowel. We analyzed the clinical experience of the MiRo CE in patients with suspected small bowel disease to assess whether longer operation time could increase the complete examination rate of the small bowel and diagnostic yield. METHODOLOGY: A total of 96 patients with suspected small bowel disease received CE examination at 4 tertiary hospitals in Korea. The recorded information was uploaded to a computer and analyzed by the physicians responsible for each patient. RESULTS: The average total capsule operation time was 11 hours and 39 minutes (range: 5 hours 18 minutes approximately 12 hours). In 87 (90.6%) out of 96 cases, the CE was able to explore the entire small bowel. In 32 cases (33.3%), it took more than 8 hours to reach the cecum. Capsule retention occurred in 2 cases (2.1%). The CE found meaningful small bowel lesions in 62 (64.6%) out of 96 total cases. CONCLUSIONS: A CE with a long operation time had more chance to explore the entire small bowel even in patients with suspected small bowel disease.</P>

7-(3-Benzyloxypropyl)apigenin, A Novel Cytotoxic Flavone Derivative

Park, Kwang-Su,Kim, Jin-Young,Lee, Chae-Woon,Park, Ji-Sook,Park, Hyung-Soon,Chong, You-Hoon Korean Chemical Society 2007 Bulletin of the Korean Chemical Society Vol.28 No.10

Efficacy of Steroid Treatment in Logopenic Variant Primary Progressive Aphasia with Sjögren's Syndrome

Woon Yeong Park,Sang Hoon Kim,Sang Hag Park,Eun Hyun Seo,Seung Gon Kim,Ju Chang il,IL Han Choo 조선대학교 의학연구원 2014 The Medical Journal of Chosun University Vol.39 No.4

Primary progressive aphasia (PPA) is a progressive degenerative disorder that primarily affects language. Although the etiology of PPA has not been determined, autoimmune mechanism is known to be one possible pathophysiology. We investigate efficacy of steroid treatment in a patient diagnosed as both logopenic variant PPA and Sjögren's syndrome. After steroid treatment, her cognitive function, especially language ability showed improvement. And also, FDG-PET showed metabolic increase in the bilateral temporal lobe. However, on reassessment after stopping steroid treatment, her cognitive performance declined to pretreatment level.

Phosphate uptake and growth characteristics of transgenic rice under high phosphate soils

Woon-Ha Hwang,Soo-Kwon Park,Tackmin Kwon,Sais-Beul Lee,Min-Hee Nam,Doh-Hoon Kim,Dong-Soo Park 한국육종학회 2012 한국육종학회 심포지엄 Vol.2012 No.07

Farmers have use phosphate fertilizer to provide sufficient yields. However, overuse of phosphorus accumulate in soil and causes soil and water pollution. We evaluated the phosphate acquisition and growth characteristics of OsPT1 transgenic rice (OsPT1-OX, over-expressing the high affinity phosphate transporter 1) in high phosphate soils with different level of nitrogen fertilizer treatment to investigate removing ability of excessive phosphate from soil. OsPT1-OX had shorter culm length but more tillers than those of wild-type plants in each soil conditions. Phosphate content per dry weight of OsPT1-OX was 1.8 times higher than that of wild-type under control fertilizer treated conditions. Although the dry weight of OsPT1-OX was not different from that of wild-type plants, whole plant phosphate content was 1.7 times higher than that of wild-type plants under control fertilizer conditions. Tiller number and phosphate content per dry weight of wild-type plants increased following high levels of phosphate application but did not change by following additional nitrogen application. Tiller number and phosphate content per dry weight of OsPT1-OX did not change under the high phosphate condition, but increased following nitrogen application under similar conditions. Whole plant phosphate content was highest under high nitrogen and high phosphate application conditions. These results suggest that OsPT1-OX may reduce phosphate content in soils containing excess phosphate and may be further effective under high nitrogen condition.

유방암의 수신자판단특성곡선(ROC) 분석에 의한 정량적 Tc-99m Tetrofosmin Scintimammography의 진단적 정확도

박상현,박흥규,한상훈,이영돈,정민,이태훈,오재환,이정남,이운기,박연호,민승기,백정흠,김종호,황경훈 한국유방암학회 2004 한국유방암학회지 Vol.7 No.1