원심압축기 모형 시험의 신뢰성 향상 및 공력 성능 평가를 위한 연구

학위논문(석사)--서울대학교 대학원 :기계공학과,1997.Maste

Gender differences in spouse choice : evidence from a Korean matchmaking agency

Thesis(masters) --서울대학교 대학원 :경제학부,2008. 8.Maste

The Effects of Hydrogen Contents in Al Melt on the Porosity of Al Castings

Al 주물의 기공발생 원인을 이론적으로 규명하고, Al 용탕 중의 수소함량을 직접 측정하여 탈가스의 효과와 주물품의 미세조직변화를 관찰하였다. 그 결과, 다이캐스팅용 합금으로 많이 사용되는 Al-7.5%Si-0.4%Mg 합금에서 기공이 전혀 발생하지 않을 용탕 중의 최소수소농도는 0.1㎤/100g이며, 용탕 중의 수소는 장입물 속의 수분에 의해서라기 보다는 주로 용해 중의 분위기로부터 침투한다는 사실을 알았다. 또한 탈가스 효과는 초기 수소농도가 높을수록, 용탕의 온도가 낮을수록 더 좋다는 결론을 얻었다.We studied theoretically the formation of porosities in Al castings, and observered by experimentally the hydrogen contents in Al melts and the changes of microstructures in Al castings. As results, we know that the minimun hydrogen content which will not generate the porosity in Al-7.5%Si-0.4%Mg diecasting alloy is 0.1㎤/100g and, the hydrogen penetrates into the Al melts by the melting atmospheres rather than by the moistures in Al scrap. Also, we know the facts that the initial hydrogen contents are higher and the temperature of melts are lower, the effect of degassing is supenor.We studied theoretically the formation of porosities in Al castings, and observered by experimentally the hydrogen contents in Al melts and the changes of microstructures in Al castings. As results, we know that the minimun hydrogen content which will not generate the porosity in Al-7.5%Si-0.4%Mg diecasting alloy is 0.1㎤/100g and, the hydrogen penetrates into the Al melts by the melting atmospheres rather than by the moistures in Al scrap. Also, we know the facts that the initial hydrogen contents are higher and the temperature of melts are lower, the effect of degassing is supenor

냉압연된 78.5％ Permalloy 와 변형된 mild steel 에서의 barkhausen noise

학위논문(석사) - 한국과학기술원 : 물리학과, 1985.2, [ [iii], 78 p. ]The Barkhausen noise, its frequency spectrum and the hysteresis loops of coldrolled 78\% permalloy have been studied during magnetization cycle at different magnetizing frequencies. The hysteresis loss did not change at different magnetizing frequencies (0.05 Hz, 10 Hz and 90 Hz), but the average amplitude of Barkhausen noise was larger at higher magnetizing frequency (in the range of 0.01 - 1Hz), that is, Barkhausen noise have the tendency to be clustered more strongly at higher magnetizing frequency. The magnitude of the frequency spectrum was greatest near Hc, that is, the clustering mature of Barkhausen noise is predominant at the steepest parts of the hysteresis loop. The hysteresis loop and Barkhausen noise of deformed mild steel were measured. When the deformation became more severe, the magnetic property was harder. This is supposed to be due to the increase of dislocation densities which act as barriers to the domain wall motion, and this was confirmed by the measurement of Barkhausen noise, average amplitude of which increased when the deformation became more and more severe.한국과학기술원 : 물리학과

A solution method for the large scale production of multiwall carbon nanotubes

Large scale production of multiwall carbon nanotubes (MWCNTs) has been achieved by a solution method. A heated bubble chamber is used as a hydrocarbon source from liquid n-hexane, and a Fe catalyst precursor is prepared by Fe(CO)5 which is dissolved into the n-hexane. The temperature and dissolved Fe concentration in the n-hexane have influences on the synthesis of MWCNTs. The synthesized MWNTs are collected by an electromagnet

Characterization of Circulating IL-7R Positive Cell Populations for Early Detection of Pancreatic Ductal Adenocarcinoma

(1) Background: Pancreatic cancer is a high devastating disease with the lowest survival rate among all common cancers due to difficulties in early diagnosis. The purpose of this study was to identify and characterize the distinct subset of blood cell population elevated in peripheral blood mononuclear cells (PBMC) of pancreatic cancer to evaluate the potential markers for diagnosis of pancreatic cancer; (2) Methods: We analyzed differential gene expression in PBMC from normal individuals and pancreatic cancer patients utilizing transcriptome analysis. Flow cytometry analysis was applied to identify the discrete subset of interleukin-7 receptor (IL-7R) expressing cells in these cells. The expression of IL-7R during tumorigenesis was determined in syngeneic mouse model of pancreatic cancer in vivo; (3) Results: PBMC from pancreatic cancer patients expressed elevated IL-7R mRNA compared to healthy control individuals. IL-7R expressing cells rapidly appeared from the early stages of the onset of tumor formation in syngeneic pancreatic cancer mouse model in vivo. The discrete subset of IL-7R positive cells mainly consist of naive T, central memory T, and effector memory T cells; (4) Conclusions: Taken together, our present findings suggest that pancreatic cancer patients expressed higher level of IL-7R expression in PBMC that rapidly emerged from the onset of early pancreatic tumor formation in vivo than normal individuals. Thus, it can be used as a novel biological marker for early events of pancreatic cancer development

Continuous mass production system of carbon nanotubes synthesis and processing

High purity multiwall carbon nanotubes (MWCNTs) were synthesized by a continuous mass production apparatus using a catalyst vapor deposition method. The continuous mass production apparatus consisted of a moving heater and a gas decomposer, and this continuous mass production apparatus of carbon nanotubes shows the possibility of industrial scale production of carbon nanotubes. The MWNTs have lengths of several micrometres and diameters in the range of 20 to 60 nm with over 90% purity

Evogliptin Suppresses Calcific Aortic Valve Disease by Attenuating Inflammation, Fibrosis, and Calcification

Calcific aortic valve disease (CAVD) accompanies inflammatory cell infiltration, fibrosis, and ultimately calcification of the valve leaflets. We previously demonstrated that dipeptidyl peptidase-4 (DPP-4) is responsible for the progression of aortic valvular calcification in CAVD animal models. As evogliptin, one of the DPP-4 inhibitors displays high specific accumulation in cardiac tissue, we here evaluated its therapeutic potency for attenuating valvular calcification in CAVD animal models. Evogliptin administration markedly reduced calcific deposition accompanied by a reduction in proinflammatory cytokine expression in endothelial nitric oxide synthase-deficient mice in vivo, and significantly ameliorated the mineralization of the primary human valvular interstitial cells (VICs), with a reduction in the mRNA expression of bone-associated and fibrosis-related genes in vitro. In addition, evogliptin ameliorated the rate of change in the transaortic peak velocity and mean pressure gradients in our rabbit model as assessed by echocardiography. Importantly, evogliptin administration in a rabbit model was found to suppress the effects of a high-cholesterol diet and of vitamin D2-driven fibrosis in association with a reduction in macrophage infiltration and calcific deposition in aortic valves. These results have indicated that evogliptin prohibits inflammatory cytokine expression, fibrosis, and calcification in a CAVD animal model, suggesting its potential as a selective therapeutic agent for the inhibition of valvular calcification during CAVD progression