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초음속 터빈 익렬 앞전 형상 및 노즐-익렬 간격에 따른 유동 특성에 대한 실험적 연구
조종대,김귀순 朝鮮大學校 機械技術硏究所 2006 機械技術硏究 Vol.9 No.1
본 연구에서는 초음속 충동형 터빈의 유통특성을 알아보기 위해 소형 초음속 풍동을 설계 하였으며 Single pass Schlieren system을 이용하여 유통을 가시화하였다. 실험은 2차원 초음속 노즐과 익렬을 조합하여 블레이드 앞전 형상과 노즐-익렬 간극에 따라 실시하였다. 실험을 통해 충격파를 포함한 복잡한 유동 형태와 노즐-익렬, 충격파-경계층 상호작용 등을 관찰할 수 있었다. In this paper, a small supersonic wind tunnel is designed and built to study the flow characteristics of a supersonic impulse turbine cascade. The flow is visualized by means of a single pass Schlieren system. The supersonic cascade with 2-dimensional supersonic nozzle was tested for various blade leading edge shapes and gaps between the nozzle and cascade. Highly complicated flow patterns including shocks, nozzle-cascade interaction and shock boundary layer interactions are observed.
조종대(Jong Dae Cho),정수룡(Su Ryoung Cheong),나인균(In Gyun Na),신동건(Dong Gun Shin),박동철(Dong Chul Park),이진관(Jin Kwan Lee) 대한내과학회 1998 대한내과학회지 Vol.54 No.2
Background: A correct estimation of volume status and dry weight in dialysis patients remains a difficult clinical problem Clinical status and chest X-ray are not sensitive enough, while invasively measured central venous pressures are not routinely available. Recently, the ultrasonographic determination of the diameter and collapse index of the inferior vena cava has been proposed as a noninvasive method for estimating intravascular volume. We tried to evaluate the clinical relevance of this method in dialysis patients by comparing it with alphahuman-atrial natriuretic peptide (alpha-h-ANP) and cyclic guanosine 3:5-monophosphate (cGMP) levels. Methods: Using echocardiography, the diameter of the inferior vena cava (VCD) and its decrease on deep inspiration (collapse index : CI) were evaluated in 27 hemodialysis patients. Echocardiography of the inferior vena cava (IVC) was performed in the supine position after 10 minutes rest. The transducer was placed in the subxiphoid region and long and short axis views of the IVC were obtained just below the diaphragm in the hepatic segment. VCD was measured before the P-wave on the electrocardiogram to avoid interference with A-wave and V-wave on the venous pressure curve, and corrected for body surface area. Pre- and post-hemodialysis levels of the plasma alpha-h-ANP and cGMP were measured by radioimmunoassay. The relationship between VCD, CI determined by echocardiography, and alpha-h-ANP and cGMP concentrations were studied. Results: The levels of alpha-h-ANP and cGMP were markedly elevated before hemodialysis and significantly lower values were found after hemodialysis (alpha-h-ANP: 162.7 102.6 pg/ml vs 90.6 61.0 pg/ml, cGMP: 35.3 8.8 pmol/ml vs 21.3 6.2 pmol/ml). A significant correlation was found between VCD and alpha-h-ANP before (r=0.81, p<0.05) and hemodialysis (r=0.65, p<0.05). No such significant correlation was observed between CI and alpha-h-ANP levels. Furthermore, a significant correlation was observed between VCD before hemodialysis and the change in alpha-h-ANP during hemodialysis (r=0.64, p<0.05). The relationship between VCD and cGMP before hemodialysis was not significant (r=0.26, p>0.05) and also no relation was observed between the decrease of cGMP during hemodialysis and VCD before hemodialysis (r=0.12, p>0.05). A significant correlation between the percent change in body weight and the percent change in VCD during hemodialysis (r=0.91, p<0.05) and also significant relation was observed between the pecent change in body weight and the percent change in alpha-h-ANP levels (r=0.40, p, 0.05). Conclusion: Echocardiography of the inferior vena cava allow an estimation of changes of intravascular volume in ESRD patients without cardiac filling impairment as shown by the correlation to other indices of intravascular volume, such as alpha-h-ANP. In this study, CI and cGMP levels were less informative. Inferior vena cava echocardiography is noninvasive and easily available and serial measurements of VCD and alpha-h-ANP levels allow an estimation of chages of intravascular volume in FARD patients on maintenance hemodialysis.