• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.341-344
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• 2008

The complicated helical flow formed in the regenerative turbomachines is usually decomposed into a peripheral component and a circulatory component. On the basis of the momentum exchange theory, the circulatory flow plays a critical role of imparting angular momentum to the peripheral flow. Therefore, the accuracy of performance prediction is dominated by the circulatory flow modeling. Until now the circulatory flow has been accounted of a standstill flow normal to the peripheral flow. However, the circulatory path from the impeller exit to the re-entrance inlet is exposed to the adverse pressure gradient, so it would be more realistic to describe that the circulatory flow is formed on the skewed plane not perpendicular to the peripheral flow. Present study suggests new circulatory flow loss model including the effect of adverse pressure gradient and modifies the effective circulatory flow rate and circulatory pivot which were previously published.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.322-324
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• 2004

Up to the present, digital replantation patients has appealed different symptoms due to blood circulatory failure. But, the level of blood circulatory failure has been evaluated only by clinical symptoms, or angiography. According to the cases of digit replantation is increasing, then objective evaluation methods of the level of blood circulation failure is needed other than patient's subjective symptoms and complaints. Although angiography, doppler, electromagnetic flowmeter, laser blood flowmeter, mechanical blood flowmeter has been used for the evaluation of the blood circulatory failure, the result was affected by time, place, surrounding temperature, patient's body temperature, and even emotion. Therefore, it is pointed out with lack of availability, feasibility and reproducibility. Thus, we compared digital blood flow of dominant hand to non dominant hand, and replanted fingers to opposite normal fingers from developed photo-plethysmography. The average digital blood flow showed no difference in normal digits each other, but, replanted digits showed average of 53% (9 - 100 %) compare to opposit normal digits. As it measure relative blood flow for circulatory failure of tissue such as fingers and toes more sensitively, reliably. In conclusion, it is expected that photo- plethysmography will be very useful for diagnosis, curative effect, prognosis of blood circulatory failure in digital replantation patient.

• 대한기계학회논문집B
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• 제28권10호
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• pp.1238-1246
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• 2004

Momentum exchange theory has been generally used for an analysis of the regenerative turbomachines due to its direct description of the complicate circulatory flow. However, because its application is limited only to linear region and its model equations are incomplete on three variables, it needs further refinements. In the present study it is improved by introducing a central pivot of circulatory flow. Also, by assuming linear circulatory velocity distribution, mean radii of inlet and outlet flows through the impeller are newly suggested. By applying control volume analysis to both linear region and the acceleration region, the governing equation on the circulatory velocity is derived. As a result, systematic performance analysis on the entire region of the incompressible regenerative turbomachines can be carried out based on the proposed model equations.

• International Journal of Fluid Machinery and Systems
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• 제8권1호
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• pp.46-54
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• 2015

Thrust-ring-pump is a kind of extreme-low specific speed centrifugal pump with special structure as numerous restrictions from thrust bearing and operation conditions of hydro-generator units. Because the oil circulatory and cooling system with thrust-ring-pump has a lot of advantages in maintenance and compactness in structure, it has widely been used in large and medium-sized hydro-generator units. Since the diameter and the speed of the thrust ring is limited by the generator set, the matching relationship between the flow passage inside the thrust ring (equivalent to impeller) and oil bath (equivalent to volute) has great influence on hydrodynamic performance of thrust-ring-pump. On another hand, the head and flow rate are varying with the operation conditions of hydro-generator units and the oil circulatory and cooling system. As so far, the empirical calculation method is employed during the actual engineering design, in order to guarantee the operating performance of the oil circulatory and cooling system with thrust-ring-pump at different conditions, a collaborative hydrodynamic design and optimization is purposed in this paper. Firstly, the head and flow rate at different conditions are decided by 1D flow numerical simulation of the oil circulatory and cooling system. Secondly, the flow passages of thrust-ring-pump are empirically designed under the restrictions of diameter and the speed of the thrust ring according to the head and flow rate from the simulation. Thirdly, the flow passage geometry matching optimization between thrust ring and oil bath is implemented by means of 3D flow simulation and performance prediction. Then, the pumps and the oil circulatory and cooling system are collaborative hydrodynamic optimized with predicted head-flow rate curve and the efficiency-flow rate curve of thrust-ring-pump. The presented methodology has been adopted by DFEM in design process of thrust-ring-pump and it shown can effectively improve the performance of whole system.

• 대한의용생체공학회:의공학회지
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• 제36권6호
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• pp.264-270
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• 2015

A mock circulatory loop system has been developed to construct a simulator for trainees in cardiopulmonary bypass systems or to simulate a test environment for cardiac-assist devices. This paper proposes a computerized mock circulatory loop system whose node is modularized by using a servo control flow regulator to simulate dynamic change of the hemodynamic status. To observe the effect of time-varying resistance, one with hemodynamic properties, the proposed system replicates the planned cross-sectional areas of the outlet of a ventricular assist device in terms of voltage input of a servo valve. The experiment is performed (1) for steady-input commands of selected area sizes and (2) for dynamic commands such as monotonous increase and decrease, and oscillatory functions of the voltage input, and a computer program based on LabVIEW (National Instruments, Austin, USA) processes every measured data and control command to the servo valve. The results show that the pressure and flow at the target points with respect to time-varying resistance match intuitive estimation: the pressure at the outlet and the pressure drop between both sides of the valve increased and the flow at the outlet decreased for increased resistance.

• 대한한의학회지
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• 제19권1호
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• pp.251-270
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• 1998

The effects of Gamigunshimtang on the isolated perfused ischemic heart in rats, heart rates, left ventricular pressure, cardiac blood flow and cardiotoxicity were stu.died in H9C2 myoblast cell, myocardial slice culture The results were as follows: 1. The administration of Gamigunshimtang to the rat recovered effectively heart rate, left ventricular pressure and flow rate from the experimental ischemia in perfused rat heart. The release of lactic dehydrogenase after the ischemia also decreased compared to the control group. 2. The administration of Gamigunshimtang to H9C2 myoblast culture enhanced the cell proliferation and protected against doxorubicin and allylamine induced release of the lactic dehydrogenase into the culture medium. It also protected effectively against doxorubicin and allylamine induced decrease of Ca ATPase activity and the increase of NADPH-cytochrome C reductase activity in the microsome. 3. The administration of Gamigunshimtang to the rat myocardial slice culture protected effectively against doxorubicin and allylamine induced decreases of protein synthesis and ATP content, and increases of cvtosolic enzyme, creatin kinase into the medium and lipid peroxidation.

• 대한기계학회논문집B
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• 제23권3호
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• pp.408-418
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• 1999

Incompressible flow inside a circular cylinder Including periodically oscillating free surface waves was studied primarily by using a numerical method. We developed a finite difference scheme based on the MAC method applicable to three-dimensional free-surface flows, and applied it to the present flow model to study tho flow characteristics as well as the fluid stirring. To verify the validity of our scheme, we performed a simple experiment for flow visualization. We found that the numerical results show a reasonable agreement with the observed flow patterns.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.266-268
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• 2011

We present a mathematical model of left heart governed by the partial differential equations. This heart is coupled with a lumped model of the whole circulatory system governed by the ordinary differential equations. The immersed boundary method is used to investigate the intracardiac blood flow and the cardiac valve motions of the normal circulation in humans. We investigate the intraventricular velocity field and the velocity curves over the mitral ring and across outflow tract. The pressure and flow are also measured in the left and right heart and the systemic and pulmonary arteries. The simulation results are comparable to the existing measurements.

• 제어로봇시스템학회논문지
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• 제4권3호
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• pp.315-320
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• 1998

In this paper, we present the PID control method for the controlling flow rate of highly complicated nonlinear Left Ventricular Assist Device(LVAD) with pneumatically driven mock circulatory system. Beat Rate (BR), Systole-Diastole Rate (SDR) and flow rate are used as the main variables of the LVAD system. System modeling is completed using the neural network with input variables (BR, SDR, their derivatives, actual flow) and an output valiable(actual flow). Then, as the basis of this model, we perform the simulation of PID control to predict the performance and tendency of the system and control the flow rate of LVAD system using the PID controller. The ability and effectiveness of identifying and controlling a LVAD system using the proposed algorithm will be demonstrated through computer simulation and experiments.

• 멤브레인
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• 제5권1호
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• pp.35-43
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• 1995

이산화탄소를 포함하는 기체혼합물의 분리를 위해 액체막을 기반으로 하여 관련된 많은 연구가 시도되어 왔다. 폐가스로부터 이산화탄소를 분리하기 위해 본 연구에서는, 흡수제(absorbent)가 흡수(absoption)모듈과 전공조작식 탈착(desorption)모듈간을 계속 순환하는, 보다 개선된 형식의 순환식 중공사 막흡수기(circulatory HFMA)를 새로이 구성하고 분리성능에 관한 기초적인 해석을 하였다. 기-액 물질전달 모델식에 수치해를 적용하여 중공사 막 내부에서의 액상에 대한 농도분포를 정량적으로 예측하였고, 순환하는 흡수제의 유속에 따른 투과플럭스와 선택도의 변화거동을 살펴보았다. $CO_{2}/N_{2}$ 원료혼합기체와 흡수제로서 반응이 없는 순수(pure water)에 대해 계산을 수행하였다. 결과로 흡수제의 유량이 증가함에 따라 투과플럭스는 증가하는 반면에 종전 방식에 비해 졸은 값을 나타낸 선택도의 경우는 점차 감소하였다. 한편 투과플럭스는 진공조작변수인 탈착모듈에서의 기상압력($p_{4}$)에 크게 좌우됨을 보았다. 기존의 평판형 막모듈과의 비교로부터 예상했던 바와 같이 본 연구에서의 중공사 막모듈이 우수한 투과율을 나타냄을 확인할 수 있었다. Circulatory HFMA의 실제 설계를 위한 기초해석이 본 연구가 갖는 의의이다.