• Journal of Biomedical Engineering Research
• /
• v.8 no.2
• /
• pp.161-170
• /
• 1987

A new type of motor-driven total artificial heart system with a rolloing-cylinder mechanism has been developed. The prototype system consists of a brushless DC motor inside of a rolling-cylinder, two arc shaped pusher-plate s, and two ventricles of smooth, seamless polyurethane sacs. The motor-driven pump has the advantages of being portable and quiet compared to the present air-driven pump. It can also be controlled more accurately. This rolling-cylinder type electromechanical pump has several structural advantages including small size and weight, as compared to other research groups' motor-driven pumps. The results of mock circulation tests confirm sufficient pump output capacity(cardiac output . 9 L/min, at aortic pressure'120mmHg, with heart rate . 120 BPM) for animal implantation of our prototype system.

• 제어로봇시스템학회:학술대회논문집
• /
• 1993.10a
• /
• pp.383-391
• /
• 1993

In this paper, a new automatic cardiac output control algorithm without any pressure sensors for the motor-driven electromechanical total artificial heart(TAH) was developed using motor current information. In the previous studies, many transducers were utilized to obtain informations of hemodynamic states for the automatic cardiac output control. But. such automatic control with sensors has some problems. To solve these problems, I proposed a new "sensorless" automatic cardiac output control algorithm providing the adequate cardiac output to the time-varying physiological demand without right atrial collapse. In-vitro tests were performed to evaluate the performance of a new algorithm and it satisfied the basic three requirements on the pump output response through the mock circulation tests.

• 제어로봇시스템학회:학술대회논문집
• /
• 1991.10a
• /
• pp.758-761
• /
• 1991

Using one chip microcontroller 87Cl96 (On chip EPROM type) and EPLD (Erasable & Programable Logic Device), an implantable control system to drive pendulum type electromechanical total artificial heart was developed. This control system consists of 4 parts, main management system, motor driver with power regulator, state monitoring system and communication part. The main system has the functions for speed detection, PI(proportional and integration) control, PWM generation, communication and analog data processor. Two kinds of power system were used and separated by 8 photo coupler arrays to improve the system stability. The performances of each compartments were compared with our previous z80 microprocessor based control system and good correspondences was shown. Logic power consumption was reduced to a one third of our previous controller. Using mock circulation tests, the overall performances of control system are evaluated.

• 제어로봇시스템학회:학술대회논문집
• /
• 1995.10a
• /
• pp.509-513
• /
• 1995

A microcontroller-based DC motor control system for a total artificial heart(TAH) was developed. Using a one-chip microcontroller, 87Cl96KB, the design of digital motor speed control system and servo control system is demonstrated. Functionally, the control system consists of a position control unit, a speed control unit, and a communication unit. The performance and the reliability of the developed control system were assessed through a series of mock circulation system experiments.

• Journal of Biomedical Engineering Research
• /
• v.19 no.3
• /
• pp.291-296
• /
• 1998

A new mechanical heart valve prosthesis has been designed appling systematic design methodology. The function of the heart valve was defined, and search for design variation has been carried out according to the functional structure, Optimal model among the various variations was determined in view of the design specificationn. Proto type valve was fabricated and test has been carried out using a mock circulation system. It has been observed that the pressure profile, cardiac output and behavior characteristics are generally satisfactory.

• Proceedings of the Acoustical Society of Korea Conference
• /
• autumn
• /
• pp.131-134
• /
• 1999

This paper considers the acoustical characteristics of the mechanical valve employed in the Korean type Artificial Heart. $Bj\"{o}rk-Shiley$ tilting disc valve was chosen for the study and acoustic measurements were performed for the artificial heart operated in a mock circulation system as well as implanted to an animal as a Bi Ventricular Assist Device (BVAD). In the mock system, three different conditions of the valve were examined which were normal, damaged (torn off), pseudothrombus attached. Microphone measurements for the BVAD were carried out at a regular time interval for 5 days after the implantation operation. Of the recorded acoustic emissions from the artificial heart, click sounds mainly originated from the valves were further analyzed using Multiple Signal Classification (MUSIC) for estimating their spectral properties. It was shown that the spectral peaks below 4 kHz and the optimal order number for MUSIC, equivalent to the number of the spectral component, might be the key parameters which were highly correlated to the physiological states of the valve like the mechanical damage of the valve or the formation of thrombus on the valves.

• Journal of Korean Elementary Science Education
• /
• v.26 no.3
• /
• pp.276-285
• /
• 2007

The purpose of this study was to observe five teachers' science classes and analyze the patterns of their analogies. To analyze the data, investigator triangulation was used, and the results were as follows: First, among the patterns of analogy used, expressions of similes and metaphors were utilized by all the teachers; teachers with over ten years' experience used adult's daily phrases, and teachers with under ten years' experience tended to use anthropomorphism. Regarding pictorial analogies, these manifested themselves in the sixth period, while teachers with over ten years' experience drew a simple picture about circulation of water, teachers with under one year's experience made additional materials for their analogy and they put an emphasis on the concept of the circulation itself. Teachers tended to use analogs according to their interests; teachers who majored in science education used pictorial analogies for further study. Second, the patterns emerging from the correspondence of the analogy manifested themselves in all the teachers equally, but they have no relation to the teacher's background. Third, routine analogy and artificial analogy appeared equally in consideration of degree of artificiality among the patterns of the analogies used. Regarding routine analogy, most teachers tended to look for analogs from things and experiences from themselves or their own backgrounds rather than those of the students. Regarding artificial analogies, teachers tended to purposely choose analogs to help students to understand; energetic teachers sometimes failed to choose appropriate analogs because they approached the topic with too much intensity. While a teacher who lacked experience and interest in science used many expressions of analogy, a teacher who felt some degree of constraint rarely used expressions of analogy. Fourth, most of the teachers used analogs familiar to their own experiences but students often found understanding these analogs difficult. Therefore, teachers need to make greater efforts to utilize analogs which are especially familiar to students when they attempt to explain science concepts.

• Proceedings of the KOSOMBE Conference
• /
• v.1998 no.11
• /
• pp.249-250
• /
• 1998

In this study, we modeled moving-actuator type Total Artificial Heart (TAH) with cardiovascular system as a form of electric circuit. The bronchial circulation, important for the imbalance between the left cardiac output and the right one, was considered and added to the model. In the model, the relations of hemodynamic variables, just as blood pressures, volumes, or flow rates of each part of body, can be expressed as simultaneous first order ordinary differential equations. To solve the equations by the numerical analysis, Runge-Kutta forth order approximation method was adopted. The simulation software (SimTAH), implemented in C++ as a window-based application program, was developed to display the hemodynamic variables and to receive control inputs from users. SimTAH was evaluated by comparison of the simulation results with the results of mock-circulation tests, in vitro.

• Journal of Chest Surgery
• /
• v.20 no.3
• /
• pp.458-472
• /
• 1987

A heart supplies bloods of about 15, 000 liters to each human organ in a day. A normal function of heart valves is necessary to this act of heart. The disease of heart valve develops to a narrowness of a closure, resulting in an abnormal circulation of bloods. In an attempt to eliminate the affliction of heart valves, the operation method to repair with artificial heart valves has been developed and saved numerous patients over past 30 years. This replacement operation has been performed since early 1960`s in Korea, but all the artificial heart valves used are imported from abroad with very high costs until recent years. The artificial heart valve using pyrolytic carbon has been developed at KAIST, which was proved to be stable in the mechanical performance and durability. Therefore, the in viva performance of this valve was examined through animal tests. The artificial heart valves used in this study are tilting disc type valves, in which the disc were made of graphite coated with pyrolytic carbon and the cages were made of titanium. In viva testings of these valves were performed in 12 dogs, in which right ventriculo-pulmonary arterial [Croup I] or inter-aortic [Croup IV] valved conduit was implanted using polytetrafluoroethylene conduits containing KAIST valve and aortic valve [Group II] or pulmonary valve [Croup III] was replaced by a KAIST valve with a 21mm or 19mm tissue annulus diameter. In group I and II, pre-and post-operative transvalvular pressure gradient was measured and compared with other prosthetic valves. During post operative period laboratory examination was performed including hemoglobin, hematocrit, red cell count, white cell, lactic acid dehydrogenase and platelet. The eight surviving dogs were sacrificed and autopsy was performed at 2, 6, and 8 weeks. KAIST valve has low transvalvular gradient and relatively high orifice area. Average ventriculo-aortic peak systolic transvalvular gradient was 14 mmHg in 21 mm valve and 19 mmHg in 19 mm valve. The valve has slight intravascular hemolysis effect. Thrombogenic effect of low polishing quality and eddy currents around small orifice is high. The valve has vulnerability of disc movement. These animal tests suggest that the improvement of the heart valve design, surface polishing state and prescription methods.

• Journal of Biomedical Engineering Research
• /
• v.26 no.5
• /
• pp.337-341
• /
• 2005

Blood pulsation has been reported to have an advantageous effect on extracorporeal blood circulation. However, the study of pulsatile blood flow in renal replacement therapy is very limited. The in-vitro experimental results of pulsatile blood flow on ultrafiltration, when compared with the conventional roller pump, are described in this paper. Methods: Blood flow rate (QB) and transmembrane pressure (TMP) were considered as regulating factors that have an influence on ultrafiltration. Experiments were performed under the condition of equal TMP and OB in both pulsatile and roller pump groups, Several kinds of hollow fiber dialyzers were tested using distilled water containing chemicals as a blood substitute. Mean TMP (mTMP) varied from 10 to 90mmHg while the QB was 200ml/min. Results: Ultrafiltration rate (QUF) was found to be linearly proportional to TMP, whereas QB had little influence on QUF. In addition, QUF was higher in the pulsatile group than the roller pump group at the identical TMP. Conclusion: In the controlled test, QUF increased solely as a consequence of blood pulsation, which implies that the pulse frequency represents an additional and important clinical variable during renal replacement therapy.