• Journal of Sensor Science and Technology
• /
• v.22 no.5
• /
• pp.364-368
• /
• 2013

Vibrational energy harvester based on piezoelectricity has been expected to be the dominant energy harvesting technology due to the advantages of high conversion efficiency, light weight and small size, night operation, etc. Its commercialization is just around the corner but the integration with power management electronics should be solved in advance. In this paper, therefore, fully-integrated design environment for piezoelectric energy harvesting systems is presented to assist co-design with the power management electronics. The proposed design environment is capable of analyzing the energy harvester including the package-induced damping effects and simulating the device and its power management electronics simultaneously. When the developed design environment was applied to the fabricated device, the simulated resonant frequency matched well with the experimental result with a difference of 2.97% only. Also, the complex transient response was completed in short simulation time of 3,001 seconds including the displacement distribution over the device geometry. Furthermore, a full-bridge power management circuit was modeled and simulated with the energy harvester simultaneously. Therefore the proposed, fully-integrated design environment is accurate and fast enough for the contribution on successful commercialization of piezoelectric energy harvester.

• Journal of Biomedical Engineering Research
• /
• v.24 no.2
• /
• pp.121-126
• /
• 2003

The purpose of this work was to assess and quantify whether the beneficial effects in long-term gas exchange at exciting frequency were obtained at different frequencies as well and then to develop a vibrating intravascular lung assist device(VIVLAD), for Patients suffering from acute respiratory distress syndrome(ARDS) or chronic respiratory problems. We investigate the optimal condition of the frequency band excited with new vibrator at state of limit hemolysis when blood hemolysis came to through a membrane vibration action. The experimental design and procedures were given for a device used to assess the effectiveness of membrane vibrations. Quantitative experimental measurements were performed to evaluate the performance of the device . and to identify membrane vibration dependence on blood hemolysis. We developed an analytical solution for the hydrodynamics of flow through a bundle of sinusoidally vibrated hollow fibers that is used to provide some insight into how wall vibrations might enhance the performance of the VIVLAD. In the result, it was measured that the effect of various excited frequencies in gas transfer rate and hemolysis from the maximum gas transfer rate at no vibration when the maximum gas transfer rates showed at module type 6, module type 6 consisted of 675 hollow fiber membranes The maximum oxygen transfer rate was caused by the occurrence of maximum amplitude and transfer of vibration to hollow fiber membranes when it was excited by the frequency band of 7Hz at each blood flow rate. because this frequency became the End mode resonance frequency of the flexible in blood flow. Also, when module type 6 was excited at an excited frequency of 7Hz. blood hemolysis was low. Therefore, we decided that the limit of hemolysis frequency is 7Hz . because maximum amplitude occurred at this frequency.

• Journal of Chest Surgery
• /
• v.32 no.12
• /
• pp.1065-1077
• /
• 1999

Background : Ventricular assist devices(VADs) are being used for patients in postcvardiotomy cardiogenic shock status bridge to cardiac transplant settings and in post-myocardial infarction cardiogenic shock. The VAD which was developed at the Deparment of medical engineering in Dankook University College of Medicine was a pneumatically driven device and can maintain pulsatile flow. The goal of this study is to develop animal experimental models using the VAD and to clarify the reliability and hemodynamic property adequacy of end organ perfusion durability and severity of thrombotic-hemolytic tendency of the device. Material and Method : The pneumatic VAD was applied to 8 adult female lambs, We examined some hemodynamic parameters such as arterial blood pressure pulmonary capillary wedge pressure(pcwp) pulmonary artery pressure(PAP) left atrial pressure hour urine output cardiac index VAD flow EKG to determine the reliability of the VAD and hemodynamic compatibility of the experimental animals within 24 hours of experiment. We also observed the end organ perfusion durability of the VAD and thrombotic-hemolytic property of the VAD after 24 hours of VAD insertion. Result: We could monitor all hemodynamic parameters including pcwp PAP cardiac index EKG, adn hour urine as true clinical settings. We observed that the reliability of the VAD was excellent and the hemodynamic property of the experimental animal and end organ perfusion were adequate within 24 hours of experiment. In four lambs surviving 24 hours after insertion the reliability of the VAD and end organ perfusion were excellent and no thrombotic-hemolytic tendency was noted. However after 15 days of experiment the diaphragm of the VAD was torn and it was recommende that the durability of the VAD should be extended. Conclusion : e conclude that the pneumatic VAD developed at Dankook University Biomedical Engineering has good hemodynamic property and low thromboembolic tendency and presents adequate end organ perfusion but we noted that the durability of the device should be expanded further. It will be possible to do more reliable experiment in the future according to the animal experimental method developed in this study especially with the heart failure models.

• Korean Chemical Engineering Research
• /
• v.49 no.2
• /
• pp.230-237
• /
• 2011

In this study, the characteristic of fluid flow in the new type lung assist devices has been established using computational fluid dynamics(CFD). For the modeling, the hollow fiber was ignored, and vertical types and tangential types were used for the model. Which was to analyze the flow characteristics of the fluid flow model when there exists 1 and 2 input/output ports, and when the input/output ports is located at the center of the cylinder and at the tangential direction with the cylinder wall. The modeling results showed that it was possible to eliminate no-flow region(stagnant layer) as shown in the vertical type when an inlet and an outlet were installed on the tangential direction of the cylinder as shown in the tangential type. Also, in the tangential type, vortex-type flow appeared as dominant, and it showed a complicated flow not deviated to one side. When the number of input/output was two, there was no deviated flow, and complicated flows were generated all across the tube. From the test result, it was found that input/output of flow was tangential type and complicated flows with no stagnant layer would be generated when there are two inputs/outputs, respectively.

• Journal of Biomedical Engineering Research
• /
• v.30 no.1
• /
• pp.23-33
• /
• 2009

It can be used easily to reduce rehabilitation and treatment time if diagnostic and therapeutic devices are attached to cloth or body. Therefore we developed neuromuscular wearable ultra-miniature lighting modules which can improve the neuromuscular function and verified its clinical effectiveness. The system is based on the ultra-miniature lighting treatment module and there are two types of systems. One of them is designed as an attached type and the other type is combined with clothing. The wearable ultra-miniature lighting module is composed of controller (battery, MCU, bidirectional transmitter and receiver), cable, treatment medium generating device and other peripheral devices. To verify the clinical effectiveness of this device, we observed the difference of the strength of a muscle before and after 650nm and 25mW laser irradiation on the reflex point for 1 to 4 seconds. Among 48 patients having the degenerative osteoarthritis, the muscle strength before and after irradiation of laser was $21.8{\pm}7.99$ and $27.3{\pm}8.43$. According to the result, the muscle strength after treatment was significantly increased (p<0.01). To whom having difficulty in visiting to OPD(Out-Patient Department), doctors medically examine the patients and find the therapeutic point, attachment of this wearable ultra-miniature lighting module can function as self treatment (treating instrument) and treatment assist at home. If doctor can remotely control the patient and take part in treatment, the therapeutic device could contribute to prevention and care device.

• The Journal of the Convergence on Culture Technology
• /
• v.8 no.6
• /
• pp.405-411
• /
• 2022

Korea's long-term care insurance for the elderly, which started in 2008, is a borrowed one from gaeho insurance, which started eight years earlier. Both countries have a policy of welfare equipment benefit systems to support the lives of the elderly who are intellectually and mentally weakened. In this study, we attempted to compare and examine the welfare equipment items in Korea with those in Japan and find out the characteristics of the items in Korea and Japan. In Korea, loitering-detection device, posture changing devices, and incontinence underwears were registered as welfare devices before Japan, and in Japan, automatic urine disposal systems, wheelchair electric assist device, position converters, and lifts for handicapped person were designated as welfare devices before Korea. In addition, the Japanese Ministry of Health, Labor and Welfare has announced the designation of the excretion prediction support device as a welfare device. If Korea and Japan cooperate to develop welfare equipment items together, it will be of great help in improving the quality of life of the elderly in both countries in a super-aged society.

• Journal of Chest Surgery
• /
• v.40 no.3 s.272
• /
• pp.168-179
• /
• 2007

Background: The recent trend of an increasing number of patients with acute cardiogenic shock or chronic congestive heart failure following myocardial infarction, as well as the considerable number who can not be weaned from cardiopulmonary bypass after open heart surgery, call for immediate efforts to develop affordable ventricular assist devices that are suitable for the Korean physique. Recently, a pneumatic pulsatile ventricular assist device (VAD), named DKUH-75, has been developed by the Department of Biomedical Engineering, in collaboration with the Department of Thoracic and Cardiovascular Surgery of Dankook University College of Medicine. The feasibility of the DKUH-75 VAD was evaluated on the bases of common hemodynamic variables and echocardiographic measurements in pigs, which are subjected to an acute cardiogenic shock state following myocardial infarction, using a novel coronary artery ligation method employing the ischemic preconditioning concept. Material and Method: Acute cardiogenic shock was induced in 10 Yorkshire Landrace Duroc strain pigs by ligating the left anterior descending coronary artery via an ischemic preconditioning process. The hemodynamic variables were monitored, with epicardial echocardiographic measurements performed before and one hour after the ligation. The DKUH-75 VAD was implanted into 5 pigs one hour after the onset of the shock. The hemodynamic variables and echocardiographic measurements were taken one hour after installation of the VAD. Result: The systolic, diastolic and mean systemic arterial pressures were significantly decreased in all the experimental animals one hour after the ligation. The systolic, diastolic and mean pulmonary arterial pressures were increased (Eds note: this completely contradicts the preceding statement? However, if you mean the non-experimental animals this should be stated?). The left ventricular end diastolic pressure (LVEDP) was increased, but the cardiac index decreased, An increase in the left ventricular end systolic dimension and decreases in the fractional shortening and ejection fraction were observed all animals one hour after the coronary artery ligation. In all 5 of the VAD implanted pigs, the systolic and mean systemic arterial pressures were increased, and the pulmonary arterial pressures decreased one hour after the implantation; the LVEDP decreased, but the cardiac index was significantly increased, In the echocardiographic measurements, the left ventricular end systolic dimension decreased after the implantation of the VAD, but the fractional shortening and ejection fraction significantly increased. Conclusion: Significant improvements in the hemodynamic variables and echocardiographic measurements were observed in the 5 VAD implanted animals one hour after installation, which had been subjected to an acute cardiogenic shock state by ligation of the coronary artery, indicating that the DKUH-75 VAD could help in the recovery of the myocardial function. This suggests that the DKUH-75 VAD is feasible in the short term in relation to an acute cardiogenic shock state due to myocardial infarction.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.15 no.1
• /
• pp.39-51
• /
• 2016

In accordance to rapid aging of population, the accidents of elderly pedestrian and pedestrian safety are becoming very important issues. In terms of smartphone technologies, older people are increasingly looking for useful and friendly ICT services that which can add a value on their silver life. This paper introduced a new IT-based service for elderly walking assist using a smart-phone accompanied by a wearable watch. We describe the functional requirements and a systems architecture model with an interface between a smart-phone and wearable watch. Moreover, this study attempted to verify what services are needed and to estimate elderly pedestrians' WTP (willingness to pay) for IT-based walking assistance device. A total of 189 elderly pedestrians were randomly surveyed through face-to-face interviews. The questionnaire consisted of 3 categories: (1) questions pertaining to socio-economic status, (2) 12 questions regarding walking attitudes, and (3) a question to measure WTP. With this gathered data, factor analysis and path model estimating were conducted. The results identified the elderly user requirements and the use-value of new innovative products for IT-based walking assistance services by two groups(latent elderly and elderly). The modeling result shows that elderly's service preference would increase the possibilities for the commercialization of IT-based walking device with improving their walking safety.

• Journal of Biomedical Engineering Research
• /
• v.28 no.4
• /
• pp.569-576
• /
• 2007

Ventricular Assist Device(VAD) has switched its goal from a short-tenn use for bridge-to-transplantation to a long-tenn use for destination therapy, With this goal, the importance of long-tenn reliability gets more interests and importances, H-VAD is an portable extracorporeal biventricular assist device, and adopts an electro-pneumatic driving mechanism. The pneumatic pressure to pump out blood is generated with compression of bellows, and is transmitted in a closed pneumatic circuit through a pneumatic line. The existing pneumatic VAD adopts a air compressor which can generate stable pressures but has defects such as a noise and a size problem. Thus, it is not suitable for being used as a portable device, These problems are covered with adopting a closed pneumatic circuit mechanism with a bellows which has a small size and small noise generation, but it has defects that improper pneumatic setting causes a failure of adequate flow generation. In this study, the pneumatic pressure regulation system is developed to cover these defects of a bellows-type pneumatic VAD. The optimal pneumatic pressure conditions according to various afterload conditions for an optimal flow rate were investigated and the afterload estimation algorithm was developed, The final pneumatic regulation system estimates a current afterload and regulate the pneumatic pressure to the optimal point at a given afterload condition. The afterload estimation algorithm showed a sufficient performance that the standard deviation of error is 8.8 mmHg, The pneumatic pressure regulation system showed a sufficient performance that the flow rate was stably governed to various afterload conditions. In a further study, if a additional sensor such as ultrasonic sensor is developed to monitor the direct movement of diaphragm in a blood pump part, the reliability would be greatly increased. Moreover, if the afterload estimation algorithm gets more accuracy, it would be also helpful to monitor the hemodynamic condition of patients.

• Proceedings of the KOSOMBE Conference
• /
• v.1996 no.05
• /
• pp.84-87
• /
• 1996

We have been developed electrohydraulic left ventricular assist device and done various in vivo evaluation on the device. Through the in vivo experiment conducted from Jan. 23, 1996 to Feb. 8, we could have experience of long-term evaluation fur the first time. The sheep used in this experiment had survived for 16 days. We used new actuator with reduced size and linear motion guide replacing oil box and ball bearings. Also, we used improved blood chamber with reduced size, reduced weight facilitating fixing the chamber to animal's body, and polymer sac having improved folding pattern. Against suction problem, we used absolute pressure limiter only. Motor current for driving this new actuator was not much higher than older one. Effective stroke volume was about 48 cc. Thrombosis was found around top area and peripheral boundary of the sac and valves. There was no sign of damage from suction problem in the atrium observed at autopsy. Main cause of death was presumed to be progressive formation of thrombosis in the cannulae. In this paper, the results of this experiment are documented.