• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.2
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• pp.6-11
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• 2010

For the purpose of reducing the energy consumption in the house heating, the various devices have been developed. One of these is to control the flow in the heat pipe and the flow control valve using shape memory alloy(SMA) spring is proposed in our study. The proposed house heating system is to save the gas consumption and the remote control system is designed for the convenience of using the proposed valve. The developed valve consists of SMA spring, disk, return spring, and regulation handle. The regulation handle is for supplying the additional hot water and is controlled by remote-control-motor. In order to design the remote control system, the Zigbee wireless communication protocol is used. The performance of the proposed valve structure is shown through the experimental result.

• Smart Structures and Systems
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• v.3 no.2
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• pp.189-200
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• 2007

As a functional material, shape memory alloy (SMA) has attracted much attention and research effort to explore its unique properties and its applications in the past few decades. Some of its properties, in particular the electrical resistance (ER) based self-sensing property of SMA, have not been fully studied. Electrical resistance of an SMA wire varies during its phase transformation. This variation is an inherent property of the SMA wire, although it is highly nonlinear with hysteresis. The relationship between the displacement and the electrical resistance of an SMA wire is deterministic and repeatable to some degree, therefore enabling the self-sensing ability of the SMA. The potential of this self-sensing ability has not received sufficient exploration so far, and even the previous studies in literature lack generality. This paper concerns the utilization of the self-sensing property of a spring-biased Nickel-Titanium (Nitinol) SMA actuator for two applications: ER feedback position control of an SMA actuator without a position sensor, and estimation of the opening of a SMA actuated valve. The use of the self-sensing property eliminates the need for a position sensor, therefore reducing the cost and size of an SMA actuator assembly. Two experimental apparatuses are fabricated to facilitate the two proposed applications, respectively. Based on open-loop testing results, the curve fitting technique is used to represent the nonlinear relationships between the displacement and the electrical resistance of the two SMA wire actuators. Using the mathematical models of the two SMA actuators, respectively, a proportional plus derivative controller is designed for control of the SMA wire actuator using only electrical resistance feedback. Consequently, the opening of the SMA actuated valve can be estimated without using an extra sensor.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.8
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• pp.79-87
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• 1999

In this study, a new type of flow control valve which is SMA actuated flow control valve is presented. The flow control valve is actuated by a small motion of shape memory alloy. The performance of this valve as a position control component is analyzed by computer simulation. A variable structure control technique is applied for the position control by the flow control valve. The position control performance of the valve is evaluated on the step responses of a PID control by a electrohydraulic servo valve. For the simulation study, first, the mathematical model of a hydraulic system, which is consisted of the flow control valve and a hydraulic cylinder, is formulated. This mathematical model and the designed variable structure control algorithm are then combined by the MATLAB software. The same sequence of work is carried out for the PID position control system with a electrohydraulic servo valve. The simulation results show the validity of the new type of flow control valve as a variable position control component.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1055-1060
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• 2009

Noise is one of the major environmental problems in human life. But hot water distributers with the flow rate control valve bring about often noise according to the heating control condition in residential buildings. The sound power level increased as the flow rate and pressure difference increased. And thus, experimental analyses for the flow rate control and the pressure difference control were carried out in this study to reduce the noise emitted from the flow rate control valve. As the results, the flow rate control method using a SMA(Shape Memory Alloy)-valve and the flow rate control system using a pressure difference sensor can be expected to control noise in the region of below 50 dB of sound power level.

• Journal of Chest Surgery
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• v.51 no.3
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• pp.209-212
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• 2018

Superior mesenteric artery (SMA) aneurysms are rare and often fatal. A 72-year-old man had previously been admitted to the emergency room with epigastric pain and heart murmur. The echocardiographic diagnosis was vegetation on the aortic and mitral valves, with moderate regurgitation from both valves due to infective endocarditis. No aneurysm was detected on abdominal computed tomography, and emergency double-valve replacement was performed. On postoperative day 25, the patient experienced abrupt abdominal pain, and computed tomography revealed a mycotic SMA aneurysm. Open surgical repair of the SMA aneurysm was performed using the femoral vein, and the patient's postoperative course was uneventful.

• Journal of Chest Surgery
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• v.39 no.7 s.264
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• pp.527-533
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• 2006

Background: A retrospective study was conducted to analyze the results of St. Jude Medical mitral valve replacement at the Chonbuk National University Hospital since the initial implant in May 1984. Material and Method: Between May of 1984 and December of 1996, 95 patients underwent MVR with the St. Jude Medical mechanical valve prosthesis at Department of Medical Science of Chonbuk National University Hospital and follow-up ended in May of 2004. Result: Age ranged from 19 to 69 years. Follow-up (mean${\pm}$standard deviation) averaged $10.6{\pm}4.2\;year$. Thirty-day operative mortality was 4.2% (4/95). Nine late deaths have occurred and actuarial survival was $90.5{\pm}3.0%,\;87.9{\pm}3.4%\;and\;83.2{\pm}4.6%$ at 5, 10 and 20 years, respectively. Probability of freedom from valve-rotated death was $95.5{\pm}2.1%,\;94.3{\pm}2.4%\;and\;91.0{\pm}3.9%$ at 5, 10 and 20 years, respectively. Seven patients have sustained thromboembolic events (1,05%/patient-year). Fifteen patients had anticoagulation related hemorrhage (3.56%/patient-year). There was no structural valve deterioration. Probability of freedom from all complications was $82.0{\pm}3.9%,\;71.3{\pm}4.8%\;and\;42.4{\pm}10.5%$ at 5, 10 and 20 years, respectively. Conclusion: We confirm the effective and excellent durability of the St. Jude Medical prosthesis in the mitral position with a low event rate at long-term follow-up. It also demonstrates the commonly encountered practical difficulty of adjusting the anti-coagulation protocol in patients with prosthetic mitral valves.