• Journal of Chest Surgery
• /
• v.45 no.5
• /
• pp.320-322
• /
• 2012

The percutaneous transcatheter closure of secundum atrial septal defect has recently become an increasingly widespread alternative to surgical closure in many centers. Although immediate, short, and intermediate term results of percutaneous transcatheter septal closure are promising, the procedure is not free from inherent complications that could be lethal. We report a case of device embolization necessitating emergent surgical retrieval.

• Progress in Superconductivity and Cryogenics
• /
• v.18 no.2
• /
• pp.42-47
• /
• 2016

A free-piston reciprocating expander is a device which operates without any mechanical linkage to a stationary part. Since the motion of the floating piston is only controlled by the pressure difference at two ends of the piston, this kind of expander may indispensably require a sophisticated active control system equipped with multiple valves and reservoirs. In this paper, we have suggested a novel design that can further reduce complexity of the previously developed cryogenic free-piston expander configuration. It is a simple replacement of both multiple valves and reservoirs by a combination of an orifice valve and a reservoir. The functional characteristic of the integrated orifice-reservoir configuration is similar to that of a phase controller applied in a pulse tube refrigerator so that we designate the one as a phase controller. Depending on the orifice valve size in the phase controller, the different PV work which affects the expander performance is generated. The numerical model of this unique free-piston reciprocating expander utilizing a phase controller is established to understand and analyze quantitatively the performance variation of the expander under different valve timing and orifice valve size. The room temperature experiments are carried out to examine the performance of this newly developed cryogenic expander.

• Archives of Craniofacial Surgery
• /
• v.18 no.3
• /
• pp.186-190
• /
• 2017

We report a case of free flap deterioration which may have been induced by pressure gradient resulting from cranial defect overlying a ventriculoperitoneal shunt (VP shunt). The patient, male and aged 78, had a VP shunt operation for progressive hydrocephalus. Afterwards, the scalp skin flap surrounding the VP shunt collapsed and showed signs of necrosis, exposing part of the shunt catheter. After covering the defect with a radial forearm free flap, the free flap site showed signs of gradual sinking while the vascularity of the flap remained unimpaired. An agreement was reached to remove the shunt device and observe the patient for any neurological symptoms, and after the shunt was removed and the previous cranial opening filled with fibrin glue by Neurosurgery, we debrided the deteriorated flap and provided coverage with 2 large opposing rotational flaps. During 2 months' outpatient follow-up no neurological symptoms appeared, and the new scalp flap displayed slight depression but remained intact. The patient has declined from any further follow-up since.

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.3 s.168
• /
• pp.29-37
• /
• 2005

In this study, the control of the free surface deformation of a magnetic fluid for the change in electromagnetic force is discussed. The free surface of magnetic fluid is formed by the balance of surface force, gravity, pressure difference, magnetic normal pressure and magnetic body force. Magnetic fluid in characteristics of fluid adjusted to the opposite direction of the gravity direction. Thus, the device of a magnetic fluid proposed the complete zero-leakage sealing, oscillator for surface control, boundary layer control, MHD, flow control, flow using magnetic levitation system and surface actuator. This study show the deformation of surface rise due to the intensity of the magnetic field and possibility of two-dimensional control of magnetic fluid through the feedback data of hall sensor.

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.5
• /
• pp.180-188
• /
• 2003

In the precision motion device, the frictional problem by mechanical friction causes serious effects on the system performance. Various researches have been executed to solve this problem, but classical fluid lubrication method has some disadvantages in precision motion under clean environment. Therefore, the magnetic bearing and contact-free systems have been focused on with its pollution-free characteristics. In this paper, we treat modeling and analysis of electromagnets not only for magnetic bearing but also fer contact-free electromagnetic actuators. Three types of electromagnet for various applications are modeled and analyzed by magnetic circuit theory and the validity is verified by experiments.

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.7
• /
• pp.91-98
• /
• 2003

In the field of precision manufacturing demanding high positioning performance, the mechanical friction in positioning device deteriorates the quality of the product and increases the cost of production for positioning devices. Therefore, we propose a contract-free linear actuator using active magnetic bearing. The structure and operating principle of the proposed system are explained, and the magnetic forces are analyzed by magnetic circuit theory to design magnetic bearings and linear actuator. With the derived equation of motion, the stability is identified. Experimental results are presented to show the feasibility.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.29A no.10
• /
• pp.8-16
• /
• 1992

Despite recent advances in electrical switch architectures, the practical switch performance is limited by both the technological and physical constraints of electrical device and wiring. Though an optical switch can have good features, optical devices are of poor quality. Therefore, we propose and study the switching architecture based on free-space optical interconnections and electrical logic devices. And an exchanging method using packets with a parallel form is introduced to solves the blocking problem of the switch that resulted from switching packets with a serial form. The free-space optical interconnections overcome the defects of electrical switch, such as, the complex connections of the wires. The proposed and demonstrated switch is nonblocking, simple and high performable. Other attractive features of the proposed switch include the guarantee of first-in first-out packet sequence. In this thesis, we also discuss the performance of proposed switch and show the experimental results of the 4$\times$4 switch.

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.10
• /
• pp.47-55
• /
• 2003

In the development of positioning device for precision manufacturing and measuring, the friction from mechanical contact causes serious decrease of performance. In this study, we studied about variable reluctance type contact-free linear actuator to overcome drawbacks from friction. In the view of electromagnetics, we analyzed and derived theoretical magnetic force equation and designed structure for generating suspension and propulsion force simultaneously. In the view of dynamics, we derived equation of motion and identified the stability of the system. Finally, we verified the feasibility of the proposed system.

• Archives of Craniofacial Surgery
• /
• v.15 no.3
• /
• pp.121-124
• /
• 2014

The use of the implantable Doppler device eases the burden of free flap monitoring, and allows caregivers to notify healthcare personnel of a potential vascular event. A 24-year-old female patient underwent anterolateral thigh adipofascial flap surgery to provide a buried flap on the left temporal area for a depressed and infected skull wound. The author was able to salvage the flap from two venous occlusions, which was made possible by early notifications from the caregiver who reported changes in the Doppler signal.

• Korean Journal of Computational Design and Engineering
• /
• v.22 no.2
• /
• pp.181-189
• /
• 2017

In this paper, we develop a human error-free wire connection guide system. The only related work is Japanese patent by Hitachi. The patent is guiding the wire connection using PC server. And no implementation details have been reported publicly. We propose a new method based on smart mobile devices. The proposed methods are registered as two Korean patents. We implement a prototype wire connection guide system to verify the patents. Through human experiments, we verify the system can reduce the human error more than 90% and speed up the connection process more than twice faster than working without the system. To be used in the industrial fields, the prototype system needs more product packaging works.