• Journal of Korean Neurosurgical Society
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• v.48 no.4
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• pp.367-370
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• 2010

We present a case of posterior atlantoaxial screw-rod fixation in a patient with an aberrant vertebral artery (VA) course combined with bilateral high-riding VA. An aberrant VA which courses below the posterior arch of the atlas (C1) that does not pass through the C1 transverse foramen and without an osseous anomaly is rare. However, it is important to consider an abnormal course of the VA both preoperatively and intraoperatively in order to avoid critical vascular injuries in procedures which require exposure or control of the VA, such as the far-lateral approach and spinal operations.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.3
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• pp.134-138
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• 2005

A typical conventional systems of a linear motion use rack and pinions or ball screws to convert rotary motions from DC servo motors. A linear motor has been used a several field for a MEMS technology and a aircraft carrier. We have studied a transient response of a linear actuator with a damping ratio, spring constant and a pressed power for a constant stroke control.

• Journal of Korean Neurosurgical Society
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• v.49 no.2
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• pp.128-130
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• 2011

The low lumbar spine is deeply located in flexible segments, and has a physiologic lordosis. Therefore, burst fractures of the low lumbar spine are uncommon injuries. The treatment for such injuries may either be conservative or surgical management according to canal compromise and the neurological status. However, there are no general guidelines or consensus for the treatment of low lumbar burst fractures especially in neurologically intact cases with severe canal compromise. We report a patient with a burst fracture of the fourth lumbar vertebra, who was treated surgically but without fusion because of the neurologically intact status in spite of severe canal compromise of more than 85%. It was possible to preserve motion segments by removal of screws at one year later. We also discuss why bone fusion was not necessary with review of the relevant literature.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1513-1518
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• 1996

A force reflecting hand controller can be used to provide more realistic information to the operator of a teleoperation system such as kinesthetic feedback from a slave robot. In this paper, a new design concept of a force reflecting 6-DOF hand controller utilizing the kinematic structure of a Stewart Platform is presented. Based on the optimal design technique of a Stewart Platform, a force reflecting hand controller has been designed and constructed to verify the technical feasibility of proposed design concept. In order to provide an operator with kinesthetic feedback information, a force mapping algorithm based on a reciprocal product of screws has been introduced. Finally, the technical feasibility of the design concept has been demonstrated through some of experimental results of the device under virtual environment on a real-time graphic system.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.11
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• pp.987-994
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• 2000

A Linear Pulse Motor (LPM) is a direct drive motor that has good performance in terms of accuracy, velocity and acceleration compared to the conventional rotating system with toothed belts and ball screws. However, since an LPM needs supporting devices which maintain constant air-gap and has strong nonlinearity caused by leakage magnetic flux, friction and cogging, etc., there are many difficulties in improvement on accuracy with conventional control theory. Moreover, when designing the position controller of LPM, the modeling error and load variations has not been considered. In order to compensate these components, the neural network with conventional feedback controller is introduced. This neural network of feedback error learning type changes the current commands to improve position accuracy. As a result of experiments, we observes that more accurate position control is possible compared to conventional controller.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.39 no.2
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• pp.90-93
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• 2013

Mandibular fractures in infants are rare. This case report describes management of a mandibular fracture in an 11-month-old infant using a microplate and screws with open reduction. The surgical treatment was successful. Because the bone fragments were displaced and only the primary incisors had erupted, conservative treatment, such as an acrylic splint and circummandibular wiring, was not recommended. Nine weeks after surgery, the microplate was removed. The results showed complete clinical and radiological bone healing with normal eruption of deciduous teeth.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.33 no.4
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• pp.397-400
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• 2007

In an open reduction of the mandibular angle fracture, it is crucial to approximate each fracture segment as closer as possible for the reduction of the healing period. In this case report, we proposed a new technique for the mandibular angle fracture. This was designed to minimize the gap between two separated segments using mini-implants and surgical wires. Mini-implants were placed around the fracture line, followed by wire ligation to minimize the fracture gap. And then internal fixation was easily employed with plates and screws. The advantages of this technique were reduced time for operation, the promotion of healing, rapid functional recovery, and few complications.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.785-790
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• 2001

Linear motors can drive a linear motion without intermediate gears, screws or crank shafts. Linear motors can successfully replace ball lead screw in machine tools, because they have a high velocity, acceleration and good positioning accuracy. On the other hand, linear motors emit large amounts of heat and have low efficiency. In this paper, heat sources of a synchronous linear motor with high velocity and force are measured and analyzed. To improve the thermal stiffness of the linear motor, an insulation layer with low thermal conductivity is inserted between cooler and machine table. Some effects of the insulation layer are presented.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.4
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• pp.22-32
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• 2001

One of the important considerations in designing a machine tool is the durability. In this study, a durability estimation system for horizontal machining centers is developed to evaluate the effects of structural specification and driving condi-tions on the durability. All loads such as weights, inertial forces, cutting force and so on, are automatically transferred from the upper elements to the lower elements by the force flows which can be derived from the structural code of horizontal machining centers. And the external loads applied to the motion elements such as bearings, LM guides, ball screws and ao on, are determined by the equilibrium conditions of force and moment. Especially, the durability of horizontal machining centers is estimated based on the lifes of motion elements operating under the desired driving conditions.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.4
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• pp.97-103
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• 2001

The study on the high-speed machine tool is very important for the improvement of productivity since it can shortens cutting and non-cutting time. Especially, high speed of feed drive system is the major research field. In the industries of the advanced countries, the feed drive systems at the speed of 60 m/min have been already developed based on the high lead ball screws. In this study, a high speed feed drive system at the speed of 60 m/ min has been developed, and its movements characteris-tics are investigated. As the movement characteristics, positioning accuracy, angular accuracy, straightness and micro step-response are measured. Thermal characteristics of the system is also discussed. For measuring the movement characteris-tics, a laser interferometer, a memory-based Hi-coder and a cooling device are used. The experimental results confirm that the movement characteristics and the thermal behavior of the system are satisfactory in the aspect of accuracy and stability.