• Journal of KSNVE
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• v.6 no.2
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• pp.187-196
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• 1996

A new control strategy to actively control the vibration of a very flexible single link manipulator is proposed and experimentally realized. The control scheme consists of two actuators; a motor mounted at the beam hub and a piezoceramic bonded to the surface of the flexible link. The control torque of the motor to produce a desired angular motion is firstly determined by employing a sliding mode control theory on the equivalent rigid dynamics. The torque is then applied to the flexible manipulator in order to activate the commanded motion. During the motion, underirable oscillation is actively suppressed by applying a feedback control voltage to the piezoceramic actuator. Consequently, the desired tip position is favorably accomplished without vibration. Measured control responses are presented in order to demonstrate the efficiency of the proposed control methodology.

• Journal of Ocean Engineering and Technology
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• v.10 no.4
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• pp.128-140
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• 1996

To analyze a formation process of the soots in spray flame in the combustion chamber, an optically accessible DI Diesel engine was used for visualization. The images of the flames and soots were visualiaed with high speed camera by Schlieren method and Light extinction method. The spray flame and soot images on the films were analyzed at the various engine operating conditions. Soot distributed widely in spray flame and its concentration was about $100g/m^3$ at the position close by nozzle tip of spray flame region, however it decreased below $20g/m^3$ at the corner of combustion chamber due to soot oxidation.

• Journal of Technologic Dentistry
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• v.15 no.1
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• pp.63-72
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• 1993

The following results were come out after the careful study on the rational application of dental surveyor in the clinic 1. The adequate path of placement satisfying guiding plane, retention non-interference and esthetics. 2. The location of clasp arm and the accurate under cut position and amount of clasp tip can be judged. 3. In case that the model needs to be mounted to the surveyor, the exactly same location can be attained by the means of the tripoding. 4. The unnecessary undercut areas in the path of placement and removal car be corrected. 5. The surveyor is essential in manufacturing dental prosthesis and it can also carry out all sorts of prospective designs In terms of the diagnosis and treatment.

• Journal of Industrial Technology
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• v.19
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• pp.15-23
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• 1999

Active damping system is generally used for the vibration suppression and precise motion control for the flexible structure. This application can be easily found on the space structure and driving mechanism of optical storage devices. Although a control system using the flexible structure has many advantages over using rigid mechanism in driving energy saving, system weights, and etc., more complex and precise control strategies are required. A position control system using flexible structure and the concept of active damper is designed and manufactured, which is driven by slide DC motor and moving coil motor located at the tip of the flexible beam. Dynamic characteristics of this system are investigated by analytic and experimental ways. By the comparison of those two results, a nominal reference model for this system is proposed.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1778-1783
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• 2008

A compact and two-dimensional atomic force microscope (AFM) using an orthogonal sample scanner, a calibrated homodyne laser interferometer and a commercial AFM head was developed for use in the nanometrology field. The x and y position of the sample with respect to the tip are acquired by using the laser interferometer in the open-loop state, when each z data point of the AFM head is taken. The sample scanner which has a motion amplifying mechanism was designed to move a sample up to $100{\times}100{\mu}m^2$ in orthogonal way, which means less crosstalk between axes. Moreover, the rotational errors between axes are measured to ensure the accuracy of the calibrated AFM within the full scanning range. The conventional homodyne laser interferometer was used to measure the x and y displacements of the sample and compensated via an X-ray interferometer to reduce the nonlinearity of the optical interferometer. The repeatability of the calibrated AFM was measured to sub-nm within a few hundred nm scanning range.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.304-309
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• 2000

Strain gage method is used to evaluate the mode I dynamic stress intensity factor of marging steel(18Ni) and titanium alloy(Ti-6A1-4V). To decide the best strain gage position on specimen, static fracture toughness test was performed. Then instrumented charpy impact test and dynamic tensile test was performed by using strain gage method for evlauating dynamic stress intensity factor. Strain gage signals on the crack tip region are used to calculate the stress intensity factors. It is found that strain gage method is more useful than method by using load which is obtained from impact tup to assess dynamic characteristics such as dynamic stress intensity factor.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.971-976
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• 1996

A flexible pointing system mounted on top of a vehicle suffers from performance degradation due to bending vibrations as the vehicle runs on a bump course. In order to improve the pointing performance, the pointing structure's vibrations should be suppressed. In this paper, a nonlinear controller is designed to control the tip position of the pointing system while actively suppressing the vibrations. To cope with high order dynamics and nonlinearities of the plant and hydraulic actuating system, a two-stage sliding mode controller is devised. The desired actuating pressure is obtained in the first stage and then the in put current In the hydraulic servo system is computed to generate the pressure. The simulation results show the effectiveness of this scheme and improvements in pointing accuracy.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.71-74
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• 2012

Generally, tone noise is generated at the rotary wing and helicopter. BVI(Blade-Vortex Interaction) noise is one of the helicopter's tone noise. The BVI noise is governed by tip-vortex characteristics such as vortex size, strength and trajectory. To avoid BVI, many methods have been developed and proposed. In this paper, rotating blade with active tab was numerically investigated to reduce BVI noise. For flow and noise simulation, the lifting surface approach and the acoustic analogy were used. Using numerical methods, the noise directivity and maximum noise position were predicted.

• The Korean Journal of Pain
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• v.12 no.1
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• pp.128-131
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• 1999

Stellate ganglion block is a well established method for the management of certain pain syndromes (e.g., chronic regional pain syndrome, facial pain) in the cervicothoracic region and upper extremity. The stellate ganglion resides between the C7 transverse process and the head of the first rib. Anesthetic injections for the stellate ganglion block are typically made at the level of the transverse process of either the C6 or C7 vertebrae to avoid the pleura, vessels, and nerve roots. Method of positioning the needle tip directly at the ganglion has been described, but are problematic because of the risk of injury to or injection into adjacent structures. It is necessary to know the exact anatomic position of the stellate ganglion when permanent blockade is required by means of radiofrequency thermocoagulation. Whereas fluroscopy shows only bony feature, computerized tomography also images nerves, vessels, and lung, allowing accruate needle placement. We report a case of the percutaneous radiofrequency thermocoagulation of the stellate ganglion after computerized tomography-guided localization.

• The Korean Journal of Pain
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• v.2 no.2
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• pp.181-188
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• 1989

Neurolytic splanchnic nerve block is an effective method for the relief of pain of upper abdominal cancer. Nine cases of intractable upper abdominal cancer pain were treated by splanchnic nerve block with absolute alcohol (25 ml) at the pain clinic of Kangdong Sacred Heart Hospital, Hallym University, during a 19 month period from March, 1988 to September, 1989. The group included six patients with stomach cancer, two patients with pancreatic cancer, and one patient with hepatobiliary cancer. We used fluoroscopy in all cases of alcohol spianchnic nerve block to determine both, the position of the needle tip, and the spread of the neurolytic solution. Of the 9 patients, 6 patients had excellent pain relief, and 3 patients who had combined upper abdominal and lower back pain had relieved upper abdominal pain only, but remaining lower back pain. Of the 9 patients', 5 patients had excellent pain relief through the patients remaining life (1-2 months) in which follow up was possible.