• 대한족부족관절학회:학술대회논문집
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• 2008.11a
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• pp.29-29
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• 2008

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.117.5-117
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• 2002

. Mobility analysis for overconstrained mechanisms is not clearly explained. . Aims at mobility analysis of overconstrained mechanisms . Representative screws is employed as a tool . A method to identifying the representative screw is introduced . Mobility analysis for several overconstrained parallel mechanisms and mobile robots

• 대한치주과학회:학술대회논문집
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• 2006.11a
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• pp.139-139
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• 2006

• Fibers and Polymers
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• v.7 no.4
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• pp.404-413
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• 2006

This study examines multiple quality optimization of the injection molding for Polyether Ether Ketone (PEEK). It also looks into the dimensional deviation and strength of screws that are reduced and improved for the molding quality, respectively. This study applies the Taguchi method to cut down on the number of experiments and combines grey relational analysis to determine the optimal processing parameters for multiple quality characteristics. The quality characteristics of this experiment are the screws' outer diameter, tensile strength and twisting strength. First, one should determine the processing parameters that may affect the injection molding with the $L_{18}(2^1{\times}3^7)$ orthogonal, including mold temperature, pre-plasticity amount, injection pressure, injection speed, screw speed, packing pressure, packing time and cooling time. Then, the grey relational analysis, whose response table and response graph indicate the optimum processing parameters for multiple quality characteristics, is applied to resolve this drawback. The Taguchi method only takes a single quality characteristic into consideration. Finally, a processing parameter prediction system is established by using the back-propagation neural network. The percentage errors all fall within 2%, between the predicted values and the target values. This reveals that the prediction system established in this study produces excellent results.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.9
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• pp.1094-1102
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• 2011

Recent trends for the miniaturization and weight reduction of portable electronic parts is the use of subminiature components. Assembly of the miniaturized components requires subminiature screws of which pitch sizes are in a micrometer scale. To produce such a subminiature screw with high precision threads, not only a precision forming technology but also high-precision measurement technique is required. In the present work, a vision inspection system is developed to measure the thread profile of a subminiature screw. Optical simulation based on a ray tracing method is used to design and analyze the optical system of the vision inspection apparatus. Through this simulation, optical performance of the developed vision inspection system is optimized. The image processing algorithm for the precision screw inspection is also discussed.

• Journal of Korean Neurosurgical Society
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• v.42 no.4
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• pp.305-310
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• 2007

Objective : Combined antero-posterior fixation has been a standard method for bilateral interfacetal dislocation in cervical spine. The purpose of this study is to evaluate the efficacy and complication of anterior cervical stabilization in treatment of bilateral interfacetal dislocation. Methods : A total of 65 cases of traumatic bilateral interfacetal dislocation in cervical spine who were managed in our institution, from Mar. 1997 to Feb. 2006, were included in this study. Closed reduction was tried in all cases before operation. If closed reduction was accomplished successfully, only anterior cervical fixation was performed (Group I), and attempted to place screws bicortically as possible with unicortical screws. If failed, posterior open reduction with fixation was first tried, followed by anterior cervical fixation (Group II). All patients were evaluated for neurological outcome and radiological evidence of healing. Results : The Group I included 47 patients and the Group II, 18 patients. The improvement of Frankel grade and increase of mean cervical lordosis angles were not statistically different between two groups. Screw-plate system used did not influence the outcome. On follow up, solid bone fusion was evident and there were no cases of instability in both groups. Conclusion : Our study demonstrated that anterior cervical fixation on BID is safe and effective in comparison with combined antero-posterior cervical fixation.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.23 no.4
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• pp.348-356
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• 2001

The factors related to relapse in 20 skeletal class III patients who performed two-jaw surgery with Le Fort I maxillary osteotomy and bilateral sagittal split ramus osteotomy was investigated. All patients were fixed with miniplate on the maxilla and three screws at each mandible. Cephalograms taken at preoperative, immediate postoperative and 8 months postoperative after surgery were traced and digitized. 1.The horizontal and vertical relapse of maxilla and mandibular chin points was within 1mm postoperatively. Compare to the preceding report concerning the mandibular set-back surgery only group, this reveals two-jaw surgery for mandibular prognathism using rigid fixation is more stable. 2.Although there was no significant relapse tendancy was observed at chin points, the screw tip land-marks moves anterio-superiorly and each side of the screws moved as a one unit. The screw tip points moved similar direction to the masticatory force and this movements might be influenced by the muscular tension to the distal segment of the mandible. 3.According to the regression analysis, the amount of horizontal and vertical movement of mandibular set-back influenced the mandibular relapse. However, direction and amount of maxillary surgical movement did not inf1uenced the maxillary and mandibular relapse.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.17 no.1
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• pp.46-54
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• 1995

Postoperative infection following orthognatic surgery is rare. When postoperative infections occur, the initial treatment consists of incision and drainage of the affected area, culturing to identify bacterial stains and verify antibiotic sensitivity, and the institution of the appropriate antibiotic regimen. Some plates and screws may eventually require removal, the initial therapy should be attempted to retain the plates and screws until adequete healing has taken place. In orthoganthic surgery, intra-operative complications as a lesion of inferior alveolar nerve, fracture of osteomised segments, incomplete sectioning, malposition of segments, haemorrhage may occur. The surgeon should be familiar with possible complications to be caused and how to manage them. Prevention of postoperative infection following the orthognathic surgery consists of minimal periosteal reflection, aseptic management of operation field, proper surgical technique, rigid fixation, prophylactic antibiotics.

• Journal of Dental Rehabilitation and Applied Science
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• v.19 no.2
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• pp.125-137
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• 2003

The use of screw-retaind prosthesis on an osseointegrated implant is a popular treatment modality offering relative ease in the removal of the restoration. One of the complications associated with this modality is the loosening of the abutment and coping screws. Loosening of the screws results in patient dissatisfaction, frustration to the dentist and, if left untreated, component fracture. There are several factors which contribute to the loosening of implant components which can be controlled by the restorative dentist and lab technician. This article offers pratical solutions to minimize this clinical problem and describes the factors involved in maintaining a stable screw joint assembly. To avoid joint failure, adherence to specific clinical, as well as mechanical, parameters is critical. With respect to hardware, optimal tolerance and fit, minimal rotational play, best physical properties, a predictable interface, and optimal torque application are mandatory. In the clinical arena, optimal implant distribution; load in line with implant axis; optimal number, diameter, and length of implants; elimination of cantilevers; optimal prosthesis fit; and occlusal load control are equally important.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.6
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• pp.509-515
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• 2015

Recent trends to reduce the size of mobile electronics products have driven miniaturization of various components, including screw parts for assembling components. Considering that the size reduction of screws may degenerate their joining capabilities, the size reduction should not be limited to the thread region but should be extended to its head region. The screw head is usually manufactured by forging in which a profiled punch presses a billet so that plastic deformation occurs to form the desired shape. In this study, finite element (FE) analysis was performed to simulate the forging process of a subminiature screw; a screw head of 1.7 mm diameter is formed out of a 0.82 mm diameter billet. The FE analysis result indicates that this severe forging condition leads to a generation of folding defects. FE analyses were further performed to find appropriate punch design parameters that minimize the amount of folding defects.