• Journal of Korean Neurosurgical Society
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• v.39 no.3
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• pp.188-191
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• 2006

Objective : The purpose of this study is to evaluate the efficacy and necessity of combined anterior approach [discectomy and fusion] and posterior approach[open-door laminoplasty] in the treatment of cervical spondylotic myelopathy. Methods : The authors reviewed 14 cases in whom combined anterior and posterior approach performed for cervical myelopathy due to simultaneous anterior and posterior pathology such as huge central disc herniation with narrow spinal canal between January 2000 and December 2002. Clinical symptoms were evaluated by Japanese Orthopaedic Association [JOA] score and then the cervical curvature, change of spinal canal to vertebral body[SC/VB] ratio and canal widening were measured and compared to the clinical symptoms. Results : The mean JOA score increased from $10.4{\pm}3.1$ preoperatively to $14.8{\pm}1.2$ at the final follow up with a mean recovery rate 66.4%. In all cases, there were not neurologic deterioration. Mild postoperative complications developed in two cases. One patient had a limitation of range of neck motion and the other one showed kyphotic change. Postoperative radiography showed an improvement of body to canal ratios [average $0.70{\pm}0.08$ before surgery to $1.05{\pm}0.12$ after surgery and mainte nance or recovery of cervical lordosis. Canal widening of antero-posterior diameter and dimension after operation is 6.8mm. $116.61mm^2$. Conclusion : Combined anterior and posterior procedure could be helpful in decompression of the spinal cord and good functional recovery in spondylotic myelopathy patients with combined anterior and posterior pathology such as huge disc herniation accompanying narrow spinal canal.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.398-403
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• 2005

This study investigates the change of the temperature and mechanical properties of the braking disk for the railway vehicle. The average temperature is measured about $100^{\circ}C$ and the maximum temperature is measured over $200^{\circ}C$ by non-contact sensor from Seoul to Chun-an. In the $20^{\circ}C-300^{\circ}C$, the 0.2% offset yield strengths of the disk (GC25-30 material) are a little down to the reference value, but the linear relation of tensile test result is not find from the linear change of temperature. However, JIC values have the inverse proportion to the temperature, and the JIC value at $200^{\circ}C$ decrease 30.55% from the JIC. value of the room temperature. This result means that the crack length on the braking disk is rapidly increase at $200^{\circ}C$.

• Journal of Technologic Dentistry
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• v.4 no.1
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• pp.5-7
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• 1982

This study was performed to examine the effect of repeated firing on porcelain color stability. Sixty sepcimens of generally uniform size and shape(9.7 12mm)were prepared using the manufactorer's specifications and among them 50 specimens that showed no defect after firing procedure were selected. All samples, abraded with sandpaper disc, ultrasonically cleaned, and air fired to amedium glaze were devided into 10 groups according to the number of repeated firing and, upon completion, mounted on a 13 by 16cm board. 30 persons(five dentists, ten dental techanicians, and fiftheen students) were asked to compare the samples for variations, in hue, chroma and value under natural and artificial light. The results were as follows:(1) There were no color change detected in the first four firings.(2) Slight color change were noticed in subsequent firings(ie: greater decreases in value with slight increases In chroam)(3) However, the hue remained constant in all 10 groups after repeated firings.

• Journal of Oral Medicine and Pain
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• v.25 no.2
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• pp.191-203
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• 2000

This study was performed to investigate the relationship between vertical dimension during swallowing and speech pattern in patients with temporomandibular disorders. For this study, 33 patients with temporomandibular disorders(TMDs), namely, 17 patients with disc displacement with reduction and 16 patients with disc displacement without reduction, and 30 normal subjects without any signs and symptoms in the masticatory system were selected as the patient group and as the normal group, respectively. Biopak $system^{(R)}$(Bioresearch Inc., Milwaukee, USA) was used for recording of electromyographic(EMG) activity(${\mu}V$) of the anterior temporalis, the superficial masseter, the sternocleidomastoideus and the trapezius insertion muscle during swallowing, and of mandibular positional change with function time(sec.) during swallowing and speech. A sentence of 'Sue is missing her house' was used for observing of speech pattern. Comparison between the two groups and relationship of the mandibular positional change and the function time between during swallowing and during speech were analysed by SPSS windows program. The results of this study were as follows : 1. Mean EMG activity of the trapezius insertion during swallowing was higher in the patient group, and the value was $3.4{\mu}V$ in patients and $2.1{\mu}V$ in normal subjects. 2. Vertica1 dimension(VD) at mandibular rest position before swallowing was slightly higher in the patient group, but VD at swallowing-late stage and at rest position after swallowing were not different between the two groups. 3. Swallowing time were 2.1 sec. in the patient group, and 1.5 sec. in the normal group, and the difference was significant. 4. VD during speech were generally higher in the normal group. In this case, speaking position showing the most difference between the two groups was 'her' position. The distance from habitual intercuspal position to 'her' position was 4.9mm in the patient group, and 6.6mm in the normal group. Speaking time was also longer in the patient group. 5. There were no difference in all observed items between the two categories of the patient group according to reduction of disc displacement. 6. Relationship between the positional changes during swallowing and speech were different between the patient group and the normal group. And in the normal group, VD at rest position before swallowing was negatively correlated with speaking time.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.54-63
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• 2022

This paper is a study on the friction damper, which is one of the seismic reinforcement devices for structures. This study developed a damper by replacing the internal friction material with ultra high molecular weight polyethylene (UHMWPE), a type of composite material. In addition, this study applied a multi-friction method in which the internal structure where frictional force is generated is laminated in several layers. To verify the performance of the developed multi-friction damper, this study performed a characteristic analysis test for the basic physical properties, wear characteristics, and disc springs of the material. As a result of the wear test, the mass reduction rate of UHMWPE was 0.003%, which showed the best performance among the friction materials based on composite materials. Regarding the disc spring, this study secured the design basic data from the finite element analysis and experimental test results. Moreover, to confirm the quality stability of the developed multi-friction damper, this study performed an seismic load test on the damping device and the friction force change according to the torque value. The quality performance test result showed a linear frictional force change according to the torque value adjustment. As a result of the seismic load test, the allowable error of the friction damper was less than 15%, which is the standard required by the design standards, so it satisfies the requirements for seismic reinforcement devices.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.983-989
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• 2015

Power transformer is one of the major and key apparatus in electric power system. Monitoring and diagnosis of transformer fault is necessary for improving the life period of transformer. The failures caused by short circuits are one of the causes of transformer outages. The short circuit currents induce excessive forces in the transformer windings which result in winding deformation affecting the mechanical and electrical characteristics of the winding. In the present work, a transformer producing only the radial flux under short circuit is considered. The corresponding axial displacement profile of the windings is computed using Finite Element Method based transient structural analysis and thus obtained displacements are compared with the experimental result. The change in inter disc capacitance and mutual inductance of the deformed windings due to different short circuit currents are computed using Finite Element Method based field analyses and the corresponding Sweep Frequency Responses are computed using the modified electrical equivalent circuit. From the change in the first resonant frequency, the winding movement can be quantified which will be useful for estimating the mechanical withstand capability of the winding for different short circuit currents in the design stage itself.

• The Korean Journal of Nuclear Medicine
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• v.29 no.4
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• pp.511-517
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• 1995

Bone scan is a very sensitive diagnostic imaging test for detecting bone and joint disorders. So it might be useful in the diagnosis of temporomandibular disorders of the joint origin. Thus, the effectiveness of bone scan for detecting temporomandibular joint(TMJ) diseases and differentiating the TMJ disc displacement from the TMJ arthritis was evaluated. Bone scan was done in 21 patients with TMJ disc displacement(13 unilaterally affected, 8 bilaterally affected), 25 patients with TMJ arthritis(23 unilateral, 3 bilateral), and 39 volunteers with no signs, symtoms, or history of TMJ disease. TMJ simple uptake rate(SUR) and difference of both TMJ SUR were calculated from the 100,000 count lateral image of head and neck region in 99mTc MDP bone scan. Transcranial and panorama X-ray examination was also done in all patients. TMJ SUR(%) were $1.673{\pm}0.606$ in TMJs affected with arthritis, $1350{\pm}0.351$ in TMJs affected with disc displacement, and $1.084{\pm}0.172$ in TMJs of controls. Significant differences were demonstrated among them(p<0.01) Difference of bith TMJ SUR was highest in patients with unilateral TMJ arthritis($0.608{\pm}$0.533, p<001), and there is no significant difference between that of controls and that of unilateral TMJ dist displacement patients($0.062{\pm}0.063$ vs $0.122{\pm}0.100$). TMJ SUR of Joint with bone change on X-ray finding was not significantly different from that of joint with normal X-ray finding. Those in patients with unilateral TMJ disc displacement(696% and 87% vs 23.1% and 23%). The proportions of patients with increased TMJ SUR and difference of both TMJ SUR(>mean+2SD of controls) in unilateral TMJ arthritis patients were significantly higher than those in patients with unilateral TMJ disc displacement(69.6% and 87% vs 23.1% and 23%). Conclusively, bone scan nay help to detect TMJ disease and differentiate TMJ disc displacement from TMJ arthritis.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.3
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• pp.178-188
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• 2017

Purpose: We compared the effects of newly developed diode laser (Bison 808 nm Diode laser) on the treatment of peri-implantitis with conventional products (Picasso 810 nm Diode laser) by comparing the surface temperature of titanium disc and bacterial sterilization according to laser power. Materials and Methods: The titanium disc was irradiated for 60 seconds and 1 - 2.5 W using diode laser 808 nm and 810 nm. The surface temperature of the titanium disc was measured using a temperature measurement module and a temperature measurement program. In addition, in order to investigate the sterilizing effect according to the laser power, 808 nm laser was irradiated after application of bacteria to sandblasted large-grit acid-etched (SLA) and resorbable blast media (RBM) coated titanium discs. The irradiated disks were examined with scanning electron microscopy. Results: Both 808 nm and 810 nm lasers increased disk surface temperature as the power increased. When the 810 nm was irradiated under all conditions, the initial temperature rise rate, the descending rate, and the temperature change before and after was higher than that of 808 nm. Disk surface changes were not observed on both lasers at all conditions. Bacteria were irradiated with 808 nm, and the bactericidal effect was increased as the power increased. Conclusion: When applying these diode lasers to the treatment of peri-implantitis, 808 nm which have a bactericidal effect with less temperature fluctuation in the same power conditions would be considered safer. However, in order to apply a laser treatment in the dental clinical field, various safety and reliability should be secured.

• Journal of Oral Medicine and Pain
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• v.24 no.1
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• pp.9-24
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• 1999

Pumping into the upper joint cavity of the TMJ was done on patients who had reducible disc displacement with pain. This article discusses the change in TMJ sounds before and after the Pumping treatment. 20subjects(mean age of $32.1{\pm}10.2yr$)were selected among those who visited the department of Oral Medicine of Yonsei University for the treatment of craniomandibular dysfunctions. Through a thorough history taking, clinical exam and X-ray taking these subjects were diagnosed as reducible disc displacement patients, and they were subdivided into two groups as acute and chronic according to the time the TMJ sound was made. Sonopak was used to measure the TMJ sound before, right after and one-week after the Pumping treatment. VAS was used to measure the degree of subjective TMJ complaints(sounds and pain) before and one-week after the Pumping treatment. Vibration related items included total integral, high integral, low integral, ratio of high integral to low integral, peak amplitude, peak frequency and median frquency. 1. It was not statistically significant between the acute and chronic groups before the treatment. However, total integral, high integral, low integral, peak amplitude, peak frequency, median frequency showed to be greater in the chronic group. 2. In all the subjects, just after the Pumping treatment was done, total integral, high and low integral, peak amplitude and peak frequency significantly decreased (p<0.05). Even after one week, low integral, peak frequency and median frequency significantly decreased (p<0,05), and the TMJ sound diminished accordingly. 3. Comparing the two groups(before and right after the Pumping treatment), there was the following difference ; in the acute group, high integral, high amplitude, high frequency and median frequency significantly decreased(p<0.05). In the chronic group, total integral, high integral, low integral, ratio, peak amplitude and peak frequency significantly decreased(p<0,05). It was not statistically significant between the acute and chronic group. 4. Comparing the two groups(right after and one week after the Pumping treatment), there was the following difference : in the acute group, high integral, high amplitude, high frequency and median frequency significantly decreased(p<0.05), In the chronic group, low integral significantly decreased(p<0.05). However, although it was not statistically significant, after one week, there was an increase in total integral, ratio, peak amplitude and peak frequency compared to right after the treatment group. 5. In the VAS of before and one week after the Pumping treatment of the TMJ pain and sound, the TMJ pain significantly decreased(p<0.05) in both the acute and chronic group. However, it was not statistically significant between the two groups. There was a statistically significant decrease(p<0.05) in the TMJ sound in the acute group after one week of Pumping treatment, but no change was notable in the chronic group and it was not statistically significant between the two groups. From the above results, we can conclude that Pumping into the upper joint cavity of patients having reducible disc displacement is effective in reducing clicking and pain. Therefore, it can be applied in diverse clinical fields.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.19 no.1
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• pp.7-18
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• 1989

The authors analyzed the clinical findings, radiological findings and their correlations in the temporomandibular joint disorders. The results were as follows: 1. The most prevalent age group was in the first decade, then the second decade and the third decade. Female were more common with a ratio of 3.4:1. 2. The most common clinical findings was the pain on open mouth position (42.3%), then came the clicking and limitation of mouth opening. 3. The most common bone change on the condyle side was the erosion, then came the flattening, the osteopyte and the sclerosis in that orders. 4. In the case of the crepitus, the coarse crepitus showed more radiological change than the fine crepitus. The 27% of the patients with crepitus showed the bone change and the patients with crepitus showed more bone change than any other clinical symptoms. 5. In the case of the mouth opening limitation, the evaluation of the translatory movement by transcranial projection was in accordance with the clinical evaluation. 6. The correlation between the clinical symptom and the condylar position within the mandibular fossa was not present and in the case of diagnosis of disc displacement, the transcranial projection seemed not to be able to substitute for the arthrography. Radiographically, the most prevalent age group which showed the bone change was in the first, the second and the third decade. And the bone change seemed to have no relationship with aging.