• Maxillofacial Plastic and Reconstructive Surgery
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• v.22 no.3
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• pp.294-300
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• 2000

Purpose: The aim of this study was to find the clinical characteristics of the patients who had temporomandibular joint internal derangement(ID) with disc adhesion(adhesion group) compared to only disc displacement without disc adhesion, perforation, hyperemia, and so on(ID group). Materials and methods: Thirty seven joints were included in adhesion group and 54 joints in ID group of all 174 patients(174 joints) treated surgically and had been checked periodically over 12 months at TMJ clinic of Yongdong Severance Hospital, Yonsei University, between 1992 and 1997. Mouth opening range, pain during mouth opening and biting, headache, neck/shoulder pain and TMJ sound were checked his/her every visit before and after surgery. Results: The maximum mouth opening was improved significantly after postoperative 3 months in two groups(p<0.01), but adhesion group was less improved. Pain during mouth opening was improved significantly over 3 months after surgery in adhesion group(p<0.01), but in ID group 1 month after surgery. Biting pain was improved and maintained it after surgery and not significant difference between two groups. Headache and neck/shoulder pain were much improved after surgery(p<0.01), but slight relapse was found in adhesion group after 12 months. TMJ sound was more found in adhesion group after 1 month(p<0.05), but after 3 months, no significant difference was found between two groups. Conclusions: The postoperative results of adhesion group were worse than ID group. Therefore, it is considered more carefully to diagnose and treat in cases of internal derangement with adhesion.

• Journal of Korean Society of Steel Construction
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• v.17 no.4 s.77
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• pp.499-509
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• 2005

The excessive wind-induced motion of tall buildings most frequently result from vortex-shedding-induced across-wind oscillations. This form of excitation is most pronounced for relatively flexible, lightweight, and lightly damped high-rise buildings with constant cross-sections. This paper discusses the aerodynamic means ofmitigating the across-wind vortex shedding induced in such situations. Openings are added in both the drag and lift directions in the buildings to provide pressure equalization. Theytend to reduce the effectiveness of across-wind forces by reducing their magnitudes and disrupting their spatial correlation. The effects of buildings with several geometries of openings on aerodynamic excitations and displacement responses have been studied for high-rise buildings with square cross-sections and an aspect ratio of 8:1 in a wind tunnel. High-frequency force balance testshave been carried out at the Kumoh National University of Technology using rigid models with 24 kinds of opening shapes. The measured model's aerodynamic excitations and displacement were compared withthose of a square cylinder with no openings to estimate the effectiveness of openings for wind-induced oscillations. From these results, theopening shape, size, and location of buildings to reduce wind-induced vortex shedding and responses were pointed out.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.4
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• pp.354-361
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• 2004

This Paper describes a crack scattering model for SH wave based on the boundary integral equation(BIE) method, where the fundamental unknown is crack opening displacement(COD). When a time harmonic plane wave was incident on a 2-D isolated crack (slit) of width 2a, the COD distributions were numerically calculated as a function of ka. The calculated COD agreed well with results obtained with other methods. The far-field scattering amplitude, which completely characterizes the flaw response, was calculated in two ways. The Kirchhoff approximation and the BIE-COD exact formulation were compared in terms of incidence angle and frequency ka in a pulse-echo mode. Maximum response was obtained for both methods at the specular reflection direction. Away from the specular direction, the Kirchhoff approximation becomes less accurate. The time domain crack response was also calculated using a band-limited spectrum of center frequency 10 MHz. At oblique incidence to the crack both methods show the existence of an antisymmetric flash points occurring from the crack edge. The Kirchhoff approximation provides an exact time interval between flash points, although it unrealistically gives the same amplitude.

• Journal of the Korean Institute of Gas
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• v.2 no.1
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• pp.7-13
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• 1998

In this study, for the safety performance of LNG storage tank, the fracture toughness in X-grooved weld HAZ(heat-affected zone) of $9\%$ Ni steel was evaluated qualitatively and quantitatively, and the relation with the change in microstructure was analyzed. The toughness assessment was peformed through the modified CTOD test proposed for thick weldment with X-groove. Additionally, microstructures of HAZ were evaluated by OM, SEM and XRD. From the results, HAZ toughness of SMA(shielded metal arc)-welded $9\%$ Ni steel decreased as the evaluated region approached the fusion line. The decrease in toughness was apparently caused by the increase in the fraction of coarse-grained zone within HAZ. On the other hand, toughness drop with decreasing test temperature in F.L.(fusion line) ${\~}$F.L.+3mm was larger than that in F.L.+5mm${\~}$F.L.+7mm region due to the fact that in the former regions, retained austenite had poor stability.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.349-356
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• 2018

In this study, material properties of steel fiber reinforced high strength concrete (FRHSC) with the compressive strength of about 120MPa were modeled. Steel fiber content of 1.0%, 1.5%, and 2.0% was considered as experimental variable. First of all, compressive strength tests were carried out to determine compressive characteristics of concrete, and compressive stress-strain curves were modeled. For conventional concrete with moderate compressive strength, the stress-strain curves are in the form of parabolic curves, but in the case of high strength concrete reinforced with steel fiber, the curves increase linearly in the form of the straight line. In addition, to understand the tensile properties of FRHSC, the crack mouth opening displacement (CMOD) test was performed, and the tensile stress-CMOD curve was calculated through inverse analysis. When the steel fiber content increased from 1.0% to 1.5%, there was a significant difference of tensile strength. However, when the amount of steel fiber was increased from 1.5% to 2.0%, there was no significant difference of tensile strength, which might result from the poor dispersion and arrangement of steel fiber in concrete.

• Journal of the Korea Concrete Institute
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• v.22 no.4
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• pp.461-472
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• 2010

This paper investigates the behavior of precast concrete (PC) shear walls with a new vertical connections for a fast remodeling construction. The C-type vertical connections for the PC wall systems are proposed for transfer of bending moment between top and bottom walls in the vertical direction while a shear key in the center of wall is prepared to transfer shear forces by bearing action. The proposed vertical connections allows easy fabrication thanks to slots at the edges of wall in opposite directions. The plane PC wall systems subject to lateral load are compared with ordinary wall systems by investigating the effects of connection on the stiffness, strength, ductility, and failure modes of whole systems. The load-displacement relationship and influence of premature failure of connections are examined. The experimental test showed that the longitudinal reinforcing steel bars placed at the edges of walls yielded first and the ultimate deformation were terminated due to premature failure of connections. The diagonal reinforcements for efficient shear transfer in the walls were not effective. The strength and deformation obtained through the section analysis were generally in agreement with the experimental data, and indicated that. Gap opening contributed to the deformation behavior more than any other factors.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.7
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• pp.535-541
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• 2018

In this study, wedge splitting tests were performed to evaluate fracture behavior of particle reinforced composite materials. Crack resistance was evaluated by using CTOD (crack tip opening displacement) and crack tip opening angle (CTOA). The particle reinforced composites were tested under various temperature ($-60^{\circ}C{\sim}50^{\circ}C$) and load speed (5~500mm/min). Also, digital image correlation method (DIC) was used to analyze the strain field at crack tip. Test results showed that the fracture energy increased with decreasing temperature and crack resistance increased with increasing load velocity.

• Journal of Oral Medicine and Pain
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• v.20 no.2
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• pp.407-420
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• 1995

This study was performed to evaluate and compare conservative treatment results by several parameters such as age, sex, symptom duration, type and timing of joint sound, parafunctional habits, splint type, and diagnostic classification. There have been too many articles reporting long term results of conservative treatment but articles related to comparison of treatment results by patients' self-evaluation have been rarely reported. For this study 258 patients with temporomandibular disorders(TMDs) were selected and examined by routine diagnostic procedure for TMDs. The subjects were classified into 5 TMDs subgroups ad treated with conservative treatments involving splints, physical modalities, jaw exercises, and counseling. Visual analogue scale(VAS) about pain, joint sound, and mouth opening limitation was recorded respectively during treatment period. From the VAS data and treatment duration, VAS treatment index(VAS Ti) was calculated. The obtained results were as follows : 1. Pain was the most frequent main symptom in subjects with temporomandibular disorders, and main symptom for mouth opening limitation was comparatively less than for pain or sound in disk displacement with reduction group or in degenerative joint disease group. 2. Degenerative joint disease group had the most poor treatment results and highest occlusal index of Helkim's index. 3. Good prognosis for conservative treatment was observed in acute group, under 6 months than chronic group, 6months over in symptom duration, and subjects with 40 years over in age showed the most poor prognosis. 4. Subjects treated with anterior repositioning splint had better treatment results than subjects treated with centric relation splint, but statistical significance in VAS Ti and treatment duration was not observed. 5. Treatment results according to affected side, types and point of joint sound did not show consistent statistical results. 6. The result for conservative treatment was observed poor in subjects with bruxism and clenching. 7. In studying coincidence between preferred chewing and affected side, frequency of preferred chewing side, in unilateral affection, was higher in ipsilateral than in contralateral side.

• 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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.12
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• pp.1521-1528
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• 2012

The present paper provides the elastic stress intensity factors (SIFs) and the crack opening displacements (CODs) of a thick-walled pipe with a slanted axial through-wall crack. For estimating these elastic fracture mechanics parameters, systematic three-dimensional elastic finite element (FE) analyses were performed by considering geometric variables, i.e., thickness of pipe, reference crack length, and crack length ratio, affecting the SIFs and CODs. As for loading condition, the internal pressure was considered. Based on the FE results, the SIFs and CODs of slanted axial through-wall cracks in a thickwalled pipe along the crack front and the wall thickness were calculated. In particular, to calculate the SIFs of a thick-walled pipe with a slanted axial through-wall crack from those of a thick-walled pipe with an idealized axial through-wall crack, a slant correction factor representing the effect of the slant crack on the SIFs was proposed.