• 대한치과교정학회지
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• 제36권2호
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• pp.136-144
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• 2006

본 연구는 표준 경두개 방사선사진에서 나타나는 하악두/관절와의 위치 관계 및 형태 특징과 MRI에서 관찰되는 관절원판의 변위 여부를 비교함으로써 측두하악관절 내장증 평가 시 경두개 방사선사진의 임상적 이용 가능성을 알아보고자 하였다. 연구는 성인 환자 76명(남자 26명, 여자 50명)의 113개 악관절을 대상으로 하였다 MRI 자료를 기초로 하여 각 악관절을 정상군, 정복성 관절원판 변위군, 비정복성 관절원판 변위군으로 분류하였으며 최대 감합시의 경두개 방사선사진에서 관절와와 하악두 간의 전방, 후방 및 상방 직선 거리를 계측하여 상대적 위치 평가를 하고 형태적 특징을 판별하기 위해 악관절 경부와 두부간의 각도를 계측하였다. 또한 각 군에 따라 경두개 방사선 계측항목 간에 유의성 있는 차이가 있는지 알아보기 위해 일원분산분석과 다중비교분석을 시행하였다. 표준 경두개 방사선사진에서 나타나는 관절와와 하악두의 위치 관계는 관절원판 변위 여부 및 진행 정도와 상관성을 보이지 않았다. 또한 하악측두관절 경부와 하악두가 이루는 각도는 비정복성 관절원판 변위군에서 유의성 있게 증가하였다. 이는 하악두각이 악관절 내장증의 진행에 따른 악관절의 구조적인 경조직 변화를 반영한다고 볼 수 있으나 이것에만 근거하여 관절원판 변위 여부를 판단하기에는 근거가 미약하다.

• 대한기계학회논문집A
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• 제29권12권
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• pp.1574-1585
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• 2005

In this paper, a spectral element model is developed for the uniform straight pipelines conveying internal unsteady fluid. Four coupled pipe-dynamics equations are derived first by using the Hamilton's principle and the principles of fluid mechanics. The transverse displacement, the axial displacement, the fluid pressure and the fluid velocity are all considered as the dependent variables. The coupled pipe-dynamics equations are then linearized about the steady state values of the fluid pressure and velocity. As the final step, the spectral element model represented by the exact dynamic stiffness matrix, which is often called spectral element matrix, is formulated by using the frequency-domain solutions of the linearized pipe-dynamics equations. The FFT-based spectral dynamic analyses are conducted to evaluate the accuracy of the present spectral element model and also to investigate the structural dynamic characteristics and the internal fluid transients of an example pipeline system.

• Advances in nano research
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• 제12권3호
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• pp.337-344
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• 2022

In this work, the vibrational frequency of two layered FGM cylindrical shell with and without the effects of internal pressure under ring support are discussed in detailed. The functionally graded materials of a cylindrical shell are designed for specific purpose and studied under various boundary conditions. The Love shell dynamical equations theory is utilized to find the relationship between the curvature displacement and strain displacement. Natural frequency vibrations are analyzed by using volume polynomial for bi-layered FGM shell under ring support both for with and without internal pressures.

• 한국전기전자재료학회논문지
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• 제13권1호
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• pp.33-38
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• 2000

In this study, multilayer piezoelectric actuators were fabricated with 75 layers by a conventional multi-layer capacitor (MLC) techniques, using 70Ag/30Pd paste as an internal electrode which can be sintered at low temperature and have cost down effect in mass productions. The multilayer piezoelectric actua-tors had no defects such as diffusions of internal electrode to ceramic bodies and shortages of internal electrodes. The multilayer piezoelectric actuators did not show the crack in the ceramics parts and the gapping phenomena in the external eletrodes when Ag paste was used as external electrodes. The multilayer piezoelectric actuators showed a maximum displacement of 4${\mu}{\textrm}{m}$ at 100V dc voltage and kept the maximum displacement constant for 300 seconds. The multilayer piezoelectric actuators showed good matching properties between ceramic bodies and AgPd internal electrodes. We confirmed the possibility of large-scaled production of the multilayer piezoelectric actuators with superior electrical properties and cost down effect using 70Ag/30Pd paste as an internal electrodes.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제18권1호
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• pp.78-86
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• 1996

This is a retrospective study of 31 patients, who were diagnosed as bilateral TMJ internal derangement in consequence of magnetic resonance imaging (MRI) of the temporomandibular joint (TMJ) at Department of Dentistry, Ajou University Hospital, and who were compared clinical findings with radiological findings. The results obtained were as follows. 1. The average of the patients of bilateral TMJ internal derangement was 27.3 years with a range from 12 to 74 years, and 93.6% of the patients were yonger than 40 years of age. The male-female ratio was 1 : 6.8, and the females of $20{\sim}29$ years were most common in 35.5%. 2. In the patients of bilateral TMJ internal derangement, the patients who complained clinical symptoms bilaterally were 38.7% and the patients who complained clinical symptoms untilaterally were 61.3%. 3. The most common disc position of bilateral TMJ internal derangement was anterior disc displacement without reduction on both sides in 38.7%. The most common disc configuration of bilateral TMJ internal derangement was biconcave on both sides and amorphous on both sides in closed mouth, and was amorphous on both sides in open mouth. 4. In the patients of bilateral TMJ internal derangement, the joints which really showed clinical symptoms were most common in anterior displacement without reduction of 48.9%.

• Advances in nano research
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• 제16권3호
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• pp.273-288
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• 2024

The geometrical nonlinear vibrations of the gold nanoscale rod are investigated for the first time by considering the internal modals interactions using different nonlinear beam theories. This phenomenon is usually one of the important features of nonlinear vibration systems. For a more detailed analysis, the von-Karman effects, preserving all the nonlinear terms in the strain-displacement relationships of gold nanoscale rods in three displacement directions, are considered to analyze the nonlinear axial vibrations of gold nanoscale rods. It uses highly accurate analytical-numerical solutions for the clamped-clamped and clamped-free boundary conditions of nanoscale gold rods. Also, with the help of Hamilton's principle, the governing equation and boundary conditions are derived based on Eringen's theory. The influence of nonlinear and nonlocal factors on axial vibrations was investigated separately for all three theories: Simple (ST), Rayleigh (RT) and Bishop (BT). Using different theories, the effects of inertia and shear on the internal resonances of gold nanorods were studied and compared in terms of twoto-one and three-to-one internal resonances. As the nonlocal parameter of the gold nanorod increases, the maximum nonlinear amplitude occurs. So, by adding nonlocal effects in a gold nanorod, the internal modal interactions resulting from the unique structure can be enhanced. It is worth noting that shear and inertial analysis have a significant effect on internal modal interactions in gold nanorods.

• 한국운동역학회지
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• 제21권4호
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• pp.467-477
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• 2011

This study was performed to investigate the effects of tibial rotation while going up stair on muscle activity of vastus medialis oblique and vastus lateralis, and on patellar displacement. The subjects included 30 people (male: 15; female: 15) who were randomly assigned to the tibial internal-rotation, neutral-rotation, and external-rotation groups. The subjects went up the stair while performing the assigned rotations, and the rotation of the hip and the displacement of the patella were measured using a 3D motion analyzer. In addition, the maximum voluntary isometric contraction (MVIC) of the vastus medialis oblique and vastus lateralis were measured using surface electromyogram. On the tibial internal rotation, the hip rotation significantly appeared in the same direction and so did on the tibial neutral and external rotations(p<.001). Although the MVIC of the vastus medialis oblique and vastus lateralis did not significantly differ by tibial rotation during the stair ascent, the MVIC of the vastus medialis oblique was higher than that of the vastus lateralis during the internal and neutral rotations (p<.05). In addition, during the stair ascent, the displacement of the patella was more significant during the tibial external rotation than during the tibial internal and neutral rotations(p<.001). Thus, patients with patellofemoral pain are required to be considered the effects of tibial rotation for their rehabilitation.

• The Journal of Advanced Prosthodontics
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• 제10권5호
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• pp.388-394
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• 2018

PURPOSE. To measure axial displacement of different implant-abutment connection types and materials during screw tightening at the recommended torque by using a contact scanner for two-dimensional (2D) and three-dimensional (3D) analyses. MATERIALS AND METHODS. Twenty models of missing mandibular left second premolars were 3D-printed and implant fixtures were placed at the same position by using a surgical guide. External and internal fixtures were used. Three implant-abutment internal connection (INT) types and one implant-abutment external connection (EXT) type were prepared. Two of the INT types used titanium abutment and zirconia abutment; the other INT type was a customized abutment, fabricated by using a computer-controlled milling machine. The EXT type used titanium abutment. Screws were tightened at $10N{\cdot}cm$, simulating hand tightening, and then at the manufacturers' recommended torque ($30N{\cdot}cm$) 10 min later. Abutments and adjacent teeth were subsequently scanned with a contact scanner for 2D and 3D analyses using a 3D inspection software. RESULTS. Significant differences were observed in axial displacement according to the type of implant-abutment connection (P<.001). Vertical displacement of abutments was greater than overall displacement, and significant differences in vertical and overall displacement were observed among the four connection types (P<.05). CONCLUSION. Displacement according to connection type and material should be considered in choosing an implant abutment. When adjusting a prosthesis, tightening the screw at the manufacturers' recommended torque is advisable, rather than the level of hand tightening.

• Imaging Science in Dentistry
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• 제31권2호
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• pp.93-99
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• 2001

Purpose: To analyze the possible association between magnetic resonance imaging signal intensity of temporomandibular joint disk and posterior attachment, and the type and extent of disk displacement, disk configuration, effusion and clinical signs in patients with internal derangement. Materials and Methods: Magnetic resonance images of the 132 temporomandibular joints of 66 patients with temporomandibular joint displacement were analyzed. The clinical findings were obtained by retrospective review of the patients' records. The type and extent of disk displacement, disk configuration and effusion were evaluated on the proton density MR images. The signal intensity from the anterior band, posterior band and posterior attachment were measured on MR images. The associations between the type and extent of disk displacement, disk configuration, effusion and clinical signs and the MR signal intensity of disk and posterior attachment were statistically analyzed by student's t-test. Results: Of 132 joints, 87 (65.9%) showed anterior disk displacement with reduction (ADR) and 45 (34.1%) showed anterior disk displacement without reduction (ADnR). The signals from posterior attachments were lower in joints with ADnR than those of ADR (p<0.05). The results showed statistically significant (p<0.05) association between the type and extent of disk displacement and disk configuration, and decreased signal intensity of posterior attachment. There were no statistical associations between pain, noise and limited mouth opening, and signal intensity of disk and posterior attachment. Conclusions: The average signal from posterior attachment was lower in joints with ADnR than that of ADR. The type and extent of disk displacement and disk configuration appeared to be correlated with the signal intensity from posterior attachment.

• 대한치과보철학회지
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• 제59권1호
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• pp.126-133
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• 2021

여러 연구에서 임플란트 지지 보철물의 수직 침하에 대해 보고되고 있지만, 구강내 임플란트 지지보철물의 기능 시 수직침하 양상에 대해서는 알려진 바 없다. 본 증례에서는 2명의 환자에서 구치부 단일 치아 임플란트 지지 보철물의 3차원적인 변화를 평가하였다. 내부연결형 임플란트를 식립하였으며 통상적인 방법으로 Screw-Cement Retained Prosthesis(SCRP) 형태의 보철물을 제작해 장착하였다. 구강스캐너(Cerec Omnicam, Dentsply Sirona, USA)를 이용해 보철물 장착 시, 장착 1주, 1개월, 1년 후 구강 스캔을 시행하였으며 디지털 분석 프로그램(Geomagic Control X, 3D systems, USA)을 이용해 기간에 따른 위치 변화를 3차원적으로 평가하였다. 인접 치아를 기준으로 보철물 장착 후 임상적인 위치 변화가 나타났으며 변화량은 시간이 지남에 따라 증가하였다.