• The korean journal of orthodontics
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• v.22 no.1
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• pp.109-121
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• 1992

Temporomandibular joint is a major structure to play an important role in the function & stability of the occlusion as well as the stomatognathic system. Therefore, the TMJ is the structure that requires the complete analysis for diagnosing and planning treatment of pathologic changes by TMJ dysfunction and malocclusion. So, in this study, to evaluate TMJ situation in Korean malocclusion, based on the previous accomplishments, students of the dental college of Won-Kwang Univ. are surveyed and selected in terms of Angle's classification of malocclusion, whose TMJ radiographs were taken in the centric occlusion and centric relation. In each maiocclusion groups, the mean and standard deviation of anterior, posterior and superior joint space of the right, left and both side in CO & CR are evaluated and also those of the fossa height and the articular eminence angle of the right, left and both sides are evaluated. The obtained results were as follows: 1. In the correlation coefficient between the malocclusion groups, no other items except the posterior joint space of the right side in CR between in class I and class III are significant. 2. In the correlation coefficient between the right and left side, the each joint space in class I malocclusion group and class II malocclusion group are significant. 3. In the change of each joint space during the transmit from CO to CR, there is a tendency of increasing anterior joint space and decreasing posterior, superior joint spaces in class I, II malocclusion and increasing superior joint space and decreasing anterior, posterior joint space in class III malocclusion, which is significant in the correlation coefficient, but not significant in the T-test. 4. In each malocclusion group, the correlation coefficient between the posterior joint space and the superior joint space in C.R is highly significant. 5. The fossa height of class II malocclusion group is lesser than that of class I or class III, which is not significant in T-test. 6. In the correlation coefficient between Rt. and Lt. side in the fossa height, it is not significant in class I and class III group, but significant in class II malocclusion group. 7. The articular eminence angle of class II malocclusion group is larger then that of class I or class III groups, which is fairly significant. 8. In the correlation coefficient between Rt. and Lt. side in the articular eminence angle, it is significant in each malocclusion group.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.1
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• pp.77-89
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• 2020

Submerged floating tunnel (SFT) is a type of tunnel that allows tunnel segments to float underwater by buoyancy, and is being actively studied in recent years. When the submerged floating tunnel is connected to the ground, the tunnel and the bored tunnel inside the ground must be connected. There is risk that the stress will be concentrated at the connection between the two tunnels due to the different constraints and behavior of the two tunnels. Therefore, special design and construction methods should be applied to ensure the stability around the connection. However, previous studies on the stability at the connection site have not been sufficiently carried out, so study on the basic stage of the stability at connection site are necessary. In this study, numerical analysis simulating the connection between submerged floating tunnel and the bored tunnel confirmed that the shear strain concentration occurred in the ground around the connection, and it was analyzed that the structural factors can be handled during construction to have effects on the stability of the ground around the connection. Numerical results show that the risks from disproportionate displacements in the two tunnels can be mitigated through the construction of grouting material and joint design. Although the results from this study are qualitative results, it is expected that it will contribute to the determination of structural factors and risk areas that should be considered in the design of connections between the submerged floating tunnel and bored tunnel in the future studies.

• Korean Journal of Applied Biomechanics
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• v.19 no.1
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• pp.77-85
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• 2009

This study is aimed at providing information on injury prevention and skill improvement by inducing the accurate movements in exercise as well as understanding the principles of badminton drive movements. Movement displacement of racket head showed the similar patterns among those surveyed but, it seemed that slight differences resulted from external factors such as height, length of brachial and forearm and individual trend of swing locus. Regarding upper joint angle per phase, the angles of shoulder joint, elbow joint and wrist joint were closely associated in taking drive movements and they supported the segment order theory that power was conveyed from proximal into distal. It was shown that angular velocity of upper joint became larger in follow through movement after impact among all those surveyed, which meant the importance of follow through in racket sports such as badminton. In conclusion, this follow through movement acts as an important factor in racket sports in terms of pose stability maintenance, pose correction of movements and injury prevention of joints. In summary, when swings are made according to segment order theory, efficient movements can be taken.

• Journal of the Korean Geotechnical Society
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• v.24 no.5
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• pp.65-78
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• 2008

In case of cut-slopes or shallow-depth tunnels, sliding along with discontinuities or rotation could play a critical role in judging stability. Although numerical analysis is widely used to check the stability of these cut-slopes and shallow-depth tunnels in early design process, common analysis programs are based on continuum model. Performing continuum model analysis regarding discontinuities is possible by reducing overall strength of jointed rock mass. It is also possible by applying ubiquitous joint model to Mohr-Coulomb failure criteria. In numerical analysis of cut-slope, main geotechnical properties such as cohesion, friction angle and elastic modulus can be evaluated by empirical equations. This study tried to compare two main systems, RMR and GSI system by applying them to in-situ hazardous cut-slopes. In addition, this study applied ubiquitous joint model to simulation model with inputs derived by RMR and GSI system to compare with displacements obtained by in-situ monitoring. To sum up, numerical analysis mixed with GSI inputs and ubiquitous joint model proved to provide most reliable results which were similar to actual displacements and their patterns.

• Physical Therapy Korea
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• v.29 no.1
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• pp.64-69
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• 2022

Background: Gluteus medius muscle is important for the stability of hip joint. The sufficient core stability can be contributed to the performance of gluteus medius muscle in standing position. In addition, the external support may affect core stability in standing position. Objects: The purpose of this study was to investigated the effectiveness of the external support on the strength and muscle activity of hip abductor muscle during hip abduction in standing position in subjects without core stability. Methods: Fifteen subjects participated in this study. The subjects were evaluated by using the double-leg lowering with bent knees to measure the core stability. The strength and muscle activity of hip abductors was measured in standing position with the condition with and without external support using the tensiometer sensor and the surface electromyography. The paired t-test was used to investigate the difference between hip abductor strength and activity according to external support. The level of statistical significance was set at α = 0.05. Results: The hip abductor strength and muscle activity of gluteus medius muscle with external support were significantly greater than those without external support during hip abduction in standing position (p < 0.05). Conclusion: During hip abduction in standing position, the external support may be contributed to the improvement of the hip abductor strength and muscle activity of gluteus medius especially in the subjects without core stability.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1780-1783
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• 2005

In this paper ZMP was considered in order to get a walking stability, so the gait in the stable domain was realized through putting the stability margin in the sole domain of a foot. It is assumed that the robot's legs have 12 joints to operate a open-loop drive and there was no external disturbance under walking phases, additionally, the robot is walking on the flat plane. It was observed that the robot's walking trajectory, locus of COM and ZMP after imposing the motion to each joint. For realizing the simulation considering ZMP and movement of mass center, it was checked if it is stable for the constraint robot model to walk in stability and the feasibility was estimated about its dynamic gait. Eventually it was shown that a constraint gait algorithm is able to realize. To verify the proper walking process, ZMP(Zero Moment Point) theory is applied and the simulation has been done by ADAMS.

• The Journal of Korea Robotics Society
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• v.18 no.2
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• pp.172-181
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• 2023

This paper presents research on the stability of control for a quadruped robot with two different leg structure designs. The focus of the research is on the design and analysis of the leg structures in terms of their impact on the stability and robustness of the robot's motion. First, a static analysis was performed in the simulation to compare the structural strength of the legs when the same force was applied. Secondly, two quadruped robots were built, each equipped with differently designed legs, and performed trot gait walking in the real world. And the states of the robots and the torques of each joint were analyzed and compared. In conclusion, based on the results of structural analysis in simulation and the actual walking experiments with the robots, it was demonstrated that the legs designed to be structurally robust improved the control stability of the quadruped robot.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.2
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• pp.164-173
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• 2009

Purpose: The purpose of this study was to evaluate the effect of abutment material on screw-loosening before and after cyclic loading. Among the different materials of abutments, zirconia and metal abutment were used. Material and methods: Two types of implant systems: external butt joint(US II, Osstem Implant, Korea) and internal conical joint(GS II, Osstem Implant, Korea) were used. In each type, specimens were divided into two different kinds of abutments: zirconia and metal(n=5). The implant was rigidly held in a special holding to device ensure fixation. Abutment was connected to 30 Ncm with digital torque gauge, and was retightened in 30 Ncm after 10 minutes. The initial removal torque values were measured. The same specimens were tightened in 30 Ncm again and held in the cycling loading simulator(Instron, USA) according to ISO/FPIS 1480. Cycling loading tests were performed at loads 10 to 250 N, for 1 million cycles, at 14 Hz,(by subjecting sinusoidal wave from 10 to 250 N at a frequency of 14 Hz for 1 million cycles,) and then postload removal torque values were evaluated. Results: 1. In all samples, the removal values of abutment screw were lower than tightening torque values(30 Ncm), but the phenomenon of the screw loosening was not observed. 2. In both of the implant systems, initial and postload removal torque of zirconia abutment were significantly higher than those of metal abutment(P<.05). 3. In both of the implant systems, the difference in removal torque ratio between zirconia abutment and metal abutment was not significant(P>.05). 4. In metal abutments, the removal torque ratio of GS II system(internal conical joint system) was lower than that of US II system(external butt joint system)(P<.05). 5. In zirconia abutments, the difference in removal torque ratio between the two implant systems was not significant(P>.05). Conclusion: Zirconia abutment had a good screw joint stability in the condition of one million cycling loading.

• Journal of the Korean Geotechnical Society
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• v.15 no.4
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• pp.221-234
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• 1999

This paper deals with the application of joint element in the finite element modeling of discontinuities encountered during rock tunneling. A nodal displacement joint element was implemented in a two dimensional finite element program GEOFE2D. The applicability of the joint element for modeling of discontinuities and the numerical stability of the implemented algorithm were examined by comparing the results of reduced small scale model tests as well as commercially available FEM program. The GEOFE2D was then used to analyze a tunnel crossed by a major discontinuity for the purpose of understanding the effect of discontinuity on the tunnel behavior. In addition, a modeling technique for the junction of discontinuity and shotcrete lining was presented. The results of analysis indicated that the stress-strain field around the tunnel is significantly altered by the presence of discontinuity, and that the stresses in the shotcrete lining considerably increase at the junction of the shotcrete lining and the discontinuity. It is therefore concluded that the major discontinuities must be carefully modeled in the finite element analysis of a tunneling problem in order to obtain more reliable results close to actual tunnel behavior.

• Korean Journal of Applied Biomechanics
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• v.26 no.2
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• pp.153-159
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• 2016

Objective: The purpose of this study was to investigate the effects of joint mobilization on foot pressure, ankle moment, and vertical ground reaction force in subjects with ankle instability. Method: Twenty male subjects (age, $25.38{\pm}3.62yr$; height, $170.92{\pm}5.41cm$; weight, $60.74{\pm}9.63kg$; body mass index (BMI), $19.20{\pm}1.67kg/m^2$) participated and underwent ankle joint mobilization. Weight-bearing distribution, ankle dorsi/plantar flexion moment, and vertical ground reaction force were measured using a GPS 400 and a VICON Motion System (Oxford, UK), and subsequently analyzed. SPSS 20.0 for Windows was used for data processing and paired t-tests were used to compare pre- and post-mobilization measurements. The significance level was set at ${\alpha}$ = .05. Results: The results indicated changes in weight-bearing, ankle dorsi/plantar flexion moment, and vertical ground reaction force. The findings showed changes in weight-bearing distribution on the left (pre $29.51{\pm}6.31kg$, post $29.57{\pm}5.02kg$) and right foot (pre $32.40{\pm}6.30kg$, post $31.18{\pm}5.47kg$). There were significant differences in dorsi/plantar flexion moment (p < .01), and there were significant increases in vertical ground reaction forces at initial stance (Fz1) and terminal stance (Fz2, p < .05). Additionally, there was a significant reduction in vertical ground reaction force at midstance (Fz2, p < .001). Conclusion: Joint mobilization appears to alter weight-bearing distribution in subjects with ankle instability, with resultant improvements in stability.