• The Journal of Korean Physical Therapy
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• v.13 no.1
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• pp.1-18
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• 2001

Aging has been recognized as the primary cause of disc degeneration. A biomechanical characteristics of disc degeneration has been demonstrated that intradiscal pressure is reduced. With the increasing population of elderly people, disc degeneration and associated problems of nerve entrapment are becoming more prevalent. Presently, research on reduced intradiscal pressure associated with degeneration is insufficient. In this study. we used the Finite Element Method (FEM) of computerized simulations to investigate the effects of variation in intradiscal pressure on mechanical behaviours of L4-5 intervertebral disc degeneration. Degeneration was classified using four grades based on initial intradiscal pressure; Normal (135 kPa), mild(107 kPa), moderate (47 kPa) and severe (15 kPa). The predicted results f3r bending loads were as follows; 1 . Range of motion increased progressively with severity of degeneration with flexion and lateral bending moments, but decreased with extension moments. 2. Discal bulging of posterolateral aspect was larger in lateral bending and extension moment. But bulging was increased with severity of degeneration in lateral bending and torsion(same side).3. The rate of increasing intradiscal pressure was decreased in all bending motions with severity of degeneration. In conclusion, lateral bending and extension moment yield greatest bulging in severe degeneration. In torsion, although bending load produces disc bulging, disc bulging was associated more strongly with severity of degeneration than increasing torsional moments. Clinical Implications: Discal bulging may produce nerve root impingement and irritation. The effect of loading and posture on the varying degrees of disc degeneration has important implications especially in the elderly. In the presence of disc degeneration, avoidance of end range postures, especially extension and lateral bending may help reduce discal bulging and in turn, nerve entrapment.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.61-61
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• 2010

The purpose of this study is to prevent the unstable fracture at the FCA butt weldment of hatch coaming deck in the ultra large containership during service life. In order to do it, the behavior of the embedded crack at the weldment under design loading conditions was evaluated in accordance with BS7910. Here, the level of primary stress induced by ship motion was evaluated by the design code of classification society and FEA. The level of residual stress as secondary stress was calculated in consideration of the restraint degree of weldment and welding heat input by using the predictive equation proposed by authors in the previous study. The fatigue crack growth rate at the weldment was evaluated using CT specimen in accordance with ASTM E647. According to the results, although the allowable defect for embedded crack specified in the classification society exists at the weldment, the occurrence possibility of unstable fracture at the weldment could not be negligible, regardless of CTOD value given in this study. So, in this study, the effect of initial defect size, welding heat input, restraint degree and CTOD on the fracture mechanical characteristics of embedded crack at the weldment was evaluated by the comprehensive fracture assessment. Based on the results, the design criteria including allowable defect, residual stress level and CTOD value was established to prevent the unstable fracture at the FCA butt weldment of hatch coaming deck in an ultra large containership during service life of 20years.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4_1
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• pp.137-150
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• 1992

A complete solution, exact to second-order, for wave motion forced by a hinged-wavemaker of variable-draft is presented. A solution for a piston type wavemaker is also obtained as a special case of a hinged-wavemaker. The laboratory waves generated by a plane wave board are shown to be composed of two components; viz., a Stokes second-order wave and a second-harnomic free wave which travels at a different speed. The amplitude of the second-harmonic free wave is relatively large in shallow water and decreases to less than 10% of the amplitude of the primary wave in deep water. Wavemakers with relatively deeper draft (i.e., hinged near the bottom) generate the free waves of smaller amplitude in shallow and intermediate water depths than the wavemakers with shallow draft. However, the opposite is predicted by theory in deep water.

• Proceedings of the KSMRM Conference
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• 2003.10a
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• pp.97-97
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• 2003

Contrast-enhanced MR angiography (CE-MRA) gradually occupies its position as a primary evaluation tool forsteno-occlusive disease of supra-aortic cervical arteries. It has several advantages over time-of-flight (TOF) technique such as shorter imaging time, less saturation effect, and less flow- and motion-related artifacts. Diverse methods of k-space sampling, imaging sequences, and strategies for image acquisitiontiming have been introduced since its early clinical application. Especially, methods of k-space sampling and image acquisition timing are very important to achieve maximal arterial enhancement and suppress venous signal while maintaining large scan coverage and high spatial resolution. In addition, regardless of several advantages over TOF technique, it still has a tendency to overestimate the degree of stenosis in patients with carotid or vertebralartery disease. In this exhibit, we will overview the current techniques of CE-MRA with special attention to methods of k-space sampling and image acquisition timing. We will also discuss diagnostic accuracy of CE-MRA in patients with supra-aortic cervical artery stenosis and artifacts frequently misinterpreted as steno-occlusive lesion on CE-MRA.

• Smart Structures and Systems
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• v.19 no.5
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• pp.487-497
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• 2017

Semi-active devices use the building's own motion to produce resistive forces and are thus strictly dissipative and require little power. Devices that independently control the binary open/closed valve state can enable novel device hysteresis loops that were not previously possible. However, some device hysteresis loops cannot be obtained without active analog valve control allowing slower, controlled release of stored energy, and is presents an ongoing limitation in obtaining the full range of possibilities offered by these devices. This in silico study develops a proportional-derivative feedback control law using a validated nonlinear device model to track an ideal diamond-shaped force-displacement response profile using active analog valve control. It is validated by comparison to the ideal shape for both sinusoidal and random seismic input motions. Structural application specific spectral analysis compares the performance for the non-linear, actively controlled case to those obtained with an ideal, linear model to validate that the potential performance will be retained when considering realistic nonlinear behaviour and the designed valve control approach. Results show tracking of the device force-displacement loop to within 3-5% of the desired ideal curve. Valve delay, rather than control law design, is the primary limiting factor, and analysis indicates a ratio of valve delay to structural period must be 1/10 or smaller to ensure adequate tracking, relating valve performance to structural period and overall device performance under control. Overall, the results show that active analog feedback control of energy release in these devices can significantly increase the range of resetable, valve-controlled semi-active device performance and hysteresis loops, in turn increasing their performance envelop and application space.

• Clinics in Shoulder and Elbow
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• v.18 no.1
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• pp.28-35
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• 2015

Background: We assessed the effectiveness of arthroscopic capsular release for the treatment of adhesive capsulitis. Further, we tried to ascertain the clinical benefits, if any, of pancapsular release over selective capsular release, where the two differ by performing or not performing a posterior capsular release, respectively. Methods: Thirty-five consecutive patients with either primary or secondary adhesive capsulitis who failed conservative treatment for more than 6 months were enrolled in the study. A total of 16 patients allocated in group 1 received a pancapsular release that comprises the release of the rotator interval, anteroinferior capsular, and the posterior capsular release, whereas 19 patients in group 2 received a selective capsular release that comprises only the release of the rotator interval release and anteroinferior capsular release. The clinical outcomes, visual analogue scale (VAS) score, Constant score, and range of motion, were assessed preoperative and postoperatively. Results: In both groups, the preoperative VAS score, Constant score, and ROM showed a significant improvement by the 6-month follow-up. We found that the immediate postoperative internal rotation was significantly higher in group 1 than group 2. Despite significant differences seen between the two groups at the initial postoperative period, there were no significant differences in Constant score, VAS score, and the ROM at all the subsequent follow-ups between the two groups. Conclusions: Arthroscopic capsular release for the treatment of adhesive capsulitis is very effective. However, pancapsular release did not show any advantage over selective capsular release in terms of overall clinical outcome.

• Applied Microscopy
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• v.42 no.2
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• pp.95-103
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• 2012

The cell surface sculpture of the plant epidermis has received great interest recently. It has also been an active area of research, as the biological microstructures of the surface, such as papillae and waxes, exhibit several unique properties, including self-cleaning character; namely the "Lotus effect" first described in the leaves of the lotus, Nelumbo nucifera. The Lotus effect is the phenomenon in which the super-hydrophobic and water-repellent nature of lotus leaves allow water drops to run off easily on the surface in a rolling and sliding motion thereby facilitating the removal of dirt particles. It is well-known that surface roughness on the micro- and nanoscale is a primary characteristic allowing for the Lotus effect. This effect is common among plants and is of great technological importance, since it can be applied industrially in numerous fields. In the present study, Nelumbo nucifera leaf and stem epidermal surfaces have been examined with a focus on the features of papillae and wax crystalloids. Both young and mature Nelumbo nucifera leaf epidermis demonstrated the Lotus effect on their entire epidermal surface. The central area of the upper epidermis, in particular, formed extremely papillose surfaces, with an additional wax layer, enabling greater water repellency. Despite the presence of wax crystalloids, epidermal surfaces of the lower leaf and stem lacking papillae, were much more easily wetted.

• Journal of Korean Association for Spatial Structures
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• v.10 no.1
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• pp.103-110
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• 2010

In this study, the possibility of seismic response control of semi-active tuned mass damper (TMD) for spatial structures has been investigated. To this end, an arch structure was used as an example structure because it has primary characteristics of spatial structures and it is a comparatively simple structure. A TMD and semi-active TMD were applied to the example arch structure and the seismic control performance of them were evaluated based on the numerical simulation. In order to regulate the damping force of the semi-active TMD, groundhook control algorithm, which is widely used for semi-active control, was used. El Centro (1940) and Northridge (1994) earthquakes and harmonic ground motion were used for performance evaluation of passive TMD and semi-active TMD. Based on the analytical results, the passive TMD could effectively reduce the seismic responses of the arch structure and it has been shown that the semi-active TMD more effectively decreased the dynamic responses of the arch structure compared to the passive TMD with respect to all the excitations used in this study.

• Journal of muscle and joint health
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• v.18 no.2
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• pp.270-281
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• 2011

Purpose: This study was done to determine if osteoarthritis (OA) patients living in rural Korea would have a benefit from a structured group program focused on self-help strategies. Methods: A hundred and twenty-six patients with OA were recruited from nine Primary Health Care Posts. The experimental group received a 6-week self-help education program while the control group received usual care. T-tests and c2-tests were used to determine the homogeneity between the experimental and control groups. Independent sample t-tests were performed to determine the effect of the treatment program. To guard against such likelihood, the level of significance of t-test was determined by Bonferroni correction within the study constructs. When significant group differences were found in study variables at baseline, analysis of covariances (ANCOVAs) were used for group comparisons of outcome variables. Results: The experimental group reported more significant improvement in fatigue, difficulty with physical activity, depression, quality of life, self-efficacy, and health behaviors than did the control group. The experimental group also showed improvements in range of motion and muscle strength as compared to the control group. Conclusion: A self-help group education program was an effective and powerful strategy to promote physical and psychosocial health in OA patients

• Journal of muscle and joint health
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• v.21 no.2
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• pp.97-105
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• 2014

Purpose: The purpose of this study was to identify the effects of an aquatic exercise program on physical fitness, body composition, and gait characteristics using trunk and pelvic angle in women living in urban fringe area. Methods: An aquatic exercise program consists of exercise in a swimming pool and self-help group activity with 16 women living in urban fringe (mean age: 63 years) for 8 weeks (twice a week for 2 hours). Physical fitness, body composition, trunk and pelvic angle using 2D video motion analyzer, and a questionnaire including socio-demographic variables were measured from July to August, 2013. Data were analyzed using a paired t-test with the SPSS/WIN 18.0 program. Results: At the end of 8 weeks intervention, there were significant decreases on body weight (p=.025), body fat (p=.030) and BMI (p=.011). There were significant increases on muscle strength (p=.001) and flexibility (p=.015). Trunk angle was significantly improved, which means participants less moved their body from side to side when they walked (p=.001). Conclusion: From this results, the aquatic exercise program could be an effective nursing intervention to improve physical fitness, body composition, and gait ability for women living in urban fringe area.