• Steel and Composite Structures
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• v.22 no.6
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• pp.1239-1259
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• 2016

The modified couple stress-based third-order shear deformation theory is presented for sigmoid functionally graded materials (S-FGM) plates. The advantage of the modified couple stress theory is the involvement of only one material length scale parameter which causes to create symmetric couple stress tensor and to use it more easily. Analytical solution for dynamic instability analysis of S-FGM plates on elastic medium is investigated. The present models contain two-constituent material variation through the plate thickness. The equations of motion are derived from Hamilton's energy principle. The governing equations are then written in the form of Mathieu-Hill equations and then Bolotin's method is employed to determine the instability regions. The boundaries of the instability regions are represented in the dynamic load and excitation frequency plane. It is assumed that the elastic medium is modeled as Pasternak elastic medium. The effects of static and dynamic load, power law index, material length scale parameter, side-to-thickness ratio, and elastic medium parameter have been discussed. The width of the instability region for an S-FGM plate decreases with the decrease of material length scale parameter. The study is relevant to the dynamic simulation of micro structures embedded in elastic medium subjected to intense compression and tension.

• Journal of Korean Foot and Ankle Society
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• v.25 no.1
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• pp.6-9
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• 2021

The term chronic lateral ankle instability (CLAI) embraces a spectrum of conditions that involve functional and mechanical instability, both in athletes and lower-demand patients. The hallmarks of CLAI are recurrent sprains, persistent pain, and repeated episodes of the ankle giving way. CLAI is the main complication of acute ankle sprains, which can cause discomfort in daily and sports activity. Approximately 10% to 30% of patients with acute ligament ruptures will develop chronic instability over the course of a year from the index injury. An accurate diagnostic approach and successful treatment plan should be established based on a comprehensive understanding of the concept of functional and mechanical instability. Unfortunately, the optimal modality for the management of CLAI is unclear. Even after conservative treatment or surgical intervention, it could result in degenerative changes to the ankle joint in the long term. Thus far, the incidence of ligamentous posttraumatic ankle osteoarthritis was reported to be 13% to 78%. The mean latency time between injury and osteoarthritis was at least 10 to 34.3 years. CLAI is an important pathological condition that can cause discomfort or dysfunction in daily activity in the short term, resulting in joint destruction in the long term. Therefore, it is important to understand the various complications that can occur when CLAI is not treated properly.

• Journal of Korean Foot and Ankle Society
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• v.25 no.1
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• pp.32-37
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• 2021

Patients with chronic lateral ankle instability often experience a range of associated injuries. The well-known comorbidities include intra-articular pathologies (osteochondral lesion, soft tissue or bony impingement, and loose body), peroneal tendon pathologies, neural injuries, and other extra-articular pathologies. Surgeons should have a high index of suspicion for these associated pathologies before operative intervention, correlate the clinical findings, and plan the treatment. Despite the restoration of ankle stability following ligament repair or reconstruction surgery, a high prevalence (13%~35%) of postoperative residual pain has been reported. This pain can negatively affect the clinical outcomes and patient satisfaction. This study examined the causes of persistent pain after surgical treatments for chronic ankle instability.

• Journal of The Korean Society of Integrative Medicine
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• v.10 no.1
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• pp.73-79
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• 2022

Purpose : Kinesio taping applied to the ankle varies, and if the overall ankle is taped as much as possible, several effects, including balance, can be expected, but clinically the cost reduction for intervention is very important. Therefore, this study attempted to find out the optimal way to the effect and cost of kinesio taping on ankle dynamic balance. Methods : The subject of this study was 24 university students in their 20s (male: 13, female: 11), who received sufficient explanation of the purpose and method of the study. The Cumberland ankle instability tool (CAIT) questionnaire was used for the degree of ankle instability of the study subjects. If the subject's CAIT score was 28 points or more, it was classified as a stable ankle, and if the score was 24 points or less, it was classified as functional ankle instability (FAI). In this study, Biodex Balance System^® measurement equipment was used to calculate the dynamic balance of study participants. The application of kinesio taping was performed by one physical therapist to attach in the same way, and a method of wrapping the ankle joint was applied in the eight-shaped bandage. Results : The results are as follows in before and after taping of the stable ankle and FAI group. There was no significant difference in the overall, anterior-posterior, and medial-lateral stability index. The comparison is as follows between groups for the differences (post-pre value) in before and after the application of kinesio taping. There were no significant differences between groups in all the overall, anterior-posterior, and medial-lateral stability index. Conclusion : In this study, no significant difference in kinesio taping was found in the dynamic balance of stable ankle and FAI (overall, anterior-posterior, and medial-lateral). It is necessary to continue to study ways to find the maximum effect while minimally attaching them to the application method of ankle kinesio taping.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1146-1151
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• 2004

Measurements of OH chemiluminescence in an atmospheric pressure, laboratory-scale dump combustor at equivalence ratios ranging from 0.63 to 0.89 were reported. The signal from the first electronically excited state of OH to ground state was detected through a band-pass filter with an ICCD. The objectives of this study are two: One is to see the effects of equivalence ratio on global heat release rate and local Rayleigh index distribution. To get the local Rayleigh index distribution, the line-of-sight images were inverted by tomographic method, such as Abel de-convolution. Another aim is to investigate the validity of using OH chemiluminescence acquired with an ICCD as a qualitative measure of local heat release. For constant inlet velocity and temperature, the overall intensities of OH emission acquired at different equivalence ratio showed periodic and higher value at high equivalence ratio. OH intensity averaged over one period of pressure increased exponentially with equivalence ratio. Local Rayleigh index distribution clearly showed the region of amplifying or damping the combustion instability as equivalence ratio increased. It could provide an information/insights on active control such as secondary fuel injection. Finally, local heat release rate derived from reconstructed OH images were presented for typical locations.

• Clinics in Shoulder and Elbow
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• v.23 no.2
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• pp.62-70
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• 2020

Background: Recent studies have reported high rates of recurrence of shoulder instability in patients with glenoid bone defects greater than 20% after capsulolabral reconstruction. The purpose of the present study was to evaluate the failure rate of arthroscopic capsulolabral reconstruction for the treatment of anterior instability in the presence of glenoid bone deficits >20%. Methods: Retrospective analyses were conducted among cases with anterior shoulder instability and glenoid bone defects of >20% that were treated by arthroscopic capsulolabral reconstruction with a minimum 2-year follow-up (30 cases). We included the following variables: age, bone defect size, instability severity index score (ISIS), on-/off-track assessment, incidence recurrent instability, and return to sports. Results: The mean glenoid bone defect size was 25.8%±4.2% (range, 20.4%-37.2%), and 18 cases (60%) had defects of >25%. Bony Bankart lesions were identified in 11 cases (36.7%). Eleven cases (36.7%) had ISIS scores >6 points and 21 cases (70%) had off-track lesions. No cases of recurrent instability were identified over a mean follow-up of 39.9 months (range, 24-86 months), but a sense of subluxation was reported by three patients. Return to sports at the preinjury level was possible in 24 cases (80%), and the average satisfaction rating was 92%. Conclusions: Arthroscopic soft tissue reconstruction was successful for treating anterior shoulder instability among patients with glenoid bone defects >20%, even enabling return to sports. Future studies should focus on determining the range of bone defect sizes that can be successfully managed by soft tissue repair.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.6
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• pp.869-876
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• 1994

This paper presents an efficient method to calculate voltage collapse point and to avoid voltage instability. To evaluate voltage stability in power systems, it is necessary to get critical loading points. For this purpose, this paper uses linear programming to calculate efficiently voltage collapse point. Also, if index value becomes larger than given threshold value, voltage stability is improved by compensation of reactive power at selected bus. This algorithm is verified by simulation on the IEEE 14-bus sample system.

• Journal of the Korean Geographical Society
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• v.41 no.2 s.113
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• pp.168-187
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• 2006

Windy meteorological conditions and dried fire fuels due to higher atmospheric instability and dryness in the lower troposphere can exacerbate fire controls and result in more losses of forest resources and residential properties due to enhanced large wildland fires. Long-term (1979-2005) climatology of the Haines Index reconstructed in this study reveals that spatial patterns and intra-annual variability of the atmospheric instability and dryness in the lower troposphere affect the frequency of wildland fire incidences over the Korean Peninsula. Exponential regression models verify that daily high Haines Index and its monthly frequency has statistically significant correlations with the frequency of the wildland fire occurrences during the fire season (December-April) in South Korea. According to the climatic maps of the Haines Index created by the Geographic Information System (GIS) using the Digital Elevation Model (DEM), the lowlands below 500m from the mean sea level in the northwestern regions of the Korean Peninsula demonstrates the high frequency of the Haines Index equal to or greater than five in April and May. The annual frequency of the high Haines Index represents an increasing trend across the Korean Peninsula since the mid-1990s, particularly in Gyeongsangbuk-do and along the eastern coastal areas. The composite of synoptic weather maps at 500hPa for extreme events, in which the high Haines Index lasted for several days consecutively, illustrates that the cold low pressure system developed around the Sea of Okhotsk in the extreme event period enhances the pressure gradient and westerly wind speed over the Korean Peninsula. These results demonstrate the need for further consideration of the spatial-temporal characteristics of vertical atmospheric components, such as atmospheric instability and dryness, in the current Korean fire prediction system.

• Journal of the Korean Regional Science Association
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• v.10 no.1
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• pp.53-70
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• 1994

The relationships between the Capital gains of housings by tenure, type and size have been analyzed. Major findings are (i) capital gain rate of 'chonsei' housing is larger than that of the owner occupied housing (ii) the small 'chosei' apartment has the highest capital gain rate and the lowest instability index (iii) the smaller the size of housings, the higher the capital gain rate and the smaller the instability index. Even though there is the 'structural change' in the capital gain rates of owner occupied and 'chonsei' housings, they are cointegrated. The capital gain of owner occupied housing is mainly affected by the real estate policies. But, The capital gain of 'chonsei' housing is mainly affected by the business cycle and the aggregate demand management policies.

• Journal of the Korean Society of Physical Medicine
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• v.19 no.2
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• pp.29-45
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• 2024

PURPOSE: This study aimed to compare the effects of pain level, lower back pain dysfunction level, psychosocial level, hip abductor strength (HAS), number of positive lumbar instability tests, and dynamic balance (DB) by applying lumbar stabilization exercises according to the presence or absence of gluteus medius muscle weakness in chronic lower back pain (CLBP) patients with lumbar instability. METHODS: Thirty-five CLBP patients with lumbar instability were divided into the gluteus medius weakness (n = 18) and gluteus medius non-weakened (n = 17) groups using the gluteus medius manual muscle test. Intervention applied conservative physical therapy and lumbar stabilization exercises to both groups that lasted three times a week for four weeks. To compare the intervention effects, the quadruple visual analog scale (QVAS), the Korean version of the Oswestry disability index (K-ODI), fear-avoidance beliefs questionnaire (FABQ), HAS, lumbar instability tests positive response counter (LIC), and DB were measured. RESULTS: Significant differences were shown for QVAS, K-ODI, FABQ, HAS, LIC, and DB for both groups pre- and post-intervention (p < .05). Compared to the gluteus medius weakness group, the gluteus medius non-weakened group showed a significant difference (p < .05) in the changes in QVAS, K-ODI, FABQ-W, FABQ-total, and HAS. CONCLUSION: In CLBP patients with lumbar instability, having gluteus medius weakness was less effective in improving lumbar stabilization exercise than gluteus medius non-weakness regarding pain level, lower back pain dysfunction level, psychosocial level excluding physical activity, and hip abductor strength. Therefore, additional gluteus medius strengthening exercises are necessary for patients with lumbar instability and gluteus medius muscle weakness.