• Neurospine
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• v.15 no.4
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• pp.323-328
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• 2018

The author reviews the various types of cervical fusion that are associated with instability of the craniovertebral junction. Assimilation of the atlas, C2-3 fusion, the Klippel-Feil abnormality, and pancervical fusion are amongst the more common types of bone abnormalities. It is conceptualised that these types of cervical fusion are not related to any kind of embryological dysgenesis or fault, but instead emerge due to longstanding muscle spasms of the neck in response to atlantoaxial instability. Such bone fusions could be secondary protective responses to longstanding atlantoaxial instability.

• Korean Journal of Childcare and Education
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• v.13 no.6
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• pp.21-41
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• 2017

Objective: The purpose of this study was to examine the direct and indirect effects of mothers' and children's emotional instability and maternal affectionate-rational parenting on children's attributional style. Methods: The participants of this study were 253 4th, 5th and 6th grade elementary school students and their mothers in Seoul and Incheon. Data were analyzed by path analysis using AMOS 21.0. Results: The results were as follows: First, children's attributional style for negative and positive events was significantly related to children's emotional instability and maternal affectionate-rational parenting. Also, mothers' and children's emotional instability was significantly associated with affectionate-rational parenting. Second, mothers' emotional instability had indirect effects on children's attributional style for negative and positive events through maternal affectionate-rational parenting. Finally, children's emotional instability had not only significant effects on children's attributional style for positive achievement events, but also indirect effects on children's attributional style for negative and positive events through maternal affectionate-rational parenting. Conclusion/Implications: The results of this study suggest that both environmental and individual factors, including mothers'and children's emotional instability and maternal affectionate-rational parenting, need to be considered to explain children's attributional style. Also, these findings have implications for developing intervention programs for children's attributional style and parental education.

• Journal of Labour Economics
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• v.28 no.3
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• pp.111-139
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• 2005

This study analyzed employment instability, defining the increase of employment instability as 'a greater possibility of losing a job and a declining possibility of re-employment'. Flow variable measurements showed that the extent of employment instability was higher post 2000 compared to the period of before financial crisis. When considering the status of workers, such an increase in employment instability can be characterized by a greater possibility of unemployment for daily workers. If this is examined in conjunction with job creation and destruction, employment instability is increased not because there are less jobs being created but because there is an actual decline in the number of jobs and also because the jobs that are being created are mostly temporary. On the other hand the increased instability is due to the large-scaled public work policy under the financial crisis.

• Korea-Australia Rheology Journal
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• v.20 no.1
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• pp.15-26
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• 2008

It has been known that there is a viscoelastic instability in the channel flow past a cylinder at high Deborah (De) number. Some of our numerical simulations and a boundary layer analysis indicated that this instability is related to the shear flow in the gap between the cylinder and the channel walls in our previous work. The critical condition for instability initiation may be related to an inflection velocity profile generated by the normal stress near the cylinder surface. At high De, the elastic normal stress coupling with the streamline curvature is responsible for the shear instability, which has been recognized by the community. In this study, an instability criterion for the flow problem is proposed based on the analysis on the pressure gradient and some supporting numerical simulations. The critical De number for various model fluids is given. It increases with the geometrical aspect ratio h/R (half channel width/cylinder radius) and depends on a viscosity ratio ${\beta}$(polymer viscosity/total viscosity) of the model. A shear thinning first normal stress coefficient will delay the instability. An excellent agreement between the predicted critical Deborah number and reported experiments is obtained.

• Journal of The Korean Society of Integrative Medicine
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• v.5 no.2
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• pp.1-10
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• 2017

Purpose : This study was aimed at investgating the effect of short foot exercise(SFE) using an imagery technique on chronic ankle instability(CAI). Methods : Twenty subjects with chronic ankle instability were selected by using the Cumberland ankle instability tool. They were randomly assigned to one of two groups(10 in each group) : namely the short foot exercise group and imagery technique group. The short foot exercise group performed short foot exercise for 6 weeks(3 times a week, 15 min per session). The imagery technique group performed short foot exercise(3 times a week, 15 min per session) and the imagery technique(3 times a week, 5 min per session) for 6 weeks. We measured chronic ankle instability, balance and threshold of vibration sensation before and after exercise by using the Cumberland ankle instability tool, Biodex Balance System and VSA-II, respectively. Results : We found statistically significant differences in cumberland ankle instability tool, balance and threshold of vibration sensation between the groups(p<.05). Conclusion : We confirmed the effect of short foot exercise using an imagery technique. Thus, we thought these results could be used as basic data and reference for musculoskeletal therapy or intervention using an imagery technique.

• Journal of International Academy of Physical Therapy Research
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• v.11 no.2
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• pp.2036-2041
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• 2020

Background: Ankle sprain in the Lead Leg Side (ALLS) is common in fencing athletes, and studies comparing the ankle range of motion (ROM) and strength of both legs are insufficient. Objectvies: To compare the ankle ROM and hip strength between two legs in fencing athletes who has ankle instability in the lead leg side. Design: Cross-sectional design. Methods: Seven fencing athletes with ankle instability participated in this study, and they randomly assigned into ankle in the Lead Leg Side (ALLS) and ankle in the Rear Leg Side (ARLS). Instability was determined by the Cumberland Ankle Instability Tool (CAIT), and then joint ROM and hip muscle strength were measured. Results: There were significant differences in dorsiflexion ROM, hip strength (extension and abduction) between the ALLS with ankle instability and ARLS (P<.05). Conclusion: This study suggests that the ankle ROM and hip muscle strength of ARLS are greater than ALLS in fencing athletes with ankle instability.

• Geomechanics and Engineering
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• v.9 no.6
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• pp.729-742
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• 2015

The aim of the present work was the study of instability in a loose sand from Les Dunes beach in Ain Beninan, Algeria, where the Boumerdes earthquake occurred in 2003. This earthquake caused significant structural damages and claimed the lives of many people. Damages caused to infrastructures were strongly related to phenomena of liquefaction. The study was based on the results of two drained and six undrained triaxial tests over a local sand collected in a region where liquefaction occurred. All the tests hereby analyzed followed compression stress-paths in monotonic conditions and the specimens were isotropically consolidated, since the objective was to study the instability due to static loading as part of a more general project, which also included cyclic studies. The instability was modeled with the second-order work increment criterion. The definition of the instability line for Les Dunes sand and its relation with yield surfaces allowed the identification of the region of potential instability and helped in the evaluation of the susceptibility of soils to liquefy under undrained conditions and its modeling. The dilatancy rate was studied in the points where instability began. Some mixed tests were also simulated, starting with drained conditions and then changing to undrained conditions at different time steps.

• Journal of the Korean Society of Physical Medicine
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• v.10 no.4
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• pp.39-48
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• 2015

PURPOSE: This study aimed to compare the degree of lumbopelvic rotation during the active straight leg raise (ASLR) test in chronic low back pain with and without lumbar segmental instability. METHODS: A total of 71 patients with chronic low back pain were recruited for this study. The subjects who tested positive for more than three of the five lumbar segmental instability tests (prone lumbar instability, lumbar passive extension test, anterior posterior mobility test, passive straight leg raise, age) were categorized into the lumbar segmental instability positive group. Patients who tested positive for less than three of the five tests were categorized into the lumbar segmental instability negative group. The lumbopelvic rotation was measured three times during ASLR and a mean was determined. Subjective heaviness during the ASLR was measured on 6 point scale. RESULTS: There was a statistically significant difference in the lumbopelvic rotation angle between the groups with and without lumbar segmental instability (p<.01). There was no significant difference in the subjective heaviness during ASLR. The mean lumbopelvic rotation angle during ASLR was $13.54{\pm}2.86^{\circ}$, and $8.81{\pm}2.47^{\circ}$ in the positive and negative groups, respectively (p<.01). The cut-off value of the lumbopelvic rotation during was $10.5^{\circ}$, the sensitivity was 82.9%, and the specificity was 80.6%. CONCLUSION: These results suggest that lumbopelvic rotation is more prevalent in patients without lumbar segmental instability. Clinically, this important when diagnosing chronic low back pain with lumbar segmental instability, as the lumbopelvic rotation angle during the ASLR test can be used to aid in diagnosis.

• Journal of Mechanical Science and Technology
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• v.16 no.7
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• pp.1019-1028
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• 2002

The instability of two-phase loop thermosyphons was investigated experimentally and analytically. Three orifice type inserts were used to study the effect of change in the pressure drop in the flow channel of the TLT on the flow instability and temperature fluctuation. It is observed that a decrease in the size of the orifice insert from 3.7 mm (no insert) to 0.71 mm drastically reduced the fluctuation of the temperature, especially at the evaporator section of the TLT. With the orifice type insert of 0.71 mm for the TLT, the overall temperature fluctuation was almost completely eliminated, especially at higher power input to the TLT The analysis based on the Kelvin-Helmholtz instability theory seems to predict reasonable well the loop stability state of the TLT with experimentally determined constant factors.

• 한국연소학회:학술대회논문집
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• 2003.05a
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• pp.209-214
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• 2003

The Saffman-Taylor instability mechanisms in laminar premixed flames in a Hele-Shaw cell are investigated using two-dimensional numerical simulations with Poiseuille assumption for the viscous effect. The baseline calculations considering the Darrieus-Landau and diffusive-thermal instability modes show the results consistent with the classical linear instability theory. With the Saffrnan-Taylor instability mechanism. the overall effect is to enhance the destabilizing mechanism by providing an increased viscous force in the product gas. The linear instability behavior is found to qualitatively similar to the Darrieus-Landau mechanism. However, the results in the nonlinear range demonstrate that there may exist distinct characteristic time scales associated with Darrieus-Landau and Saffman-Taylor mechanisms, such that the latter effect sustains longer in time, contributing to a higher overall flame speed.