• Geomechanics and Engineering
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• 제25권1호
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• pp.17-30
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• 2021

This paper develops a convenient approach for deterministic and probabilistic evaluations of tunnel face stability using support vector machine classifiers. The proposed method is comprised of two major steps, i.e., construction of the training dataset and determination of instance-based classifiers. In step one, the orthogonal design is utilized to produce representative samples after the ranges and levels of the factors that influence tunnel face stability are specified. The training dataset is then labeled by two-dimensional strength reduction analyses embedded within OptumG2. For any unknown instance, the second step applies the training dataset for classification, which is achieved by an ad hoc Python program. The classification of unknown samples starts with selection of instance-based training samples using the k-nearest neighbors algorithm, followed by the construction of an instance-based SVM-KNN classifier. It eventually provides labels of the unknown instances, avoiding calculate its corresponding performance function. Probabilistic evaluations are performed by Monte Carlo simulation based on the SVM-KNN classifier. The ratio of the number of unstable samples to the total number of simulated samples is computed and is taken as the failure probability, which is validated and compared with the response surface method.

• International Journal of Precision Engineering and Manufacturing
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• 제9권2호
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• pp.3-7
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• 2008

Vibratory conveyors are widely used in industry to transport granular materials and products. A theoretical point mass model for vibratory conveying was studied. The results agreed well with experimental observations. The model theory included the resting, sliding and flight states of the material. Each state was considered separately when determining the equations of motion. For the coefficients of restitution, values of zero for the normal component and 0.8 for the tangential component were found to be appropriate for modeling the collisions of the granular particles with the conveying surface. The vibration angle had a large influence on the mode and rate of transport. There was an optimum vibration angle for a given set of conditions. The optimum vibration angle decreased and was better defined as the coefficient of friction increased. The results suggest the existence of an optimum dimensionless track acceleration (throw number), which does not support general industrial practice in which the track acceleration is limited when the feed cycle becomes erratic and unstable.

• 대한정형도수물리치료학회지
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• 제29권1호
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• pp.41-52
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• 2023

Background: Bulgarian split squat (BSS) is beneficial to improve dynamic balance ability and muscle activity of lower extremities, however its effects have not been fully investigated. Therefore, this study aimed to compare changes in dynamic balance ability and muscle properties according to various modifications of BSS exercises. Methods: Thirty healthy male volunteers participated in this study, and they were randomly divided into three different groups. The subjects performed the BSS exercise either on a stable surface with the eyes opened (n=10) or eyes closed (n=10), and on an unstable support plane with eyes opened (n=10) conditions, respectively. Dynamic balance ability was measured via Biodex balance system under the eyes-opened and closed conditions. Additionally, muscle properties of the rectus femoris (RF), vastus medialis (VM) and vastus lateralis (VL) were evaluated. Results: Dynamic balance ability did not show the significant differences among the groups that performed the BSS exercises. However, in the Unstable group, there were significant differences in the overall stability index and anterior posterior stability index under the eyes-closed condition between pre-exercise and post-exercise. In comparison of muscle properties according to the groups, RF muscle showed a significant difference in amount of change of elasticity (p=.038). Additionally, there were significant changes in post measurements of VM muscle tone (p=.016), stiffness (p=.012) and elasticity (p=.002). VL muscle, however had no significant differences in muscle properties. Conclusion: These results indicate that BSS exercises could induce the alteration of RF and VM muscle properties, in particular VM muscle which is susceptible to weakness. Thus, BSS could be applied in various ways as an effective rehabilitation exercise.

• Physical Therapy Rehabilitation Science
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• 제4권1호
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• pp.11-16
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• 2015

Objective: Prone bridge exercise is one of the core strengthening exercise for improving abdominal, lower and upper extremity muscles. In addition, coactivation of the trunk muscles and extremities is important for treatment of low back pain. This study aimed to investigate the correlation between the thickness, cross-sectional area of the target muscle, and endurance during prone bridge exercise. Our hypothesis was that an increase in muscle thickness is positively related to the hold time for the static prone bridge exercise. Design: Cross-sectional study. Methods: Fourteen healthy university students (8 men and 6 women) voluntarily participated in the study at Sahmyook University. Hold time for the prone bridge with one and both legs was measured. The resting and contracted thickness of the lateral abdominal, rectus femoris, and triceps muscles was measured using rehabilitative ultrasound imaging. The correlation between muscle thickness and endurance for maintenance time was evaluated. Results: The prone bridge with both legs and the contraction thickness of the triceps muscle showed a positive correlation (r=0.692, p<0.05); the prone bridge with one leg and the contraction thickness of the internal oblique and transversus abdominis muscles showed a positive correlation (r=0.545, 0.574, p<0.05, 0.05, respectively). Conclusions: Endurance for the prone bridge exercise with a stable support surface is correlated with the contraction thickness of arm muscles; the prone bridge exercise with an unstable support surface is correlated with the contraction thickness of the deep abdominal muscles.

• 대한물리치료과학회지
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• 제29권1호
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• pp.64-72
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• 2022

Background: The purpose of this study is to investigate the effect of wall squat exercise according to the difference in the support surface on the thickness change of external oblique, internal oblique and transverse abdominalis of the trunk muscles and the change in distance of center of pressure when the eyes are opened and closed. Design: Randomized controlled trial. Methods: The subjects were 26 healthy adults, 18 males and 8 females. The composition of each group using the single-blind method was 13 people in the unstable side wall squat exercise group and 13 people in the stable side wall squat exercise group. Experimental measurements were divided into before, 3 weeks, and 6 weeks after the experiment, and changes in muscle thickness and balance were confirmed. Muscle thickness was measured using ultrasinic, and static balance change was measured using Bio-rescue. Results: There were significant differences in the thickness changes of external oblique, internal oblique and transverse abdominalis according to the wall squat exercise method by period and in the interaction between the period and the group (p<0.05). As a result of the post-hoc analysis, there was a significant difference in the change between the two groups in external oblique muscle after 6 weeks. And there was a significant difference in the distance of the pressure center between eyes open and closed eyes (p<0.05). Conclusion: In terms of instability, wall squat exercise was positive for changes in trunk muscle thickness. It suggests the possibility of using it for trunk muscle strengthening training in the future.

• 한국전문물리치료학회지
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• 제26권1호
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• pp.67-74
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• 2019

Background: Uncontrolled lumbopelvic movement leads to asymmetric symptoms and causes pain in the lumbar and pelvic regions. So many patients have uncontrolled lumbopelvic movement. Passive support devices are used for unstable lumbopelvic patient. So, we need to understand that influence of passive support on lumbopelvic stability. It is important to examine that using the pelvic belt on abdominal muscle activity, pelvic rotation and pelvic tilt. Objects: This study observed abdominal muscle activity, pelvic rotation and tilt angles were compared during active straight leg raise (ASLR) with and without pelvic compression belt. Methods: Sixteen healthy women were participated in this study. ASRL with and without pelvic compression belt was performed for 5 sec, until their leg touched the target bar that was set 20 cm above the base. Surface electromyography was recorded from rectus abdominis (RA), internal oblique abdominis (IO), and external oblique abdominis (EO) bilaterally. And pelvic rotation and tilt angles were measured by motion capture system. Results: There were significantly less activities of left EO (p=.042), right EO (p=.031), left IO (p=.039), right IO (p=.019), left RA (p=.044), and right RA (p=.042) and a greater right pelvic rotation angle (p=.008) and anterior pelvic tilt angle (p<.001) during ASLR with pelvic compression belt. Conclusion: These results showed that abdominal activity was reduced while the right pelvic rotation angle and anterior pelvic tilt angle were increased during ASLR with a pelvic compression belt. In other words, although pelvic compression belt could support abdominal muscle activity, it would be difficult to control pelvic movement. So pelvic belt would not be useful for controlled ASLR.

• 대한물리치료과학회지
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• 제29권3호
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• pp.48-55
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• 2022

Background: The purpose of this study is to examine the effect of push-up plus exercise on the changes in the thickness of the trapezius trapezius, serratus anterior and pectoralis major muscles involved in shoulder stability in various support surfaces. Design: Randomized controlled trial. Methods: The thickness change of the shoulder stabilizing muscle was measured using an ultrasound device. Corresponding t-test was performed to confirm the change within the group before the experiment and after 5 weeks. And one-way ANOVA was used to confirm the change between groups after 5 weeks. As a post hoc test, the least significant difference test was performed, and the significance level was set to a=0.05. Results: Changes in the thickness of the trapezius muscle within the group were significantly different between UPEG and SPEG after 5 weeks (p<0.05), and there was a significant difference between groups after 5 weeks (p<0.05). Changes in the thickness of the serratus anterior and pectoralis major muscle within the group were significantly different after 5 weeks in PEG, UPEG and SPEG (p<0.05), and the changes between the groups were significantly different in the serratus anterior muscle after 5 weeks (p<0.05). Conclusion: From the results of this study, it was found that the push-up exercise on an unstable support surface was effective for strengthening the trapezius upper and serratus anterior. This study intends to suggest the possibility of application as basic data for a push-up plus exercise program in clinical practice.

• 대한통합의학회지
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• 제11권4호
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• pp.51-60
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• 2023

Purpose : The purpose of this study was to determine the effect of pelvic floor muscle exercise (PFME) on an unstable support surface on maximal inspiratory pressure (MIP), maximum expiratory pressure (MEP), and abdominal muscle thickness as a method for effective PFME. Methods : This study was performed on 22 subjects. They were matched and divided into two groups based on body mass index; the experimental group (EG) performed PFME on a foam roller (n= 11), the control group (CG) performed PFME on a stable support surface (n= 11). Kegel exercise was performed with 10 seconds of contraction, 10 seconds of relaxation, and 4 sets of 10 reps per set. Both of group executed the exercise 3 times a week for 2 weeks. MIP and MEP was measured using a spirometer. Abdominal muscle thickness was measured using ultrasound. The paired t-test was used to compare difference on each group and the comparison between groups was analyzed using the independent t-test. A significance level of α= .05 was used to verify statistical significance. Results : The EG showed a significant increase in the MEP (p<.05). The CG showed a significant increase in the MEP (p<.05). There was no significant difference in the two groups (p>.05). The EG showed a significant increase in the external oblique, internal oblique and transverse abdominis (p<.05). The CG showed a significant increase in the internal oblique (p<.05). There was no significant difference in the two groups (p>.05). Conclusion : Based on the results of this study, additional research should be conducted to correct the limitations of this study to confirm that PFME performed on a foam roller has a positive effect on respiratory muscle strength and abdominal muscle thickness.

• The Journal of Korean Physical Therapy
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• 제1권1호
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• pp.15-25
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• 1989

The purpose of this study was to determine the factors influencing the standing balance of independent ambulatory hemiparetic patients. The subjects of this study were 30 hemiparetic patients (18 males, 12 females) being treated as admitted or out patients at Severance Hospital Medical Center, all of whom agreed to participate in the study. In order to assure the statistical significance of the results, the paired t-test aid a Pearson's correlation were applied at the .05 level of significance. The results were as follows. 1. The difference in maintenance time of standing balance on a stable and unstable support surface was significant at the .05 level. 2. The difference in maintenance time of standing balance according to the control of visual and acoustic stimuli was significant at the .05 level. 3. The presence or absence of passive joint motion sense influenced the standing balance maintenance time. 4. There was no significant difference in the maintenance standing balance of the sound tower leg standing conditions according to spasticity, but the paretic lower leg standing conditions were significantly different (p<.05). This type of evaluation should be more widely used in the field of evaluating standing balance with hemiparetic patients. However, more extensive study and reports on various factors of standing balance are needed.

• 대한통합의학회지
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• 제6권4호
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• pp.39-45
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• 2018

Purpose : The purpose of this study is to investigate the effect of core motion pattern on abdominal muscle thickness on unstable support surface using sling suspension system and to provide an effective exercise program for therapeutic rehabilitation in clinical practice. Methods : In this study, we used the flank exercise using a sling. It was intended for 21 healthy men and 9 healthy women. Before and after the exercise of the subjects, abdominal muscles (EO, IO, TrA the thickness of the muscle) was determined using a diagnostic ultrasonic apparatus. The period of exercise was 3 times a week for 6 weeks. The exercise for each group started with 3 sets per week and 1 set per week was added. A description of the method and attitude of each exercise is as follows. First, the push-up flank 's exercise position is to put both feet on the sling and hold the floor with both hands. Second, the side flank's exercise postures take the side flanks, while the two legs hang on the sling and one arm supports the body with an articulated bend (about $90^{\circ}$). Third, the elbow flank's exercise position is to put the two legs on the sling, and take a flank posture with the arms bent and joint bending (about $90^{\circ}$). Results : There was a significant difference in the thickness of the muscle in the three flank movements after the exercise (p<.05). The most significant difference was in the change of the muscle thickness in the abdominal muscle, the outer muscle, and the stomach in the elbow flank exercise after exercise. There was a significant difference between the mean thickness of the abdominal muscles according to the flank type after exercise (p<.05). Conclusion : In flank exercise for core stabilization using sling, it is considered effective to strengthen the abdominal muscles by considering the support surface, difficulty level, change of movement pattern.