• Structural Engineering and Mechanics
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• v.9 no.6
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• pp.601-613
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• 2000

Existing models for the shear strength degradation of reinforced concrete members present varied conceptual approaches to interpreting test data. The relative superiority of one approach over the others is difficult to determine, particularly given the sparseness of ideal test data. Nevertheless, existing models are compared using a suite of test data that were used for the development of one such model, and significant differences emerge. Rather than relying purely on column test data, the body of knowledge concerning degradation of concrete as a material is considered. Confined concrete relations are examined to infer details of the degradation process, and to establish a framework for developing phenomenologically-based models for shear strength degradation in reinforced concrete members. The possibility of linking column shear strength degradation with material degradation phenomena is explored with a simple model. The model is applied to the results of 7 column tests, and it is found that such a link is sustainable. It is expected that models founded on material degradation phenomena will be more reliable and more broadly applicable than the current generation of empirical shear strength degradation models.

• Geomechanics and Engineering
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• v.9 no.5
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• pp.601-618
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• 2015

Soil-reinforcement interaction mechanism is an important issue in the design of geosynthetic reinforced soil structures. This mechanism depends on the soil properties, reinforcement characteristics and interaction between these two elements (soil and reinforcement). In this work the shear strength of sand/geotextile interfaces were characterized through direct and simple shear tests. The direct shear tests were performed on a conventional direct shear device and on a large scale direct shear apparatus. Unreinforced sand and one layer reinforced sand specimens were characterized trough simple shear tests. The interfaces shear strength achieved with the large scale direct shear device were slightly larger than those obtained with the conventional direct shear apparatus. Notwithstanding the differences between the shear strength characterization through simple shear and direct shear tests, it was concluded that the shear strength of one layer reinforced sand is similar to the sand/geotextile interface direct shear strength.

• Transactions of Materials Processing
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• v.33 no.2
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• pp.123-131
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• 2024

Plastic, the main material of FFF-type 3D printing, exhibits lower strength compared to metal. research aimed at increasing strength is needed for use in various industrial fields. This study analyzed three X-shape infill patterns(grid, lines, zigzag) with similar internal lattice structure. Moreover, tensile test considering weight and printing time was conducted based on the infill line multiplier and infill overlap percentage. The three X-shape infill patterns(grid, lines, zigzag) showed differences in nozzle paths, material usage and printing time. When infill line multiplier increased, there was a proportional increase in tensile strength/weight and tensile strength/printing time. In terms of infill overlap percentage, the grid pattern at 50% and the zigzag and lines patterns at 75% demonstrated the most efficient performance.

• Journal of the Korean Ceramic Society
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• v.34 no.8
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• pp.877-885
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• 1997

The dependence of strength, crack growth, fracture mode and degree of domain rearrangement of PZT ceramics on poling strength were studied. The PZT [(Pb0.94Sr0.06)(Zr0.46Ti0.54)O3+Nb(trace)] specimens were poled at 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 kv/mm, and the strength of the specimens was measured by 3 point flexure system. The bending strength of the specimen decreased in different modes according to the bending directions; xz, zx and yz plane direction with x axis of the poling direction in Cartesian coordinate system. The strength differences between the directions increased as the poling strength increased. The fracture mode transferred to intergranular fracture mode from transgranular one as the poling strength increased. The mechanical breakdown occurred when the poling strength higher than 3 kV/mm was applied to the specimen. It was observed that the crack length increased in the normal direction to the poling direction, however, decreased in the parallel direction to the poling direction when the poled PZT specimen was indented by the Vickers indenter. However, the crack produced by indentation continuously was continuously increased little by little after indentation on the specimen. The domain rearrangement occurred as the poling strength increased and the domains were rearranged more effectively when the electric field was continuously increased little by little.

• Journal of Korean Academy of Nursing
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• v.36 no.1
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• pp.5-14
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• 2006

Purpose: This study was done to analyze the effects of an exercise program on body composition and physical fitness of obese female college students. Method: Data was collected from September 29, 2003 to December, 29, 2003. The research design was arandomized control group pretest-posttest experimental design. The subjects were college nursing students at K University. Forty four students, 20 in the experimental group and 24 ina control group, with more than $30\%$ body fat were randomly assigned. The subjects in the experimental group participated in an exercise program for 12 weeks, sixty minutes per session, five times per week. Body composition and physical fitness was measured by a body composition analyzer, cardiovascular endurance, muscle endurance, muscle strength(grip strength, back strength), flexibility, balance, agility(whole body reaction time) and power(standing long jump). Result: Body weight(F=4.76, p=0.035), body fat(kg)(F=5.68, p=0.022) and body mass index(F=5.73, p=0.021) of the experimental group were significantly different from the control group, but there were no significant differences in body fat($\%$), lean body mass, muscle mass and WHR. Back strength(F=6.50, p=0.015), flexibility(F=14.62, p=0.000), muscle endurance(F=7.98, p=0.007), power(F=5.76, p=0.02l) and balance(F=2.46, p=0.018) of the experimental group were significantly different from the control group, but there were no significant differences in cardiovascular endurance, grip strength or agility. Conclusiton: The exercise program was effective in improving body weight, body fat(kg), body mass index, back strength, muscle endurance, flexibility, balance and power of obese female college students.

• The Journal of Advanced Prosthodontics
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• v.6 no.2
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• pp.115-120
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• 2014

PURPOSE. The aim of this in vitro study was to evaluate the effect of aging on the tear strength and cytotoxicity of four soft denture lining materials. MATERIALS AND METHODS. Four commonly used soft denture lining materials, (Coe-Comfort$^{TM}$ GC America Inc., Alsip, IL, USA; Coe-SOFT$^{TM}$ GC America Inc., Alsip, IL, USA; Visco-gel Dentsply Caulk Milford, DE, USA; and Sofreliner Tough M Tokuyama Dental Corporation Tokyo, Japan) were selected. Sixty trouser-leg designed specimens per lining material were fabricated using a stainless steel mold for tear strength testing. The specimens were divided into non-thermocycling and 1000-, and 3000-thermocycling groups. For the cytotoxicity test, twenty-four disk shaped specimens per material were fabricated using a stainless steel mold. The specimens were soaked in normal saline solution for 24 h, 48 h and 72 h. Cytotoxicity was measured by XTT assay in L929 mouse fibroblasts. Data were analyzed by two way analysis of variance and Dunnett's test (P<.05). RESULTS. Before thermocycling, Sofreliner Tough M ($10.36{\pm}1.00N$) had the highest tear strength value while Coe-Comfort$^{TM}$ ($0.46{\pm}0.10N$) had the lowest. After 3000 cycles, Sofreliner Tough M ($9.65{\pm}1.66N$) presented the highest value and Coe-Comfort$^{TM}$ ($0.42{\pm}0.08N$) the lowest. Sofreliner Tough M, in all incubation periods was the least toxic with significant differences compared to all other materials (P<.05). Coe-Comfort$^{TM}$, Coe-$SOFT^{TM}$, and Sofreliner Tough M did not show any significant differences within their material group for all incubation periods. CONCLUSION. This in vitro study revealed that aging can affect both the tear strength and cytotoxicity of soft denture materials depending on the composition.

• Journal of the Korean Society of Physical Medicine
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• v.14 no.3
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• pp.81-89
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• 2019

PURPOSE: To solve the problems of chronic obstructive pulmonary disease (COPD) patients complaining of muscle fatigue and having limited motor abilities, this study provided the clinical basic data for pulmonary rehabilitation by examining the effects of High Low-Frequency Neuromuscular Electrical Stimulation (NMES) on the respiratory muscle strength, quadriceps muscle activity, and life quality. METHODS: Samples were collected from 20 COPD patients and placed randomly in a low-frequency group (n=10) and high-frequency group (n=10). For a pretest, the respiratory muscle strength (MIP, MEP), quadriceps muscle activity (LF, VM, VL), and life quality (SGRQ) were measured. After applying NMES to each group for 30 minutes at a time, five times a week, for four weeks, a posttest was conducted in the same way as the pretest. RESULTS: Both groups showed significant differences in the respiratory muscle strength, quadriceps muscle activity, and quality of life within the groups and there were significant differences in the quadriceps muscle activity between the groups. CONCLUSION: The four-weeks NMES positively influenced the respiratory muscle strength and life quality by enhancing the function of the quadriceps and exercise tolerance. In particular, high-frequency(75 Hz) NMES was more effective than low-frequency (15 Hz) NMES. This result can be an alternative means to improve the physical functions of COPD patients clinically in the future.

• PNF and Movement
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• v.19 no.1
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• pp.105-113
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• 2021

Purpose: The purpose of this study was to investigate the effect of trunk-stabilization training using stabilizing reversal and rhythmic stabilization techniques of PNF on trunk muscle strength and respiratory function in elderly stroke patients. Methods: There were 26 stroke patients included in the study. Patients were divided into two groups, and all patients performed exercise 30 min five times per week for six weeks. The experimental group performed trunk stability exercise using stabilizing reversal and rhythmic stabilization techniques of PNF, and the control group performed flexibility and strength training. Trunk muscle strength, forced vital capacity, maximum inspiratory pressure, and maximum expiration pressure were measured to determine the changes after the intervention. For statistical processing, a paired t-test was performed within the group, and the value after intervention was performed as an independent t-test to find out the difference between the two groups. Results: In the experimental group, all of the trunk muscle strength, forced vital capacity, maximum inspiratory pressure, and maximum expiration pressure showed significant differences according to the intervention. In the control group, there were statistically significant differences in trunk muscle strength and forced vital capacity, but the maximum inspiratory pressure and the maximum expiration pressure did not show any statistical change. Conclusion: From these results, it can be seen that the trunk stability exercises that use the proprioceptive neuromuscular promotion method of stable reversal and rhythm stabilization can be a good intervention for the respiratory function of stroke patients.

• Journal of the Korean Society of Physical Medicine
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• v.16 no.2
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• pp.9-21
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• 2021

PURPOSE: This study examined the effects of an eight weeks twenty meters walk on the cardiorespiratory fitness and strength of the shoulder extensor, hip extensor, and dorsiflexor of stroke survivor outpatients in two tertiary hospitals in Osogbo, Nigeria. METHODS: A purposive sampling technique was used to select 21 registered right or left outpatient hemiplegic stroke survivors in a pre- and post-test experimental research design. The research questions were presented using the descriptive statistics of frequency, percentage, mean, and standard deviation. The differences between the mean of the cardio-respiratory indices and the muscle strength were tested by repeated measures analysis of variance followed by Bonferroni post-hoc test for multiple comparisons. RESULTS: No significant differences in heart rate were observed at week 0 compared to week 4. A significant decrease was recorded in the parameter at week 8, compared to week 4. Moreover, there were significant decreases in blood pressure and respiratory rate in week 0, compared to week 4, and in the respiratory rate, compared to week 8. In contrast, significant elevations in VO2 max were observed in week 0, compared to week 4, and in the week 4, compared to week 8. Furthermore, significant elevations in muscular strength were documented when comparisons were made at weeks 0, 4, and 8. CONCLUSION: Eight weeks of twenty meters walk aerobic exercise improve the cardio-respiratory fitness and muscular strength of stroke survivor outpatients.

• Journal of The Korean Society of Integrative Medicine
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• v.3 no.2
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• pp.55-61
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• 2015

Purpose: The purpose of this study was to investigate the effect of regularly strength exercise of spine in teenagers with tutor. Method: Study subjects were 24 middle school students. They were arranged to 2 groups(n=12, respectively). Then experimental group did regularly strength exercise of spine as the handout maneuver during 50min/day and 1day/week in 8 weeks with tutor, but control group did regularly exercise of spine as same maneuver without tutor. For muscle strength of both extensor and flexor of lumbar, the balancing ability and weight distribution index were measured before and after the intervention. Results: For muscle strength of both extensor and flexor of lumbar, there was not significant differences after the intervention, but both flexor and extensor increase mean value of muscle strength than control group. For balancing ability and weight distribution index, there were not significant difference after intervention(p>.05), but experimental group show a tendency to decrease in a few position than control group. Conclusion: When teenagers regularly exercise for spine strengthening for a long time with tutor, it may be increased muscle strength of lumbar and trunk balance.