• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.647-650
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• 2005

This paper is to investigate the shrinkage properties of ultra high strength concrete(UHSC) incorporating $5\%$ of expansive additives(EA) along with $1\%$ of shrinkage reducing agent(SRA). UHSC subjected to steam curing and incorporated with steel fiber exhibited higher compressive strength than control UHSC by as much as50MPa at 7days, while at 28days, noticeable change in compressive strength was not observed between UHSC mixtures. Control UHSC subjected to steam curing had a $922{\times}10^6$ of autogenous shrinkage strain value, which was 6.7 times of drying shrinkage strain value at 42 days. The combination of EA and SRA resulted in a decrease in autogenous shrinkage by as much as half of control mixture. Steam curing contributed to the reduction of autogenous shrinkage by as much as $11\%$ compared with that of standard curing.

• Transactions of Materials Processing
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• v.12 no.8
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• pp.718-723
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• 2003

Tn order to develop springback control technology for high-strength steel sheets, several studies have been conducted: dome stretching test, stepped s-rail forming and springback measurement, and optimally shaped initial blank design. First, to find out the formability of TRIP60, dome stretching test was performed. Next, the stepped s-rail die, which was designed to form a channel type panel with large twist and wall curl, was manufactured and used to evaluate the effect of controlling forming variables, such as blank holding force and flange amount on the springback. Furthermore, new measurement method of the springback was introduced to define wall curl and twist in geometrically complex panels. Finally, the optimally shaped initial blank was employed to verify one of the best ways to control the springback in channel type. high-strength sheet panels.

• Transactions of Materials Processing
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• v.25 no.3
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• pp.155-160
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• 2016

Magnesium(Mg) alloys have been evaluated as replacements for steel or aluminum parts in the automobile industry because of the fuel economy they can provide through reducing weight. The application of Mg alloys has been limited due to its low formability at room temperature, which results from a small number of active slip systems. In the current study, an extruded TAZ711(Mg-7Sn-1Al-1Zn) alloy was warm forged into an automotive control arm to evaluate its formability at various forging temperature. Warm forging was conducted at temperatures of 200, 250, 350 and 450℃. Static strength evaluation was performed on the as-forged specimen at 250℃. The results showed good static strength.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.228-229
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• 2007

As one way of weight saving of the vehicle, 1-piece typed lower control arm has been developed using high strength hot rolled steel sheet. In order to overcome the edge splitting problem during edge flanging or burring process, HER (hole expansion ratio) value of steel sheet was primarily considered. The strength grade of steel sheet and the shape were optimized utilizing Taguchi method.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.24 no.2
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• pp.59-67
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• 2018

Background: The purpose of this study was to investigate the effects of gluteus medius strength exercise on the ankle stability of high school student with chronic ankle sprains. Methods: A total of 30 participants were divided two groups. Experimental group was 15 participants applied gluteus medius strength exercise. Control group was 15 participants performing ankle strength exercise. This study was performed for 50 minutes per day, three a week for 6 weeks. All measurements were taken to a pre and post test. Strength was measured using Power Track ll. Balance was measured using Biodex balance system for Limits of Stability and Postural Stability. Ankle Stability was measured using Cumberland Ankle Instability Tool (CAIT). Results: In the case of gluteus medius strength, there were statistically significant differences between the experimental group and the control group. For ankle stability were statistically significant differences within the experimental group according to measurements taken by Limits of Stability, Postural Stability, and CAIT. A between group comparison showed a statistically significant difference for CAIT only. Conclusion: According to our measurements it appears that gluteus medius strength training was effective in benefiting muscular strength, balance and ankle stability among the physical education.

• Korean Journal of Applied Biomechanics
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• v.33 no.2
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• pp.45-51
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• 2023

Objective: The aim of this study was to examine the effect of strength training targeting medial quadriceps/hamstrings and non-targeting strength training on dynamic balance. Method: A total of 51 healthy subjects were randomly assigned to control, targeting strength training, or non-targeting training groups. To measure the dynamic balance, the star excursion balance test (SEBT) was performed before and after training. The SEBT parameters were compared using repeated measures ANOVA, and post-hoc paired t test at a significance level of 0.05. Results: Greater anterior (p= .011), anteromedial (p= .001), medial (p< .001), lateral (p< .001), and anterolateral (p= .001) reach distances were found between pre- and post-training in the strength training targeting medial thigh muscles group. Only greater lateral reach distance was found after non-targeting strength training (p= .029). In addition, no differences were found for any SEBT scores in the control group. Conclusion: Strength training targeting medial quadriceps and hamstrings can improve the dynamic balance, thereby it positively affected in lower extremity injury risk, whereas non-targeting strength training rarely changes the dynamic balance.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.5
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• pp.656-673
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• 2003

Statement of problem : Long-term exposure of dental porcelain to saliva during temporary cementation of a porcelain-fused to metal (PFM) restoration could affect mechanical strength of dental porcelain if the restoration is refired. Purpose : This work was performed to verify the effect of water on the mechanical strength in aged dental porcelain. Material and method : 63 specimens(Vintage Metalbond opaque and opal powder) were distributed to three experimental groups ; non-water immersed control, immersed and pedried, and immersed and non-predired groups. The changes in flexural strength and fracture toughness after specimen refiring related to Fourier Transform Infrared (FT-IR) spectroscopy. Results : 1. The FT-IR reflectances assigned to molecular bonds of $H_2O$ were noted as significantly different between the first-fired group and three refired groups and between two water-immersed groups and control group after refiring(p<0.05). They were also significantly different between predried group and non-predried group after refiring(p<0.05) 2. For opal specimens, FT-IR absorbances for hydrogen bond of $H_2O$ and silanols were significantly higher in non-predried group than in predreid group(p<0.05). 3 Predried opal group showed the highest mean flexural strength(p<0.05). Non-predried group indicated higher mean flexural strength than control group(p<0.05). 4. The mean fracture toughness for predired group was higher than non-predried group(p<0.05). 5. The difference of leucite crystal size is noted between control group and water-immersed, predried group in scanning electron microscopic study(${\times}10000$).

• Journal of Korean Academy of Nursing
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• v.30 no.3
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• pp.647-658
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• 2000

The purpose of this study was to determine the effect of Korean traditional dance movement training on balance, gait and leg strength in elderly women who are forced to remain at home. Fifteen elderly women of an experimental group between the ages 65 and 75 years who have normal vision and passed the hearing and Romberg test, participated in the 12 weeks' dance movement training. Fourteen subjects of a control group were selected. Korean traditional dance movement training was developed on the basis of Korean traditional dance and music by the authors. It took approximately 50 minutes to perform the dance movement program. The subjects of the experimental group practiced dance training for 3 times a week during 12 weeks. During the 50 minutes workout, the subjects practiced 15 minutes of a warm-up dance, 25 minutes of a conditioning dance, and 10 minutes of a cool-down dance. The intensity for the conditioning phase was between 60% and 65% of age-adjusted maximum heart rates. The balance, gait and leg strength were measured prior to and after the experimental treatment. Total balance scores of the experimental group were significantly higher than those of the control group. Scores of sternal nudge, one leg standing balance and reaching up among 13 items have significantly increased after the dance movement training. Total scores of gait of the experimental group were significantly higher than those of the control group following the korean traditional dance movement training. Scores of experimental group in step height, path deviation and turning while walking among 9 items have increased significantly following 12 weeks of dance movement training. The leg strength of experimental group was significantly higher than those of the control group following the Korean traditional dance movement training. The balance, gait and leg strength have significantly correlated in the experimental group following the Korean traditional dance movement training. The results suggest that Korean traditional dance movement training can improve balance, gait and leg strength in home bound elderly women.

• The Journal of Korean Physical Therapy
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• v.33 no.4
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• pp.202-209
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• 2021

Purpose: This study examined whether various lower extremity exercises using a Swiss ball in the standing position could improve balance, muscle strength, gait, and fall efficacy in stroke patients. Methods: Twenty-one stroke patients were randomly divided into three groups, each with seven participants. For four weeks, experimental group 1 performed various lower extremity exercises using a Swiss ball, while experimental group 2 executed the same exercises without a Swiss ball, and the control group underwent general physical therapy. The subjects' knee extensor muscle strength, balance, gait, and fall efficacy were evaluated before and after the intervention using portable muscle strength measurement, the Berg Balance Scale (BBS), G-walk, and the Korean Falls Efficacy Scale (K-FES). Results: Knee extensor strength increased significantly in all three groups after the intervention; in particular, a significant increase was seen in experimental groups 1 and 2 compared to the control group. Moreover, all three groups had significantly better BBS scores and higher cadence after the intervention; notably, experimental group 1 had better scores and increased cadence than the control group. Additionally, gait speed was significantly increased in the experimental group 1 than in the control group. The step length of the non-affected leg was also significantly higher in the same group. The K-FES score improved significantly in all three groups, but there was no significant difference between the groups. Conclusion: This study suggests that lower extremity exercises with or without a Swiss ball could be effective interventions to improve muscle strength, balance, gait, and fall efficacy in stroke patients.

• Journal of Korean Clinical Nursing Research
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• v.23 no.3
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• pp.388-397
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• 2017

Purpose: The purpose of this study was to explore the effects of the lower limb muscle strength exercise program during hemodialysis on the leg strength and falls efficacy (fall-related self-efficacy) of hemodialysis patients. Methods: The study was designed to be a quasi-experimental, nonequivalent control group pre and post test design. A total of 42 patients participated in the study. We applied lower limb muscle strength exercise program to the experimental group in every hemodialysis three times a week for 8 weeks. Data were analyzed using ${\chi}^2$ test, fisher's exact test, t-test and repeated measures ANOVA. Results: The mean age was 58 years old (t=-1.54, p=.132), the mean hemodialysis period was 67 months (t=1.949, p=.058) and there was no significant difference of dependent variable (t=1.17, p=.251)(t=-.89, p=.381) between the two groups before the experiment. After the experiment, leg strength was significantly improved in the experimental group compared to that of the control group (F=6.63, p=.004). However, falls efficacy was not significantly different between the experimental group and the control group (F=2.33, p=.104). Conclusion: The study results indicated that the lower limb muscle strength exercise program during hemodialysis may improve leg strength and potentially to prevent falls for hemodialysis patients. Further studies are warranted in which larger number of participants and longer duration of intervention are recommended.