• Advances in concrete construction
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• v.16 no.3
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• pp.127-139
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• 2023

In this study, the steel fiber and the polypropylene fiber were used to enhance the mechanical properties of fully recycled coarse aggregate concrete. Natural crushed stone was replaced with recycled coarse aggregate at 100% by volume. The steel fiber and polypropylene fiber were used as additive material by incorporating into the mixture. In this test two parameters were considered: (a) steel fiber volume ratio (i.e., 0%, 1%, 1.5%, 2%), (b) polypropylene fiber volume ratio (i.e., 0%, 0.1%, 0.15%, 0.2%). The results showed that compared with no fiber, the integrity of cubes or cylinders mixed with fibers after failure was better. When the volume ratio of steel fiber was 1~2%, the width of mid-span crack after flexural failure was 5~8 mm. In addition, when the volume ratio of polypropylene fiber was 0.15%, with the increase of steel fiber content, the static elastic modulus and toughness of axial compression first increased and then decreased, and the flexural strength increased, with a range of 6.5%~20.3%. Besides, when the volume ratio of steel fiber was 1.5%, with the increase of polypropylene fiber content, the static elastic modulus decreased, with a range of 7.0%~10.5%. The ratio of axial compression toughness first increased and then decreased, with a range of 2.2%~8.7%. The flexural strength decreased, with a range of 2.7%~12.6%. On the other hand, the calculation formula of static elastic modulus and cube compressive strength of fully recycled coarse aggregate with steel-polypropylene fiber was fitted, and the optimal fiber content within the scope of the test were put forward.

• Journal of the Ergonomics Society of Korea
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• v.30 no.5
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• pp.637-644
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• 2011

Objective & Background: When applying various evaluation tools that analyze work posture risk through observation, accurate measurement of body flexion angle is very important. Method: This study investigated differences and appropriateness of 5 different existing reference points commonly used in the analysis of the work posture. Twenty five ergonomist and trained professionals were participated in this study. A Same flexion angle was utilized for the evaluation of risk assessment of musculoskeletal disorders using five different reference points to investigate the degree of difference between them. To investigate how different the observers' preferred flexion angle measuring methods were compared to the ISO 11226 Reference Posture, a virtual body model was constructed using the Poser 6.0 program. Six types of body flexion postures were constructed, and since neck flexion differs according to body angle, five types of neck flexion postures were constructed with the trunk bending $20^{\circ}$ forward, making up a total of 30 virtual flexion postures. Results: Results showed that the observers used personally preferred reference points instead of reference points recommend in the evaluation tools. Also the results revealed the their seems to be 6 types of flexion angle for the trunk and 11 types of measurement methods for the neck flexion angle in the form of personally preferred reference points. The results showed that a mean difference of $14^{\circ}$($4{\sim}23^{\circ}$) occurred in the trunk, and a mean difference of $20^{\circ}$($-8{\sim}51^{\circ}$) occurred in the neck. To increase accuracy when using the 5 evaluation tools in combination, the ISO 11226 standards, observers' preferred flexion posture standards, and common flexion posture standards of the evaluation tools were compared with the reference points of the 5 evaluation tools. Results showed considerable variance in angle difference for each evaluation tool. Conclusion: According to the results of this study, considering the angle difference between the flexion angle reference points of the evaluation tool and the reference points selected by the observers, it is concluded that instead of personally preferred reference points, the standardized reference points to enhance the accuracy and the objectivity. Application: The result of this study can be used as reference guide to develop the standardized reference point in the future.

• Journal of Korea Entertainment Industry Association
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• v.13 no.6
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• pp.165-173
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• 2019

This study aims to examine the moderating effects of band circuit training for the mortality improvement of elderly women to provide an effective exercise moderating program for the enhanced quality of life of the elderly. To achieve the purpose of this study, the moderating effects of 8 weeks of band circuit training in the Senior Fitness Tests (SFT) and Sitting Rising Tests (SRT) of elderly women ages 65 and older in Y city were examined and the following results were gained. The functional fitness of elderly women according to the moderating effects of band circuit training (sitting down in a chair and standing up, lifting 2 kg dumbbells, walking in place for 2 minutes, sitting in a chair and bending forward, hand holding behind one's back, walking back and forth for 2.44 m) and the Sitting Rising Test (SRT) displayed statistically significant interaction effects among measurement times and groups and positive improvements were shown in the test group after band circuit training moderation. These research results show that band circuit training moderation has a positive effect on functional fitness and SRT, which are associated with the mortality rate of the elderly, and thus it can be applied as an effective exercise moderation program for the improvement of quality of life through the mortality improvement of the elderly.

• The korean journal of orthodontics
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• v.33 no.4 s.99
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• pp.235-245
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• 2003

The goal of the present study was to evaluate the effects of PNAM appliance and cheiloplasty on alveolar molding. Samples consisted of 16 unilateral cleft lip and palate infants (10 males and 6 female, mean age=37.0 days after birth, average alveolar cleft gap=10.46m), who were treated with PNAM appliances by one orthodontist and rotation- advancement cheiloplasty by one surgeon in Seoul National University Hospital. Average duration of alveolar molding treatment was 13.10 weeks and these patients were recalled at average 8.31 weeks after cheiloplasty. These patients' models were obtained at initial visit (T0, mean age : $37.0\pm27.89$ days after birth), after successful alveolar molding (T1, mean age : $119.25\pm40.18$ days after birth), and after cheilopasty (T2, mean age : $190.81\pm42.78$ days after birth). Seven linear and five angular variables were measured using 1 : 1 photometry and soft ware program(V-ceph. Cybermed. Seoul, Korea). Paired t-test was performed to investigate statistical significance at p<0.05 level. 1 The posterior parts of alveolar segments were the stable structures during alveolar molding treatment period and after cheiloplasty in infants. 2. The closure of cleft gap during alveolar molding was usually due to backward bending of the whole part of the greater segment. 3. Although forward growth of the greater segment was hindered by alveolar molding, it resumed after cheiloplasty. 4. Increase of anterior inter-segment angle after cheiloplasty was due to the molding effect of the lip scar pressure.