• Nuclear Engineering and Technology
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• 제54권7호
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• pp.2550-2563
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• 2022

This study performed a precise dynamic finite element time history elastic-plastic seismic analysis considering the welds, which have been not considered in design stage, on the nuclear components subjected to severe seismic loadings such as beyond-design basis earthquakes for sustainable nuclear power plants. First, the dynamic finite element elastic-plastic seismic analysis was performed for a general design practice that does not take into account the welds of the pressurizer surge line system, one of safety class I components in nuclear power plants, and then the reference values for the accumulated equivalent plastic strain, equivalent plastic strain, and von Mises effective stress were set. Second, the dynamic finite element elastic-plastic seismic analyses were performed for the case of considering only the mechanical strength over-mismatch of the welds as well as for the case of considering both the strength over-mismatch and welding residual strain. Third, the effects of the strength over-mismatch and welding residual strain were analyzed by comparing the finite element analysis results with the reference values. As a result of the comparison, it was found that not considering the strength over-mismatch may lead to conservative assessment results, whereas not considering the welding residual strain may be non-conservative.

• Physical Therapy Rehabilitation Science
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• 제12권3호
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• pp.355-364
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• 2023

Objective: The aim of this study is to test the effects of elastic band exercise accompanied by Swiss ball exercise on lower limb muscle strength, balance and pain in middle-aged women with osteoarthritis. Design: A randomized controlled trial. Methods: Thirty-five participants were randomly assigned to the experimental group (n=18), which performed elastic band exercise combined with Swiss ball exercise, and the control group (n=17), which performed elastic band exercise only. Both groups did a 30-minute session of exercise three times a week for eight weeks and were assessed for lower extremity muscle strength, static and dynamic balance, and pain levels before the first therapy session. All participating patients underwent outcome assessment after eight weeks of therapy without any additional treatment. Results: The experimental group made a significant increase in muscle strength of the lower extremities, static and dynamic balance ability, and pain level (p<0.05). The control group made a significant improvement in lower limb muscle strength, dynamic balance ability and pain level (p<0.05) with no such improvement in static balance ability. The exercise group made a significant increase in static and dynamic balance ability and pain level compared to the control group (p<0.05). Conclusions: These results demonstrated that both Swiss ball exercise and elastic band exercise were effective for middle-aged women with osteoarthritis and found that elastic band exercise combined with Swiss ball exercise produced more significant effects on their balance and pain.

• 한국지반신소재학회논문집
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• 제18권3호
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• pp.89-100
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• 2019

본 연구에서는 동재하시험을 통해 매입공법으로 선단이 암반에 근입된 초고강도 PHC 말뚝의 지지력 특성을 분석하였다. 초고강도 PHC 말뚝은 일반 고강도 PHC 말뚝에 비해 콘크리트의 강도가 높아 허용구조내력을 향상시킬 수 있었다. 초고강도 PHC 말뚝의 최적 설계를 위해서는 지반지지력도 증가된 구조내력과 균형을 맞출 수 있도록 증가되어야 할 것이다. 오늘날, 지반지지력 검증을 위한 동재하시험 시 경험적으로 고강도 PHC 말뚝과 유사한 항타에너지를 초고강도 PHC 말뚝에 적용하고 있는 실정이다. 동재하시험 결과를 기반으로 초고강도 PHC 말뚝의 지지력에 영향을 미치는 요소들을 분석한 결과, 선단지지력에 대해 선단 주변지반의 표준관입시험 N값의 영향은 미미하였으며, 항타에너지가 증가할수록 선단지지력이 증가하는 경향을 보였다. 그러나 주면마찰력의 경우, 항타에너지의 증가에 따른 변화가 나타나지 않았다. 또한, 허용지지력을 판단하는 Restrike 시험시 선단지지력의 영향은 극히 작아 허용지지력 판단시 합리적인 방안이 필요하다.

• 한국압력기기공학회 논문집
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• 제20권1호
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• pp.66-74
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• 2024

This study investigates the effects of temperatures and strain rates on the strength and ductility of Gr.91 (ASME Grade 91) steel which is widely being used as a heat-resistant material in Generation IV nuclear and super critical thermal power plants. The tensile behavior of modified 9Cr-1Mo (Gr.91) steel was studied for the three strain rates of 6.67×10^-5/s, 6.67×10^-4/s and 6.67×10-3/s over the temperature range from room temperature (RT) to 650℃. Experimental results showed that at specific combinations of temperatures (300~400℃) and strain rates, serrations appeared in the stress-strain curves. Concurrently, abnormal behaviors such as a plateau in yield strength and tensile strength, a minimum in ductility and negative strain rate sensitivity were observed. These phenomena were analyzed as significant characteristics of dynamic strain aging (DSA). Since this abnormal behavior in Gr.91 steel affects the material strength, it is judged that a correlation analysis between DSA and material strength should be crucial in the design and integrity evaluation of Gr. 91 steel pressure vessel and piping subjected to high-temperature loading.

• 대한의용생체공학회:의공학회지
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• 제34권4호
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• pp.212-217
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• 2013

Falling is one of the major public problems to the elderly, resulting in limitations of daily living activities. It can be induced by the functional loss of the balance ability and muscle strength in the elderly. It has been, however, not well investigated to suggest an effective methodology improving the balance ability and muscle strength for the prevention of the falling due to lack of information about the characteristics of the balance and muscle activations responded to the dynamic motions. The aim of the current study is, therefore, to identify the characteristics of the balance and muscle activations responded to the dynamic motions in Anterior-Posterior(AP) and Medial Lateral(ML) directions. For that, a motion capture system with eight infrared cameras, surface electromyogram system and Wii Fit system with a customized variable unstable base were used and kinematic and kinetic data obtained from the systems were analyzed for five healthy male($24.8{\pm}3.3years$, $177.4{\pm}2.0cm$, $73.9{\pm}12.9kg$, $23.5{\pm}4.0kg/m$). The results showed that the characteristics of the balance and muscle activations were differently responded to between the dynamic motions in Anterior-Posterior(AP) and Medial Lateral(ML) directions. These findings may indicate that customized dynamic motions should be applied to the training of the balance ability and muscle strength for the effective prevention of the falling. This study may be meaningful to providing basic information to establish a guideline improving effectively the balance ability and muscle strength.

• 대한기계학회논문집A
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• 제34권9호
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• pp.1175-1183
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• 2010

지지격자체는 경수로 핵연료집합체의 가장 중요한 핵심 구조부품 중에 하나이다. 질칼로이 지지격자체 설계시의 우선적으로 고려해야 할 사항은 지지격자체가 원자로심에서 냉각수의 심한 수두손실을 유발하지 않으면서 지진사고를 고려한 설계하중 하에서 충분한 횡방향 충격강도를 갖도록 하는 것이다. 본 연구에서는 시험과 유한요소해석을 통해 지지격자체의 횡방향 충격강도에 영향을 주는 인자들에 대한 분석을 수행하였고, 지지격자체 제조용 질칼로이 원자재 소요량을 획기적으로 줄이면서 지지격자체의 횡방향 충격강도를 개선할 수 있는 방안을 제시하였다.

• Physical Therapy Rehabilitation Science
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• 제10권4호
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• pp.479-486
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• 2021

Objective: The aim of this study was to investigate the effect of agility training with kinesio taping (ATKT) on muscle tone, muscle strength lower extremity and dynamic stability of women softball players. Design: Two groups pre-post randomized controlled design Methods: 34 softball players were recruited randomly assigned into the ATKT group and agility training with sham kinesio taping (control group). All subjects performed agility training for 30 min/day, 5 times/week for 4 weeks. The subjects in the ATKT group underwent agility trainingwith kinesio taping on vastus madialis, vastus medialis, rectus femoris, and vastus lateralis where the subects in the control group underwent agility trainingwith sham kinseio taping. Muscle tone was measured using myotonPRO. A Hand dynamometer was used to evaluate muscle strengthening of lower -extremity. Dynamic stability was measured using the side hop test. Results: Muscle tone of lower-extremity was significantly more increased in the ATKT group (mean change 0.39 ± 0.31) than in the control group (mean change 0.19 ± 0.31) (p<0.05). Muscle strength of lower-extremity was significantly more increased in the ATKT group than in the control group (p<0.05). Dynamic stability was significantly more increased in the ATKT group (mean change -1.39 ±0.45) than in the control group (mean change -0.60 ± 0.46) (p<0.05). Conclusions: We confirmed that the benefits that ATKT is effective for increasing in softball players and suggested that knee joint kinesio taping. Also, it was observed improvement of muscle tone, muscle strength and Dynamic stability.

• 한국응용과학기술학회지
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• 제37권6호
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• pp.1669-1677
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• 2020

이 연구의 목적은 14주 고유수용성 저항운동이 사회복지시설 이용 여성 노인의 근지구력, 동적 평형성 및 보행능력에 미치는 영향이었다. 이 연구에 참여한 대상자는 평균연령이 70세 전후의 30의 여성 노인을 운동집단 15명과 통제집단 15명으로 구성하였다. 대상자들은 운동프로그램 전과 후에 근지구력(30초 의자 앉았다 일어서기), 동적 평형성(3m 왕복 걷기)과 보행능력(10m 걷기, 400m 걷기)을 검사하였다. 운동집단은 주 3회 60분간 스위스 볼을 이용한 고유수용성 저항운동을 하였다. 연구 결과 하체 근지구력에서는 유의한 개선이 있었고, 동적 평형성을 평가하는 3m 왕복 걷기에서도 유의한 개선이 있었다. 보행능력인 10m 걷기와 400m 걷기에서도 유의한 개선이 있었다. 결론적으로 고유수용성 저항운동에 의한 동적평형성과 보행능력의 개선은 여성 노인의 낙상 관련 가능성을 감소시킬 것이다.

• 한국응용과학기술학회지
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• 제38권5호
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• pp.1345-1353
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• 2021

이 연구의 목적은 6주간의 엉덩관절 강화 훈련이 근력, 동적 자세 조절 및 하체 손상 준거에 미치는 영향을 보고자 하였다. 운동선수 20명을 운동군과 통제군으로 분류하여, 운동군은 주 3회, 60분, 6주간 엉덩관절 강화훈련을 하였다. 이 연구의 측정 변인은 유연성, 근력, 동적 자세 조절 및 하체 부상 준거로 하였다. 연구 결과 유연성에서 운동의 효과가 유의하지 않았으나 배근력에서는 유의하였다. 동적 자세조절 결과, 좌·우 후방 가쪽 및 안쪽에서 운동의 효과가 유의하였다. 또한 종합점수에서도 운동의 효과가 유의하였고, 좌·우 다리 간의 차이는 없었다. 결론적으로 엉덩관절 강화 운동은 근력과 동적 자세 조절 능력의 증가와 하체 손상의 우려는 감소시키는 것으로 나타났다.

• 대한물리의학회지
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• 제14권4호
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• pp.153-162
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• 2019

PURPOSE: This study compared ankle joint exercise and thigh exercise on the isometric strength of the lower limb and balance ability. METHODS: Twenty-seven subjects were divided into ankle joint exercise (AEG, n=9), tight exercise (TEG, n=9), and control group (CON, n=9). AEG and TEG performed ankle joint and tight exercises three times a week for four weeks. The following were measured before and four weeks after each exercise: isometric strength at knee flexion and extension of the lower limb; isometric strength at ankle plantar flexion and dorsiflexion of the lower limb; static balance of trace length and C90 area; and the dynamic forward, backward, leftward, and rightward balance for each region. RESULTS: The results showed that the isometric strength of plantar flexion (p<.05) was increased significantly in AEG compared to those in TEG and CON. The dynamic leftward (p<.05) and rightward balance (p<.05) were increased significantly in both AEG and TEG compared to that in CON. On the other hand, the static balance of the trace length and C90 area, isometric strength of ankle dorsiflexion, knee flexion and extension of the lower limb, and dynamic forward and backward balance did not show significant differences between the groups. CONCLUSION: Ankle joint exercise improves the isometric strength of plantar flexion compared to tight exercise.