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이경봉,Jong Geun Kim,Han Gi Park,Ji Eun Kim,Hye Sun Kim,이완희 물리치료재활과학회 2015 Physical therapy rehabilitation science Vol.4 No.1
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.
윤한기,박원조,이경봉 東義大學校産業技術開發硏究所 1991 産業技術硏究誌 Vol.5 No.-
Low-cycle fatigue behavior of AISI 4340 steel which was carried out under full reversed strain control fatigue system, and was investigated by the Mason-Coffin equation and the ASTM test methods. And cyclic hardening exponent was calculated from the relationship of the plastic strain and stress range in stable cycles. The modified cyclic hardening exponent calculated by the Hysteresisloop in stable load cycles was compared with cyclic hardening exponent, and predicted the fatigue failure cycles. And so, a possibility was examined about substitution the modified cyclic hardening exponent for the established cyclic hardening exponent for the established cyclic hardening exponent on the ASTM test method.
풍력발전시스템의 안정성을 갖는 블레이드에 대한 공력해석
유재환,이경봉 世明大學校 1996 世明論叢 Vol.5 No.-
Wind energy generation technology, compared to other alternative energy technologies, provides simple, inexpensive, efficient and easy-maintenance powder generation system. Owing to the development of the basic technologies, commericalization of wind turbine system and the development of mass production of system, the world is in the stage of the development of structural stability of wind energy generation system. In this study, calculation of system profile and operating condition, which was preliminary for concept design, reviewed the size and airfoil of system blade by practicizing simulation variable according to design condition.
이경봉 물리치료재활과학회 2021 Physical therapy rehabilitation science Vol.10 No.4
Objective: The interest of clinicians is increasing due to the newly established medical insurance for pulmonary rehabilitation. Improvement of respiratory muscle strength and pulmonary function is an important factor in pulmonary rehabilitation, and this study aims to investigate the correlation between changes in respiratory muscle contraction thickness that can affect respiratory muscle strength and pulmonary function. Design: Cross-sectional observational study. Methods: Thirty-one subjects (male=13, female=18) participated in this study. The respiratory muscle strength was measured by dividing it into inspiratory/forced expiratory muscles, and the pulmonary function was measured by forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), and FEV1/FVC. To evaluate the respiratory muscle length increase, in resting and concentric contraction thickness of diaphragm, external/internal oblique, transverse abdominis, and rectus abdominis were measured by using ultrasonography. Results: Inspiratory muscle strength showed a significant correlation with the length increase of the inspiratory muscle (r=0.368 ∼0.521, p<0.05), and forced expiratory muscle strength showed a significant correlation with length increase of forced expiratory muscle (r=0.356∼0.455, p<0.05). However, pulmonary function was not correlated with the length increase of the respiratory muscle. Conclusions: In this study, a correlation between respiratory muscle strength and respiratory muscle length increase was confirmed, but no correlation with the pulmonary function was found. It is considered that the respiratory muscle strength can be improved by increasing the respiratory muscle thickness through appropriate respiratory muscle training.
저-사이클피로에서 히스테리시스 곡선에 의한 수명예측의 실험적 연구
이경봉,유재환,윤한기 東義大學校産業技術開發硏究所 1989 産業技術硏究誌 Vol.3 No.-
The MEF dual phase steel was made of the heat treatment of the SS41 steel, which are uniform in the volume fraction and are varied with three kinds in the ferrite grain size. The materials are fatigue tested under the control of constant total strain of fully reversed tensile and compression in the low-cycle fatigue region. The cyclic hardening and softening procedure of the two steel is compared with when the tow steels experience the cyclic strain. In this study, the characteristics of the MEF dual phase steel is investigated with the exponent and constant calculated from substituting the plastic strain and the failure life in Manson-Coffin equation ; the cyclic hardening exponent is calculated from the relation hysteresis by the experiment is the modified cyclic hardening exponent is calculated from the relation equation of the plastic strain and the stress range in stable state and computed from the hysteresis by the experiment is the modified cyclic hardening exponent corresponding to the cyclic hardening exponent is examined and the extimation of the low-cycle fatigue life time is execuated from substituting the modified cyclic hardening exponent in the established equation.
打擊速度 및 溫度變化가 豫크랙을 가진 衝擊試驗片의 動的破壞靭性에 미치는 影響
兪在煥,李敬奉,金重吉,李致雨,吳世旭 慶南大學校 附設 工業技術硏究所 1989 硏究論文集 Vol.7 No.-
計裝化衝擊試驗에서 打擊速度와 溫度의 變化가 豫크랙을 揷入한 衝擊試驗片의 動的破壞靭性에 미치는 影響을 考察한 結果 다음을 알 수 있었다. 豫크랙을 揷入한 試驗片이 V-노치 試驗片에 比하여 實驗値의 分散度가 적으며 0℃以下의 溫度領域에서 動的破壞靭性의 有效性이 있었다. 또한 打擊速度와 實驗溫度의 影響은 溫度가 速度보다 훨씬 上廻하는 傾向이었다. The effect of various impact velocity and temperature on dynamic fracture toughness is tested with precracked Charpy specimen, and conclude following results. Precracked specimen has less dispersion of test results than V-notched specimen, unstable crack initiation load didn't agreed to maximum load at room temperature but at 0℃ below, thus, the availability of dynamic fracture toughness is relatively high. Comparing V-notched specimen, the precracked Charpy specimen represented lower shelf of temperature different. But, at this time, the absorbed energy is estimated equivalently. With the decrease of temperature, the reduction of fracture toughness was obvious, but the effect of impact velocity didn't appear.
조정미,이경봉 대한기계학회 1994 大韓機械學會誌 Vol.34 No.5
본 연구를 통하여 기존에 사용되고 있던 알루미늄 압출재 블레이드를 복합재료로 대치하여 개 발함으로써 이의 타당성을 검토하여 보았다. 풍력발전기의 개발 추세는 점차 메가와트 (megawatt)급 시스템으로 진행되어 터빈 블레이드가 대형화됨에 따른 터빈브레이드의 경량화 및 내구력의 향상이 절실히 요구된다. 이는 복합소재의 사용으로 경량화를 통한 시스템 각요소의 제작비용절감 및 내구력 향상을 통한 시스템의 수명증대의 효과를 확보할 수 있을 것이다. 그 러나 복합재료를 사용한 터빈 블레이드는 기존의 알루미늄을 이용한 재료보다는 가격경쟁에서 다소 떨어지며 제작공정상의 어려움과 정밀한 설계기술의 미개발 등 아직도 많은 난점을 안고 있는 실정이다. 그러나 현재 풍력에너지 이용 선직국의 개발추이로 보아 대용량시스템의 터빈 블레이드는 복합소재의 사용이 필수적이며 보다 효율적인 양산시스템의 구축과 최적설계에 대한 연구가 지속적으로 실시되면 기존의 블레이드와는 충분한 경쟁성을 확보할 것으로 전망된다.