• 제목/요약/키워드: eccentric

검색결과 893건 처리시간 0.025초

독립화 비율과 정량화 비율을 사용한 대각선 패턴의 어깨운동 간의 근활성도 비교 (Comparison of Muscle Activities between the Diagonal Pattern of Shoulder Exercises Using the %Normalization and %Isolation Method)

  • 이상열;박세연
    • PNF and Movement
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    • 제21권1호
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    • pp.87-94
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    • 2023
  • Purpose: The present study aims to investigate the effects of a diagonal exercise pattern on selective activation of the upper extremity muscles using both normalization and isolation methods. Methods: In total, 17 asymptomatic subjects participated in this study. During the two diagonal patterns of exercise (diagonals 1 and 2), muscular activities of the upper trapezius (UT), lower trapezius (LT), serratus anterior (SA), anterior deltoid (AD), and infraspinatus (IS) were measured. The collected data were analyzed in two ways, according to the dominance of muscle activities (%Isolation) and according to normalized activities (%MVIC). Results: There were significant differences in LT, SA, AD, and IS between %MVIC and %Isolation (p<0.05), and the diagonal 1 pattern of exercise showed significantly more LT activities compared with the diagonal 2 pattern (p<0.05). Further, except for LT, there were no significant differences in muscle activities between the diagonal 1 and 2 exercises. Conclusion: The present study suggests that a diagonal pattern of exercise is advantageous for strengthening shoulder muscles, but caution is needed when applying to patients requiring selective strengthening. Regarding both the concentric and eccentric phases of exercise, there was no significant difference in muscular activation, except in LT, between the two diagonal patterns of exercises.

Shear strength and shear behaviour of H-beam and cruciform-shaped steel sections for concrete-encased composite columns

  • Keng-Ta Lin;Cheng-Cheng Chen
    • Steel and Composite Structures
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    • 제47권3호
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    • pp.423-436
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    • 2023
  • In this research, we tested 10 simply supported concrete-encased composite columns under monotonic eccentric loads and investigated their shear behaviour. The specimens tested were two reinforced concrete specimens, three steel-reinforced concrete (SRC) specimens with an H-shaped steel section (also called a beam section), and five SRC specimens with a cruciform-shaped steel section (also called a column section). The experimental variables included the transverse steel shape's depth and the longitudinal steel flange's width. Experimental observations indicated the following. (1) The ultimate load-carrying capacity was controlled by web compression failure, defined as a situation where the concrete within the diagonal strut's upper end was crushed. (2) The composite effect was strong before the crushing of the concrete outside the steel shape. (3) We adjusted the softened strut-and-tie SRC (SST-SRC) model to yield more accurate strength predictions than those obtained using the strength superposition method. (4) The MSST-SRC model can more reasonably predict shear strength at an initial concrete softening load point. The rationality of the MSST-SRC model was inferred by experimentally observing shear behaviour, including concrete crushing and the point of sharp variation in the shear strain.

4차원 자기공명영상을 활용한 돼지 심장 ex-vivo 이첨판 모델 유동 가시화 및 유동 특성 분석 (4D flow MRI based flow visualization and quantification of bicuspid valvular flow using ex-vivo porcine model)

  • 권민성;박성호;허형규
    • 한국가시화정보학회지
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    • 제21권1호
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    • pp.12-17
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    • 2023
  • Aortic valve stenosis is a heart valve disease caused by the accumulation of calcium in the valve, which can divide into tricuspid aortic valve (TAV) stenosis and bicuspid aortic valve (BAV) stenosis depending on the shape of natural valve. In this study, pig heart-based TAV and BAV ex vivo models were fabricated, and the flow characteristics behind a valve were analyzed using 4D flow MRI. Flow behind normal TAV was uniformly distributed, while BAV asymmetrically opened with an eccentric strong jet. Especially, BAV ex vivo model exhibited a secondary flow in the region where the valve closed. In addition, BAV had a 26% higher peak velocity while maintaining similar stroke volume compared with normal TAV. This study would be helpful for understanding the flow characteristics for BAV AS patients.

Mechanics model of novel compound metal damper based on Bi-objective shape optimization

  • He, Haoxiang;Ding, Jiawei;Huang, Lei
    • Earthquakes and Structures
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    • 제23권4호
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    • pp.363-371
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    • 2022
  • Traditional metal dampers have disadvantages such as a higher yield point and inadequate adjustability. The experimental results show that the low yield point steel has superior energy dissipation hysteretic capacity and can be applied to seismic structures. To overcome these deficiencies, a novel compound metal damper comprising both low yield point steel plates and common steel plates is presented. The optimization objectives, including "maximum rigidity" and "full stress state", are proposed to obtain the optimal edge shape of a compound metal damper. The numerical results show that the optimized composite metal damper has the advantages such as full hysteresis curve, uniform stress distribution, more sufficient energy consumption, and it can adjust the yield strength of the damper according to the engineering requirements. In view of the mechanical characteristics of the compound metal damper, the equivalent model of eccentric cross bracing is established, and the approximate analytical solution of the yield strength and the yield displacement is proposed. A nonlinear simulation analysis is carried out for the overall aseismic capacity of three-layer-frame structures with a compound metal damper. It is verified that a compound metal damper has better energy dissipation capacity and superior seismic performance, especially for a damper with double-objective optimized shape.

Bearing capacity of strip footings on unsaturated soils under combined loading using LEM

  • Afsharpour, Siavash;Payan, Meghdad;Chenari, Reza Jamshidi;Ahmadi, Hadi;Fathipour, Hessam
    • Geomechanics and Engineering
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    • 제31권2호
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    • pp.223-235
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    • 2022
  • Bearing capacity of shallow foundations is often determined for either dry or saturated soils. In some occasions, foundations may be subjected to external loading which is inclined and/or eccentric. In this study, the ultimate bearing capacity of shallow foundations resting on partially saturated coarse-grained cohesionless and fine-grained cohesive soils subjected to a wide range of combined vertical (V) - horizontal (H) - moment (M) loadings is rigorously evaluated using the well-established limit equilibrium method. The unified effective stress approach as well as the suction stress concept is effectively adopted so as to simulate the behaviour of the underlying unsaturated soil medium. In order to obtain the bearing capacity, four equilibrium equations are solved by adopting Coulomb failure mechanism and Bishop effective stress concept and also considering a linear variation of the induced matric suction beneath the foundation. The general failure loci of the shallow foundations resting on unsaturated soils at different hydraulic conditions are presented in V - H - M spaces. The results indicate that the matric suction has a marked influence on the bearing capacity of shallow foundations. In addition, the effect of induced suction on the ultimate bearing capacity of obliquely-loaded foundations is more pronounced than that of the eccentrically-loaded footings.

The Immediate Effect of Static and Dynamic Stretching on Flexibility of Hamstring, Dynamic Balance Ability, Function of Lower Extremity: Randomized Controlled Trial

  • Ho Jin Shin;Eun-Ji Kim;Shin Young Kim
    • The Journal of Korean Physical Therapy
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    • 제35권5호
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    • pp.125-131
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    • 2023
  • Purpose: This study examined the acute effects of static and dynamic stretching on the flexibility of the hamstring, dynamic balance ability, and function of the lower extremities in healthy adults. Methods: Thirty participants were assigned randomly to three groups: static stretching group (SSG), basic dynamic stretching group (BDSG), and 5 sec dynamic stretching group (5DSG). SSG performed three sets of 30 seconds of static stretching. BDSG performed a single-leg deadlift (SLD) at the same time as SSG, and 5DSG performed SLD held for five seconds. Hamstring flexibility, dynamic balance ability, and lower extremity function were evaluated before and after intervention. Results: The hamstring flexibility significantly improved in all groups (p<0.05). The dynamic balance ability improved significantly after intervention in all groups except BDSG in the anterior direction (p<0.05). There were significant differences in the posterolateral and posteromedial direction in all groups. The function of the lower extremity showed significant improvement over time only in BDSG (p<0.05). Conclusion: This study suggested that basic dynamic stretching and 5 sec dynamic stretching positively affect the hamstring flexibility, dynamic balance ability, and lower extremity function. Therefore, it is recommended to include dynamic stretching in a program for improving the hamstring flexibility, dynamic balance ability, and the lower extremity function. In addition, it is recommended to apply it at different times depending on the purpose.

Seismic response control of irregular asymmetric structure with voided slabs by distributed tuned rotary mass damper devices

  • Shujin Li;Irakoze Jean Paula;Ling Mao
    • Earthquakes and Structures
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    • 제25권6호
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    • pp.455-467
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    • 2023
  • This study focuses on demonstrating the effectiveness of vibration control of tuned rotary mass damper (TRMD) for reducing the bidirectional and torsional response of the irregular asymmetric structure with voided slabs under earthquake excitations. The TRMD arranged in plane of one-story eccentric structure is proposed as a distributed tuned rotary mass damper (DTRMD) system. Lagrange's equation is used to derive the equations of motion of the controlled system. The optimum position and number of TRMD are numerically investigated under harmonic excitation and the control effects of different distributions are discussed. Furthermore, a shaking table test is conducted under different excitation cases, including free vibration, forced vibration and seismic wave to investigate the absorption performance of the device. The numerical simulations of different distributions of the TRMDs show that the DTRMDs are more effective in reduction of the displacement response of the asymmetric structure under the same mass ratio, even when the degree of eccentricity becomes large. However, with small degree of eccentricity, the unreasonable asymmetrical arrangement may cause the increase of the peak value of the rotational angular displacement. Finally, the experimental investigations exhibit similar results of translational displacement of the structure. It is concluded that the vibration of the irregular asymmetric structure can be controlled more economically and effectively by reducing the mass ratio through reducing the quantity of TRMDs at the high stiffness end.

유전자 알고리즘을 이용한 비대칭 강성 구조물의 내진보강 최적설계 (Optimal design of seismic reinforcement for structures with asymmetric rigidity plans using genetic algorithm)

  • 이준호;김유성;성은희
    • 한국공간구조학회논문집
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    • 제24권2호
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    • pp.65-73
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    • 2024
  • In this study, we propose an optimal design method by applying the Prefabricated Buckling Restrained Brace (PF-BRB) to structures with asymmetrically rigidity plan. As a result of the PF-BRB optimal design of a structure with an asymmetrically rigidity plan, it can be seen that the reduction effect of dynamic response is greater in the case of arrangement considering the asymmetric distribution of stiffness (Asym) than in the case of arrangement in the form of a symmetric distribution (Sym), especially It was confirmed that at an eccentricity rate of 20%, the total amount of reinforced PF-BRBs was also small. As a result of analyzing the dynamic response characteristics according to the change in eccentricity of the asymmetrically rigidity plan, the distribution of the reinforced PF-BRB showed that the larger the eccentricity, the greater the amount of damper distribution around the eccentric position. Additionally, when comparing the analysis models with an eccentricity rate of 20% and an eccentricity rate of 12%, the response reduction ratio of the 20% eccentricity rate was found to be large.

Evaluation of cyclic behavior of lateral load resisting system with eccentric brace and steel plate

  • Reza Khalili Sarbangoli;Ahmad Maleki;Ramin K. Badri
    • Structural Engineering and Mechanics
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    • 제89권3호
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    • pp.239-252
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    • 2024
  • Steel plate shear walls (SPSWs) are classified as lateral load-resisting systems. The feasibility of openings in the steel plate is a characteristic of SPSWs. The use of openings in SPSWs can lower the load capacity, stiffness, and energy dissipation. This study proposes a novel form of SPSWs that provides convenient access through openings by combining steel plates and eccentrically braced frames (EBFs). The proposed system also avoids a substantial reduction in the strength and stiffness. Hence, various geometric forms were analyzed through two different structural approaches. Groups 1, 2, and 3 included a steel EBF with a steel plate between the column and EBF in order to improve system performance. In Group 4, the proposed system was evaluated within an SPSW with openings and an EBF on the opening edge. To evaluate the performance of the proposed systems, the nonlinear finite element method (NL-FEM) was employed under cyclic loading. The hysteresis (load-drift) curve, stress contour, stiffness, and damping were evaluated as the structural outputs. The numerical models indicated that local buckling within the middle plate-EBF connection prevented a diagonal tension field. Moreover, in group 4, the EBF and stiffeners on the opening edge enhanced the structural response by approximately 7.5% in comparison with the base SPSW system.

Effects of Resistance Exercise with Pressure Biofeedback Unit on the Gait Ability and Knee Joint Function in Subject with Total Knee Replacement Patients

  • Jin Park
    • The Journal of Korean Physical Therapy
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    • 제36권1호
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    • pp.27-32
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    • 2024
  • Purpose: This study was conducted to verify the effect of applying a pressure biofeedback unit on walking ability and knee joint function while performing knee joint extensor strengthening exercises using resistance exercise equipment in total knee replacement (TKR) patients. Methods: This study was conducted on twelve patients receiving rehabilitation treatment after being admitted to a rehabilitation hospital post-TKR. Of these, six were allocated to a feedback group with a pressure biofeedback unit, and the other 6 were allocated to a control group without a pressure biofeedback unit. The subjects performed an exercise program for 45 minutes per session, five times a week, for two weeks. Walking ability and knee joint function were evaluated and analyzed before and after exercise. Results: The feedback group showed significantly better improvements in walking speed, gait cycle, step length on the non-operation side, time on the foot on the operation side, K-WOMAC stiffness, and K-WOMAC function than the control group (p<0.05). Conclusion: When strengthening the knee joint extensor muscles using resistance exercise equipment in TKR patients, the provision of a pressure biofeedback unit was found to improve walking ability and knee joint function by inducing concentric-eccentric contraction of the knee joint extensor muscles. Therefore, the study shows that exercise based on the provision of a pressure biofeedback unit should be considered when strengthening knee joint extensor muscles to improve the walking ability and knee joint function of TKR patients in clinical practice.