• Journal of the Korean Society for Precision Engineering
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• v.19 no.10
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• pp.37-44
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• 2002

The dynamic behavior of rotor-bearing system has been investigated using finite element method. A procedure is presented for dynamic modeling of rotor-bearing system which consists of shaft elements, rigid disk, flexible bearing and support structure. A finite element model including the effects of rotary inertia, shear deformation, gyroscopic moments is developed. Linear stiffness and damping coefficients are calculated for 2 lobe sleeve bearing. The whirl frequency, mode shape, stability and unbalance response of rotor system including effects of bearing coefficient and support structures are calculated.

• The Journal of Korean Physical Therapy
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• v.31 no.6
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• pp.346-350
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• 2019

Purpose: The purpose of this study was to investigate the effects of calf tightness on gait, plantar pressure, and balance in adults. Methods: A total of 60 participants were divided into a normal group of 30 subjects with normal dorsiflexion angle (20-25 degrees) and an experimental group of 30 subjects with limited dorsiflexion angle (0-15 degrees) due to calf tightness. Gait ability and foot pressure of the subjects was measured with a treadmill, and the balance ability was measured by PROKIN system. Results: A significant difference in COP length, loading response, and single limb support was observed between groups. The COP length and single limb support ratio in the normal group was greater than in the experimental group, but the experimental group showed a higher ratio for loading response in the gait ratio. Conclusion: Our results indicated that calf tightness was negative effects on balance and gait ability, so assessment of the muscle tightness should be considered during exercise and treatment.

• Proceedings of the KSR Conference
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• 2002.05a
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• pp.256-263
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• 2002

This paper deal with optimal design of reinforced track as a track reinforcing method for transition area of track support stiffness in transition area between bridge and earthwork. When vehicle passes through transition area, dynamic properties between vehicle and track are studied by the analysis of vehicle-train interaction for the each case when reinforced tracks are used or not. furthermore, optimum decision of type and length of track are made based on the performance adapting variable parameters : support stiffness of track for bridge and earthwork, heading direction of vehicle and type and length of track.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.58-63
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• 1997

The natural frequencies of the support system for a vertical pump, which are a key factor affecting the dynamic stability of the pump support system, are not easily predictable with analytical approaches only, due to the difficulties estimating the effective stiffness of the connections between the concrete base, the motor structure, the discharge elbow and the suction column of the pump system. This paper presents the results of a finite element analysis and an experimental study performed to identify and modify the characteristics of the pumping structure. The difficulties of modelling the effective stiffness were overcome by utilizing experimental results in the analysis. Based on analytical and experimental results, appropriate structural modifications are taken to reduce excessive vibration of the pump system to a satisfactory level.

• Journal of Auto-vehicle Safety Association
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• v.11 no.1
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• pp.40-47
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• 2019

First, three point bending analysis for the inclined press door impact beam was carried out to investigate inclination angle effect on the maximum strength with varying support distance. Next, for the system model with spring elements representing body stiffness at door mounting area, the bending structural behavior of impact beam mounted on vehicle was estimated. The mounting distance and inclination angle were changed and the beam bending buckling strength was presumed at the head displacement below which spring stiffness change has little effect on the load. Finally strength ratio to predict the bending buckling strength of impact beam mounted on vehicle from three point bending maximum strength of fixed support distance was suggested.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.631-637
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• 2005

This paper presents a stiffness analysis method for a low-DOF parallel manipulator, which takes into account of elastic deformations of joints and links. A low-DOF parallel manipulator is defined as a spatial parallel manipulator which has less than six degrees of freedom. Differently from the case of a 6-DOF parallel manipulator, the serial chains in a low-DOF parallel manipulator are subject to constraint forces as well as actuation forces. The reaction forces due to actuations and constraints in each limb can be determined by making use of the theory of reciprocal screws. It is shown that the stiffness model of an F-DOF parallel manipulator consists of F springs related to the reciprocal screws of actuations and 6-F springs related to the reciprocal screws of constraints, which connect the moving platform to the fixed base in parallel. The $6{times}6$ stiffness matrix is derived, which is the sum of the stiffness matrices of actuations and constraints. The six spring constants can be precisely determined by modeling the compliance of joints and links in a serial chain as follows; the link can be considered as an Euler beam and the stiffness matrix of rotational or prismatic joint can be modeled as a $6{times}6$ diagonal matrix, where one diagonal element about the rotation axis or along the sliding direction is zero. By summing the elastic deformations in joints and links, the compliance matrix of a serial chain is obtained. Finally, applying the reciprocal screws to the compliance matrix of a serial chain, the compliance values of springs can be determined. As an example of explaining the procedure, the stiffness of the Tricept parallel manipulator has been analyzed.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.8
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• pp.137-145
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• 1997

A two-dimensional program for the analysis of bimaterial inclusion has been developed using the bound- ary element method. In order to study the effects of circular inclusion on the stress field of the crack tip, numerical analysis was performed for the straight crack of finite length around the symmetric circular inclusion whose modulus of elasticity was different from that of the matrix material. In the case of inclusion whose stiffness was smaller than that of the matrix material, the stress intensity factor was found to increase as the crack enamated. The stress intensity factor was uninfluenced from the radial change in inclusion and remained constant for the stiffness equivalent to the matrix materials, where as it decreased for the inclusion with larger stiffness. For the vareation in the distance of the inclusion, a small increase in the stress intensity factor was observed for the case with small or equal stiffness compared with the matrix materials. The inclusion with larger stiffness showed a gradual decrease in the strss intensity factor as the crack emanated.

• The Korean Journal of Emergency Medical Services
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• v.24 no.3
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• pp.79-87
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• 2020

Purpose: This study sought to determine how the act of performing cardiopulmonary resuscitation (CPR) affects the rescuer's muscle tone, stiffness, and fatigue in the lumbar region. Methods: The research subjects were 30 healthy men in their twenties in possession of a Basic Life Support (BLS) provider certificate. In this study, the CPR rescuer's muscle tone and stiffness in the upper and lower lumbar regions were measured in the resting position, starting position, and position after 10 min. Their level of fatigue was measured before and after performing CPR. Results: Muscle tone and stiffness in the upper and lower lumbar regions of the research subjects significantly increased throughout the CPR process and lasted up to 10 min after the process (p<.001). The subjects' fatigue also significantly increased post-CPR (p<.001). Conclusion: This study suggests that performing CPR creates muscular and physiological stress, fatigue, and ultimately, lower back pain.

• Journal of the Korean Society of Safety
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• v.32 no.3
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• pp.60-65
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• 2017

This study examined the effect of rotational stiffness of joints between vertical and horizontal members in system supports. In order to prevent repeated disasters of system supports, it is important to examine the accurate behavior of system supports. Among various factors affecting the complex behavior of system supports, this study focused on the stiffness of joints between vertical and horizontal members. The considered joint was modelled by a rotational spring, but the translational displacements were fixed. The stiffness of rotational spring was calculated by utilizing the usable experimental data. In addition, the hinge connection condition, which is generally considered in design and only restrict the translational displacements, was modelled to compare the results. The case with the rotational stiffness in joints showed 3.5 times buckling loads compared to the case without the rotational stiffness. Thus, the structural behavior of the vertical member in system supports was similar to the vertical member with the fixed condition. For the combined stresses of vertical members, the combined stress ratios were reduced 5~6% by considering the rotational stiffness of connecting parts. However, for the horizontal member where showed relatively small stress range, the stresses were increased 2.3~7.6 times by considering the rotational stiffness in connecting parts.

• The Journal of the Convergence on Culture Technology
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• v.6 no.3
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• pp.347-352
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• 2020

In this study, the variation of track impact factor according to the spring stiffness change rate of sleeper resilience pad was analyzed based on field measurements. In addition, the correlation between field measurement results and 7 million fatigue test results was verified. The fatigue effect diagram of the sleeper resilience pads was presented considering the nonlinear deterioration characteristics of the sleeper resilience pads used for the STEDEF track. Based on the field measurement results, the nonlinear characteristics of the track impact factor for the spring stiffness change rate over 30% of sleeper resilience pad on the track impact factor-track support stiffness diagram were analyzed to be consistent with the fatigue test results.