• The Journal of the Acoustical Society of Korea
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• 제17권2E호
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• pp.53-58
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• 1998

In this paper, we study the response of several anisotropic systems to buried transient line loads. The problem is mathematically formulated based on the equations of motion in the constitutive relations. The load is in form of a normal stress acting with arbitrary axis on the plane of monoclinic symmetry. Plane wave equation is coupled with vertical shear wave, longitudinal wave and horizontal shear wave. We first considered the equation of motion in reference coordinate system, where the line load is coincident with symmetry axis of the orthotrioic material. Then the equation of motion is transformed with respect to general coordiante system with azimuthal angle by using transformation tensor. The load is first described as a body force in the equations of the motion for the infinite media and then it is mathematically characterized. Subsequently the results for semi-infinite spaces is also obtained by using superposition of the infinite medium solution together with a scattered solution from the free surface. Consequently explicit solutions for the displacements are obtained by using Cargniard-DeHoop contour. Numerical results which are drawn from concrete examples of orthotropic material belonging to monoclinic symmetry are demonstrated.

• Wind and Structures
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• 제19권5호
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• pp.481-503
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• 2014

A new theoretical model on rain-wind induced vibration (RWIV) of a continuous stay cable is developed in this paper. Different from the existing theoretical analyses in which the cable was modeled as a segmental rigid element, the proposed scheme focuses on the in-plane and out-of-plane responses of a continuous stay cable, which is identical with the prototype cable on cable-stayed bridge. In order to simplify the complexities, the motion law of the rivulet on the cable surface is assumed as a sinusoidal way according to some results obtained from wind tunnel tests. Quasi-steady theory is utilized to determine the aerodynamic forces on the cable. Equations of motion of the cable are derived in a Cartesian Coordinate System and solved by using finite difference method to obtain the in-plane and out-of-plane responses of the cable. The results show that limited cable amplitudes are achieved within a limited range of wind velocity, which is a unique characteristic of RWIV of stay cable. It appears that the in-plane cable amplitude is much larger than the out-of-plane cable amplitude. Rivulet frequency, rivulet distribution along cable axis, and mean wind velocity profile, all have significant effects on the RWIV responses of the prototype stay cable. The effects of damping ratio on RWIVs of stay cables are carefully investigated, which suggests that damping ratio of 1% is needed to well mitigate RWIVs of prototype stay cables.

• 대한기계학회논문집A
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• 제27권8호
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• pp.1331-1337
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• 2003

Linearized equations of motion for the vibration analysis of rotating cantilever plates with arbitrary orientation angle are derived in the present work. Two in-plane stretch variables are introduced to be approximated. The use of the two in-plane stretch variables enables one to derive the equations of motion which include proper motion-induced stiffness variation terms. The equations of motion are transformed into dimensionless forms in which dimensionless parameters are identified. The effects of the dimensionless parameters on the modal characteristics of rotating cantilever plates are investigated through numerical study. The natural frequency loci veering along with the associated mode shape variations, which occur while the rotating speed increases, are also presented and discussed.

• Clinics in Orthopedic Surgery
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• 제10권4호
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• pp.468-478
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• 2018

Background: The restriction of wrist motion results in limited hand function, and the evaluation of the range of wrist motion is related to the evaluation of wrist function. To analyze and compare the wrist motion during four selected tasks, we developed a new desktop motion analysis system using the motion controller for a home video game console. Methods: Eighteen healthy, right-handed subjects performed 15 trials of selective tasks (dart throwing, hammering, circumduction, and winding thread on a reel) with both wrists. The signals of light-emitting diode markers attached to the hand and forearm were detected by the optic receptor in the motion controller. We compared the results between both wrists and between motions with similar motion paths. Results: The parameters (range of motion, offset, coupling, and orientations of the oblique plane) for wrist motion were not significantly different between both wrists, except for radioulnar deviation for hammering and the orientation for thread winding. In each wrist, the ranges for hammering were larger than those for dart throwing. The offsets and the orientations of the oblique plane were not significantly different between circumduction and thread winding. Conclusions: The results for the parameters of dart throwing, hammering, and circumduction of our motion analysis system using the motion controller were considerably similar to those of the previous studies with three-dimensional reconstruction with computed tomography, electrogoniometer, and motion capture system. Therefore, our system may be a cost-effective and simple method for wrist motion analysis.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.597-600
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• 2004

A two-degree-of-freedom out-of-plane model with contact stiffness is presented to describe dynamical interaction between the pad and disc of a disc brake system. It is assumed that the out-of-plane motion of the system depends on the friction force acting along the in-plane direction. Dynamic friction coefficient is modelled as a function of both in-plane relative velocity and out-of-plane normal force. When the friction coefficient depends only on the relative velocity, the contact stiffness has the role of negative stiffness. The results of stability analysis show that the stiffness of both pad and disc are equally important. Complex eigenvalue analysis is conducted for the case that the friction coefficient is also dependent on the normal force. The results further verify the importance of the stiffness. It has also been found that increasing the gradient of friction coefficient with respect to the normal force makes the system more unstable. Nonlinear analysis is also performed to demonstrate various responses. Comparing the responses with experimental data has shown that the proposed model may qualitatively well represent a certain type of brake noise.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.659-661
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• 1997

An in-plane motion measurement method using $moir{\acute{e}}$ patterns by linear-gratings and cross-gratings, which can be used as micro inertial sensors, micro actuators, and micromachined scanning microscopes is demonstrated. A simple digital image processing method that calculates and analyzes the motion of microstructure from $moir{\acute{e}}$ patterns was developed. And using several grating structures fabricated by surface micromachining, we formed $moir{\acute{e}}$ patterns and analyzed the motion of microstructure.

• 한국공작기계학회논문집
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• 제13권5호
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• pp.1-6
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• 2004

Measurements of circular motion accuracy of NC lathe have achieved with ball bar systems proposed by Bryan, but the ball bar systems have ifluenced on the measuring data by way of the accuracy of the balls and the contacts of balls and bar seats. Therefore in this study, error data during of circular motion of ATC(Automatic Tool Changer) of NC lathe will be acquired by reading zx plane coordinates using two optical linear scales. Two optical linear scales of measuring unit are fixed on z-x plane of NC lathe, and the moving part is fixed to ATC and then is made to receive data of coordinates of the ATC at constant time intervals using tick pulses comming out from computer. And then, error data files of radial direction of circular motion are calculated with the data read, and the aspect of circular motion are modeled to plots, and are analysed by means of statistical treatments of circularity, means, standard deviations etc.

• 한국운동역학회지
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• 제20권2호
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• pp.197-204
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• 2010

Scapular position and motion are essential for normal upper limb mobility; Further, the posture of patients with thoracic kyphosis is related to shoulder girdle function and disorder. The purpose of this study was to examine the effects of thoracic posture on the shoulder range of motion and on three-dimensional scapular kinematics. Thirty healthy subjects performed right-arm abduction along the frontal plane while standing in both erect and in slouched trunk posture. The scapular position and rotation, and shoulder and thoracic angles were recorded using a motion analysis system. The scapular upward rotation and internal rotation were significantly altered according to postural tatiges; however, scapular tilt was not affected. Shoulder angle was significantly decreased in the slouched posture as c rpared to tatt in the erect posture. Thus, a slouched posture(thoracic kyphosis) significantly affects the shoulder range of motion and scapular kinematics during shoulder abduction in the frontal plane.

• The Journal of Korean Physical Therapy
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• 제31권6호
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• pp.333-338
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• 2019

Purpose: Although previous studies on the screw-home movement (SHM) for autopsy specimen and walking of living persons conducted, the possibility of acquiring SHM based on inertial measurement units received little attention. This study aimed to investigate the possibility of measuring SHM for the non-weighted bearing using a micro-electro-mechanical system-based wearable motion capture system (MEMSS). Methods: MEMSS and camera-based motion analysis systems were used to obtain kinematic data of the knee joint. The knee joint moved from the flexion position to a fully extended position and then back to the start point. The coefficient of multiple correlation and the difference in the range of motion were used to assess the waveform similarity in the movement measured by two measurement systems. Results: The waveform similarity in the sagittal plane was excellent and the in the transverse plane was good. Significant differences were found in the sagittal plane between the two systems (p<0.05). However, there was no significant difference in the transverse plane between the two systems (p>0.05). Conclusion: The SHM during the passive motion without muscle contraction in the non-weighted bearing appeared in the entire range. We thought that the MEMSS could be easily applied to the acquisition of biomechanical data on the knee related to physical therapy.

• 대한기계학회논문집A
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• 제26권5호
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• pp.952-959
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• 2002

The natural frequencies of a flexible spinning disk misaligned with the axis of rotation are studied in an analytic manner. The effects of misalignment on the natural frequency need to be investigated, because the misalignment between the axis of symmetry and the axis of relation cannot be avoided in the removable disks such as CD-R, CD-RW or DVD disks. Assuming that the in -plane displacements are in steady state and the out-of-plane displacement is in dynamic state, the equations of motion are derived for the misaligned spinning disk. After the exact solutions are obtained fur the steady -state in-plane displacements, they are plugged into the equation for the dynamic-state out-of-plane motion. The resultant equation is a linear equation for the out -of-plane displacement, which is discretized by the Galerkin method. Based on the discretized dquations, the effects of the misalignment are analyzed on the vibration characteristics of the spinning disk, i.e., the natural frequencies and the critical speed.