• Steel and Composite Structures
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• v.46 no.3
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• pp.367-383
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• 2023

In this investigation, an improved integral trigonometric shear deformation theory is employed to examine the vibrational behavior of the functionally graded (FG) sandwich plates resting on visco-Pasternak foundations. The studied structure is modelled with only four unknowns' variables displacements functions. The simplicity of the developed model being in the reduced number of variables which was made with the help of the use of the indeterminate integral in the formulation. The current kinematic takes into consideration the shear deformation effect and does not require any shear correction factors as used in the first shear deformation theory. The equations of motion are determined from Hamilton's principle with including the effect of the reaction of the visco-Pasternak's foundation. A Galerkin technique is proposed to solve the differentials governing equations, which enables one to obtain the semi-analytical solutions of natural frequencies for various clamped and simply supported FG sandwich plates resting on visco-Pasternak foundations. The validity of proposed model is checked with others solutions found in the literature. Parametric studies are performed to illustrate the impact of various parameters as plate dimension, layer thickness ratio, inhomogeneity index, damping coefficient, vibrational mode and elastic foundation on the vibrational behavior of the FG sandwich plates.

• Geomechanics and Engineering
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• v.31 no.1
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• pp.99-112
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• 2022

The present study examines the natural frequencies (NFs) of perfect/imperfect functionally graded sandwich beams (P/IP-FGSBs), which are composed of a porous core constructed of functionally graded materials (FGMs) and a homogenous isotropic metal and ceramic face sheets resting on elastic foundations. To accomplish this, the material properties of the FGSBs are assumed to vary continuously along the thickness direction as a function of the volume fraction of constituents expressed by the modified rule of the mixture, which includes porosity volume fraction represented using four distinct types of porosity distribution models. Additionally, to characterize the reaction of the two-parameter elastic foundation to the Perfect/Imperfect (P/IP) FGSBs, the medium is assumed to be linear, homogeneous, and isotropic, and it is described using the Winkler-Pasternak model. Furthermore, the kinematic relationship of the P/IP-FGSBs resting on the Winkler-Pasternak elastic foundations (WPEFs) is described using trigonometric shear deformation theory (TrSDT), and the equations of motion are constructed using Hamilton's principle. A closed-form solution is developed for the free vibration analysis of P/IP-FGSBs resting on the WPEFs under four distinct boundary conditions (BCs). To validate the new formulation, extensive comparisons with existing data are made. A detailed investigation is carried out for the effects of the foundation coefficients, mode numbers (MNs), porosity volume fraction, power-law index, span to depth ratio, porosity distribution patterns (PDPs), skin core skin thickness ratios (SCSTR), and BCs on the values of the NFs of the P/IP-FGSBs.

• The Journal of the Convergence on Culture Technology
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• v.10 no.1
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• pp.465-470
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• 2024

Kitchen cabinets are widely used for their spacious storage and efficient use of space, but their high installed location makes it difficult for the elderly and disabled to access. Therefore, in this paper, we propose a new height-adjustable kitchen cabinet that can be used more easily and safely. The lift-down range of cabinet was set considering the installation location of cabinet for efficient use of kitchen space and the maximum height accessible to the elderly and disabled, and the link geometry and driving method of the complex link mechanism were determined through the mechanism design procedure to ensure that the selected floor come down safely along the optimal descend path. In addition, the appropriate motor and control algorithm were added to allow the user to descend to the desired height with a simple button operation. It was confirmed through actual production that the proposed linkage mechanism performs the desired lift-down motion.

• Physical Therapy Korea
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• v.20 no.1
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• pp.64-73
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• 2013

The purposes of this study were to develop a new orthosis controlling ankle and knee joint motion during the gait cycle and to identify the effects of the newly designed orthosis on gait kinematics and tempospatial parameters, including coordination of the extremities in stroke patients. Fifteen individuals who had sustained a stroke, onset was 16 months, participated in this study. Before application of the measurement equipment the subjects were accustomed to walking on the ankle-foot orthosis (AFO) or stance control knee with knee flexion assisted-oil damper ankle-foot orthosis (SCKAFO) for 5 minutes. Fifteen patients were investigated for 45 days with a 3-day interval between sessions. Measurements were walking in fifteen stroke with hemiparesis on the 3D motion analysis system. Comparison of AFO and SCKAFO are gait pattern. The difference between the AFO and SCKAFO conditions was significant in the gait velocity, step length of the right affected side, stance time of both legs, step-length asymmetry ratio, single-support-time asymmetry ratio, ${\phi}$-thigh angle and ${\phi}$-shank angle in the mid swing (p<.001). Using a SCKAFO in stroke patients has shown similar to normal walking speeds can be attained for walking efficiency and is therefore desirable. In this study, the support time of the affected leg with the SCKAFO was longer than with the AFO and the asymmetry ratio of single support time decreased by more than with the AFO. This indicates that the SCKAFO was effective for improving gait symmetry, single-support-time symmetry. This may be due to the decrease of gait asymmetry. Thus, the newly designed SCKAFO may be useful for promoting gait performance by improving the coordination of the extremity and decreasing gait asymmetry in chronic stroke patients.

• Korean Journal of Applied Biomechanics
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• v.25 no.2
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• pp.175-182
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• 2015

Objective : The purpose of this study was to investigate difference in fascicle behavior of the medial gastrocnemius during the locomotion with varying intensities, such as gait and one-legged and two-legged vertical jumping. Methods : Six subjects (3 males and 3 females; age: $27.2{\pm}1.6yrs.$, body mass: $62.8{\pm}9.8kg$, height: $169.6{\pm}8.5cm$) performed normal gait (G) at preferred speed and maximum vertical jumping with one (OJ) and two (TJ) legs. While subjects were performing the given tasks, the hip, knee and ankle joint motion and ground reaction force was monitored using a 8-infrared camera motion analysis system with two forceplates. Simultaneously, electromyography of the triceps surae muscles, and the fascicle length of the medial gastrocnemius were recorded using a real-time ultrasound imaging machine. Results : Comparing to gait, the kinematic and kinetic parameters of TJ and OJ were found to be significantly different. Along with those parameters, change in the medial gastrocnemius (MG) muscle-tendon complex (MTC) length ($50.57{\pm}6.20mm$ for TJ and $44.14{\pm}5.39mm$ for OJ) and changes in the fascicle length of the MG ($18.97{\pm}3.58mm$ for TJ and $20.31{\pm}4.59mm$ for OJ) were observed. Although the total excursion of the MTC and the MG fascicle length during the two types of jump were not significantly different, however the pattern of length changes were found to be different. For TJ, the fascicle length maintained isometric longer during the propulsive phase than OJ. Conclusion : One-legged and two-legged vertical jumping use different muscle-tendon interaction strategies.

• The Journal of Korean society of community based occupational therapy
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• v.4 no.1
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• pp.23-31
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• 2014

Objective : The objectives of this study were to compare the variables from Fitmeter accelerometer with them from CMS-70P(Zebris Medizintechnik Gmbh, Germany) and to suggest the availability the accelerometer in the field of occupational therapy. Methods : Twenty participants performed calling, drinking water, washing face and spooning and we measured Sum of Single Vector Magnitude(SSVM) and range of motion(ROM) on the wrist and elbow joints. Results :With respect to the wrist and elbow joints, SSVM and ROM differed significantly according to the task(calling, drinking water, washing face and spooning)(p<.001; p<.001; p<.001; p<.001). As for the wrist joint, SSVM and ROM did not show the significant correlation(p>.05) but as for the elbow joint, SSVM and ROM did show the significant correlation according to the task(p<.01; p<.001; p<.01; p<.05). With regard to the SVM-difference of wrist and elbow joints, calling and washing showed the significant difference (p<.001; p<.05) but drinking and spooning did not show the significant difference(p>.05; p>.05). Conclusion : We suggest that Fitmeter accelerometer would be use to record the kinematic variables during performance of ADL and it can compensate the function of CMS-70P as for the elbow joint than the wrist joint.

• Journal of Korean Neurosurgical Society
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• v.46 no.6
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• pp.532-537
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• 2009

Objective : Recently, motion preservation has come to the forefront of emerging technologies in spine surgery. This is the important background information of the emergence of cervical arthroplasty as an alternative to arthrodesis that offers the promise of restoring normal spinal movement and reduces a kinematic strain on adjacent segments. The study was designed to evaluate early surgical outcome and radiological effects of $Bryan^{(R)}$ cervical disc prosthesis. Methods : The authors retrospectively reviewed radiographic and clinical outcomes in 52 patients who received the $Bryan^{(R)}$ Cervical Disc prosthesis, for whom follow-up data were available. Static and dynamic radiographs were measured by computer to determine the angles formed by the endplates of the natural disc preoperatively, those formed by the shells of the implanted prosthesis, the angle of functional spine unit (FSU), and the C2-7 Cobb angle. The range of motion (ROM) was also determined radiographically, whereas clinical outcomes were assessed using Odom's criteria, visual analogue pain scale (VAS) and neck disability index (NDI). Results : A total of 71 $Bryan^{(R)}$ disc were placed in 52 patients. A single-level procedure was performed in 36 patients, a two-level procedure in 13 patients, and a three-level procedure in 3. Radiographic and clinical assessments were made preoperatively. Mean follow-up duration was 29.2 months, ranging from 6 to 36 months. All of the patients were satisfied with the surgical results by Odom's criteria, and showed significant improvement by VAS and NDI score (p < 0.05). The postoperative ROM of the implanted level was preserved without significant difference from preoperative ROM of the operated level (p < 0.05). 97% of patients with a preoperative lordotic sagittal orientation of the FSU were able to maintain lordosis. The overall sagittal alignment of the cervical spine was preserved in 88.5% of cases at the final follow up. Interestingly, preoperatively kyphotic FSU resulted in lordotic FSU in 70% of patients during the late follow up, and preoperatively kyphotic overall cervical alignment resulted in lordosis in 66.6% of the patients postoperatively. Conclusion : Arthroplasty using the $Bryan^{(R)}$ disc seemed to be safe and provided encouraging clinical and radiologic outcome in our study. Although the early results are promising, this is a relatively new approach, therefore long-term follow up studies are required to prove its efficacy and its ability to prevent adjacent segment disease.

• Korean Journal of Applied Biomechanics
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• v.19 no.3
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• pp.467-479
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• 2009

The purpose of this study was to present the quantitative data which riders can utilize teaching field by comparison analysis of kinematics according to skill level of rider during 2 strides rising trot with the JeJu's-Horse. Participated subjects was consisted of total 10 riders(unskilled: n=5, skilled: n=5). The method of experiment & analysis was based on 3D cinematography. Variables were consisted of temporal, linear & angular kinematics by each event & phase. The skilled assigned more ratio of elapsed time in air than support phase, had the less range of motion in up-down direction and more consistent velocity in lateral & forward direction and performed periodic up-down movement with alignment in vertical direction according to elapsing of phases. The skilled more flexed at elbow and extended backwardly according to elapsing of phases, while more flexed forwardly at hip & knee and plantarflexion at ankle. The skilled postured backward extension but the unskilled do forward flexion. That is, It was considered that the unskilled continued more unstable posture than the skilled during 2 strides in rising trot.

• Korean Journal of Applied Biomechanics
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• v.19 no.1
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• pp.77-85
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• 2009

This study is aimed at providing information on injury prevention and skill improvement by inducing the accurate movements in exercise as well as understanding the principles of badminton drive movements. Movement displacement of racket head showed the similar patterns among those surveyed but, it seemed that slight differences resulted from external factors such as height, length of brachial and forearm and individual trend of swing locus. Regarding upper joint angle per phase, the angles of shoulder joint, elbow joint and wrist joint were closely associated in taking drive movements and they supported the segment order theory that power was conveyed from proximal into distal. It was shown that angular velocity of upper joint became larger in follow through movement after impact among all those surveyed, which meant the importance of follow through in racket sports such as badminton. In conclusion, this follow through movement acts as an important factor in racket sports in terms of pose stability maintenance, pose correction of movements and injury prevention of joints. In summary, when swings are made according to segment order theory, efficient movements can be taken.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.1
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• pp.344-350
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• 2013

A recent study reporting significantly reduced symmetry in arm swing amplitude in early Parkinson's disease (PD), as measured during gait by auditory cues velocity, led to this investigation of arm swing symmetry and amplitude in PD. The subjects were 14 elderly patients diagnosed with PD. Patients were measured of three conditions performed in random order: slow, general, fast. The auditory cue velocity consisted of a metronome beat ${\pm}20%$ than the subject's general gait speed. Using a motion analysis measurement system, changes in kinematic variables were compared to arm swing analysis. PD groups showed a highly significant reduction of the arm swing amplitude on the more affected body side(MAS)(p<.05). Comparison between the auditory cues velocity, there was a significant increase arm swing amplitude in fast velocity gait than slow and general velocity gait(p<.05). We conclude that motion analysis during gait by auditory cues velocity allows reliable investigation of asymmetric arm movements in early PD patients which attenuate with ongoing disease. The measurement of limb kinematics during gait by auditory cues velocity can broaden our methodological line-up for the analysis of complex motor programs in movement disorders.