• Physical Therapy Rehabilitation Science
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• v.12 no.2
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• pp.149-154
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• 2023

Objective: This study is designed to investigate the effect of ankle joint position on hip extensor muscle activity when bridging exercise in sagittal plane. Design: Cross-sectional study Methods: The subjects were recruited from 20 healthy adult men. The subjects performed three types of bridging exercises (normal bridging, ankle dorsiflexion bridging, ankle plantar flexion bridging) three times for five seconds with a rest of 15 seconds between measurements and two minutes of rest between each motion. The target muscles were the gluteus maximus, biceps femoris, soleus, and tibialis anterior. A surface electromyography was used to measure the muscle activity of these muscles. Results: The results show there was no statistically significant difference between the three types of exercise in the gluteus maximus muscle activity. However, the biceps femoris showed a significant difference between the three types of exercises (p<0.05). Conclusions: In conclusion, when the three different bridging exercises were performed by adding ankle motion to normal bridging exercise, there was a significant difference in the muscle activity of the gluteus maximus relative to the biceps femoris muscle activity in the order of the ankle dorsiflexion bridging, normal bridging, and ankle plantar flexion bridging exercise. Therefore, this could be an effective option for a bridging exercise if applied to patients with a weak gluteal muscle and shortening of the hamstring muscle in further studies.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.7
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• pp.579-586
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• 2016

This paper describes kinematic analysis of a 6-degrees-of-freedom (DOF) ultra-precision positioning stage based on a flexure hinge. The stage is designed for processes which require ultra-precision and high load capacities, e.g. wafer-level precision bonding/assembly. During the initial design process, inverse and forward kinematic analyses were performed to actuate the precision positioning stage and to calculate workspace. A two-step procedure was used for inverse kinematic analysis. The first step involved calculating the amount of actuation of the horizontal actuation units. The second step involved calculating the amount of actuation of the vertical actuation unit, given the the results of the first step, by including a lever hinge mechanism adopted for motion amplification. Forward kinematic analysis was performed by defining six distance relationships between hinge positions for in-plane and out-of-plane motion. Finally, the result of a circular path actuation test with respect to the x-y, y-z, and x-z planes is presented.

• Korean Journal of Applied Biomechanics
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• v.21 no.4
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• pp.437-447
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• 2011

In this study, the lower limbs joints were analyzed for features based on the biomechanical characteristics of landing techniques according to height and landing on the ground type (flats and downhill). In order to achieve the objectives of the study, changes were analyzed in detail contents such as the height and form of the first landing on the ground at different angles of joints, torso and legs, torso and legs of the difference in the range of angular motion of the joint, the maximum angular difference between joints, the lower limbs joints difference between the maximum moment and the difference between COM changes. The subjects in this study do not last six months did not experience joint injuries 10 males in 20 aged were tested. Experimental tools to analyze were the recording and video equipment. Samsung's SCH-650A model camera was used six units, and the 2 GRF-based AMTI were used BP400800 model. 6-unit-camera synchronized with LED (photo cell) and Line Lock system were used. the output from the camera and the ground reaction force based on the data to synchronize A/D Syc. box was used. To calculate the coordinates of three-dimensional space, $1m{\times}3m{\times}2m$ (X, Y, Z axis) to the size of the control points attached to the framework of 36 markers were used, and 29 where the body was taken by attaching a marker to the surface. Two kinds of land condition, 40cm and 60cm in height, and ground conditions in the form of two kinds of flat and downhill slopes ($10^{\circ}$) of the landing operation was performed and each subject's 3 mean two-way RM ANOVA in SPSS 18.0 was used and this time, all the significant level was set at a=.05. Consequently, analyzing the landing technique as land form and land on the ground, the changes of external environmental factors, and the lower limbs joints' function in the evaluation were significantly different from the slopes. Landing of the slop plane were more load on the joints than landing of plane. Especially, knee extensor moment compared to the two kinds of landing, slopes plane were approximately two times higher than flat plane, and it was statistical significance. Most of all not so much range of motion and angular velocity of the shock to reduce stress was important. In the further research, front landing as well as various direction of motion of kinetic, kinetic factors and EMG variables on lower limbs joints of the study in terms of injury-prevention-approach is going to be needed.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.1
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• pp.97-105
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• 2015

Recently, there have been many researches about applications of origami to mechanical engineering, which realizes a 30 sturcture by folding a 20 plane material. With this simple manufacturing process, origami was even adopted by some roboticists as a way to build an entirely new robot with benefits in terms of cost, weight, and structural simplicity In this paper, we propose a new type of a walking robot based on origami structure. Because all the components of the robot that generate gait motion are mechanically connected, it can actually walk fotward with only a single actuator. We also showed the similarity of gait trajectories between a kinematic analysis and the actual gait motion measured by video tracking. This result proved the possibility of designing an origami-based robot with the identical gait trajectory as we plan.

• Earthquakes and Structures
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• v.16 no.3
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• pp.265-277
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• 2019

Framed masonry wall structures represent a typical high-rise structural system that are also seismically vulnerable. During ground motions, they are excited in both in-plane and out-of-plane terms. The interaction between the frame and the infill during ground motion is a highly investigated phenomenon in the field of seismic engineering. This paper presents a numerical investigation of two distinct static out-of-plane loading methods for framed masonry wall models. The first and most common method is uniformly loaded infill. The load is generally induced by the airbag. The other method is similar to in-plane push-over method, involves loading of the frame directly, not the infill. Consequently, different openings with the same areas and various placements were examined. The numerical model is based on calibrated in-plane bare frame models and on calibrated wall models subjected to OoP bending. Both methods produced widely divergent results in terms of load bearing capabilities, failure modes, damage states etc. Summarily, uniform load on the panel causes more damage to the infill than to the frame; openings do influence structures behavior; three hinged arching action is developed; and greater resistance and deformations are obtained in comparison to the frame loading method. Loading the frame causes the infill to bear significantly greater damage than the infill; infill and openings only influence the behavior after reaching the peak load; infill does not influence initial stiffness; models with opening fail at same inter-storey drift ratio as the bare frame model.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.3
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• pp.253-263
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• 2004

The problem considered in this paper is about the collocation of sensor and actuator for the active control of sound and vibration. It is well-known that a point collocated sensor-actuator pair offers an unconditional stability with very high performance when it is used with a direct velocity feedback (DVFB) control, because the pair has strictly positive real (SPR) property. In order to utilize this SPR characteristics, a matched piezoelectric sensor and actuator pair is considered. but this pair suffers from the in-plane motion coupling problem with the out-of-plane motion due to the piezo sensor and actuator interaction. This coupling phnomenon limits the stability and performance of the matched pair with DVFBcontrol. As a new alternative, a point sensor and distributed piezoelectric actuator pair is also considered, which provides SPR property in all frequency range when the pair is implemented on a clamped-clapmed beam. The use of this sensor-actuator pair is highly expected for the applications to more practical active control of sound and vibration systems with the DVFB control strategy.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.6
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• pp.502-508
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• 2012

An analytical model for a human body is important to predict muscle and joint forces. Because it is difficult to estimate muscle or joint forces from a human body, the objective of this study is the development of a reliable analytical model for a human body to evaluate the lower extremity muscle and joint forces. The musculoskeletal system of the human lower extremity is modeled as a multibody system employing the Hill-type muscle model. Muscle forces are determined to minimize energy consumption, and we assume that motion is constrained in the sagittal plane. Muscle forces are calculated through an equilibrium analysis while rising from a seated position. The musculoskeletal model consists of four segments. Each segment is a rigid body and connected by frictionless revolute joints. Muscles of the lower extremity are simplified to seven muscles with those that are not related to the sagittal plane motion are ignored. Muscles that play a similar role are combined together. The results of the present study are compared with experimental results to validate the lower extremity model and the assumptions of the present study.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.8
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• pp.848-855
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• 2008

In this paper, we describe correspondence among multiple images taken by multiple cameras. The correspondence among multiple views is an interesting problem which often appears in the application like visual surveillance or gesture recognition system. We use the principal axis and the ground plane homography to estimate foot of human. The principal axis belongs to the subtracted silhouette-based region of human using subtraction of the predetermined multiple background models with current image which includes moving person. For the calculation of the ground plane homography, we use landmarks on the ground plane in 3D space. Thus the ground plane homography means the relation of two common points in different views. In the normal human being, the foot of human has an exactly same position in the 3D space and we represent it to the intersection in this paper. The intersection occurs when the principal axis in an image crosses to the transformed ground plane from other image. However the positions of the intersection are different depend on camera views. Therefore we construct the correspondence that means the relationship between the intersection in current image and the transformed intersection from other image by homography. Those correspondences should confirm within a short distance measuring in the top viewed plane. Thus, we track a person by these corresponding points on the ground plane. Experimental result shows the accuracy of the proposed algorithm has almost 90% of detecting person for tracking based on correspondence of intersections.

• Journal of the Society of Naval Architects of Korea
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• v.53 no.4
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• pp.307-314
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• 2016

Energy flow analysis(EFA) is a representative method that can predict the statistical energetics of structures at high frequencies. Generally, as the frequency increases, the shear distortion and rotatory inertia effects in the out-of-plane motion of beams or plates become important. Therefore, to predict the out-of-plane energetics of coupled structures in the high frequency range, the energy flow analyses of Timoshenko beam and Mindlin plate are required. Unlike the energy flow model of Kirchhoff plate, the energy flow model of Mindlin plate is composed of three kinds of energy governing equations(out-of-plane shear wave, bending dominant flexural wave, and shear dominant flexural wave). This paper performed the energy flow finite element analysis(EFFEA) of coplanar coupled Mindlin plates. For EFFEA of coplanar coupled Mindlin plates, the energy flow finite element formulation of out-of-plane energetics in the Mindlin plate was performed. The general EFFEA program was implemented by MATLAB® language. For the verification of EFFEA of Mindlin plate, the various numerical applications were done successfully.

• Journal of the korean academy of Pediatric Dentistry
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• v.11 no.1
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• pp.13-24
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• 1984

To Study the eruption pattern of the maxillary first permanent molar, the author took 266 cases of true lateral cephalogram (Male; 137 cases, Female; 129 cases) from 3 to 7 years old children and observed the vertical change and axial change. The following results were obtained: 1. The angle of axial inclination of the maxillary first permanent molar to the F-H plane increased gradually from age 3 to 7, except for age 6 in both sexes. There was a slight reversal of this motion at age 6. 2. The distance from the cusp of the maxillary first permanent molar to the occlusal plane slightly decreased from age 3 to 5, and rapidly decreased from age 5 in both sexes. 3. The change of angle of the axial inclination resulted in the distance from the distobuccal cusp of the maxillary first permanent molar to the occlusal plane decreasing more than that from the mesiobuccal cusp of the maxillary first permanent molar to the occlusal plane in both sexes. 4. The eruption of the maxillary first permanent molar generally was found to be earlier in girls than boys.