• 한국기계가공학회지
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• 제18권1호
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• pp.1-8
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• 2019

The optimal design parameters of a dynamic absorber (DA) in a machine body (that is considered as a rigid body) are discussed in this paper. The bounce and rotation motions of the rigid body have been controlled passively by a DA, which consists of a mass and a spring. The rigid body is subjected to a harmonically excited force and supported by linear springs at both ends. To define the motion of a rigid body with a DA, the equation of motion was expressed in the third-order matrix form. To define the optimal design conditions of a DA, the reduction of dynamic characteristics, represented by the amplitudes of bounce and rotation, and the transmitted powers, were evaluated and discussed. The level of reduction was found to be highly dependent on the location and spring stiffness of the DA.

• 대한기계학회논문집B
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• 제25권3호
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• pp.339-346
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• 2001

The impulsive spin-up flow in a shallow rectangular container is analyzed numerically by quasi 3-D unsteady laminar flow. In the non-inertia coordinates, the flow is generated by the virtual forces as Coriolis force, etc.. After the boundary layers grow up near sidewalls, primary vortexes separate from the sidewalls. As the Reynolds number increases, the subsidiary vortexes take place in the boundary layer. The rigid body rotation is started from the inner region and propagated to the outer region, finally all the fluid reaches the rigid body rotation. According to the Reynolds number and the aspect ratio, the development of vortex pattern is symmetric or asymmetric.

• 천문학회보
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• 제36권1호
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• pp.56.1-56.1
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• 2011

To understand the effect of the initial rotation for tidally bounded clusters with mass spectrum, we performed N-body simulations for the clusters with different degrees of initial rotation and compared to Fokker-Planck results. We confirmed that the cluster evolution is accelerated by the initial rotation as well as the mass spectrum. For the slowly rotating models, the time evolution of mass, energy and angular momentum show good agreements between N-body and Fokker-Planck calculations. On the other hand, for the rapidly rotating models, there are significant differences between two approaches at the beginning of the evolution. By investigating cluster shapes, we concluded that these differences are mainly due to secular instability that takes place for very rapidly rotating clusters. The shape of cluster for N-body simulations becomes tri-axial or even prolate, while the 2-dimensional Fokker-Planck simulation can treat only oblate type axisymmetric systems. We also founded that there is the angular momentum exchange from high mass to low mass.

• 한국운동역학회지
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• 제16권1호
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• pp.55-63
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• 2006

The purpose of this study is to prove the kinematical characteristics of Deff motion, the high bar performance, in terms of flying phases so that we can provide basic sources for improving gymnastic performance. To do this, we selected and analyzed the performance of two athletes who did Deff motion in the high bar competition of male artistic gymnastic in the 22nd Universiade 2003 Daegu. We drew the conclusions from the kinematical factors that were came out through analyzing three-dimensional cinematography of the athletes' movements, by using a high speed video camera. To make a successful performance, a performer releases the bar at a height of a high bar vertically and at a height of 82cm horizontally, and the flying performance should be made without moving forward, as maintaining the proper balance, in order to rise over 118cm high during the flying phase. When the performer is releasing the bar, an increase of the vertical speed in the center of the body and extension of a knee joint and a hip joint contribute to increasing a flying height. And when the moving body is twisted, leaning to left side is caused by the winding movement of a knee joint, which causes an unstable bar grasp. To grasp the bar stably, just before releasing the performer should gain propulsive force from twisting rotation through increasing the speed of shoulder rotation. And before the peak point, the performer should make sure of a body rotation distance over $164^{\circ}$ so that he or she can do an aerial rotary performance smoothly. When grasping the high bar, the center of the body should be above the bar and the angle of shoulder rotation should be maintained close to $540^{\circ}$ simultaneously. he high point performance(S1) has more speed on an ascending phase and less speed on a descending phase than the low point performance (S2). At the peak point, both the rotation angle of the body and that of the shoulder in high point performance are big as well. In conclusion, it is shown that a performer can make a jump toward the high bar easily with the body straight because the performer can hold the upper part of the body erect early in a descending phase.

• The Korean Journal of Physiology
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• 제24권1호
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• pp.103-113
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• 1990

The role of cervical proprioceptors in the control of body posture was studied in bilaterally labyrinth-ectomized, decerebrate cats. The animals were suspended on hip pins with the neck extended horizontally. With this placement the EMG activities of extensor and flexor muscles of the upper extremities were observed by means of sinusoidal head rotator. The rotator can induce two kinds of neck movement: The one is 'pitch' which describes a rotatory neck motion to transverse axis of the body and mainly occurs at skull-C1 (atlantooccipital) joint and the other is 'roll', side-to-side relation of the neck to longitudinal axis, whose center is C1-C2 (atlanto-axial) joint. The following results were obtained. 1) Responses of EMG activity were closely dependent on the rotatory range of the neck. And the EMG activity was not changed during sustained neck torsion, eliciting a typical tonic neck reflex. 2) On pitching movement, the head-up rotation produced the excitation of bilateral triceps muscles, whereas the head-down rotation produced the inhibition. And the response of bilateral biceps muscles was the opposite to that of triceps. 3) On rolling movement, the side-up rotation of the head produced the excitation of ipsilateral triceps muscles and the inhibition of contralateral ones. And the response of biceps muscles was the opposite to that of triceps. 4) The minimum requirement of motion to evoke EMG activities in the upper extremities was $3.2^{\circ}{\sim}12.5^{\circ}$. These results have shown that the cervical proprioceptors produce tonic discharge on the upper brachial muscles, regulate the EMG activities of those muscles, and are very sensitive to neck rotation. And it can be stated that the cervical proprioceptors may play an important role in the control of body posture and movement.

• 대한물리의학회지
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• 제13권4호
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• pp.149-162
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• 2018

PURPOSE: The aim of this study was to investigate the effect of scapular dynamic taping on pain, disability, upper body posture, and range of motion (ROM) in the postoperative shoulder. METHODS: Twenty-two patients who underwent acromioplasty and rotator cuff repair surgery volunteered for this study. The subjects were randomly divided into an experimental group (EG, n=11) and a control group (CG, n=11). For the EG, exercise therapy, manual therapy, and scapular dynamic taping were applied for 6 weeks; for the CG, only exercise therapy and manual therapy were applied for 6 weeks. Shoulder pain, disability, upper body posture, and ROM were evaluated at baseline, after 3 weeks of intervention, and after 6 weeks of intervention. Assessment tools included quadruple visual analog scale (QVAS) for level of pain; shoulder pain and disability index (SPADI) for functional disability level; forward head angle (FHA), forward shoulder angle (FSA), and pectoralis minor index (PMI) for upper body posture; and ROM testing. RESULTS: Significant differences were observed between the EG and CG in SPADI total scores; internal rotation and external rotation ROM of the glenohumeral joint ; FSA ; and PMI. All groups showed statistically significant improvement in QVAS; SPADI; flexion; abduction; external rotation and internal rotation ROM of the glenohumeral joint; FSA; and PMI. CONCLUSION: These results suggest that, for patients who have undergone acromioplasty and rotator cuff repair surgery, the addition of scapular dynamic taping during therapy is effective for improvement of shoulder disability level, ROM, and upper body posture.

• 대한물리의학회지
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• 제5권1호
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• pp.1-6
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• 2010

Purpose : This research intended to find out the effects of scalenus medius muscle relaxed posture on the increase of head-neck rotation for general adults. Methods : This research was conducted on 30 subjects whose both sides head neck rotation angles are not the same and that agreed to participate in the experiment. In a posture of sitting erectly on a mat, both sides head neck rotation angles were measured with C-ROM equipment, and while supporting arm in direction opposite the side where head neck rotation limited and leaning over the body at 45 degree and neck at vertical condition against ground, head-neck rotation angles were measured each with C-ROM equipment. Results : The Head-Neck rotation angle on the side of limited head-neck rotation demonstrated more increase in scalenus medius relaxed posture than in erect sitting posture, showing significant difference statistically(p<0.05). The head-neck rotation angle on the side of non-limited Head-Neck rotation demonstrated more decrease in scalenus medius relaxed posture than in erect sitting posture, not showing any significant difference statistically (p>0.05). Conclusions : This posture may be used for preventing limit of head-neck rotation caused of scalenus medius muscle tension and increasing head-neck rotation.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2011년도 춘계학술대회 논문집
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• pp.1407-1408
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• 2011

• Clinics in Shoulder and Elbow
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• 제18권1호
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• pp.13-20
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• 2015

Background: The purpose of this study is to assess the range of shoulder motion using an indirect evaluation method without physical examinations of patients based on questionnaires regarding several specific arm postures referenced by patient's own body parts. Methods: Nine criteria of specific shoulder motion including 4 forward flexion, 2 external rotation, and 3 internal rotation were decided as reference position which can represent a certain shoulder motion. Flexion contains postures such as lifting arm to waist-height, shoulder-height, eye-height, and raising arm above head with arm touching ears. External rotation comprises grasping ears and placing hands on back of the head. Vertebral height in internal rotation is determined by calculating the samples' motions, which are holding on to trouser belts, opposite-elbow, and scapula. These postures are included in questionnaires for patients to evaluate the validity and effectiveness of this indirect method. Results: The range of flexion was $77^{\circ}$ ($60^{\circ}$ to $100^{\circ}$), $96^{\circ}$ ($87^{\circ}$ to $115^{\circ}$), $135^{\circ}$ ($115^{\circ}$ to $150^{\circ}$), and $167^{\circ}$ ($150^{\circ}$ to $175^{\circ}$) when arms go up to waist, shoulder, eye, and high vertically. Range of external rotation was $39.6^{\circ}$ ($30^{\circ}$ to $50^{\circ}$) when grasping ears and $69.2^{\circ}$ ($60^{\circ}$ to $80^{\circ}$) with the hands on the back of the head. Range of internal rotation was L4 when placing trouser belts, T12 for holding opposite elbow, and T9 for reaching scapula. The mismatch rates of flexion, external rotation, and internal rotation were 11.6%, 9.6%, and 7.8%. Conclusions: The range of shoulder motion using this method is expected to be applied to an established shoulder scoring system which included shoulder motion evaluation item.

• 대한인간공학회지
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• 제32권3호
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• pp.245-252
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• 2013

Objective: This paper analyzes the changes on stride parameters, joint angles, and trajectories of the body parts due to high heels during walking and explains the causal relationship between the changes and high heels. Background: This study aims to indicate the comprehensive gait changes by high heels on the whole body for women wearing high heels and researchers interested in high-heeled walking. Method: The experiment was designed in which two different shoe heel heights were used for walking (1cm, 9.8cm), and twelve women participated in the test. In the experiment, 35 points on the body were tracked to extract the stride parameters, joint angles, and trajectories of the body parts. Results: Double support time increased, but stride length decreased in high-heeled walking. The knee inflexed more at stance phase and the spine rotation became more severe. The trajectories of the pelvis, the trunk and the head presented outstanding fluctuations in the vertical direction. Conclusion: The double support time and the spine rotation were changed to compensate instability by high heels. Reduced range of motion of the ankle joint influenced on the stride length, the knee flexion, and fluctuations of the body parts. Application: This study can provide an insight of the gait changes by high heels through the entire body.