• 한국운동역학회지
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• 제17권1호
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• pp.61-68
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• 2007

The purpose of this study was to analyze the shoulder joint torque and muscle pattern performing as Tennis serve by Isokinetic motions on Isomed 2000. The subject, who was 5 males Korean national high school tennis players. By analyzing the flexion/extension of the shoulder, the peak torque of the internal/external rotation motion(at 60,180 and 300 degree/sec) at peak torque degree, the weight, peak torque, and power. combined with the timing of the electrode of the attached trapezius and posterior deltoid at the three part. From the data analysis & discussion the following conclusions were drawn. When doing a shoulder extension, the peak torque can be widely seen at 60degree per second. However the degree may be different depending on angular velocity. When doing an internal rotation at 90degree abduction, peak torque per weight was seen at 60degree per second. The degree of peak torque was at 31.6-44.2 and peak power was faster when angular velocity was increased. The aspect of muscle pattern was seen more at the internal rotation in the 90degree abduction rather than the shoulder extension. However the angular velocity was not influenced by muscle mobilization(in order of anterior deltoid, posterior deltoid and trapezius. To properly apply the above conclusion, when tennis players serve it is better the elbow be impacted by the extension. when doing isokinetic motion it is better to increase angular velocity and improve muscle power. also the anterior deltoid amongst the shoulder muscle should be improved to develop serve speed.

• 한국기계기술학회지
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• 제13권4호
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• pp.1-7
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• 2011

The paper concerns numerical study of fully developed laminar flow of a Newtonian water and non-Newtonian fluids, 0.2% aqueous of sodium carboxymethyl cellulose(CMC) solution in eccentric annuli with combined bulk axial flow and inner cylinder rotation. Pressure losses and skin friction coefficients have been measured when the inner cylinder rotates at the speed of 0~200 rpm. A numerical analysis considered mainly the effects of annular eccentricity and inner cylinder rotation. The present analysis has demonstrated the importance of the drill pipe rotation and eccentricity. In eccentricity of 0.7 of a Newtonian water, the flow field is recirculation dominated and unexpected behavior is observed. it generates a strong rotation directed layer, that two opposing effects act to create two local peaks of the axial velocity. The influences of rotation, radius ratio and working fluid on the annular flow field are investigated.

• 한국소음진동공학회논문집
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• 제13권11호
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• pp.860-867
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• 2003

This paper presents a systematic method measuring a velocity disturbance to design the robust seek loop system of optical disk drives. The velocity disturbance caused by the rotation of a disk has a greater influence on the performance of the seek control loop as the rotational speed increases. Thus, it needs to measure the extent of the velocity disturbance and design the seek control loop based on the measured data. The measurement method of the velocity disturbance is a real-time . method using a measurable velocity and a velocity controller output and is a robust method considering actuator uncertainties. The loop gain adjustment algorithm is introduced to compensate for the actuator uncertainties. The proposed method is implemented by an experimental digital system and is evaluated through an experiment.

• 한국의학물리학회지:의학물리
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• 제24권4호
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• pp.243-252
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• 2013

본 연구는 표적이 규칙적으로 움직일 때 생기는 4DCT 영상의 모션 아티팩트(motion artifact) 관련된 원인들인 partial volume effect (PVE), partial projection effect (PPE), 각각의 프레임의 시작점 사이에 불일치(MMimph)의 원인들은 조사 및 분석을 목적으로 했다. 본 기관에서 제작된 흉부팬텀과 아크릴의 두개의 원기둥팬텀(반지름: 2 cm, 길이: 0.5 cm/ 반지름: 2 cm, 길이: 10 cm)이 규칙적인 움직이는 동안 CT을 이용하여 4D 영상을 획득했다. 촬영은 자동시작과 각각의 프레임의 시작점을 일치시키기 위해 매뉴얼로 두 가지 방법으로 시작하였다. 첫번째 실험에서는 CT 캔트리 rotation time은 5초와 8초가 이용되었다. 각 프레임은 다른 위상으로 시작되었다. 두번째 실험에서는 각 프레임에서 같은 위상으로 시작되게 하기 위해 매뉴얼로 시작했다. 세번째 실험에서는 원기둥팬텀을 2초와 6초를 주기로 움직였다. 각각의 4DCT의 영상에서 표적의 부피를 구했다. 영상으로부터 구한 표적의 부피와 표적의 실제 부피와 비교를 통해 관계를 분석했다. 흉부팬텀 실험에서는 CT의 갠트리 속도가 팬텀의 움직임보다 빠를수록 PVE와 PPE의 영향이 적어짐에 따라 영상에서 얻은 표적부피는 실제에 근접했다. 각각의 프레임의 시작점이 일치할수록 움직임의 속도와 표적의 부피와 상관관계가 높았다. 원기둥팬텀에서는 흉부팬텀의 경우와 같이 갠트리 속도가 팬텀의 움직임보다 빠를수록 영상으로부터 구한 표적부피는 실제 표적부피에 근접했다. 특히 한 slice의 두께가 2.5 mm을 고려 할 때 axial방향의 PVE, PPE, 각각의 프레임의 시작점이 일치가 되는 상태를 시뮬레이션한 길이 10 cm의 원기둥팬텀 실험에서는 영상에서 얻은 표적부피는 표적이 정지되었을 때 영상에서 얻은 부피와 거의 일치했다. 팬텀이 느리게 움직일수록, CT 갠트리의 rotation 시간이 짧을수록 영상에서 얻은 표적부피는 실제 부피에 근접했다. CT 촬영 시 각각의 프레임의 시작점이 같을수록 표적의 속도와 영상에서 의한 표적의 부피는 상관관계가 높게 나타났다. CT 갠트리의 rotation 속도를 팬텀의 움직임보다 빠르게 하고, CT 촬영시 각의 프레임의 시작점을 일치시킬수록 실제의 팬텀부피에 근접하리라고 예상된다.

• Tribology and Lubricants
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• 제30권4호
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• pp.212-217
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• 2014

A counter gear transmits the rotation angle, so the angular velocity ratio of the gear does not necessarily need to be constant in the meshing process. As a pinion has a small number of teeth when combined with an internal gear for counters, tooth interference can occur with the use of an involute curve. This paper introduces circular arcs that represent a tooth profile and fillet for the profile design of a pinion through the combination of arcs with lines. The straight line of a rack tooth represents the profile of a mating internal gear. Thus, the circular arc and line maintain contact during the rotation of the counter gear. This paper presents an analysis of the meshing of the circular arc tooth and rack tooth along with the properties of the counter gear, such as the change in rotational velocity and amount of backlash. The contact ratio of the counter gear is 1 because the tooth contact occurs between circular arcs and line. The initial position of tooth contact, which denotes the simultaneous contact of two teeth, is found. As the rotation of the pinion, only one tooth keeps the contact situation. This meshing property is analyzed by the geometrical constraints of the tooth profile in contact and the results are presented as graphical diagrams in which tooth-arc movements are superimposed.

• 대한기계학회논문집B
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• 제20권10호
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• pp.3322-3333
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• 1996

A numerical analysis has been conducted to investigate a modified floating-zone crystal growth process in which most of the melt surface is covered with a heated ring. The crystal rod is not only pulled downward but rotated around its axisymmetric line during crystal growth process in order to produce the flat interface of crystal growth and the single crystal growth of NaNO3 is considered in 6mm diameter. The present study is made from a full-equation-based analysis considering a pulling velocity in all of solid and liquid domains and both of solid-liquid interfaces are tracked simultaneously with a governing equation in each domain. Numerical results are mainly presented for the comparison of the surface shape of rotational crystal rod with that of no-rotational crystal rod and the effects of revolution speeds of the crystal rod. Results show that the rotation of crystal rod produces more its flat surface. In addition, the shape of crystal growth near the centerline is more concaved with the increase in the revolution speed of crystal rod. The flow pattern and temperature distribution is analyzed and presented in each case. As the pulling velocity of crystal rod is increasing, the free surface of the melt below the heated ring is enlarged due to the crystal interface migrating downward.

• 한국운동역학회지
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• 제17권3호
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• pp.133-145
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• 2007

The purpose of this paper was to compare of difference between energy walking and normal walking. Subjects were selected 8 male undergraduates. The kinematic variables of a pelvis and a thorax were analysed at the take off and contact with 3d cinematography. In addition to the variables, the phase plot angle was calculated in order to definite characteristics in the phase space. The pelvic angle and angular velocity showed significant differences in the flexion/extension between two walking patterns. The pelvic angle and angular velocity were increasing when walking speed was increasing and magnitude of the variables of energy walking was larger than corresponding values for normal walking. On the other hand, the thoracic angle demonstrated significant differences in the flexion/extension and rotation between two walking patterns. The angles of energy walking were smaller in the flexion/extension and were larger in the rotation than the angle of normal walking. The kinematic characteristics of energy walking were also showed clearly significant differences in the range of motion and the relative angle of the trunk. The angle of phase plot only showed demonstrated a significant difference in the rotation at contact between the two walking patterns.

• 천문학회보
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• 제44권1호
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• pp.34.3-34.3
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• 2019

We report our discovery of observational evidence for the coherence between galaxy rotation and the average motion of neighbors. Using the Calar Alto Legacy Integral Field Area (CALIFA) survey data analyzed with the Python CALIFA STARLIGHT Synthesis Organizer (PyCASSO) platform, and the NASA-Sloan Atlas (NSA) catalog, we estimate the angular momentum vectors of 445 CALIFA galaxies and build composite maps of their neighbor galaxies on the parameter space of velocity versus distance. The composite radial profiles of the luminosity-weighted mean velocity of neighbors show striking evidence for dynamical coherence between the rotational direction of the CALIFA galaxies and the average moving direction of their neighbor galaxies. The signal of such dynamical coherence is significant for the neighbors within 800 kpc distance from the CALIFA galaxies with a confidence level of $3.5{\sigma}$, when the angular momentum is measured at the outskirt ($Re<R{\leq}2Re$) of each CALIFA galaxy. We also find that faint or kinematically misaligned galaxies show stronger coherence with neighbor motions than bright or kinematically well-aligned galaxies do. Our results show that the rotation of a galaxy, particularly at its outskirt, may be significantly influenced by recent interactions with its neighbors.

• 천문학회지
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• 제4권1호
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• pp.1-8
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• 1971

The average velocity, 330km/sec. of the high velocity stars with respect to the galactic center is obtained from the data used by Fricke on the assumption that the rotational velocity of the Local Standard of Rest is 250km/sec. Comparing this value with the escape velocity, 380km/sec, at the solar neighborhood which is calculated from Mestel's model of the Galaxy, it is shown that most of the high velocity stars are bound to the Galaxy and that their average apogalacticon is about 40 kpc from the galactic center. And the fact that stars with radial velocities larger than 63km/sec are missing in the direction of galactic rotation of L.S.R. is interpreted as the result partly of the random distribution of the directions of motion of the high velocity stars and partly of the observational errors.

• 대한기계학회논문집B
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• 제27권2호
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• pp.206-214
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• 2003

Mean flow and turbulence properties of developing turbulent flows in a 90 degree square bend with spanwise rotation were measured by a hot-wire anemometer. A slanted wire is rotated into 6 orientations and the voltage outputs from them are combined to obtain the mean velocity and Reynolds stress components. The combinative effects of the centrifugal and Coriolis forces due to the curvature and the rotation of bend on the mean motion and turbulence structures are investigated experimentally. Results show that the two body forces can either enhance or counteract each other depending on the flow direction in the bend.