• 한국지구과학회지
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• 제26권7호
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• pp.725-731
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• 2005

우리은하 속의 행성상성운들의 운동자료를 분석하여, 은하 회전의 운동학적 특성과 진화에 대한 단서를 제공한다. 우리는 THE STRASBOURG-ESO CATALOGUE OF GALACTIC PLANETARY NEBULAE에 주어진 자료 502개를 이용하여 행성상성운의 운동학적 특성을 분석하였다. 은경($\iota$)이 $0^{\circ},\;90^{\circ},\;180^{\circ},\;270^{\circ}$인 4방향과 태양의 향점과 배점의 총 6방향에 대한 특성적인 평균시선속도 $(V_r)s$를 구하였다. 행성상성운들은 향점에서 69.0 km/s로 태양에 접근하고, 배점$(56{\circ},\;236{\circ})$에서 64.1km/s로 멀어지고 있는 경향을 보였다. z 방향으로 행성상성운의 분포를 보면 은하면 아래쪽에 더 많이 분포하지만, 큰 차이는 보이지 않았다. 우리은하에 속한 천체 중 제 3세대인 행성상성운들의 회전속도 성분이 태양에 비해 상대적으로 느림을 알 수 있는데 이는 4세대 별인 태양이 제 3세대 별들과 조우할 수 있음을 암시한다.

• 대한기계학회논문집A
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• 제26권12호
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• pp.2636-2646
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• 2002

This research presents an analytical model to investigate vibration due to ball bearing waviness in a rotating system supported by two or more ball bearings, taking account of the centrifugal force and gyroscopic moment of the ball. The waviness of rolling elements is modeled by the sinusoidal function, and it is incorporated into the position vectors of the race curvature center. The Hertzian con tact theory is applied to calculate the elastic deflection and nonlinear contact force while the rotor has translational and angular motions. Both the centrifugal force and gyroscopic moment of the ball and the waviness of the rolling elements are included in the kinematic constraints and force equilibrium equations of a ball to derive the nonlinear governing equations of the rotor, which are solved by using the Runge-Kutta-Fehlberg algorithm to determine the new position of the rotor. The proposed model is validated by the comparison of the results of the prior researchers. This research shows that the centrifugal force and gyroscopic moment of the ball plays the important role in determining the bearing frequencies, i.e. the principal frequencies, their harmonics and the sideband frequencies resulting from the waviness of the rolling elements of ball bearing. It also shows that the bearing vibration frequencies are generated by the waviness interaction not only between the rolling elements of one ball bearing but also between those of two or more ball bearings constrained by the rotor.

• 한국운동역학회지
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• 제21권1호
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• pp.107-114
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• 2011

Closed kinematic chain exercises such as squatting have been widely indicated for knee rehabilitation in patients with patellofemoral disorders such as osteoarthritis and patellofemoral pain. Patellofemoral disorders are thought to be associated with abnormal patellar kinematics. In addition, the Q-angle may be undervalued in patients with patellofemoral pain and a laterally displaced patella. The purpose of this study was to assess patellar kinematics and the Q-angle during double-leg semi-squat and wall-slide semi-squat exercises. In this study, 28 asymptomatic subjects(16 male, 12 female) were assessed. Patellar tilt, patellar spin, and Q-angle were recorded using a motion analysis system during double-leg semi-squat and wall-slide semi-squat exercises. The Q-angle and patellar tilt were significantly increased, whereas patellar spin was significantly decreased, at $45^{\circ}$ of knee flexion compared with $0^{\circ}$. No differences were observed for the Q-angle, patellar tilt, and patellar spin during double-leg semi-squat and wall-slide semi-squat exercises. However, a significant interaction was observed between squat type and knee angle for patellar spin. We found that the patella is laterally tilted during semi-squat exercises and that there was no difference in patellar tracking between knee flexion during double-leg semi-squat and wall-slide semi-squat exercises.

• 한국전문물리치료학회지
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• 제23권3호
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• pp.48-56
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• 2016

Background: Recently, there has been an emphasis on the use of interventions with biofeedback information for the maintenance or correction of posture. Objects: This study assessed the change of trunk posture and trunk muscle activation when people exhibiting postural kyphosis performed visual display terminal work with or without a contact feedback device (CFD). Methods: Eighteen right-handed individuals were recruited. Thoracic angle and right thoracic erector spinae (TES) muscle amplitude were analyzed. There were two sessions in these experiments. The control session involved 16 minutes of typing without a CFD, and the CFD session involved 16 minutes of typing with a CFD. The visual analog scale score was analyzed with a paired t-test, and the kinematic and electromyography data were analyzed through two-way repeated analysis of variance. Results: The paired t-tests revealed that subjects had significantly less pain after the CFD sessions than after the control sessions (p<.05). Significant main effects by session and by time were observed in the thoracic kyphosis angle (p<.05). There was a significant session${\times}$time interaction for TES amplitude (p<.05), along with significant main effects by session and by time (p<.05). Conclusion: The CFD caused people with postural kyphosis to straighten and to activate their TES continuously, even though they were habituated to bend their bodies forward. Therefore, the CFD was a beneficial treatment tool.

• 디지털콘텐츠학회 논문지
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• 제13권2호
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• pp.255-262
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• 2012

사람 움직임 추적 알고리즘은 인간과 컴퓨터 상호작용, 화상회의, 감시 시스템, 게임 및 엔터테인먼트 분야에서 반드시 필요한 기술로 인식되고 있다. 과거 다양한 사람 움직임 추적 알고리즘들이 응용 프로그램의 특성에 따라 구현되고, 실시간성을 고려한 보다 효율적인 영상 처리, 컴퓨터 비전, 인터페이스 기술들을 적용하여 구현되고 있다. 본 논문에서는 타원체 형태의 신체 모델과 깊이값 정보를 갖는 3차원 점들과의 매칭을 통해 실시간으로 적용 가능한 움직임 추적 기술을 소개한다. 움직임 추적을 위한 기반 모델은 사람의 모습과 유사한 형태의 타원체 조합의 18개의 관절을 갖는 형태로 구성되어 지며, 영상으로부터 들어온 사람의 모습을 분석하여 일련의 신체 부위를 나누고, 그 정보를 바탕으로 역기구학 기반의 초기 자세를 추출한다. 초기 자세는 3차원 점 매칭 기법을 활용하여 보다 정확한 자세로 수정된다.

• Journal of Biosystems Engineering
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• 제43권4호
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• pp.379-385
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• 2018

Purpose: Postharvest handling of onions (harvesting, cleaning, grading, cooling, storing, and transport) should be performed continually to reduce costs and improve quality. The purpose of this study is to a) determine the design parameters and operating conditions of anion auto-dumping that constitutes a key component of the postharvest bulk handling machinery system, and b) to perform a performance test with the auto-dump prototype system. Methods: Kinematic analyses and computer simulations of the auto-dump mechanism were applied to analyze the operating conditions and design parameters. Results: The optimum working condition for the auto-dump was determined from kinetic analyses. In addition, the interaction between the velocity of the hydraulic cylinder and the angular velocity of the auto-dump were analyzed in order to control the bulk handling machinery system. The acting forces and optimum operating conditions of the hydraulic cylinder were determined by analyzing the forces related to the mass of inertia of the auto-dump assembly during rotation. The method of controlling the feeding rate of onions in terms of the uniformity of the stacking pattern and the control of the entire system was better than the two-stage method of controlling the rotational speed of the auto-dump. Based on the performance test with the prototype for the auto-dump, the stacking pattern and rigidity of the system were analyzed. Conclusions: These results would be of great importance in the postharvest bulk handling machinery system for onions.

• International Journal of Internet, Broadcasting and Communication
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• 제13권1호
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• pp.47-53
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• 2021

Gait kinematics and kinetics have a similar tendency between men and women, yet it remains unclear how walking while carrying a load affects the gait mechanism. Twenty adults walked with preferred velocity on level ground of 20 m relative to change of a load carriage (no load, 15%, 30% of the body weights) aimed to observe gait mechanism. We measured gait posture using the three-dimensional image analysis and ground reaction force system during stance phase on left foot. In main effect of gender difference, men showed increased displacement of center of gravity (COG) compared to women, and it showed more extended joint angle of hip and knee in sagittal plane. In main effect of a load difference, knee joint showed more flexed postuel relative to increase of load carriage. In main effect of load difference on the kinetic variables, medial-lateral force, anterior-posterior force (1st breaking, 2nd propulsive), vertical force, center of pressure (COP) area, leg stiffness, and whole body stiffness showed more increased values relative to increase of load carriage. Also, men showed more increased COP area compared to women. Interaction showed in the 1st anterior-posterior force, and as a result of one-way variance analysis, it was found that a load main effect had a greater influence on the increase in the magnitude of the braking force than the gender. The data in this study explains that women require little kinematic alteration compared to men, while men in more stiff posture accommodate an added load compared to women during gait. Additionally, it suggests that dynamic stability is maintained by adopting different gait strategies relative to gender and load difference.

• 한국전문물리치료학회지
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• 제30권1호
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• pp.59-67
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• 2023

Background: Posterior capsule tightness (PCT), commonly seen in overhead athletes, is a soft tissue adaptation that is also noted in non-throwers. PCT is associated with scapular and humeral kinematic alterations, significant restriction of shoulder internal rotation (IR) range of motion (ROM), and significant scapular anterior tilting. Sleeper and cross-body stretches (CBS) are suggested for PCT and IR deficits, and have been modified since introduction. A novel modified sleeper stretch (NMSS) was designed in this study to prevent the risk of anterior translation of the humeral head. Though the effects of posterior shoulder stretching exercise have been widely studies, to the best of our knowledge, no previous studies have investigated the effectiveness of posterior shoulder exercises in decreasing scapular anterior tilting. Objects: To compare the immediate effects of two posterior shoulder stretching exercises (NMSS and CBS) on scapular anterior tilting and shoulder IR ROM. Methods: Thirty-two subjects with anteriorly tilted scapula and IR deficits [mean age: 24.3 ± 2.5 years; 15 males and 17 females] participated in this study. Subjects were randomly assigned to either the NMSS or CBS groups. Scapular anterior tilting (at rest and at shoulder 60° active IR) and shoulder IR ROM were measured before and immediately after intervention. Results: Scapular anterior tilting significantly decreased, while the shoulder IR ROM significantly increased in both groups. However, there was no significant group-by-time interaction effect or significant difference between the groups. Conclusion: Both stretching exercises were effective in restoring shoulder IR ROM and decreasing scapular anterior tilting.

• 한국운동역학회지
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• 제25권2호
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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.

• 대한지역사회작업치료학회지
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• 제10권1호
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• pp.51-61
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• 2020

목적 : 정상인을 대상으로 팔뻗기 수행 시 물체 크기와 뻗기 거리가 상지의 운동형상학적 요소에 미치는 영향을 알아보고자 하였다. 연구 방법 : 대상자는 부산시 D대학교에 재학 중인 대학생 30명이며 측정 도구는 삼차원 동작 분석기인 CMS-70P(Zebris Medizintechnik Gmbh, Germany)를 사용하였다. 과제는 6가지 조건이다. 팔뻗기 수행시 물체 크기(2cm, 10cm)와 뻗기 거리(15%, 37.5%, 60%)의 변화에 따른 움직임의 평균 속도, 평균 가속도, 최대 속도, 속도의 정점수를 측정하였다. 대상자의 일반적 특성은 기술통계를 사용하였다. 두 가지 물체 크기에서 세 가지 뻗기 거리로 팔뻗기 과제를 수행했을 때 변수를 비교하기 위해 일원분산분석(One-way ANOVA measure)으로 분석하였고, 사후검정은 Tukey 검정을 실시하였다. 또한 세 가지 뻗기 거리에서 두 가지 물체 크기에 따른 운동형상학적 차이를 분석하기 위해서 독립 t검정(Independent t-test)을 사용하였다. 팔뻗기 거리(15%, 37.5%, 60%)와 물체 크기(2cm, 10cm)에 따른 상호작용효과를 확인하기 위해 이원분산분석(3×2 Two-way ANOVA measure)을 실시하였다. 통계적 유의수준 α는 .05로 설정하였다. 결과 : 정상인은 물체 크기와 뻗기 거리의 변화에 따라 상지 움직임에 유의한 차이가 있었다. 물체 크기가 동일한 경우 뻗기 거리가 길어질수록 평균 속도, 최대속도가 증가하였고, 속도의 정점 수는 감소하였다. 뻗기 거리가 동일한 경우 물체 크기가 커질수록 평균 속도, 최대 속도가 증가하였고 속도의 정점 수는 감소하였다. 물체 크기와 뻗기 거리의 변화는 평균 가속도에 영향을 미치지 않았으며 유의한 차이가 없었다. 결론 : 과제를 시간적, 공간적 특성으로 제한하는 것은 대상자의 상지 움직임에도 영향을 미치게 된다. 따라서 본 연구의 결과를 토대로 신경학적 기능수준에 따라 세밀하게 등급화된 과제제공에 도움이 될 것으로 사료된다.