Reliability of Axial-Thoracolumbar Spine Rotation Range Measurements

정성훈,하성민,김준희,곽경태,김수정 KEMA학회 2018 근골격계과학기술학회 Vol.2 No.1

Background Although numerous measurement methods exist for thoracolumbar spine rotation, achieving an accurate measurement of axial-thoracolumbar spine rotation is difficult because it is usually measured in the open kinematic chain. Purpose Therefore, the purpose of our study was to investigate the reliability of a new method for measuring axial-thoracolumbar spine rotation in the closed kinematic chain. Study design Intra-tester repeated measures Methods 14 healthy participants performed axial-thoracolumbar rotation. An electromagnetic tracking system was used to measure the angle of axial-thoracolumbar rotation in the sternum’s jugular notch and xiphoid process. Results The test-retest reliability of the axial-thoracolumbar rotation angle per the sensor on the jugular notch was 0.83, and the measurement from the sensor on the xiphoid process was 0.84. Conclusions The measurement of the axial-thoracolumbar rotation angle in the supine position showed excellent reliability. Background Although numerous measurement methods exist for thoracolumbar spine rotation, achieving an accurate measurement of axial-thoracolumbar spine rotation is difficult because it is usually measured in the open kinematic chain. Purpose Therefore, the purpose of our study was to investigate the reliability of a new method for measuring axial-thoracolumbar spine rotation in the closed kinematic chain. Study design Intra-tester repeated measures Methods 14 healthy participants performed axial-thoracolumbar rotation. An electromagnetic tracking system was used to measure the angle of axial-thoracolumbar rotation in the sternum’s jugular notch and xiphoid process. Results The test-retest reliability of the axial-thoracolumbar rotation angle per the sensor on the jugular notch was 0.83, and the measurement from the sensor on the xiphoid process was 0.84. Conclusions The measurement of the axial-thoracolumbar rotation angle in the supine position showed excellent reliability.

Enumeration of axial rotation

Yoon, Yong-San Techno-Press 2014 Advances in biomechanics & applications Vol.1 No.2

In this paper, two procedures of enumerating the axial rotation are proposed using the unit sphere of the spherical rotation coordinate system specifying 3D rotation. If the trajectory of the movement is known, the integration of the axial component of the angular velocity plus the geometric effect equal to the enclosed area subtended by the geodesic path on the surface of the unit sphere. If the postures of the initial and final positions are known, the axial rotation is determined by the angular difference from the parallel transport along the geodesic path. The path dependency of the axial rotation of the three dimensional rigid body motion is due to the geometric effect corresponding to the closed loop discontinuity. Firstly, the closed loop discontinuity is examined for the infinitesimal region. The general closed loop discontinuity can be evaluated by the summation of those discontinuities of the infinitesimal regions forming the whole loop. This general loop discontinuity is equal to the surface area enclosed by the closed loop on the surface of the unit sphere. Using this quantification of the closed loop discontinuity of the axial rotation, the geometric effect is determined in enumerating the axial rotation. As an example, the axial rotation of the arm by the Codman's movement is evaluated, which other methods of enumerating the axial rotations failed.

토릭 소프트콘택트렌즈의 축 회전에 따른 각막수차의 변화

황민준(Min-Jun Hwang),김도균(Do-Kyun Kim),김소라(So Ra Kim),박미정(Mijung Park) 한국안광학회 2021 한국안광학회지 Vol.26 No.3

Purpose: In this study, the effect of changes in corneal aberrations when wearing toric soft contact lenses (hereinafter toric lenses) and the effect of axial rotation of toric lenses on optical correction were investigated. Methods: A total of 41 myopic WTR-astigmatic eyes of patients in their 20s were included in this study, excluding those with monocular visual acuity <0.8, or axial rotation >5° when wearing a toric lens with a double-thin design for axis stabilization. The corrective effect was determined by measuring total, lower-order, and higher-order aberrations of the corneas before and after wearing the toric lens, after which the change in aberration was measured after rotating the lenses by 30±5°. Results: Corneal total and lower-order aberrations were significantly reduced when wearing toric lenses, and the aberration increased again when the axis was rotated. In particular, in the high astigmatism groups, the corneal aberrations were of almost the same level as before wearing the toric lens, indicating the most significant reduction in the corrective effect of the contact lenses. In addition, despite wearing toric lenses, the corneal higher-order aberration significantly increased, and its degree was greater during axial rotation. As the pupil size increased from 4 mm to 6 mm, all corneal aberrations increased by more than double the for each measurement. Conclusions: This study revealed that axial rotation of the toric lens causes significantly larger corneal aberrations than those at the axis stabilization, and the degree of change increases as the astigmatism increases. Therefore, when the wearer’s degree of astigmatism is high, the wearers vision-related habits for minimizing axial rotation as well as considering the fit and design of toric lenses, may be essential to obtain high visual satisfaction.

원문 : 태권도 주춤서 지르기 시 골반 종축 선(先)회전 동작의 운동역학적 특성 및 효과

최치선 ( Chi Sun Choi ) 한국스포츠정책과학원(구 한국스포츠개발원) 2013 체육과학연구 Vol.24 No.3

이 연구의 목적은 태권도 주춤서 지르기 시 골반 종축 선회전 동작의 운동역학적 특성을 연구하는데 있다. 이러한 목적을 달성하기 위하여 태권도 품새 전문 선수 11명을 대상으로 동작 속도를 별도 통제하지 않고 최대한 빠르고 강하게 허공의 몸통을 목표로 한 오른손 주춤서 지르기를 5회 실시하였다. 3차원 동작분석 시스템과 지면반력기를 통하여 분석에 필요한 각종 자료들을 획득하였고, 실험대상자를 15개 분절로 모델링 및 지역 좌표계를 설정하여 분석에 필요한 각종 변인들을 산출하였다. 분석 결과, 골반 종축 선회전 동작은 주먹을 지르기 위해 동작을 준비하는 구간에서 골반을 상체보다 먼저 빠른 속도로 목표방향으로 회전시키는 동작으로서, 비선회전 집단은 동작 준비 구간에서 골반과 상체를 거의 동시에 회전시키며 지르기 동작을 시작하는 반면에, 선회전 집단은 골반을 목표 방향으로 비선회전 집단에 비해 먼저 4배 가량 빨리 회전시킨 후 상체의 회전이 뒤따라가는 특성을 나타냈다. 또한 선회전 집단은 비선회전 집단에 비하여 골반의 회전 동작 시간이 짧았고, 허리와 오른쪽 어깨 부위 근육군의 파워가 각각 약 2배와 1.5배 큰 것으로 나타나, 짧은 동작 시간 동안 큰 파워를 내는 숙련된 기술의 특성을 나타냈다. 이 연구의 골반 종축 선회전 동작은 하나하나의 낱기술이 아닌 태권도 전체 기술에 적용될 수 있는 기능으로서, 다른 손동작과 차기 등에 동일하게 적용한다면 빠르고 강한 회전 동작을 만들어 낼 수 있어, 교육 시 태권도 기능 및 경기력 향상에 도움이 될 것이라 기대한다. The purpose of this study was to investigate the biomechanical characteristics and efficiencies of the pelvic axial pre-rotational movement for the Jireugi in the Taekwondo Juchumseogi stance. Eleven elite Taekwondo Poomsae athletes participated in the experiment. Each participant performed 5 right hand Jireugi in Juchumseogi stance as fast and strong as possible while their motion was recorded by a 3D motion analysis system and the ground reaction forces by two force plates. A 15-segment model with 15-local coordinate systems were used. The phase time, axial rotational angle of the pelvis and trunk, relative pelvis-trunk rotational angle, angular velocity, and maximal speed of the fist were measured according to each of the pelvis axial pre-movement conditions. To evaluate the efficiency, the power of the waist and right shoulder were also calculated using the inverse dynamics method. The pelvic axial pre-rotational movement had a pelvis rotation earlier and faster than the trunk during the preparation phase of the Jireugi. For the none pre-rotation group, the pelvis and trunk rotated almost simultaneously, but pre-rotation group rotated the pelvis about 4 times faster than the other group and this led to the trunk’s rotation. The pre-rotation group’s pelvic rotation time was shorter, the power of the waist and the right shoulder were about 2 times and 1.5 times greater respectively, than the none pre-rotation group. Thus, this seems to be a way to characterize skill level. The pelvic axial pre-rotational movement of this study may be applied to the all techniques of Taekwondo such as the hand skills and kicks. It has the effect of shortening of the range of movement, creating a fast and more powerful rotation, thus increasing the magnitude of impact. Therefore if the coaches educate their players to use this movement, then they will be able to produce quicker more powerful techniques.

Equitranslational and Axially Rotational Microrobot using Electromagnetic Actuation System

최현철,정세미,고광준,이정,JINZHEN,고성영,박종오,박석호 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.3

Recently, many researchers have focused on wireless microrobots as therapeutic agents for active drugdelivery. Owing to their size limitation, they cannot be equipped with actuators/sensors, controllers and batteries. Therefore, external devices (magnetic field generator, position recognition devices, and control system) are usedto realize the main functions (locomotion, sensing, and therapy) of biomedical microrobots and thus, to minimizetheir size. Especially, the small wireless microrobots, inserted into the human body, should have various steering,locomotive, and therapeutic functions for diagnosis and treatment. Generally, an external magnetic field is widelyused for the locomotion of a wireless microrobot. However, microrobots using an external magnetic field cannotsimultaneously realize equitranslational and axial rotational motions in the same microrobot system. In this paper,we developed an electromagnetic actuation (EMA) system and a spiral-shape microrobot and proposed its actuatingalgorithm. The developed wireless microrobot can show equitranslation and axial rotation in the same microrobotsystem. Finally, various experiments in a test-bed and in a blood vessel phantom validated that the developedmicrorobot can move to a target position by equitranslation and can penetrate a thrombus model by axial rotation.

Numerical study on the internal flow characteristics of an axial-flow pump under stall conditions

Kan Kan,Yuan Zheng,Yujie Chen,Zhanshan Xie,Guang Yang,Chunxia Yang 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.10

When an axial-flow pump works in low flow rate conditions, rotating stall phenomena will probably occur, and the pump will enter hydraulic unsteady conditions. The rotating stall can lead to violent vibration, noise, turbulent flow, and a sharp drop in efficiency. This affects the safety and stability of the pump unit. To study the rotating stall flow characteristics of an axial-flow pump, the steady and unsteady internal flow field in a large vertical axial-flow pump was investigated using 3D computational fluid dynamic (CFD) technology. Numerical calculations were carried out using the Reynolds-averaged Navier–Stokes (RANS) solver and Menter's shear stress transport (SST) k-ω turbulence model. Steady flow characteristics including streamline, velocity vector, pressure and turbulent kinetic energy are presented and analyzed. Unsteady flow characteristics are described using post-processing signals for pressure monitoring points in the time and frequency domains. Using Q-criterion, the locations and evolution rules of the core region of the vortex structure in guide vanes under deep stall conditions were investigated. The reliability of the numerical simulation results was verified using the experimental prototype pressure fluctuation test. In this way, typical flow structure and pressure fluctuation characteristics in an axial-flow pump were analyzed, with contrastive analysis in design condition and stall conditions. Finally, the mechanism of low-frequency pressure fluctuation in a pump unit under the stall condition was revealed.

높은 Prandtl 수 유체에서 축회전이 열모세관 유동의 진동에 미치는 영향

전승원(Seung-Won Jeon),이규정(Kyu-Jung Lee) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11

A numerical study on oscillatory thermocapillary flow in half-zone has performed to understand the effect of axial rotation. 2d unsteady code is developed to observe the onset of oscillation. 2cs Silicone oil with Prandtl number of 26.5 is used as a working fluid. The critical temperature difference at onset of oscillation is investigated under the different aspect ratios and rotation modes. It is shown that the onset of oscillation is delayed when aspect ratio reduces and rotating speed increases. The oscillatory flow is strongly reduced under top rotation and co-rotation modes, while it is augmented under bottom rotation and counter-rotation modes. It is thought that interaction between return flow and bottom wall is important to explain the oscillatory flow.

가스터빈 엔진 모델 버너의 공기과잉률에 따른 연소현상 연구

진유인(Yu-In Jin),유경원(Gyong-Won Ryu),김택현(Taek-Hyun Kim),김용련(Yeong-Ryeon Kim),민성기(Seong-Ki Min) 한국추진공학회 2014 한국추진공학회 학술대회논문집 Vol.2014 No.12

본 연구는 가스터빈 연소기의 핵심구성품인 연료노즐과 스월러에 대한 점화 및 화염의 보염성능을 확인하기 위한 실험적인 연구이다. 연소기 모델 버너에 사용된 연료노즐은 압력식 선회노즐이며, 동축반전 스월러(Axial Counter-rotating Swirler)를 장착하여 연료 미립화를 증가시키면서 화염의 보염성능을 높이도록 하였다. 연소기 모델 버너의 유동특성을 파악하기 위해 수류시험을 수행하여 연소기 내부에 강한 재순환영역이 분포하는 것을 확인하였으며, 공기과잉률 0.39 ~ 2.40 범위에 대하여 점화 가능영역과 화염의 보염특성 및 화염안정화 특성을 계측하였다. 연소기 버너 모델의 안정적인 점화 가능영역은 공기과잉률이 1.04 이내인 것으로 확인되었으며, 희박연소 한계값은 2.30 근처인 것으로 나타났다. 또한 연소기 버너 모델에서 공기과잉률이 증가할수록 완전연소 영역이 스월러 출구면으로 이동하는 것을 확인할 수 있었다. An experimental study was conducted to investigate combustion phenomena with respect to the air excess ratio(α) between 0.39 and 2.40 of the annual-type gas turbine model burner which consists of a pressure swirl nozzle and an axial-type counter-rotating swirler. Swirl-flow structure generated by the counter-rotating swirler was measured at water flow tests with same Reynolds number. The results showed that the strong recirculation zone clearly appeared in the combustor chamber. Stable ignition was possible at the air excess ratio below 1.04. LBO(Lean blow-out) limit appeared around the air excess ratio of 2.30. In addition, with the air excess ratio increase, flame was gradually close to the swirl exit.

주관절 운동의 상완,전완좌표계 타당도 및 굴곡/신전과 회내/회외의 상호작용

김진욱 ( Jin Uk Kim ) 한국운동역학회 2010 한국운동역학회지 Vol.20 No.2

The axes of upper forearm coordinate system have been considered as principal axis of each segment which was component of elbow joint. The purpose of this study was to verify whether the mean direction(principal axis) of instantaneous axes of rotation for pure flexion/extension motion coincided with the flexion/extension axis of upper forearm coordinate system. The same procedure was done for pronation/supination motion. Futhermore, it was tested indirectly that there was an interaction effect between the two rotational motions. The results showed that most segment coordinate axes statistically were not consistent with the mean directions of flexion/extension and pronation/supination axes of rotation. From the results, it would be concluded that the ISB coordinate systems was proved to be a little valid for human movement analysis. There also was an effect of pronation/supination angles on flexion/extension motion.

축회전 다이아그리드 구조시스템의 내진성능평가에 관한 연구

윤상호,박성수 대한건축학회지회연합회 2015 대한건축학회연합논문집 Vol.17 No.1

최근 초고층 구조물은 단순 생활공간이 아닌 도시의 랜드마크적인 기능을 할수 있도록 점차 그 형태가 다양해지고 있다. 다이아그리드 구조시스템은 외부에 위치하는 반복된 삼각 트러스 형태로서 수평하중 및 수직하중에 저항하는 시스템이고, 외부기둥을 제거하여 비정형 형상을 자유롭게 표현할수 있다. 최근에 다이아그리드 구조시스템에 대한 연구는 활발하게 진행 중이지만, 비정형 형태인 다이아그리드 구조시스템에 대한 연구는 상대적으로 설계경험이나 연구가 미흡하다. 따라서 본 연구는 비정형 구조물 형태중 twisted(뒤틀림)을 적용하여 축회전 다이아그리드 구조시스템의 내진성능평가에 관한 연구를 하였다. 선형시간이력해석과 비선형정적해석을 수행하여 층간변위와 최대밑면전단력 통해 가새각도와 구조시스템 평면의 회전각도 변화에 따른 다이아그리드 구조시스템의 내진성능평가에 관한 연구를 하였다. Since the high-rise structures have been played a role the city's Landmarks, the form of high-rise structures are becoming diverse. Diagrid structural system resists horizontal loads and vertical loads as a repeated triangular truss type along the entire exterior perimeter surfaces of the building. Due to eliminate vertical columns in exterior. This system can express complex shape buildings. Recently, diagrid structural system has been studied actively in many field. But study of atypical diagrid structural system, and experience of the design is relatively lack. Therefore, In this study the seismic performance of axial rotation-diagrid structure system was evaluated by applying the one twist in the form of atypical structures. Seismic performance of diagrid structural system was evaluated by change of the rotation angle of structural system plane and angle of external braces throught story drift and maximum base shear performed nonlinear static and linear time history analysis