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Search Results: 1 - 10 of 2829 matches for " center of rotation "
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The Precise Methods for the Measurement of Collimator Hole Angulation and Center of Rotation of SPECT by Adaptive Quality Control Phantom  [PDF]
Hossein Zamani Zeinali, Mehran Ataee, Hamid Ravanbakhsh, Ehsan Masumi Goodarzi, Samana Ghoreishi, Gholamreza Raisali
World Journal of Nuclear Science and Technology (WJNST) , 2014, DOI: 10.4236/wjnst.2014.44026
Abstract: The Adaptive Quality Control Phantom (AQCP) is a computer-controlled phantom which positions and moves a radioactive source in the Field of View (FOV) of an imaging nuclear medicine device on a definite path to produce a spatial distribution of gamma rays to perform QC Tests such as the Collimator Hole Angulation (CHA) and the Center of Rotation (COR) of Single Photon Emission Computer Tomography (SPECT). The collimator hole angulation for six collimators was measured using a point source and a computer-controlled cylindrical positioning system. In this method, the displacement of the image of a point source was examined as the AQCP was moving point source vertically away from the collimator face. The results of the high-accuracy measurement method of CHA show that the measurement accuracy for absolute angulation errors is better than ±0.024°. The Root Mean Square (RMS) of CHA for LEHR, LEHS and LEUHR collimators of SMV dual heads camera and LEGP, MEGP and HEGP of GE Millennium MG were evaluated to be 0.290°, 0.292°, 0.208°, 0.154°, 0.220° and 0.202°, respectively. It is to be added in this connection that the evaluated RMS of CHA for LEHR collimator with the distance variation from the collimator’s surface ±1 mm has been varied ±0.04 degree. A new method for the center of rotation assessment by AQCP is introduced and the results of this proposed method as compared with the routine QC test and their differences are discussed in detail. We defined and measured a new parameter called Dynamic Mechanical Error (DME) for applying the gantry motion correction.
A new kinematics method of determing elbow rotation axis and evaluation of its feasibility

- , 2016, DOI: 10.3969/j.issn.1671-167X.2016.02.007
Abstract: 目的:利用光学定位系统测量肘关节在屈曲、旋转活动时的运动学数据并进行可视化显示和分析,探索新的肘关节外固定旋转轴的定位方法,并对其可行性进行评估。 方法:利用光学定位系统,分别采集4位正常成年志愿者和6例Sawbone肘关节模型进行五次肘关节屈曲活动时的运动学数据,利用最小二乘法拟合肘关节旋转轴线,对运动学数据和拟合结果进行可视化显示并计算得到平均运动平面和平均运动转轴,从而确定旋转轴;应用标准临床方法对6例Sawbone肘关节模型透视下定位旋转轴的出、入点,并置入克氏针标记代表旋转轴,比较两种方法定位旋转轴的入点、出点及角度偏差。 结果: 每位志愿者5条运动轴线与其平均运动转轴之间的距离偏差均小于3 mm,角度偏差均小于5°;两种定轴方法确定的6例肘关节模型旋转轴的入点偏差平均为1.697 2 mm,出点偏差平均为1.838 3 mm,角度偏差平均为1.321 7° ,偏差均很小,在临床实际操作的可接受范围之内。 结论:肘关节单次屈曲运动轨迹的圆度及共面性良好,可以把肘关节的屈曲伸直活动视为近似固定轴线的运动;该新定轴方法在准确性上可以替代传统方法,并弥补传统定轴方法的不足。
Objective:To study a new positioning method of elbow external fixation rotation axis, and to evaluate its feasibility. Methods: Four normal adult volunteers and six Sawbone elbow models were brought into this experiment. The kinematic data of five elbow flexion were collected respectively by optical positioning system. The rotation axes of the elbow joints were fitted by the least square method. The kinematic data and fitting results were visually displayed. According to the fitting results, the average moving planes and rotation axes were calculated. Thus, the rotation axes of new kinematic methods were obtained. By using standard clinical methods, the entrance and exit points of rotation axes of six Sawbone elbow models were located under X-ray. And The kirschner wires were placed as the representatives of rotation axes using traditional positioning methods. Then, the entrance point deviation, the exit point deviation and the angle deviation of two kinds of located rotation axes were compared. Results: As to the four volunteers, the indicators represented circular degree and coplanarity of elbow flexion movement tra-jectory of each volunteer were both about 1 mm. All the distance deviations of the moving axes to the ave-rage moving rotation axes of the five volunteers were less than 3 mm. All the angle deviations of the mo-ving axes to the average moving rotation axes of the five volunteers were less than 5°. As to the six Sawbone models, the average entrance point deviations, the average exit point deviations and the average angle deviations of two different rotation axes determined by two kinds of located methods were respectively 1.697 2 mm, 1.838 3 mm and 1.321 7°. All the deviations were very small. They were all in an accep-table range of clinical practice. Conclusion: The values that represent circular degree and coplanarity of volunteer's elbow single curvature movement trajectory are very small. The result shows that the elbow single curvature movement can be regarded as the approximate fixed axis movement. The new method can replace the
New method for determining apparent axial center of rotation of lumbar and thoracic spine segments
Sanjum P. Samagh, MS,Charles D. Rosen, MD,Karimdad Otarodifard, MD,Matthew Kornswiet, MS
Journal of Rehabilitation Research and Development , 2011,
Abstract: One main question in spinal kinematics is the determination of the spine’s apparent axial center of rotation. Previous research on this topic has yielded contradictory results. The objective of this study was to determine the apparent axial center of rotation for seven lumbar and six thoracic spinal segments by developing and validating a new method. A custom six-degree-of-freedom device, allowing full range of motion, was used with motion recording and analysis software. This system tracked a grid of markers on a specimen when rotational torque was applied in both clockwise and counterclockwise directions at 3.53 Nm, 7.05 Nm, 10.58 Nm, and 14.10 Nm.The area encompassing the apparent axial center of rotation was determined by identifying the five markers with the least amount of motion. The marker angular displacement was calculated as the angle between a virtual line drawn between two points in the initial and final torque conditions. Rotation in both directions was averaged. The lumbar and thoracic spinal segments averaged an apparent axial center of rotation at the posterior border of the vertebral endplates and the anterior border of the spinal canal, with average clockwise to counterclockwise angular displacement ratios of 0.87 and 0.97, respectively.
On the Rotation Speed Measurement Method Based on Digital Image Correlation

- , 2016, DOI: 10.7520/1001-4888-15-093
Abstract: Aiming at kinematic parameter measurement of rotating mechanism, a method of measuring kinematic parameters, such as the rotation angle, the rotation speed and the velocity instantaneous center etc., is proposed in this paper, based on digital image correlation technique. Reliability analysis was carried out by using simulated speckle pattern. Results show that if taking the average value of test results from multiple regions as reliable test results, the measurement accuracy of rotation angle can reach 0.01°, and the measurement accuracy of velocity instantaneous center can reach sub-pixel level. Authors have established a rotation speed image measurement system, which was used to measure the rotational speed and the velocity instantaneous center of a motor shaft. Experimental results further indicate that above proposed method which is based on digital image correlation, has high accuracy and stability in practical engineering measurement
On the Curvature of Rotating Objects  [PDF]
Martin Tamm
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.66087
Abstract: In this paper, we investigate a certain property of curvature which differs in a remarkable way between Lorentz geometry and Euclidean geometry. In a certain sense, it turns out that rotating topological objects may have less curvature (as measured by integrating the square of the scalar curvature) than non-rotating ones. This is a consequence of the indefinite metric used in relativity theory. The results in this paper are mainly based of computer computations, and so far there is no satisfactory underlying mathematical theory. Some open problems are presented.
Nonlinear Polarizability of Erythrocytes in Non-Uniform Alternating Electric Field  [PDF]
Konstantin V. Generalov, Vladimir M. Generalov, Alexander S. Safatov, Alexander G. Durymanov, Galins A. Buryak, Margarita V. Kruchinina, Mikhail I. Voevoda, Andrey A. Gromov
Open Journal of Biophysics (OJBIPHY) , 2014, DOI: 10.4236/ojbiphy.2014.43011
Nonlinear polarizability of erythrocytes in non-uniform alternating electric field (NUAEF) was proved theoretically and experimentally by dielectrophoresis method. The paper presents experimental evidence of the nonlinear polarizability of erythrocytes in the non-uniform alternating electric field. The rotation of erythrocyte around its own axis at more than one revolution per second in the non-uniform alternating electric field in the frequency range \"\"and the electric field intensity \"\"is the evidence of its nonlinear polarizability. The theoretical analysis of the density of electric charges capable of overcoming the membrane potential was carried out on the basis of statistical mechanics, the thermal equilibrium in which the particle stays. The nonlinear polarizability of the erythrocyte emerges if the voltage on the membrane exceeds \"\", which was theoretically proved. The alternating electric field from the donor erythrocyte with the amplitude exceeding \"\"forms the constant component of the current \"\" in the cytoplasm of the recipient erythrocyte whose energy can be considered as a signal one. The nonlinear equivalent electric circuit of the cell was proposed.
Revisiting Galactic Rotation Curves Given a Noncommutative-Geometry Background  [PDF]
Peter K. F. Kuhfittig, Vance D. Gladney
Journal of Modern Physics (JMP) , 2014, DOI: 10.4236/jmp.2014.517187
Abstract: It was shown earlier by Rahaman et al. that a noncommutative-geometry background can account for galactic rotation curves without the need for dark matter. The smearing effect that characterizes noncommutative geometry is described by means of a Gaussian distribution intended to replace the Dirac delta function. The purpose of this paper is two-fold: 1) to account for the galactic rotation curves in a more transparent and intuitively more appealing way by replacing the Gaussian function by the simpler Lorentzian distribution proposed by Nozari and Mehdipour and 2) to show that the smearing effect is both a necessary and sufficient condition for meeting the stability criterion.
A Modified Relativistic Model of Gravitational Propagation  [PDF]
Jonathan Peter Merrison
International Journal of Astronomy and Astrophysics (IJAA) , 2016, DOI: 10.4236/ijaa.2016.63026
Abstract: A novel model of gravity is proposed and developed by modifying general relativity through propagating the gravitational field in an entirely analogous way to that of electromagnetic fields. It is therefore not a purely geometric model of gravitation, but is self-consistent, having clear causality and has the benefit of being inherently compatible with unified field theories. This model reproduces the observed almost constant rotational velocities of many galaxies as well as other large scale non-Keplerian motion. This is achieved without assuming the existence of dark matter and is made possible by modelling a rapidly rotating central star which with the inclusion of a velocity induced Doppler shift (of gravity) generates a highly anisotropic and intense, sheet like gravitational field. At extremely high gravitational fields this model remains real and finite i.e. does not generate a black hole, instead it asymptotically approaches a field limit below which light may escape. This is due to the inclusion of self-interaction of gravity in vacuum leading to a non-li nearity in the propagation of gravitational energy i.e. the effects of a gravitational field upon itself. This model is implemented computationally using an iterative finite element model. On the scale of our solar system these corrections are small and are shown not to be in obvious disagreement with high precision solar system tests.
Use of the partogram in labor: Analysis of its application in different care models  [PDF]
Cláudia de Azevedo Aguiar, Roselane Gon?alves, Ana Cristina d’Andretta Tanaka
Open Journal of Obstetrics and Gynecology (OJOG) , 2013, DOI: 10.4236/ojog.2013.39A001

Objective: To compare and identify possible differences in the use of the partogram in different models of delivery and birth care. Design/Setting: This was a cross-sectional study performed in two Brazilian hospitals with different models of care: Natural Birth Center (NBC) and Traditional Obstetric Center (TOC). Data were collected from the medical records of 112 mothers with low obstetric risk who underwent an intrapartum cesarean section. Socioeconomic and demographic variables, obstetric history, partogram labor evolution, complications, and indication of cesarean section were included. A significance level of 5% and a confidence interval of 95% were considered. Data were analyzed in accordance with the Brazilian Ministry of Health and World Health Organization recommendations. Findings: In the NBC, the use of the partogram follows the Ministry of Health recommendations for filling-in variables with greater frequency and significance (p < 0.001) beginning with the active phase of labor in the correct column in relation to the lines of alert and action (p = 0.00, OR = 42.2) and continuous records (p = 0.00, OR = 53.3). However, obstetric interventions, such as use of oxytocin, amniotomy and cesarean delivery were concentrated in area 1 of the partogram in both institutions. Conclusions: In this study, the NBC used the instrument most adequately; however there was no difference from the other model (TOC) and regarding the moment of interventions, many of them were early. This finding implies that, regardless of the care model, the partogram has been used bureaucratically and not as a guiding instrument of assistance envisioning safely and timely practices. In other words, aside from a “humanized” physical structure, it is necessary that obstetric practices should be focused on best evidence, thus reducing maternal and perinatal risks.

Sistemas de cultivo no cerrado e dinamica de popula??es de plantas daninhas
Pereira, F.A.R.;Velini, E.D.;
Planta Daninha , 2003, DOI: 10.1590/S0100-83582003000300002
Abstract: this research aimed to evaluate the effects of no-tillage systems using crop rotation variations, conventional tillage, and minimum tillage on the dynamics of weed populations in the cerrado region in brazil. the experiment was arranged in a randomized block design, four replications and five treatments, (two no tillage treatments consisting of summer and fall/winter crop rotations and two single crop treatments under conventional tillage and minimum tillage. weed population dynamics was evaluated. the results showed that the no-tillage system was the most efficient for weed control with the following programs: soybean/sorghum - crotalaria/corn - millet/soybean, winter corn/soybean); (winter corn/soybean - sunflower/corn - sorghum/soybean - sunflower/corn) and (pigeon/pea/soybean - millet/soybean - winter corn/corn - sunflower/soybean) .
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