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1
Powers, Michael E. "Rotator Cuff Training for Pitchers". Journal of Sport Rehabilitation 7, nr 4 (listopad 1998): 285–99. http://dx.doi.org/10.1123/jsr.7.4.285.
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This paper reviews the role of the rotator cuff during two key phases of the pitching sequence and presents a training program for these muscles. The program uses a periodization design consisting of three stages, beginning with a high-resistance/low-repetition eccentric strengthening stage. This is followed by a low-resistance/high-repetition stage for training muscular endurance. The core exercises for these two stages are prone external rotation in the 90/90 position, prone horizontal abduction, side-lying D2 flexion pattern, supine internal rotation in the 90/90 position, prone elevation with 100° of shoulder abduction and external rotation, and standing scapular plane elevation. The final stage of the program uses high-speed functional exercises: 90/90 external rotation, 90/90 internal rotation, D2 PNF flexion pattern, D2 PNF extension pattern, supine plyometric 90/90 internal rotation with a medicine ball, and the “arm whip” through the D2 PNF flexion pattern. The goal of this program is to prepare the muscles for the stresses of pitching and prevent shoulder injuries.
2
Alkadhimi, Aslam. "A novel and simple technique for correcting localised rotations in the early alignment stage". Journal of Orthodontics 47, nr 4 (27.08.2020): 338–44. http://dx.doi.org/10.1177/1465312520949553.
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Correcting severe tooth rotations can be challenging. There are many ways to de-rotate teeth with fixed or removable appliances. Mechanically, the best and most effective way is one that produces a two-force couple system to rotate a tooth around its centre of rotation (longitudinal axis). The aim of this article was to introduce a simple and efficient technique using a closed coil to correct localised tooth rotations in the early alignment stage, utilising a simple two-force couple system. Furthermore, some of the biomechanical principles concerning de-rotation will be revisited.
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Panov, V. F., O. V. Sandakova, E. V. Kuvshinova i D. M. Yanishevsky. "Evolution of the Universe with two rotating fluids". International Journal of Modern Physics A 35, nr 02n03 (30.01.2020): 2040042. http://dx.doi.org/10.1142/s0217751x20400424.
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An anisotropic cosmological model with expansion and rotation and the Bianchi type IX metric has been constructed within the framework of general relativity theory. The first inflation stage of the Universe filled with a scalar field and an anisotropic fluid is considered. The model describes the Friedman stage of cosmological evolution with subsequent transition to accelerated exponential expansion observed in the present epoch. The model has two rotating fluids: the anisotropic fluid and dust-like fluid. In the approach realized in the model, the anisotropic fluid describes the rotating dark energy.
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Ito, Yoichiro. "Two-phase Motion in Hydrodynamic Counter-current Chromatography". Current Chromatography 7, nr 2 (29.12.2020): 76–81. http://dx.doi.org/10.2174/2213240606666190912161221.
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Background: Motion of the two mutually immiscible liquids in hydrodynamic countercurrent chromatographic systems is speculated based on the observation of their behavior in a closed coiled tube rotating in unit gravity. Materials and Methods: The experiment revealed an up and down pattern of four stages of twophase volume ratio occupied at the head end of the coil according to the rotation speed. These two-phase behaviors are comprehensively explained on the bases of interplay between the unit gravity and centrifugal force generated by rotation of the coil. This theory is successfully extended to explain the two-phase behavior in a coil undergoing the type-I and type-J planetary motions. Results and Discussion: The type-I planetary motion produces the centrifugal force distribution similar to that of slowly rotating coil in unit gravity (Stage I), where both phases competitively move toward the head of the coil. In contrast, the type-J planetary motion displays complex distribution patterns of centrifugal force according to the location of the coil on the holder hence the two-phase motion varies with the ß values. When ß is 0.5 – 0.75, the force pattern simulates that of the rotating coil in unit gravity at 120 rpm (Stage III) where the lighter phase moves toward the head leaving the heavier phase behind. Conclusion: This clearly demonstrates the importance of the proper choice of ß values in highspeed countercurrent chromatography utilizing the type-J planetary motion.
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Wei, Zhicong, Wei Yang i Ruofu Xiao. "Pressure Fluctuation and Flow Characteristics in a Two-Stage Double-Suction Centrifugal Pump". Symmetry 11, nr 1 (8.01.2019): 65. http://dx.doi.org/10.3390/sym11010065.
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Pressure fluctuation is the primary factor that affects the stability of turbomachines. The goal of the present work is to explore the propagation of pressure fluctuations in a two-stage double-suction centrifugal pump. The pressure fluctuation characteristics of each component of a two-stage double-suction centrifugal pump are simulated under four typical flow rates based on the SST k-ω turbulence model. It is shown that the pressure fluctuation frequency at blade passing frequency and its first harmonic is the same at the suction chamber, the leading edge, and the middle of the first-stage impeller, which is different from the rotor–stator interaction. Moreover, the uneven impeller inlet flow distribution will produce fluctuations with rotation frequency and its harmonics at the leading edge of the impellers in both stages. Finally, broadband frequency is found at the trailing edge of the impellers in both stages associated with the first harmonic of the rotation frequency, especially under the part load condition. The large size backflow vortex appears in the blade flow channel leading to the low-pressure zone between the impeller, the tongue, and the start of the partition. That is why the pressure drops significantly twice in one rotation period when the blades pass through the tongue and the start of the partition.
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Luan, Hengxuan, Liyuan Weng, Ranhui Liu, Dongmin Li i Mingwei Wang. "Axial Spacing Effects on Rotor-Rotor Interaction Noise and Vibration in a Contra-Rotating Fan". International Journal of Aerospace Engineering 2019 (7.02.2019): 1–15. http://dx.doi.org/10.1155/2019/2125976.
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Because of the potential technical advantages, the contra-rotation technology has become a renewed interest in aviation and other applications. Contra-rotation increases efficiency in comparison with the single-rotor design, but this advantage is not fully harnessed. The axial spacing of two-stage contra-rotating blade rows has a significant impact on a contra-rotating fan/compressor. The results show that with a contra-rotation pattern, the strong unsteadiness of two-stage rotors is caused by the rotor-rotor interaction. The unsteadiness of rotor 1 is caused by the potential disturbance, and the upstream wake leads to the strong unsteadiness of rotor 2. With the increase of axial spacing, the rotor-rotor interaction is weakened, while unsteady features of two-stage rotor blades tend to be consistent. The acoustic and vibration effects of axial spacing are studied. It is found that the axial spacing has great influence of aerodynamic noise. The mean value of sound pressure level decreases by 17.2 dB in total when the axial spacing increased to 1.1 chord from 0.3 chord. For the accuracy of calculation, the scattering effect of the casing wall should be considered in the prediction of the noise. The axial spacing does not have obvious effects on the natural frequencies of the two-stage rotor blades but has certain effect on blade deformation.
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Ye, Tingting, i Yangmin Li. "Synthesis of 2-DOF Decoupled Rotation Stage with FEA-Based Neural Network". Processes 11, nr 1 (6.01.2023): 192. http://dx.doi.org/10.3390/pr11010192.
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Transfer printing technology has developed rapidly in the last decades, offering a potential demand for 2-DOF rotation stages. In order to remove decoupling modeling, improve motion accuracy, and simplify the control method, the 2-DOF decoupled rotation stages based on compliant mechanisms present notable merits. Therefore, a novel 2-DOF decoupled rotation stage is synthesized of which the critical components of decoupling are the topological arrangement and a novel decoupled compound joint. To fully consider the undesired deformation of rigid segments, an FEA-based neural network model is utilized to predict the rotation strokes and corresponding coupling ratios, and optimize the structural parameters. Then, FEA simulations are conducted to investigate the static and dynamic performances of the proposed 2-DOF decoupled rotation stage. The results show larger rotation strokes of 4.302 mrad in one-axis actuation with a 1.697% coupling ratio, and 4.184 and 4.151 mrad in two-axis actuation with undesired Rz rotation of 0.014 mrad with fewer actuators than other works. In addition, the first natural frequency of 2151 Hz is also higher, enabling a wider working frequency range.
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Gurney, Kevin, i Michael J. Wright. "Rotation and Radial Motion Thresholds Support a Two-Stage Model of Differential-Motion Analysis". Perception 25, nr 1 (styczeń 1996): 5–26. http://dx.doi.org/10.1068/p250005.
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Lower motion thresholds for rotational and radial flow have been measured for stimuli consisting of four closely packed circular apertures, each containing patches of drifting grating or plaid. Detection and direction thresholds were measured for gratings and plaids as a function of the relative orientation of the pattern components. There was a similarity between both types of threshold, supporting the existence of specialised rotation and radial-flow detectors. Further, thresholds increased with the relative component orientation for both gratings and plaids. This suggests that component information from a first stage, tuned spatiotemporally and to orientation, is being used directly to compute the optic flow in a two-stage process. A model based on this architecture is described by means of simple template receptive-field arrays with separable temporal and spatial tuning at the first stage.
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Zhang, Lei, i Abraham Engeda. "Numerical simulation of rotating stall in a two-stage axial fan". Thermal Science 22, Suppl. 2 (2018): 655–63. http://dx.doi.org/10.2298/tsci171025050z.
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Computational fluid dynamics calculations using high-performance parallel computing were conducted to simulate the prestall flow of a two-stage axial fan. The simulations were run with a full-annulus grid that models the 3-D, viscous, unsteady blade row interaction without the need for an artificial inlet distortion to induce stall. The simulation shows the initiation and development of the stall inception in two rotors of the axial fan. The results show that the stall inception first occurs in the second stage. The spike-type stall inception occurred in the second stage, which is different from the common views. The starting positions of stall inception in both rotors are in the same circumferential direction, and the stall inceptions in both rotors turn into mature stall cells at the same time. Also, the rotation speed of the stall inception and rotating stall in the two rotors are the same. The rotating stall in the first and second stage rotor impellers are both directly induced by the blade tip leakage flow. However, the blocked flow in the second stage rotor strengthens the leakage flow in the blade tip of the first stage rotor indirectly, resulting in the formation of stall inception.
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Malael, I., i V. Dragan. "Numerical and Experimental Efficiency Evaluation of a Counter-Rotating Vertical Axis Wind Turbine". Engineering, Technology & Applied Science Research 8, nr 4 (18.08.2018): 3282–86. http://dx.doi.org/10.48084/etasr.2231.
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This paper investigates the concept of a concentric counter-rotating vertical axis wind turbine (VAWT), consisting of a two stage vertical H-type turbine with three blades on each stage. The model has an inner and an outer stage, rotating in opposition to each other. Both numerical and experimental tests have been performed in order to validate this new concept. Numerical analysis is based on the use of 2.5-dimensional, unsteady simulations using a DOF type of analysis which allows for the two stages to self-adjust their rotation speed. Sliding mesh conformal interfaces are defined between these subdomains to minimize numerical artifacts such as artificial relations or entropy changes. Fully turbulent URANS were carried out in Ansys Fluent software. One key outcome was the momentum coefficient for each stage at different tip wind speed values. Another, more qualitative, outcome is the analysis of vortex shedding, impingement and overall interaction between the stages at different positions and scenarios. Ultimately, the numerical results have been validated using a scaled experimental device which was analyzed in the wind tunnel at different free stream speeds.
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Zhang, Zi Miao, Shi Hai Zhang i Ya Nan Yu. "Study on Axis Calibration Method of the Coordinate Measurement System Based on Binocular Vision". Advanced Materials Research 989-994 (lipiec 2014): 3266–69. http://dx.doi.org/10.4028/www.scientific.net/amr.989-994.3266.
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For a coordinate measurement system based on binocular vision, system calibration is an important factor for measurement accuracy. In this paper we present a flexible calibration method for the axis calibration of rotation stage which is installed in front of the binocular vision system to increase the system measurement range. By putting a standard ball in front of the binocular vision system, a sequence of pictures is taken by the two cameras with a few different rotation angles of the rotation stage. With the method of space intersection of two straight lines, the reference points (the ball centers at each rotation angles) for axis calibration are figured out. The trail of standard ball is a circle. Since all ball centers of rotation are on a plane perpendicular to the axis, the center of circle is on the axis of rotation stage. The rotation axis of stage is then calibrated according to the calibration model.
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Alfredsson, P. Henrik, i Håkan Persson. "Instabilities in channel flow with system rotation". Journal of Fluid Mechanics 202 (maj 1989): 543–57. http://dx.doi.org/10.1017/s002211208900128x.
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A flow visualization study of instabilities caused by Coriolis effects in plane rotating Poiseuille flow has been carried out. The primary instability takes the form of regularly spaced roll cells aligned in the flow direction. They may occur at Reynolds numbers as low as 100, i.e. almost two orders of magnitude lower than the critical Reynolds number for Tollmien-Schlichting waves in channel flow without rotation. The development of such roll cells was studied as a function of both the Reynolds number and the rotation rate and their properties compared with results from linear spatial stability theory. The theoretically obtained most unstable wavenumber agrees fairly well with the experimentally observed value. At high Reynolds number a secondary instability sets in, which is seen as a twisting of the roll cells. A wavytype disturbance is also seen at this stage which, if the rotational speed is increased, develops into large-scale ‘turbulence’ containing imbedded roll cells.
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Chai, Fu Jun, Jin You Xu i Ying Xu. "Kinematics Simulation of Steel Tube Rotating Mechanism Based on ADAMS". Applied Mechanics and Materials 130-134 (październik 2011): 2647–50. http://dx.doi.org/10.4028/www.scientific.net/amm.130-134.2647.
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Taking a new steel tube rotating mechanism as the research object, the model is simplified and the virtual prototyping model of the mechanism is established. The mechanism kinematics simulation is carried out with ADAMS simulation software. The motion law and state in two conditions are comparatively analyzed. Analysis results show that, in steel tube clamping stage the motion of the clip rod is of variable deceleration; And in rotating stage, mechanism is of accelerated rotation with variable acceleration when the cylinder input, while mechanism is of uniform rotation when the crank input； And then the cylinder is with positive and reverse swings throughout the movement process. The analysis results provide the basis for institution parameter selection and structure optimization design.
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Pun, C. M., i M. C. Lee. "Rotation-invariant texture classification using a two-stage wavelet packet feature approach". IEE Proceedings - Vision, Image, and Signal Processing 148, nr 6 (2001): 422. http://dx.doi.org/10.1049/ip-vis:20010705.
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Choi, Min-Seok, i Whoi-Yul Kim. "A novel two stage template matching method for rotation and illumination invariance". Pattern Recognition 35, nr 1 (styczeń 2002): 119–29. http://dx.doi.org/10.1016/s0031-3203(01)00025-5.
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Alekhnovich, V. I., M. Yu Chetvernin i A. F. Shirankov. "OPTICAL METHOD FOR MEASURING RUNOUT PARAMETERS AXIS OF THE PART RELATIVE TO THE AXIS OF ROTATION". Kontrol'. Diagnostika, nr 270 (grudzień 2020): 50–56. http://dx.doi.org/10.14489/td.2020.12.pp.050-056.
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The article is devoted to the development of an optical method and a device for measuring the runout parameters of a part relative to the axis of its rotation. A graphical diagram is provided to indicate and explain all the runout parameters of rotating part. It is shown that these parameters can be determined by the optical method using the visualization of the rotation axis and the inertia axis of the part by a collimated laser beam. The process of measuring these parameters consists of two stages. In the first stage, the inertia axis of the part is aligned with the axis of the laser beam, and in the second stage, the rotation axis of the part is aligned with the axis of the measuring camera. The measurement is based on determining the coordinates of the photoenergy center of the laser spot in the plane of the sensing array. The results of the scientific work are the developed optical method and the device based on a measuring camera, which allow to measure and reduce the runout parameters in a controlled manner, bringing them to acceptable limits by means of the known vectors of bearing adjustment movements.
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Bouchaud, K., A. Domiciano de Souza, M. Rieutord, D. R. Reese i P. Kervella. "A realistic two-dimensional model of Altair". Astronomy & Astrophysics 633 (styczeń 2020): A78. http://dx.doi.org/10.1051/0004-6361/201936830.
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Context. Fast rotation is responsible for important changes in the structure and evolution of stars and the way we see them. Optical long baseline interferometry now allows for the study of its effects on the stellar surface, mainly gravity darkening and flattening. Aims. We aim to determine the fundamental parameters of the fast-rotating star Altair, in particular its evolutionary stage (represented here by the core hydrogen mass fraction Xc), mass, and differential rotation, using state-of-the-art stellar interior and atmosphere models together with interferometric (ESO-VLTI), spectroscopic, and asteroseismic observations. Methods. We use ESTER two-dimensional stellar models to produce the relevant surface parameters needed to create intensity maps from atmosphere models. Interferometric and spectroscopic observables are computed from these intensity maps and several stellar parameters are then adjusted using the publicly available MCMC algorithm Emcee. Results. We determined Altair’s equatorial radius to be Req = 2.008 ± 0.006 R⊙, the position angle PA = 301.1 ± 0.3°, the inclination i = 50.7 ± 1.2°, and the equatorial angular velocity Ω = 0.74 ± 0.01 times the Keplerian angular velocity at equator. This angular velocity leads to a flattening of ε = 0.220 ± 0.003. We also deduce from the spectroscopically derived v sin i ≃ 243 km s−1, a true equatorial velocity of ∼314 km s−1 corresponding to a rotation period of 7h46m (∼3 cycles/day). The data also impose a strong correlation between mass, metallicity, hydrogen abundance, and core evolution. Thanks to asteroseismic data, and provided our frequencies identification is correct, we constrain the mass of Altair to 1.86 ± 0.03 M⊙ and further deduce its metallicity Z = 0.019 and its core hydrogen mass fraction Xc = 0.71, assuming an initial solar hydrogen mass fraction X = 0.739. These values suggest that Altair is a young star ∼100 Myr old. Finally, the 2D ESTER model also gives the internal differential rotation of Altair, showing that its core rotates approximately 50% faster than the envelope, while the surface differential rotation does not exceed 6%.
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Prokhorenko, A., S. Kravchenko i E. Solodky. "METHOD OF ORGANIZING TWO-STAGE FUEL INJECTION INTO A DIESEL CYLINDER USING A HYDROMECHANICAL FUEL EQUIPMENT". Internal Combustion Engines, nr 2 (15.11.2022): 25–32. http://dx.doi.org/10.20998/0419-8719.2022.2.04.
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The use of multiphase injection allows reducing the emission levels with exhaust gases and the noise of diesel engines. This paper proposes to improve the hydromechanical fuel supply system of diesel vehicles by providing the possibility of two-stage fuel supply. This task is solved by high-pressure fuel pump equipment, additionally by high-pressure sections that work to inject fuel for pilot injection. The drive shaft cams of these sections are ahead of the shaft cams of the main sections by 2-10 degrees rotation of the camshaft. In order to check the performance of the proposed two-stage fuel supply system and to confirm the possibility of achieving its stated parameters, calculation studies were performed based on mathematical modeling of hydromechanical processes in this system.
Calculation studies were carried out using a mathematical model of the high-pressure fuel system of the Ch12/14 research single-cylinder diesel engine. The mathematical model is implemented in the MATLAB programming environment. Test results of calculations according to this mathematical model for the operating mode of the system at a camshaft rotation frequency of 650 min-1 and full fuel supply, the high-pressure system provides two-stage injection with the following indicators: total cyclic fuel supply 64 mm3/cycle, pilot dose - 9 mm3/cycle (which is 16% of the total cyclical supply); the maximum injection pressure is 49 MPa with a maximum pressure of 58 MPa in the over-plunger cavity; the maximum injection pressure of the pilot dose is 14.7 MPa, while the pressure reached in the over-plunger cavity is 26.5 MPa; the duration of the injection of the pilot dose is about 2 degrees rotation of the camshaft, the main one - 4.7 degrees rotation of the camshaft.
The system also provides two-stage injection in modes according to the load (and speed) characteristics. When the load is reduced from the maximum by 35-40%, it does not affect the maximum injection pressure of the main part of the fuel at all speed modes of the system, after which there is a sharp drop of this parameter to the value of the maximum injection pressure of the pilot. The maximum injection pressure of the pilot dose practically does not depend on the speed mode and lies within 13.5-15 MPa. Since the amount of the pilot dose is not adjustable, it does not depend on the movement of the high-pressure fuel pump rail and is 2 mm3/cycle at a rotation frequency of 450 min-1, 6 mm3/cycle at a rotation frequency of 550 min-1 and 9 mm3/cycle at a rotation frequency of 650 min-1.
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Trilis, Artem. "Modeling Of Transverse Detonation Waves In A Flat-Radial Annular Channel". Siberian Journal of Physics 12, nr 2 (1.06.2017): 60–65. http://dx.doi.org/10.54362/1818-7919-2017-12-2-60-65.
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Acoustic properties of two regions of gases with different temperatures arising at the initial stage of evolution of transverse detonation waves in annular channel were examined. Mechanics of acoustic vibrations and waves are studied using both numeric and analytical and methods. Rotating circumferential waves at boundary surface of two gases with different temperatures were discovered and rotation velocities of these waves were determined.
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Ahn, Jaeyong, M. T. Schobeiri, Je-Chin Han i Hee-Koo Moon. "Film Cooling Effectiveness on the Leading Edge Region of a Rotating Turbine Blade With Two Rows of Film Cooling Holes Using Pressure Sensitive Paint". Journal of Heat Transfer 128, nr 9 (22.04.2006): 879–88. http://dx.doi.org/10.1115/1.2241945.
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Detailed film cooling effectiveness distributions are measured on the leading edge of a rotating gas turbine blade with two rows (pressure-side row and suction-side row from the stagnation line) of holes aligned to the radial axis using the pressure sensitive paint (PSP) technique. Film cooling effectiveness distributions are obtained by comparing the difference of the measured oxygen concentration distributions with air and nitrogen as film cooling gas respectively and by applying the mass transfer analogy. Measurements are conducted on the first-stage rotor blade of a three-stage axial turbine at 2400rpm (positive off-design), 2550rpm (design), and 3000rpm (negative off-design), respectively. The effect of three blowing ratios is also studied. The blade Reynolds number based on the axial chord length and the exit velocity is 200,000 and the total to exit pressure ratio was 1.12 for the first-stage rotor blade. The corresponding rotor blade inlet and outlet Mach numbers are 0.1 and 0.3, respectively. The film cooling effectiveness distributions are presented along with discussions on the influence of rotational speed (off design incidence angle), blowing ratio, and upstream nozzle wakes around the leading edge region. Results show that rotation has a significant impact on the leading edge film cooling distributions with the average film cooling effectiveness in the leading edge region decreasing with an increase in the rotational speed (negative incidence angle).
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Liao, Che-Wei, Ming-Tzu Tsai, Heng-Li Huang, Lih-Jyh Fuh, Yen-Lin Liu, Zhi-Teng Su i Jui-Ting Hsu. "Geometrical Calibration of a 2.5D Periapical Radiography System". Applied Sciences 10, nr 3 (30.01.2020): 906. http://dx.doi.org/10.3390/app10030906.
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The objective of this study was to develop a geometrical calibration method applicable to the 2.5D prototype Periapical Radiography System and estimate component position errors. A two-steel-ball phantom with a precisely known position was placed in front of a digital X-ray sensor for two-stage calibration. In the first stage, the following three parameters were estimated: (1) r, the distance between the focal spot and the rotation axis of the X-ray tube; (2) ψ, the included angle between the straight line formed by the X-ray tube’s focal spot and rotation axis and the straight line of the orthogonal sensor; and (3) L4, the distance between the rotation axis and the plane where the two steel balls were positioned. In the second stage, the steel balls’ positions were determined to calculate the positions of the X-ray tube on the x, y, and z axes. Computer simulation was used to verify the accuracy of the calibration method. The results indicate that for the calibration approach proposed in this study, the differences between the estimated errors and setting errors were smaller than 0.15% in the first and second stages, which is highly accurate, verifying its applicability to accurate calibration of the 2.5D Periapical Radiography System.
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Stoneham, E., L. Witt, Q. Paterson, L. Martin i B. Thoma. "P101: The development of entrustable professional activity reference cards to support the implementation of Competence by Design in emergency medicine". CJEM 21, S1 (maj 2019): S100. http://dx.doi.org/10.1017/cem.2019.292.
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Innovation Concept: Competence by Design (CBD) was implemented nationally for Emergency Medicine (EM) residents beginning training in 2018. One challenge is the need to introduce residents to Entrustable Professional Activities (EPAs) that are assessed across numerous clinical rotations. The Royal College's resources detail these requirements, but do not map them to specific rotations or present them in a succinct format. This is problematic as trainees are less likely to succeed when expectations are unclear. We identified a need to create practical resources that residents can use at the bedside. Methods: We followed an intervention mapping framework to design two practical, user-friendly, low-cost, aesthetically pleasing resources that could be used by residents and observers at the bedside to facilitate competency-based assessment. Curriculum, Tool or Material: First, we designed a set of rotation- and stage-specific EPA reference cards for the use of residents and observers at the bedside. These cards list EPAs and clinical presentations likely to be encountered during various stages of training and on certain rotations. Second, we developed a curriculum board to organize the EPA reference cards by stage based upon our program's curriculum map. The curriculum board allows residents to view the program's curriculum map and the EPAs associated with each clinical rotation at a glance. It also contains hooks to hang and store extra cards in an organized manner. Conclusion: We believe that these practical and inexpensive tools facilitated our residency program's transition to competency-based EPA assessments. Anecdotally, the residents are using the cards and completing the suggested rotation-specific EPAs. We hope that the reference cards and curriculum board will be successfully incorporated into other residency programs to facilitate the introduction of their EPA-based CBD assessment system.
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Beck, P. G., T. Kallinger, K. Pavlovski, A. Palacios, A. Tkachenko, S. Mathis, R. A. García i in. "Seismic probing of the first dredge-up event through the eccentric red-giant and red-giant spectroscopic binary KIC 9163796". Astronomy & Astrophysics 612 (kwiecień 2018): A22. http://dx.doi.org/10.1051/0004-6361/201731269.
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Context. Binaries in double-lined spectroscopic systems (SB2) provide a homogeneous set of stars. Differences of parameters, such as age or initial conditions, which otherwise would have strong impact on the stellar evolution, can be neglected. The observed differences are determined by the difference in stellar mass between the two components. The mass ratio can be determined with much higher accuracy than the actual stellar mass. Aim. In this work, we aim to study the eccentric binary system KIC 9163796, whose two components are very close in mass and both are low-luminosity red-giant stars. Methods. We analysed four years of Kepler space photometry and we obtained high-resolution spectroscopy with the Hermes instrument. The orbital elements and the spectra of both components were determined using spectral disentangling methods. The effective temperatures, and metallicities were extracted from disentangled spectra of the two stars. Mass and radius of the primary were determined through asteroseismology. The surface rotation period of the primary is determined from the Kepler light curve. From representative theoretical models of the star, we derived the internal rotational gradient, while for a grid of models, the measured lithium abundance is compared with theoretical predictions. Results. From seismology the primary of KIC 9163796 is a star of 1.39 ± 0.06M⊙, while the spectroscopic mass ratio between both components can be determined with much higher precision by spectral disentangling to be 1.015 ± 0.005. With such mass and a difference in effective temperature of 600 K from spectroscopy, the secondary and primary are, respectively, in the early and advanced stage of the first dredge-up event on the red-giant branch. The period of the primary’s surface rotation resembles the orbital period within ten days. The radial rotational gradient between the surface and core in KIC 9163796 is found to be 6.9−1.0+2.0. This is a low value but not exceptional if compared to the sample of typical single field stars. The seismic average of the envelope’s rotation agrees with the surface rotation rate. The lithium’abundance is in agreement with quasi rigidly rotating models. Conclusions. The agreement between the surface rotation with the seismic result indicates that the full convective envelope is rotating quasi-rigidly. The models of the lithium abundance are compatible with a rigid rotation in the radiative zone during the main sequence. Because of the many constraints offered by oscillating stars in binary systems, such objects are important test beds of stellar evolution.
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Luo, Tianyin, Hideyuki Umeda, Takashi Yoshida i Koh Takahashi. "Stellar Models of Betelgeuse Constrained Using Observed Surface Conditions". Astrophysical Journal 927, nr 1 (1.03.2022): 115. http://dx.doi.org/10.3847/1538-4357/ac4f5f.
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Abstract We study stellar models for Betelgeuse using the HR diagram and surface abundances as observational constraints. Previous studies on Betelgeuse have not systematically investigated the surface abundances, but we believe they can be impacted by, and thus be used as an observational constraint for various parameters such as initial mass, rotation, and overshoot scheme. We investigate stellar models with varying initial mass as they evolve past the main sequence, and we examine the red supergiant (RSG) properties in detail. For each mass, we vary the initial rotation up to ∼300 km s−1, and test two different overshoot parameters. Overall, the acceptable initial mass range is 12–25 M ⊙, but for nonrotating models only, the range is decreased to 15–24 M ⊙. Also for rotating models, we find that v/v K = 0.3 is the upper limit for initial rotation, as more rapidly rotating models are unable to fit to Betelgeuse’s surface abundances as an RSG. In addition, we report two possibilities for the current stage of evolution, core helium burning or core carbon burning and beyond. We find that certain 17 M ⊙ models could fit both stages. Finally, we discuss the implications of our results in the context of merger scenarios which have been suggested as a mechanism to attain the observed surface velocity of Betelgeuse.
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Xu, Weihe, Kenneth Lauer, Yong Chu i Evgeny Nazaretski. "A high-precision instrument for mapping of rotational errors in rotary stages". Journal of Synchrotron Radiation 21, nr 6 (2.10.2014): 1367–69. http://dx.doi.org/10.1107/s160057751401618x.
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A rotational stage is a key component of every X-ray instrument capable of providing tomographic or diffraction measurements. To perform accurate three-dimensional reconstructions, runout errors due to imperfect rotation (e.g.circle of confusion) must be quantified and corrected. A dedicated instrument capable of full characterization and circle of confusion mapping in rotary stages down to the sub-10 nm level has been developed. A high-stability design, with an array of five capacitive sensors, allows simultaneous measurements of wobble, radial and axial displacements. The developed instrument has been used for characterization of two mechanical stages which are part of an X-ray microscope.
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Sharma, P. B., Y. P. Jain i D. S. Pundhir. "A Study of Some Factors Affecting the Performance of a Contra-Rotating Axial Compressor Stage". Proceedings of the Institution of Mechanical Engineers, Part A: Power and Process Engineering 202, nr 1 (luty 1988): 15–21. http://dx.doi.org/10.1243/pime_proc_1988_202_003_02.
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An experimental investigation of the performance of a contra-rotating stage is reported. The influence of factors such as speed ratio of the two rotors, rotor stagger, pitch-chord ratio and axial spacing between the rotors is examined from tests on a 0.66 hub-tip ratio compressor. The study reveals that the performance of a contra-rotating stage is affected by all these factors. Axial spacing between the rotors and the speed ratio of the rotors both exhibit a strong influence on the stalling behaviour of the stage. It has been found that in a stage with close axial gap, rotating stall on the first rotor is suppressed if the second rotor is contra-rotated at a speed 50 per cent faster than the first rotor. This unique advantage of contra-rotation is not obtained if the axial gap is large. Measurements of sound pressure level are also reported to highlight the high noise problems associated with a contra-rotating stage.
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Hazel, Soufyane, Yong Huang i Mokhtar Ait Amirat. "New single vortex generation method for flame/vortex interaction using flow behind a rotating cylinder". Fluid Dynamics Research 53, nr 6 (1.12.2021): 065506. http://dx.doi.org/10.1088/1873-7005/ac4385.
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Abstract This paper investigates a new experimental method to generate a single two-dimensional translated vortex for flame/vortex interaction studies. A rotating cylinder is immersed in a uniform flow and, its rotating speed is impulsively reduced. This sudden action triggers the generation of a single vortex when both the initial and the final rotation speeds are in the range of a steady-state regime. Flow visualization allows confirming the applicability of this method, while a complementary two-dimensional numerical simulation is conducted to understand the vortex formation process. A vorticity layer is detached from the cylinder, initiating a feeding process and gradual growth of a single leading vortex. The feeding process is saturated at a specific distance from the cylinder and, vortex separation from the vorticity layer is observed. At the final stage of the formation process, the generated vortex is advected away and, a steady-state regime is again established behind the cylinder. The vortex characteristics appear to be related to the normalized reduction in the rotation rate Δ α , defined as the initial and final rotation rates difference normalized by the initial rotation rate. Several combinations of initial and final rotation rates corresponding to different normalized reductions are investigated experimentally and numerically. The results allow understanding the effect of this parameter; a higher normalized reduction generates a stronger, more rapidly growing vortex. However, its trajectory is related to the wake deviation corresponding to the final rotation rate.
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Герасимов, М., M. Gerasimov, Н. Воробьев, N. Vorob'ev, В. Иванов i V. Ivanov. "OPTIMIZATION OF PARAMETERS OF TWO-STAGE VIBRATION MECHANISM WITH ASYMMETRIC OSCILLATIONS BY DYNAMIC COEFFICIENT". Bulletin of Belgorod State Technological University named after. V. G. Shukhov 4, nr 10 (7.11.2019): 149–53. http://dx.doi.org/10.34031/article_5db3fdb0e8c532.45857437.
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The mechanisms with asymmetric vibrations is the priority direction of development and creation of vibration devices for technological processes in the coming years. Mechanisms with asymmetric vibrations are constructively created on the basis of vibrators with directional vibrations in the form of steps, which differ from each other in the mass of unbalances, the radius of displacement of the center of mass from the axis of rotation and the frequency of rotation of the unbalanced shaft. The simplest device with asymmetric oscillations is a two-stage mechanism. Optimization of parameters of vibrators of each stage can be carried out according to the coefficient of dynamism of the oscillatory system. Rational parameters of the mechanism are consistent with the highest value of the coefficient of dynamism of the system. Currently, there is no method of design calculation for the translation of circular, elliptical and equally directed oscillations into asymmetric ones. The article presents the method of calculation associated with the translation of the parameters of vibration devices with circular, elliptical and equally directed vibrations into asymmetric ones with the highest coefficient of dynamism.
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Исмагилов, Динар, Dinar Ismagilov, Марат Калимуллин, Marat Kalimullin, Ринат Абдрахманов, Rinat Abdrakhmanov, Ильдар Валиев i Il'dar Valiev. "EXPERIMENTAL STUDIES OF A TWO-GRADE CHOPPER OF BEETS". Vestnik of Kazan State Agrarian University 14, nr 2 (29.07.2019): 100–105. http://dx.doi.org/10.12737/article_5d3e174cf21866.69997219.
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The two-grade rotary chopper BIR-2 of root and tuber crops with flexible working elements is designed to remove the beets of vegetable leaves before or during the harvest of carrots. It is proposed to use it together with an undermining machine in an aggregate with a tractor of the 1.4 kN class of thrust with a front and rear hitch. In this case, the chopper of beets is hung on the front hitch of the power means, and the working units are driven in rotation by hydraulic motors, which allows the two unitized devices to operate independently of each other. Laboratory studies of the effect of rotational speed, type and diameter of the cross section of work items on the amplitude of their oscillations were carried out on the soil plots Kazan State Agrarian University. Several types of work items were used in the experiments: a rubberized metal cable, a rubber-fabric element, a fishing line. The approbation was carried out when removing the tops of carrots. At this stage of experimental studies, the rotational speed of the working unit was 700 min-1, and the onward speed was 2.5 m/sec. Later, for the experiments, the plasticine pins were made, using which, with the necessary accuracy, the lower and upper points of contact of the working element can be determined, which, in turn, makes it possible to calculate the amplitude of transverse oscillations as the difference between these points. The rotational speed of the working elements at this stage varied from 500 to 900 min-1, the cross-sectional diameter - from 5 to 7 mm. According to the test results, the most rational diameter of the working element, which is equal to 5.5 mm, was determined, the required cutting height of the carrot tops in accordance with agrotechnical requirements, which is 0 ... 20 mm at a frequency of rotation of the working elements 800 min-1. According to the testing results of the developed unit under production conditions, which were carried out in JSC “Kyrlay” of the Republic of Tatarstan, the rational speed of the unit movement was chosen, which amounted to 3.3 m/sec.
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Choi, Kee-Bong, Jaejong Lee, Geehong Kim, Hyungjun Lim i Soongeun Kwon. "Kinematic Analysis of a Parallel Manipulator Driven by Perpendicular Linear Actuators". Actuators 10, nr 10 (9.10.2021): 262. http://dx.doi.org/10.3390/act10100262.
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In this paper, a goniometer-type specimen stage with a linear actuation mechanism mounted on a rotation mechanism is introduced. The linear actuation mechanism was modeled as a spatial parallel manipulator consisting of a moving body, three linear actuators, and an anti-rotation mechanism. The three linear actuators were arranged perpendicular to each other. In the specimen stage, the linear actuators were in ball contact with the surface of a holder designed to hold a specimen. For the parallel manipulator, the ball contact was replaced with two prismatic joints and a spherical joint. The mobility of the manipulator without the anti-rotation mechanism was one degree of freedom greater than the number of actuators. Therefore, the redundant one degree-of-freedom motion was restrained using an anti-rotation mechanism with three rotation joints and two prismatic joints. The inverse and direct kinematics of the goniometer mechanism were derived and verified. In addition, the inverse Jacobian was derived, and local and global performance indices were analyzed by the terms of manipulability and isotropy. Finally, the goniometer-type specimen stage was designed by the global performance indices.
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Smith, Robert Connon. "The Evolution of Rapidly Rotating B Stars (Review Paper)". International Astronomical Union Colloquium 92 (sierpień 1987): 486–99. http://dx.doi.org/10.1017/s0252921100116665.
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AbstractBe stars are located in or near the main-sequence band for non-rotating stars. Although this stage of evolution is relatively well understood, there are two main effects that make it impossible to say whether all Be stars are in the same stage of evolution and, if so, what that stage is. One effect is the spread in observed magnitude and colour as a result of rotation. Correction for rotation is not possible because of the unknown inclination of any particular star's rotation axis to the line of sight and because it is not clear what the internal angular momentum distribution is or how it changes as a result of evolution. The other effect is that there are uncertainties in the theoretical evolutionary tracks because the amount of convective overshooting is unclear. Other mixing mechanisms that might in principle also confuse the tracks seem to be small near the main sequence. If Be stars are related to the β Cephei and 53 Persei stars in the same part of the HR diagram, then the non-radial pulsation properties of Be stars may give a clue to their evolutionary state. The existence of a circumstellar disc or ring, however, tells us very little about the evolutionary stage of the underlying star. A useful way forward may be to try to understand individual stars in as much detail as possible.
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Lou, Zhi-Feng, Xiu-Peng Hao, Yin-Di Cai, Tien-Fu Lu, Xiao-Dong Wang i Kuang-Chao Fan. "An Embedded Sensor System for Real-Time Detecting 5-DOF Error Motions of Rotary Stages". Sensors 19, nr 13 (27.06.2019): 2855. http://dx.doi.org/10.3390/s19132855.
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The geometric error motions of rotary stages greatly affect the accuracy of constructed machines such as machine tools, measuring instruments, and robots. In this paper, an embedded sensor system for real-time measurement of two radial and three angular error motions of a rotary stage is proposed, which makes use of a rotary encoder with multiple scanning heads to measure the rotational angle and two radial error motions and a miniature autocollimator to measure two tilt angular errors of the axis of rotation. The assembly errors of the grid disc of the encoder and the mirror for autocollimator are also evaluated and compensated. The developed measuring device can be fixed inside the rotary stage. In the experiments, radial error motions of two points on the axis (h = 5 mm and 60 mm) were measured and calibrated with LVDTs, and the data showed that the radial error motions of the axis were less than 20 μm, and the calibration residual errors were less than 2 μm. When intermittent external forces were applied to the stage, the change of the stage’s error motion could also be monitored accurately.
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Livernois, Alexander, Enrico Vesperini, Maria Tiongco, Anna Lisa Varri i Emanuele Dalessandro. "Early dynamics and violent relaxation of multimass rotating star clusters". Monthly Notices of the Royal Astronomical Society 506, nr 4 (26.07.2021): 5781–801. http://dx.doi.org/10.1093/mnras/stab2119.
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ABSTRACT We present the results of a study aimed at exploring, by means of N-body simulations, the evolution of rotating multimass star clusters during the violent relaxation phase, in the presence of a weak external tidal field. We study the implications of the initial rotation and the presence of a mass spectrum for the violent relaxation dynamics and the final properties of the equilibria emerging at the end of this stage. Our simulations show a clear manifestation of the evolution towards spatial mass segregation and evolution towards energy equipartition during and at the end of the violent relaxation phase. We study the final rotational kinematics and show that massive stars tend to rotate more rapidly than low-mass stars around the axis of cluster rotation. Our analysis also reveals that during the violent relaxation phase, massive stars tend to preferentially segregate into orbits with angular momentum aligned with the cluster’s angular momentum, an effect previously found in the context of the long-term evolution of star clusters driven by two-body relaxation.
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Yu, Bo, Xiaonan Liang, Ying Wang, Yun Liu, Qiao Chang, Linlin Wang i Tingting Zhao. "The Determination of Sample Size for Sensitive Issue Successive Survey with the Multiplication RRT Model under Two-Stage and Stratified Two-Stage Random Sampling and Its Application in Medical Survey". Mathematical Problems in Engineering 2019 (25.03.2019): 1–10. http://dx.doi.org/10.1155/2019/1979616.
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When designing the sample scheme, it is important to determine the sample size. The survey accuracy and cost of survey and sampling method should be considered comprehensively. In this article, we discuss the method of determining the sample size of complex successive sampling with rotation sample for sensitive issue and deduce the formulas for the optimal sample size under two-stage sampling and stratified two-stage sampling by using Cauchy-Schwartz inequality, respectively, so as to minimize the cost for given sampling errors and to minimize the sampling errors for given cost.
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Ebus, Tobias, Markus Dietz i Andreas Hupfer. "Experimental and numerical studies on small contra-rotating electrical ducted fan engines". CEAS Aeronautical Journal 12, nr 3 (29.05.2021): 559–71. http://dx.doi.org/10.1007/s13272-021-00517-7.
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AbstractElectrical propulsion has been identified as one of the key fields of future research within the aerospace sector. The Institute of Aeronautical Engineering at the Universität der Bundeswehr München aims to contribute to the ongoing development of small-sized electrical ducted fan engines with a thrust in the range of 100 N. A special emphasis is placed on electrically powered contra-rotating fan stages. When compared to a conventional rotor–stator stage, contra-rotating fan stages allow for a more compact design, considering a given pressure ratio, or an increased pressure ratio at a constant fan diameter. Since numerous new aircraft concepts are presently being developed, a high demand for compact and powerful electrically driven engines arises. Electrically driven contra-rotating fan engines provide a high potential in terms of compactness, emissions and efficiency. Using electric motors offers the ability to overcome common issues, such as design and integration of a contra-rotating stage into a gas turbine. An innovative new engine design featuring such a contra-rotating stage is developed and tested at one of the Institute’s test benches for electrical propulsion. Key components are two brushless motors powering the fan stage, one for each rotor. Various operation points are investigated experimentally during an extensive test campaign. Experimental results are compared to results of numerical simulations computed by ANSYS CFX. Results indicate a good agreement between experiment and simulation. The engine is running very smooth throughout all tested operation points. Yet, intensive heating up of the electric motors and high-temperature zone are found to be an issue at higher rotation speeds.
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Prokudin, A. N., i S. V. Firsov. "Elastoplastic deformation of a rotating hollow cylinder with a rigid casing". PNRPU Mechanics Bulletin, nr 4 (15.12.2019): 120–35. http://dx.doi.org/10.15593/perm.mech/2019.4.12.
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A rotating hollow cylinder with fixed ends is considered, the inner surface of which is free of stresses, and the outer one is fixed from radial movements. It is assumed that the cylinder is made of an ideal isotropic elastoplastic material, and the deformations in it are small and represent the sum of elastic and plastic deformations. Stresses are associated with elastic deformations by Hooke's law. Plastic deformations are determined using the Tresca - Saint-Venant condition and the plastic flow rule associated with it. The cylinder rotation speed first monotonically increases to a maximum value, and then decreases to zero. By using the elastic solution, the dependence is found for the critical rotation speed at which the plastic flow begins. It is established that, depending on the thickness of the cylinder and the Poisson's ratio, plastic flow can begin, either on the inner or on the outer surface of the cylinder. In addition, 3 plastic regions appear in the cylinder at the loading stage, and 4 plastic regions appear at the unloading stage. These regions correspond to two faces and two edges of the Treska prism. For each plastic region, an exact analytical solution of the determining system of equations is found. The system of conditions at the boundaries between the regions providing continuity of the obtained solutions throughout the cylinder is given. Two cases are considered, i.e. the case with a plastic flow which starts first on the inner, and then on the outer surface of the cylinder. Analytical expressions are obtained for rotational speeds at which new regions appear. The relationship between the nucleation rates of the secondary and primary plastic flow is established. The value of the maximum rotation speed sufficient for a complete transition of the cylinder to the state of the secondary plastic flow was also found. It has been revealed that the adding of a rigid casing can significantly increase the resource of an exploited part.
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Dengwei Fu i A. N. Willson. "A two-stage angle-rotation architecture and its error analysis for efficient digital mixer implementation". IEEE Transactions on Circuits and Systems I: Regular Papers 53, nr 3 (marzec 2006): 604–14. http://dx.doi.org/10.1109/tcsi.2005.859056.
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Tevelev, A. V., A. A. Borisenko, M. I. Erokhina, S. S. Popov, I. A. Kosheleva i Yu A. Gatovsky. "Signs of polichnous deformations in microstructures of carbonate rocks of the Katav-Yuryuzan zone of transpression (Southern Urals)". Moscow University Bulletin. Series 4. Geology, nr 4 (28.08.2020): 13–21. http://dx.doi.org/10.33623/0579-9406-2020-4-13-21.
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The Katav-Ivanovsk transpression zone experienced at least two stages of tectonic deformations, and the sequence of deformations was approximately the same throughout the entire zone — from the Bakal-Satka fault in the south to the Suleimsky fault in the north. Three stages of the formation of parageneses were identified. The parageneses of the first and the second stages were formed in a pure shear environment, and the paragenesis of the third stage — in a simple shear environment. There are stylolites (S1) parallel to bedding, and mineral veins (V1) in the paragenesis of the first stage. Paragenesis of the second stage combines stylolites (S2), mineral veins (V2) and intergranular cleavage (S2). In paragenesis of the third stage were distinguished schistosity (S3), milonites (S3), cataclasites, mica packets (SC-textures), and the rotation structures of porphyroblasts.
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Pattabirani, G., i K. Selvakumar. "Implementation of Energy HEED (ER-HEED) Protocol Using Super Cluster Head for WSN". Asian Journal of Computer Science and Technology 7, S1 (5.11.2018): 119–22. http://dx.doi.org/10.51983/ajcst-2018.7.s1.1790.
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Wireless Sensor Network (WSN) is used in almost all applications in developing environment. This is due to their ability and easy implementation through several applications. The most important criteria in WSN are to minimize the energy consumption and improve the network lifetime. Clustering algorithms are considered as one of the effective way to improve the network lifetime in WSN. Hybrid, Energy-Efficient and Distributed (HEED) clustering approach uses energy-efficient clustering algorithm. This paper proposes an Enhanced Rotational HEED (ER-HEED) protocol using super cluster head for minimizing energy consumption and to improve the network lifetime. The proposed work is carried out in two stages, first stage, super cluster head is introduced. In second stage, the node with maximum threshold is chosen as a cluster head on rotation within in the cluster. The results show that the ER-HEED performs well when compared with HEED and LEACH.
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Johnson, Deepika Roselind, i Rhymend Uthariaraj Vaidhyanathan. "Detection and localization of multi-scale and oriented objects using an enhanced feature refinement algorithm". Mathematical Biosciences and Engineering 20, nr 8 (2023): 15219–43. http://dx.doi.org/10.3934/mbe.2023681.
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<abstract><p>Object detection is a fundamental aspect of computer vision, with numerous generic object detectors proposed by various researchers. The proposed work presents a novel single-stage rotation detector that can detect oriented and multi-scale objects accurately from diverse scenarios. This detector addresses the challenges faced by current rotation detectors, such as the detection of arbitrary orientations, objects that are densely arranged, and the issue of loss discontinuity. First, the detector also adopts a progressive regression form (coarse-to-fine-grained approach) that uses both horizontal anchors (speed and higher recall) and rotating anchors (oriented objects) in cluttered backgrounds. Second, the proposed detector includes a feature refinement module that helps minimize the problems related to feature angulation and reduces the number of bounding boxes generated. Finally, to address the issue of loss discontinuity, the proposed detector utilizes a newly formulated adjustable loss function that can be extended to both single-stage and two-stage detectors. The proposed detector shows outstanding performance on benchmark datasets and significantly outperforms other state-of-the-art methods in terms of speed and accuracy.</p></abstract>
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Dong, Qingming, i Amalendu Sau. "Unsteady electrorotation of a viscous drop in a uniform electric field". Physics of Fluids 35, nr 4 (kwiecień 2023): 047116. http://dx.doi.org/10.1063/5.0140845.
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A dielectric drop suspended in an immiscible dielectric fluid of higher conductivity can spontaneously generate the so-called Quincke rotation (a rotating activity that a weakly conducting drop/solid particle displays in an electric field) subjected to sufficiently strong electric field strength. The steady tilt has been extensively studied and is well elucidated now. However, the unsteady electrorotation of drop remains a largely unclear, complex issue. Motivated by this, we examine the unsteady drop electrorotation in this work with the required integrated convective bulk charge transport effect. First, for the steady rotation, the transient evolution to a steady droplet tilt from the symmetric Taylor state is analyzed in-depth. Here we discover several new phenomena, including the evolving equatorial charge jets. For unsteady rotation, based on a drop's interfacial charge variation, deformation, and tilt angle, the study reports the growth of three distinct rotating patterns in the viscosity ratio range [Formula: see text] and electric field strength [Formula: see text] at a fixed conductivity ratio Q ( = [Formula: see text]) = 0.026 and permittivity ratio S (=[Formula: see text]) = 0.566. A low-viscosity drop ([Formula: see text]) exhibits only the periodic rotation. For the viscosity ratio [Formula: see text], the increased electric intensity creates two new unsteady rotation modes: the pseudo-periodic tumbling and the irregular one. For [Formula: see text], the periodic mode remains absent; instead, the drop displays the electric intensity-dependent tumbling and irregular rotation patterns. Our study shows that the rotation reduces a drop's transitory interfacial charge. At this stage, the drop rotation behavior is controlled by competing charge convection due to fluid flow and charge supply by conduction. The resulting varying electric Reynolds number [Formula: see text] (the time ratio of charge relaxation and charge convection) explains the created different rotation mechanisms. For [Formula: see text], owing to lacking enough interfacial charge to sustain rotation, the drop's transition to a temporary non-rotating Taylor state occurs until the interface recharges. The resultant mechanism supports the periodic batch-type rotation for a low-viscosity drop and the irregular rotation for a high-viscosity drop in a higher electric field. In contrast, for [Formula: see text], the drop timely acquires sufficient charge to support continuous tumbling electrorotation.
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Rodríguez-Martín, J. E., A. García Hernández, J. C. Suárez i J. R. Rodón. "Study of the low-order Δν–ρ¯ relation for moderately rotating δ Scuti stars and its impact on their characterization". Monthly Notices of the Royal Astronomical Society 498, nr 2 (26.08.2020): 1700–1709. http://dx.doi.org/10.1093/mnras/staa2378.
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ABSTRACT The large separation in the low-radial order regime is considered as a highly valuable observable to derive mean densities of δ Scuti stars, due to its independence with rotation. Up to now, theoretical studies of this Δν–${\bar{\rho}}$ relation have been limited to 1D non-rotating models and 2D pseudo-evolutionary models. The present work aims at completing this scenario by investigating quantitatively the impact of rotation in this relation on a large grid of 1D asteroseismic models representative of δ Scuti stars. These include rotation effects on both the stellar evolution and the interaction with pulsation. This allowed us to compute the stellar deformation, get the polar and equatorial radii, and correct the stellar mean densities. We found that the new Δν–${\bar{\rho}}$ relation for rotating models is compatible with previous works. We explained the dispersion of the points around the linear fits as caused mainly by the distribution of the stellar mass, and partially by the evolutionary stage. The new fit is found to be close to the previous theoretical studies for lower masses ($1.3\!-\!1.81\, \mathrm{M}_{\odot }$). However, the opposite holds for the observations: For the higher masses ($1.81\!-\!3\, \mathrm{M}_{\odot }$), the fit is more compatible with the empirical relation. To avoid such discrepancies, we provided new limits to the fit that encompass any possible dependence on mass. We applied these results to characterize the two well-known δ Scuti stars observed by CoRoT, HD 174936 and HD 174966, and compared the physical parameters with those of previous works. The inclusion of rotation in the modelling causes a tendency towards greater masses, radii, and luminosities, and lower density values. Comparison between Δν and Gaia’s luminosities also allowed us to constrain the inclination angles and rotational velocities of both stars. The present results pave the way to systematically constrain the angle of inclination (and thereby the actual surface rotation velocity) of δ Scuti stars.
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Takehiro, Shin, Michio Yamada i Yoshi-Yuki Hayashi. "Energy Accumulation in Easterly Circumpolar Jets Generated by Two-Dimensional Barotropic Decaying Turbulence on a Rapidly Rotating Sphere". Journal of the Atmospheric Sciences 64, nr 11 (1.11.2007): 4084–97. http://dx.doi.org/10.1175/2006jas2154.1.
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Abstract A series of numerical experiments on two-dimensional decaying turbulence is performed for a barotropic fluid on a rotating sphere. Numerical calculations have confirmed two important asymptotic features: emergence of the banded structure of zonal flows and their extreme latitudinal inhomogeneities in which kinetic energy is accumulated into the easterly circumpolar jets. The banded structure of zonal flows is established relatively early on in the initial stage. Later, after extended periods of time integration, only the circumpolar jets are intensified gradually, while there is no further evolution in the banded structure in the low and midlatitudes. Wave activity flux analysis illustrates that the initial vortices in the low and midlatitudes propagate poleward as Rossby waves and converge to produce easterly circumpolar flows. In association with this convergence, accumulation of the mean zonal component of kinetic energy proceeds. The tendency for the accumulation becomes strong as the rotation rate is increased, and nearly all of the kinetic energy is concentrated to the circumpolar flows in cases of rapid rotation. A theoretical model is constructed under the assumption that a circumpolar jet emerges around the latitude where the local Rhines scale is equal to the distance from the Pole, and that initial vortices at the lower latitudes contribute to the generation of the jets. The model describes the mean zonal component of kinetic energy and the averaged speed and width of the circumpolar jets as functions of the rotation rate, which agree satisfactorily with the numerical results.
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Pandis, Nikolaos, Theodore Eliades, Samira Partowi i Christoph Bourauel. "Moments Generated during Simulated Rotational Correction with Self-Ligating and Conventional Brackets". Angle Orthodontist 78, nr 6 (1.11.2008): 1030–34. http://dx.doi.org/10.2319/110307-516.1.
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Abstract Objective: To assess comparatively the magnitude of moments generated during rotational correction from different bracket systems during the late leveling and alignment stage of orthodontic treatment. Materials and Methods: The three types of brackets assessed were Orthos2 (ORMCO, Glendora, CA), Damon2 (ORMCO), and In Ovation-R (GAC, Bohemia, NY). The brackets were bonded on replicas made of resin from models constructed from an aligned patient's mandibular arch, and a 0.014- × 0.025-inch CuNiTi (ORMCO) wire was inserted. Orthodontic rotational correction was simulated on the Orthodontic Measurement and Simulation System from −5° to +5° rotation in 0.25° increments on the distal and mesial direction. The moments generated at each increment of rotation throughout the full rotation path were statistically analyzed using a two-way analysis of variance and Tukey test at the .05 level of significance. Results: Both bracket type and direction of rotation showed an effect on moment magnitude. The highest moment (27.2 Nmm) was observed for the Damon2 bracket assigned to its noncompliant slot wall door. Higher moments were found during distal premolar rotation. The In Ovation-R showed a magnitude of moment in the range of 9.0 Nmm in the same direction, whereas conventional brackets presented the lowest moments (5.0 Nmm). Conclusions: A wide variation in magnitude of moments exerted by self-ligating and conventional brackets is noted in the simulated rotational correction of teeth, which relates to the geometry of the dental arch, the tooth position, and the rigidity of the closing component of the bracket slot.
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Song, H. F., G. Meynet, A. Maeder, S. Ekström, P. Eggenberger, C. Georgy, Y. Qin i in. "Close binary evolution". Astronomy & Astrophysics 609 (22.12.2017): A3. http://dx.doi.org/10.1051/0004-6361/201731073.
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Context. Massive stars with solar metallicity lose important amounts of rotational angular momentum through their winds. When a magnetic field is present at the surface of a star, efficient angular momentum losses can still be achieved even when the mass-loss rate is very modest, at lower metallicities, or for lower-initial-mass stars. In a close binary system, the effect of wind magnetic braking also interacts with the influence of tides, resulting in a complex evolution of rotation. Aims. We study the interactions between the process of wind magnetic braking and tides in close binary systems. Methods. We discuss the evolution of a 10 M⊙ star in a close binary system with a 7 M⊙ companion using the Geneva stellar evolution code. The initial orbital period is 1.2 days. The 10 M⊙ star has a surface magnetic field of 1 kG. Various initial rotations are considered. We use two different approaches for the internal angular momentum transport. In one of them, angular momentum is transported by shear and meridional currents. In the other, a strong internal magnetic field imposes nearly perfect solid-body rotation. The evolution of the primary is computed until the first mass-transfer episode occurs. The cases of different values for the magnetic fields and for various orbital periods and mass ratios are briefly discussed. Results. We show that, independently of the initial rotation rate of the primary and the efficiency of the internal angular momentum transport, the surface rotation of the primary will converge, in a time that is short with respect to the main-sequence lifetime, towards a slowly evolving velocity that is different from the synchronization velocity. This “equilibrium angular velocity” is always inferior to the angular orbital velocity. In a given close binary system at this equilibrium stage, the difference between the spin and the orbital angular velocities becomes larger when the mass losses and/or the surface magnetic field increase. The treatment of the internal angular momentum transport has a strong impact on the evolutionary tracks in the Hertzsprung-Russell Diagram as well as on the changes of the surface abundances resulting from rotational mixing. Our modelling suggests that the presence of an undetected close companion might explain rapidly rotating stars with strong surface magnetic fields, having ages well above the magnetic braking timescale. Our models predict that the rotation of most stars of this type increases as a function of time, except for a first initial phase in spin-down systems. The measure of their surface abundances, together, when possible, with their mass-luminosity ratio, provide interesting constraints on the transport efficiencies of angular momentum and chemical species. Conclusions. Close binaries, when studied at phases predating any mass transfer, are key objects to probe the physics of rotation and magnetic fields in stars.
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Qian, Wen, Xue Yang, Silong Peng, Junchi Yan i Yue Guo. "Learning Modulated Loss for Rotated Object Detection". Proceedings of the AAAI Conference on Artificial Intelligence 35, nr 3 (18.05.2021): 2458–66. http://dx.doi.org/10.1609/aaai.v35i3.16347.
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Popular rotated detection methods usually use five parameters (coordinates of the central point, width, height, and rotation angle) or eight parameters (coordinates of four vertices) to describe the rotated bounding box and l1 loss as the loss function. In this paper, we argue that the aforementioned integration can cause training instability and performance degeneration. The main reason is the discontinuity of loss which is caused by the contradiction between the definition of the rotated bounding box and the loss function. We refer to the above issues as rotation sensitivity error (RSE) and propose a modulated rotation loss to dismiss the discontinuity of loss. The modulated rotation loss can achieve consistent improvement on the five parameter methods and the eight parameter methods. Experimental results using one stage and two stages detectors demonstrate the effectiveness of our loss. The integrated network achieves competitive performances on several benchmarks including DOTA and UCAS AOD. The code is available at https://github.com/yangxue0827/RotationDetection.
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Bouvier, J. "The Rotational History of Solar-Type Stars: Does It Affect Lithium Abundances?" Highlights of Astronomy 10 (1995): 445–46. http://dx.doi.org/10.1017/s1539299600011679.
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Recent studies of lithium abundances in solar-type stars suggest that second order effects, such as rotation and/or mass-loss, might affect the rate at which lithium is depleted at the surface of cool stars. This conclusion mainly stems from the dispersion of lithium abundances observed in late-type stars with otherwise similar mass and age. The dispersion of lithium abundances is relatively small in pre-main sequence (PMS) stars [1], reaches a maximum of about 2 dex in ZAMS stars (Soderblom, this volume), and decreases later during main sequence evolution, although significant dispersion may still be present by the age of the Sun [2], and perhaps even during the giant stage (Balachandran, this volume).Such a pattern of lithium dispersion is difficult to understand in the framework of conventional models in which lithium burning occurs at the base of the convective zone of non-rotating, non-mass losing stars. That two stars of the same age and mass can exhibit different lithium content strongly suggests that other, so far neglected, mechanisms play a role in lithium depletion.In this context, it may be relevant to stress that the pattern of lithium dispersion varies with age in much a similar way than does the dispersion of stellar rotation, namely: the dispersion in both rotation rates and lithium abundances is relatively small in the PMS stage, then strongly increases from the PMS to the ZAMS, and subsequently decreases on the main sequence. The parallel evolution of the range of lithium abundances and of rotation rates observed in solar-type stars is strongly suggestive of a physical link between rotation and lithium depletion.
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Yang, Shuai, Wenjing Shi, Yongzhen Ke i Yongjiang Xue. "A Two-Stage Registration Method for Dental Volumetric Data and Mesh Data". International Journal of Healthcare Information Systems and Informatics 16, nr 4 (październik 2021): 1–15. http://dx.doi.org/10.4018/ijhisi.20211001.oa29.
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Dental computed tomography (CT) images and optical surface scan data are widely used in dental computer-aided design systems. Registration is essential if they are used in software systems. Existing automatic registration methods are either time-consuming or rough, and interactive registration methods are experience-dependent and tedious because of a great deal of purely manual interactions. For overcoming these disadvantages, a two-stage registration method is proposed. In the rough registration stage, the rough translation and rotation matrices are obtained by applying unit quaternion based method on the points interactively selected from the two types of data. In the precise registration stage, the stridden sampling is used to reduce computational complexity and the proposed registration algorithm with scale transformation is used for precise registration. The proposed method offers a good trade-off between precision and time cost. The experimental results demonstrate that the proposed method provides faster convergence and smaller registration errors than existing methods.
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Anguera, Joaquin A., Patricia A. Reuter-Lorenz, Daniel T. Willingham i Rachael D. Seidler. "Contributions of Spatial Working Memory to Visuomotor Learning". Journal of Cognitive Neuroscience 22, nr 9 (wrzesień 2010): 1917–30. http://dx.doi.org/10.1162/jocn.2009.21351.
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Previous studies of motor learning have described the importance of cognitive processes during the early stages of learning; however, the precise nature of these processes and their neural correlates remains unclear. The present study investigated whether spatial working memory (SWM) contributes to visuomotor adaptation depending on the stage of learning. We tested the hypothesis that SWM would contribute early in the adaptation process by measuring (i) the correlation between SWM tasks and the rate of adaptation, and (ii) the overlap between the neural substrates of a SWM mental rotation task and visuomotor adaptation. Participants completed a battery of neuropsychological tests, a visuomotor adaptation task, and an SWM task involving mental rotation, with the latter two tasks performed in a 3.0-T MRI scanner. Performance on a neuropsychological test of SWM (two-dimensional mental rotation) correlated with the rate of early, but not late, visuomotor adaptation. During the early, but not late, adaptation period, participants showed overlapping brain activation with the SWM mental rotation task, in right dorsolateral prefrontal cortex and the bilateral inferior parietal lobules. These findings suggest that the early, but not late, phase of visuomotor adaptation engages SWM processes.
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He, Tangmei, Jingyi Zhang, Jinbo Yang i Hongwei Tan. "Lifespan of rotating black hole in the frame of generalized uncertainty principle". Modern Physics Letters A 31, nr 03 (18.01.2016): 1650008. http://dx.doi.org/10.1142/s0217732316500085.
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In this paper, the lifespan under the generalized uncertainty principle (GUP) of rotating black hole is derived through the corrected radiation energy flux and the first law of the thermodynamics of black hole. The radiation energy flux indicates that there exist the highest temperature and the minimum mass both of which are relevant to the initial mass of the black hole in the final stage of the radiation. The lifespan of rotating black hole includes three terms: the dominant term is just the lifespan in the flat spacetime; the other two terms are individually induced by the rotation and the GUP.