Periodicity Signatures of Lightcurves of Active Comets in Non-Principal-Axis Rotational States
Samarasinha, Nalin H.; Mueller, Beatrice E. A.; Barrera, Jose G.
2016-10-01
There are two comets (1P/Halley, 103P/Hartley 2) that are unambiguously in non-principal-axis (NPA) rotational states in addition to a few more comets that are candidates for NPA rotation. Considering this fact, and the ambiguities associated with how to accurately interpret the periodicity signatures seen in lightcurves of active comets, we have started an investigation to identify and characterize the periodicity signatures present in simulated lightcurves of active comets. We carried out aperture photometry of simulated cometary comae to generate model lightcurves and analyzed them with Fourier techniques to identify their periodicity signatures. These signatures were then compared with the input component periods of the respective NPA rotational states facilitating the identification of how these periodicity signatures are related to different component periods of the NPA rotation. Ultimately, we also expect this study to shed light on why only a small fraction of periodic comets is in NPA rotational states, whereas theory indicates a large fraction of them should be in NPA states (e.g., Jewitt 1999, EMP, 79, 35). We explore the parameter space with respect to different rotational states, different orientations for the total rotational angular momentum vector, and different locations on the nucleus for the source region(s). As for special cases, we also investigate potential NPA rotational states representative of comet 103P/Hartley2, the cometary target of the EPOXI mission. The initial results from our investigation will be presented at the meeting. The NASA DDAP Program supports this work through grant NNX15AL66G.
Brozović, Marina; Benner, Lance A. M.; Magri, Christopher; Scheeres, Daniel J.; Busch, Michael W.; Giorgini, Jon D.; Nolan, Michael C.; Jao, Joseph S.; Lee, Clement G.; Snedeker, Lawrence G.; Silva, Marc A.; Lawrence, Kenneth J.; Slade, Martin A.; Hicks, Michael D.; Howell, Ellen S.; Taylor, Patrick A.; Sanchez, Juan A.; Reddy, Vishnu; Dykhuis, Melissa; Corre, Lucille Le
2017-04-01
We report radar and optical photometric observations of near-Earth asteroid (214869) 2007 PA8 obtained during October 2-November 13, 2012. We observed 2007 PA8 on sixteen days with Goldstone (8560 MHz, 3.5 cm) and on five days with the 0.6 m telescope at Table Mountain Observatory. Closest approach was on November 5 at a distance of 0.043 au. Images obtained with Goldstone's new chirp system achieved range resolutions as fine as 3.75 m, placing thousands of pixels on the asteroid's surface, and revealing that 2007 PA8 is an elongated, asymmetric object. Surface features include angularities, facets, and a concavity approximately 400 m in diameter. We used the Shape software to estimate the asteroid's 3D shape and spin state. 2007 PA8 has a broad, rounded end and a tapered, angular end with sharp-crested ridges. The asteroid's effective diameter is 1.35 ± 0.07 km, which in combination with the absolute magnitude of 16.30 ± 0.52 gives an optical albedo of pV = 0.29 ± 0.14. The shape modeling of the radar data revealed that 2007 PA8 is a non-principal axis (NPA) rotator in the short-axis mode with an average period of precession by the long axis around the angular momentum vector of 4.26 ± 0.02 days and an oscillatory period around the long axis of 20.55 ± 3.75 days. The amplitude of rolling around the long axis is 42 ± 7° . The angular momentum vector points toward ecliptic longitude and latitude of 273.6 ± 10°, +16.9 ± 5°. 2007 PA8 is only the second confirmed short-axis mode NPA rotator known in the near-Earth asteroid population after (99942) Apophis (Pravec et al., 2014). 2007 PA8 has a geopotential high at the equator, where the equator is defined as the plane that contains the long and intermediate axis. This geopotential extreme could be interpreted as a large, hidden surface depression, or as evidence that 2007 PA8 is a multi-component body.
Actuator assembly including a single axis of rotation locking member
Quitmeyer, James N.; Benson, Dwayne M.; Geck, Kellan P.
2009-12-08
An actuator assembly including an actuator housing assembly and a single axis of rotation locking member fixedly attached to a portion of the actuator housing assembly and an external mounting structure. The single axis of rotation locking member restricting rotational movement of the actuator housing assembly about at least one axis. The single axis of rotation locking member is coupled at a first end to the actuator housing assembly about a Y axis and at a 90.degree. angle to an X and Z axis providing rotation of the actuator housing assembly about the Y axis. The single axis of rotation locking member is coupled at a second end to a mounting structure, and more particularly a mounting pin, about an X axis and at a 90.degree. angle to a Y and Z axis providing rotation of the actuator housing assembly about the X axis. The actuator assembly is thereby restricted from rotation about the Z axis.
Spin-stabilized magnetic levitation without vertical axis of rotation
Romero, Louis [Albuquerque, NM; Christenson, Todd [Albuquerque, NM; Aaronson, Gene [Albuquerque, NM
2009-06-09
The symmetry properties of a magnetic levitation arrangement are exploited to produce spin-stabilized magnetic levitation without aligning the rotational axis of the rotor with the direction of the force of gravity. The rotation of the rotor stabilizes perturbations directed parallel to the rotational axis.
Verticality Perception During Off-Vertical Axis Rotation
Vingerhoets, R.A.A.; Gisbergen, J.A.M. van; Medendorp, W.P.
2007-01-01
During prolonged rotation about a tilted yaw axis, often referred to as off-vertical axis rotation (OVAR), a percept of being translated along a conical path slowly emerges as the sense of rotation subsides. Recently, we found that these perceptual changes are consistent with a canal-otolith interac
Verticality perception during off-vertical axis rotation
Vingerhoets, R.A.A.; Gisbergen, J.A.M. van; Medendorp, W.P.
2007-01-01
During prolonged rotation about a tilted yaw axis, often referred to as off-vertical axis rotation (OVAR), a percept of being translated along a conical path slowly emerges as the sense of rotation subsides. Recently, we found that these perceptual changes are consistent with a canal-otolith interac
Angular momentum projection of tilted axis rotating states
Energy Technology Data Exchange (ETDEWEB)
Oi, M.; Onishi, N.; Tajima, N. [Tokyo Univ. (Japan); Horibata, T.
1998-03-01
We applied an exact angular momentum projection to three dimensional cranked HFB (3d-CHFB) states. Tilted axis rotating states (TAR) and principal axis rotating states (PAR) are compared. It is shown that TAR is more adequate than PAR for description of the back bending phenomena driven by tilted rotation or wobbling motion. (author)
Rotation Axis Variation Due To Spin Orbit Resonance
Gallavotti, G
1993-01-01
Abstract: rotation axis variation due to spin orbit resonance: conference report; keywords: planetary precession, rigid body, chaos, KAM, Arnold diffusion, averaging, celestial mechanics, classical mechanics, large deviations
Sequence-dependent rotation axis changes in tennis.
Hansen, Clint; Martin, Caroline; Rezzoug, Nasser; Gorce, Philippe; Bideau, Benoit; Isableu, Brice
2017-09-01
The purpose of this study was to evaluate the role of rotation axes during a tennis serve. A motion capture system was used to evaluate the contribution of the potential axes of rotation (minimum inertia axis, shoulder-centre of mass axis and the shoulder-elbow axis) during the four discrete tennis serve phases (loading, cocking, acceleration and follow through). Ten ranked athletes (International Tennis Number 1-3) repeatedly performed a flat service aiming at a target on the other side of the net. The four serve phases are distinct and thus, each movement phase seems to be organised around specific rotation axes. The results showed that the limbs' rotational axis does not necessarily coincide with the minimum inertia axis across the cocking phase of the tennis serve. Even though individual serving strategies were exposed, all participants showed an effect due to the cocking phase and changed the rotation axis during the task. Taken together, the results showed that despite inter-individual differences, nine out of 10 participants changed the rotation axis towards the minimum inertia and/or the mass axis in an endeavour to maximise external rotation of the shoulder to optimally prepare for the acceleration phase.
Thermally induced reversible easy axis rotations in permalloy thin films
Horsthuis, Winfried H.G.; Eijkel, Kees J.M.; Ridder, de René M.; Leeuwis, Henk
1988-01-01
The thermal stability of the easy axis orientation in thin Permalloy films was studied. This orientation was measured by two methods, i.e. the magneto-optic Kerr effect and a novel measurement scheme based on magnetoresistive effects. It appeared that even for small temperature changes rotations of
Institute of Scientific and Technical Information of China (English)
ZHA Feng; HU Bai-qing; QIN Fang-jun; LUO Yin-bo
2012-01-01
An effective and flexible rotation and compensation scheme is designed to improve the accuracy of rotating inertial navigation system (RINS).The accuracy of single-axial RINS is limited by the errors on the rotating axis.A novel inertial measurement unit (IMU) scheme with error compensation for the rotating axis of fiber optic gyros (FOG) RINS is presented.In the scheme,two couples of inertial sensors with similar error characteristics are mounted oppositely on the rotating axes to compensate the sensors error.Without any change for the rotation cycle,this scheme improves the system's precision and reliability,and also offers the redundancy for the system.The results of 36 h navigation simulation prove that the accuracy of the system is improved notably compared with normal strapdown INS,besides the heading accuracy is increased by 3 times compared with single-axial RINS,and the position accuracy is improved by 1 order of magnitude.
A Singular Limit Problem for Rotating Capillary Fluids with Variable Rotation Axis
Fanelli, Francesco
2016-04-01
In the present paper we study a singular perturbation problem for a Navier-Stokes-Korteweg model with Coriolis force. Namely, we perform the incompressible and fast rotation asymptotics simultaneously, while we keep the capillarity coefficient constant in order to capture surface tension effects in the limit. We consider here the case of variable rotation axis: we prove the convergence to a linear parabolic-type equation with variable coefficients. The proof of the result relies on compensated compactness arguments. Besides, we look for minimal regularity assumptions on the variations of the axis.
A Singular Limit Problem for Rotating Capillary Fluids with Variable Rotation Axis
Fanelli, Francesco
2016-12-01
In the present paper we study a singular perturbation problem for a Navier-Stokes-Korteweg model with Coriolis force. Namely, we perform the incompressible and fast rotation asymptotics simultaneously, while we keep the capillarity coefficient constant in order to capture surface tension effects in the limit. We consider here the case of variable rotation axis: we prove the convergence to a linear parabolic-type equation with variable coefficients. The proof of the result relies on compensated compactness arguments. Besides, we look for minimal regularity assumptions on the variations of the axis.
Symmetry axis based object recognition under translation, rotation and scaling.
Hyder, Mashud; Islam, Md Monirul; Akhand, M A H; Murase, Kazuyuki
2009-02-01
This paper presents a new approach, known as symmetry axis based feature extraction and recognition (SAFER), for recognizing objects under translation, rotation and scaling. Unlike most previous invariant object recognition (IOR) systems, SAFER puts emphasis on both simplicity and accuracy of the recognition system. To achieve simplicity, it uses simple formulae for extracting invariant features from an object. The scheme used in feature extraction is based on the axis of symmetry and angles of concentric circles drawn around the object. SAFER divides the extracted features into a number of groups based on their similarity. To improve the recognition performance, SAFER uses a number of neural networks (NNs) instead of single NN are used for training and recognition of extracted features. The new approach, SAFER, has been tested on two of real world problems i.e., English characters with two different fonts and images of different shapes. The experimental results show that SAFER can produce good recognition performance in comparison with other algorithms.
Propagation of angular errors in two-axis rotation systems
Torrington, Geoffrey K.
2003-10-01
Two-Axis Rotation Systems, or "goniometers," are used in diverse applications including telescope pointing, automotive headlamp testing, and display testing. There are three basic configurations in which a goniometer can be built depending on the orientation and order of the stages. Each configuration has a governing set of equations which convert motion between the system "native" coordinates to other base systems, such as direction cosines, optical field angles, or spherical-polar coordinates. In their simplest form, these equations neglect errors present in real systems. In this paper, a statistical treatment of error source propagation is developed which uses only tolerance data, such as can be obtained from the system mechanical drawings prior to fabrication. It is shown that certain error sources are fully correctable, partially correctable, or uncorrectable, depending upon the goniometer configuration and zeroing technique. The system error budget can be described by a root-sum-of-squares technique with weighting factors describing the sensitivity of each error source. This paper tabulates weighting factors at 67% (k=1) and 95% (k=2) confidence for various levels of maximum travel for each goniometer configuration. As a practical example, this paper works through an error budget used for the procurement of a system at Sandia National Laboratories.
Song, Yoogeun; Pu, Hung-Yi; Hirotani, Kouichi; Matsushita, Satoki; Kong, Albert K. H.; Chang, Hsiang-Kuang
2017-01-01
We investigate the acceleration of electrons and positrons by magnetic-field-aligned electric fields in the polar funnel of an accreting black hole (BH). Applying the pulsar outer-gap theory to BH magnetospheres, we find that such a lepton accelerator arises in the immediate vicinity of the event horizon due to frame-dragging, and that their gamma-ray luminosity increases with decreasing accretion rate. Furthermore, we demonstrate that the gamma-ray flux is enhanced along the rotation axis by...
Assessment of movement distribution in the lumbar spine using the instantaneous axis of rotation
Energy Technology Data Exchange (ETDEWEB)
Park, Ki Won [Trine University, Angola (Indonesia)
2014-12-15
The position of the torso and the magnitude of exertion are thought to influence the distribution pattern of intervertebral movements within the lumbar spine. Abnormal intervertebral movements have been correlated with the risk of spine injuries. Since the capability to measure movement distribution within the lumbar spine noninvasively is limited, a convenient method to diagnose joint motion function was proposed. The goal of this research was to test the efficacy of the instantaneous axis of rotation for assessment of the distribution of movement within the lumbar spine. The proposed method was evaluated in the bio mechanical model. The results showed that the location of instantaneous axis of rotation lowered with increased trunk exertion force, and slightly moved higher with increased trunk angle. Recognizing that abnormal location of the instantaneous axis of rotation correlated with spinal pain, these results suggest potential the location of the instantaneous axis of rotation relates to the risk of low back pain on distributed spinal kinematics.
Vertical-Axis Rotations Within the Peruvian Altiplano
Roperch, P.; Carlotto, V.
2007-05-01
During the last two decades, numerous paleomagnetic studies have reported tectonic rotations in the Central Andes but only few data are available for a key tectonic region like the southern Peruvian Altiplano. Clockwise rotations (> 25°) are recorded in Mesozoic to Early Paleogene rocks along the forearc of northern Chile (23-28°S) [Arriagada et al., 2006, Tectonics, doi:10.1029/2005TC001923]. Within the forearc of southern Peru, counterclockwise rotations recorded by flat lying red-beds (Moquegua Formation) increase from south to north from about -30° to more than -45° and rotations decrease with time from late Eocene to late Oligocene - early Miocene time [Roperch et al., 2006, Tectonics, doi:10.1029/2005TC001882]. Rotations in the forearc seems concomitant with deformation localized in the Eastern Cordillera. We speculate that the rotations within the forearc are related to shortening to the east of the Altiplano leading to the first stage of oroclinal bending. If this model is correct, rotations within the Altiplano should have similar magnitude than those of the forearc. We have undertaken a new paleomagnetic sampling (490 samples) along a transect from Nazca (8 sites in the early Miocene Nazca ignimbrites and 7 sites in Oligocene volcanics near Puquio, Western Altiplano) to Abancay (8 sites in Paleocene - Eocene red beds and dikes, Central Altiplano) and Cusco (20 sites in Eocene - Oligocene red beds, Eastern Altiplano). We will present the new results and discuss the spatial and temporal distribution of the tectonic rotations within the Andes of southern Peru.
Tilted axis rotation in odd-odd {sup 164}Tm
Energy Technology Data Exchange (ETDEWEB)
Reviol, W.; Riedinger, L.L.; Wang, X.Z.; Zhang, J.Y. [Univ. of Tennessee, Knoxville, TN (United States)] [and others
1996-12-31
Ten band structures are observed in {sup 164}Tm, among them sets of parallel and anti-parallel couplings of the proton and neutron spins. The Tilted Axis Cranking scheme is applied for the first time to an odd-odd nucleus in a prominent region of nuclear deformation.
Rotation Angle for the Optimum Tracking of One-Axis Trackers
Energy Technology Data Exchange (ETDEWEB)
Marion, W. F.; Dobos, A. P.
2013-07-01
An equation for the rotation angle for optimum tracking of one-axis trackers is derived along with equations giving the relationships between the rotation angle and the surface tilt and azimuth angles. These equations are useful for improved modeling of the solar radiation available to a collector with tracking constraints and for determining the appropriate motor revolutions for optimum tracking.
Rotation Angle for the Optimum Tracking of One-Axis Trackers
Energy Technology Data Exchange (ETDEWEB)
Marion, W. F.; Dobos, A. P.
2013-07-01
An equation for the rotation angle for optimum tracking of one-axis trackers is derived along with equations giving the relationships between the rotation angle and the surface tilt and azimuth angles. These equations are useful for improved modeling of the solar radiation available to a collector with tracking constraints and for determining the appropriate motor revolutions for optimum tracking.
Energy Technology Data Exchange (ETDEWEB)
KPONOU,A.; PIKIN,A.; BEEBE,E.; ALESSI,J.
2000-11-06
We have analyzed the motion of a Hall probe, which is rotated about an axis that is arbitrarily displaced and oriented with respect to the magnetic axis of a solenoid. We outline how the magnetic field measured by the rotating Hall probe can be calculated. We show how to compare theoretical results with actual measurements, to determine the displacement and orientation of the axis of rotation of the probe from the magnetic axis. If the center of rotation of the probe is known by surveying, the corresponding point on the magnetic axis of the solenoid can be located. This is applied to a solenoid that was built for BNL by Oxford Instruments.
Binocular Coordination of the Human Vestibulo-Ocular Reflex during Off-axis Pitch Rotation
Wood, S. J.; Reschke, M. F.; Kaufman, G. D.; Black, F. O.; Paloski, W. H.
2006-01-01
Head movements in the sagittal pitch plane typically involve off-axis rotation requiring both vertical and horizontal vergence ocular reflexes to compensate for angular and translational motion relative to visual targets of interest. The purpose of this study was to compare passive pitch VOR responses during rotation about an Earth-vertical axis (canal only cues) with off-axis rotation (canal and otolith cues). Methods. Eleven human subjects were oscillated sinusoidally at 0.13, 0.3 and 0.56 Hz while lying left-side down with the interaural axis either aligned with the axis of rotation or offset by 50 cm. In a second set of measurements, twelve subjects were also tested during sinusoidally varying centrifugation over the same frequency range. The modulation of vertical and horizontal vergence ocular responses was measured with a binocular videography system. Results. Off-axis pitch rotation enhanced the vertical VOR at lower frequencies and enhanced the vergence VOR at higher frequencies. During sinusoidally varying centrifugation, the opposite trend was observed for vergence, with both vertical and vergence vestibulo-ocular reflexes being suppressed at the highest frequency. Discussion. These differential effects of off-axis rotation over the 0.13 to 0.56 Hz range are consistent with the hypothesis that otolith-ocular reflexes are segregated in part on the basis of stimulus frequency. At the lower frequencies, tilt otolith-ocular responses compensate for declining canal input. At higher frequencies, translational otolith-ocular reflexes compensate for declining visual contributions to the kinematic demands required for fixating near targets.
Off-vertical axis rotation: a test of the otolith-ocular reflex
Furman, J. M.; Schor, R. H.; Schumann, T. L.
1992-01-01
The vestibulo-ocular reflex was studied via off-vertical axis rotation (OVAR) in the dark. The axis of the turntable could be tilted from vertical by up to 30 degrees. Eye movements were measured with electro-oculography. Results from healthy asymptomatic subjects indicated that 1) a reliable otolith-induced response could be obtained during constant velocity OVAR using a velocity of 60 degrees/s with a tilt of 30 degrees; 2) constant velocity OVAR rotation was nausea-producing and, especially if subjects were rotated in the dark about an earth-vertical axis prior to being tilted, disorienting; and 3) sinusoidal OVAR produced minimal nausea; the eye movement response appeared to be the result of a combination of semicircular canal and otolith components. We conclude that OVAR has the potential of becoming a useful method for clinically assessing both the otolith-ocular reflex and semicircular canal-otolith interaction.
Implementation of Unsteady Double-Axis of Rotation Motion to Predict Pitch-Damping Moment
2016-10-18
becomes important when eventually defining initial Euler angles. This coordinate system defines the inertial reference frame. Approved for public...coordinates, except when defining the initial Euler angles set in “Initialization based on:” select “ Euler Angles.” For this example, set the coning angle...to the global longitudinal axis before setting the Euler angles. Since the rotation is about the global +y-axis, Euler_y is set to 0.5 (note degrees
Horns, Daniel M.; Verosub, Kenneth L.
1995-03-01
Outcrops of shallow marine sedimentary rocks of the Neogene Purisima Formation and Santa Cruz Mudstone occur throughout the Santa Cruz Mountains and along the coast of Santa Cruz and San Mateo counties in California. Within the Santa Cruz Mountains, the Purisima Formation has been extensively folded and offset by reverse faults. Along the coast, the Purisima Formation and Santa Cruz Mudstone are only gently folded although the Purisima Formation is cut by the San Gregorio Fault Zone. Previous paleomagnetic studies have shown that vertical axis rotation has occurred within some parts of the San Gregorio Fault Zone. As part of a kinematic study of the San Gregorio Fault Zone, this paleomagnetic investigation of the Purisima Formation and Santa Cruz Mudstone was conducted to determine the extent of the vertical axis rotation. The characteristic paleomagnetic directions of the Purisima Formation and Santa Cruz Mudstone, which we interpret as the primary directions, indicate that a clockwise vertical axis rotation of 35 deg to 60 deg has occurred throughout the San Gregorio Zone, whereas no rotation has occurred away from the fault zone. This result suggests that vertical axis rotation is fundamentally related to shear across the San Gregorio Fault Zone. Our work also indicates that while the Purisima Formation and Santa Cruz Mudstone along the coast have retained their primary magnetizations, the Purisima Formation within the Santa Cruz Mountains has been remagnetized after folding.
Accurate Compensation of Attitude Angle Error in a Dual-Axis Rotation Inertial Navigation System
Jiang, Rui; Yang, Gongliu; Zou, Rui; Wang, Jing; Li, Jing
2017-01-01
In the dual-axis rotation inertial navigation system (INS), besides the gyro error, accelerometer error, rolling misalignment angle error, and the gimbal angle error, the shaft swing angle and the axis non-orthogonal angle also affect the attitude accuracy. Through the analysis of the structure, we can see that the shaft swing angle and axis non-orthogonal angle will produce coning errors which cause the fluctuation of the attitude. According to the analysis of the rotation vector, it can be seen that the coning error will generate additional drift velocity along the rotating shaft, which can reduce the navigation precision of the system. In this paper, based on the establishment of the modulation average frame, the vector projection is carried out, and then the attitude conversion matrix and the attitude error matrix mainly including the shaft swing angle and axis non-orthogonal are obtained. Because the attitude angles are given under the static condition, the shaft swing angle and the axis non-orthogonal angle are estimated by the static Kalman filter (KF). This kind of KF method has been widely recognized as the standard optimal estimation tool for estimating the parameters such as coning angles (α1 , α2), initial phase angles (ϕ1,ϕ2), and the non-perpendicular angle (η). In order to carry out the system level verification, a dual axis rotation INS is designed. Through simulation and experiments, the results show that the amplitudes of the attitude angles’ variation are reduced by about 20%–30% when the shaft rotates. The attitude error equation is reasonably simplified and the calibration method is accurate enough. The attitude accuracy is further improved. PMID:28304354
Manifestation of the rotational Doppler effect by use of an off-axis optical vortex beam.
Basistiy, I V; Slyusar, V V; Soskin, M S; Vasnetsov, M V; Bekshaev, A Ya
2003-07-15
We report what is to our knowledge the first all-optical detection of the frequency beats between Gaussian and Laguerre-Gaussian LG0(1) modes in their axial superposition, caused by the rotational Doppler effect. The relation between the observable off-axis optical vortex rotation and the rotational frequency shift of the Laguerre-Gaussian component is ascertained. The results can be used as a physical basis for recognition of Laguerre-Gaussian mode spectra along their orbital angular momenta.
Vortex Breakdown Generated by off-axis Bifurcation in a cylinder with rotating covers
DEFF Research Database (Denmark)
Bisgaard, Anders; Brøns, Morten; Sørensen, Jens Nørkær
2006-01-01
Vortex breakdown of bubble type is studied for the flow in a cylinder with rotating top and bottom covers. For large ratios of the angular velocities of the covers, we observe numerically that the vortex breakdown bubble in the steady regime may occur through the creation of an off-axis vortex ring...
Numerical results in a vertical wind axis turbine with relative rotating blades
Energy Technology Data Exchange (ETDEWEB)
Bayeul-Laine, Annie-Claude; Dockter, Aurore; Simonet, Sophie; Bois, Gerard [Arts et Metiers PARISTECH (France)
2011-07-01
The use of wind energy to produce electricity through wind turbines has spread world-wide. The quantity of electricity produced is affected by numerous factors such as wind speed and direction and turbine design; the aim of this paper is to assess the influence of different blades on the performance of a turbine. This study was performed on a turbine in which the blades have a rotating movement, each around its own axis and around the turbine's axis. Unsteady simulations were carried out with several blade stagger angles and one wind speed and 2 different blade geometries were used for 4 rotational speeds. Results showed that the studied turbine gave better performance than vertical axis wind turbines and that blade sketch, blade speed ratios, and blade stagger angle were important influences on the performance. This study showed that this kind of turbine has the potential to achieve good performance but that further work needs to be done.
Attitude Heading Reference System Using MEMS Inertial Sensors with Dual-Axis Rotation
Directory of Open Access Journals (Sweden)
Li Kang
2014-09-01
Full Text Available This paper proposes a low cost and small size attitude and heading reference system based on MEMS inertial sensors. A dual-axis rotation structure with a proper rotary scheme according to the design principles is applied in the system to compensate for the attitude and heading drift caused by the large gyroscope biases. An optimization algorithm is applied to compensate for the installation angle error between the body frame and the rotation table’s frame. Simulations and experiments are carried out to evaluate the performance of the AHRS. The results show that the proper rotation could significantly reduce the attitude and heading drifts. Moreover, the new AHRS is not affected by magnetic interference. After the rotation, the attitude and heading are almost just oscillating in a range. The attitude error is about 3° and the heading error is less than 3° which are at least 5 times better than the non-rotation condition.
Attitude heading reference system using MEMS inertial sensors with dual-axis rotation.
Kang, Li; Ye, Lingyun; Song, Kaichen; Zhou, Yang
2014-09-29
This paper proposes a low cost and small size attitude and heading reference system based on MEMS inertial sensors. A dual-axis rotation structure with a proper rotary scheme according to the design principles is applied in the system to compensate for the attitude and heading drift caused by the large gyroscope biases. An optimization algorithm is applied to compensate for the installation angle error between the body frame and the rotation table's frame. Simulations and experiments are carried out to evaluate the performance of the AHRS. The results show that the proper rotation could significantly reduce the attitude and heading drifts. Moreover, the new AHRS is not affected by magnetic interference. After the rotation, the attitude and heading are almost just oscillating in a range. The attitude error is about 3° and the heading error is less than 3° which are at least 5 times better than the non-rotation condition.
CSIR Research Space (South Africa)
Abdul Gaffar, MY
2007-10-01
Full Text Available in ISAR imaging mostly under the limited assumption that a targets axis of rotation is constant over the CPI. This paper investigates how the targets time-varying Doppler generating axis of rotation, caused by the complex 3D motion of a target at sea...
Amel'kin, N. I.
2009-01-01
The set of steady motions of the system named in the title is represented parametrically via the gyro gimbal rotation angle for an arbitrary position of the gimbal axis. We study the set of steady motions for a system in which the gyro gimbal axis is parallel to a principal plane of inertia as well
A self-calibration method for tri-axis rotational inertial navigation system
Gao, Pengyu; Li, Kui; Wang, Lei; Liu, Zengjun
2016-11-01
The navigation accuracy of the rotational inertial navigation system (RINS) could be greatly improved by periodically rotating the inertial measurement unit (IMU) with gimbals. However, error parameters in RINS should be effectively calibrated and compensated. In this paper, a self-calibration method is proposed for tri-axis RINS using attitude errors and velocity errors as measurements. The proposed calibration scheme is designed as three separate steps, and a certain gimbal rotates continuously in each step. All the error parameters in the RINS are calibrated when the whole scheme finishes. The separate calibration steps reduce the correlations between error parameters, and the observability of errors in this method is clear to demonstrate according to the relations between navigation errors and error parameters when gimbals rotate. Each calibration step only lasts 12 min, thus gyro drifts and accelerometers biases could be regarded as constant. The proposed calibration scheme is tested in both simulation and actual tri-axis RINS, and simulation and experimental results show that all 23 error parameters could be well estimated in tri-axis RINS. A long-term vehicle navigation experiment results show that after calibration and compensation, the navigation performance has doubled approximately, and the velocity accuracy is less than 2 m s-1 while the position accuracy is less than 1500 m, fully illustrating the significance of the proposed self-calibration method in improving the navigation performance of RINS.
Antimagnetic rotation in 108,110In with tilted axis cranking relativistic mean-field approach
Sun, Wu-Ji; Xu, Hai-Dan; Li, Jian; Liu, Yong-Hao; Ma, Ke-Yan; Yang, Dong; Lu, Jing-Bing; Ma, Ying-Jun
2016-08-01
Based on tilted axis cranking relativistic mean-field theory within point-coupling interaction PC-PK1, the rotational structure and the characteristic features of antimagnetic rotation for ΔI = 2 bands in 108,110In are studied. Tilted axis cranking relativistic mean-field calculations reproduce the experimental energy spectrum well and are in agreement with the experimental I ∼ ω plot, although the calculated spin overestimates the experimental values. In addition, the two-shears-like mechanism in candidate antimagnetic rotation bands is clearly illustrated and the contributions from two-shears-like orbits, neutron (gd) orbits above Z = 50 shell and Z = 50, N = 50 core are investigated microscopically. The predicted B(E2), dynamic moment of inertia ℑ(2), deformation parameters β and γ, and ℑ(2)/B(E2) ratios in tilted axis cranking relativistic mean-field calculations are discussed and the characteristic features of antimagnetic rotation for the bands before and after alignment are shown. Supported by National Natural Science Foundation of China (11205068, 11205069, 11405072, 11475072, 11547308) and China Postdoctoral Science Foundation (2012M520667)
A Kinematic Model for Vertical Axis Rotation within the Mina Deflection of the Walker Lane
Gledhill, T.; Pluhar, C. J.; Johnson, S. A.; Lindeman, J. R.; Petronis, M. S.
2016-12-01
The Mina Deflection, at the boundary between the Central and Southern Walker Lane, spans the California-Nevada border and includes a heavily-faulted Pliocene volcanic field overlying Miocene ignimbrites. The dextral Walker Lane accommodates 25% of relative Pacific-North America plate motion and steps right across the sinistral Mina deflection. Ours and previous work shows that the Mina Deflection partially accommodates deformation by vertical-axis rotation of up to 99.9o ± 6.1o rotation since 11 Ma. This rotation is evident in latite ignimbrite of Gilbert et al. (1971), which we have formalized as three members of Tuff of Huntoon Creek (THC). The welded, basal, normal-polarity Huntoon Valley Member of THC is overlain by the unwelded to partially-welded, reversed-polarity Adobe Hills Mbr. This member includes internal breaks suggesting multiple eruptive phases, but the paleomagnetic results from each are statistically indistinguishable, meaning that they were likely erupted in rapid succession (within a few centuries of one another). THC ends with a welded member exhibiting very shallow inclination and south declination that we call Excursional Mbr. One of the upper members has been dated at 11.17 ± 0.04 Ma. These Miocene units are overlain by Pliocene basalts, Quaternary alluvium, and lacustrine deposits. Our paleomagnetic results show a gradient between the zero rotation domain and high rotation across a 20km baseline. A micropolar model, based on 25 years of earthquake data from the Northern and Southern California Seismic Network, suggest the Mina Deflection is currently experiencing transpressional seismogenic deformation (Unruh et al., 2003). Accepting Unruh's model and assuming continuous rotation since 11 Ma, we propose a kinematic model for the western Mina Deflection that accommodates 90o of vertical axis rotation from N-S to ENE-WSW oriented blocks.
Energy Technology Data Exchange (ETDEWEB)
Schiefer, H., E-mail: johann.schiefer@kssg.ch; Peters, S.; Plasswilm, L. [Klinik für Radio-Onkologie, Kantonsspital St.Gallen, Rorschacherstrasse 107, St.Gallen CH-9007 (Switzerland); Ingulfsen, N.; Kluckert, J. [Kantonsschule am Burggraben St.Gallen, Burggraben 21, St.Gallen CH-9000 (Switzerland)
2015-03-15
Purpose: For stereotactic radiosurgery, the AAPM Report No. 54 [AAPM Task Group 42 (AAPM, 1995)] requires the overall stability of the isocenter (couch, gantry, and collimator) to be within a 1 mm radius. In reality, a rotating system has no rigid axis and thus no isocenter point which is fixed in space. As a consequence, the isocenter concept is reviewed here. It is the aim to develop a measurement method following the revised definitions. Methods: The mechanical isocenter is defined here by the point which rotates on the shortest path in the room coordinate system. The path is labeled as “isocenter path.” Its center of gravity is assumed to be the mechanical isocenter. Following this definition, an image-based and radiation-free measurement method was developed. Multiple marker pairs in a plane perpendicular to the assumed gantry rotation axis of a linear accelerator are imaged with a smartphone application from several rotation angles. Each marker pair represents an independent measuring system. The room coordinates of the isocenter path and the mechanical isocenter are calculated based on the marker coordinates. The presented measurement method is by this means strictly focused on the mechanical isocenter. Results: The measurement result is available virtually immediately following completion of measurement. When 12 independent measurement systems are evaluated, the standard deviations of the isocenter path points and mechanical isocenter coordinates are 0.02 and 0.002 mm, respectively. Conclusions: The measurement is highly accurate, time efficient, and simple to adapt. It is therefore suitable for regular checks of the mechanical isocenter characteristics of the gantry and collimator rotation axis. When the isocenter path is reproducible and its extent is in the range of the needed geometrical accuracy, it should be taken into account in the planning process. This is especially true for stereotactic treatments and radiosurgery.
Merfeld, D. M.; Paloski, W. H. (Principal Investigator)
1996-01-01
The vestibulo-ocular reflexes (VOR) are determined not only by angular acceleration, but also by the presence of gravity and linear acceleration. This phenomenon was studied by measuring three-dimensional nystagmic eye movements, with implanted search coils, in four male squirrel monkeys. Monkeys were rotated in the dark at 200 degrees/s, centrally or 79 cm off-axis, with the axis of rotation always aligned with gravity and the spinal axis of the upright monkeys. The monkey's position relative to the centripetal acceleration (facing center or back to center) had a dramatic influence on the VOR. These studies show that a torsional response was always elicited that acted to shift the axis of eye rotation toward alignment with gravito-inertial force. On the other hand, a slow phase downward vertical response usually existed, which shifted the axis of eye rotation away from the gravito-inertial force. These findings were consistent across all monkeys. In another set of tests, the same monkeys were rapidly tilted about their interaural (pitch) axis. Tilt orientations of 45 degrees and 90 degrees were maintained for 1 min. Other than a compensatory angular VOR during the rotation, no consistent eye velocity response was ever observed during or following the tilt. The absence of any response following tilt proves that the observed torsional and vertical responses were not a positional nystagmus. Model simulations qualitatively predict all components of these eccentric rotation and tilt responses. These simulations support the conclusion that the VOR during eccentric rotation may consist of two components: a linear VOR and a rotational VOR. The model predicts a slow phase downward, vertical, linear VOR during eccentric rotation even though there was never a change in the force aligned with monkey's spinal (Z) axis. The model also predicts the torsional components of the response that shift the rotation axis of the angular VOR toward alignment with gravito-inertial force.
Titan's interior from its rotation axis orientation and its Love number
Baland, Rose-Marie; Gabriel, Tobie; Axel, Lefèvre
2013-04-01
The tidal Love number k2 of Titan has been recently estimated from Cassini flybys radio-tracking and is consistent with the presence of a global ocean in Titan's interior, located between two ice layers (Iess et al. 2012), in accordance with prediction from interior and evolutionary models for Titan. Previously, the orientation of the rotation axis of Titan has been measured on the basis of radar images from Cassini (Stiles et al. 2008). Titan's obliquity, is about 0.3. The measured orientation is more consistent with the presence of a global internal liquid ocean than with an entirely solid Titan (Baland et al. 2011). The global topography data of Titan seem to indicate some departure from the hydrostatic shape expected for a synchronous satellite under the influence of its rotation and the static tides raised by the central planet (Zebker et al. 2009). This may be explained by a differential tidal heating in the ice shell which flattens the poles (Nimmo and Bills 2010). A surface more flattened than expected implies compensation in depth to explain the measured gravity coefficients C20 and C22 of Iess et al. (2012). Here, all layers are assumed to have a tri-axial ellipsoid shape, but with polar and equatorial flattenings that differ from the hydrostatic expected ones. We assess the influence of this non-hydrostatic shape on the conclusions of Baland et al. (2011), which developped a Cassini state model for the orientation of the rotation axis of a synchronous satellite having an internal liquid layer. We assess the possibility to constrain Titan's interior (and particularly the structure of the water/ice layer) from both the rotation axis orientation and the Love number. We consider a range of internal structure models consistent with the mean density and the mean radius of Titan, and made of a shell, an ocean, a mantle, and a core, from the surface to the center, with various possible compositions (e.g. ammonia mixed with water for the ocean). The internal
Frauendorf, S
2000-01-01
The selfconsistent cranking approach is extended to the case of rotation about an axis which is tilted with respect to the principal axes of the deformed potential (Tilted Axis Cranking). Expressions for the energies and the intra bands electro-magnetic transition probabilities are given. The mean field solutions are interpreted in terms of quantal rotational states. The construction of the quasiparticle configurations and the elimination of spurious states is discussed. The application of the theory to high spin data is demonstrated by analyzing the multi-quasiparticle bands in the nuclides with N=102,103 and Z=71,72,73.
Translational Vestibulo-Ocular Reflexes During Off-Vertical Axis Rotation
Wood, Scott J.; Clement, Gilles
2009-01-01
The translational vestibulo-ocular reflex (tVOR) is an otolith-mediated response that stabilizes near vision during linear acceleration at higher frequencies where visually mediated reflexes are not adequate. The modulation of horizontal and vergence eye movements during Off-Vertical Axis Rotation (OVAR) are presumed to reflect the tVOR in response to the continuously varying linear acceleration in the interaural and nasooccipital axes, respectively. The purpose of this study was to examine the effect of frequency and fixation distance on the modulation of slow phase eye velocity (SPV) as further evidence that the tVOR is elicited during OVAR. Eighteen subjects were rotated about their longitudinal axis tilted by 30 deg off-vertical. Rotational velocities varied between 18 and 288 deg/sec corresponding to a frequency range of 0.05 to 0.8 Hz. Fixation distance was altered by asking subjects to imagine stationary targets that were briefly presented at 0.5, 1 and 2 m during some rotation cycles. The target flash was 40 msec in the nose-up position at eye level. Oculomotor responses were recorded in the dark using infrared binocular videography. Sinusoidal curve fits were used to derive amplitude, phase and bias velocity of the eye movements across multiple rotation cycles. Consistent with previous studies, the modulation of both horizontal and vergence SPV increased with stimulus frequency. The effect of fixation distance was negligible at lower frequencies. The modulation of horizontal and vergence SPV was; however, proportional to fixation distance during OVAR at 0.8 Hz. This increasing sensitivity and dependence on fixation distance of horizontal and vergence SPV during OVAR is consistent with tVOR characteristics measured during other types of linear motion. We conclude that the modulation of horizontal and vergence SPV will be diagnostically more useful at higher stimulus frequencies where the tVOR is more robust.
Translational Vestibulo-Ocular Reflexes During Off-Vertical Axis Rotation
Wood, Scott J.; Clement, Gilles
2009-01-01
The translational vestibulo-ocular reflex (tVOR) is an otolith-mediated response that stabilizes near vision during linear acceleration at higher frequencies where visually mediated reflexes are not adequate. The modulation of horizontal and vergence eye movements during Off-Vertical Axis Rotation (OVAR) are presumed to reflect the tVOR in response to the continuously varying linear acceleration in the interaural and nasooccipital axes, respectively. The purpose of this study was to examine the effect of frequency and fixation distance on the modulation of slow phase eye velocity (SPV) as further evidence that the tVOR is elicited during OVAR. Eighteen subjects were rotated about their longitudinal axis tilted by 30 deg off-vertical. Rotational velocities varied between 18 and 288 deg/sec corresponding to a frequency range of 0.05 to 0.8 Hz. Fixation distance was altered by asking subjects to imagine stationary targets that were briefly presented at 0.5, 1 and 2 m during some rotation cycles. The target flash was 40 msec in the nose-up position at eye level. Oculomotor responses were recorded in the dark using infrared binocular videography. Sinusoidal curve fits were used to derive amplitude, phase and bias velocity of the eye movements across multiple rotation cycles. Consistent with previous studies, the modulation of both horizontal and vergence SPV increased with stimulus frequency. The effect of fixation distance was negligible at lower frequencies. The modulation of horizontal and vergence SPV was; however, proportional to fixation distance during OVAR at 0.8 Hz. This increasing sensitivity and dependence on fixation distance of horizontal and vergence SPV during OVAR is consistent with tVOR characteristics measured during other types of linear motion. We conclude that the modulation of horizontal and vergence SPV will be diagnostically more useful at higher stimulus frequencies where the tVOR is more robust.
Sun-Relative Pointing for Dual-Axis Solar Trackers Employing Azimuth and Elevation Rotations
Energy Technology Data Exchange (ETDEWEB)
Riley, Daniel [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hansen, Clifford W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2014-12-30
Dual axis trackers employing azimuth and elevation rotations are common in the field of photovoltaic (PV) energy generation. Accurate sun-tracking algorithms are widely available. However, a steering algorithm has not been available to accurately point the tracker away from the sun such that a vector projection of the sun beam onto the tracker face falls along a desired path relative to the tracker face. We have developed an algorithm which produces the appropriate azimuth and elevation angles for a dual axis tracker when given the sun position, desired angle of incidence, and the desired projection of the sun beam onto the tracker face. Development of this algorithm was inspired by the need to accurately steer a tracker to desired sun-relative positions in order to better characterize the electro-optical properties of PV and CPV modules.
Guo, Jianyu; Jiang, Ping; Yang, Huajun; Niu, Ye; Xianyu, Jiawei
2017-03-20
A novel optical antenna with an off-axis confocal parabolic rotating surfaces configuration is designed for achieving maximum transmission efficiency. An improved 3-D ray tracing method based on the vector theory of reflection is used to simulate spatial rays transmitting through the antenna system. Aberrations and the spatial divergence angles of the output beam, which are caused by on-axial defocusing and off-axial defocusing between the primary reflector and secondary reflector, are visualized and effects on receiver efficiency of the antenna system are analyzed in detail. This work will provide a reference for improving the transmission efficiency of long-range communication systems.
Relation between perception of vertical axis rotation and vestibulo-ocular reflex symmetry
Peterka, Robert J.; Benolken, Martha S.
1992-01-01
Subjects seated in a vertical axis rotation chair controlled their rotational velocity by adjusting a potentiometer. Their goal was to null out pseudorandom rotational perturbations in order to remain perceptually stationary. Most subjects showed a slow linear drift of velocity (a constant acceleration) to one side when they were deprived of an earth-fixed visual reference. The amplitude and direction of this drift can be considered a measure of a static bias in the subject's perception of rotation. The presence of a perceptual bias is consistent with a small, constant imbalance of vestibular function which could be of either central or peripheral origin. Deviations from perfect vestibulo-ocular reflex (VOR) symmetry are also assumed to be related to imbalances in either peripheral or central vestibular function. Researchers looked for correlations between perceptual bias and various measures of vestibular reflex symmetry that might suggest a common source for both reflective and perceptual imbalances. No correlations were found. Measurement errors could not account for these results since repeated tests on the same subjects of both perceptual bias and VOR symmetry were well correlated.
A bead on a hoop rotating about a horizontal axis: a 1-D ponderomotive trap
Johnson, Andrew K
2009-01-01
We describe a simple mechanical system that operates as a ponderomotive particle trap, consisting of a circular hoop and a frictionless bead, with the hoop rotating about a horizontal axis lying in the plane of the hoop. The bead in the frame of the hoop is thus exposed to an effective sinusoidally-varying gravitational field. This field's component along the hoop is a zero at the top and bottom. In the same frame, the bead experiences a time-independent centrifugal force that is zero at the top and bottom as well. The system is analyzed in the ideal case of small displacements from the minimum, and the motion of the particle is shown to satisfy the Mathieu equation. In the particular case that the axis of rotation is tangential to the hoop, the system is an exact analog for the rf Paul ion trap. Various complicating factors such as anharmonic terms, friction and noise are considered. A working model of the proposed system has been constructed, using a ball-bearing rolling in a tube along the outside of a sec...
Counter-rotating vortex pairs in the wake of a vertical axis wind turbine
Rolin, Vincent; Porté-Agel, Fernando
2017-04-01
Despite the rising popularity of vertical axis wind turbines, or VAWTs, the wakes behind these machines is much less well understood than those behind horizontal axis wind turbines, or HAWTs. A thorough understanding of wakes is important as they can cause turbines in wind farms to produce less power than anticipated and increase the fatigue loading on turbines due to vibrations. In order to gain a deeper understanding of the wake behind a vertical axis wind turbine in atmospheric flow stereo-PIV is implemented in a boundary-layer wind tunnel to produce snapshots of the 3-component velocity field in the wake at various downstream positions. The boundaries of the wake are readily observed due to the high velocity gradients and turbulence present here. Two pairs of counter-rotating vortices similar to those in the wake of yawed HAWTs are also observed. An examination of the momentum fluxes behind the turbine demonstrates that the mean flow induced by these vortices entrains a large quantity of momentum from the unperturbed boundary layer flow above the wake. This effect proves to play an even more significant role than turbulence in reintroducing momentum into the wake. In order to comprehend why the VAWT produces these vortices we modify the double-multiple stream-tube model typically used to predict VAWT performance to incorporate crosswind forces. The similarity between VAWT and yawed HAWT wakes is found not to be coincidental as both cases feature rotors which exert a lateral thrust on the incoming wind which leads to the creation of counter-rotating vortex pairs.
Modification of Eye Movements and Motion Perception during Off-Vertical Axis Rotation
Wood, S. J.; Reschke, M. F.; Denise, P.; CLement, G.
2006-01-01
Constant velocity Off-Vertical Axis Rotation (OVAR) imposes a continuously varying orientation of the head and body relative to gravity. The ensuing ocular reflexes include modulation of both torsional and horizontal eye movements as a function of the varying linear acceleration along the lateral plane, and modulation of vertical and vergence eye movements as a function of the varying linear acceleration along the sagittal plane. Previous studies have demonstrated that tilt and translation otolith-ocular responses, as well as motion perception, vary as a function of stimulus frequency during OVAR. The purpose of this study is to examine normative OVAR responses in healthy human subjects, and examine adaptive changes in astronauts following short duration space flight at low (0.125 Hz) and high (0.5 Hz) frequencies. Data was obtained on 24 normative subjects (14 M, 10 F) and 14 (13 M, 1F) astronaut subjects. To date, astronauts have participated in 3 preflight sessions (n=14) and on R+0/1 (n=7), R+2 (n= 13) and R+4 (n= 13) days after landing. Subjects were rotated in darkness about their longitudinal axis 20 deg off-vertical at constant rates of 45 and 180 deg/s, corresponding to 0.125 and 0.5 Hz. Binocular responses were obtained with video-oculography. Perceived motion was evaluated using verbal reports and a two-axis joystick (pitch and roll tilt) mounted on top of a two-axis linear stage (anterior-posterior and medial-lateral translation). Eye responses were obtained in ten of the normative subjects with the head and trunk aligned, and then with the head turned relative to the trunk 40 deg to the right or left of center. Sinusoidal curve fits were used to derive amplitude, phase and bias of the responses over several cycles at each stimulus frequency. Eye responses during 0.125 Hz OVAR were dominated by modulation of torsional and vertical eye position, compensatory for tilt relative to gravity. While there is a bias horizontal slow phase velocity (SPV), the
Park, Barratt; Krueger, Bastian C.; Meyer, Sven; Kandratsenka, Alexander; Wodtke, Alec; Schaefer, Tim
2017-06-01
The conversion of translational to rotational motion often plays a major role in the trapping of small molecules at surfaces, a crucial first step for a wide variety of chemical processes that occur at gas-surface interfaces. However, to date most quantum-state resolved surface scattering experiments have been performed on diatomic molecules, and very little detailed information is available about how the structure of non-linear polyatomic molecules influences the mechanisms for energy exchange with surfaces. In the current work, we employ a new rotationally-resolved 1+1' resonance-enhanced multiphoton ionization (REMPI) scheme to measure rotational distribution in formaldehyde molecules directly scattered from the Au(111) surface at incident kinetic energies in the range 0.3-1.2 eV. The results indicate a pronounced propensity to excite a-axis rotation (twirling) rather than b- or c-axis rotation (tumbling or cartwheeling), and are consistent with a rotational rainbow scattering model. Classical trajectory calculations suggest that the effect arises--to zeroth order--from the three-dimensional shape of the molecule (steric effects). The results have broad implications for the enhanced trapping probability of prolate and near-prolate molecules at surfaces.
On the Measurement and Analysis of Rotation and Spin Axis of LAGEOS and LAGEOS II
Currie, D.; Andres, N.; Noomen, R.
2003-04-01
The University of Maryland has, for the past 15 years, been monitoring the rotation of LAGEOS, LAGEOS II and other satellites by the sun-glint method. This has resulted in the first determination of the orientation of the spin axis, and has provide a history of the motion of the spin. The accuracy ellipse is typically better than 1 degree by 10 degrees, and when two passes are available for the same night, the error ellipse improves to 1 degree by 1 degree. This accuracy has been verified by internal consistency and by the agreement with the model of Andres. The current status of the observations and the method will be presented. The role of the thermal thrust will be addressed on the orbit will be addressed, as well as the effect of the satellite orientation. The relation of these measurement and the thermal thrust to the joint Italian/University of Maryland program for the measurement of the Lense-Thirring will be also discussed.
Rotational kinematics of a rigid body about a fixed axis: development and analysis of an inventory
Mashood, K. K.; Singh, Vijay A.
2015-07-01
We present the development, administration, and analysis of a focused inventory on the rotational kinematics of a rigid body around a fixed axis. The inventory, which is made up of 13 multiple-choice questions, was developed on the basis of interactions with students and teachers. The systematic and iterative aspects of the construction of the inventory are illustrated. The questions, which were validated, were administered to a set of teachers (N = 25) and two groups of preuniversity students (N = 74 and 905) in India. Students, as well as teachers, exhibited difficulties in applying the operational definition of angular velocity to a rigid body. Many erroneously assumed that an angular acceleration cannot exist without a net torque. Patterns of reasoning resulting in errors were identified and categorized under four broad themes. These include inappropriate extensions of familiar procedural practices, reasoning cued by primitive elements in thought, lack of differentiation between related but distinct concepts, and indiscriminate use of equations. The inventory was also administered to introductory-level students (N = 384) at the University of Washington. Popular distractors to most items were similar to the Indian students.
Pueyo, Emilio L.; Oliván, Carlota; Soto, Ruth; Rodríguez-Pintó, Adriana; Santolaria, Pablo; Luzón, Aránzazu; Casas, Antonio M.; Ayala, Conxi
2017-04-01
Vertical axis rotations are common in all deformation settings. At larger scales, for example in fold and thrust belts, they are usually related to differential shortening along strike and this may be caused by a number of reasons (interplay of plate boundaries, sedimentary wedges, detachment level distribution, etc.). At smaller scales, local stress fields, interference of non-coaxial deformation phases, development of non-cylindrical structures, etc. may play an important role to accommodate significant magnitudes of rotation. Apart from their implication in the truly 4D understanding of geological structures, the occurrence of vertical axis rotation usually precludes the application of most 3D restoration techniques and thus, increases the uncertainty in any 3D reconstruction. Salt structures may form in different geological settings, but focusing on compressive regimes, very little is known about the relation between their geometry and kinematics and their ability to accommodate vertical axis rotations (i.e. local or regional lateral gradients of shortening). The Barbastro-Balaguer anticline (BBA) is the southernmost structure of the Central Pyrenees. It is a large detachment fold spreading more than 150 km along the front. In contrast to most frontal Pyrenean structures, the BBA is detached in Priabonian evaporites and was folded during Oligocene times as witnessed by well exposed growth strata. Along strike changes in the fold axis trend may reach 50°, an overall the anticline displays a convex shape towards the foreland (south). A residual Bouguer anomaly map based on a densely sampled gravimetric surveying (10.000 stations) has helped delineating a heterogeneous distribution of the Eocene detachment level in the subsurface. In this contribution we explore the interplay between vertical axis rotations, detachment level distribution and the fold geometry (structural trend and style based on hundreds of data). Seventy paleomagnetic sites evenly and densely
Directory of Open Access Journals (Sweden)
Elisa Danda de Oliveira
2015-03-01
Full Text Available This article describes a practical activity to estimate the angle of inclination of the Earth's rotation axis as a teaching resource with potential to promote the meaningful learning on topics related to astronomy and Earth science. Some topics of interest for carrying out the activity as the apparent movement of the sun, the angle of incidence of sunlight throughout the year and the seasons are discussed. The procedures and materials used in measuring the length of the shadow of a gnomon, the collected data, and the estimating of the angle of inclination of the rotation axis are presented. The article ends with a reflection on the implementation of this activity in elementary and high school level.
Elisa Danda de Oliveira; Letícia Zolet; Odilon Giovannini Junior
2015-01-01
This article describes a practical activity to estimate the angle of inclination of the Earth's rotation axis as a teaching resource with potential to promote the meaningful learning on topics related to astronomy and Earth science. Some topics of interest for carrying out the activity as the apparent movement of the sun, the angle of incidence of sunlight throughout the year and the seasons are discussed. The procedures and materials used in measuring the length of the shadow of a gnomon, th...
Sereno, M; Debiossac, M; Kalashnyk, N; Roncin, P
2016-01-01
A procedure to measure the residual tilt angle $\\tau$ between a flat surface and the azimuthal rotation axis of the sample holder is described. When the incidence angle $\\theta$ and readout of the azimuthal angle $\\phi$ are controlled by motors, an active compensation mechanism can be implemented to reduce the effect of the tilt angle during azimuthal motion. After this correction, the effective angle of incidence is kept fixed, and only the small residual oscillation of the scattering plane remains.
Nanometer-level axis of rotation metrology for a high-precision macromolecular X-ray diffractometer
Knapp, B.; Marsh, E.; Cipriani, F.; Arneson, D.; Oss, D.; Liebers, M.; Keller, E.
2013-03-01
The availability of micro-focused beams at 3rd generation synchrotrons makes collecting X-ray data from macromolecular crystals down to a fraction of micron size possible. This requires using goniometers with nanometer-level errors. Crystal positioning is typically realized with a multi-axis goniometer designed to minimize error motion during rotation of the crystal by the data-collection axis. In this paper, five degree-of-freedom error motions of an air bearing diffractometer data-collection axis are evaluated using a multiprobe method. As spindle errors and artifact out-of-roundness approach equal magnitudes, techniques must be used to distinguish and separate each error. A purpose-built fixture orients a single capacitive sensor in three asymmetrical positions to separate artifact form error from spindle error motion. Metrology results of this air bearing Omega spindle demonstrate synchronous errors of 16 nm radial, 4 nm axial and 0.28 μrad tilt.
Florin, E; Rangwala, H S; Rudin, S
2007-01-01
A magnetic guidance methodology to rotate a device around the catheter axis is proposed. The specific medical application is to intracranial aneurysms. An endovascular device, the asymmetric stent, has a low porosity region that is rotated to cover the aneurysm neck so as to reduce the blood flow into and hence obliterate the aneurysm. The magnetic guidance system consists of a magnetic device attached to the asymmetric stent and an external homogeneous magnetic field of 0.1 T. This magnetic field puts a torque on the magnetic moment of the magnetic device, thereby rotating the stent for proper orientation. For the magnetic device with the required magnetic moment of 0.001 A m2, a cylindrical neodymium permanent magnet is proposed due to its favorable material characteristics while a coil electromagnet with iron core appears impractical due to demagnetizing effects.
Huang, J.; Young, L. R.
1981-01-01
The effects of the oculogyro illusion of the relative motion of a spot fixed with respect to the subject during subject rotation and of a fixed striped peripheral visual field under different levels of illumination on perceptions of rotation about a vertical axis are investigated. Subjects were seated in a rotatable flight trainer cockpit with visual fields consisting of darkness, a dim peripheral field, and a bright peripheral field, all fixed with respect to the subject, and subject perceptual thresholds, frequency responses and sensations of displacement and velocity were measured during trainer rotation at constant and varying angular accelerations. The perception of angular acceleration is found to exhibit a significantly lower threshold and a reduced latency time in the illuminated visual fields which was independent of the level of illumination. Subjective frequency responses showed a higher gain in the illuminated presentations, while subjective displacements during triangular velocity stimuli exhibited no difference for the different visual cues. Finally, magnitude estimations of the after-rotation associated with deceleration from a constant velocity showed a greater rising speed, larger velocity and longer duration under illumination. Results show that, for low accelerations, the visual input enhances sensitivity to self-motion, an effect explained by the oculogyral illusion.
Hopson, R.F.; Hillhouse, J.W.; Howard, K.A.
2008-01-01
Analysis of the strikes of 3841 dikes in 47 domains in the 500-km-long Late Jurassic Independence dike swarm indicates a distribution that is skewed clockwise from the dominant northwest strike. Independence dike swarm azimuths tend to cluster near 325?? ?? 30??, consistent with initial subparallel intrusion along much of the swarm. Dike azimuths in a quarter of the domains vary widely from the dominant trend. In domains in the essentially unrotated Sierra Nevada block, mean dike azimuths range mostly between 300?? and 320??, with the exception of Mount Goddard (247??). Mean dike azimuths in domains in the Basin and Range Province in the Argus, Inyo, and White Mountains areas range from 291?? to 354?? the mean is 004?? in the El Paso Mountains. In the Mojave Desert, mean dike azimuths range from 318?? to 023??, and in the eastern Transverse Ranges, they range from 316?? to 051??. Restoration for late Cenozoic vertical-axis rotations, suggested by paleodeclinations determined from published studies from nearby Miocene and younger rocks, shifts dike azimuths into better agreement with azimuths measured in the tectonically stable Sierra Nevada. This confirms that vertical-axis tectonic rotations explain some of the dispersion in orientation, especially in the Mojave Desert and eastern Transverse Ranges, and that the dike orientations can be a useful if imperfect guide to tectonic rotations where paleomagnetic data do not exist. Large deviations from the main trend of the swarm may reflect (1) clockwise rotations for which there is no paleomagnetic evidence available, (2) dike intrusions of other ages, (3) crack filling at angles oblique or perpendicular to the main swarm, (4) pre-Miocene rotations, or (5) unrecognized domain boundaries between dike localities and sites with paleomagnetic determinations. ?? 2008 The Geological Society of America.
Development of a Low-Cost Attitude and Heading Reference System Using a Three-Axis Rotating Platform
Directory of Open Access Journals (Sweden)
Fei-Bin Hsiao
2010-03-01
Full Text Available A development procedure for a low-cost attitude and heading reference system (AHRS with a self-developed three-axis rotating platform has been proposed. The AHRS consists of one 3-axis accelerometer, three single-axis gyroscopes, and one 3-axis digital compass. Both the accelerometer and gyroscope triads are based on micro electro-mechanical system (MEMS technology, and the digital compass is based on anisotropic-magnetoresistive (AMR technology. The calibrations for each sensor triad are readily accomplished by using the scalar calibration and the least squares methods. The platform is suitable for the calibration and validation of the low-cost AHRS and it is affordable for most laboratories. With the calibrated parameters and data fusion algorithm for the orientation estimation, the self-developed AHRS demonstrates the capabilities of compensating for the sensor errors and outputting the estimated orientation in real-time. The validation results show that the estimated orientations of the developed AHRS are within the acceptable region. This verifies the practicability of the proposed development procedure.
Lai, Ying-Chih; Jan, Shau-Shiun; Hsiao, Fei-Bin
2010-01-01
A development procedure for a low-cost attitude and heading reference system (AHRS) with a self-developed three-axis rotating platform has been proposed. The AHRS consists of one 3-axis accelerometer, three single-axis gyroscopes, and one 3-axis digital compass. Both the accelerometer and gyroscope triads are based on micro electro-mechanical system (MEMS) technology, and the digital compass is based on anisotropic-magnetoresistive (AMR) technology. The calibrations for each sensor triad are readily accomplished by using the scalar calibration and the least squares methods. The platform is suitable for the calibration and validation of the low-cost AHRS and it is affordable for most laboratories. With the calibrated parameters and data fusion algorithm for the orientation estimation, the self-developed AHRS demonstrates the capabilities of compensating for the sensor errors and outputting the estimated orientation in real-time. The validation results show that the estimated orientations of the developed AHRS are within the acceptable region. This verifies the practicability of the proposed development procedure.
Konosevich, B. I.
2014-07-01
The error of the Wentzel-Kramers-Brillouin solution of the equations describing the angular motion of the axis of symmetry of rotation of a rigid body (projectile) is estimated. It is established that order of this estimate does not depend on whether the low-frequency oscillations of the axis of symmetry are damped or not
Dai, M.; Raphan, T.; Kozlovskaya, I.; Cohen, B.
1996-01-01
Horizontal movements of both eyes were recorded simultaneously using scleral search coils in 2 rhesus monkeys before and after the COSMOS 2229 space-flight of 1992-1993. Another 9 monkeys were tested at comparable time intervals and served as controls. Ocular vergence, defined as the difference in horizontal position between the left and right eyes, was measured during off-vertical yaw axis rotation (OVAR) in darkness. Vergence was modulated sinusoidally as a function of head position with regard to gravity during OVAR. The amplitude of peak-to-peak modulation increased with increments in tilt of the angle of the rotational axis (OVAR tilt angle) that ranged from 15 degrees to 90 degrees. Of the 11 monkeys tested, 1 had no measurable modulation in vergence. In the other 10, the mean amplitude of the peak to peak modulation was 5.5 degrees +/- 1.3 degrees at 90 degrees tilt. Each of these monkeys had maximal vergence when its nose was pointed close to upward (gravity back; mean phase: -0.9 degree +/- 26 degrees). After space flight, the modulation in vergence was reduced by over 50% for the two flight monkeys, but the phase of vergence modulation was not altered. The reduction in vergence modulation was sustained for the 11-day postflight testing period. We conclude that changes in vergence are induced in monkeys by the sinusoidal component of gravity acting along the naso-occipital axis during yaw axis OVAR, and that the modulation of the vergence reflex is significantly less sensitive to linear acceleration after space flight.
Live-Axis Turning for the Fabrication of Non-Rotationally Symmetric Optics Project
National Aeronautics and Space Administration — The goal of this proposal is to develop a new method to create Non-Rotationally Symmetric (NRS) surfaces that overcomes the limitations of the current techniques and...
Wood, Scott; Clement, Gilles; Denise, Pierre; Reschke, Millard
2005-01-01
Constant velocity Off-Vertical Axis Rotation (OVAR) imposes a continuously varying orientation of the head and body relative to gravity. The ensuing ocular reflexes include modulation of both horizontal and torsional eye velocity as a function of the varying linear acceleration along the lateral plane. The purpose of this study was to examine whether the modulation of these ocular reflexes would be modified by different head-on-trunk positions. Ten human subjects were rotated in darkness about their longitudinal axis 20 deg off-vertical at constant rates of 45 and 180 deg/s, corresponding to 0.125 and 0.5 Hz. Binocular responses were obtained with video-oculography with the head and trunk aligned, and then with the head turned relative to the trunk 40 deg to the right or left of center. Sinusoidal curve fits were used to derive amplitude, phase and bias velocity of the eye movements across multiple cycles for each head-on-trunk position. Consistent with previous studies, the modulation of torsional eye movements was greater at 0.125 Hz while the modulation of horizontal eye movements was greater at 0.5 Hz. Neither amplitude nor bias velocities were significantly altered by head-on-trunk position. The phases of both torsional and horizontal ocular reflexes, on the other hand, shifted towards alignment with the head. These results are consistent with the modulation of torsional and horizontal ocular reflexes during OVAR being primarily mediated by the otoliths in response to the sinusoidally varying linear acceleration along the interaural head axis.
Kanner, Samuel Adam Chinman
The design and operation of two counter-rotating vertical-axis wind turbines on a floating, semi-submersible platform is studied. The technology, called the Multiple Integrated and Synchronized Turbines (MIST) platform has the potential to reduce the cost of offshore wind energy per unit of installed capacity. Attached to the platform are closely-spaced, counter-rotating turbines, which can achieve a higher power density per planform area because of synergistic interaction effects. The purpose of the research is to control the orientation of the platform and rotational speeds of the turbines by modifying the energy absorbed by each of the generators of the turbines. To analyze the various aspects of the platform and wind turbines, the analysis is drawn from the fields of hydrodynamics, electromagnetics, aerodynamics and control theory. To study the hydrodynamics of the floating platform in incident monochromatic waves, potential theory is utilized, taking into account the slow-drift yaw motion of the platform. Steady, second-order moments that are spatially dependent (i.e., dependent on the platform's yaw orientation relative to the incident waves) are given special attention since there are no natural restoring yaw moment. The aerodynamics of the counter-rotating turbines are studied in collaboration with researchers at the UC Berkeley Mathematics Department using a high-order, implicit, large-eddy simulation. An element flipping technique is utilized to extend the method to a domain with counter-rotating turbines and the effects from the closely-spaced turbines is compared with existing experimental data. Hybrid testing techniques on a model platform are utilized to prove the controllability of the platform in lieu of a wind-wave tank. A 1:82 model-scale floating platform is fabricated and tested at the UC Berkeley Physical-Model Testing Facility. The vertical-axis wind turbines are simulated by spinning, controllable actuators that can be updated in real-time of
Dimitroff, C.; Housen, B. A.; McNabb, J. C.; Dorsey, R. J.; Burmester, R. F.; Messe, G. T.
2015-12-01
Here, we report new paleomagnetism and magnetostratigraphy data from the Palm Spring Fm of the Mecca Hills, the Pleistocene conglomeratic sandstone in Desert Hot Springs and the Plio-Pleistocene San Timoteo beds from Live Oak Canyon. From the Mecca Hills, new data are from 29 sites and 112 samples. The paleomagnetic results yielded well-defined components of magnetization- defining seven polarity zones within the Ocotillo and upper Palm Spring Fm. Correlation to the geomagnetic polarity timescale, using the Bishop Ash near the top of the section as a tie point, places the Brunhes-Matuyama boundary near the base of the Ocotillo Fm, and the Jaramillo, Olduvai, and Reunion normal polarity sub-chrons in the upper Palm Spring Fm. This indicates the upper Palm Spring Fm in the Mecca Hills was deposited between 2.3 and 0.9 Ma. Sites from the Mecca Hills section have mean directions of D = 343, I = 53, α95 =11.3 N = 5 for normal sites, D = 175, I = -50, α95 = 4.9 N = 24 for reverse sites, and normal and reverse sites combined have a mean direction of D = 353, I = 51 α95 = 4.4. This indicates modest (7 degrees) CCW rotation of the section. Results from 19 sites (53 samples) of the Pleistocene conglomeritic sandstone from Desert Hot Springs have very well-defined paleomagnetic components. Six of the sites have normal polarity- 13 sites have reverse polarity. Sites with normal polarity have a mean direction of D = 358, I = 45, α95 = 13 and reverse sites have a mean of D = 182, I = -50, α95 = 6.6.The combined mean direction (in tilt-corrected coordinates) is D = 0.7, I = 49, α95 = 5.6 and indicates that 3.1° ± 2.3° of CW rotation has occurred at this location since ~1 to 1.5 Ma. Results from 8 sites (35 samples) of the upper-most San Timoteo beds from Live Oak Canyon also have well-defined paleomagnetic components for 6 sites. All of the results have normal polarity, and one site has a direction that is >40 degree from the other sites- the mean of the remaining 5
Naito, Kozo; Takagi, Hiroyasu; Yamada, Norimasa; Hashimoto, Shinichi; Maruyama, Takeo
2014-12-01
The shoulder internal rotation (IR) and forearm pronation (PR) are important elements for baseball pitching, however, how rapid rotations of IR and PR are produced by muscular torques and inter-segmental forces is not clear. The aim of this study is to clarify how IR and PR angular velocities are maximized, depending on muscular torque and interactive torque effects, and gain a detailed knowledge about inter-segmental interaction within a multi-joint linked chain. The throwing movements of eight collegiate baseball pitchers were recorded by a motion capture system, and induced-acceleration analysis was used to assess the respective contributions of the muscular (MUS) and interactive torques associated with gyroscopic moment (GYR), and Coriolis (COR) and centrifugal forces (CEN) to maximum angular velocities of IR (MIRV) and PR (MPRV). The results showed that the contribution of MUS account for 98.0% of MIRV, while that contribution to MPRV was indicated as negative (-48.1%). It was shown that MPRV depends primarily on the interactive torques associated with GYR and CEN, but the effects of GYR, COR and CEN on MIRV are negligible. In conclusion, rapid PR motion during pitching is created by passive-effect, and is likely a natural movement which arises from 3D throwing movement. Applying the current analysis to IR and PR motions is helpful in providing the implications for improving performance and considering conditioning methods for pitchers.
Edirisinghe, Y; Troupis, J M; Patel, M; Smith, J; Crossett, M
2014-05-01
We used a dynamic three-dimensional (3D) mapping method to model the wrist in dynamic unrestricted dart throwers motion in three men and four women. With the aid of precision landmark identification, a 3D coordinate system was applied to the distal radius and the movement of the carpus was described. Subsequently, with dynamic 3D reconstructions and freedom to position the camera viewpoint anywhere in space, we observed the motion pathways of all carpal bones in dart throwers motion and calculated its axis of rotation. This was calculated to lie in 27° of anteversion from the coronal plane and 44° of varus angulation relative to the transverse plane. This technique is a safe and a feasible carpal imaging method to gain key information for decision making in future hand surgical and rehabilitative practices.
Colle, Francesca; Lopomo, Nicola; Visani, Andrea; Zaffagnini, Stefano; Marcacci, Maurilio
2016-01-01
Estimating the main axis of rotation (AoR) of a human joint represents an important issue in biomechanics. This study compared three formal methods used to estimate functional AoR, namely a cylindrical fitting method, a mean helical axis transformation, and a symmetrical axis approach. These methods were tested on 106 subjects undergoing navigated total knee arthroplasty. AoR orientation in 3D and in the frontal and coronal planes provided by each method was compared to the transepicondylar axis direction. Although all the methods resulted effective, significant differences were identified among them, relatively to the orientation in 3D and in the frontal plane projection. This was probably due to the presence of secondary rotations during the first degrees of knee flexion.
Tian, W.
2016-07-01
Ring laser gyroscope technique directly senses the Earth's instantaneous rotation pole (IRP), whose polar motion contains strong retrograde diurnal components induced by external torques due to the gravitational attraction of the Moon and Sun. The first direct measurement of this retrograde diurnal motion with three large ring lasers was reported by Schreiber et al. (J Geophys Res 109(B18):B06405, 2004). Since then many technical improvements led to a significant increase in precision and stability of ring laser gyroscopes; however, precise determination of amplitude and phase at main partial waves has not been given in the literature. In this paper, I will report on determination of the retrograde diurnal motion of the IRP at main partial waves (Oo_1, J_1, K_1, M_1, O_1, Q_1 ) by the ring laser "G", located in Wettzell, Germany, which is the most stable one amongst the currently running large ring laser gyroscopes.
Tian, W.
2017-01-01
Ring laser gyroscope technique directly senses the Earth's instantaneous rotation pole (IRP), whose polar motion contains strong retrograde diurnal components induced by external torques due to the gravitational attraction of the Moon and Sun. The first direct measurement of this retrograde diurnal motion with three large ring lasers was reported by Schreiber et al. (J Geophys Res 109(B18):B06405, significant increase in precision and stability of ring laser gyroscopes; however, precise determination of amplitude and phase at main partial waves has not been given in the literature. In this paper, I will report on determination of the retrograde diurnal motion of the IRP at main partial waves (Oo_1, J_1, K_1, M_1, O_1, Q_1) by the ring laser "G", located in Wettzell, Germany, which is the most stable one amongst the currently running large ring laser gyroscopes.
Yang, Xiaogang; De Carlo, Francesco; Phatak, Charudatta; Gürsoy, Dogˇa
2017-03-01
This paper presents an algorithm to calibrate the center-of-rotation for X-ray tomography by using a machine learning approach, the Convolutional Neural Network (CNN). The algorithm shows excellent accuracy from the evaluation of synthetic data with various noise ratios. It is further validated with experimental data of four different shale samples measured at the Advanced Photon Source and at the Swiss Light Source. The results are as good as those determined by visual inspection and show better robustness than conventional methods. CNN has also great potential for reducing or removing other artifacts caused by instrument instability, detector non-linearity, etc. An open-source toolbox, which integrates the CNN methods described in this paper, is freely available through GitHub at tomography/xlearn and can be easily integrated into existing computational pipelines available at various synchrotron facilities. Source code, documentation and information on how to contribute are also provided.
Model tests of wind turbine with a vertical axis of rotation type Lenz 2
Directory of Open Access Journals (Sweden)
Zwierzchowski Jaroslaw
2017-01-01
Full Text Available A building design of vertical axis wind turbines (VAWT was presented in the article. The construction and operating principle of a wind turbine were described therein. Two VAWT turbine models were compared, i.a. Darrieus and Lenz2, taking their strengths and weaknesses into consideration. 3D solid models of turbine components were presented with the use of SolidWorks software. Using CFD methods, the air flow on two aerodynamic fins, symmetrical and asymmetrical, at different angles of attack were tested. On the basis of flow simulation conducted in FlowSimulation, an asymmetrical fin was chosen as the one showing greater load bearing capacities. Due to the uncertainty of trouble-free operation of Darrieus turbine on construction elements creating the basis thereof, a 3D model of Lenz2 turbine was constructed, which is more reliable and makes turbine self-start possible. On the basis of the research, components were designed and technical docu mentation was compiled.
Energy Technology Data Exchange (ETDEWEB)
Yang, Xiaogang; De Carlo, Francesco; Phatak, Charudatta; Gürsoy, Dogˇa
2017-01-24
This paper presents an algorithm to calibrate the center-of-rotation for X-ray tomography by using a machine learning approach, the Convolutional Neural Network (CNN). The algorithm shows excellent accuracy from the evaluation of synthetic data with various noise ratios. It is further validated with experimental data of four different shale samples measured at the Advanced Photon Source and at the Swiss Light Source. The results are as good as those determined by visual inspection and show better robustness than conventional methods. CNN has also great potential for
Institute of Scientific and Technical Information of China (English)
LIU Hui-liang; JIN Zhi-geng; YANG Sheng-li; LUO Jian-ping; MA Dong-xing; LIU Ying; HAN Wei
2012-01-01
Background Dual-axis rotational coronary angiography (DARCA) was developed as an innovative adaptation of rotational angiography (RA),but it requires a longer coronary injection compared to standard coronary angiography (SA).As the body of the average Chinese patient is smaller than that of most western patients,with the same contrast injection time,the risk of complications from the contrast agent is increased in this population.The purpose of this study was to assess the clinical safety and efficacy of DARCA in the diagnosis of coronary artery disease (CAD) in the Chinese population by directly comparing it to SA.Methods Two hundred Chinese patients were randomized to either the SA group (n=100) or DARCA group (n=100).Contrast utilization,radiation exposure and procedure time were recorded for each modalities.Blood pressure (BP),heart rate (HR) pre and post injection symptoms and any arrhythmias were recorded.Results Compared to the SA group,there was a 42％ reduction in contrast utilization,55％ reduction in radiation exposure and a 31％ shorter procedure time in the DARCA group.In both groups,there were slight declines in the systolic BP values in the left coronary artery (LCA) post injection (P ＜0.01).Moreover,post injection HRs for the LCA were also reduced in the DARCA group (P ＜0.01).But all of these changes were small,transient and without clinical importance.Only one patient (1％) in the DARCA group had an attack of ventricular tachycardia immediately post injection and it resolved by itself during LCA angiography.No arrhythmias occurred in the SA group.Conclusion DARCA is a safe,efficient,and clinically comparable altemative to SA in the diagnosis of coronary artery disease in the Chinese population with less contrast utilized,which is less radiation exposure and a shorter procedure time than SA.
Zhu, Jing; Wang, Xingshu; Wang, Jun; Dai, Dongkai; Xiong, Hao
2016-10-01
Former studies have proved that the attitude error in a single-axis rotation INS/GPS integrated system tracks the high frequency component of the deflections of the vertical (DOV) with a fixed delay and tracking error. This paper analyses the influence of the nominal process noise covariance matrix Q on the tracking error as well as the response delay, and proposed a Q-adjusting technique to obtain the attitude error which can track the DOV better. Simulation results show that different settings of Q lead to different response delay and tracking error; there exists optimal Q which leads to a minimum tracking error and a comparatively short response delay; for systems with different accuracy, different Q-adjusting strategy should be adopted. In this way, the DOV estimation accuracy of using the attitude error as the observation can be improved. According to the simulation results, the DOV estimation accuracy after using the Q-adjusting technique is improved by approximate 23% and 33% respectively compared to that of the Earth Model EGM2008 and the direct attitude difference method.
Analysis of response delay of the attitude in a single-axis rotation INS/GPS system
Zhu, Jing; Wang, Xingshu; Wang, Jun; Dai, Dongkai; Xiong, Hao
2016-01-01
Deflections of the vertical (DOV) are normally ignored in the gravity compensation procedure, which become one of the primary error sources in inertial navigation. In a single-axis rotation INS/GPS system, bias of the gyro and the accelerometer can be ignored, the attitude error is mainly affected by DOV. In this paper, the ideal system assumption is abandoned and the influence of DOV on the attitude is comprehensively discussed, which can be divided into two parts i.e. the direct influence and the indirect influence. The attitude error tracks the DOV along the trajectory belongs to the former. A relatively fixed delay between the attitude error and the DOV belongs to the latter. The delay is essentially induced by the weak observability of the system to the violent DOV. Factors which affect the delay are carefully analyzed. The simulation results show that the delay is mainly affected by accuracies of the inertial sensors and the GPS. It decreases with the GPS accuracy increasing, but increases with the inertial sensor accuracy increasing. The process noise covariance matrix Q plays an important role. With analysis of the characteristics of the delay, influence of the DOV on attitude is studied further, which is necessary for the attitude correction in future.
Directory of Open Access Journals (Sweden)
Kelly N. Salb
2016-01-01
Full Text Available Ankle instantaneous axis of rotation (IAR measurements represent a more complete parameter for characterizing joint motion. However, few studies have implemented this measurement to study normal, injured, or pathological foot ankle biomechanics. A novel testing protocol was developed to simulate aspects of in vivo foot ankle mechanics during mid-stance gait in a human cadaveric specimen. A lower leg was mounted in a robotic testing platform with the tibia upright and foot flat on the baseplate. Axial tibia loads (ATLs were controlled as a function of a vertical ground reaction force (vGRF set at half body weight (356 N and a 50% vGRF (178 N Achilles tendon load. Two specimens were repetitively loaded over 10 degrees of dorsiflexion and 20 degrees of plantar flexion. Platform axes were controlled within 2 microns and 0.008 degrees resulting in ATL measurements within ±2 N of target conditions. Mean ATLs and IAR values were not significantly different between cycles of motion, but IAR values were significantly different between dorsiflexion and plantar flexion. A linear regression analysis showed no significant differences between slopes of plantar flexion paths. The customized robotic platform and advanced testing protocol produced repeatable and accurate measurements of the IAR, useful for assessing foot ankle biomechanics under different loading scenarios and foot conditions.
Clement, Gilles; Denise, Pierre; Reschke, Millard; Wood, Scott J.
2007-01-01
Ocular counter-rolling (OCR) induced by whole body tilt in roll has been explored after spaceflight as an indicator of the adaptation of the otolith function to microgravity. It has been claimed that the overall pattern of OCR responses during static body tilt after spaceflight is indicative of a decreased role of the otolith function, but the results of these studies have not been consistent, mostly due to large variations in the OCR within and across individuals. By contrast with static head tilt, off-vertical axis rotation (OVAR) presents the advantage of generating a sinusoidal modulation of OCR, allowing averaged measurements over several cycles, thus improving measurement accuracy. Accordingly, OCR and the sense of roll tilt were evaluated in seven astronauts before and after spaceflight during OVAR at 45 /s in darkness at two angles of tilt (10 and 20 ). There was no significant difference in OCR during OVAR immediately after landing compared to preflight. However, the amplitude of the perceived roll tilt during OVAR was significantly larger immediately postflight, and then returned to control values in the following days. Since the OCR response is predominantly attributed to the shearing force exerted on the utricular macula, the absence of change in OCR postflight suggests that the peripheral otolith organs function normally after short-term spaceflight. However, the increased sense of roll tilt indicates an adaptation in the central processing of gravitational input, presumably related to a re-weigthing of the internal representation of gravitational vertical as a result of adaptation to microgravity.
Wood, Scott J.; Paloski, W. H. (Principal Investigator)
2002-01-01
The purpose of this study was to examine how the modulation of tilt and translation otolith-ocular responses during constant velocity off-vertical axis rotation varies as a function of stimulus frequency. Eighteen human subjects were rotated in darkness about their longitudinal axis 30 degrees off-vertical at stimulus frequencies between 0.05 and 0.8 Hz. The modulation of torsion decreased while the modulation of horizontal slow phase velocity (SPV) increased with increasing frequency. It is inferred that the ambiguity of otolith afferent information is greatest in the frequency region where tilt (torsion) and translational (horizontal SPV) otolith-ocular responses crossover. It is postulated that the previously demonstrated peak in motion sickness susceptibility during linear accelerations around 0.3 Hz is the result of frequency segregation of ambiguous otolith information being inadequate to distinguish between tilt and translation.
Grip, Helena; Sundelin, Gunnevi; Gerdle, Björn; Stefan Karlsson, J
2008-09-18
The helical axis model can be used to describe translation and rotation of spine segments. The aim of this study was to investigate the cervical helical axis and its center of rotation during fast head movements (side rotation and flexion/extension) and ball catching in patients with non-specific neck pain or pain due to whiplash injury as compared with matched controls. The aim was also to investigate correlations with neck pain intensity. A finite helical axis model with a time-varying window was used. The intersection point of the axis during different movement conditions was calculated. A repeated-measures ANOVA model was used to investigate the cervical helical axis and its rotation center for consecutive levels of 15 degrees during head movement. Irregularities in axis movement were derived using a zero-crossing approach. In addition, head, arm and upper body range of motion and velocity were observed. A general increase of axis irregularity that correlated to pain intensity was observed in the whiplash group. The rotation center was superiorly displaced in the non-specific neck pain group during side rotation, with the same tendency for the whiplash group. During ball catching, an anterior displacement (and a tendency to an inferior displacement) of the center of rotation and slower and more restricted upper body movements implied a changed movement strategy in neck pain patients, possibly as an attempt to stabilize the cervical spine during head movement.
Inamori, Takaya; Otsuki, Kensuke; Sugawara, Yoshiki; Saisutjarit, Phongsatorn; Nakasuka, Shinichi
2016-11-01
This study proposes a novel method for three-axis attitude control using only magnetic torquers (MTQs). Previously, MTQs have been utilized for attitude control in many low Earth orbit satellites. Although MTQs are useful for achieving attitude control at low cost and high reliability without the need for propellant, these electromagnetic coils cannot be used to generate an attitude control torque about the geomagnetic field vector. Thus, conventional attitude control methods using MTQs assume the magnetic field changes in an orbital period so that the satellite can generate a required attitude control torque after waiting for a change in the magnetic field direction. However, in a near magnetic equatorial orbit, the magnetic field does not change in an inertial reference frame. Thus, satellites cannot generate a required attitude control torque in a single orbital period with only MTQs. This study proposes a method for achieving a rotation about the geomagnetic field vector by generating a torque that is perpendicular to it. First, this study shows that the three-axis attitude control using only MTQs is feasible with a two-step rotation. Then, the study proposes a method for controlling the attitude with the two-step rotation using a PD controller. Finally, the proposed method is assessed by examining the results of numerical simulations.
Precession Relaxation of Viscoelastic Oblate Rotators
Frouard, Julien
2016-01-01
Various perturbations (collisions, close encounters, YORP) destabilise the rotation of a small body, leaving it in a non-principal spin state. Then the body experiences alternating stresses generated by the inertial forces. The ensuing inelastic dissipation reduces the kinetic energy, without influencing the angular momentum. This yields nutation relaxation, i.e., evolution of the spin towards rotation about the maximal-inertia axis. Knowledge of the timescales needed to damp the nutation is crucial in studies of small bodies' dynamics. In the past, nutation relaxation has been described by an empirical quality factor introduced to parameterise the dissipation rate and to evade the discussion of the actual rheological parameters and their role in dissipation. This approach is unable to describe the dependence of the relaxation rate upon the nutation angle, because we do not know the quality factor's dependence on the frequency (which is a function of the nutation angle). This leaves open the question of relax...
Pueyo Anchuela, Ó.; Pueyo, E. L.; Pocoví Juan, A.; Gil Imaz, A.
2012-04-01
Geometry and kinematics of fold-and-thrust belts can be complex settings when oblique structures and vertical-axis rotations (VAR) take place during thrust emplacement. Many techniques can be used to unravel such complex tectonic histories, from classic ones like strain analysis and changes of paleocurrents, to more modern approaches such as paleomagnetism and calcite twin analysis. In this paper, anisotropy of magnetic susceptibility is compared to vertical axis rotations deduced from paleomagnetic data along three cross-sections in the External Sierras and the Jaca Basin (southwestern Pyrenees). These data enable us to state that: 1) AMS represents pre-tilting deformation fabrics and magnetic lineation behaves like a passive marker during later deformation; and 2) a primary record of the paleomagnetic field can be found in the area. Therefore, the difference with the paleomagnetic reference is the local VAR. The comparison of the two datasets allows us to draw the following conclusions: A) the changes in both paleomagnetic VAR and magnetic lineation orientation between neighbouring sites are similar; and B) there is a significant linear regression between VAR and trend changes in magnetic lineation. Deviations in magnetic lineation with respect to the expected local magnetic lineation permit vertical axis rotations to be quantified using the AMS dataset. The combined analysis of paleomagnetic and AMS data enables: 1) a quicker comparison of the kinematic evolution in areas with similar AMS patterns; 2) the identification of anomalous orientations of magnetic lineation linked to VARs; and 3) the use of AMS analysis as a homogeneity test for VARs determined from other techniques. AMS is proposed as a suitable preliminary technique to select further sites for paleomagnetic analysis since paleomagnetic laboratory procedures are much more time-consuming than AMS measurements, AMS does not usually modify sample remanence and hence samples can be used for both types of
Fazzito, Sabrina Y.; Rapalini, Augusto E.; Cortés, José M.; Terrizzano, Carla M.
2016-05-01
Palaeomagnetic data from poorly consolidated to non-consolidated late Cenozoic sediments along the central segment of the active El Tigre Fault (Central-Western Precordillera of the San Juan Province, Argentina) demonstrate broad cumulative deformation up to ~450 m from the fault trace and reveal clockwise and anticlockwise vertical-axis rotations of variable magnitude. This deformation has affected in different amounts Miocene to late Pleistocene samples and indicates a complex kinematic pattern. Several inherited linear structures in the shear zone that are oblique to the El Tigre Fault may have acted as block boundary faults. Displacement along these faults may have resulted in a complex pattern of rotations. The maximum magnitude of rotation is a function of the age of the sediments sampled, with largest values corresponding to middle Miocene-lower Pliocene deposits and minimum values obtained from late Pleistocene deposits. The kinematic study is complemented by low-field anisotropy of magnetic susceptibility data to show that the local strain regime suggests a N-S stretching direction, subparallel to the strike of the main fault.
Baland, Rose-Marie; Yseboodt, Marie; Van Hoolst, Tim; Rivoldini, Attilio
2016-10-01
Mercury's spin axis occupies the Cassini state 1, in which the orbit normal and spin axis precess together with a long period of about 300 000 years. An accurate model of the Cassini state is needed to get a reliable estimate of its polar moment of inertia from the measured orientation of its spin axis. The polar moment of inertia provides a strong constraint on the interior structure. For long, it has been assumed that Mercury precesses as a solid body, meaning that the estimate of the polar moment of inertia may be inaccurate. Recently, there has been renewed interest for the topic, because of the recent determination of Mercury's rotation state (Earth-based radar observations, MESSENGER data), as well as the possibility of future more accurate measurements with the BepiColombo mission.Here, we revisit the influence of the liquid outer core, solid inner core, and precession of the pericenter (period of about 127 000 years). Previous studies have concluded that those effects may have an influence above or up to about an order of magnitude below the present uncertainty on the obliquity. We consider three-layer interior models with a mantle (including the crust), a liquid outer core and a solid inner core. Those models are constrained by the mass, radius, second-degree gravity field coefficients and libration amplitude. We adapt to Mercury a Cassini state model previously developed for synchronous satellites, in which we express the spin axis motion in a frame based on the Laplace plane. We take into account the solar gravitational torque exerted on each layer, the internal gravitational torques between the internal layers and the pressure torques as well as the dissipative viscous torques exerted at the interfaces. We reassess the effect of tidal periodic deformations on the torques, currently thought to be two orders of magnitude below the present uncertainty on the spin orientation determination. Finally, we use the current rotation data to constrain Mercury
Henry, Bernard; Rouvier, Henri; Le Goff, Maxime
2004-06-01
Classical progressive unfolding makes a distinction between pre-folding, post-folding or synfolding magnetization. It yields the direction of magnetization only in the two first cases. To determine the direction of synfolding magnetization, possible different unfolding percentages during remagnetization have to be assumed according to the site. The small circle approach of Surmont et al. not only leads to this direction, but also to the dip value at each site during remagnetization. In the Cévennes area, extensive palaeomagnetic study reveals syntectonic remagnetization enabling the reconstruction of the shape of a fold for the time of the magnetic overprinting as well as analysis of the rotations undergone by some sites after the remagnetization.
Akimoto, Hiromichi; Hara, Yutaka; Kawamura, Takafumi; Nakamura, Takuju; Lee, Yeon-Seung
2013-12-01
In a vertical axis wind turbine (VAWT), turbine blades are subjected to the curved flow field caused by the revolution of turbine. However, performance prediction of VAWT is usually based on the fluid dynamic coefficients obtained in wind tunnel measurements of the two-dimensional static wing. The difference of fluid dynamic coefficients in the curved flow and straight flow deteriorates the accuracy of performance prediction. To find the correlation between the two conditions of curved and straight flow, the authors propose a conformal mapping method on complex plane. It provides bidirectional mapping between the two flow fields. For example, the flow around a symmetric wing in the curved flow is mapped to that around a curved (cambered) wing in the straight flow. Although the shape of mapped wing section is different from the original one, its aerodynamic coefficients show a good correlation to those of the original in the rotating condition. With the proposed method, we can reproduce the local flow field around a rotating blade from the flow data around the mapped static wing in the straight flow condition.
Massire, Aurélien; Cloos, Martijn A; Vignaud, Alexandre; Le Bihan, Denis; Amadon, Alexis; Boulant, Nicolas
2013-05-01
At ultra-high magnetic field (≥ 7T), B1 and ΔB0 non-uniformities cause undesired inhomogeneities in image signal and contrast. Tailored radiofrequency pulses exploiting parallel transmission have been shown to mitigate these phenomena. However, the design of large flip angle excitations, a prerequisite for many clinical applications, remains challenging due the non-linearity of the Bloch equation. In this work, we explore the potential of gradient ascent pulse engineering to design non-selective spin-echo refocusing pulses that simultaneously mitigate severe B1 and ΔB0 non-uniformities. The originality of the method lays in the optimization of the rotation matrices themselves as opposed to magnetization states. Consequently, the commonly used linear class of large tip angle approximation can be eliminated from the optimization procedure. This approach, combined with optimal control, provides additional degrees of freedom by relaxing the phase constraint on the rotation axis, and allows the derivative of the performance criterion to be found analytically. The method was experimentally validated on an 8-channel transmit array at 7T, using a water phantom with B1 and ΔB0 inhomogeneities similar to those encountered in the human brain. For the first time in MRI, the rotation matrix itself on every voxel was measured by using Quantum Process Tomography. The results are complemented with a series of spin-echo measurements comparing the proposed method against commonly used alternatives. Both experiments confirm very good performance, while simultaneously maintaining a low energy deposition and pulse duration compared to well-known adiabatic solutions. Copyright © 2013 Elsevier Inc. All rights reserved.
Rotation of cometary meteoroids
Čapek, D.
2014-08-01
Aims: The rotation of meteoroids caused by gas drag during the ejection from a cometary nucleus has not been studied yet. The aim of this study is to estimate the rotational characteristics of meteoroids after their release from a comet during normal activity. Methods: The basic dependence of spin rate on ejection velocity and meteoroid size is determined analytically. A sophisticated numerical model is then applied to meteoroids ejected from the 2P/Encke comet. The meteoroid shapes are approximated by polyhedrons, which have been determined by a 3D laser scanning method of 36 terrestrial rock samples. These samples come from three distinct sets with different origins and characteristics, such as surface roughness or angularity. Two types of gas-meteoroid interactions and three gas ejection models are assumed. The rotational characteristics of ejected meteoroid population are obtained by numerical integration of equations of motion with random initial conditions and random shape selection. Results: It is proved that the results do not depend on a specific set of shape models and that they are applicable to the (unknown) shapes of real meteoroids. A simple relationship between the median of meteoroid spin frequencies bar{f} (Hz), ejection velocities vej (m s-1), and sizes D (m) is determined. For diffuse reflection of gas molecules from meteoroid's surface it reads as bar{f≃ 2× 10-3 v_ej D-0.88}, and for specular reflection of gas molecules from meteoroid's surface it is bar{f≃ 5× 10-3 v_ej D-0.88}. The distribution of spin frequencies is roughly normal on log scale, and it is relatively wide: a 2σ-interval can be described as (0.1, 10)× bar{f}. Most of the meteoroids are non-principal axis rotators. The median angle between angular momentum vector and spin vector is 12°. About 60% of meteoroids rotate in long-axis mode. The distribution of angular momentum vectors is not random. They are concentrated in the perpendicular direction with respect to the gas
Jacobson, Seth A.; Scheeres, D. J.
2012-05-01
Many comet nuclei have been identified or are suspected to occupy non-principal axis (complex) rotation [Belton 2005, etc.] as well as have evolving rotation rates [Belton 2011, etc.]. Active areas of the surface and jets torque the nucleus during perihelion passage, while time variable internal stresses dissipate energy in the anelastic comet interior. These competing processes determine the comet’s nuclear rotation state. We developed a model for the evolution of the nuclei due to the reactive torques of a number of discrete jets located on the surface based on Neishtadt et al. [2002]. These jets are active only within a specific distance of the sun according to an empirical law determined by Marsden et al. (1973), however internal dissipation occurs as long as the body is not rotating about a principal axis. This internal dissipation is modeled according to Sharma et al. [2005] and Vokrouhlicky et al. [2009]. We average the full evolutionary equations over the rapidly changing spin angle, precession angle and true anomaly of the orbit. The averaged equations can rapidly calculate the long-term evolution of the nutation angle, cone angle and magnitude of the angular momentum vector over many perihelion passages. The averaged dynamical system is characterized by just two parameters: the first encapsulating the jet geometry and the second the coefficient of energy dissipation. Neishtadt et al. [2002] determined that there exist non-principal axis rotation fixed points, some even stable, for certain jet geometries. With the addition of internal dissipation, some of these fixed points disappear, while others remain but may change locations and classification as a function of the strength of energy dissipation at constant jet geometry. We explore this model of comet nuclei evolution to determine the rotation state of comet nuclei with changing jet geometries and constant coefficients of energy dissipation.
Petronis, M. S.; Grondin, D.; Castillo, G., Sr.; Shields, S.; Lindline, J.; Romero, B.; Pluhar, C. J.
2016-12-01
Deformation between the North American and Pacific plates is distributed across a wide zone of the western margin of the continent, where at least 25-30% of the plate boundary strain is accommodated via intraplate deformation. We hypothesize that during the early to mid-Miocene transtensional deformation was located east of the Sierra Nevada in the Mono Basin prior to stepping east into the Mina Deflection. Seventeen 40Ar/39Ar age determinations were obtained from sequences of lava flows that yield relatively stable plateau ages that indicate eruption in the late Miocene to early Pliocene. Paleomagnetic data were collected from the Miocene Jack Springs Tuff (JST) east of Huntoon Valley, and stratigraphically continuous sections of Mio-Pliocene basalt flows near Marietta, NV (MB), Pizona, CA (PB), Queens Valley, CA/NV (QVB), and in the Adobe Hills (AH). Nineteen sites from the JST yield clockwise discordant results, with respect to the reference location, from +20°±10° to +60°±11°. The results from the basalts yield discordant data with respect to the Miocene expected field direction (D=353°, I=58°, A95= 3°). Twelve of 13 sites from the MB yield a group mean direction D=027°, I=57°, a95=12.4° that is clockwise discordant with an inferred rotation (R) and flattening (F) of R=+33.9°+/-18.4° and F=1.3°+/-10.6°. Seventeen of 22 sites from four sections in the PB indicate that three sections are counter-clockwise discordant and one section plots on the expected field direction. Sixteen of 23 sites from five sections in the QVB indicate that three sections are counter-clockwise discordant and two sections are clockwise discordant. Thirty-four sites of the >100 sites collected in the Adobe Hills are clockwise discordant ranging from +15°±10° to +50°±10°. This study provides the first paleomagnetic data for this area, which supports the hypothesis of strain accommodated by vertical axis rotation in the Mono Basin and constrains the timing of intraplate
Directory of Open Access Journals (Sweden)
Suhendra Suhendra
2012-05-01
Full Text Available White pepper is produced by decorticating the pericarp of the pepper which commonly be done manually or mechani cally. A pepper decorticator without soaking process was developed in order to improve quality and capasity of decor tication. The decortication mechanism was designed by shearing the pepper on a gap between a static vertical cylinder and a vertical axis rotating tube. This research was done to analyze the decortication and working performances of the machine. Dimension analysis approach was applied in order to develope a mathematical relation to be used for prediction of the machine performance based on their design and operational variables. The machine variables varied were linear speed of tube (v, width of clearance (s, and length of rotated cylinder (L. The material variables were diameter of pepper (D , decortication force (F , and density of pepper (ρ . From the analysis result, there were debkbfined mathematical equations for prediction of decorticated pepper (p , damaged pepper (p and working capacity ofkrthe machine (K . Validation analysis shows that the equations could be used for prediction and determination of themachine performances needed. ABSTRAK Lada putih dihasilkan melalui proses pengupasan kulit lada yang dilakukan secara manual atau mekanis. Untuk meng atasi masalah rendahnya kapasitas dan kualitas pengupasan telah dikembangkan rancangbangun mesin pengupas kulit lada dengan sistem gesekan pada silinder dengan putaran poros secara vertikal tanpa melalui proses perendaman. Penelitian ini dilakukan untuk menganalisis kinerja pengupasan, kerusakan dan kapasitas kerja mesin. Pendekatan analisis dimensi diterapkan untuk mendapatkan persamaan matematis yang dapat digunakan untuk memprediksi dan merencanakan kinerja mesin berdasarkan variabel rancangbangun dan operasionalnya. Variabel bebas mesin yang di variasikan meliputi kecepatan linier silinder (v, lebar celah (s dan panjang silinder pengupas (L. Variabel
Zhou, Cai; Wang, Fenglong; Dunzhu, Gesang; Yao, Jinli; Jiang, Changjun
2016-11-01
Non-volatile electric field-based control of magnetic anisotropy in Co2FeAl/ Pb(Mg1/3Nb2/3)O3-PbTiO3 (CFA/PMN-PT) heterostructures is investigated at room temperature. The remnant magnetization response under different electric fields shows a asymmetric butterfly-like behavior; specifically, this behavior is consistent with the asymmetric butterfly-like piezostrain versus applied electric field curve. Thus electric field-induced non-volatile 90° magnetic easy axis rotation can be attributed to the piezostrain effect. Further, the result measured by rotating-angle ferromagnetic resonance demonstrates piezostrain-mediated non-volatile 90° magnetic easy axis rotation at the initial state and the two remnant polarization states after application of the poling fields of 10 and -10 kV cm-1 turned off. The angular dependence of magnetic damping also indicates a 90° phase shift at the above mentioned three different states. Additionally, the piezostrain-mediated non-volatile stable magnetization reversal in the two directions of easy and hard magnetization axes are observed under positive and negative pulsed electric fields, which can be used to improve the performance of low-loss multiple-state memory devices.
Baland, Rose-Marie; Yseboodt, Marie; Rivoldini, Attilio; Van Hoolst, Tim
2017-06-01
Mercury’s spin axis nearly occupies the Cassini state 1, in which the orbit normal and spin axis precess together with a long period of about 300 000 years. Mercury slightly deviates from that state which is defined for a uniformly precessing rigid planet. Variations in obliquity and deviation from the coplanarity between the spin axis, the normal to the orbit and the normal to the Laplace plane are induced by the slow precession of the pericenter. Moreover, the short-periodic tidal deformations induce a constant shift over time in mean obliquity and deviation, characterized by the tidal love number k2 and by the ratio k2/Q of the tidal Love number over the tidal quality factor, respectively. Including theses effects, we analytically develop a new Cassini state model and reinterpret recent determination of Mercury's orientation in terms of parameters of Mercury's interior. We also show explicitly that Peale's equation is sometimes wrongly cited in the literature, resulting in wrong estimates of the polar moment of inertia.From the orientation of Stark et al. (2015, Planetary and Space Science, Vol. 117), we find C/MR2=0.3433+/-0.0134, which is 0.9% smaller than the estimate by Stark et al. (2015) themselves, because of our refinements of the Cassini state model (0.1%) and their wrong use of Peale's equation (0.8%). That difference is below the actual precision (3-4%) on the polar moment of inertia but may be of the order of precision that can be reached with BepiColombo mission (<0.3%). Given the actual precision on the spin axis orientation, we place an upper limit of about 0.02 on the ratio k2/Q and of about 350 on Q (assuming k2=0.5) at the 1 sigma level. The parameter k2 cannot be estimated from the spin axis orientation, because of its correlation with the polar moment of inertia. In the future, the relative precision on the determination of k2/Q from the spin axis orientation could be as good as 30% with BepiColombo, so that the non-elastic parameter of
DESIGN OF MULTI-MIRROR REFLECTIVE CONCENTRATOR FOR SINGLE-AXIS ROTATING TRACKER%单轴旋转跟日式多平面镜反射聚光器的设计
Institute of Scientific and Technical Information of China (English)
张海燕; 王建平; 张崇巍
2011-01-01
主要设计了一种新型的单轴旋转跟日式多镜面聚光系统,该系统与目前常见的聚光器相比,价格低廉、易于维护,仅通过单轴的转动来实现反射聚光,耗能较小.对系统中各镜面的位置及尺寸进行了详细的讨论和计算,并通过实验验证了其可行性和有效性,该方法能实现4倍以上的聚光,能有效减少跟踪系统消耗的能量,从而提高整个跟踪聚光系统的性价比.%A novel type of the multi-mirror concentrator system for single-axis rotating tracker was presented. Comparing with the current solar concentrating, the new concentrator performs reflective concentration through single-axis rotation, which possesses the characteristics of cheap cost, easy maintenance and low energy-consumption. The correlative quantitative analysis and numerical calculation were done for this system, and their feasibility and effectiveness were verified by experiment. By establishing the tracking motion relationship between solar module and multi-mirror, the tracking control relationship between solar module and multi-mirror was achieved.
Aeroelastically coupled blades for vertical axis wind turbines
Paquette, Joshua; Barone, Matthew F.
2016-02-23
Various technologies described herein pertain to a vertical axis wind turbine blade configured to rotate about a rotation axis. The vertical axis wind turbine blade includes at least an attachment segment, a rear swept segment, and optionally, a forward swept segment. The attachment segment is contiguous with the forward swept segment, and the forward swept segment is contiguous with the rear swept segment. The attachment segment includes a first portion of a centroid axis, the forward swept segment includes a second portion of the centroid axis, and the rear swept segment includes a third portion of the centroid axis. The second portion of the centroid axis is angularly displaced ahead of the first portion of the centroid axis and the third portion of the centroid axis is angularly displaced behind the first portion of the centroid axis in the direction of rotation about the rotation axis.
Herman, Scott William
The history of late Miocene (Proto-Gulf) deformation on the Sonoran margin of the Gulf of California is key to understanding how Baja California was captured by the Pacific plate and how strain was partitioned during the Proto-Gulf period (12.5-6 Ma). The Sierra el Aguaje and Sierra Tinajas del Carmen are located in southwestern coastal Sonora, Mexico, and represent the eastern rifted margin of the central Gulf of California. The ranges are composed of volcanic units and their corresponding volcaniclastic units which are the result of persistent magmatic activity between 20 and 8.8 Ma, including three packages of basalt and andesite that make excellent paleomagnetic recorders. Based on cross cutting relations and geochronologic data for pre-, syn-, and post-tectonic volcanic units, most of the faulting and tilting in the Sierra El Aguaje is bracketed between 11.9 and 9.0 Ma, thus falling entirely within Proto-Gulf time. A paleomagnetic investigation into possible vertical axis rotations in the Sierra el Aguaje has uncovered evidence of clockwise rotations between ~13º and ~105º with possible translations. These results are consistent with existing field relations, which suggest the presence of large (>45°) vertical axis rotations in this region. This evidence includes: a) abrupt changes in the strike of tilted strata in different parts of the range, including large domains characterized by E-W strikes b) ubiquitous NE-SW striking faults with left lateral-normal oblique slip, that terminate against major NW-trending right lateral faults, and c) obliquity between the general strike of tilted strata and the strike of faults. These rotations occurred after 12 Ma and largely prior to 9 Ma, thus falling into the Proto-Gulf period. Such large-scale rotations lend credence to the theory that the area inboard of Baja California was experiencing transtension during the Proto-Gulf period, rather than the pure extension that would be the result of strain partitioning
Samarasinha, Nalin
2013-01-01
We introduce a parameter, X, to predict the changes in the rotational period of a comet in terms of the rotational period itself, the nuclear radius, and the orbital characteristics. We show that X should be a constant if the bulk densities and shapes of nuclei are nearly identical and the activity patterns are similar for all comets. For four nuclei for which rotational changes are well documented, despite the nearly factor 30 variation observed among the effective active fractions of these comets, X is constant to within a factor two. We present an analysis for the sungrazing comet C/2012 S1 (ISON) to explore what rotational changes it could undergo during the upcoming perihelion passage where its perihelion distance will be ~2.7 solar radii. When close to the sun, barring a catastrophic disruption of the nucleus, the activity of ISON will be sufficiently strong to put the nucleus into a non-principal-axis rotational state and observable changes to the rotational period should also occur. Additional causes ...
Energy Technology Data Exchange (ETDEWEB)
Vaughn, Mark R. (Albuquerque, NM); Robinett, III, Rush D. (Tijeras, NM); Phelan, John R. (Albuquerque, NM); Van Zuiden, Don M. (Albuquerque, NM)
1997-01-21
A new class of coplanar two-axis angular effectors. These effectors combine a two-axis rotational joint analogous to a Cardan joint with linear actuators in a manner to produce a wider range of rotational motion about both axes defined by the joint. This new class of effectors also allows design of robotic manipulators having very high strength and efficiency. These effectors are particularly suited for remote operation in unknown surroundings, because of their extraordinary versatility. An immediate application is to the problems which arise in nuclear waste remediation.
Energy Technology Data Exchange (ETDEWEB)
Vaughn, M.R.; Robinett, R.D. III; Phelan, J.R.; Zuiden, D.M. Van
1997-01-21
A new class of coplanar two-axis angular effectors is described. These effectors combine a two-axis rotational joint analogous to a Cardan joint with linear actuators in a manner to produce a wider range of rotational motion about both axes defined by the joint. This new class of effectors also allows design of robotic manipulators having very high strength and efficiency. These effectors are particularly suited for remote operation in unknown surroundings, because of their extraordinary versatility. An immediate application is to the problems which arise in nuclear waste remediation. 11 figs.
Institute of Scientific and Technical Information of China (English)
高贤志; 王丹
2012-01-01
It is significantly important to improve the performance of inertial navigation system navigation by controlling the negative effects on inertial navigation system for inertial measurement units. This paper analyses the error equations of the inertial navigation system, makes a focus on the inertial components accumulation effect on symmetrical position error, analyses the automatic constant error compensation mechanism of the inertial navigation system, and then discusses the error depressing of inertial components constant error, the scale factor error cased by rotating. Finally, the simulation for single-axis rotation mechanism validates the theory analysis.%提高惯导系统对于惯性器件误差负面影响的抑制能力,对于改善系统的导航精度具有重要意义.本文对惯导系统误差方程进行分析,重点讨论对称位置上惯性器件误差的积累效果,系统地研究了单轴旋转调制对捷联惯性导航系统惯性器件误差的自动补偿机理,详细分析了单轴旋转对惯性器件常值误差、标度因数误差的抑制情况.对单轴旋转调制方案进行仿真,验证了理论分析的正确性.
Numerical Study on Fixed-Axis Rotation of Rigid Body under Variable Moment Inertia%变转动惯量刚体定轴转动的数值研究
Institute of Scientific and Technical Information of China (English)
唐军杰; 王爱军; 赵昆; 张鹏
2012-01-01
Given a model of variable moment inertia of rigid body,a numerical method with Matlab has been applied to study the fixed-axis rotation of rigid body under variable moment inertia and constant external torque. Because at the initial stage the changes in variable moment inertia are very small , the movement of rigid body is similar to that when moment inertia is constant. As the changes in moment inertia become greater,the angular velocity of rigid body changes periodically under the impact of elastic restoring forces.%给出一个变转动惯量刚体模型,用数值方法研究了在恒力矩作用下变转动惯量刚体的定轴转动问题.在开始阶段由于转动惯量变化很小,刚体运动与刚体转动惯量不变的情况相似,随着转动惯量变化增大,在弹性恢复力的作用下,刚体角速度呈周期性变化.
Ray-tracing for qP waves in media with rotated axis of symmetry%旋转轴对称介质中的qP波射线追踪
Institute of Scientific and Technical Information of China (English)
杨文军; 孙福利
2011-01-01
本文使用qP波一阶射线追踪方程(FORT)计算光滑、非均匀旋转轴对称弱各向异性介质中qP波传播的路径和走时.此FORT方程只依赖于15个弱各向异性参数,而非标准射线方程中的21个弹性参数.通常弹性参数模型是在局部坐标系中给定的,而在实际中需要的是全局坐标系下的弹性参数,因此为了解决两个坐标系下弹,性参数的变换问题,本文从Bond变换方程出发,推导出了旋转轴对称介质中的弹性参数张量变换方程.全局坐标系中的弹性参数是由局部坐标系中弹性参数通过两个坐标系间极角和方位角的正、余弦函数组合给出的,所得到的弹性参数能够完全匹配FORT方程.最后通过对旋转TI模型和正交模型进行数值模拟验证本方法的有效性和适应性,结果表明本方法对于具有不同各向异性类型、各向异性强度和旋转角度的介质都具有很高的计算精度.%We use the first-order ray tracing (FORT) formulas of qP waves to calculate pathes and traveltimes of qP waves propagation in smooth, inhomogeneous and weakly anisotropic medium with arbitrarily symmetric axes. The FORT equations depend only on 15 weak-anisotropy parameters, not on the 21 elastic moduli used in the standard raytracing equations. The elastic modulus of anisotropic media is presented in the local coordinate system, while practical coordinate is in the global system, the Cartesian coordinate system. In order to solve the inconsistency problem between the global coordinate system and the local coordinate system, in this paper, the tensor transformation equations of elastic modulus in media with rotated axis of symmetry are derived from the Bond transformation equations. The weak-anisotropy parameters in the global coordinate system can be explicitly expressed as the combination with the sine and cosine functions of polar angle and azimuth between these different coordinate systems,and the weak
单轴旋转惯导转轴方向高精度标定方法研究%Shaft orientation calibration method for single-axis rotation INS
Institute of Scientific and Technical Information of China (English)
李有; 王省书; 黄宗升; 战德军
2014-01-01
在单轴旋转激光陀螺惯导系统中，转轴方向误差将导致船体姿态解算结果中出现阶跃跳变。本文在分析转轴方向误差与姿态解算误差之间的数学关系的基础上，提出了一种转轴方向的在线标定方法。利用转轴角编码器和惯性测量单元（IMU）的输出数据，解调出船体姿态信息，再根据解调所得到的转轴旋转前后船体姿态的误差，反解出转轴实际方向。通过对实际系统数据实验，验证了该方法的有效性。%In single-axis rotation inertial navigation system, shaft orientation error will lead to the step effect in the ship attitude result. We derived the mathematical relationship between the shaft orientation error and the ship attitude measurement error, and proposed an online shaft orientation calibration method based on the mathematical relationship. The output data of the shaft an-gle-encoder and the inertial measurement unit (IMU) was adopted to calculate the ship attitude, and then the real shaft orientation was calculated inversely according to the measured ship attitude error. Experimental results showed that this method can calibrate the shaft orientation in a high accuracy.
Vertical axis wind turbine airfoil
Krivcov, Vladimir; Krivospitski, Vladimir; Maksimov, Vasili; Halstead, Richard; Grahov, Jurij Vasiljevich
2012-12-18
A vertical axis wind turbine airfoil is described. The wind turbine airfoil can include a leading edge, a trailing edge, an upper curved surface, a lower curved surface, and a centerline running between the upper surface and the lower surface and from the leading edge to the trailing edge. The airfoil can be configured so that the distance between the centerline and the upper surface is the same as the distance between the centerline and the lower surface at all points along the length of the airfoil. A plurality of such airfoils can be included in a vertical axis wind turbine. These airfoils can be vertically disposed and can rotate about a vertical axis.
Centrifugally activated bearing for high-speed rotating machinery
Post, Richard F.
1994-01-01
A centrifugally activated bearing is disclosed. The bearing includes an annular member that extends laterally and radially from a central axis. A rotating member that rotates about the central axis relative to the annular member is also included. The rotating member has an interior chamber that surrounds the central axis and in which the annular member is suspended. Furthermore, the interior chamber has a concave shape for retaining a lubricant therein while the rotating member is at rest and for retaining a lubricant therein while the rotating member is rotating. The concave shape is such that while the rotating member is rotating a centrifugal force causes a lubricant to be forced away from the central axis to form a cylindrical surface having an axis collinear with the central axis. This centrifugally displaced lubricant provides restoring forces to counteract lateral displacement during operation.
Electrical-Discharge Machining With Additional Axis
Malinzak, Roger M.; Booth, Gary N.
1991-01-01
Proposed electrical-discharge-machining (EDM) apparatus uses moveable vertical wire as electrode. Wire positionable horizontally along one axis as it slides vertically past workpiece. Workpiece indexed in rotation about horizontal axis. Because of symmetry of parts, process used to make two such parts at a time by defining boundary between them. Advantages: cost of material reduced, imparts less residual stress to workpiece, and less time spent machining each part when parts produced in such symmetrical pairs.
The Rotation State of Comet 103P/Hartley 2
Farnham, Tony; Knight, Matthew M.; Schleicher, David G.
2016-10-01
On November 4, 2010, the Deep Impact (DI) spacecraft made its closest approach to comet 103P/Hartley 2, passing only 694 km from the nucleus. Observations of the coma produced a lightcurve that shows the nucleus is in a state of non-principal axis rotation that evolves with time, while other observations revealed a nucleus that has concentrated collimated jets driven by CO2 emission (A'Hearn et al., 2011), large variability in the production of H2O and CO2 (Besse et al. 2016), and ice patches on the surface (Sunshine et al. 2011). To properly interpret the significance of these phenomena, it is necessary to understand the rotation of the nucleus, so that its thermal history can be derived and properly modeled, while at the same time, it is likely that the comet's high activity levels play an important role in the nucleus dynamics.An analysis of the lightcurve by Belton et al (2013) described the comet's rotation state, with two periodicities (primary of 18 h, secondary of 28 or 55 h) that change with time. Although their solution describes the periodicities observed around closest approach, it is insufficient to reproduce the changes in coma morphology with time. We are performing an analysis of the structures in the coma (Farnham 2009), using Monte Carlo routines to model the outflowing dust produced by active sources on the nucleus, to derive a comprehensive solution for the nucleus' rotation.We are also obtaining new observations of Hartley 2 in June/July 2016 (r~3.2 AU) to measure the nucleus' primary component period before the comet becomes highly active. This will provide an end-state measure of the rotation from the 2010 apparition, as well as a starting value for the current apparition, to allow its continuing evolution to be monitored. We will present an update on the status and preliminary results of these analyses.This work is funded by NASA Grant NNX12AQ64G.A'Hearn, M.F., et al. (2011) Science 332, 1396-1400Belton M.J.S., et al. (2013) Icarus 222, 595
Dual Axis Light Sensor for Tracking Sun
Shibata, Miki; Tambo, Toyokazu
We have developed convenient light sensors to control a platform of solar cell panel. Dual axis light sensor in the present paper has structure of 5 PD (photodiode) light sensor which is composed of 5 photodiodes attached on a frustum of pyramid(1). Light source can be captured in front of the sensor by rotating the X and Y axis as decreasing the output deviation between two pairs of outside photodiodes. We here report the mechanism of sun tacking using the dual axis 5 PD light sensor and the fundamental results performed in the dark room.
Manolopoulou, Maria
2016-01-01
We study the possible rotation of cluster galaxies, developing, testing and applying a novel algorithm which identifies rotation, if such does exits, as well as its rotational centre, its axis orientation, rotational velocity amplitude and, finally, the clockwise or counterclockwise direction of rotation on the plane of the sky. To validate our algorithms we construct realistic Monte-Carlo mock rotating clusters and confirm that our method provides robust indications of rotation. We then apply our methodology on a sample of Abell clusters with z<~0.1 with member galaxies selected from the SDSS DR10 spectroscopic database. We find that ~35% of our clusters are rotating when using a set of strict criteria, while loosening the criteria we find this fraction increasing to ~48%. We correlate our rotation indicators with the cluster dynamical state, provided either by their Bautz-Morgan type or by their X-ray isophotal shape and find for those clusters showing rotation that the significance and strength of their...
Cross-axis adaptation of torsional components in the yaw-axis vestibulo-ocular reflex
Trillenberg, P.; Shelhamer, M.; Roberts, D. C.; Zee, D. S.
2003-01-01
The three pairs of semicircular canals within the labyrinth are not perfectly aligned with the pulling directions of the six extraocular muscles. Therefore, for a given head movement, the vestibulo-ocular reflex (VOR) depends upon central neural mechanisms that couple the canals to the muscles with the appropriate functional gains in order to generate a response that rotates the eye the correct amount and around the correct axis. A consequence of these neural connections is a cross-axis adaptive capability, which can be stimulated experimentally when head rotation is around one axis and visual motion about another. From this visual-vestibular conflict the brain infers that the slow-phase eye movement is rotating around the wrong axis. We explored the capability of human cross-axis adaptation, using a short-term training paradigm, to determine if torsional eye movements could be elicited by yaw (horizontal) head rotation (where torsion is normally inappropriate). We applied yaw sinusoidal head rotation (+/-10 degrees, 0.33 Hz) and measured eye movement responses in the dark, and before and after adaptation. The adaptation paradigm lasted 45-60 min, and consisted of the identical head motion, coupled with a moving visual scene that required one of several types of eye movements: (1) torsion alone (-Roll); (2) horizontal/torsional, head right/CW torsion (Yaw-Roll); (3) horizontal/torsional, head right/CCW torsion (Yaw+Roll); (4) horizontal, vertical, torsional combined (Yaw+Pitch-Roll); and (5) horizontal and vertical together (Yaw+Pitch). The largest and most significant changes in torsional amplitude occurred in the Yaw-Roll and Yaw+Roll conditions. We conclude that short-term, cross-axis adaptation of torsion is possible but constrained by the complexity of the adaptation task: smaller torsional components are produced if more than one cross-coupling component is required. In contrast, vertical cross-axis components can be easily trained to occur with yaw head
Modeling rigid magnetically rotated microswimmers: rotation axes, bistability, and controllability.
Meshkati, Farshad; Fu, Henry Chien
2014-12-01
Magnetically actuated microswimmers have recently attracted attention due to many possible biomedical applications. In this study we investigate the dynamics of rigid magnetically rotated microswimmers with permanent magnetic dipoles. Our approach uses a boundary element method to calculate a mobility matrix, accurate for arbitrary geometries, which is then used to identify the steady periodically rotating orbits in a co-rotating body-fixed frame. We evaluate the stability of each of these orbits. We map the magnetoviscous behavior as a function of dimensionless Mason number and as a function of the angle that the magnetic field makes with its rotation axis. We describe the wobbling motion of these swimmers by investigating how the rotation axis changes as a function of experimental parameters. We show that for a given magnetic field strength and rotation frequency, swimmers can have more than one stable periodic orbit with different rotation axes. Finally, we demonstrate that one can improve the controllability of these types of microswimmers by adjusting the relative angle between the magnetic field and its axis of rotation.
LAMB WAVES PROPAGATION ALONG NON-PRINCIPAL DIRECTIONS IN ORTHOTROPIC PLATE%正交各向异性板中非主轴方向的Lamb波
Institute of Scientific and Technical Information of China (English)
何存富; 刘宏业; 刘增华; 吴斌
2013-01-01
Based on linearly three-dimensional elasticity,the wave motion equations for coupled Lamb waves which propagate along non-principal directions of the material are derived by using a Legendre orthogonal polynomial approach,and the coupled equations of wave motion are solved numerically. For verifying its applicability and validity,the present approach is applied to isotropic material and obtained results are compared with existing results. Then,the phase dispersion curves of coupled Lamb waves along different non-principal directions are calculated,and the effects of the different propagation directions on fundamental modes and high-order modes are investigated. Finally,the distributions of phase and group velocities of fundamental modes are shown respectively,which are useful for structural health monitoring of aniso-tropic materials. Simultaneously,the reason that So mode is the most sensitive to the change of the propagation direction is illustrated with both displacement distribution of fundamental modes and material's ani-sotropy property being considered.%基于线性三维弹性理论,采用勒让德正交多项式展开法,推导了波沿正交各向异性材料非主轴方向传播时的Lamb波耦合波动方程,并对耦合波动方程进行了数值求解.为验证该方法的适用性和正确性,首先将此方法应用于各向同性材料,并与已知的数据结果进行了比较；然后以单向纤维增强复合材料为例,计算了耦合Lamb波沿不同的非主轴方向传播时的相速度频散曲线,并分别研究了传播方向改变时低阶模态Lamb波和高阶模态Lamb波频散特性的变化.最后,针对潜在用于各向异性复合材料结构健康监测的耦合Lamb波低阶模态,给出了其在不同传播方向时的相速度分布和群速度分布.同时,结合低阶模态Lamb波的位移分布特性和材料的各向异性特点,阐释了S0模态对波的传播方向变化最为敏感的原因.
Vertical-axis wind turbines -- The current status of an old technology
Energy Technology Data Exchange (ETDEWEB)
Berg, D.E.
1996-12-31
Vertical-axis wind turbine technology is not well understood, even though the earliest wind machines rotated about a vertical axis. The operating environment of a vertical-axis wind turbine is quite complex, but detailed analysis capabilities have been developed and verified over the last 30 years. Although vertical-axis technology has not been widely commercialized, it exhibits both advantages and disadvantages compared to horizontal-axis technology, and in some applications, it appears to offer significant advantages.
Rotating Shaft Tilt Angle Measurement Using an Inclinometer
2015-01-01
This paper describes a novel measurement method to accurately measure the rotating shaft tilt angle of rotating machine for alignment or compensation using a dual-axis inclinometer. A model of the rotating shaft tilt angle measurement is established using a dual-axis inclinometer based on the designed mechanical structure, and the calculation equation between the rotating shaft tilt angle and the inclinometer axes outputs is derived under the condition that the inclinometer axes are perpendic...
Rotationally symmetric viscous gas flows
Weigant, W.; Plotnikov, P. I.
2017-03-01
The Dirichlet boundary value problem for the Navier-Stokes equations of a barotropic viscous compressible fluid is considered. The flow region and the data of the problem are assumed to be invariant under rotations about a fixed axis. The existence of rotationally symmetric weak solutions for all adiabatic exponents from the interval (γ*,∞) with a critical exponent γ* < 4/3 is proved.
Dimensionality constraints of light induced rotation
Oroszi, László; Galajda, Péter; Kelemen, Lóránd; Mathesz, Anna; Vicsek, Tamás; Vizsnyiczai, Gaszton; Ormos, Pál
2015-01-01
We have studied the conditions of rotation induced by collimated light carrying no angular momentum. Objects of different shapes and optical properties were examined in the nontrivial case where the rotation axis is perpendicular to the direction of light propagation. This geometry offers important advantages for application as it fundamentally broadens the possible practical arrangements to be realised. We found that collimated light cannot drive permanent rotation of 2D or prism-like 3D objects (i.e. fixed cross-sectional profile along the rotation axis) in the case of fully reflective or fully transparent materials. Based on both geometrical optics simulations and theoretical analysis, we derived a general condition for rotation induced by collimated light carrying no angular momentum valid for any arrangement: Permanent rotation is not possible if the scattering interaction is two-dimensional and lossless. In contrast, light induced rotation can be sustained if partial absorption is present or the object ...
Energy Technology Data Exchange (ETDEWEB)
NONE
2001-03-01
As element technology to continuously control attitude and feed of tools, development was made of precision machining technology, 6-axis CAM/CAE system and high speed high precision NC control technology. A high precision non-rotating tool machine was trial-manufactured which enables the heightening of precision in machining of mold curved surfaces/complicated shaped parts, and the practicality was verified. In FY 2000, as to the machining technology relation, it was verified that it is possible to machine the mirror surface at 0.1{mu}mRy using diamond non-rotating tool to aluminum materials. In CAD/CAM relations, a high speed high precision CAM/NC interface system based on ISO14649 was developed. Then, by the tool path made by this system, cutting experiment/evaluation were conducted. Further, a new system for cutting reversely tapered grooves was designed, and the cutting experiment was carried out. In the NC relation, development was made of the NC system loaded with the work coordinate interpolation function for conducting high precision multi-axial interpolation on high speed NC board and also of the high speed servo network using IEEE1394. (NEDO)
ELONGATED ODONTOID PROCESS OF AXIS VERTEBRA
Directory of Open Access Journals (Sweden)
Prathap Kumar J,
2014-09-01
Full Text Available Introduction: Odontoid process is a bony projection of axis around which the atlas rotates. It measures 1 to 1.25 cms in length and projects upwards from the body of Axis. An elongated odontoid process may narrow the foramen magnum causing compressive neurological symptoms. It can cause cervical stiffness, serious restrictions of neck movement, and even a bone-derived torticollis. Observation: During routine osteology classes, we encountered an Axis vertebra with an elongated odontoid process. The measurements of the elongated odontoid process were taken using digital Vernier slide calipers. Conclusion: Elongated odontoid process can be mistaken for fracture of dens in radiological images; hence the knowledge of elongated odontoid process is useful for the radiologists, neurosurgeons and orthopaedicians for accurate diagnosis and treatment involving cranio-vertebral junctions.
Determining the Stellar Spin Axis Orientation
Lesage, Anna-Lea; Wiedemann, Gunter
2015-01-01
We present an observing method that permits the determination of the absolute stellar spin axis position angle based on spectro-astrometric observations for slowly-rotating late-type stars. This method is complementary to current interferometric observations that determine the orientation of stellar spin axis for early-type fast-rotating stars. Spectro-astrometry enables us to study phenomena below the diffraction limit, at the milli-arcsecond scale. It relies on the wavelength dependent variations of the centroid position of a structured source in a long-slit spectrum. A rotating star has a slight tilt in its spectral lines, which induces a displacement of the photocentre's position. By monitoring the amplitude of the displacement for varying slit orientations, we can infer the absolute position angle of the stellar spin axis. Finally, we present first observational results on Aldebaran obtained with the Thüringer Landesternwarte high resolution spectrograph. We were able to retrieve Aldebaran's position angle with less than 10° errors.
Disambiguation of Mental Rotation by Spatial Frames of Reference
Directory of Open Access Journals (Sweden)
Nobuhiko Asakura
2011-06-01
Full Text Available Previous research has shown that our ability to imagine object rotations is limited and associated with spatial reference frames; performance is poor unless the axis of rotation is aligned with the object-intrinsic frame or with the environmental frame. Here, we report an active effect of these reference frames on the process of mental rotation: they can disambiguate object rotations when the axis of rotation is ambiguous. Using novel mental rotation stimuli, in which the rotational axes between pairs of objects can be defined with respect to multiple frames of reference, we demonstrate that the vertical axis is preferentially used for imagined object rotations over the object-intrinsic axis for an efficient minimum rotation. In contrast, the object-intrinsic axis can play a decisive role when the vertical axis is absent as a way of resolving the ambiguity of rotational motion. When interpreted in conjunction with recent advances in the Bayesian framework for motion perception, our results suggest that these spatial frames of reference are incorporated into an internal model of object rotations, thereby shaping our ability to imagine the transformation of an object's spatial structure.
Tucker, Dennis Stephen (Inventor); Capo-Lugo, Pedro A. (Inventor)
2016-01-01
A single-axis accelerometer includes a housing defining a sleeve. An object/mass is disposed in the sleeve for sliding movement therein in a direction aligned with the sleeve's longitudinal axis. A first piezoelectric strip, attached to a first side of the object and to the housing, is longitudinally aligned with the sleeve's longitudinal axis. The first piezoelectric strip includes a first strip of a piezoelectric material with carbon nanotubes substantially aligned along a length thereof. A second piezoelectric strip, attached to a second side of the object and to the housing, is longitudinally aligned with the sleeve's longitudinal axis. The second piezoelectric strip includes a second strip of the piezoelectric material with carbon nanotubes substantially aligned along a length thereof. A voltage sensor is electrically coupled to at least one of the first and second piezoelectric strips.
Partially locally rotationally symmetric perfect fluid cosmologies
Mustapha, N; Van Elst, H; Marklund, M; Mustapha, Nazeem; Ellis, George F R; Elst, Henk van; Marklund, Mattias
2000-01-01
We show that there are no new consistent perfect fluid cosmologies with the kinematic variables and the electric and magnetic parts of the Weyl curvature all rotationally symmetric about a common axis in an open neighbourhood ${\\cal U}$ of an event. The consistent solutions of this kind are either locally rotationally symmetric, or are subcases of the Szekeres model.
Rotational image deblurring with sparse matrices
DEFF Research Database (Denmark)
Hansen, Per Christian; Nagy, James G.; Tigkos, Konstantinos
2014-01-01
We describe iterative deblurring algorithms that can handle blur caused by a rotation along an arbitrary axis (including the common case of pure rotation). Our algorithms use a sparse-matrix representation of the blurring operation, which allows us to easily handle several different boundary cond...
Institute of Scientific and Technical Information of China (English)
于旭东; 魏学通; 李莹; 龙兴武
2012-01-01
在激光陀螺单轴旋转惯性导航系统中,单轴旋转可以自动补偿垂直于旋转轴上的惯性器件误差,却不能消除旋转轴方向上惯性器件的误差,因此单轴旋转惯性导航系统的导航精度主要由轴向陀螺漂移决定.提出了一种基于径向基函数神经网络的轴向陀螺漂移辨识方法,利用系统纬度误差和温度变化量作为训练集,针对系统热态、冷态两种情况对RBF神经网络进行训练,对轴向陀螺漂移的辨识精度达到0.0003°/h.试验结果表明:该方法能够有效地辨识轴向陀螺漂移,使系统达到较高的导航精度,满足实际应用的需要.%In the single-axis rotation inertial navigation system with ring laser gyroscope ( RLG), the single-axis rotation can compensate the vertical errors of the inertial apparatus automatically, but cannot compensate the axial vertical errors, so the precision of the system is determined by the drift of the axial RLG. A novel identification method based on radial basis function network is proposed for the axial RLG drift. The inputs of the network are the latitude error and change of the temperature, and the network is trained for steady and non-steady state, in which the identification capability is less than 0. 0003°/h. The experiments show that this method can estimate the axial RLG drift efficaciously, and the result of the navigation is excellent and can meet the practical demand.
Three-axis force actuator for a magnetic bearing
Gondhalekar, Vijay (Inventor)
1998-01-01
This invention features a three-axis force actuator that axially, radially and rotatably supports a bearing member for frictionless rotation about an axis of rotation generally coincident with a Z-axis. Also featured is a magnetic bearing having such an actuator. The actuator includes an inner member, a magnetic member and a pole assembly having a ring member and four pole extending therefrom. The poles are equi-angular spaced from each other and radially spaced about the Z-axis. The inner member extends along the Z-axis and is a highly magnetic permeable material. The magnetic member is formed about the inner member outer surface, extends along the Z-axis and is configured so one magnetic pole polarity is located at its outer surface and the other polarity pole is located at its inner surface. Preferably, the magnetic member is a radially magnetized permanent magnet. The inner surface of the ring member is magnetically coupled to the magnetic member and a face of each pole is coupled to the bearing member. The magnetic member, the pole assembly, the inner member and the bearing member cooperate to generate a magnetic field that radially and rotatably supports a rotating member secured to the bearing member. The actuator further includes a plurality of electromagnetic coils. Preferably, a coil is formed about each pole and at least 2 coils are formed about the inner member. When energized, the electromagnetic coils generate a modulated magnetic field that stabilizes the rotating member in the desired operational position.
Application of Circulation Controlled Blades for Vertical Axis Wind Turbines
Shires, A.; Kourkoulis, V
2013-01-01
The blades of a vertical axis wind turbine (VAWT) rotor see an inconsistent angle of attack through its rotation. Consequently, VAWT blades generally use symmetrical aerofoils with a lower lift-to-drag ratio than cambered aerofoils tailored to maximise horizontal axis wind turbine rotor performance. This paper considers the feasibility of circulation controlled (CC) VAWT blades, using a tangential air jet to provide lift and therefore power augmentation. However CC blade sections require a hi...
Earth rotation prevents exact solid body rotation of fluids in the laboratory
Boisson, J; Moisy, F; Cortet, P -P
2012-01-01
We report direct evidence of a secondary flow excited by the Earth rotation in a water-filled spherical container spinning at constant rotation rate. This so-called {\\it tilt-over flow} essentially consists in a rotation around an axis which is slightly tilted with respect to the rotation axis of the sphere. In the astrophysical context, it corresponds to the flow in the liquid cores of planets forced by precession of the planet rotation axis, and it has been proposed to contribute to the generation of planetary magnetic fields. We detect this weak secondary flow using a particle image velocimetry system mounted in the rotating frame. This secondary flow consists in a weak rotation, thousand times smaller than the sphere rotation, around a horizontal axis which is stationary in the laboratory frame. Its amplitude and orientation are in quantitative agreement with the theory of the tilt-over flow excited by precession. These results show that setting a fluid in a perfect solid body rotation in a laboratory exp...
Development of methodology for horizontal axis wind turbine dynamic analysis
Dugundji, J.
1982-01-01
Horizontal axis wind turbine dynamics were studied. The following findings are summarized: (1) review of the MOSTAS computer programs for dynamic analysis of horizontal axis wind turbines; (2) review of various analysis methods for rotating systems with periodic coefficients; (3) review of structural dynamics analysis tools for large wind turbine; (4) experiments for yaw characteristics of a rotating rotor; (5) development of a finite element model for rotors; (6) development of simple models for aeroelastics; and (7) development of simple models for stability and response of wind turbines on flexible towers.
Childs, Peter R N
2010-01-01
Rotating flow is critically important across a wide range of scientific, engineering and product applications, providing design and modeling capability for diverse products such as jet engines, pumps and vacuum cleaners, as well as geophysical flows. Developed over the course of 20 years' research into rotating fluids and associated heat transfer at the University of Sussex Thermo-Fluid Mechanics Research Centre (TFMRC), Rotating Flow is an indispensable reference and resource for all those working within the gas turbine and rotating machinery industries. Traditional fluid and flow dynamics
Mechanical effects in a vortex device with a rotating core
Samokhvalov, V. N.
2017-05-01
The process of the appearance of forced rotation of an axial core mounted in a modified vortex tube in the direction opposite to the rotation of the air vortex and the precession of its axis have been studied. It has been established that dynamical bending of a metal axial core arises in the process of rotation which causes mechanical wear of its end part and fracture in the fastening area of the bearing without residual curvature of the core axis. The excitation of rotation and observed force effects are not related to the mechanical action of rotating air flow on the axial core.
On the problems of describing joint axis alignment.
Ball, Kevin A; Greiner, Thomas M
2008-01-01
Each three-dimensional joint possesses at least one potentially oblique axis of rotation. Several systems are used to express joint axis alignment. One system, designated the plane projection (PP) method, describes angles based on orthogonal projections onto two, of the three, anatomical planes. Alternatively, a joint axis may be described in two different ways using two sequential Cardan angle rotations. These expression systems all lay claim to similar descriptive labels, such as deviation and elevation. Difficulties arise as researchers use these various methods to compare their own data to the results of others. A joint axis alignment, described as 27 degrees deviation and 41 degrees elevation in PP, differs by as much as 6 degrees when expressed as Cardan angles. Differences among expression systems increase as the joint axis alignment becomes more oblique -- eventually differing by as much as 75 degrees . This paper explores implications for this lack of congruence among the joint axis expression systems. Effective steps in dealing with these issues begin with recognizing the existence and extent of the problem. The paper provides a common set of algorithms to illustrate and alleviate the possible problems associated with the exchange of joint axis alignment data.
Changes in the earth's rotation by tectonics : gravito-elastodynamics
Vermeersen, L.L.A.
1993-01-01
The rotation of the Earth is not regular. It changes on virtually every timescale we know in both position of the rotation axis and rotation rate. Even in our daily lives we sometimes experience the consequences of such changes, such as the second that is subtracted or added to clocks at the
Lekner, John
2008-01-01
Any free-particle wavepacket solution of Schrodinger's equation can be converted by differentiations to wavepackets rotating about the original direction of motion. The angular momentum component along the motion associated with this rotation is an integral multiple of [h-bar]. It is an "intrinsic" angular momentum: independent of origin and…
Vassiliev, Dmitri
2017-04-01
We consider an infinite three-dimensional elastic continuum whose material points experience no displacements, only rotations. This framework is a special case of the Cosserat theory of elasticity. Rotations of material points are described mathematically by attaching to each geometric point an orthonormal basis that gives a field of orthonormal bases called the coframe. As the dynamical variables (unknowns) of our theory, we choose the coframe and a density. We write down the general dynamic variational functional for our rotational theory of elasticity, assuming our material to be physically linear but the kinematic model geometrically nonlinear. Allowing geometric nonlinearity is natural when dealing with rotations because rotations in dimension three are inherently nonlinear (rotations about different axes do not commute) and because there is no reason to exclude from our study large rotations such as full turns. The main result of the talk is an explicit construction of a class of time-dependent solutions that we call plane wave solutions; these are travelling waves of rotations. The existence of such explicit closed-form solutions is a non-trivial fact given that our system of Euler-Lagrange equations is highly nonlinear. We also consider a special case of our rotational theory of elasticity which in the stationary setting (harmonic time dependence and arbitrary dependence on spatial coordinates) turns out to be equivalent to a pair of massless Dirac equations. The talk is based on the paper [1]. [1] C.G.Boehmer, R.J.Downes and D.Vassiliev, Rotational elasticity, Quarterly Journal of Mechanics and Applied Mathematics, 2011, vol. 64, p. 415-439. The paper is a heavily revised version of preprint https://arxiv.org/abs/1008.3833
Two-axis joint assembly and method
Le, Thang D. (Inventor); Lewis, James L. (Inventor); Carroll, Monty B. (Inventor)
2010-01-01
In an embodiment, a two-axis joint that utilizes planar reactions to handle moments applied to the side of the joint thereby allowing the device to remain low profile and compact with minimal intrusion to the mounting surface of the two-axis joint. To handle larger moments, the diameter of the planar member can be increased without increasing the overall height of the joint assembly thereby retaining the low profile thereof. Upper and lower antifriction bearings may be positioned within a housing engage the planar member to reduce rotational friction. The upper and lower bearings and a hub which supports the planar member transfer forces produced by moments applied to the side of the joint so as to spread the forces over the area of the housing.
DEFF Research Database (Denmark)
Takai, Hirokazu; Konstantinidis, Lukas; Schmal, Hagen;
2016-01-01
was uneventful. Conclusions. Oblique type axis body fractures resemble a highly unstable subtype of Anderson type III fractures with the potential of severe secondary deformity following conservative treatment, irrespective of initial grade of displacement. The authors therefore warrant a high index of suspicion......Purpose. Anderson type III odontoid fractures have traditionally been considered stable and treated conservatively. However, unstable cases with unfavorable results following conservative treatment have been reported. Methods. We present the cases of two patients who sustained minimally displaced...
Directory of Open Access Journals (Sweden)
Eveline S. Graf
2012-01-01
Full Text Available The two main movements occurring between the forefoot and rearfoot segment of a human foot are flexion at the metatarsophalangeal joints and torsion in the midfoot. The location of the torsion axis within the foot is currently unknown. The purpose of this study was to develop a method based on Cardan angles and the finite helical axis approach to calculate the torsion axis without the effect of flexion. As the finite helical axis method is susceptible to error due to noise with small helical rotations, a minimal amount of rotation was defined in order to accurately determine the torsion axis location. Using simulation, the location of the axis based on data containing noise was compared to the axis location of data without noise with a one-sample t-test and Fisher's combined probability score. When using only data with helical rotation of seven degrees or more, the location of the torsion axis based on the data with noise was within 0.2 mm of the reference location. Therefore, the proposed method allowed an accurate calculation of the foot torsion axis location.
Graf, Eveline S; Wright, Ian C; Stefanyshyn, Darren J
2012-01-01
The two main movements occurring between the forefoot and rearfoot segment of a human foot are flexion at the metatarsophalangeal joints and torsion in the midfoot. The location of the torsion axis within the foot is currently unknown. The purpose of this study was to develop a method based on Cardan angles and the finite helical axis approach to calculate the torsion axis without the effect of flexion. As the finite helical axis method is susceptible to error due to noise with small helical rotations, a minimal amount of rotation was defined in order to accurately determine the torsion axis location. Using simulation, the location of the axis based on data containing noise was compared to the axis location of data without noise with a one-sample t-test and Fisher's combined probability score. When using only data with helical rotation of seven degrees or more, the location of the torsion axis based on the data with noise was within 0.2 mm of the reference location. Therefore, the proposed method allowed an accurate calculation of the foot torsion axis location.
Off-axis Modal Active Vibration Control Of Rotational Vibrations
Babakhani, B.; de Vries, Theodorus J.A.; van Amerongen, J.
Collocated active vibration control is an effective and robustly stable way of adding damping to the performance limiting vibrations of a plant. Besides the physical parameters of the Active Damping Unit (ADU) containing the collocated actuator and sensor, its location with respect to the
Alfven eigenmode structure during off-axis neutral beam injection
Tobias, B.; Bass, E. M.; Classen, I.G.J.; Domier, C.W.; Grierson, B. A.; Heidbrink, W. W.; N C Luhmann Jr.,; Nazikian, R.; Park, H. K.; Spong, D. A.; VanZeeland, M. A.
2012-01-01
The spatial structure of Alfven eigenmodes on the DIII-D tokamak is compared for contrasting fast ion deposition profiles resulting from on- and off-axis neutral beam injection (NBI). In both cases, poloidal mode rotation and eigenmode twist, or radial phase variation, are correlated with the direct
Studying rotational dynamics with a smartphone—accelerometer versus gyroscope
Braskén, Mats; Pörn, Ray
2017-07-01
The wide-spread availability of smartphones makes them a valuable addition to the measurement equipment of both the physics classroom and the instructional physics laboratory, encouraging an active interaction between measurements and modeling activities. Two useful sensors, available in most modern smartphones and tablets, are the 3-axis acceleration sensor and the 3-axis gyroscope. We explore the strengths and weaknesses of each type of sensor and use them to study the rotational dynamics of objects rotating about a fixed axis. Care has to be taken when interpreting acceleration sensor data, and in some cases the gyroscope will allow for rotational measurements not easily replicated using the acceleration sensor.
Krivcov, Vladimir [Miass, RU; Krivospitski, Vladimir [Miass, RU; Maksimov, Vasili [Miass, RU; Halstead, Richard [Rohnert Park, CA; Grahov, Jurij [Miass, RU
2011-03-08
A vertical axis wind turbine is described. The wind turbine can include a top ring, a middle ring and a lower ring, wherein a plurality of vertical airfoils are disposed between the rings. For example, three vertical airfoils can be attached between the upper ring and the middle ring. In addition, three more vertical airfoils can be attached between the lower ring and the middle ring. When wind contacts the vertically arranged airfoils the rings begin to spin. By connecting the rings to a center pole which spins an alternator, electricity can be generated from wind.
The rotational memory effect of a multimode fiber
Amitonova, L V; Pinkse, P W H
2015-01-01
We demonstrate the rotational memory effect in a multimode fiber. Rotating the incident wavefront around the fiber core axis leads to a rotation of the resulting pattern of the fiber output without significant changes in the resulting speckle pattern. The rotational memory effect can be exploited for non-invasive imaging or ultrafast high-resolution scanning through a multimode fiber. Our experiments demonstrate this effect over a full range of angles in two experimental configurations.
The infrared bands Pechan prism axis parallel detection method
Qiang, Hua; Ji, Ming; He, Yu-lan; Wang, Nan-xi; Chang, Wei-jun; Wang, Ling; Liu, Li
2017-02-01
In this paper, we put forward a new method to adjust the air gap of the total reflection air gap of the infrared Pechan prism. The adjustment of the air gap in the air gap of the Pechan prism directly affects the parallelism of the optical axis, so as to affect the consistency of the optical axis of the infrared system. The method solves the contradiction between the total reflection and the high transmission of the infrared wave band, and promotes the engineering of the infrared wave band. This paper puts forward the method of adjusting and controlling, which can ensure the full reflection and high penetration of the light, and also can accurately measure the optical axis of the optical axis of the different Pechan prism, and can achieve the precision of the level of the sec. For Pechan prism used in the infrared band image de rotation, make the product to realize miniaturization, lightweight plays an important significance.
Using the axis of elongation to align shapes: Developmental changes between 18 and 24 months
Smith, Linda B.; Street, Sandra; Jones, Susan S.; James, Karin H.
2014-01-01
An object’s axis of elongation serves as an important frame of reference for forming 3-dimensional representations of object shape. By several recent accounts, the formation of these representations is also related to experiences of acting on objects. Four experiments examined 18- to 24-month-old (N = 103) infants’ sensitivity to the elongated axis in action tasks that required extracting, comparing and physically rotating an object so that its major axis was aligned with that of a visual sta...
Land, K; Land, Kate; Magueijo, Joao
2005-01-01
We examine previous claims for a preferred axis at $(b,l)\\approx (60,-100)$ in the cosmic radiation anisotropy, by generalizing the concept of multipole planarity to any shape preference (a concept we define mathematically). Contrary to earlier claims, we find that the amount of power concentrated in planar modes for $\\ell=2,3$ is not inconsistent with isotropy and Gaussianity. The multipoles' alignment, however, is indeed anomalous, and extends up to $\\ell=5$ rejecting statistical isotropy with a probability in excess of 99.9%. There is also an uncanny correlation of azimuthal phases between $\\ell=3$ and $\\ell=5$. We are unable to blame these effects on foreground contamination or large-scale systematic errors. We show how this reappraisal may be crucial in identifying the theoretical model behind the anomaly.
Zhao, Wen
2016-01-01
The foundation of modern cosmology relies on the so-called cosmological principle which states an homogeneous and isotropic distribution of matter in the universe on large scales. However, recent observations, such as the temperature anisotropy of the cosmic microwave background (CMB) radiation, the motion of galaxies in the universe, the polarization of quasars and the acceleration of the cosmic expansion, indicate preferred directions in the sky. If these directions have a cosmological origin, the cosmological principle would be violated, and modern cosmology should be reconsidered. In this paper, by considering the preferred axis in the CMB parity violation, we find that it coincides with the preferred axes in CMB quadrupole and CMB octopole, and they all align with the direction of the CMB kinematic dipole. In addition, the preferred directions in the velocity flows, quasar alignment, anisotropy of the cosmic acceleration, the handedness of spiral galaxies, and the angular distribution of the fine-structu...
DEFF Research Database (Denmark)
Takai, Hirokazu; Konstantinidis, Lukas; Schmal, Hagen
2016-01-01
Purpose. Anderson type III odontoid fractures have traditionally been considered stable and treated conservatively. However, unstable cases with unfavorable results following conservative treatment have been reported. Methods. We present the cases of two patients who sustained minimally displaced...... Anderson type III fractures with a characteristic fracture pattern that we refer to as "oblique type axis body fracture." Results. The female patients aged 90 and 72 years, respectively, were both diagnosed with minimally displaced Anderson type III fractures. Both fractures had a characteristic "oblique...... type" fracture pattern. The first patient was treated conservatively with cervical spine immobilization in a semirigid collar. However, gross displacement was noted at the 6-week follow-up visit. The second patient was therefore treated operatively by C1-C3/4 posterior fusion and the course...
Numerical simulations of rotating axisymmetric sunspots
Botha, G. J. J.; Busse, F.H.; Hurlburt, N. E.; Rucklidge, A.M.
2008-01-01
A numerical model of axisymmetric convection in the presence of a vertical magnetic flux bundle and rotation about the axis is presented. The model contains a compressible plasma described by the nonlinear MHD equations, with density and temperature gradients simulating the upper layer of the sun's convection zone. The solutions exhibit a central magnetic flux tube in a cylindrical numerical domain, with convection cells forming collar flows around the tube. When the numerical domain is rotat...
Electromagnetism of rotating conductors revisited
Energy Technology Data Exchange (ETDEWEB)
Redzic, Dragan V. [Faculty of Physics, University of Belgrade, Belgrade (Yugoslavia)]. E-mail: redzic@ff.bg.ac.yu
2002-03-01
The charge distribution and electromagnetic fields in a rotating, charged conductor under stationary conditions are investigated, assuming that the electrons are at rest relative to the conductor. The basic equations are found, referred to the inertial rest frame of the rotational axis, in the relativistic case, and applied to the case of a cylindrical conductor. The results obtained are compared with those of Groen and Voeyenli (Groen Oe and Voeyenli K 1982 Eur. J. Phys. 3 210-4) who considered the same problem but without taking into account the relative permittivity of the rotating conductor. It is found that the E- and B-fields do not depend on {epsilon}{sub r} and coincide with those calculated by Groen and Voeyenli; the space and surface charge densities, however, depend on {epsilon}{sub r}. (author)
Micromachined dual input axis rate gyroscope
Juneau, Thor Nelson
The need for inexpensive yet reliable angular rate sensors in fields ranging from automotive to consumer electronics has motivated prolific micromachined rate gyroscope research. The vast majority of research has focused on single input axis rate gyroscopes based upon either translational resonance, such as tuning forks, or structural mode resonance, such as vibrating rings. However, this work presents a novel, contrasting approach based on angular resonance of a rotating rigid rotor suspended by torsional springs. The inherent symmetry of the circular design allows angular rate measurement about two axes simultaneously, hence the name micromachined dual-axis rate gyroscope. The underlying theory of operation, mechanical structure design optimization, electrical interface circuitry, and signal processing are described in detail. Several operational versions were fabricated using two different fully integrated surface micromachining processes as proof of concept. The heart of the dual-axis rate gyroscope is a ˜2 mum thick polysilicon disk or rotor suspended above the substrate by a four beam suspension. When this rotor in driven into angular oscillation about the axis perpendicular to the substrate, a rotation rate about the two axes parallel to the substrate invokes an out of plane rotor tilting motion due to Coriolis acceleration. This tilting motion is capacitively measured and on board integrated signal processing provides two output voltages proportional to angular rate input about the two axes parallel to the substrate. The design process begins with the derivation of gyroscopic dynamics. The equations suggest that tuning sense mode frequencies to the drive oscillation frequency can vastly increase mechanical sensitivity. Hence the supporting four beam suspension is designed such that electrostatic tuning can match modes despite process variations. The electrostatic tuning range is limited only by rotor collapse to the substrate when tuning-voltage induced
Calculation of pediatric femoral fracture rotation from direct roentgenograms.
Ozel, M S; Ketenci, I E; Kaya, E; Tuna, S; Saygi, B
2013-12-01
Radiologic determination of pediatric femoral fracture rotation has been debated. Measuring the antetorsion angle of the fractured femur by computed tomography and comparing it with the opposite side has been the method of choice for this purpose. However, no simple method for direct measurement of femoral fracture rotation exists in the literature. In this study, our aim was to test a mathematical method of measuring the axial plane malrotation from direct roentgenograms. A pediatric femoral shaft fracture model was produced. The bone was secured to a wooden frame that allowed the distal part of the fracture to rotate around an axis. Radiographs were taken at known intervals of rotation ranging from the neutral position to 60° external rotation and to 60° internal rotation in 5° increments of rotation. Five independent, blinded observers measured the radiographs and calculated the fracture rotation according to a standard formula. Calculated rotation values were compared with known rotation values. Calculated rotation values were close to actual rotation values throughout the arc of rotation. The mean absolute error of five observers for all measurements of external and internal rotation was 3.97° (±0.83). The correlation coefficient between calculated and actual rotation values was 0.9927. The interobserver intraclass correlation coefficient for calculated rotation was 0.997. Absolute error and correlation coefficient values indicate that this method is accurate and reliable in determining the fracture rotation.
Automatic Identification of Axis Orbit Based on Both Wavelet Moment Invariants and Neural Network
Institute of Scientific and Technical Information of China (English)
FuXiang-qian; LiuGuang-lin; JiangJing; LiYou-ping
2003-01-01
Axis orbit is an important characteristic to be used in the condition monitoring and diagnosis system of rotating machine. The wavelet moment has the invariant to the translation, scaling and rotation. A method, which uses a neural network based on Radial Basis Function (RBF) and wavelet moment invariants to identify the orbit of shaft centerline of rotating machine is discussed in this paper. The principle and its application procedure of the method are introduced in detail. It gives simulation results of automatic identification for three typical axis orbits. It is proved that the method is effective and practicable.
Automatic Identification of Axis Orbit Based on Both Wavelet Moment Invariants and Neural Network
Institute of Scientific and Technical Information of China (English)
Fu Xiang-qian; Liu Guang-lin; Jiang Jing; Li You-ping
2003-01-01
Axis orbit is an important characteristic to be used in the condition monitoring and diagnosis system of rota-ting machine. The wavelet moment has the invariant to the translation, scaling and rotation. A method, which uses a neural network based on Radial Basis Function (RBF) and wavelet moment invariants to identify the orbit of shaft centerline of rotating machine is discussed in this paper. The principle and its application procedure of the method are intro-duced in detail. It gives simulation results of automatic identi-fication for three typical axis orbits. It is proved that the method is effective and practicable.
Static Atmospheres in a Rotating Space Habitat.
McKinley, John M.
1980-01-01
Discusses O'Neill's proposal for the colonization of space as it offers new problems in pure physics. Addresses specifically the distribution of the atmosphere in O'Neill's habitat and whether there will be enough air at the axis of rotation to allow human-powered flight, with particular reference to the habitat's "artificial gravity."…
Automated Shell Theory for Rotating Structures (ASTROS)
Foster, B. J.; Thomas, J. M.
1973-01-01
Computer program can be used to analyze any disk or shell of revolution of arbitrary cross section under inertial loads caused by rotation about shell axis and under various static loads, including thermal gradients. Geometric shapes incorporated in program are ellipsoidal, spherical, ogival, toroidal, conical, circular plate, cylindrical, and parabolic.
Isosynchronous paths on a rotating surface
Ashby, Neil
2014-01-01
In special relativity, clock networks may be self-consistently synchronized in an inertial frame by slowly transporting clocks, or by exchanging electromagnetic signals between network nodes. However, clocks at rest in a rotating coordinate system--such as on the surface of the rotating earth--cannot be self-consistently synchronized by such processes, due to the Sagnac effect. Discrepancies that arise are proportional to the area swept out by a vector from the rotation axis to the portable clock or electromagnetic pulse, projected onto a plane normal to the rotation axis. This raises the question whether paths of minimal or extremal length can be found, for which the Sagnac discrepancies are zero. This paper discusses the variational problem of finding such "isosynchronous" paths on rotating discs and rotating spheres. On a disc, the problem resembles the classical isoperimetric problem and the paths turn out to be circular arcs. On a rotating sphere, however, between any two endpoints there are an infinite ...
Invalidity of Geometrical Interpretation of F-Spin Structure of Nuclear Rotations by Otsuka's View
Long, Guilu
1995-06-01
In Otsuka's view of nuclear rotations neutrons and protons are not rotating around a common axis, but rather around separate axis. In this letter, we pointed out that this invalidates the geometrical interpretation of F-spin structure of the neutron-proton interacting boson model, where the angle between the axis of symmetries of neutron ellipsoid and proton ellipsoid is used to determine whether a state is F-spin symmetric or mixed symmetric.
Transient Simulation of a Rotating Conducting Cylinder in a Transverse Magnetic Field
2016-09-01
analysis. Therefore, the magnitude and direction (phase shift angle) of the magnetic flux density vector at the center of the cylinder’s axis of...UNCLASSIFIED 2 sensor used to measure the magnitude and direction (angle) of a magnetic field, was placed at the center of the cylinder’s axis of rotation for...vector at the center of the cylinder’s axis of rotation was evaluated. The factors that may affect the eddy current interactions and magnetic field
Differential Rotation in Solar Convective Dynamo Simulations
Fan, Yuhong
2015-01-01
We carry out a magneto-hydrodynamic (MHD) simulation of convective dynamo in the rotating solar convective envelope driven by the solar radiative diffusive heat flux. The simulation is similar to that reported in Fan & Fang (2014) but with further reduced viscosity and magnetic diffusion. The resulting convective dynamo produces a large scale mean field that exhibits similar irregular cyclic behavior and polarity reversals, and self-consistently maintains a solar-like differential rotation. The main driver for the solar-like differential rotation (with faster rotating equator) is a net outward transport of angular momentum away from the rotation axis by the Reynolds stress, and we found that this transport is enhanced with reduced viscosity and magnetic diffusion.
Destabilization of free convection by weak rotation
Gelfgat, Alexander
2011-01-01
This study offers an explanation of a recently observed effect of destabilization of free convective flows by weak rotation. After studying several models where flows are driven by a simultaneous action of convection and rotation, it is concluded that the destabilization is observed in the cases where centrifugal force acts against main convective circulation. At relatively low Prandtl numbers this counter action can split the main vortex into two counter rotating vortices, where the interaction leads to instability. At larger Prandtl numbers, the counter action of the centrifugal force steepens an unstable thermal stratification, which triggers Rayleigh-B\\'enard instability mechanism. Both cases can be enhanced by advection of azimuthal velocity disturbances towards the axis, where they grow and excite perturbations of the radial velocity. The effect was studied considering a combined convective/rotating flow in a cylinder with a rotating lid and a parabolic temperature profile at the sidewall. Next, explana...
Differential rotation in solar convective dynamo simulations
Fan, Yuhong; Fang, Fang
2016-10-01
We carry out a magneto-hydrodynamic (MHD) simulation of convective dynamo in the rotating solar convective envelope driven by the solar radiative diffusive heat flux. The simulation is similar to that reported in Fan and Fang (2014) but with further reduced viscosity and magnetic diffusion. The resulting convective dynamo produces a large scale mean field that exhibits similar irregular cyclic behavior and polarity reversals, and self-consistently maintains a solar-like differential rotation. The main driver for the solar-like differential rotation (with faster rotating equator) is a net outward transport of angular momentum away from the rotation axis by the Reynolds stress, and we found that this transport is enhanced with reduced viscosity and magnetic diffusion.
A new device for blockout procedures in rotational path removable partial dentures.
Luk, K C; Chen, P S
1993-05-01
The rationale of a rotation axis is discussed and on this basis a blockout device is designed for rotational path removable partial dentures. This device has three basic components, which are (1) the acrylic resin block, (2) the rotation axis, and (3) the functional part. In the blockout procedures for removable partial dentures with tilted mandibular molars, the rotation axis of the prosthesis is first localized by the blockout device. A knife edge, made of Duralay resin that corresponds to the survey lines of teeth to be used as supports, is constructed and is joined to the functional part of the blockout device. Blockout regions are determined by the rotational movement of the Duralay resin knife edge along the rotation axis of the blockout device. In addition to the function of blockout, the device can also be used to analyze diagnostic casts for critical undercuts. Internal and external types of blockout devices are also discussed.
Energy Transfer in Rotating Turbulence
Cambon, Claude; Mansour, Nagi N.; Godeferd, Fabien S.; Rai, Man Mohan (Technical Monitor)
1995-01-01
The influence or rotation on the spectral energy transfer of homogeneous turbulence is investigated in this paper. Given the fact that linear dynamics, e.g. the inertial waves regime tackled in an RDT (Rapid Distortion Theory) fashion, cannot Affect st homogeneous isotropic turbulent flow, the study of nonlinear dynamics is of prime importance in the case of rotating flows. Previous theoretical (including both weakly nonlinear and EDQNM theories), experimental and DNS (Direct Numerical Simulation) results are gathered here and compared in order to give a self-consistent picture of the nonlinear effects of rotation on tile turbulence. The inhibition of the energy cascade, which is linked to a reduction of the dissipation rate, is shown to be related to a damping due to rotation of the energy transfer. A model for this effect is quantified by a model equation for the derivative-skewness factor, which only involves a micro-Rossby number Ro(sup omega) = omega'/(2(OMEGA))-ratio of rms vorticity and background vorticity as the relevant rotation parameter, in accordance with DNS and EDQNM results fit addition, anisotropy is shown also to develop through nonlinear interactions modified by rotation, in an intermediate range of Rossby numbers (Ro(omega) = (omega)' and Ro(omega)w greater than 1), which is characterized by a marco-Rossby number Ro(sup L) less than 1 and Ro(omega) greater than 1 which is characterized by a macro-Rossby number based on an integral lengthscale L and the micro-Rossby number previously defined. This anisotropy is mainly an angular drain of spectral energy which tends to concentrate energy in tile wave-plane normal to the rotation axis, which is exactly both the slow and the two-dimensional manifold. In Addition, a polarization of the energy distribution in this slow 2D manifold enhances horizontal (normal to the rotation axis) velocity components, and underlies the anisotropic structure of the integral lengthscales. Finally is demonstrated the
Rotation-independent representations for haptic movements
Shioiri, Satoshi; Yamazaki, Takanori; Matsumiya, Kazumichi; Kuriki, Ichiro
2013-01-01
The existence of a common mechanism for visual and haptic representations has been reported in object perception. In contrast, representations of movements might be more specific to modalities. Referring to the vertical axis is natural for visual representations whereas a fixed reference axis might be inappropriate for haptic movements and thus also inappropriate for its representations in the brain. The present study found that visual and haptic movement representations are processed independently. A psychophysical experiment examining mental rotation revealed the well-known effect of rotation angle for visual representations whereas no such effect was found for haptic representations. We also found no interference between processes for visual and haptic movements in an experiment where different stimuli were presented simultaneously through visual and haptic modalities. These results strongly suggest that (1) there are separate representations of visual and haptic movements, and (2) the haptic process has a rotation-independent representation. PMID:24005481
Visual perception of axes of head rotation
Directory of Open Access Journals (Sweden)
David Mattijs Arnoldussen
2013-02-01
Full Text Available Registration of ego-motion is important to accurately navigate through space. Movements of the head and eye relative to space are registered through the vestibular system and optical flow, respectively. Here, we address three questions concerning the visual registration of self-rotation. 1. Eye-in-head movements provide a link between the motion signals received by sensors in the moving eye and sensors in the moving head. How are these signals combined into an ego-rotation percept? We combined optic flow of simulated forward and rotational motion of the eye with different levels of eye-in-head rotation for a stationary head. We dissociated simulated gaze rotation and head rotation by different levels of eye-in-head pursuit.We found that perceived rotation matches simulated head- not gaze-rotation. This rejects a model for perceived self-rotation that relies on the rotation of the gaze line. Rather, eye-in-head signals serve to transform the optic flow’s rotation information, that specifies rotation of the scene relative to the eye, into a rotation relative to the head. This suggests that transformed visual self-rotation signals may combine with vestibular signals.2. Do transformed visual self-rotation signals reflect the arrangement of the semicircular canals (SCC? Previously, we found sub-regions within MST and V6+ that respond to the speed of the simulated head rotation. Here, we re-analyzed those BOLD signals for the presence of a spatial dissociation related to the axes of visually simulated head rotation, such as have been found in sub-cortical regions of various animals. Contrary, we found a rather uniform BOLD response to simulated rotation along the three SCC axes.3. We investigated if subject’s sensitivity to the direction of the head rotation axis shows SCC axes specifcity. We found that sensitivity to head rotation is rather uniformly distributed, suggesting that in human cortex, visuo-vestibular integration is not arranged into
Gulshani, P
2016-01-01
A simple derivation from first principles of the conventional cranking model for nuclear collective rotation about a single axis and its coupling to intrinsic motion is given. The microscopic cranking model is derived by transforming the nuclear Schrodinger equation to a rotating frame using a rotation-intrinsic product wavefunction and imposing no constraints on either the wavefunction or the nucleon coordinates. The no-constraint feature of the transformation makes it possible to share the angular momentum of the nucleus between the rotating frame and intrinsic system. The rotation of the frame is driven by a combination of rigid and irrotational flows generated by the motion of the nucleons. The resulting transformed, time-reversal invariant Schrodinger equation is readily reduced to the equations of the conventional cranking, particle-plus-rotor, phenomenological and microscopic collective rotation-vibration, and two-fluid semi-classical collective models. In particular, the reduction of the microscopic m...
2016-01-01
Objective: To systematically review the updated information about the gut microbiota-brain axis. Data Sources: All articles about gut microbiota-brain axis published up to July 18, 2016, were identified through a literature search on PubMed, ScienceDirect, and Web of Science, with the keywords of “gut microbiota”, “gut-brain axis”, and “neuroscience”. Study Selection: All relevant articles on gut microbiota and gut-brain axis were included and carefully reviewed, with no limitation of s...
Rotation of vertically oriented objects during earthquakes
Hinzen, Klaus-G.
2012-10-01
Vertically oriented objects, such as tombstones, monuments, columns, and stone lanterns, are often observed to shift and rotate during earthquake ground motion. Such observations are usually limited to the mesoseismal zone. Whether near-field rotational ground motion components are necessary in addition to pure translational movements to explain the observed rotations is an open question. We summarize rotation data from seven earthquakes between 1925 and 2009 and perform analog and numeric rotation testing with vertically oriented objects. The free-rocking motion of a marble block on a sliding table is disturbed by a pulse in the direction orthogonal to the rocking motion. When the impulse is sufficiently strong and occurs at the `right' moment, it induces significant rotation of the block. Numeric experiments of a free-rocking block show that the initiation of vertical block rotation by a cycloidal acceleration pulse applied orthogonal to the rocking axis depends on the amplitude of the pulse and its phase relation to the rocking cycle. Rotation occurs when the pulse acceleration exceeds the threshold necessary to provoke rocking of a resting block, and the rocking block approaches its equilibrium position. Experiments with blocks subjected to full 3D strong motion signals measured during the 2009 L'Aquila earthquake confirm the observations from the tests with analytic ground motions. Significant differences in the rotational behavior of a monolithic block and two stacked blocks exist.
Numerical and Experimental Investigations of a Rotating Heat Pipe
Energy Technology Data Exchange (ETDEWEB)
Jankowski, Todd A. [Univ. of New Mexico, Albuquerque, NM (United States)
2007-05-01
Rotating and revolving heat pipes have been used in a variety of applications including heat pipe heat exchangers, cooling of rotating electrical machines, and heat removal in high speed cutting operations. The use of heat pipes in rotating environments has prompted many analytical, numerical, and experimental investigations of the heat transfer characteristics of these devices. Past investigations, however, have been restricted to the study of straight heat pipes. In this work, a curved rotating heat pipe is studied numerically and experimentally. In certain types of rotating machines, heat generating components, which must be cooled during normal operation, are located at some radial distance from the axis of rotation. The bent heat pipe studied here is shown to have advantages when compared to the conventional straight heat pipes in these off-axis cooling scenarios. The heat pipe studied here is built so that both the condenser and evaporator sections are parallel to the axis of rotation. The condenser section is concentric with the axis of rotation while the evaporator section can be placed in contact with off-axis heat sources in the rotating machine. The geometry is achieved by incorporating an S-shaped curve between the on-axis rotating condenser section and the off-axis revolving evaporator section. Furthermore, the heat pipe uses an annular gap wick structure. Incorporating an annular gap wick structure into the heat pipe allows for operation in a non-rotating environment. A numerical model of this rotating heat pipe is developed. The analysis is based on a two-dimensional finite-difference model of the liquid flow coupled to a one-dimensional model of the vapor flow. Although the numerical model incorporates many significant aspects of the fluid flow, the flow in the actual heat pipe is expected to be threedimensional. The rotating heat pipe with the S-shaped curve is also studied experimentally to determine how well the numerical model captures the key
Modal Parameter Identification of New Design of Vertical Axis Wind Turbine
DEFF Research Database (Denmark)
Chougule, Prasad; Nielsen, Søren R.K.
2013-01-01
Vertical axis wind turbines have lower power efficiency than the horizontal axis wind turbines. However vertical axis wind turbines are proven to be economical and noise free on smaller scale. A new design of three bladed vertical axis wind turbine by using two airfoils in construction of each...... blade has been proposed to improve power efficiency. The purpose of two airfoils in blade design of vertical axis wind turbine is to create high lift which in turns gives higher power output. In such case the structural parameter identification is important to understand the system behavior due to its...... first kind of design before experimental analysis. Therefore a study is carried out to determine the natural frequency to avoid unstable state of the system due to rotational frequency of rotor. The present paper outlines a conceptual design of vertical axis wind turbine and a modal analysis by using...
Modal Parameter Identification of New Design of Vertical Axis Wind Turbine
DEFF Research Database (Denmark)
Chougule, Prasad; Nielsen, Søren R.K.
2013-01-01
Vertical axis wind turbines have lower power efficiency than the horizontal axis wind turbines. However vertical axis wind turbines are proven to be economical and noise free on smaller scale. A new design of three bladed vertical axis wind turbine by using two airfoils in construction of each...... blade has been proposed to improve power efficiency. The purpose of two airfoils in blade design of vertical axis wind turbine is to create high lift which in turns gives higher power output. In such case the structural parameter identification is important to understand the system behavior due to its...... first kind of design before experimental analysis. Therefore a study is carried out to determine the natural frequency to avoid unstable state of the system due to rotational frequency of rotor. The present paper outlines a conceptual design of vertical axis wind turbine and a modal analysis by using...
The chaotic rotation of Hyperion
Wisdom, J.; Peale, S. J.; Mignard, F.
1984-01-01
Under the assumption that the satellite is rotating about a principal axis that is normal to its orbit plane, a plot of spin rate-versus-orientation for Hyperion at the pericenter of its orbit has revealed a large, chaotic zone surrounding Hyperion's synchronous spin-orbit state. The chaotic zone is so large that it surrounds the 1/2 and 2 states, and libration in the 3/2 state is not possible. Rotation in the chaotic zone is also attitude-unstable. As tidal dissipation drives Hyperion's spin toward a nearly synchronous value, Hyperion necessarily enters the large chaotic zone, becoming attitude-unstable and tumbling. It is therefore predicted that Hyperion will be found to be tumbling chaotically.
Whirling skirts and rotating cones
Guven, Jemal; Müller, Martin Michael
2013-01-01
Steady, dihedrally symmetric patterns with sharp peaks may be observed on a spinning skirt, lagging behind the material flow of the fabric. These qualitative features are captured with a minimal model of traveling waves on an inextensible, flexible, generalized-conical sheet rotating about a fixed axis. Conservation laws are used to reduce the dynamics to a quadrature describing a particle in a three-parameter family of potentials. One parameter is associated with the stress in the sheet, the second is the Noether current associated with rotational invariance, and the third is a Rossby number which indicates the relative strength of Coriolis forces. Solutions are quantized by enforcing a topology appropriate to a skirt and a particular choice of dihedral symmetry. A perturbative analysis of nearly axisymmetric cones shows that Coriolis effects are essential in establishing skirt-like solutions. Fully non-linear solutions with three-fold symmetry are presented, which bear a suggestive resemblance to the observ...
Psoas major and its controversial rotational action.
Skyrme, A D; Cahill, D J; Marsh, H P; Ellis, H
1999-01-01
The action of psoas major muscle as a primary flexor of the hip joint is undisputed. However it is also variably reported as being a medial and a lateral rotator of the femur at the hip joint. The psoas and iliacus muscles, along with their common insertion, were isolated by dissection in six adult cadaveric specimens. The action of psoas muscle was assessed by pulling the muscle along its long axis and then observing the effects on rotation of the femur, with a visual estimation of the rotation in degrees. The experiment was repeated with the hip joint capsule removed. In the anatomical position, applied traction along the long axis of the muscle produced hip flexion with no rotational component. With the hip in the abducted position, traction produced flexion, adduction, and lateral rotation of the femur at the hip joint. In adduction of the hip, traction on psoas produced only flexion at the hip joint, with no rotation. In maximal flexion, traction also produced adduction. The results were unaffected by the removal of the joint capsule.
Coupling Onset of Cyclone Upward and Rotation Flows in a Little Bottle
Kawata, Shigeo
2012-01-01
A coupling onset of the cyclone upward and rotation flows is experimentally demonstrated in a little bottle. The rotating flow provides a pressure increase in the outer part of the rotating flow by its centrifugal force. When a gradient of the fluid rotation appears along the rotation axis, the higher-pressure area is localized and pushes the fluid in a low pressure. Then the fluid staying in the central area of the rotation is pushed up along the rotation axis, and the upward wind is enhanced. In this coupling mechanism the rotation gradient is the key; the coupling of the rotation and the upward fluid flow is essentially important for a cyclone buildup, and is well explained experimentally and theoretically.
The role of Stewartson and Ekman layers in turbulent rotating Rayleigh-Bénard convection
Kunnen, Rudie P.J.; Stevens, Richard Johannes Antonius Maria; Overkamp, Jim; Sun, Chao; van Heijst, GertJan F.; Clercx, H.J.H.
2011-01-01
When the classical Rayleigh–Bénard (RB) system is rotated about its vertical axis roughly three regimes can be identified. In regime I (weak rotation) the largescale circulation (LSC) is the dominant feature of the flow. In regime II (moderate rotation) the LSC is replaced by vertically aligned
Institute of Scientific and Technical Information of China (English)
Hong-Xing Wang; Yu-Ping Wang
2016-01-01
Objective:To systematically review the updated information about the gut microbiota-brain axis.Data Sources:All articles about gut microbiota-brain axis published up to July 18,2016,were identified through a literature search on PubMed,ScienceDirect,and Web of Science,with the keywords of"gut microbiota","gut-brain axis",and "neuroscience".Study Selection:All relevant articles on gut microbiota and gut-brain axis were included and carefully reviewed,with no limitation of study design.Results:It is well-recognized that gut microbiota affects the brain's physiological,behavioral,and cognitive functions although its precise mechanism has not yet been fully understood.Gut microbiota-brain axis may include gut microbiota and their metabolic products,enteric nervous system,sympathetic and parasympathetic branches within the autonomic nervous system,neural-immune system,neuroendocrine system,and central nervous system.Moreover,there may be five communication routes between gut microbiota and brain,including the gut-brain's neural network,neuroendocrine-hypothalamic-pituitary-adrenal axis,gut immune system,some neurotransmitters and neural regulators synthesized by gut bacteria,and barrier paths including intestinal mucosal barrier and blood-brain barrier.The microbiome is used to define the composition and functional characteristics of gut microbiota,and metagenomics is an appropriate technique to characterize gut microbiota.Conclusions:Gut microbiota-brain axis refers to a bidirectional information network between the gut microbiota and the brain,which may provide a new way to protect the brain in the near future.
Effect of gravity level fluctuations for rotating fluids in high and low rotating speeds
Hung, R. J.; Tsao, Y. D.; Hong, B. B.; Leslie, F. W.
1989-01-01
Time-dependent evolutions of the profile of the free surface (bubble shapes) for a cylindrical container partially filled with a Newtonian fluid of constant density, rotating about its axis of symmetry, have been studied. Numerical computations of the dynamics of bubble shapes have been carried out with sinusoidal-function vibration of the gravity environment at high and low cylinder speeds.
Burmann, Britta; Dehnhardt, Guido; Mauck, Björn
2005-01-01
Mental rotation is a widely accepted concept indicating an image-like mental representation of visual information and an analogue mode of information processing in certain visuospatial tasks. In the task of discriminating between image and mirror-image of rotated figures, human reaction times increase with the angular disparity between the figures. In animals, tests of this kind yield inconsistent results. Pigeons were found to use a time-independent rotational invariance, possibly indicating a non-analogue information processing system that evolved in response to the horizontal plane of reference birds perceive during flight. Despite similar ecological demands concerning the visual reference plane, a sea lion was found to use mental rotation in similar tasks, but its processing speed while rotating three-dimensional stimuli seemed to depend on the axis of rotation in a different way than found for humans in similar tasks. If ecological demands influence the way information processing systems evolve, hominids might have secondarily lost the ability of rotational invariance while retreating from arboreal living and evolving an upright gait in which the vertical reference plane is more important. We therefore conducted mental rotation experiments with an arboreal living primate species, the lion-tailed macaque. Performing a two-alternative matching-to-sample procedure, the animal had to decide between rotated figures representing image and mirror-image of a previously shown upright sample. Although non-rotated stimuli were recognized faster than rotated ones, the animal's mean reaction times did not clearly increase with the angle of rotation. These results are inconsistent with the mental rotation concept but also cannot be explained assuming a mere rotational invariance. Our study thus seems to support the idea of information processing systems evolving gradually in response to specific ecological demands.
A mechanical rotator for neutron scattering measurements
Thaler, A.; Northen, E.; Aczel, A. A.; MacDougall, G. J.
2016-12-01
We have designed and built a mechanical rotation system for use in single crystal neutron scattering experiments at low temperatures. The main motivation for this device is to facilitate the application of magnetic fields transverse to a primary training axis, using only a vertical cryomagnet. Development was done in the context of a triple-axis neutron spectrometer, but the design is such that it can be generalized to a number of different instruments or measurement techniques. Here, we discuss some of the experimental constraints motivating the design, followed by design specifics, preliminary experimental results, and a discussion of potential uses and future extension possibilities.
Revisit of rotational dynamics of Asteroid 4179 Toutatis from Chang'e-2's flyby
Zhao, Yuhui; Hu, Shoucun; Ji, Jianghui
2016-01-01
This paper presents analysis of the rotational parameters of Toutatis based on the observational results from Chang'e-2's close flyby. The 3-D shape model derived from ground-based radar observation is used to calculate the 3-1-3 Euler angles at the flyby epoch, which are evaluated to be -20.1° +/- 1°, 27.6° +/- 1° and 42.2° +/- 1°. The large amplitude of Toutatis' tumbling attitude is demonstrated to be the result of the large deviation of the angular momentum axis and the rotational axis. Two rotational periods are evaluated to be 5.38+/-0.03 days for rotation about the long axis and 7.40+/-0.03 days for precession of the long axis about the angular momentum vector based on Fourier analysis. These results provide a further understanding of rotational state of Toutatis.
Revisit of rotational dynamics of Asteroid 4179 Toutatis from Chang'e-2's flyby
Zhao, Yuhui; Ji, Jianghui
2015-01-01
This paper presents analysis of the rotational parameters of Toutatis based on the observational results from Chang'e-2's close flyby. The 3-D shape model derived from ground-based radar observation is used to calculate the 3-1-3 Euler angles at the flyby epoch, which are evaluated to be $-20.1^\\circ\\pm1^\\circ$, $27.6^\\circ\\pm1^\\circ$ and $42.2^\\circ\\pm1^\\circ$. The large amplitude of Toutatis' tumbling attitude is demonstrated to be the result of the large deviation of the angular momentum axis and the rotational axis. Two rotational periods are evaluated to be $5.38\\pm0.03$ days for rotation about the long axis and $7.40\\pm0.03$ days for precession of the long axis about the angular momentum vector based on Fourier analysis. These results provide a further understanding of rotational state of Toutatis.
Helical spin rotators and snakes for RHIC
Energy Technology Data Exchange (ETDEWEB)
Ptitsin, V.I.; Shatunov, Yu.M. [Budker Inst. of Nuclear Physics, Novosibirsk (Russian Federation); Peggs, S. [Brookhaven National Lab., Upton, NY (United States)
1995-05-01
The RHIC collider, now under construction at BNL, will have the possibility of polarized proton-proton collisions up to a beam energy of 250 Gev. Polarized proton beams of such high energy can be only obtained with the use of siberian snakes, a special kind of spin rotator that rotates the particle spin by 180{degree} around an axis lying in the horizontal plane. Siberian snakes help to preserve the beam polarization while numerous spin depolarizing resonances are crossed, during acceleration. In order to collide longitudinally polarized beams, it is also planned to install spin rotators around two interaction regions. This paper discusses snake and spin rotator designs based on sequences of four helical magnets. The schemes that were chosen to be applied at RHIC are presented.
Wang, Hong-Xing; Wang, Yu-Ping
2016-01-01
Objective: To systematically review the updated information about the gut microbiota-brain axis. Data Sources: All articles about gut microbiota-brain axis published up to July 18, 2016, were identified through a literature search on PubMed, ScienceDirect, and Web of Science, with the keywords of “gut microbiota”, “gut-brain axis”, and “neuroscience”. Study Selection: All relevant articles on gut microbiota and gut-brain axis were included and carefully reviewed, with no limitation of study design. Results: It is well-recognized that gut microbiota affects the brain's physiological, behavioral, and cognitive functions although its precise mechanism has not yet been fully understood. Gut microbiota-brain axis may include gut microbiota and their metabolic products, enteric nervous system, sympathetic and parasympathetic branches within the autonomic nervous system, neural-immune system, neuroendocrine system, and central nervous system. Moreover, there may be five communication routes between gut microbiota and brain, including the gut-brain's neural network, neuroendocrine-hypothalamic-pituitary-adrenal axis, gut immune system, some neurotransmitters and neural regulators synthesized by gut bacteria, and barrier paths including intestinal mucosal barrier and blood-brain barrier. The microbiome is used to define the composition and functional characteristics of gut microbiota, and metagenomics is an appropriate technique to characterize gut microbiota. Conclusions: Gut microbiota-brain axis refers to a bidirectional information network between the gut microbiota and the brain, which may provide a new way to protect the brain in the near future. PMID:27647198
... this page: //medlineplus.gov/ency/patientinstructions/000357.htm Rotator cuff exercises To use the sharing features on this ... gov/pubmed/25560729 . Read More Frozen shoulder Rotator cuff problems Rotator cuff repair Shoulder arthroscopy Shoulder CT scan Shoulder ...
Dipole Alignment in Rotating MHD Turbulence
Shebalin, John V.; Fu, Terry; Morin, Lee
2012-01-01
We present numerical results from long-term CPU and GPU simulations of rotating, homogeneous, magnetohydrodynamic (MHD) turbulence, and discuss their connection to the spherically bounded case. We compare our numerical results with a statistical theory of geodynamo action that has evolved from the absolute equilibrium ensemble theory of ideal MHD turbulence, which is based on the ideal MHD invariants are energy, cross helicity and magnetic helicity. However, for rotating MHD turbulence, the cross helicity is no longer an exact invariant, although rms cross helicity becomes quasistationary during an ideal MHD simulation. This and the anisotropy imposed by rotation suggests an ansatz in which an effective, nonzero value of cross helicity is assigned to axisymmetric modes and zero cross helicity to non-axisymmetric modes. This hybrid statistics predicts a large-scale quasistationary magnetic field due to broken ergodicity , as well as dipole vector alignment with the rotation axis, both of which are observed numerically. We find that only a relatively small value of effective cross helicity leads to the prediction of a dipole moment vector that is closely aligned (less than 10 degrees) with the rotation axis. We also discuss the effect of initial conditions, dissipation and grid size on the numerical simulations and statistical theory.
Experimental investigation of a rapidly rotating turbulent duct flow
Energy Technology Data Exchange (ETDEWEB)
Maartensson, G.E.; Johansson, A.V. [Department of Mechanics, KTH, 10044 Stockholm (Sweden); Gunnarsson, J. [Bombardier Transportation, Vaesteraas (Sweden); Moberg, H. [Alfa Laval, 14780 Tumba (Sweden)
2002-09-01
Rapidly rotating duct flow is studied experimentally with Rotation numbers in the interval. To achieve this, in combination with relatively high Reynolds numbers (5,000-30,000 based on the hydraulic radius), water was used as the working medium. Square and rectangular duct cross-sections were used and the angle between the rotation vector and the main axis of the duct was varied. The influence of the rotation on the pressure drop in the duct was investigated and suitable scalings of this quantity were studied. (orig.)
Unidirectional Heat Transport Driven by Rotating Cholesteric Droplets
Sato, Sayumi; Bono, Shinji; Tabe, Yuka
2017-02-01
When a cholesteric liquid crystal (LC) is submitted to a thermal gradient, it exhibits continuous director rotation. The phenomenon is called the Lehmann effect and is understood as a thermomechanical coupling in chiral LCs without mirror symmetry. Since the Lehmann effect is considered to possess time-reversal symmetry, one can expect the inverse process, i.e., rotating chiral LCs to pump heat along the rotational axis. We report the first observation of heat transport driven by rotating cholesteric droplets. This result suggests a new function of the cholesterics as a micro heat pump.
Directory of Open Access Journals (Sweden)
Dhanabal.R
2013-04-01
Full Text Available Electricity plays a key role now in our daily lives but the energy sources to electric power has been used in abundance and so researchers were compelled to find an alternate source of power leading to the discovery of solar energy. Solar energy is inexhaustible and eco-friendly and can be converted into electricityusing photovoltaic panels. These panels can be used in a fixed form or used in a solar tracking system for single axis as well as for dual axis. In a fixed form their efficiency is low since the panels will be tilted in a particular angle whereas in a tracking system the panel is made to move either in single axis or dual axis. In a single axis system the panel is moved in an east to west direction with respect to the sun and it has better efficiency than panels in fixed form. But in a dual axis system the panel is made to rotate in all four directions in accordance with the sun. And dual axis has proved to have more efficiency than both fixed panels and single axis system.
Rotating Cavitation Supression Project
National Aeronautics and Space Administration — FTT proposes development of a rotating cavitation (RC) suppressor for liquid rocket engine turbopump inducers. Cavitation instabilities, such as rotating...
Anatomical study of the gastrointestinal tract in free-living axis deer (Axis axis).
Pérez, W; Erdogan, S; Ungerfeld, R
2015-02-01
The macroscopic anatomy of the stomach and intestines of adult axis deer (Axis axis), a cervid species considered intermediate/mixed feeder, was observed and recorded. Nine adult wild axis deers of both sexes were used and studied by simple dissection. The ruminal papillae were distributed unevenly in the overall area of the inner surface of rumen and primarily were more large and abundant within the atrium. The ruminal pillars had no papillae. There was an additional ruminal pillar located between the right longitudinal and right coronary ventral pillars connected to the caudal pillar. No dorsal coronary pillars were found, and the ventral coronary pillars are connected. The reticulum was the third compartment in size, and the maximum height of the reticular crests was 1.0 mm. The Cellulae reticuli were not divided and rarely contained secondary crests. There were no Papillae unguiculiformes. The omasum was the smallest gastric compartment. The abomasum had about twelve spiral plicae, and a small pyloric torus was present. The intraruminal papillation was similar to those species that are characterized by a higher proportion of grass in their natural diet. The finding of the small reticular crests is typical for browser ruminants and was coincident with data reported for other deer. The comparative ratio of the small intestine to the large intestine was 1.69, in terms of length measurements in axis deer and appears below of the 'browser range'. We concluded that the gastrointestinal system of axis deer reflected similar morphological characteristics of the both types of ruminants: browser and grazer, and we consider it as an intermediate feeder. © 2014 Blackwell Verlag GmbH.
Automated segmentation of the human hippocampus along its longitudinal axis.
Lerma-Usabiaga, Garikoitz; Iglesias, Juan Eugenio; Insausti, Ricardo; Greve, Douglas N; Paz-Alonso, Pedro M
2016-09-01
The human hippocampal formation is a crucial brain structure for memory and cognitive function that is closely related to other subcortical and cortical brain regions. Recent neuroimaging studies have revealed differences along the hippocampal longitudinal axis in terms of structure, connectivity, and function, stressing the importance of improving the reliability of the available segmentation methods that are typically used to divide the hippocampus into its anterior and posterior parts. However, current segmentation conventions present two main sources of variability related to manual operations intended to correct in-scanner head position across subjects and the selection of dividing planes along the longitudinal axis. Here, our aim was twofold: (1) to characterize inter- and intra-rater variability associated with these manual operations and compare manual (landmark based) and automatic (percentage based) hippocampal anterior-posterior segmentation procedures; and (2) to propose and test automated rotation methods based on approximating the hippocampal longitudinal axis to a straight line (estimated with principal component analysis, PCA) or a quadratic Bézier curve (fitted with numerical methods); as well as an automated anterior-posterior hippocampal segmentation procedure based on the percentage-based method. Our results reveal that automated rotation and segmentation procedures, used in combination or independently, minimize inconsistencies generated by the accumulation of manual operations while providing higher statistical power to detect well-known effects. A Matlab-based implementation of these procedures is made publicly available to the research community. Hum Brain Mapp 37:3353-3367, 2016. © 2016 Wiley Periodicals, Inc.
Wood, Charles E; Walker, Claire-Dominique
2015-12-15
Stress is an integral part of life. Activation of the hypothalamus-pituitary-adrenal (HPA) axis in the adult can be viewed as mostly adaptive to restore homeostasis in the short term. When stress occurs during development, and specifically during periods of vulnerability in maturing systems, it can significantly reprogram function, leading to pathologies in the adult. Thus, it is critical to understand how the HPA axis is regulated during developmental periods and what are the factors contributing to shape its activity and reactivity to environmental stressors. The HPA axis is not a passive system. It can actively participate in critical physiological regulation, inducing parturition in the sheep for instance or being a center stage actor in the preparation of the fetus to aerobic life (lung maturation). It is also a major player in orchestrating mental function, metabolic, and cardiovascular function often reprogrammed by stressors even prior to conception through epigenetic modifications of gametes. In this review, we review the ontogeny of the HPA axis with an emphasis on two species that have been widely studied-sheep and rodents-because they each share many similar regulatory mechanism applicable to our understanding of the human HPA axis. The studies discussed in this review should ultimately inform us about windows of susceptibility in the developing brain and the crucial importance of early preconception, prenatal, and postnatal interventions designed to improve parental competence and offspring outcome. Only through informed studies will our public health system be able to curb the expansion of many stress-related or stress-induced pathologies and forge a better future for upcoming generations.
Instabilities of a rotating helical rod
Park, Yunyoung; Ko, William; Kim, Yongsam; Lim, Sookkyung
2016-11-01
Bacteria such as Escherichia coli and Vibrio alginolyticus have helical flagellar filament. By rotating a motor, which is located at the bottom end of the flagellar filament embedded in the cell body, CCW or CW, they swim forward or backward. We model a left-handed helix by the Kirchhoff rod theory and use regularized Stokes formulation to study an interaction between the surrounding fluid and the flagellar filament. We perform numerical studies focusing on relations between physical parameters and critical angular frequency of the motor, which separates overwhiring from twirling. We are also interested in the buckling instability of the hook, which is very flexible elastic rod. By measuring buckling angle, which is an angle between rotational axis and helical axis, we observe the effects of physical parameters on buckling of the hook.
Distribution of magnetically confined circumstellar matter in oblique rotators
Preuss, O; Holzwarth, V R; Solanki, S K
2004-01-01
We consider the mechanical equilibrium and stability of matter trapped in the magnetosphere of a rapidly rotating star. Assuming a dipolar magnetic field and arbitrary inclination of the magnetic axis with respect to the axis of rotation we find stable equilibrium positions a) in a (warped) disk roughly aligned with the magnetic equatorial plane and b) at two locations above and below the disk, whose distance from the star increases with decreasing inclination angle between dipole and rotation axis. The distribution of matter is not strongly affected by allowing for a spatial offset of the magnetic dipole. These results provide a possible explanation for some observations of corotating localized mass concentrations in hot magnetic stars.
Superdeformed rotational bands in the presence of Y44 deformation
Hamamoto, Ikuko; Mottelson, Ben
1994-08-01
The observation of ΔI = 4 staggering in the rotational spectra of superdeformed nuclei suggests the occurence of Y44 deformations in the nuclear shape with associated C4 v point-symmetry for the rotational Hamiltonian. We have investigated the general class of Hamiltonians with such symmetry. In addition, we require the axially symmetric terms to favour rotation about an axis that is perpendicular to the long axis of nuclear shape. The δI = 4 staggering can indeed result from the tunneling between the four equivalent minima that occur in the plane perpendicular to the superdeformation symmetry axis, but the occurence of this effect is a subtle matter depending sensitively on the axially symmetric terms in the Hamiltonian.
Jeong, Jae-Woong; Park, Bryan; Keum, Hohyun; Kim, Seok; Rogers, John A; Solgaard, Olav
2013-06-03
We present a two-axis electrostatic MEMS scanner with high-reflectivity monolithic single-crystal-silicon photonic crystal (PC) mirrors suitable for applications in harsh environments. The reflective surfaces of the MEMS scanner are transfer-printed PC mirrors with low polarization dependence, low angular dependence, and reflectivity over 85% in the wavelength range of 1490nm~1505nm and above 90% over the wavelength band of 1550~1570nm. In static mode, the scanner has total scan range of 10.2° on one rotation axis and 7.8° on the other. Dynamic operation on resonance increase the scan range to 21° at 608Hz around the outer rotation axis and 9.5° at 1.73kHz about the inner rotation axis.
Computational analysis of vertical axis wind turbine arrays
Bremseth, J.; Duraisamy, K.
2016-10-01
Canonical problems involving single, pairs, and arrays of vertical axis wind turbines (VAWTs) are investigated numerically with the objective of understanding the underlying flow structures and their implications on energy production. Experimental studies by Dabiri (J Renew Sustain Energy 3, 2011) suggest that VAWTs demand less stringent spacing requirements than their horizontal axis counterparts and additional benefits may be obtained by optimizing the placement and rotational direction of VAWTs. The flowfield of pairs of co-/counter-rotating VAWTs shows some similarities with pairs of cylinders in terms of wake structure and vortex shedding. When multiple VAWTs are placed in a column, the extent of the wake is seen to spread further downstream, irrespective of the direction of rotation of individual turbines. However, the aerodynamic interference between turbines gives rise to regions of excess momentum between the turbines which lead to significant power augmentations. Studies of VAWTs arranged in multiple columns show that the downstream columns can actually be more efficient than the leading column, a proposition that could lead to radical improvements in wind farm productivity.
PRIGo: a new multi-axis goniometer for macromolecular crystallography
Energy Technology Data Exchange (ETDEWEB)
Waltersperger, Sandro; Olieric, Vincent, E-mail: vincent.olieric@psi.ch; Pradervand, Claude [Paul Scherrer Institute, Villigen PSI (Switzerland); Glettig, Wayne [Centre Suisse d’Electronique et Microtechnique SA, Neuchâtel 2002 (Switzerland); Salathe, Marco; Fuchs, Martin R.; Curtin, Adrian; Wang, Xiaoqiang; Ebner, Simon; Panepucci, Ezequiel; Weinert, Tobias [Paul Scherrer Institute, Villigen PSI (Switzerland); Schulze-Briese, Clemens [Dectris Ltd, Baden 5400 (Switzerland); Wang, Meitian, E-mail: vincent.olieric@psi.ch [Paul Scherrer Institute, Villigen PSI (Switzerland)
2015-05-09
The design and performance of the new multi-axis goniometer PRIGo developed at the Swiss Light Source at Paul Scherrer Institute is described. The Parallel Robotics Inspired Goniometer (PRIGo) is a novel compact and high-precision goniometer providing an alternative to (mini-)kappa, traditional three-circle goniometers and Eulerian cradles used for sample reorientation in macromolecular crystallography. Based on a combination of serial and parallel kinematics, PRIGo emulates an arc. It is mounted on an air-bearing stage for rotation around ω and consists of four linear positioners working synchronously to achieve x, y, z translations and χ rotation (0–90°), followed by a ϕ stage (0–360°) for rotation around the sample holder axis. Owing to the use of piezo linear positioners and active correction, PRIGo features spheres of confusion of <1 µm, <7 µm and <10 µm for ω, χ and ϕ, respectively, and is therefore very well suited for micro-crystallography. PRIGo enables optimal strategies for both native and experimental phasing crystallographic data collection. Herein, PRIGo hardware and software, its calibration, as well as applications in macromolecular crystallography are described.
Models of cuspy triaxial stellar systems. IV: Rotating systems
Carpintero, D D
2016-01-01
We built two self-consistent models of triaxial, cuspy, rotating stellar systems adding rotation to non-rotating models presented in previous papers of this series. The final angular velocity of the material is not constant and varies with the distance to the center and with the height over the equator of the systems, but the figure rotation is very uniform in both cases. Even though the addition of rotation to the models modifies their original semiaxes ratios, the final rotating models are considerably flattened and triaxial. An analysis of the orbital content of the models shows that about two thirds of their orbits are chaotic yet the models are very stable over intervals of the order of one Hubble time. The bulk of regular orbits are short axis tubes, while long axis tubes are replaced by tubes whose axes lie on the short-long axes plane, but do not coincide with the major axis. Other types of regular orbits that do not appear in non-rotating systems, like horseshoes and orbits that cross themselves, are...
Numerical simulations of rotating axisymmetric sunspots
Botha, Gert; Busse, F.H.; Hurlburt, Neal; Rucklidge, Alistair
2008-01-01
A numerical model of axisymmetric convection in the presence of a vertical magnetic flux bundle and rotation about the axis is presented. The model contains a compressible plasma described by the non-linear MHD equations, with density and temperature gradients simulating the upper layer of the Sun’s convection zone. The solutions exhibit a central magnetic flux tube in a cylindrical numerical domain, with convection cells forming collar flows around the tube. When the numerical domain is rota...
Face seal assembly for rotating drum
Morgan, J. Giles; Rennich, Mark J.; Whatley, Marvin E.
1982-01-01
A seal assembly comprises a tube rotatable about its longitudinal axis and having two longitudinally spaced flanges projecting radially outwardly from the outer surface thereof. Slidably positioned against one of the flanges is a seal ring, and disposed between this seal ring and the other flange are two rings that are forced apart by springs, one of the latter rings being attached to a flexible wall.
Synchronous states of slowly rotating pendula
Energy Technology Data Exchange (ETDEWEB)
Kapitaniak, Marcin [Division of Dynamics, Technical University of Lodz, Stefanowskiego 1/15, 90-924 Lodz (Poland); Centre for Applied Dynamics Research, School of Engineering, University of Aberdeen, AB24 3UE Aberdeen, Scotland (United Kingdom); Czolczynski, Krzysztof; Perlikowski, Przemysław; Stefanski, Andrzej [Division of Dynamics, Technical University of Lodz, Stefanowskiego 1/15, 90-924 Lodz (Poland); Kapitaniak, Tomasz, E-mail: tomasz.kapitaniak@p.lodz.pl [Division of Dynamics, Technical University of Lodz, Stefanowskiego 1/15, 90-924 Lodz (Poland)
2014-08-01
Coupled systems that contain rotating elements are typical in physical, biological and engineering applications and for years have been the subject of intensive studies. One problem of scientific interest, which among others occurs in such systems is the phenomenon of synchronization of different rotating parts. Despite different initial conditions, after a sufficiently long transient, the rotating parts move in the same way — complete synchronization, or a permanent constant shift is established between their displacements, i.e., the angles of rotation — phase synchronization. Synchronization occurs due to dependence of the periods of rotating elements motion and the displacement of the base on which these elements are mounted. We review the studies on the synchronization of rotating pendula and compare them with the results obtained for oscillating pendula. As an example we consider the dynamics of the system consisting of n pendula mounted on the movable beam. The pendula are excited by the external torques which are inversely proportional to the angular velocities of the pendula. As the result of such excitation each pendulum rotates around its axis of rotation. It has been assumed that all pendula rotate in the same direction or in the opposite directions. We consider the case of slowly rotating pendula and estimate the influence of the gravity on their motion. We classify the synchronous states of the identical pendula and observe how the parameters mismatch can influence them. We give evidence that synchronous states are robust as they exist in the wide range of system parameters and can be observed in a simple experiment.
Instabilities in Coaxial Rotating Jets
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
The aim of this study is the characterization of the cylindrical mixing layer resulting layer resulting from the interaction of two coaxial swirling jets.The experimental part of this study was performed in a cylindrical water tunnel,permitting an independent rotation of two coaxial jets.The rotations are generated by means of 2×36 blades localized in two swirling chambers.As expected,the evolution of the main instabiltiy modes presents certain differences compared to the plane-mixing-layer case ,Experimental results obtained by tomography showed the existence of vortex rings and streamwise vortex paris in the near field region.This method also permitted the observation of the evolution and interaction of different modes.PIV velocity measurements realized in the meridian plans and the plans perpendicular to the jet axis show that rotation distrots the typical top-hat axial velocity profile.The transition of the the axial velocity profile from jet-like into wake-like is also observed.
Neospora caninum is a cause of perinatal mortality in axis deer (Axis axis).
Basso, Walter; Moré, Gastón; Quiroga, Maria Alejandra; Balducchi, Diego; Schares, Gereon; Venturini, Maria Cecilia
2014-01-31
Neospora caninum is a worldwide distributed protozoan that may cause neuromuscular disease in dogs and reproductive failure in domestic and wild ruminants. One axis fawn (Axis axis) and four neonates from the same deer herd died at a zoo in Argentina within a four-month period. The fawn presented with dilatation of the anal sphincter at birth and incontinence, developed weakness and ataxia and died at 14 days of age. At necropsy, a mega formation of the distal large intestine was observed. Microscopically, non-suppurative encephalitis, suppurative bronchopneumonia, fibrin necrotic enteritis and degenerative changes in the liver were observed in hematoxilin and eosin-stained tissue sections, and thick-walled N. caninum-like cysts were observed in fresh brain samples. Serologic studies for N. caninum revealed an IFAT titer of 1:6400 in the fawn and 1:25, 1:400, 1:3200 and 1:6400 in the neonates. N. caninum DNA was detected in brain samples from the fawn and from one neonate by PCR, and the parasite was isolated in vitro from the fawn' brain after passage through gerbils (Meriones unguiculatus) and gamma-interferon knock-out mice. N. caninum DNA obtained from the fawn, neonate and isolated parasites showed the same microsatellite pattern. This suggests a common infection source for both animals. The diagnosis of N. caninum infection was confirmed, suggesting its association with perinatal mortality in captive axis deer. To the best of our knowledge, this is the first report of clinical disease associated to N. caninum infection in axis deer and of isolation of the parasite from this wild ruminant species.
Downwind rotor horizontal axis wind turbine noise prediction
Metzger, F. B.; Klatte, R. J.
1981-01-01
NASA and industry are currently cooperating in the conduct of extensive experimental and analytical studies to understand and predict the noise of large, horizontal axis wind turbines. This effort consists of (1) obtaining high quality noise data under well controlled and documented test conditions, (2) establishing the annoyance criteria for impulse noise of the type generated by horizontal axis wind turbines with rotors downwind of the support tower, (3) defining the wake characteristics downwind of the axial location of the plane of rotation, (4) comparing predictions with measurements made by use of wake data, and (5) comparing predictions with annoyance criteria. The status of work by Hamilton Standard in the above areas which was done in support of the cooperative NASA and industry studies is briefly summarized.
Angle estimation of simultaneous orthogonal rotations from 3D gyroscope measurements.
Stančin, Sara; Tomažič, Sašo
2011-01-01
A 3D gyroscope provides measurements of angular velocities around its three intrinsic orthogonal axes, enabling angular orientation estimation. Because the measured angular velocities represent simultaneous rotations, it is not appropriate to consider them sequentially. Rotations in general are not commutative, and each possible rotation sequence has a different resulting angular orientation. None of these angular orientations is the correct simultaneous rotation result. However, every angular orientation can be represented by a single rotation. This paper presents an analytic derivation of the axis and angle of the single rotation equivalent to three simultaneous rotations around orthogonal axes when the measured angular velocities or their proportions are approximately constant. Based on the resulting expressions, a vector called the simultaneous orthogonal rotations angle (SORA) is defined, with components equal to the angles of three simultaneous rotations around coordinate system axes. The orientation and magnitude of this vector are equal to the equivalent single rotation axis and angle, respectively. As long as the orientation of the actual rotation axis is constant, given the SORA, the angular orientation of a rigid body can be calculated in a single step, thus making it possible to avoid computing the iterative infinitesimal rotation approximation. The performed test measurements confirm the validity of the SORA concept. SORA is simple and well-suited for use in the real-time calculation of angular orientation based on angular velocity measurements derived using a gyroscope. Moreover, because of its demonstrated simplicity, SORA can also be used in general angular orientation notation.
Angle Estimation of Simultaneous Orthogonal Rotations from 3D Gyroscope Measurements
Directory of Open Access Journals (Sweden)
Sara Stančin
2011-09-01
Full Text Available A 3D gyroscope provides measurements of angular velocities around its three intrinsic orthogonal axes, enabling angular orientation estimation. Because the measured angular velocities represent simultaneous rotations, it is not appropriate to consider them sequentially. Rotations in general are not commutative, and each possible rotation sequence has a different resulting angular orientation. None of these angular orientations is the correct simultaneous rotation result. However, every angular orientation can be represented by a single rotation. This paper presents an analytic derivation of the axis and angle of the single rotation equivalent to three simultaneous rotations around orthogonal axes when the measured angular velocities or their proportions are approximately constant. Based on the resulting expressions, a vector called the simultaneous orthogonal rotations angle (SORA is defined, with components equal to the angles of three simultaneous rotations around coordinate system axes. The orientation and magnitude of this vector are equal to the equivalent single rotation axis and angle, respectively. As long as the orientation of the actual rotation axis is constant, given the SORA, the angular orientation of a rigid body can be calculated in a single step, thus making it possible to avoid computing the iterative infinitesimal rotation approximation. The performed test measurements confirm the validity of the SORA concept. SORA is simple and well-suited for use in the real-time calculation of angular orientation based on angular velocity measurements derived using a gyroscope. Moreover, because of its demonstrated simplicity, SORA can also be used in general angular orientation notation.
Boundary Layer Transition Detection on a Rotor Blade Using Rotating Mirror Thermography
Heineck, James T.; Schuelein, Erich; Raffel, Markus
2014-01-01
Laminar-to-turbulent transition on a rotor blade in hover has been imaged using an area-scan infrared camera. A new method for tracking a blade using a rotating mirror was employed. The mirror axis of rotation roughly corresponded to the rotor axis of rotation and the mirror rotational frequency is 1/2 that of the rotor. This permitted the use of cameras whose integration time was too long to prevent image blur due to the motion of the blade. This article will show the use of this method for a rotor blade at different collective pitch angles.
CFD-RANS analysis of the rotational effects on the boundary layer of wind turbine blades
DEFF Research Database (Denmark)
Carcangiu, Carlo Enrico; Sørensen, Jens Nørkær; Cambuli, Francesco
2007-01-01
The flow field past the rotating blade of a horizontal axis wind turbine has been modeled with a full 3-D steady-RANS approach. Flow computations have been performed using the commercial finite-volume solver Fluent. A number of blade sections from the 3-D rotating geometry were chosen and the cor......The flow field past the rotating blade of a horizontal axis wind turbine has been modeled with a full 3-D steady-RANS approach. Flow computations have been performed using the commercial finite-volume solver Fluent. A number of blade sections from the 3-D rotating geometry were chosen...
Effective solidity in vertical axis wind turbines
Parker, Colin M.; Leftwich, Megan C.
2016-11-01
The flow surrounding vertical axis wind turbines (VAWTs) is investigated using particle imaging velocimetry (PIV). This is done in a low-speed wind tunnel with a scale model that closely matches geometric and dynamic properties tip-speed ratio and Reynolds number of a full size turbine. Previous results have shown a strong dependance on the tip-speed ratio on the wake structure of the spinning turbine. However, it is not clear whether this is a speed or solidity effect. To determine this, we have measured the wakes of three turbines with different chord-to-diameter ratios, and a solid cylinder. The flow is visualized at the horizontal mid-plane as well as the vertical mid-plane behind the turbine. The results are both ensemble averaged and phase averaged by syncing the PIV system with the rotation of the turbine. By keeping the Reynolds number constant with both chord and diameter, we can determine how each effects the wake structure. As these parameters are varied there are distinct changes in the mean flow of the wake. Additionally, by looking at the vorticity in the phase averaged profiles we can see structural changes to the overall wake pattern.
Land, K; Land, Kate; Magueijo, Joao
2006-01-01
In light of the three-year data release from WMAP we re-examine the evidence for the ``Axis of Evil''. We discover that previous frequentist methods are not robust with respect to the data-sets available and different treatments of the galactic plane. We identify the cause of the instability and show that this result is not a weakness of the data. This is further confirmed by exhibiting an alternative approach, Bayesian in flavour, and based on a likelihood method and the information criteria. We find strong (and sometimes decisive) evidence for the ``Axis of Evil'' in almost all renditions of the WMAP data. However some significant differences between data-sets remain, and the quantitative aspects of the result depend on the particular information criteria used.
Effective diffusivity of passive scalars in rotating flow
Imazio, P Rodriguez
2012-01-01
We use direct numerical simulations to compute turbulent transport coefficients for passive scalars in turbulent rotating flows. Effective diffusion coefficients in the directions parallel and perpendicular to the rotations axis are obtained by studying the diffusion of an imposed initial profile for the passive scalar, and calculated by measuring the scalar average concentration and average spatial flux as a function of time. The Rossby and Schmidt numbers are varied to quantify their effect on the effective diffusion. It is find that rotation reduces scalar diffusivity in the perpendicular direction. The perpendicular diffusion can be estimated from mixing length arguments using the characteristic velocities and lengths perpendicular to the rotation axis. Deviations are observed for small Schmidt numbers, for which turbulent transport decreases and molecular diffusion becomes more significant.
Centripetal focusing of gyrotactic phytoplankton in solid-body rotation
Cencini, M; Santamaria, F; Boffetta, G
2015-01-01
A suspension of gyrotactic microalgae Chlamydomonas augustae swimming in a cylindrical water vessel in solid-body rotation is studied. Our experiments show that swimming algae form an aggregate around the axis of rotation, whose intensity increases with the rotation speed. We explain this phenomenon by the centripetal orientation of the swimming direction towards the axis of rotation. This centripetal focusing is contrasted by diffusive fluxes due to stochastic reorientation of the cells. The competition of the two effects lead to a stationary distribution, which we analytically derive from a refined mathematical model of gyrotactic swimmers. The temporal evolution of the cell distribution, obtained via numerical simulations of the stochastic model, is in quantitative agreement with the experimental measurements in the range of parameters explored.
Three-axis atomic magnetometer based on spin precession modulation
Energy Technology Data Exchange (ETDEWEB)
Huang, H. C.; Dong, H. F., E-mail: hfdong@buaa.edu.cn; Hu, X. Y.; Chen, L.; Gao, Y. [School of Instrumentation Science and Opto-Electronics Engineering, Beihang University, Beijing 100191 (China)
2015-11-02
We demonstrate a three-axis atomic magnetometer with one intensity-modulated pump beam and one orthogonal probe beam. The main field component is measured using the resonance of the pumping light, while the transverse field components are measured simultaneously using the optical rotation of the probe beam modulated by the spin precession. It is an all-optical magnetometer without using any modulation field or radio frequency field. Magnetic field sensitivity of 0.8 pT/Hz{sup 1∕2} is achieved under a bias field of 2 μT.
Localized waves supported by the rotating waveguide array
Zhang, Xiao; Ye, Fangwei; Kartashov, Yaroslav V.; Vysloukh, Victor A.; Chen, Xianfeng
2016-09-01
We show that truncated rotating square waveguide arrays support new types of localized modes that exist even in the linear case, in complete contrast to localized excitations in nonrotating arrays requiring nonlinearity for their existence and forming above the energy flow threshold. These new modes appear either around array center, since rotation leads to the emergence of the effective attractive potential with a minimum at the rotation axis, or in the array corners, in which case localization occurs due to competition between centrifugal force (in terms of quasi-particle analogy) and total internal reflection at the interface of the truncated array. The degree of localization of the central and corner modes mediated by rotation increases with rotation frequency. Stable rotating soliton families bifurcating from linear modes are analyzed in both focusing and defocusing media.
Localized waves supported by the rotating waveguide array
Zhang, Xiao; Kartashov, Yaroslav V; Vysloukh, Victor A; Chen, Xianfeng
2016-01-01
We show that truncated rotating square waveguide arrays support new types of localized modes that exist even in the linear case, in complete contrast to localized excitations in nonrotating arrays requiring nonlinearity for their existence and forming above the energy flow threshold. These new modes appear either around array center, since rotation leads to the emergence of the effective attractive potential with a minimum at the rotation axis, or in the array corners, in which case localization occurs due to competition between centrifugal force (in terms of quasi-particle analogy) and total internal reflection at the interface of the truncated array. The degree of localization of the central and corner modes mediated by rotation increases with rotation frequency. Stable rotating soliton families bifurcating from linear modes are analyzed in both focusing and defocusing media.
Faraday resonance in dynamical bar instability of differentially rotating stars
Saijo, Motoyuki
2008-01-01
We investigate the nonlinear behaviour of the dynamically unstable rotating star for the bar mode by three-dimensional hydrodynamics in Newtonian gravity. We find that an oscillation along the rotation axis is induced throughout the growth of the unstable bar mode, and that its characteristic frequency is twice as that of the bar mode, which oscillates mainly along the equatorial plane. A possibility to observe Faraday resonance in gravitational waves is demonstrated and discussed.
Magnetic rotation and chiral symmetry breaking
Indian Academy of Sciences (India)
Ashok Kumar Jain; Amita
2001-08-01
The deformed mean ﬁeld of nuclei exhibits various geometrical and dynamical symmetries which manifest themselves as various types of rotational and decay patterns. Most of the symmetry operations considered so far have been deﬁned for a situation wherein the angular momentum coincides with one of the principal axes and the principal axis cranking may be invoked. New possibilities arise with the observation of rotational features in weakly deformed nuclei and now interpreted as magnetic rotational bands. More than 120 MR bands have now been identiﬁed by ﬁltering the existing data. We present a brief overview of these bands. The total angular momentum vector in such bands is tilted away from the principal axes. Such a situation gives rise to several new possibilities including breaking of chiral symmetry as discussed recently by Frauendorf. We present the outcome of such symmetries and their possible experimental veriﬁcation. Some possible examples of chiral bands are presented.
Rotational Doppler effect in nonlinear optics
Li, Guixin; Zentgraf, Thomas; Zhang, Shuang
2016-08-01
The translational Doppler effect of electromagnetic and sound waves has been successfully applied in measurements of the speed and direction of vehicles, astronomical objects and blood flow in human bodies, and for the Global Positioning System. The Doppler effect plays a key role for some important quantum phenomena such as the broadened emission spectra of atoms and has benefited cooling and trapping of atoms with laser light. Despite numerous successful applications of the translational Doppler effect, it fails to measure the rotation frequency of a spinning object when the probing wave propagates along its rotation axis. This constraint was circumvented by deploying the angular momentum of electromagnetic waves--the so-called rotational Doppler effect. Here, we report on the demonstration of rotational Doppler shift in nonlinear optics. The Doppler frequency shift is determined for the second harmonic generation of a circularly polarized beam passing through a spinning nonlinear optical crystal with three-fold rotational symmetry. We find that the second harmonic generation signal with circular polarization opposite to that of the fundamental beam experiences a Doppler shift of three times the rotation frequency of the optical crystal. This demonstration is of fundamental significance in nonlinear optics, as it provides us with insight into the interaction of light with moving media in the nonlinear optical regime.
Carlson, Bruce M.
1972-01-01
Rotation of a skin cuff 180° around the proximodistal axis of the upper arm in the axolotl results in the formation of multiple regenerates in about 80° of cases after amputation of the limb through the rotated skin. Rotation of the dermis or the flexor and extensor muscles folowed by amputation pro
On the Structure Orientation in Rotating and Sheared Homogeneous Turbulence
Aguirre, Joylene C.; Moreau, Adam F.; Jacobitz, Frank G.
2016-11-01
The results of direct numerical simulations are used to study the effect of rotation on the orientation of structures and the evolution of the turbulent kinetic energy in homogeneous sheared turbulence. Shear flows without rotation, with moderate rotation, and with strong rotation are considered and the rotation axis is either parallel or anti-parallel to the mean flow vorticity. In the case of moderate rotation, an anti-parallel configuration increases the growth rate of the turbulent kinetic energy, while a parallel configuration decreases the growth rate as compared to the flow without rotation. The orientation of turbulent structures present in the flows are characterized using the three-dimensional, two-point autocorrelation coefficient of velocity magnitude and vorticity magnitude. An ellipsoid is fitted to the surface defined by a constant autocorrelation coefficient value and the major and minor axes are used to determine the inclination angle of flow structures in the plane of shear. It was found that the inclination angle assumes a maximum value for the anti-parallel configuration with moderate rotation. Again, the inclination angle for the parallel configuration with moderate rotation is reduced as compared to the case without rotation. The smallest inclination angles are found for the strongly rotating cases. Hence, the inclination angle is directly related to the growth rate of the turbulent kinetic energy. University of San Diego Shiley-Marcos School of Engineering and McNair Scholars.
Galvano-rotational effect induced by electroweak interactions in pulsars
Energy Technology Data Exchange (ETDEWEB)
Dvornikov, Maxim [Institute of Physics, University of São Paulo, CP 66318, CEP 05314-970 São Paulo, SP (Brazil); Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation (IZMIRAN), 142190 Troitsk, Moscow (Russian Federation); Physics Faculty, National Research Tomsk State University, 36 Lenin Ave., 634050 Tomsk (Russian Federation)
2015-05-21
We study electroweakly interacting particles in rotating matter. The existence of the electric current along the axis of the matter rotation is predicted in this system. This new galvano-rotational effect is caused by the parity violating interaction between massless charged particles in the rotating matter. We start with the exact solution of the Dirac equation for a fermion involved in the electroweak interaction in the rotating frame. This equation includes the noninertial effects. Then, using the obtained solution, we derive the induced electric current which turns out to flow along the rotation axis. We study the possibility of the appearance of the galvano-rotational effect in dense matter of compact astrophysical objects. The particular example of neutron and hypothetical quark stars is discussed. It is shown that, using this effect, one can expect the generation of toroidal magnetic fields comparable with poloidal ones in old millisecond pulsars. We also briefly discuss the generation of the magnetic helicity in these stars. Finally we analyze the possibility to apply the galvano-rotational effect for the description of the asymmetric neutrino emission from a neutron star to explain pulsars kicks.
Rotating Shaft Tilt Angle Measurement Using an Inclinometer
Directory of Open Access Journals (Sweden)
Luo Jun
2015-10-01
Full Text Available This paper describes a novel measurement method to accurately measure the rotating shaft tilt angle of rotating machine for alignment or compensation using a dual-axis inclinometer. A model of the rotating shaft tilt angle measurement is established using a dual-axis inclinometer based on the designed mechanical structure, and the calculation equation between the rotating shaft tilt angle and the inclinometer axes outputs is derived under the condition that the inclinometer axes are perpendicular to the rotating shaft. The reversal measurement method is applied to decrease the effect of inclinometer drifts caused by temperature, to eliminate inclinometer and rotating shaft mechanical error and inclinometer systematic error to attain high measurement accuracy. The uncertainty estimation shows that the accuracy of rotating shaft tilt angle measurement depends mainly on the inclinometer uncertainty and its uncertainty is almost the same as the inclinometer uncertainty in the simulation. The experimental results indicate that measurement time is 4 seconds; the range of rotating shaft tilt angle is 0.002° and its standard deviation is 0.0006° using NS-5/P2 inclinometer, whose precision and resolution are ±0.01° and 0.0005°, respectively.
Rotating Shaft Tilt Angle Measurement Using an Inclinometer
Luo, Jun; Wang, Zhiqian; Shen, Chengwu; Wen, Zhuoman; Liu, Shaojin; Cai, Sheng; Li, Jianrong
2015-10-01
This paper describes a novel measurement method to accurately measure the rotating shaft tilt angle of rotating machine for alignment or compensation using a dual-axis inclinometer. A model of the rotating shaft tilt angle measurement is established using a dual-axis inclinometer based on the designed mechanical structure, and the calculation equation between the rotating shaft tilt angle and the inclinometer axes outputs is derived under the condition that the inclinometer axes are perpendicular to the rotating shaft. The reversal measurement method is applied to decrease the effect of inclinometer drifts caused by temperature, to eliminate inclinometer and rotating shaft mechanical error and inclinometer systematic error to attain high measurement accuracy. The uncertainty estimation shows that the accuracy of rotating shaft tilt angle measurement depends mainly on the inclinometer uncertainty and its uncertainty is almost the same as the inclinometer uncertainty in the simulation. The experimental results indicate that measurement time is 4 seconds; the range of rotating shaft tilt angle is 0.002° and its standard deviation is 0.0006° using NS-5/P2 inclinometer, whose precision and resolution are ±0.01° and 0.0005°, respectively.
Design of h-Darrieus vertical axis wind turbine
Parra, Teresa; Vega, Carmen; Gallegos, A.; Uzarraga, N. C.; Castro, F.
2015-05-01
Numerical simulation is used to predict the performance of a Vertical Axis Wind Turbine (VAWT) H-Darrieus. The rotor consists of three straight blades with shape of aerofoil of the NACA family attached to a rotating vertical shaft. The influence of the solidity is tested to get design tendencies. The mesh has two fluid volumes: one sliding mesh for the rotor where the rotation velocity is established while the other is the environment of the rotor. Bearing in mind the overall flow is characterized by important secondary flows, the turbulence model selected was realizable k-epsilon with non-equilibrium wall functions. Conservation equations were solved with a Third-Order Muscl scheme using SIMPLE to couple pressure and velocity. During VAWT operation, the performance depends mainly on the relative motion of the rotating blade and has a fundamental period which depends both on the rate of rotation and the number of blades. The transient study is necessary to characterise the hysteresis phenomenon. Hence, more than six revolutions get the periodic behaviour. Instantaneous flows provide insight about wake structure interaction. Time averaged parameters let obtain the characteristic curves of power coefficient.
Design of h-Darrieus vertical axis wind turbine
Directory of Open Access Journals (Sweden)
Parra Teresa
2015-01-01
Full Text Available Numerical simulation is used to predict the performance of a Vertical Axis Wind Turbine (VAWT H-Darrieus. The rotor consists of three straight blades with shape of aerofoil of the NACA family attached to a rotating vertical shaft. The influence of the solidity is tested to get design tendencies. The mesh has two fluid volumes: one sliding mesh for the rotor where the rotation velocity is established while the other is the environment of the rotor. Bearing in mind the overall flow is characterized by important secondary flows, the turbulence model selected was realizable k-epsilon with non-equilibrium wall functions. Conservation equations were solved with a Third-Order Muscl scheme using SIMPLE to couple pressure and velocity. During VAWT operation, the performance depends mainly on the relative motion of the rotating blade and has a fundamental period which depends both on the rate of rotation and the number of blades. The transient study is necessary to characterise the hysteresis phenomenon. Hence, more than six revolutions get the periodic behaviour. Instantaneous flows provide insight about wake structure interaction. Time averaged parameters let obtain the characteristic curves of power coefficient.
Velocity measurement of model vertical axis wind turbines
Energy Technology Data Exchange (ETDEWEB)
Johnson, D.A.; McWilliam, M. [Waterloo Univ., ON (Canada). Dept. of Mechanical Engineering
2006-07-01
An increasingly popular solution to future energy demand is wind energy. Wind turbine designs can be grouped according to their axis of rotation, either horizontal or vertical. Horizontal axis wind turbines have higher power output in a good wind regime than vertical axis turbines and are used in most commercial class designs. Vertical axis Savonius-based wind turbine designs are still widely used in some applications because of their simplistic design and low wind speed performance. There are many design variables that must be considered in order to optimize the power output in a given wind regime in a typical wind turbine design. Using particle image velocimetry, a study of the air flow around five different model vertical axis wind turbines was conducted in a closed loop wind tunnel. A standard Savonius design with two semi-circular blades overlapping, and two variations of this design, a deep blade and a shallow blade design were among the turbine models included in this study. It also evaluated alternate designs that attempt to increase the performance of the standard design by allowing compound blade curvature. Measurements were collected at a constant phase angle and also at random rotor orientations. It was found that evaluation of the flow patterns and measured velocities revealed consistent and stable flow patterns at any given phase angle. Large scale flow structures are evident in all designs such as vortices shed from blade surfaces. An important performance parameter was considered to be the ability of the flow to remain attached to the forward blade and redirect and reorient the flow to the following blade. 6 refs., 18 figs.
Eye Formation in Rotating Convection
Oruba, L; Dormy, E
2016-01-01
We consider rotating convection in a shallow, cylindrical domain. We examine the conditions under which the resulting vortex develops an eye at its core; that is, a region where the poloidal flow reverses and the angular momentum is low. For simplicity, we restrict ourselves to steady, axisymmetric flows in a Boussinesq fluid. Our numerical experiments show that, in such systems, an eye forms as a passive response to the development of a so-called eyewall, a conical annulus of intense, negative azimuthal vorticity that can form near the axis and separates the eye from the primary vortex. We also observe that the vorticity in the eyewall comes from the lower boundary layer, and relies on the fact the poloidal flow strips negative vorticity out of the boundary layer and carries it up into the fluid above as it turns upward near the axis. This process is effective only if the Reynolds number is sufficiently high for the advection of vorticity to dominate over diffusion. Finally we observe that, in the vicinity o...
Eye formation in rotating convection
Oruba, L.; Davidson, P. A.; Dormy, E.
2017-02-01
We consider rotating convection in a shallow, cylindrical domain. We examine the conditions under which the resulting vortex develops an eye at its core; that is, a region where the poloidal flow reverses and the angular momentum is low. For simplicity, we restrict ourselves to steady, axisymmetric flows in a Boussinesq fluid. Our numerical experiments show that, in such systems, an eye forms as a passive response to the development of a so-called eyewall, a conical annulus of intense, negative azimuthal vorticity that can form near the axis and separates the eye from the primary vortex. We also observe that the vorticity in the eyewall comes from the lower boundary layer, and relies on the fact the poloidal flow strips negative vorticity out of the boundary layer and carries it up into the fluid above as it turns upward near the axis. This process is effective only if the Reynolds number is sufficiently high for the advection of vorticity to dominate over diffusion. Finally we observe that, in the vicinity of the eye and the eyewall, the buoyancy and Coriolis forces are negligible, and so although these forces are crucial to driving and shaping the primary vortex, they play no direct role in eye formation in a Boussinesq fluid.
Numerical studies of Siberian snakes and spin rotators for RHIC
Energy Technology Data Exchange (ETDEWEB)
Luccio, A.
1995-04-17
For the program of polarized protons in RHIC, two Siberian snakes and four spin rotators per ring will be used. The Snakes will produce a complete spin flip. Spin Rotators, in pairs, will rotate the spin from the vertical direction to the horizontal plane at a given insertion, and back to the vertical after the insertion. Snakes, 180{degrees} apart and with their axis of spin precession at 90{degrees} to each other, are an effective means to avoid depolarization of the proton beam in traversing resonances. Classical snakes and rotators are made with magnetic solenoids or with a sequence of magnetic dipoles with fields alternately directed in the radial and vertical direction. Another possibility is to use helical magnets, essentially twisted dipoles, in which the field, transverse the axis of the magnet, continuously rotates as the particles proceed along it. After some comparative studies, the authors decided to adopt for RHIC an elegant solution with four helical magnets both for the snakes and the rotators proposed by Shatunov and Ptitsin. In order to simplify the construction of the magnets and to minimize cost, four identical super conducting helical modules will be used for each device. Snakes will be built with four right-handed helices. Spin rotators with two right-handed and two left-handed helices. The maximum field will be limited to 4 Tesla. While small bore helical undulators have been built for free electron lasers, large super conducting helical magnets have not been built yet. In spite of this difficulty, this choice is dictated by some distinctive advantages of helical over more conventional transverse snakes/rotators: (i) the devices are modular, they can be built with arrangements of identical modules, (ii) the maximum orbit excursion in the magnet is smaller, (iii) orbit excursion is independent from the separation between adjacent magnets, (iv) they allow an easier control of the spin rotation and the orientation of the spin precession axis.
Rotator cuff repair - slideshow
... this page: //medlineplus.gov/ency/presentations/100229.htm Rotator cuff repair - series—Normal anatomy To use the sharing ... to slide 4 out of 4 Overview The rotator cuff is a group of muscles and tendons that ...
DEFF Research Database (Denmark)
Gramkow, Claus
1999-01-01
In this article two common approaches to averaging rotations are compared to a more advanced approach based on a Riemannian metric. Very offten the barycenter of the quaternions or matrices that represent the rotations are used as an estimate of the mean. These methods neglect that rotations belong...... approximations to the Riemannian metric, and that the subsequent corrections are inherient in the least squares estimation. Keywords: averaging rotations, Riemannian metric, matrix, quaternion...
Model of a rotating magnetic cloud
Farrugia, C. J.; Osherovich, V. A.; Burlaga, L. F.
1992-01-01
The possibility that magnetic clouds rotate while they propagate antisunward was investigated. Magnetic clouds are modeled as magnetic flux ropes which rotate rigidly about the axis of symmetry. An ideal magnetohydrodynamic model, in which the evolution of the magnetic structure is related to the time evolution of the angular frequency, is developed. A class of 'separable' magnetic fields is employed to reduce the problem to a nonlinear ordinary differential equation for the evolution function, and it is solved numerically. The corresponding effective potential gives rise to two modes of evolution--expansion and oscillation--depending on the energy and on the value of a dimensionless parameter, k. Parameter k depends on the gas pressure, the ratio of the magnetic field components, and the frequency of rotation. There is a critical value of k, k(sub c), above which the oscillatory regime disappears and the flux rope invariably expands, regardless of the energy. Below k(sub c) the energy determines whether the configuration is confined or unbounded. Rotation always helps expansion by lowering the potential barrier. A data example was studied and features which are interpreted as signatures of rotation are presented. The angular speed is comparable to the Alfven speed, and the core of the rotating cloud completes on average one full revolution every three days at 1 AU. The parameter k is calculated from observations, and it is found to be close to, but below, critical. Only three out of the nine clouds examined showed signatures of rotation. Theoretical analysis suggests that close to the Sun rotation effects may play a more important role in the evolution of magnetic clouds than 1 AU.
Application of Circulation Controlled Blades for Vertical Axis Wind Turbines
Directory of Open Access Journals (Sweden)
Velissarios Kourkoulis
2013-07-01
Full Text Available The blades of a vertical axis wind turbine (VAWT rotor see an inconsistent angle of attack through its rotation. Consequently, VAWT blades generally use symmetrical aerofoils with a lower lift-to-drag ratio than cambered aerofoils tailored to maximise horizontal axis wind turbine rotor performance. This paper considers the feasibility of circulation controlled (CC VAWT blades, using a tangential air jet to provide lift and therefore power augmentation. However CC blade sections require a higher trailing-edge thickness than conventional sections giving rise to additional base drag. The choice of design parameters is a compromise between lift augmentation, additional base drag as well as the power required to pump the air jet. Although CC technology has been investigated for many years, particularly for aerospace applications, few researchers have considered VAWT applications. This paper considers the feasibility of the technology, using Computational Fluid Dynamics to evaluate a baseline CC aerofoil with different trailing-edge ellipse shapes. Lift and drag increments due to CC are considered within a momentum based turbine model to determine net power production. The study found that for modest momentum coefficients significant net power augmentation can be achieved with a relatively simple aerofoil geometry if blowing is controlled through the blades rotation.
CFD Simulation of Twin Vertical Axis Tidal Turbines System
Directory of Open Access Journals (Sweden)
Syed Shah Khalid
2013-01-01
Full Text Available As concerns about rising fossil-fuel prices, energy security and climate-change increase, renewable energy can play a vital role in producing local, clean and inexhaustible energy to supply world rising demand for electricity. In this study, hydrodynamic analysis of vertical axis tidal turbine operating side-by-side is numerically analyzed. Two-dimensional numerical modeling of the unsteady flow through the blades of the turbine is performed using ANSYS CFX, hereafter CFX; this is based on a Reynolds-Averaged Navier-Stokes (RANS model. The purpose is to find an optimal distance between the turbines where interaction effect is minimal and constructive, where the turbines operate more efficiently than stand alone turbine. A transient simulation is done on Vertical Axis Tidal Turbine (VATT using the Shear Stress Transport Turbulence (SST model. Main hydrodynamic parameters like torque T, coefficients of performance CP and coefficient of torque CT are investigated. The gap spacing between the turbines has an important role in performance improvement and also in vortex shedding suppression for the flows around two counters rotating systems. The simulation results are validated with Ye and Calisal data. The results of this study prove that the total power output of a twin-turbine system with an optimal layout can be about 24% higher than two times that of a stand-alone turbine. We conclude that the optimally configured counter-rotating twin turbines should be a side-by-side arrangement.
Measurement of the screw-home motion of the knee is sensitive to errors in axis alignment.
Piazza, S J; Cavanagh, P R
2000-08-01
Measurements of joint angles during motion analysis are subject to error caused by kinematic crosstalk, that is, one joint rotation (e. g., flexion) being interpreted as another (e.g., abduction). Kinematic crosstalk results from the chosen joint coordinate system being misaligned with the axes about which rotations are assumed to occur. The aim of this paper is to demonstrate that measurement of the so-called "screw-home" motion of the human knee, in which axial rotation and extension are coupled, is especially prone to errors due to crosstalk. The motions of two different two-segment mechanical linkages were examined to study the effects of crosstalk. The segments of the first linkage (NSH) were connected by a revolute joint, but the second linkage (SH) incorporated gearing that caused 15 degrees of screw-home rotation to occur with 90 degrees knee flexion. It was found that rotating the flexion axis (inducing crosstalk) could make linkage NSH appear to exhibit a screw-home motion and that a different rotation of the flexion axis could make linkage SH apparently exhibit pure flexion. These findings suggest that the measurement of screw-home rotation may be strongly influenced by errors in the location of the flexion axis. The magnitudes of these displacements of the flexion axis were consistent with the inter-observer variability seen when five experienced observers defined the flexion axis by palpating the medial and lateral femoral epicondyles. Care should be taken when interpreting small internal-external rotations and abduction-adduction angles to ensure that they are not the products of kinematic crosstalk.
Rotations with Rodrigues' Vector
Pina, E.
2011-01-01
The rotational dynamics was studied from the point of view of Rodrigues' vector. This vector is defined here by its connection with other forms of parametrization of the rotation matrix. The rotation matrix was expressed in terms of this vector. The angular velocity was computed using the components of Rodrigues' vector as coordinates. It appears…
DEFF Research Database (Denmark)
Gramkow, Claus
2001-01-01
In this paper two common approaches to averaging rotations are compared to a more advanced approach based on a Riemannian metric. Very often the barycenter of the quaternions or matrices that represent the rotations are used as an estimate of the mean. These methods neglect that rotations belong...
Rapid fabrication of miniature lens arrays by four-axis single point diamond machining.
McCall, Brian; Tkaczyk, Tomasz S
2013-02-11
A novel method for fabricating lens arrays and other non-rotationally symmetric free-form optics is presented. This is a diamond machining technique using 4 controlled axes of motion - X, Y, Z, and C. As in 3-axis diamond micro-milling, a diamond ball endmill is mounted to the work spindle of a 4-axis ultra-precision computer numerical control (CNC) machine. Unlike 3-axis micro-milling, the C-axis is used to hold the cutting edge of the tool in contact with the lens surface for the entire cut. This allows the feed rates to be doubled compared to the current state of the art of micro-milling while producing an optically smooth surface with very low surface form error and exceptionally low radius error.
Blade pitch optimization methods for vertical-axis wind turbines
Kozak, Peter
Vertical-axis wind turbines (VAWTs) offer an inherently simpler design than horizontal-axis machines, while their lower blade speed mitigates safety and noise concerns, potentially allowing for installation closer to populated and ecologically sensitive areas. While VAWTs do offer significant operational advantages, development has been hampered by the difficulty of modeling the aerodynamics involved, further complicated by their rotating geometry. This thesis presents results from a simulation of a baseline VAWT computed using Star-CCM+, a commercial finite-volume (FVM) code. VAWT aerodynamics are shown to be dominated at low tip-speed ratios by dynamic stall phenomena and at high tip-speed ratios by wake-blade interactions. Several optimization techniques have been developed for the adjustment of blade pitch based on finite-volume simulations and streamtube models. The effectiveness of the optimization procedure is evaluated and the basic architecture for a feedback control system is proposed. Implementation of variable blade pitch is shown to increase a baseline turbine's power output between 40%-100%, depending on the optimization technique, improving the turbine's competitiveness when compared with a commercially-available horizontal-axis turbine.
Calculating pure rotational transitions of water molecule with a simple Lanczos method
Indian Academy of Sciences (India)
Pranab Sarkar
2001-04-01
We have calculated pure rotational transitions of water molecule from a kinetic energy operator (KEO) with the -axis perpendicular to the molecular plane. We have used rotational basis functions which are linear combinations of symmetric top functions so that all matrix elements are real. The calculated spectra agree well with the observed values.
Yan, Yin-Nan; Kubo, Kazuya; Noro, Shin-ichiro; Akutagawa, Tomoyuki; Nakamura, Takayoshi
2014-01-01
Supramolecular cation salt of adamantane rotator with a dithiolene complex, (fluoroadamantylammonium(+))([18]-crown-6)[Ni(dmit)(2)](-) (1) was synthesized. The fluorine atom of the adamantane unit showed a large thermal factor elongated latitudinally, suggesting molecular rotation in the solid state. Crystal 1 exhibited a large dielectric response by applying an AC field along the a axis.
Luk, K C; Chen, P S
1991-03-01
This article introduces a new blockout device for rotational path removable partial dentures. The concept of rotation axis is discussed, from which a more convenient tool for clinical use is derived. The blockout instrument can be divided into three parts: the acrylic block, the rotation axis and the functional part. In the case of tilted mandibular molars, distal and lingual surfaces of anterior abutments should be blocked out according to the rotational path of insertion. In the blockout procedures, the blockout instrument is mounted between the two rotation centers on the two distal abutments with dental stone, so as to coincide the rotation axis of the instrument and that of the denture to be constructed. After the areas below the survey line of the anterior abutments are aproned with wax, Duralay resin is applied onto the areas above the survey line, and extended to join the functional parts of the blockout instrument. After setting, Duralay resin is removed and the portion above the survey line is trimmed to form a knife edge which corresponds to the survey line. Thereafter, the blockout areas are determined by the rotation movement of the knife-edge shaped Duralay resin along the rotation axis of the blockout instrument. This blockout method is more easily performed compared to the method mentioned by Firtell and Jacobson. In addition to the function of blockout, it can also be assisted in analyzing undercut and diagnosis.
Stochl, Jan; Croudace, Tim
2013-01-01
Why some humans prefer to rotate clockwise rather than anticlockwise is not well understood. This study aims to identify the predictors of the preferred rotation direction in humans. The variables hypothesised to influence rotation preference include handedness, footedness, sex, brain hemisphere lateralisation, and the Coriolis effect (which results from geospatial location on the Earth). An online questionnaire allowed us to analyse data from 1526 respondents in 97 countries. Factor analysis showed that the direction of rotation should be studied separately for local and global movements. Handedness, footedness, and the item hypothesised to measure brain hemisphere lateralisation are predictors of rotation direction for both global and local movements. Sex is a predictor of the direction of global rotation movements but not local ones, and both sexes tend to rotate clockwise. Geospatial location does not predict the preferred direction of rotation. Our study confirms previous findings concerning the influence of handedness, footedness, and sex on human rotation; our study also provides new insight into the underlying structure of human rotation movements and excludes the Coriolis effect as a predictor of rotation.
COUNTER-ROTATION IN RELATIVISTIC MAGNETOHYDRODYNAMIC JETS
Energy Technology Data Exchange (ETDEWEB)
Cayatte, V.; Sauty, C. [Laboratoire Univers et Théories, Observatoire de Paris, UMR 8102 du CNRS, Université Paris Diderot, F-92190 Meudon (France); Vlahakis, N.; Tsinganos, K. [Department of Astrophysics, Astronomy and Mechanics, Faculty of Physics, University of Athens, 15784 Zografos, Athens (Greece); Matsakos, T. [Department of Astronomy and Astrophysics, The University of Chicago, Chicago, IL 60637 (United States); Lima, J. J. G., E-mail: veronique.cayatte@obspm.fr [Centro de Astrofísica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal)
2014-06-10
Young stellar object observations suggest that some jets rotate in the opposite direction with respect to their disk. In a recent study, Sauty et al. showed that this does not contradict the magnetocentrifugal mechanism that is believed to launch such outflows. Motion signatures that are transverse to the jet axis, in two opposite directions, have recently been measured in M87. One possible interpretation of this motion is that of counter-rotating knots. Here, we extend our previous analytical derivation of counter-rotation to relativistic jets, demonstrating that counter-rotation can indeed take place under rather general conditions. We show that both the magnetic field and a non-negligible enthalpy are necessary at the origin of counter-rotating outflows, and that the effect is associated with a transfer of energy flux from the matter to the electromagnetic field. This can be realized in three cases: if a decreasing enthalpy causes an increase of the Poynting flux, if the flow decelerates, or if strong gradients of the magnetic field are present. An illustration of the involved mechanism is given by an example of a relativistic magnetohydrodynamic jet simulation.
DEFF Research Database (Denmark)
Rasmusson, Allan; Hahn, Ute; Larsen, Jytte Overgaard
2013-01-01
to identify the specific tissue region under study. In order to use the spatial rotator in practice, however, it is necessary to be able to identify intersection points between cell boundaries and test rays in a series of parallel focal planes, also at the peripheral parts of the cell boundaries. In cases......This paper presents a new local volume estimator, the spatial rotator, which is based on measurements on a virtual 3D probe, using computer assisted microscopy. The basic design of the probe builds upon the rotator principle which requires only a few manual intersection markings, thus making...... the spatial rotator fast to use. Since a 3D probe is involved, it is expected that the spatial rotator will be more efficient than the the nucleator and the planar rotator, which are based on measurements in a single plane. An extensive simulation study shows that the spatial rotator may be more efficient...
Research on the aerodynamic characteristics of a lift drag hybrid vertical axis wind turbine
Directory of Open Access Journals (Sweden)
Xiaojing Sun
2016-01-01
Full Text Available Compared with a drag-type vertical axis wind turbines, one of the greatest advantages for a lift-type vertical axis wind turbines is its higher power coefficient (Cp. However, the lift-type vertical axis wind turbines is not a self-starting turbine as its starting torque is very low. In order to combine the advantage of both the drag-type and the lift-type vertical axis wind turbines, a lift drag hybrid vertical axis wind turbines was designed in this article and its aerodynamics and starting performance was studied in detail with the aid of computational fluid dynamics simulations. Numerical results indicate that the power coefficient of this lift drag hybrid vertical axis wind turbines declines when the distance between its drag-type blades and the center of rotation of the turbine rotor increases, whereas its starting torque can be significantly improved. Studies also show that unlike the lift-type vertical axis wind turbines, this lift drag hybrid-type vertical axis wind turbines could be able to solve the problem of low start-up torque. However, the installation position of the drag blade is very important. If the drag blade is mounted very close to the spindle, the starting torque of the lift drag hybrid-type vertical axis wind turbines may not be improved at all. In addition, it has been found that the power coefficient of the studied vertical axis wind turbines is not as good as expected and possible reasons have been provided in this article after the pressure distribution along the surfaces of the airfoil-shaped blades of the hybrid turbine was analyzed.
Millimetre Wave with Rotational Orbital Angular Momentum
Zhang, Chao; Ma, Lu
2016-01-01
Orbital angular momentum (OAM) has been widely studied in fibre and short-range communications. The implementation of millimetre waves with OAM is expected to increase the communication capacity. Most experiments demonstrate the distinction of OAM modes by receiving all of the energy in the surface vertical to the radiation axis in space. However, the reception of OAM is difficult in free space due to the non-zero beam angle and divergence of energy. The reception of OAM in the space domain in a manner similar to that in optical fibres (i.e., receiving all of the energy rings vertical to the radiation axis) is impractical, especially for long-distance transmission. Here, we fabricate a prototype of the antenna and demonstrate that rather than in the space domain, the OAM can be well received in the time domain via a single antenna by rotating the OAM wave at the transmitter, i.e., the radio wave with rotational OAM. The phase and frequency measured in the experiment reveal that for different OAM modes, the received signals act as a commonly used orthogonal frequency division multiplexing (OFDM) signal in the time domain. This phase rotation has promising prospects for use in the practical reception of different OAMs of millimetre waves in long-distance transmission. PMID:27596746
Millimetre Wave with Rotational Orbital Angular Momentum
Zhang, Chao; Ma, Lu
2016-09-01
Orbital angular momentum (OAM) has been widely studied in fibre and short-range communications. The implementation of millimetre waves with OAM is expected to increase the communication capacity. Most experiments demonstrate the distinction of OAM modes by receiving all of the energy in the surface vertical to the radiation axis in space. However, the reception of OAM is difficult in free space due to the non-zero beam angle and divergence of energy. The reception of OAM in the space domain in a manner similar to that in optical fibres (i.e., receiving all of the energy rings vertical to the radiation axis) is impractical, especially for long-distance transmission. Here, we fabricate a prototype of the antenna and demonstrate that rather than in the space domain, the OAM can be well received in the time domain via a single antenna by rotating the OAM wave at the transmitter, i.e., the radio wave with rotational OAM. The phase and frequency measured in the experiment reveal that for different OAM modes, the received signals act as a commonly used orthogonal frequency division multiplexing (OFDM) signal in the time domain. This phase rotation has promising prospects for use in the practical reception of different OAMs of millimetre waves in long-distance transmission.
Rotational dynamics of propylene inside Na-Y zeolite cages
Indian Academy of Sciences (India)
V K Sharma; Mala N Rao; Siddharth Gautam; A K Tripathi; V S Kamble; S L Chaplot; R Mukhopadhyay
2008-11-01
We report here the quasielastic neutron scattering (QENS) studies on the dynamics of propylene inside Na-Y zeolite using triple axis spectrometer (TAS) at Dhruva reactor, Trombay. Molecular dynamics (MD) simulations performed on the system had shown that the rotational motion involves energy larger than that involved in the translational motion. Therefore, rotational motion was not observed in our earlier QENS studies on propylene adsorbed Na-Y zeolite using a higher resolution spectrometer at Dhruva. Analysis of the TAS spectra revealed that the quasielastic broadening observed in propylene-loaded zeolite spectra is due to the rotational motion of the propylene molecules. This is consistent with our simulation result. Further, the rotational motion is found to be isotropic. The rotational diffusion coefficient has been obtained.
Interplay between antimagnetic and collective rotation in Fe-58
Peng, J; Zhang, S Q; Meng, J
2015-01-01
The self-consistent tilted axis cranking covariant density functional theory based on the point- coupling interaction PC-PK1 is applied to investigate the possible existence of antimagnetic ro- tation in the nucleus Fe-58. The observed data for Band 3 and Band 4 are reproduced well with two assigned configurations. It is found that both bands correspond to a rotation of antimagnetic character, but, due to the presence of considerable deformation, the interplay between antimag- netic rotation and collective motion plays an essential role. In particular for Band 4, collective rotation is dominant in the competition with antimagnetic rotation. Moreover, it is shown that the behavior of the ratios between the dynamic moments of inertia and the B(E2) values reflects the interplay between antimagnetic and collective rotation.
On the rotational dynamics of Prometheus and Pandora
Melnikov, A V; 10.1007/s10569-008-9131-z
2013-01-01
Possible rotation states of two satellites of Saturn, Prometheus (S16) and Pandora (S17), are studied by means of numerical experiments. The attitude stability of all possible modes of synchronous rotation and the motion close to these modes is analyzed by means of computation of the Lyapunov spectra of the motion. The stability analysis confirms that the rotation of Prometheus and Pandora might be chaotic, though the possibility of regular behaviour is not excluded. For the both satellites, the attitude instability zones form series of concentric belts enclosing the main synchronous resonance center in the phase space sections. A hypothesis is put forward that these belts might form "barriers" for capturing the satellites in synchronous rotation. The satellites in chaotic rotation can mimic ordinary regular synchronous behaviour: they preserve preferred orientation for long periods of time, the largest axis of satellite's figure being directed approximately towards Saturn.
Numerical simulation of negative Magnus force on a rotating sphere
Muto, Masaya; Tsubokura, Makoto; Oshima, Nobuyuki
2010-11-01
Flow characteristics and fluid force on a sphere rotating along with axis perpendicular to mean air flow were investigated using Large Eddy Simulation at two different Reynolds numbers of 10,000 and 200,000. As a result of simulation, opposite flow characteristics around the sphere and displacement of the separation point were visualized depending on the Reynolds number even though the sphere rotates at the same rotation speed according to the Reynolds number. When Reynolds number is 10,000, flow characteristics agree with the flow field explained in the Magnus effect. However sphere rotates at the same rotation speed while increasing Reynolds number to 200,000, separation point moves in opposite direction and wake appears in the different direction. The reason of the negative Magnus force was discussed in terms of the boundary layer transition on the surface.
On the invariant motions of rigid body rotation over the fixed point, via Euler angles
Ershkov, Sergey V
2016-01-01
The generalized Euler case (rigid body rotation over the fixed point) is discussed here: - the center of masses of non-symmetric rigid body is assumed to be located at the equatorial plane on axis Oy which is perpendicular to the main principal axis Ox of inertia at the fixed point. Such a case was presented in the rotating coordinate system, in a frame of reference fixed in the rotating body for the case of rotation over the fixed point (at given initial conditions). In our derivation, we have represented the generalized Euler case in the fixed Cartesian coordinate system; so, the motivation of our ansatz is to elegantly transform the proper components of the previously presented solution from one (rotating) coordinate system to another (fixed) Cartesian coordinates. Besides, we have obtained an elegantly analytical case of general type of rotations; also, we have presented it in the fixed Cartesian coordinate system via Euler angles.
Coherent Structures and Extreme Events in Rotating Multiphase Turbulent Flows
Directory of Open Access Journals (Sweden)
L. Biferale
2016-11-01
Full Text Available By using direct numerical simulations (DNS at unprecedented resolution, we study turbulence under rotation in the presence of simultaneous direct and inverse cascades. The accumulation of energy at large scale leads to the formation of vertical coherent regions with high vorticity oriented along the rotation axis. By seeding the flow with millions of inertial particles, we quantify—for the first time—the effects of those coherent vertical structures on the preferential concentration of light and heavy particles. Furthermore, we quantitatively show that extreme fluctuations, leading to deviations from a normal-distributed statistics, result from the entangled interaction of the vertical structures with the turbulent background. Finally, we present the first-ever measurement of the relative importance between Stokes drag, Coriolis force, and centripetal force along the trajectories of inertial particles. We discover that vortical coherent structures lead to unexpected diffusion properties for heavy and light particles in the directions parallel and perpendicular to the rotation axis.
Coherent Structures and Extreme Events in Rotating Multiphase Turbulent Flows
Biferale, L.; Bonaccorso, F.; Mazzitelli, I. M.; van Hinsberg, M. A. T.; Lanotte, A. S.; Musacchio, S.; Perlekar, P.; Toschi, F.
2016-10-01
By using direct numerical simulations (DNS) at unprecedented resolution, we study turbulence under rotation in the presence of simultaneous direct and inverse cascades. The accumulation of energy at large scale leads to the formation of vertical coherent regions with high vorticity oriented along the rotation axis. By seeding the flow with millions of inertial particles, we quantify—for the first time—the effects of those coherent vertical structures on the preferential concentration of light and heavy particles. Furthermore, we quantitatively show that extreme fluctuations, leading to deviations from a normal-distributed statistics, result from the entangled interaction of the vertical structures with the turbulent background. Finally, we present the first-ever measurement of the relative importance between Stokes drag, Coriolis force, and centripetal force along the trajectories of inertial particles. We discover that vortical coherent structures lead to unexpected diffusion properties for heavy and light particles in the directions parallel and perpendicular to the rotation axis.
Antenna Axis Offset Estimation from VLBI
Kurdubov, Sergey; Skurikhina, Elena
2010-01-01
The antenna axis offsets were estimated from global solutions and single sessions. We have built a set of global solutions from R1 and R4 sessions and from the sets of sessions between SVETLOE repairs. We compared our estimates with local survey data for the stations of the QUASAR network. Svetloe station axis offset values have changed after repairs. For non-global networks, the axis offset value of a single station can significantly affect the EOP estimations.
Rotation of single live mammalian cells using dynamic holographic optical tweezers
Bin Cao; Kelbauskas, Laimonas; Chan, Samantha; Shetty, Rishabh M.; Smith, Dean; Meldrum, Deirdre R.
2017-05-01
We report on a method for rotating single mammalian cells about an axis perpendicular to the optical system axis through the imaging plane using dynamic holographic optical tweezers (HOTs). Two optical traps are created on the opposite edges of a mammalian cell and are continuously transitioned through the imaging plane along the circumference of the cell in opposite directions, thus providing the torque to rotate the cell in a controlled fashion. The method enables a complete 360° rotation of live single mammalian cells with spherical or near-to spherical shape in 3D space, and represents a useful tool suitable for the single cell analysis field, including tomographic imaging.
Time-odd mean fields in the rotating frame microscopic nature of nuclear magnetism
Afanasiev, A V
2000-01-01
The microscopic role of nuclear magnetism in rotating frame is investigated for the first time in the framework of the cranked relativistic mean field theory. It is shown that nuclear magnetism modifies the expectation values of single-particle spin, orbital and total angular momenta along the rotational axis effectively creating additional angular momentum. This effect leads to the increase of kinematic and dynamic moments of inertia at given rotational frequency and has an impact on effective alignments.
3D CFD Analysis of a Vertical Axis Wind Turbine
Directory of Open Access Journals (Sweden)
Andrea Alaimo
2015-04-01
Full Text Available To analyze the complex and unsteady aerodynamic flow associated with wind turbine functioning, computational fluid dynamics (CFD is an attractive and powerful method. In this work, the influence of different numerical aspects on the accuracy of simulating a rotating wind turbine is studied. In particular, the effects of mesh size and structure, time step and rotational velocity have been taken into account for simulation of different wind turbine geometries. The applicative goal of this study is the comparison of the performance between a straight blade vertical axis wind turbine and a helical blade one. Analyses are carried out through the use of computational fluid dynamic ANSYS® Fluent® software, solving the Reynolds averaged Navier–Stokes (RANS equations. At first, two-dimensional simulations are used in a preliminary setup of the numerical procedure and to compute approximated performance parameters, namely the torque, power, lift and drag coefficients. Then, three-dimensional simulations are carried out with the aim of an accurate determination of the differences in the complex aerodynamic flow associated with the straight and the helical blade turbines. Static and dynamic results are then reported for different values of rotational speed.
Spontaneous transfer of chirality in an atropisomerically enriched two-axis system.
Barrett, Kimberly T; Metrano, Anthony J; Rablen, Paul R; Miller, Scott J
2014-05-01
One of the most well-recognized stereogenic elements in a chiral molecule is an sp(3)-hybridized carbon atom that is connected to four different substituents. Axes of chirality can also exist about bonds with hindered barriers of rotation; molecules containing such axes are known as atropisomers. Understanding the dynamics of these systems can be useful, for example, in the design of single-atropisomer drugs or molecular switches and motors. For molecules that exhibit a single axis of chirality, rotation about that axis leads to racemization as the system reaches equilibrium. Here we report a two-axis system for which an enantioselective reaction produces four stereoisomers (two enantiomeric pairs): following a catalytic asymmetric transformation, we observe a kinetically controlled product distribution that is perturbed from the system's equilibrium position. As the system undergoes isomerization, one of the diastereomeric pairs drifts spontaneously to a higher enantiomeric ratio. In a compensatory manner, the enantiomeric ratio of the other diastereomeric pair decreases. These observations are made for a class of unsymmetrical amides that exhibits two asymmetric axes--one axis is defined through a benzamide substructure, and the other axis is associated with differentially N,N-disubstituted amides. The stereodynamics of these substrates provides an opportunity to observe a curious interplay of kinetics and thermodynamics intrinsic to a system of stereoisomers that is constrained to a situation of partial equilibrium.
Tunable magnetocrystalline easy axis in cobalt nanowire arrays by zinc additive
Energy Technology Data Exchange (ETDEWEB)
Manouchehri, A. [Institute of Nanoscience and Nanotechnology, University of Kashan, Kashan 87317-51167 (Iran, Islamic Republic of); Ramazani, A., E-mail: rmzn@kashanu.ac.ir [Institute of Nanoscience and Nanotechnology, University of Kashan, Kashan 87317-51167 (Iran, Islamic Republic of); Department of Physics, University of Kashan, Kashan 87317-51167 (Iran, Islamic Republic of); Kashi, M. Almasi [Institute of Nanoscience and Nanotechnology, University of Kashan, Kashan 87317-51167 (Iran, Islamic Republic of); Department of Physics, University of Kashan, Kashan 87317-51167 (Iran, Islamic Republic of); Montazer, A.H. [Institute of Nanoscience and Nanotechnology, University of Kashan, Kashan 87317-51167 (Iran, Islamic Republic of)
2016-05-15
Graphical abstract: - Highlights: • Pure Co and Co-rich CoZn NW arrays were fabricated into AAO templates. • Effect of Zn additive on magnetic properties and crystal structure was investigated. • Coercivity and squareness of Co NWs increased up to 2150 Oe and 0.93 by Zn additive. • Incorporation of Zn rotated Co c-axis from perpendicular to parallel to NW axis. - Abstract: A new approach to tuning the crystalline characteristics and magnetic properties of cobalt nanowire (NW) arrays embedded in AAO templates is reported using zinc additive. This is realized by adding low concentrations of Zn when pulse-electrodepositing cobalt NWs while also increasing the solution pH from 3 to 5. Using hysteresis loop measurements with a magnetic field applied parallel to the NW axis, coercivity and squareness of pure cobalt NWs increased from 890 Oe and 0.45 to 2150 Oe and 0.93 in Co{sub 97}Zn{sub 3} NWs, respectively, using a Zn concentration of 0.01 M at pH = 4. XRD patterns obtained from the cobalt-rich CoZn NWs revealed that the crystalline texture of cobalt changes from [1 0 0] direction to [1 0 1] and [0 0 2] at pH = 3 and 4, respectively. For the latter, the magnetocrystalline easy axis of cobalt rotates from nearly perpendicular to parallel to the NW axis, induced by the incorporation of zinc into the hcp structure of cobalt.
A numerical method of tracing a vortical axis along local topological axis line
Nakayama, Katsuyuki; Hasegawa, Hideki
2016-06-01
A new numerical method is presented to trace or identify a vortical axis in flow, which is based on Galilean invariant flow topology. We focus on the local flow topology specified by the eigenvalues and eigenvectors of the velocity gradient tensor, and extract the axis component from its flow trajectory. Eigen-vortical-axis line is defined from the eigenvector of the real eigenvalue of the velocity gradient tensor where the tensor has the conjugate complex eigenvalues. This numerical method integrates the eigen-vortical-axis line and traces a vortical axis in terms of the invariant flow topology, which enables to investigate the feature of the topology-based vortical axis.
Principles of the prolactin/vasoinhibin axis.
Triebel, Jakob; Bertsch, Thomas; Bollheimer, Cornelius; Rios-Barrera, Daniel; Pearce, Christy F; Hüfner, Michael; Martínez de la Escalera, Gonzalo; Clapp, Carmen
2015-11-15
The hormonal family of vasoinhibins, which derive from the anterior pituitary hormone prolactin, are known for their inhibiting effects on blood vessel growth, vasopermeability, and vasodilation. As pleiotropic hormones, vasoinhibins act in multiple target organs and tissues. The generation, secretion, and regulation of vasoinhibins are embedded into the organizational principle of an axis, which integrates the hypothalamus, the pituitary, and the target tissue microenvironment. This axis is designated as the prolactin/vasoinhibin axis. Disturbances of the prolactin/vasoinhibin axis are associated with the pathogenesis of retinal and cardiac diseases and with diseases occurring during pregnancy. New phylogenetical, physiological, and clinical implications are discussed.
Acute injuries of the axis vertebra
Energy Technology Data Exchange (ETDEWEB)
Burke, J.T. (United General Hospital, Sedro Woolley, WA (USA)); Harris, J.H. (Texas Univ., Houston, TX (USA). Dept. of Radiology)
1989-08-01
A retrospective analysis of 165 patients admitted to Hermann Hospital with acute injuries of the axis vertebra revealed 68 (41%) dens fractures, 62 (38%) cases of traumatic spondylolisthesis ('hangman's' fracture), 21 (13%) extension teardrop fractures, 10 (6%) hyperextension dislocations, and 2 (1.0%) fractures each of the laminae and spinous processes. Of the axis injuries 31 (18%) were limited to the axis body alone. Of these, 21 (61%) were hyperextension teardrop fractures and 10 (32%) were hyperextension dislocations. Axis injuries were associated with acute injuries of other cervical vertebrae in 14 (8%) of the patients. (orig./GDG).
Differential rotation of the unstable nonlinear r -modes
Friedman, John L.; Lindblom, Lee; Lockitch, Keith H.
2016-01-01
At second order in perturbation theory, the r -modes of uniformly rotating stars include an axisymmetric part that can be identified with differential rotation of the background star. If one does not include radiation reaction, the differential rotation is constant in time and has been computed by Sá. It has a gauge dependence associated with the family of time-independent perturbations that add differential rotation to the unperturbed equilibrium star: For stars with a barotropic equation of state, one can add to the time-independent second-order solution arbitrary differential rotation that is stratified on cylinders (that is a function of distance ϖ to the axis of rotation). We show here that the gravitational radiation-reaction force that drives the r -mode instability removes this gauge freedom; the exponentially growing differential rotation of the unstable second-order r -mode is unique. We derive a general expression for this rotation law for Newtonian models and evaluate it explicitly for slowly rotating models with polytropic equations of state.
Perceptual strategies of pigeons to detect a rotational centre--a hint for star compass learning?
Directory of Open Access Journals (Sweden)
Bianca Alert
Full Text Available Birds can rely on a variety of cues for orientation during migration and homing. Celestial rotation provides the key information for the development of a functioning star and/or sun compass. This celestial compass seems to be the primary reference for calibrating the other orientation systems including the magnetic compass. Thus, detection of the celestial rotational axis is crucial for bird orientation. Here, we use operant conditioning to demonstrate that homing pigeons can principally learn to detect a rotational centre in a rotating dot pattern and we examine their behavioural response strategies in a series of experiments. Initially, most pigeons applied a strategy based on local stimulus information such as movement characteristics of single dots. One pigeon seemed to immediately ignore eccentric stationary dots. After special training, all pigeons could shift their attention to more global cues, which implies that pigeons can learn the concept of a rotational axis. In our experiments, the ability to precisely locate the rotational centre was strongly dependent on the rotational velocity of the dot pattern and it crashed at velocities that were still much faster than natural celestial rotation. We therefore suggest that the axis of the very slow, natural, celestial rotation could be perceived by birds through the movement itself, but that a time-delayed pattern comparison should also be considered as a very likely alternative strategy.
Perceptual strategies of pigeons to detect a rotational centre--a hint for star compass learning?
Alert, Bianca; Michalik, Andreas; Helduser, Sascha; Mouritsen, Henrik; Güntürkün, Onur
2015-01-01
Birds can rely on a variety of cues for orientation during migration and homing. Celestial rotation provides the key information for the development of a functioning star and/or sun compass. This celestial compass seems to be the primary reference for calibrating the other orientation systems including the magnetic compass. Thus, detection of the celestial rotational axis is crucial for bird orientation. Here, we use operant conditioning to demonstrate that homing pigeons can principally learn to detect a rotational centre in a rotating dot pattern and we examine their behavioural response strategies in a series of experiments. Initially, most pigeons applied a strategy based on local stimulus information such as movement characteristics of single dots. One pigeon seemed to immediately ignore eccentric stationary dots. After special training, all pigeons could shift their attention to more global cues, which implies that pigeons can learn the concept of a rotational axis. In our experiments, the ability to precisely locate the rotational centre was strongly dependent on the rotational velocity of the dot pattern and it crashed at velocities that were still much faster than natural celestial rotation. We therefore suggest that the axis of the very slow, natural, celestial rotation could be perceived by birds through the movement itself, but that a time-delayed pattern comparison should also be considered as a very likely alternative strategy.
Increasing Plant Availability by Mechanical Checking of the Cement Rotary Kiln Axis
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
A periodic check of the cement rotary kiln axis is needed within the framework of preventive maintenance for maintaining high plant availability. The fourth generation “KAS-4” measuring system was developed by Wuhan University of Technology in 1999. The system can be carried out with rotating or stationary kiln plant. The same is true of the measurement of tire and supporting roller diameters, the clearance of tires, the position of rollers, the machining of tires and rollers, the slopes of roller surfaces, the deflection of gear, the axis of kiln. The system has been applied to the measurement for 10 sets of cement rotary kiln in China.
Desai, Naeem M.; Lionheart, William R. B.
2016-11-01
We give an explicit plane-by-plane filtered back-projection reconstruction algorithm for the transverse ray transform of symmetric second rank tensor fields on Euclidean three-space, using data from rotation about three orthogonal axes. We show that in the general case two-axis data is insufficient, but we give an explicit reconstruction procedure for the potential case with two-axis data. We describe a numerical implementation of the three-axis algorithm and give reconstruction results for simulated data.
Energy Technology Data Exchange (ETDEWEB)
Butterfield, C.P.; Musial, W.P.; Simms, D.A.
1992-10-01
How does wind tunnel airfoil data differ from the airfoil performance on an operating horizontal axis wind turbine (HAWT) The National Renewable Energy laboratory has been conducting a comprehensive test program focused on answering this question and understanding the basic fluid mechanics of rotating HAWT stall aerodynamics. The basic approach was to instrument a wind rotor, using an airfoil that was well documented by wind tunnel tests, and measure operating pressure distributions on the rotating blade. Based an the integrated values of the pressure data, airfoil performance coefficients were obtained, and comparisons were made between the rotating data and the wind tunnel data. Care was taken to the aerodynamic and geometric differences between the rotating and the wind tunnel models. This is the first of two reports describing the Combined Experiment Program and its results. This Phase I report covers background information such as test setup and instrumentation. It also includes wind tunnel test results and roughness testing.
Entropy generation of radial rotation convective channels
Alić, Fikret
2012-03-01
The exchange of heat between two fluids is established by radial rotating pipe or a channel. The hotter fluid flows through the pipe, while the cold fluid is ambient air. Total length of pipe is made up of multiple sections of different shape and position in relation to the common axis of rotation. In such heat exchanger the hydraulic and thermal irreversibility of the hotter and colder fluid occur. Therefore, the total entropy generated within the radial rotating pipe consists of the total entropy of hotter and colder fluid, taking into account all the hydraulic and thermal irreversibility of both fluids. Finding a mathematical model of the total generated entropy is based on coupled mathematical expressions that combine hydraulic and thermal effects of both fluids with the complex geometry of the radial rotating pipe. Mathematical model follows the each section of the pipe and establishes the function between the sections, so the total generated entropy is different from section to section of the pipe. In one section of the pipe thermal irreversibility may dominate over the hydraulic irreversibility, while in another section of the pipe the situation may be reverse. In this paper, continuous analytic functions that connect sections of pipe in geometric meaning are associated with functions that describe the thermo-hydraulic effects of hotter and colder fluid. In this way, the total generated entropy of the radial rotating pipe is a continuous analytic function of any complex geometry of the rotating pipe. The above method of establishing a relationship between the continuous function of entropy with the complex geometry of the rotating pipe enables indirect monitoring of unnecessary hydraulic and thermal losses of both fluids. Therefore, continuous analytic functions of generated entropy enable analysis of hydraulic and thermal irreversibility of individual sections of pipe, as well as the possibility of improving the thermal-hydraulic performance of the rotating
Image data rate converter having a drum with a fixed head and a rotatable head
Billingsley, F. C. (Inventor)
1973-01-01
A data-rate converter is disclosed comprising a rotatable data-storing drum with at least one fixed read/record head and a rotatable read/record head. The latter is rotatable in a circular path about the drum axis of rotation. The drum is positionable in any one of a plurality of axial positions with respect to the heads, so that at least one drum track is aligned with the fixed head in one drum position and with the rotatable head in another drum position. When a track is aligned with the fixed head, data may be recorded therin or read out therefrom at a rate which is a function of drum rotation, while when aligned with the rotatable head, data may be recorded or read out at a rate which is a function of the rates and directions of rotation of both the drum and the head.
Relativistic Rotating Vector Model
Lyutikov, Maxim
2016-01-01
The direction of polarization produced by a moving source rotates with the respect to the rest frame. We show that this effect, induced by pulsar rotation, leads to an important correction to polarization swings within the framework of rotating vector model (RVM); this effect has been missed by previous works. We construct relativistic RVM taking into account finite heights of the emission region that lead to aberration, time-of-travel effects and relativistic rotation of polarization. Polarizations swings at different frequencies can be used, within the assumption of the radius-to-frequency mapping, to infer emission radii and geometry of pulsars.
Design and analysis of a dual-axis resonator fiber-optic gyroscope employing a single source.
Pinnoji, Prerana Dabral; Nayak, Jagannath
2013-08-01
In this paper, design of a resonator fiber-optic gyroscope comprised of a single laser source and two optical fiber resonator rings is presented. A typical gyroscope measures angular rotation around a fixed axis, whereas the proposed design can sense simultaneous rotation about two orthogonal axes. Two variants of the design are proposed and analyzed using a mathematical model based on Jones matrix methodology.
National Research Council Canada - National Science Library
Heilmann, René; Gräfe, Markus; Nolte, Stefan; Szameit, Alexander
2014-01-01
.... In our work we close this gap and present Hadamard, Pauli-X, and rotation gates of high fidelity for photonic polarisation qubits on chip by employing a reorientation of the optical axis of birefringent waveguides...
Strongly magnetized rotating dipole in general relativity
Petri, J
2016-01-01
Electromagnetic waves arise in many area of physics. Solutions are difficult to find in the general case. In this paper, we numerically integrate Maxwell equations in a 3D spherical polar coordinate system. Straightforward finite difference methods would lead to a coordinate singularity along the polar axis. Spectral methods are better suited to deal with such artificial singularities related to the choice of a coordinate system. When the radiating object is rotating like for instance a star, special classes of solutions to Maxwell equations are worthwhile to study such as quasi-stationary regimes. Moreover, in high-energy astrophysics, strong gravitational and magnetic fields are present especially around rotating neutron stars. In order to study such systems, we designed an algorithm to solve the time-dependent Maxwell equations in spherical polar coordinates including general relativity as well as quantum electrodynamical corrections to leading order. As a diagnostic, we compute the spindown luminosity exp...
Magnetohydrodynamic Flow Between Concentric Rotating Porous Cylinders
Directory of Open Access Journals (Sweden)
S. N. Dube
1971-10-01
Full Text Available An attempt has been made to study the steady laminar flow of a incompressible electrically conducting fluid between infinitely long concentric rotating porous cylinders under the influence of radial magnetic field. A solution has been obtained under the assumption of uniform conditions along the axis of the cylinders. The cylinders being porous, a hyperbolic radial velocity distribution has been superimposed over the circumferential velocity produced due to rotation. There is a Bernoulli type pressure variation in the radial in the direction. When the inner cylinder is at rest the shearing stress at it and the torque transmitted to it decrease as R (=v/Sub/1y/Sub1/v= v/Sub2y/Sub2/v increases and the magnetic parameter lambda (=4sigma mue/sube/sup2A/Sup2/Mue will further decrease them.
MEMS inertial sensors with integral rotation means.
Energy Technology Data Exchange (ETDEWEB)
Kohler, Stewart M.
2003-09-01
The state-of-the-art of inertial micro-sensors (gyroscopes and accelerometers) has advanced to the point where they are displacing the more traditional sensors in many size, power, and/or cost-sensitive applications. A factor limiting the range of application of inertial micro-sensors has been their relatively poor bias stability. The incorporation of an integral sensitive axis rotation capability would enable bias mitigation through proven techniques such as indexing, and foster the use of inertial micro-sensors in more accuracy-sensitive applications. Fabricating the integral rotation mechanism in MEMS technology would minimize the penalties associated with incorporation of this capability, and preserve the inherent advantages of inertial micro-sensors.
Optical design of a rotating eyepiece telescope
Siddique, M.; Nasim, F.; Khan, A. N.; Gul, A.
2016-08-01
Flexible eyepiece telescope has been designed and verified. The rotating eyepiece of telescope will facilitate viewing of objects in a remote or out of sight target. Eyepiece arm of telescope can be rotated upto 360o keeping objective and reticule unchanged and ensuring zero deviation in reticule inclination. Main application of this scope is off axis viewing of objects. Image inversion has been carried out by using pair of mirrors and length of telescope is controlled by using relay lenses. The optical design, simulation and image analysis has been carried out by using ZEMAX®. Magnification of telescope is between 10∼⃒12 times with FOV of 60. Experiment has been carried out using uncoated Edmund Optics and optical tool box of Micro Series Kit, NEWPORT.
State reconstruction of molecular spatial rotation
Institute of Scientific and Technical Information of China (English)
Qin Xiao; Gao Jun-Yi
2012-01-01
We establish a reconstruction approach for the rotational quantum state of linear molecules possessing a magnetic manifold.Our approximate method contains an iteration with generalized matrix inverses,processing the tomographic integral of the time-dependent molecular-axis distribution in a polar angle.As shown in a simulated example for an alignment state,the density matrix is determined in a high fidelity.An analytic tomographic formula is also derived for the symmetric top rotation.The state coherent in the quantun space of both the angular momentum and its magnetic projection can be approximately retrieved from the observable time-resolved solid-angle distribution of the molecular.
Innovative Design of Vertical Axis Wind Turbine
DEFF Research Database (Denmark)
Chougule, Prasad
2013-01-01
The wind turbines can be classified as: i) Horizontal axis wind turbines (HAWT), and ii) Vertical axis wind turbines (VAWT). The HAWT is fully developed and the size is growing higher. Whereas, the VAWT is not developed because of the less efficiency and vibration issues of big structure. However...
Differential rotation in solar-like stars from global simulations
Energy Technology Data Exchange (ETDEWEB)
Guerrero, G.; Kosovichev, A. G. [Solar Physics, HEPL, Stanford University, 452 Lomita Mall, Stanford, CA 94305-4085 (United States); Smolarkiewicz, P. K. [European Centre for Medium-Range Weather Forecasts, Reading RG2 9AX (United Kingdom); Mansour, N. N., E-mail: gag@stanford.edu, E-mail: sasha@sun.stanford.edu, E-mail: smolar@ecmwf.int, E-mail: nagi.n.mansour@nasa.gov [NASA, Ames Research Center, Moffett Field, Mountain View, CA 94040 (United States)
2013-12-20
To explore the physics of large-scale flows in solar-like stars, we perform three-dimensional anelastic simulations of rotating convection for global models with stratification resembling the solar interior. The numerical method is based on an implicit large-eddy simulation approach designed to capture effects from non-resolved small scales. We obtain two regimes of differential rotation, with equatorial zonal flows accelerated either in the direction of rotation (solar-like) or in the opposite direction (anti-solar). While the models with the solar-like differential rotation tend to produce multiple cells of meridional circulation, the models with anti-solar differential rotation result in only one or two meridional cells. Our simulations indicate that the rotation and large-scale flow patterns critically depend on the ratio between buoyancy and Coriolis forces. By including a sub-adiabatic layer at the bottom of the domain, corresponding to the stratification of a radiative zone, we reproduce a layer of strong radial shear similar to the solar tachocline. Similarly, enhanced super-adiabaticity at the top results in a near-surface shear layer located mainly at lower latitudes. The models reveal a latitudinal entropy gradient localized at the base of the convection zone and in the stable region, which, however, does not propagate across the convection zone. In consequence, baroclinicity effects remain small, and the rotation isocontours align in cylinders along the rotation axis. Our results confirm the alignment of large convective cells along the rotation axis in the deep convection zone and suggest that such 'banana-cell' pattern can be hidden beneath the supergranulation layer.
Lukerchenko, N. (Nikolay); Keita, I. (Ibrahima); Kvurt, Y.; Miles, J.
2010-01-01
The drag torque, drag force and Magnus force acting on a spheroid rotating around its axis of symmetry and moving perpendicularly to this axis in initially quiescent water were studied using experimental data and numerical simulation. The prolate spheroid with ratio of the axes 4/3 was speeded up in special device, which ensured the required rotational and translational velocity in the given plane. A video system was used to record the spheroid motion in water. Using the video records the sph...
Rotational motion of Foton M-4
Abrashkin, V. I.; Voronov, K. E.; Piyakov, I. V.; Puzin, Yu. Ya.; Sazonov, V. V.; Semkin, N. D.; Chebukov, S. Yu.
2016-07-01
The actual controlled rotational motion of the Foton M-4 satellite is reconstructed for the mode of single-axis solar orientation. The reconstruction was carried out using data of onboard measurements of vectors of angular velocity and the strength of the Earth's magnetic field. The reconstruction method is based on the reconstruction of the kinematic equations of the rotational motion of a solid body. According to the method, measurement data of both types collected at a certain time interval are processed together. Measurements of the angular velocity are interpolated by piecewise-linear functions, which are substituted in kinematic differential equations for a quaternion that defines the transition from the satellite instrument coordinate system to the inertial coordinate system. The obtained equations represent the kinematic model of the satellite rotational motion. A solution of these equations that approximates the actual motion is derived from the condition of the best (in the sense of the least squares method) match between the measurement data of the strength vector of the Earth's magnetic field and its calculated values. The described method makes it possible to reconstruct the actual rotational satellite motion using one solution of kinematic equations over time intervals longer than 10 h. The found reconstructions have been used to calculate the residual microaccelerations.
The Short Rotation Period of Nereid
Grav, T; Kavelaars, J J
2003-01-01
We determine the period, p = 11.52 \\pm 0.14 h, and a light curve peak-to-peak amplitude, a = 0.029 \\pm 0.003 magnitudes, of the Neptunian irregular satellite Nereid. If the light curve variation is due to albedo variations across the surface, rather than solely to the shape of Nereid variations, the rotation period would be a factor of two shorter. In either case, such a rotation period and light curve amplitude, together with Nereid's orbital period, p=360.14 days, imply that Nereid is almost certainly in a regular rotation state, rather than the chaotic rotation state suggested by Schaefer and Schaefer (1988,2000) and Dobrovolskis (1995). Assuming that Nereid is perfectly spherical, the albedo variation is 3% across the observed surface. Assuming a uniform geometric albedo, the observed cross sectional area varies by 3%. We caution that the lightcurve found in this paper only sets limits on the combination of albedo and physical irregularity and that we cannot determine the orientation of Nereid's spin axis...
Streaming potential near a rotating porous disk.
Prieve, Dennis C; Sides, Paul J
2014-09-23
Theory and experimental results for the streaming potential measured in the vicinity of a rotating porous disk-shaped sample are described. Rotation of the sample on its axis draws liquid into its face and casts it from the periphery. Advection within the sample engenders streaming current and streaming potential that are proportional to the zeta potential and the disk's major dimensions. When Darcy's law applies, the streaming potential is proportional to the square of the rotation at low rate but becomes invariant with rotation at high rate. The streaming potential is invariant with the sample's permeability at low rate and is proportional to the inverse square of the permeability at high rate. These predictions were tested by determining the zeta potential and permeability of the loop side of Velcro, a sample otherwise difficult to characterize; reasonable values of -56 mV for zeta and 8.7 × 10(-9) m(2) for the permeability were obtained. This approach offers the ability to determine both the zeta potential and the permeability of materials having open structures. Compressing them into a porous plug is unnecessary. As part of the development of the theory, a convenient formula for a flow-weighted volume-averaged space-charge density of the porous medium, -εζ/k, was obtained, where ε is the permittivity, ζ is the zeta potential, and k is the Darcy permeability. The formula is correct when Smoluchowski's equation and Darcy's law are both valid.
Active Blade Pitch Control for Straight Bladed Darrieus Vertical Axis Wind Turbine of New Design
DEFF Research Database (Denmark)
Chougule, Prasad; Nielsen, Søren R.K.; Basu, Biswajit
2013-01-01
at low rotational speed producing very less noise during operation, although these are less efficient than Horizontal Axis Wind Turbines (HAWT). The efficiency of a VAWT has been significantly improved by H-Darrieus VAWT design based on double airfoil technology as demonstrated by the authors...... in a previous publication. Further, it is well know that the variation of the blade pitch angle during the rotation improves the power efficiency. A blade pitch variation is implemented by active blade pitch control, which operates as per wind speed and position of the blade with respect to the rotor. A double...
Development of methodology for horizontal-axis wind-turbine dynamic analysis. Summary report
Energy Technology Data Exchange (ETDEWEB)
Dugundji, J.
1982-09-01
The 3-year effort reported included: (1) review of the MOSTAS computer programs for dynamic analysis of horizontal-axis wind turbines; (2) review of various analysis methods for rotating systems with periodic coefficients; (3) review of structural dynamics analysis tools for large wind turbine; (4) experiments for yaw characteristics of a rotating rotar; (5) development of a finite element model for rotors; (6) development of simple models for aeroelastic; and (7) development of simple models for stability and response of wind turbines on flexible towers.
Deconstructing Mental Rotation
DEFF Research Database (Denmark)
Larsen, Axel
2014-01-01
A random walk model of the classical mental rotation task is explored in two experiments. By assuming that a mental rotation is repeated until sufficient evidence for a match/mismatch is obtained, the model accounts for the approximately linearly increasing reaction times (RTs) on positive trials...... alignment take place during fixations at very high speed....
Philip E. Pope; Jeffery O. Dawson
1989-01-01
Short-rotation plantations offer several advantages over longer, more traditional rotations. They enhance the natural productivity of better sites and of tree species with rapid juvenile growth. Returns on investment are realized in a shorter period and the risk of loss is reduced compared with long term investments. Production of wood and fiber can be maximized by...
Faraday rotation measure synthesis
Brentjens, MA; de Bruyn, AG
2005-01-01
We extend the rotation measure work of Burn ( 1966, MNRAS, 133, 67) to the cases of limited sampling of lambda(2) space and non-constant emission spectra. We introduce the rotation measure transfer function (RMTF), which is an excellent predictor of n pi ambiguity problems with the lambda(2) coverag
Le Vine, David
2016-01-01
Faraday rotation is a change in the polarization as signal propagates through the ionosphere. At L-band it is necessary to correct for this change and measurements are made on the spacecraft of the rotation angle. These figures show that there is good agreement between the SMAP measurements (blue) and predictions based on models (red).
Design and implementation of five-axis transformation function in CNC system
Directory of Open Access Journals (Sweden)
Wang Feng
2014-04-01
Full Text Available To implement five-axis functions in CNC system, based on domestic system Lan Tian series, an improved design method for the system software structure is proposed in this paper. The numerical control kernel of CNC system is divided into the task layer and the motion layer. A five-axis transformation unit is integrated into the motion layer. After classifying five-axis machines into different types and analyzing their geometry information, the five-axis kinematic library is designed according to the abstract factory pattern. Furthermore, by taking CA spindle-tilting machine as an example, the forward and the inverse kinematic transformations are deduced. Based on the new software architecture and the five-axis kinematic library, algorithms of RTCP (rotation tool center point control and 3D radius compensation for end-milling are designed and realized. The milling results show that, with five-axis functions based on such software structure, the instructions with respect to the cutter’s position and orientation can be directly carried out in the CNC system.
Identification of Kinematic Errors of Five-axis Machine Tool Trunnion Axis from Finished Test Piece
Institute of Scientific and Technical Information of China (English)
ZHANG Ya; FU Jianzhong; CHEN Zichen
2014-01-01
Compared with the traditional non-cutting measurement, machining tests can more accurately reflect the kinematic errors of five-axis machine tools in the actual machining process for the users. However, measurement and calculation of the machining tests in the literature are quite difficult and time-consuming. A new method of the machining tests for the trunnion axis of five-axis machine tool is proposed. Firstly, a simple mathematical model of the cradle-type five-axis machine tool was established by optimizing the coordinate system settings based on robot kinematics. Then, the machining tests based on error-sensitive directions were proposed to identify the kinematic errors of the trunnion axis of cradle-type five-axis machine tool. By adopting the error-sensitive vectors in the matrix calculation, the functional relationship equations between the machining errors of the test piece in the error-sensitive directions and the kinematic errors of C-axis and A-axis of five-axis machine tool rotary table was established based on the model of the kinematic errors. According to our previous work, the kinematic errors of C-axis can be treated as the known quantities, and the kinematic errors of A-axis can be obtained from the equations. This method was tested in Mikron UCP600 vertical machining center. The machining errors in the error-sensitive directions can be obtained by CMM inspection from the finished test piece to identify the kinematic errors of five-axis machine tool trunnion axis. Experimental results demonstrated that the proposed method can reduce the complexity, cost, and the time consumed substantially, and has a wider applicability. This paper proposes a new method of the machining tests for the trunnion axis of five-axis machine tool.
De Lorenci, V A
1996-01-01
We investigate which mapping we have to use to compare measurements made in a rotating frame to those made in an inertial frame. Using a "Lorentz-like" coordinate transformation we obtain that creation-anihilation operators of a massless scalar field in the rotating frame are not the same as those of an inertial observer. This leads to a new vacuum state (a rotating vacuum) which is a superposition of positive and negative frequency Minkowski particles. After this, introducing an apparatus device coupled linearly with the field we obtain that there is a strong correlation between number of rotating particles (in a given state) obtained via canonical quantization and via response function of the rotating detector. Finally, we analyse polarization effects in circular accelerators in the proper frame of the electron making a connection with the inertial frame point of view.
Uniformly rotating neutron stars
Boshkayev, Kuantay
2016-01-01
In this chapter we review the recent results on the equilibrium configurations of static and uniformly rotating neutron stars within the Hartle formalism. We start from the Einstein-Maxwell-Thomas-Fermi equations formulated and extended by Belvedere et al. (2012, 2014). We demonstrate how to conduct numerical integration of these equations for different central densities ${\\it \\rho}_c$ and angular velocities $\\Omega$ and compute the static $M^{stat}$ and rotating $M^{rot}$ masses, polar $R_p$ and equatorial $R_{\\rm eq}$ radii, eccentricity $\\epsilon$, moment of inertia $I$, angular momentum $J$, as well as the quadrupole moment $Q$ of the rotating configurations. In order to fulfill the stability criteria of rotating neutron stars we take into considerations the Keplerian mass-shedding limit and the axisymmetric secular instability. Furthermore, we construct the novel mass-radius relations, calculate the maximum mass and minimum rotation periods (maximum frequencies) of neutron stars. Eventually, we compare a...
Institute of Scientific and Technical Information of China (English)
MIRZAEISEFAT Sina; FERNANDES Antonio Carlos
2013-01-01
This work describes investigations performed on the interaction of uniform current and freely rotating plate about a fixed vertical axis. Fluttering and autorotation are two different motions that may occur during the flow induced rotation. The dimensional analysis proves that the motion in flow induced rotation motion is governed essentially by the dimensionless moment of inertia and Reynolds number. Certain combinations define the stability boundaries between fluttering and autorotation. Fluttering is oscillation of body about a vertical axis and the autorotation is a name given to the case when the body turns continuously about the vertical axis. First, the loads and moment coefficients are calculated by experiments and streamline theory for different angles of attack for a fixed flat plate. Then for dynamic case, a bifurcation diagram is presented based on experiments to classify different motion states of flow induced rotation. Finally, a dynamical model is proposed for stability analysis of flow induced rotation of a flat plate.
Five-Axis, Three-Magnetic-Bearing Dynamic Spin Rig
Morrison, Carlos R.; Provenza, Andrew; Kurkov, Anatole; Mehmed, Oral; Johnson, Dexter; Montague, Gerald; Duffy, Kirsten; Jansen, Ralph
2005-01-01
The Five-Axis, Three-Magnetic-Bearing Dynamic Spin Rig is an apparatus for vibration testing of turbomachine blades in a vacuum at rotational speeds from 0 to 40,000 rpm. This rig includes (1) a vertically oriented shaft on which is mounted an assembly comprising a rotor holding the blades to be tested, (2) two actively controlled heteropolar radial magnetic bearings at opposite ends of the shaft, and (3) an actively controlled magnetic thrust bearing at the upper end of the shaft. This rig is a more capable successor to a prior apparatus, denoted the Dynamic Spin Rig (DSR), that included a vertically oriented shaft with a mechanical thrust bearing at the upper end and a single actively controlled heteropolar radial magnetic bearing at the lower end.
Numerical modeling and preliminary validation of drag-based vertical axis wind turbine
Directory of Open Access Journals (Sweden)
Krysiński Tomasz
2015-03-01
Full Text Available The main purpose of this article is to verify and validate the mathematical description of the airflow around a wind turbine with vertical axis of rotation, which could be considered as representative for this type of devices. Mathematical modeling of the airflow around wind turbines in particular those with the vertical axis is a problematic matter due to the complex nature of this highly swirled flow. Moreover, it is turbulent flow accompanied by a rotation of the rotor and the dynamic boundary layer separation. In such conditions, the key aspects of the mathematical model are accurate turbulence description, definition of circular motion as well as accompanying effects like centrifugal force or the Coriolis force and parameters of spatial and temporal discretization. The paper presents the impact of the different simulation parameters on the obtained results of the wind turbine simulation. Analysed models have been validated against experimental data published in the literature.
An Experimental Investigation of Passive Variable-Pitch Vertical-Axis Ocean Current Turbine
Directory of Open Access Journals (Sweden)
Ridho Hantoro
2011-04-01
Full Text Available Vertical-axis hydrokinetic turbines with fixed pitch blades typically suffer from poor starting torque, low efficiency and shaking due to large fluctuations in both radial and tangential force with azimuth angle. Maximizing the turbine power output can be achieved only if the mechanism of generation of the hydrodynamic force on the blades is clearly identified and tools to design high-performance rotors are developed. This paper describes an initial experimental investigation to understand more of the performance on vertical-axis turbine related to the effect of fixed-pitch and passive variable-pitch application using airfoil NACA 0018. Comparative analysis according to aspects of rotation and tip speed ratios was discussed. Information regarding the changes of foil position in passive variable-pitch during rotation at a limited range of flow velocity variations test was obtained and analyzed.
Design and Development of a Solar Thermal Collector with Single Axis Solar Tracking Mechanism
Directory of Open Access Journals (Sweden)
Theebhan Mogana
2016-01-01
Full Text Available The solar energy is a source of energy that is abundant in Malaysia and can be easily harvested. However, because of the rotation of the Earth about its axis, it is impossible to harvest the solar energy to the maximum capacity if the solar thermal collector is placed fix to a certain angle. In this research, a solar thermal dish with single axis solar tracking mechanism that will rotate the dish according to the position of the sun in the sky is designed and developed, so that more solar rays can be reflected to a focal point and solar thermal energy can be harvested from the focal point. Data were collected for different weather conditions and performance of the solar thermal collector with a solar tracker were studied and compared with stationary solar thermal collector.
Comparison with Tilted Axis Cranking and particle rotor model for triaxial nuclei
Energy Technology Data Exchange (ETDEWEB)
Ohtsubo, Shin-ichi; Shimizu, Yoshifumi R. [Kyushu Univ., Fukuoka (Japan). Dept. of Physics
1998-03-01
An extension of the cranking model in such a way to allow a rotation axis to deviate from the principal axes of the deformed mean-field is a promising tool for the spectroscopic study of rapidly rotating nuclei. We have applied such a `Tilted Axis Cranking` (TAC) method to a simple system of one-quasiparticle coupled to a triaxial rotor and compared it with a particle-rotor coupling calculation in order to check whether the spin-orientation degrees of freedom can be well described within the mean-field approximation. The result shows that the TAC method gives a good approximation to observable quantities and it is a suitable method to understand the dynamical interplay between the collective and single-particle angular momenta. (author)
Modelling of convective heat and mass transfer in rotating flows
Shevchuk, Igor V
2016-01-01
This monograph presents results of the analytical and numerical modeling of convective heat and mass transfer in different rotating flows caused by (i) system rotation, (ii) swirl flows due to swirl generators, and (iii) surface curvature in turns and bends. Volume forces (i.e. centrifugal and Coriolis forces), which influence the flow pattern, emerge in all of these rotating flows. The main part of this work deals with rotating flows caused by system rotation, which includes several rotating-disk configurations and straight pipes rotating about a parallel axis. Swirl flows are studied in some of the configurations mentioned above. Curvilinear flows are investigated in different geometries of two-pass ribbed and smooth channels with 180° bends. The author demonstrates that the complex phenomena of fluid flow and convective heat transfer in rotating flows can be successfully simulated using not only the universal CFD methodology, but in certain cases by means of the integral methods, self-similar and analyt...
Differential rotation of the unstable nonlinear r-modes
Friedman, John L; Lockitch, Keith H
2016-01-01
At second order in perturbation theory, the $r$-modes of uniformly rotating stars include an axisymmetric part that can be identified with differential rotation of the background star. If one does not include radiation-reaction, the differential rotation is constant in time and has been computed by S\\'a. It has a gauge dependence associated with the family of time-independent perturbations that add differential rotation to the unperturbed equilibrium star: For stars with a barotropic equation of state, one can add to the time-independent second-order solution arbitrary differential rotation that is stratified on cylinders (that is a function of distance $\\varpi$ to the axis of rotation). We show here that the gravitational radiation-reaction force that drives the $r$-mode instability removes this gauge freedom: The expontially growing differential rotation of the unstable second-order $r$-mode is unique. We derive a general expression for this rotation law for Newtonian models and evaluate it explicitly for s...
Giant Faraday rotation of high-order plasmonic modes in graphene-covered nanowires
Kuzmin, Dmitry A; Shavrov, Vladimir G; Temnov, Vasily V
2016-01-01
Plasmonic Faraday rotation in nanowires manifests itself in the rotation of the spatial intensity distribution of high-order surface plasmon polariton (SPP) modes around the nanowire axis. Here we predict theoretically the giant Faraday rotation for SPP propagating on graphene-coated magneto-optically active nanowires. Upon the reversal of the external magnetic field pointing along the nanowire axis some high-order plasmonic modes may be rotated by up to ~ 100 degrees on scale of about 500 nm at mid-infrared frequencies. Tuning carrier concentration in graphene by chemical doping or gate voltage allows for controlling SPP-properties and notably the rotation angle of high-order azimuthal modes. Our results open the door to novel plasmonic applications ranging from nanowire-based Faraday isolators to the magnetic control in quantum-optical applications.
Ligament length patterns, strength, and rotational axes of the knee joint.
Trent, P S; Walker, P S; Wolf, B
1976-06-01
Using intact fresh specimens, the cruciate ligament lengths for positions of flexion and internal-external rotation were computed using a non-invasive technique; using photographic methods, the centers of transverse rotation on the tibia and the direction of the flexion axis were also obtained. The anterior cruciate was found to be particularly effective in restraining internal tibial rotation; the ability of the posterior cruciate to restrain external rotation, however, depended strongly on the transverse axis location. Ligament length changes during flexion were found to be small in the absence of rotary torque and anteroposterior forces. The average internal rotation occurring during flexion was 37 degrees, half of which took place during the first 15 degrees of flexion. Ultimate rupture strengths of approximately 60 kh for the cruciates were measured, with stiffnesses of 16 kg/mm.
Giant Faraday Rotation of High-Order Plasmonic Modes in Graphene-Covered Nanowires.
Kuzmin, Dmitry A; Bychkov, Igor V; Shavrov, Vladimir G; Temnov, Vasily V
2016-07-13
Plasmonic Faraday rotation in nanowires manifests itself in the rotation of the spatial intensity distribution of high-order surface plasmon polariton (SPP) modes around the nanowire axis. Here we predict theoretically the giant Faraday rotation for SPPs propagating on graphene-coated magneto-optically active nanowires. Upon the reversal of the external magnetic field pointing along the nanowire axis some high-order plasmonic modes may be rotated by up to ∼100° on the length scale of about 500 nm at mid-infrared frequencies. Tuning the carrier concentration in graphene by chemical doping or gate voltage allows for controlling SPP-properties and notably the rotation angle of high-order azimuthal modes. Our results open the door to novel plasmonic applications ranging from nanowire-based Faraday isolators to the magnetic control in quantum-optical applications.
Takehiro, S.; Sasaki, Y.; Hayashi, Y.-Y.; Yamada, M.
2013-12-01
We investigate generation mechanisms of differential rotation and angular momentum transport caused by Boussinesq thermal convection in a rotating spherical shell based on weakly nonlinear numerical calculations for various values of the Prandtl and Ekman numbers under a setup similar to the solar convection layer. When the Prandtl number is of order unity or less and the rotation rate of the system is small (the Ekman number is larger than O(10-2)), the structure of thermal convection is not governed by the Taylor-Proudman theorem; banana-type convection cells emerge which follow the spherical shell boundaries rather than the rotation axis. Due to the Coriolis effect, the velocity field associated with those types of convection cells accompanies the Reynolds stress which transports angular momentum from high-latitudes to the equatorial region horizontally, and equatorial prograde flows are produced. The surface and internal distributions of differential rotation realized in this regime are quite similar to those observed in the Sun with helioseismology. These results may suggest that we should apply larger values of the eddy diffusivities than those believed so far when we use a low resolution numerical model for thermal convection in the solar interior.
Rotating optical tubes for vertical transport of atoms
Al Rsheed, Anwar; Lyras, Andreas; Aldossary, Omar M.; Lembessis, Vassilis E.
2016-12-01
The classical dynamics of a cold atom trapped inside a vertical rotating helical optical tube (HOT) is investigated by taking also into account the gravitational field. The resulting equations of motion are solved numerically. The rotation of the HOT induces a vertical motion for an atom initially at rest. The motion is a result of the action of two inertial forces, namely, the centrifugal force and the Coriolis force. Both inertial forces force the atom to rotate in a direction opposite to that of the angular velocity of the HOT. The frequency and the turning points of the atom's global oscillation can be controlled by the value and the direction of the angular velocity of the HOT. However, at large values of the angular velocity of the HOT the atom can escape from the global oscillation and be transported along the axis of the HOT. In this case, the rotating HOT operates as an optical Archimedes' screw for atoms.
Rotating Optical Tubes: An Archimedes' Screw for Atoms
Rsheed, Anwar Al; Aldossary, Omar M; Lembessis, Vassilis E
2016-01-01
The classical dynamics of a cold atom trapped inside a vertical rotating helical optical tube (HOT) is investigated by taking also into account the gravitational field. The resulting equations of motion are solved numerically. The rotation induces a vertical motion for an atom initially at rest. The motion is a result of the action of two inertial forces, namely the centrifugal force and the Coriolis force. Both inertial forces force the atom to rotate in a direction opposite to that of the angular velocity of the HOT. The frequency and the turning points of the atom's global oscillation can be controlled by the value and the direction of the angular velocity of the HOT. However, at large values of the angular velocity of the HOT the atom can escape from the global oscillation and be transported along the axis of the HOT. In this case, the rotating HOT operates as an Optical Archimedes' Screw (OAS) for atoms.
Off-Axis Neutrino Scattering in GRB Central Engines
George, N D; McGhee, J M; Miller, W A; George, Nathan D.; Kheyfets, Arkady; Ghee, John M. Mc; Miller, Warner A.
2003-01-01
The search for an understanding of an energy source great enough to explain the gamma-ray burst (GRB) phenomena has attracted much attention from the astrophysical community since its discovery. In this paper we extend the work of K. Asano and T. Fukuyama, and J. D. Salmonson and J. R. Wilson, and analyze the off-axis contributions to the energy-momentum deposition rate (MDR) from the neutrino anti-neutrino collisions above a rotating black hole/thin accretion disk system. Our calculations are performed by imaging the accretion disk at a specified observer using the full geodesic equations, and calculating the cumulative MDR from the scattering of all pairs of neutrinos and anti-neutrinos arriving at the observer. Our results shed light on the beaming efficiency of GRB models of this kind. Although we confirm Asano and Fukuyama's conjecture as to the constancy of the beaming for small angles away from the axis; nevertheless, we find the dominant contribution to the MDR comes from near the surface of the disk ...
Institute of Scientific and Technical Information of China (English)
ZHAO Jun; GUAN Yingzi; QI Naiming
2006-01-01
The dynamic balance quality of a rotating object is an important factor to maintain the stability and accuracy for motion. The azimuth of the principal axis of inertia is a major sign of dynamic balance. A usual method is measuring moment of inertia matrix relative to some base coordinates on a rotary inertia machine so as to calculate the azimuth of principal axis of inertia. By using the measured unbalance results on the two trimmed planes on a vertical hard bearing double-plane dynamic balancing machine, the dimension and direction of couple unbalance can be found. An azimuth angle formula for the principal axis of inertia is derived and is solved by using unbalance quantities. The experiments indicate that method based on dynamic balancing measurement is proved rational and effective and has a fine precision.
Active Blade Pitch Control for Straight Bladed Darrieus Vertical Axis Wind Turbine of New Design
DEFF Research Database (Denmark)
Chougule, Prasad; Nielsen, Søren R.K.; Basu, Biswajit
2013-01-01
As Development of small vertical axis wind turbines (VAWT) for urban use is becoming an interesting topic both within industry and academia. However, there are few new designs of vertical axis turbines which are customized for building integration. These are getting importance because they operate...... at low rotational speed producing very less noise during operation, although these are less efficient than Horizontal Axis Wind Turbines (HAWT). The efficiency of a VAWT has been significantly improved by H-Darrieus VAWT design based on double airfoil technology as demonstrated by the authors...... multiple stream tube method is used to determine the performance of the H-Darrieus VAWT. The power coefficient is compared with that of a fixed pitch and a variable pitch double airfoil blade VAWT. It is demonstrated that an improvement in power coefficient by 20% is achieved and the turbine could start...
Effect of core--mantle and tidal torques on Mercury's spin axis orientation
Peale, Stanton J; Hauck,, Steven A; Solomon, Sean C
2014-01-01
The rotational evolution of Mercury's mantle and its core under conservative and dissipative torques is important for understanding the planet's spin state. Dissipation results from tides and viscous, magnetic and topographic core--mantle interactions. The dissipative core--mantle torques take the system to an equilibrium state wherein both spins are fixed in the frame precessing with the orbit, and in which the mantle and core are differentially rotating. This equilibrium exhibits a mantle spin axis that is offset from the Cassini state by larger amounts for weaker core--mantle coupling for all three dissipative core--mantle coupling mechanisms, and the spin axis of the core is separated farther from that of the mantle, leading to larger differential rotation. The relatively strong core--mantle coupling necessary to bring the mantle spin axis to its observed position close to the Cassini state is not obtained by any of the three dissipative core--mantle coupling mechanisms. For a hydrostatic ellipsoidal core...
Review of wind simulation methods for horizontal-axis wind turbine analysis
Powell, D. C.; Connell, J. R.
1986-06-01
This report reviews three reports on simulation of winds for use in wind turbine fatigue analysis. The three reports are presumed to represent the state of the art. The Purdue and Sandia methods simulate correlated wind data at two points rotating as on the rotor of a horizontal-axis wind turbine. The PNL method at present simulates only one point, which rotates either as on a horizontal-axis wind turbine blade or as on a vertical-axis wind turbine blade. The spectra of simulated data are presented from the Sandia and PNL models under comparable input conditions, and the energy calculated in the rotational spikes in the spectra by the two models is compared. Although agreement between the two methods is not impressive at this time, improvement of the Sandia and PNL methods is recommended as the best way to advance the state of the art. Physical deficiencies of the models are cited in the report and technical recommendations are made for improvement. The report also reviews two general methods for simulating single-point data, called the harmonic method and the white noise method. The harmonic method, which is the basis of all three specific methods reviewed, is recommended over the white noise method in simulating winds for wind turbine analysis.
Binzel, R. P.; Green, J. R.; Opal, C. B.
1986-01-01
Thomas et al. (1984) analyzed 14 Voyager 2 images of Saturn's satellite Hyperion and interpreted them to be consistent with a coherent (nonchaotic) rotation period of 13.1 days. This interpretation was criticized by Peale and Wisdom (1984), who argued that the low sampling frequency of Voyager data does not allow chaotic or nonchaotic rotation to be distinguished. New observations obtained with a higher sampling frequency are reported here which conclusively show that the 13.1 day period found by Thomas et al. was not due to coherent rotation.
Energy Technology Data Exchange (ETDEWEB)
Lorenci, V.A. de; Svaiter, N.F. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)
1996-11-01
It was investigated which mapping has to be used to compare measurements made in a rotating frame to those made in an inertial frame. Using a non-Galilean coordinate transformation, the creation-annihilation operators of a massive scalar field in the rotating frame are not the same as those of an inertial observer. This leads to a new vacuum state(a rotating vacuum) which is a superposition of positive and negative frequency Minkowski particles. Polarization effects in circular accelerators in the proper frame of the electron making a connection with the inertial frame point of view were analysed. 65 refs.
MOTION ERROR ESTIMATION OF5-AXIS MACHINING CENTER USING DBB METHOD
Institute of Scientific and Technical Information of China (English)
CHEN Huawei; ZHANG Dawei; TIAN Yanling; ICHIRO Hagiwara
2006-01-01
In order to estimate the motion errors of 5-axis machine center, the double ball bar (DBB)method is adopted to realize the diagnosis procedure. The motion error sources of rotary axes in 5-axis machining center comprise of the alignment error of rotary axes and the angular error due to various factors, e.g. the inclination of rotary axes. From sensitive viewpoints, each motion error is possible to have a particular sensitive direction in which deviation of DBB error trace arises from only some specific error sources. The model of the DBB error trace is established according to the spatial geometry theory. Accordingly, the sensitive direction of each motion error source is made clear through numerical simulation, which is used as the reference patterns for rotational error estimation.The estimation method is proposed to easily estimate the motion error sources of rotary axes in quantitative manner. To verify the proposed DBB method for rotational error estimation, the experimental tests are carried out on a 5-axis machining center M-400 (MORISEIKI). The effect of the mismatch of the DBB is also studied to guarantee the estimation accuracy. From the experimental data, it is noted that the proposed estimation method for 5-axis machining center is feasible and effective.
The Rotation of the halo of NGC 6822 from the radial velocities of carbon stars
Thompson, Graham P; Sibbons, Lisette F
2016-01-01
Using spectra taken with the AAOmega spectrograph, we measure the radial velocities of over 100 stars, many of which are intermediate age carbon stars, in the direction of the dwarf irregular galaxy NGC 6822. Kinematic analysis suggests that the carbon stars in the sample are associated with NGC 6822, and estimates of its radial velocity and galactic rotation are made from a star-by-star analysis of its carbon star population. We calculate a heliocentric radial velocity for NGC 6822 of $-51\\pm3$ \\kms\\ and show that the population rotates with a mean rotation speed of $11.2\\pm2.1$ \\kms\\ at a mean distance of 1.1 kpc from the galactic centre, about a rotation axis with a position angle of $26^\\circ\\pm13^\\circ$, as projected on the sky. This is close to the rotation axis of the HI gas disk and suggests that NGC 6822 is not a polar ring galaxy, but is dynamically closer to a late type galaxy. However, the rotation axis is not aligned with the minor axis of the AGB isodensity profiles and this remains a mystery.
DEFF Research Database (Denmark)
Primdahl, Fritz; Brauer, Peter; Merayo, José M.G.
2002-01-01
The reference coordinate axes of a magnetic vector field sensor are related to the instrument digital output vector (U) over bar by the calibration matrix C and the offset vector (O) over bar. In addition, this reference coordinate system must be related to (at least) two externally accessible...... optical or geometrical axes in order to be able to determine the precise orientation of the magnetic coordinate axes in an external reference system. Two methods for determining a reference axis in the sensor coordinates are discussed: (1) using a triaxial coil facility to measure the sensor orientation...... for two different positions, rotated about a fixed reference axis; (2) in the Earth's field the magnetometer sensor is rotated about a fixed axis into a number of (at least three) positions....
Axis of Zodiacal light Near Tropic Cancer
Nawar, S; Mikhail, J S; Morcos, A B; Ibrahim, Alhassan I
2014-01-01
The axis of zodiacal lights have been obtained in blue and yellow colors using photoelectric observations of zodiacal light. These observations have been carried out at Abu Simbel Site in Egypt, in October 1975. This site lies too near to the tropic of Cancer, at which the axis of the zodiacal light cone perpendiculars to the horizon. The results show that the plane of the zodiacal light is inclined to the normal by 1.59 degrees in blue color and 1.18 degrees in yellow color. This means that there is a slight variation in zodiacal light axis with wavelength, and the axis almost coincide with the ecliptic. The present results for blue color can be considered as the first one in the world near the tropic of Cancer.
Counter-Rotatable Fan Gas Turbine Engine with Axial Flow Positive Displacement Worm Gas Generator
Giffin, Rollin George (Inventor); Murrow, Kurt David (Inventor); Fakunle, Oladapo (Inventor)
2014-01-01
A counter-rotatable fan turbine engine includes a counter-rotatable fan section, a worm gas generator, and a low pressure turbine to power the counter-rotatable fan section. The low pressure turbine maybe counter-rotatable or have a single direction of rotation in which case it powers the counter-rotatable fan section through a gearbox. The gas generator has inner and outer bodies having offset inner and outer axes extending through first, second, and third sections of a core assembly. At least one of the bodies is rotatable about its axis. The inner and outer bodies have intermeshed inner and outer helical blades wound about the inner and outer axes and extending radially outwardly and inwardly respectively. The helical blades have first, second, and third twist slopes in the first, second, and third sections respectively. A combustor section extends through at least a portion of the second section.
Nonideal rotations in nuclear magnetic resonance: Estimation of coherence transfer leakage
Energy Technology Data Exchange (ETDEWEB)
Jerschow, Alexej [Materials Sciences Division, 11-D62, Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States); Chemistry Department, D62 Hildebrand, University of California at Berkeley, Berkeley, California 94720 (United States)
2000-07-15
When spherical tensors are rotated by certain angles, coherence transfer selection rules may apply. For example, a {pi} rotation cleanly inverts the coherence order. A {pi}/2 rotation of a T{sub 0}{sup 1} tensor creates only T{sub {+-}}{sub 1}{sup 1} tensors. In this work estimations are given for the coherence transfer leakage under the action of rotations with small errors in the rotation angle or axis. Although the theory is stated with particular applications to NMR (nuclear magnetic resonance) in mind it is equally applicable wherever nonideal rotations of spherical tensors are considered (e.g., quantum computing and relaxation theory). In NMR it is useful for the estimation of coherence transfer leakage, especially in pulse sequences with many n{pi} pulses. The results are also applicable to spinors and half-integer representations of the rotation group. (c) 2000 American Institute of Physics.
Lagrangian velocity auto-correlations in statistically-steady rotating turbulence
Del Castello, Lorenzo
2013-01-01
Lagrangian statistics of passive tracers in rotating turbulence is investigated by Particle Tracking Velocimetry. A confined and steadily-forced turbulent flow is subjected to five different rotation rates. The PDFs of the velocity components clearly reveal the anisotropy induced by background rotation. Although the statistical properties of the horizontal turbulent flow field are approximately isotropic, in agreement with previously reported results by van Bokhoven and coworkers [Phys. Fluids 21, 096601 (2009)], the velocity component parallel to the (vertical) rotation axis gets strongly reduced (compared to the horizontal ones) while the rotation is increased. The auto-correlation coefficients of all three components are progressively enhanced for increasing rotation rates, although the vertical one shows a tendency to decrease for slow rotation rates. The decorrelation is approximately exponential. Lagrangian data compare favourably with previously reported Eulerian data for horizontal velocity components...
Directory of Open Access Journals (Sweden)
Mahmoud Jabalameli
2016-04-01
Full Text Available Background: Evaluating the landmarks for rotation of the distal femur is a challenge for orthopedic surgeons. Although the posterior femoral condyle axis is a good landmark for surgeons, the surgical transepicondylar axis may be a better option with the help of preoperative CT scanning. The purpose of this study was to ascertain relationships among the axes’ guiding distal femur rotational alignment in preoperative CT scans of Iranian patients who were candidates for total knee arthroplasty and the effects of age, gender, and knee alignment on these relationships. Methods: One hundred and eight cases who were admitted to two university hospitals for total knee arthroplasty were included in this study. The rotation of the distal femur was evaluated using single axial CT images through the femoral epicondyle. Four lines were drawn digitally in this view: anatomical and surgical transepicondylar axes, posterior condylar axis and the Whiteside anteroposterior line. The alignment of the extremity was evaluated in the standing alignment view. Then the angles were measured along these lines and their relationship was evaluated. Results: The mean angle between the anatomical transepicondylar axis and posterior condylar axis and between the surgical transepicondylar axis and posterior condylar axis were 5.9 ± 1.6 degrees and 1.6±1.7 degrees respectively. The mean angle between the Whiteside’s anteroposterior line and the line perpendicular to the posterior condylar axis was 3.7±2.1 degrees. Significant differences existed between the two genders in these relationships. No significant correlation between the age of patients and angles of the distal femur was detected. The anatomical surgical transepicondylar axis was in 4.3 degrees external rotation in relation to the surgical transepicondylar axis. Conclusion: Preoperative CT scanning can help accurately determine rotational landmarks of the distal femur. If one of the reference axes cannot be
Field-free long-lived alignment of molecules in extreme rotational states
Milner, A A; Milner, V
2015-01-01
We introduce a new optical tool - a "two-dimensional optical centrifuge", capable of aligning molecules in extreme rotational states. Unlike the conventional centrifuge, which confines the molecules in the plane of their rotation, its two-dimensional version aligns the molecules along a well-defined axis, similarly to the effect of a single linearly polarized laser pulse, but at a much higher level of rotational excitation. The increased robustness of ultra-high rotational states with respect to collisions results in a longer life time of the created alignment in dense media, offering new possibilities for studying and utilizing aligned molecular ensembles under ambient conditions.
GAROS, an aeroelastic code for coupled fixed-rotating structures
Energy Technology Data Exchange (ETDEWEB)
Rees, M. [Aerodyn Energiestyseme GmbH, Rendsburg (Germany); Vollan, A. [Pilatus Flugzeugwerke, Stans (Switzerland)
1996-09-01
The GAROS (General Analysis of Rotating Structures) program system has been specially designed to calculate aeroelastic stability and dynamic response of horizontal axis wind energy converters. Nevertheless it is also suitable for the dynamic analysis of helicopter rotors and has been used in the analysis of car bodies taking account of rotating wheels. GAROS was developed over the last 17 years. In the following the mechanical and the aerodynamic model will be discussed in detail. A short overview of the solution methods for the equation of motion in time and frequency domain will ge given. After this one example for the FEM model of the rotor and tower will be discussed. (EG)
Lift of a rotating circular cylinder in unsteady flows
DEFF Research Database (Denmark)
Carstensen, Stefan; Mandviwalla, Xerxes; Vita, Luca
2012-01-01
A cylinder rotating in steady current experiences a lift known as the Magnus effect. In the present study the effect of waves on the Magnus effect has been investigated. This situation is experienced with the novel floating offshore vertical axis wind turbine (VAWT) concept called the DEEPWIND...... concept, which incorporates a rotating spar buoy and thereby utilizes seawater as a roller-bearing. The a priori assumption and the results suggest that the lift in waves, to a first approximation, may be represented by a formulation similar to the well-known Morison formulation. The force coefficients...
Numerical simulation of VAWT on the effects of rotation cylinder
Xing, Shuda; Cao, Yang; Ren, Fuji
2017-06-01
Based on Finite Element Analysis Method, studying on Vertical Axis Wind Turbine (VAWT) which is added rotating cylinder in front of its air foils, especially focusing on the analysis of NACA6 series air foils about variation of lift to drag ratio. Choosing the most suitable blades with rotary cylinder added on leading edge. Analysis indicates that the front rotating cylinders on the VAWT is benefit to lift rise and drag fall. The most suitable air foil whose design lift coefficient is 0.8, the blades relative thickness is 20%, and the optimistic tip speed ratio is about 7.
... cuff are common. They include tendinitis, bursitis, and injuries such as tears. Rotator cuff tendons can become ... cuff depends on age, health, how severe the injury is, and how long you've had the ...
Fractal Aggregation Under Rotation
Institute of Scientific and Technical Information of China (English)
WU Feng-Min; WU Li-Li; LU Hang-Jun; LI Qiao-Wen; YE Gao-Xiang
2004-01-01
By means of the Monte Carlo simulation, a fractal growth model is introduced to describe diffusion-limited aggregation (DLA) under rotation. Patterns which are different from the classical DLA model are observed and the fractal dimension of such clusters is calculated. It is found that the pattern of the clusters and their fractal dimension depend strongly on the rotation velocity of the diffusing particle. Our results indicate the transition from fractal to non-fractal behavior of growing cluster with increasing rotation velocity, i.e. for small enough angular velocity ω the fractal dimension decreases with increasing ω, but then, with increasing rotation velocity, the fractal dimension increases and the cluster becomes compact and tends to non-fractal.
Fractal Aggregation Under Rotation
Institute of Scientific and Technical Information of China (English)
WUFeng-Min; WULi-Li; LUHang-Jun; LIQiao-Wen; YEGao-Xiang
2004-01-01
By means of the Monte Carlo simulation, a fractal growth model is introduced to describe diffusion-limited aggregation (DLA) under rotation. Patterns which are different from the classical DLA model are observed and the fractal dimension of such clusters is calculated. It is found that the pattern of the clusters and their fractal dimension depend strongly on the rotation velocity of the diffusing particle. Our results indicate the transition from fractal to non-fractal behavior of growing cluster with increasing rotation velocity, i.e. for small enough angular velocity ω; thefractal dimension decreases with increasing ω;, but then, with increasing rotation velocity, the fractal dimension increases and the cluster becomes compact and tends to non-fractal.
Solar rotation gravitational moments
Directory of Open Access Journals (Sweden)
A. Ajabshirizadeh
2005-09-01
Full Text Available Gravitational multipole moments of the Sun are still poorly known. Theoretically, the difficulty is mainly due to the differential rotation for which the velocity rate varies both on the surface and with the depth. From an observational point of view, the multipole moments cannot be directly measured. However, recent progresses have been made proving the existence of a strong radial differential rotation in a thin layer near the solar surface (the leptocline. Applying the theory of rotating stars, we will first compute values of J2 and J4 taking into account the radial gradient of rotation, then we will compare these values with the existing ones, giving a more complete review. We will explain some astrophysical outcomes, mainly on the relativistic Post Newtonian parameters. Finally we will conclude by indicating how space experiments (balloon SDS flights, Golf NG, Beppi-Colombo, Gaia... will be essential to unambiguously determine these parameters.
UMAPRM: Uniformly sampling the medial axis
Yeh, Hsin-Yi Cindy
2014-05-01
© 2014 IEEE. Maintaining clearance, or distance from obstacles, is a vital component of successful motion planning algorithms. Maintaining high clearance often creates safer paths for robots. Contemporary sampling-based planning algorithms That utilize The medial axis, or The set of all points equidistant To Two or more obstacles, produce higher clearance paths. However, They are biased heavily Toward certain portions of The medial axis, sometimes ignoring parts critical To planning, e.g., specific Types of narrow passages. We introduce Uniform Medial Axis Probabilistic RoadMap (UMAPRM), a novel planning variant That generates samples uniformly on The medial axis of The free portion of C
Axis Offset Estimation of VLBI Telescopes
Krásná, Hana; Nickola, Marisa; Böhm, Johannes
2014-12-01
Axis offset models have to be applied for VLBI telescopes with pointing axes which do not intersect. In this work, we estimated the axis offsets for VLBI antennas in a global adjustment of suitable IVS 24-hour sessions (1984.0-2014.0) with the Vienna VLBI Software (VieVS). In particular, we focused on the two radio telescopes of the Hartebeesthoek Radio Astronomy Observatory (HartRAO) in South Africa. For the older 26-m telescope we compared the estimated axis offset values before (6699.2 ± 0.5 mm) and after (6707.3 ± 0.8 mm) the bearing repair in 2010. A comparison with axis offset estimates from other geodetic techniques, such as GNSS or conventional local survey, was made. The estimated axis offset for the newer 15-m telescope (1495.0 ± 3.4 mm) agrees with the estimated value from the GPS survey in 2007. Furthermore, we assessed the influence of differences in the axis offsets on the estimated geodetic parameters, such as station coordinates or Earth Orientation Parameters.
Sex differences in the HPA axis.
Goel, Nirupa; Workman, Joanna L; Lee, Tiffany T; Innala, Leyla; Viau, Victor
2014-07-01
The hypothalamic-pituitary-adrenal (HPA) axis is a major component of the systems that respond to stress, by coordinating the neuroendocrine and autonomic responses. Tightly controlled regulation of HPA responses is critical for maintaining mental and physical health, as hyper- and hypo-activity have been linked to disease states. A long history of research has revealed sex differences in numerous components of the HPA stress system and its responses, which may partially form the basis for sex disparities in disease development. Despite this, many studies use male subjects exclusively, while fewer reports involve females or provide direct sex comparisons. The purpose of this article is to present sex comparisons in the functional and molecular aspects of the HPA axis, through various phases of activity, including basal, acute stress, and chronic stress conditions. The HPA axis in females initiates more rapidly and produces a greater output of stress hormones. This review focuses on the interactions between the gonadal hormone system and the HPA axis as the key mediators of these sex differences, whereby androgens increase and estrogens decrease HPA activity in adulthood. In addition to the effects of gonadal hormones on the adult response, morphological impacts of hormone exposure during development are also involved in mediating sex differences. Additional systems impinging on the HPA axis that contribute to sex differences include the monoamine neurotransmitters norepinephrine and serotonin. Diverse signals originating from the brain and periphery are integrated to determine the level of HPA axis activity, and these signals are, in many cases, sex-specific.
Electromagnetic rotational actuation.
Energy Technology Data Exchange (ETDEWEB)
Hogan, Alexander Lee
2010-08-01
There are many applications that need a meso-scale rotational actuator. These applications have been left by the wayside because of the lack of actuation at this scale. Sandia National Laboratories has many unique fabrication technologies that could be used to create an electromagnetic actuator at this scale. There are also many designs to be explored. In this internship exploration of the designs and fabrications technologies to find an inexpensive design that can be used for prototyping the electromagnetic rotational actuator.
Rotational spectrum of phenylglycinol
Simão, Alcides; Peña, Isabel; Cabezas, Carlos; Alonso, José L.
2014-11-01
Solid samples of phenylglycinol were vaporized by laser ablation and investigated through rotational spectroscopy in a supersonic expansion using two different techniques: chirped pulse Fourier transform microwave spectroscopy and narrow band molecular beam Fourier transform microwave spectroscopy. One conformer, bearing an O-H···N and an N-H···π intramolecular hydrogen bonds, could be successfully identified by comparison of the experimental rotational and 14N nuclear quadruple coupling constants with those predicted theoretically.
Earth rotation and geodynamics
Bogusz Janusz; Brzezinski Aleksander; Kosek Wieslaw; Nastula Jolanta
2015-01-01
This paper presents the summary of research activities carried out in Poland in 2011-2014 in the field of Earth rotation and geodynamics by several Polish research institutions. It contains a summary of works on Earth rotation, including evaluation and prediction of its parameters and analysis of the related excitation data as well as research on associated geodynamic phenomena such as geocentre motion, global sea level change and hydrological processes. The second part of the paper deals wit...
Oliveira, L. A.; Pecheux, J.; Restivo, A. O.
1991-06-01
The rotating flow between coaxial disks in a radially confined geometry is studied by numerical integration of the full Navier-Stokes equations. The results indicate that both Batchelor's and Stewartson's flow structures can be observed near the axis of rotation, depending on what conditions are set at the peripheral boundary.
Multi-view autostereoscopic projection display using rotating screen.
Eldes, Osman; Akşit, Kaan; Urey, Hakan
2013-11-18
A new technique for multi-view autostereoscopic projection display is proposed, and demonstrated. The technique uses two mobile projectors, a rotating retro-reflective diffuser screen, and a head-tracking camera. As two dynamic viewing slits are created at the viewer's position, the slits can track the position of the eyes by rotating the screen. The display allows a viewer to move approximately 700 mm along the horizontal axis, and 500 mm along the vertical axis with an average crosstalk below 5 %. Two screen prototypes with different diffusers have been tried, and they provide luminance levels of 60 Cd/m2, and 160 Cd/m2 within the viewing field.
ΔI = 4 structure in superdeformed rotational band - deformation with C4v symmetry
Hamamoto, Ikuko; Mottelson, Ben
1995-01-01
The recent observation of "ΔI = 4 structure" (or, alternatively, we call it "ΔI = 2 staggering") in the rotational spectra of superdeformed nuclei suggests the occurrence of Y44 deformations in the nuclear shape with associated C4v point-symmetry for the rotational Hamiltonian. Requiring the axially symmetric terms to favour rotation about an axis that is perpendicular to the long axis of nuclear shape, we have studied the general class of Hamiltonians with such symmetry. The ΔI = 4 structure can indeed result from the tunnelling between the four equivalent minima that occur in the plane perpendicular to the superdeformation symmetry axis, but the occurrence of this effect is a subtle matter depending sensitively on the axially symmetric terms in the Hamiltonian. We also discuss the dependence of the phase and the amplitude of the ΔI = 2 staggering on parameters.
Electro-mechanical coupling of rotating 3D beams
Directory of Open Access Journals (Sweden)
Stoykov S.
2016-01-01
Full Text Available A rotating thin-walled beam with piezoelectric element is analysed. The beam is considered to vibrate in space, hence the longitudinal, transverse and torsional deformations are taken into account. The bending deformations of the beam are modelled by assuming Timoshenko's theory. Torsion is included by considering that the cross section rotates as a rigid body but can deform in longitudinal direction due to warping. The warping function is computed preliminary by the finite element method. The equation of motion is derived by the principle of virtual work and discretized in space by the Ritz method. Electro-mechanical coupling is included in the model by considering the internal electrical energy and the electric charge output. The piezo-electric constitutive relations are used in reduced form. The beam is assumed to rotate about a fixed axis with constant speed. The equation of motion is derived in rotating coordinate system, but the influence of the rotation of the coordinate system is taken into account through the inertia forces. Results in time domain are presented for different speeds of rotation and frequencies of vibration. The influence of the speed of rotation and of the frequency of vibration on the electrical output is presented and analysed.
Rotating superconductor magnet for producing rotating lobed magnetic field lines
Hilal, Sadek K.; Sampson, William B.; Leonard, Edward F.
1978-01-01
This invention provides a rotating superconductor magnet for producing a rotating lobed magnetic field, comprising a cryostat; a superconducting magnet in the cryostat having a collar for producing a lobed magnetic field having oppositely directed adjacent field lines; rotatable support means for selectively rotating the superconductor magnet; and means for energizing the superconductor magnet.
The dynamic rotation of Langer's lines on facial expression.
Bush, James; Ferguson, Mark W J; Mason, Tracey; McGrouther, Gus
2007-01-01
Karl Langer investigated directional variations in the mechanical and physical properties of skin [Gibson T. Editorial. Karl Langer (1819-1887) and his lines. Br J Plast Surg 1978;31:1-2]. He produced a series of diagrams depicting lines of cleavage in the skin [Langer K. On the anatomy and physiology of the skin I. The cleavability of the cutis. Br J Plast Surg 1978;31:3-8] and showed that the orientation of these lines coincided with the dominant axis of mechanical tension in the skin [Langer K. On the anatomy and physiology of the skin II. Skin tension. Br J Plast Surg 1978;31:93-106]. Previously these lines have been considered as a static feature. We set out to determine whether Langer's lines have a dynamic element and to define any rotation of the orientation of Langer's lines on the face with facial movement. One hundred and seventy-five naevi were excised from the face and neck of 72 volunteers using circular dermal punch biopsies. Prior to surgery a vertical line was marked on the skin through the centre of each naevus. After excision distortions of the resulting wounds were observed. The orientation of the long axis of each wound, in relation to the previously marked vertical line, was measured with a goniometer with the volunteer at rest and holding their face in five standardised facial expressions: mouth open, smiling, eyes tightly shut, frowning and eyebrows raised. The aim was to measure the orientation of the long axis of the wound with the face at rest and subsequent rotation of the wound with facial movement. After excision elliptical distortion was seen in 171 of the 175 wounds at rest. Twenty-nine wounds maintained the same orientation of distortion in all of the facial expressions. In the remaining wounds the long axis of the wound rotated by up to 90 degrees . The amount of rotation varied between sites (p>0.0001). We conclude that Langer's lines are not a static feature but are dynamic with rotation of up to 90 degrees . It is possible that
Rotating cylindrically symmetric Kaluza-Klein ﬂuid model
Indian Academy of Sciences (India)
Ramesh Tikekar; L K Patel
2000-09-01
Kaluza-Klein ﬁeld equations for stationary cylindrically symmetric ﬂuid models in standard Einstein theory are formulated and a set of physically viable solutions is reported. This set is believed to be the ﬁrst such Kaluza-Klein solutions and it includes the Kaluza-Klein counterpart of Davidson’s solution describing spacetime of a perfect ﬂuid in rigid rotation about a regular axis.
Optical Characterization of Deep-Space Object Rotation States
2014-09-01
Optical Characterization of Deep-Space Object Rotation States Doyle Hall 1 and Paul Kervin 2 1 Boeing LTS, Kihei, Maui, HI and Colorado Springs, CO...0646, OPS-14-6494) Cleared for Public Release (Release # 377ABW-2014-0646, OPS-14-6494) 3. Wallach, B., Somers, P. and Scott , R., “Determination of...Wallace, B., Somers, P., and Scott , R. L., “Determination of Spin Axis Orientation of Geosynchronous Objects Using Space-Based Sensors: An Initial
DEFF Research Database (Denmark)
Gebhardt, Cristian; Preidikman, Sergio; Massa, Julio C
2010-01-01
blades’, the drivetrain and the generator. The blades are the part of the turbine that touches energy in the wind and rotates about an axis. Extracting energy from the wind is typically accomplished by first mechanically converting the velocity of the wind into a rotational motion of the wind turbine...... by means of the rotor blades, and then converting the rotational energy of the rotor blades into electrical energy by using a generator. The amount of available energy which the wind transfers to the rotor depends on the mass density of the air, the sweep area of the rotor blades, and the wind speed......Due to increasing environmental concern, and approaching limits to fossil fuel consumption, green sources of energy are gaining interest. Among the several energy sources being explored, wind energy shows much promise in selected areas where the average wind speeds is high. Wind turbines are used...
Moment of Inertia Dependence of Vertical Axis Wind Turbines in Pulsating Winds
Directory of Open Access Journals (Sweden)
Yutaka Hara
2012-01-01
Full Text Available Vertical Axis Wind Turbines (VAWTs are unaffected by changes in wind direction, and they have a simple structure and the potential for high efficiency due to their lift driving force. However, VAWTs are affected by changes in wind speed, owing to effects originating from the moment of inertia. In this study, changes in the rotational speed of a small VAWT in pulsating wind, generated by an unsteady wind tunnel, are investigated by varying the wind cycle and amplitude parameters. It is shown that the responses observed experimentally agree with simulations based on torque characteristics obtained under steady rotational conditions. Additionally, a simple equation expressing the relationship between the rotational change width and amplitude of the pulsating wind is presented. The energy efficiency in a pulsating wind remains constant with changes in both the moment of inertia and the wind cycle; however, the energy efficiency decreases when the wind amplitude is large.
Did Adria rotate relative to Africa?
Directory of Open Access Journals (Sweden)
D. J. J. van Hinsbergen
2014-03-01
Full Text Available The first and foremost boundary condition for kinematic reconstructions of the Mediterranean region is the relative motion between Africa and Eurasia, constrained through reconstructions of the Atlantic Ocean. The Adria continental block is in a downgoing plate position relative to the strongly curved Central Mediterranean subduction-related orogens, and forms the foreland of the Apennines, Alps, Dinarides, and Albanides-Hellenides. It is connected to the African plate through the Ionian Basin, likely with lower Mesozoic oceanic lithosphere. If the relative motion of Adria vs. Africa is known, its position relative to Eurasia can be constrained through the plate circuit, and hard boundary conditions for the reconstruction of the complex kinematic history of the Mediterranean are obtained. Kinematic reconstructions for the Neogene motion of Adria vs. Africa interpreted from the Alps, and from Ionian Basin and its surroundings, however, lead to scenarios involving vertical axis rotation predictions ranging from ∼0 to 20° counterclockwise. Here, we provide six new paleomagnetic poles from Adria, derived from the Lower Cretaceous to Upper Miocene carbonatic units of the Apulian peninsula (southern Italy. These, in combination with published poles from the Po Plain (Italy, the Istria peninsula (Croatia, and the Gargano promontory (Italy, document a post-Eocene 9.5 ± 8.7° counterclockwise vertical axis rotation of Adria. This result provides no support for models invoking significant Africa–Adria rotation differences between the Early Cretaceous and Eocene. The Alpine and Ionian Basin end-member kinematic models are both permitted within the documented rotation range, yet are mutually exclusive. This apparent enigma can be solved only if one or more of the following conditions (requiring future research are satisfied: (i Neogene shortening in the western Alps has been significantly underestimated (by as much as 150 km; (ii Neogene extension in
An event database for rotational seismology
Salvermoser, Johannes; Hadziioannou, Celine; Hable, Sarah; Chow, Bryant; Krischer, Lion; Wassermann, Joachim; Igel, Heiner
2016-04-01
The ring laser sensor (G-ring) located at Wettzell, Germany, routinely observes earthquake-induced rotational ground motions around a vertical axis since its installation in 2003. Here we present results from a recently installed event database which is the first that will provide ring laser event data in an open access format. Based on the GCMT event catalogue and some search criteria, seismograms from the ring laser and the collocated broadband seismometer are extracted and processed. The ObsPy-based processing scheme generates plots showing waveform fits between rotation rate and transverse acceleration and extracts characteristic wavefield parameters such as peak ground motions, noise levels, Love wave phase velocities and waveform coherence. For each event, these parameters are stored in a text file (json dictionary) which is easily readable and accessible on the website. The database contains >10000 events starting in 2007 (Mw>4.5). It is updated daily and therefore provides recent events at a time lag of max. 24 hours. The user interface allows to filter events for epoch, magnitude, and source area, whereupon the events are displayed on a zoomable world map. We investigate how well the rotational motions are compatible with the expectations from the surface wave magnitude scale. In addition, the website offers some python source code examples for downloading and processing the openly accessible waveforms.
Vega is a rapidly rotating star
Peterson, D M; Pauls, T A; Armstrong, J T; Benson, J A; Gilbreath, G C; Hindsley, R B; Hutter, D J; Johnston, K J; Mozurkewich, D; Schmitt, H R
2006-01-01
Vega, the second brightest star in the northern hemisphere, serves as a primary spectral type standard. While its spectrum is dominated by broad hydrogen lines, the narrower lines of the heavy elements suggested slow to moderate rotation, giving confidence that the ground-based calibration of its visibile spectrum could be safely extrapolated into the ultraviolet and near-infrared (through atmosphere models), where it also serves as the primary photometric calibrator. But there have been problems: the star is too bright compared to its peers and it has unusually shaped absorption line profiles, leading some to suggest that it is a distorted, rapidly rotating star seen pole-on. Here we report optical interferometric observations of Vega which detect the asymmetric brightness distribution of the bright, slightly offset polar axis of a star rotating at 93% of breakup speed. In addition to explaining the unusual brightness and line shape pecularities, this result leads to the prediction of an excess of near-infra...
Directory of Open Access Journals (Sweden)
Mirjam Ebersbach
2016-10-01
Full Text Available Tracking objects that are hidden and then moved is a crucial ability related to object permanence, which develops across several stages in early childhood. In spatial rotation tasks, children observe a target object that is hidden in one of two or more containers before the containers are rotated around a fixed axis. Usually, 30-month-olds fail to find the hidden object after it was rotated by 180°. We examined whether visual discriminability of the containers improves 30-month-olds’ success in this task and whether children perform better after 90° than after 180° rotations. Two potential hiding containers with same or different colors were placed on a board that was rotated by 90° or 180° in a within-subjects design. Children (N = 29 performed above chance level in all four conditions. Their overall success in finding the object did not improve by differently colored containers. However, different colors prevented children from showing an inhibition bias in 90° rotations, that is, choosing the empty container more often when it was located close to them than when it was farther away: This bias emerged in the same colors condition but not in the different colors condition. Results are discussed in view of particular challenges that might facilitate or deteriorate spatial rotation tasks for young children.
Ebersbach, Mirjam; Nawroth, Christian
2016-01-01
Tracking objects that are hidden and then moved is a crucial ability related to object permanence, which develops across several stages in early childhood. In spatial rotation tasks, children observe a target object that is hidden in one of two or more containers before the containers are rotated around a fixed axis. Usually, 30-month-olds fail to find the hidden object after it was rotated by 180°. We examined whether visual discriminability of the containers improves 30-month-olds’ success in this task and whether children perform better after 90° than after 180° rotations. Two potential hiding containers with same or different colors were placed on a board that was rotated by 90° or 180° in a within-subjects design. Children (N = 29) performed above chance level in all four conditions. Their overall success in finding the object did not improve by differently colored containers. However, different colors prevented children from showing an inhibition bias in 90° rotations, that is, choosing the empty container more often when it was located close to them than when it was farther away: This bias emerged in the same colors condition but not in the different colors condition. Results are discussed in view of particular challenges that might facilitate or deteriorate spatial rotation tasks for young children. PMID:27812346
Sengupta, Tapan K.; Gullapalli, Atchyut
2016-11-01
Spinning cylinder rotating about its axis experiences a transverse force/lift, an account of this basic aerodynamic phenomenon is known as the Robins-Magnus effect in text books. Prandtl studied this flow by an inviscid irrotational model and postulated an upper limit of the lift experienced by the cylinder for a critical rotation rate. This non-dimensional rate is the ratio of oncoming free stream speed and the surface speed due to rotation. Prandtl predicted a maximum lift coefficient as CLmax = 4π for the critical rotation rate of two. In recent times, evidences show the violation of this upper limit, as in the experiments of Tokumaru and Dimotakis ["The lift of a cylinder executing rotary motions in a uniform flow," J. Fluid Mech. 255, 1-10 (1993)] and in the computed solution in Sengupta et al. ["Temporal flow instability for Magnus-robins effect at high rotation rates," J. Fluids Struct. 17, 941-953 (2003)]. In the latter reference, this was explained as the temporal instability affecting the flow at higher Reynolds number and rotation rates (>2). Here, we analyze the flow past a rotating cylinder at a super-critical rotation rate (=2.5) by the enstrophy-based proper orthogonal decomposition (POD) of direct simulation results. POD identifies the most energetic modes and helps flow field reconstruction by reduced number of modes. One of the motivations for the present study is to explain the shedding of puffs of vortices at low Reynolds number (Re = 60), for the high rotation rate, due to an instability originating in the vicinity of the cylinder, using the computed Navier-Stokes equation (NSE) from t = 0 to t = 300 following an impulsive start. This instability is also explained through the disturbance mechanical energy equation, which has been established earlier in Sengupta et al. ["Temporal flow instability for Magnus-robins effect at high rotation rates," J. Fluids Struct. 17, 941-953 (2003)].
Energy Technology Data Exchange (ETDEWEB)
Hale, L C; Wulff, T A
2004-06-28
The Aerotech model S-180-69-A, a brushless DC motor of slotless design, was selected as the B-axis drive for the Precision Optical Grinder and Lathe (POGAL). It is common knowledge that a slotless motor will have effectively no magnetic cogging and much less torque ripple than a traditional slot-type motor. It is logical to believe that the radial and axial forces generated between the rotor and stator would also be smaller for a slotless design. This is important when a frameless motor is directly coupled to the axis, as these forces directly influence the axis and affect its error motion. It is the purpose of this test to determine the radial and axial forces generated by the Aerotech motor and to estimate their effect on the error motion of the axis using a mathematical model of the hydrostatic bearing being designed for POGAL. The test results combined with a mathematical model of the POGAL B axis indicate that the directly coupled Aerotech motor will be quite acceptable. In the radial direction, the residual motor force, after subtracting out the one-cycle force, could cause sub nanometer level error motion at the tool point. The axial direction is not in a sensitive direction for turning.
Gehan, Charlotte; Michel, Eric
2016-01-01
Stellar oscillations give seismic information on the internal properties of stars. Red giants are targets of interest since they present mixed modes, which behave as pressure modes in the convective envelope and as gravity modes in the radiative core. Mixed modes thus directly probe red giant cores, and allow in particular the study of their mean core rotation. The high-quality data obtained by CoRoT and Kepler satellites represent an unprecedented perspective to obtain thousands of measurements of red giant core rotation, in order to improve our understanding of stellar physics in deep stellar interiors. We developed an automated method to obtain such core rotation measurements and validated it for stars on the red giant branch. In this work, we particularly focus on the specific application of this method to red giants having a rapid core rotation. They show complex spectra where it is tricky to disentangle rotational splittings from mixed-mode period spacings. We demonstrate that the method based on the id...
Čerňanský, Andrej
2016-04-01
The comparative vertebral morphology of the atlas-axis complex in cordyliforms, xantusiid and several skinks is studied here. These lizards are particularly interesting because of their different ecological adaptations and anti-predation strategies, where conformation ranges from the lizard-like body to a snake-like body. This transition to serpentiform morphology shows several evolutionary patterns in the atlas-axis complex: 1) the zygapophyseal articulations are lost in the early stage of the transition. In contrast to mammals, the atlas is more or less locked to the axis in lepidosaurs, but the absence of zygapophyseal articulation releases this locking for rotation. However despite its serpentiform morphology, Chamaesaura is different, in possessing this articulation; 2) the first intercentrum of Chamaesaura and Tetradactylus africanus (serpentiform grass-swimmers) is fully curved anteriorly, underlying the occipital condyle. While this limits ventral skull rotation beyond a certain angle, it locks the skull, which is a crucial adaptation for a sit-and-wait position in grassland habitats that needs to keep the head stabilized; and 3) in Acontias, most of the atlas articular surface with the occipital condyle is formed by the lateral aspect of the articulation area relative to the area located in the dorsal region of the slightly reduced intercentrum. A similar state occurs in amphisbaenians, most likely reflecting a fossorial lifestyle of the limbless lizards. Although Chamaesaura and Tetradactylus live sympatrically in grasslands, Chamaesaura differs in several ways in atlas-axis complex: for example, aforementioned presence of the atlas-axis zygapophyseal articulation, and long posterodorsal processes. Its occipital condyle protrudes further posteriorly, placing the atlas-axis complex further from the endocranium than in Tetradactylus. Hence, adaptation in the same niche, even among sister clades, can lead to different atlas-axis morphology due to different
Vibrations of rotating machinery
Matsushita, Osami; Kanki, Hiroshi; Kobayashi, Masao; Keogh, Patrick
2017-01-01
This book opens with an explanation of the vibrations of a single degree-of-freedom (dof) system for all beginners. Subsequently, vibration analysis of multi-dof systems is explained by modal analysis. Mode synthesis modeling is then introduced for system reduction, which aids understanding in a simplified manner of how complicated rotors behave. Rotor balancing techniques are offered for rigid and flexible rotors through several examples. Consideration of gyroscopic influences on the rotordynamics is then provided and vibration evaluation of a rotor-bearing system is emphasized in terms of forward and backward whirl rotor motions through eigenvalue (natural frequency and damping ratio) analysis. In addition to these rotordynamics concerning rotating shaft vibration measured in a stationary reference frame, blade vibrations are analyzed with Coriolis forces expressed in a rotating reference frame. Other phenomena that may be assessed in stationary and rotating reference frames include stability characteristic...
Chiral Rotational Spectroscopy
Cameron, Robert P; Barnett, Stephen M
2015-01-01
We introduce chiral rotational spectroscopy: a new technique that enables the determination of the individual optical activity polarisability components $G_{XX}'$, $G_{YY}'$, $G_{ZZ}'$, $A_{X,YZ}$, $A_{Y,ZX}$ and $A_{Z,XY}$ of chiral molecules, in a manner that reveals the enantiomeric constitution of a sample whilst yielding an incisive signal even for a racemate. Chiral rotational spectroscopy could find particular use in the analysis of molecules that are chiral by virtue of their isotopic constitution and molecules with multiple chiral centres. The principles that underpin chiral rotational spectroscopy can also be exploited in the search for molecular chirality in space, which, if found, may add weight to hypotheses that biological homochirality and indeed life itself are of cosmic origin.
Chiral rotational spectroscopy
Cameron, Robert P.; Götte, Jörg B.; Barnett, Stephen M.
2016-09-01
We introduce chiral rotational spectroscopy, a technique that enables the determination of the orientated optical activity pseudotensor components BX X, BY Y, and BZ Z of chiral molecules, in a manner that reveals the enantiomeric constitution of a sample and provides an incisive signal even for a racemate. Chiral rotational spectroscopy could find particular use in the analysis of molecules that are chiral solely by virtue of their isotopic constitution and molecules with multiple chiral centers. A basic design for a chiral rotational spectrometer together with a model of its functionality is given. Our proposed technique offers the more familiar polarizability components αX X, αY Y, and αZ Z as by-products, which could see it find use even for achiral molecules.
Dorbolo, Stephane; Adami, Nicolas; Grasp Team
2014-11-01
The motion of ice discs released at the surface of a thermalized bath was investigated. As observed in some rare events in the Nature, the discs start spinning spontaneously. The motor of this motion is the cooling of the water close to the ice disc. As the density of water is maximum at 4°C, a downwards flow is generated from the surface of the ice block to the bottom. This flow generates the rotation of the disc. The speed of rotation depends on the mass of the ice disc and on the temperature of the bath. A model has been constructed to study the influence of the temperature of the bath. Finally, ice discs were put on a metallic plate. Again, a spontaneous rotation was observed. FNRS is thanked for financial support.
DEFF Research Database (Denmark)
Tandrup, T; Gundersen, Hans Jørgen Gottlieb; Jensen, Eva B. Vedel
1997-01-01
The optical rotator is an unbiased, local stereological principle for estimation of cell volume and cell surface area in thick, transparent slabs, The underlying principle was first described in 1993 by Kieu Jensen (T. Microsc. 170, 45-51) who also derived an estimator of length, In this study we...... further discuss the methods derived from this principle and present two new local volume estimators. The optical rotator benefits from information obtained in all three dimensions in thick sections but avoids over-/ underprojection problems at the extremes of the cell. Using computer-assisted microscopes...... the extra measurements demand minimal extra effort and make this estimator even more efficient when it comes to estimation of individual cell size than many of the previous local estimators, We demonstrate the principle of the optical rotator in an example (the cells in the dorsal root ganglion of the rat...
Rotation of cometary meteoroids
Capek, David
2014-01-01
The aim of this study is to estimate the rotational characteristics of meteoroids after their release from a comet during normal activity. The results can serve as initial conditions for further analyses of subsequent evolution of rotation in the interplanetary space. A sophisticated numerical model was applied to meteoroids ejected from 2P/Encke comet. The meteoroid shapes were approximated by polyhedrons with several thousands of surface elements, which have been determined by 3D laser scanning method of 36 terrestrial rock samples. These samples came from three distinct sets with different origin and shape characteristics. Two types of gas-meteoroid interactions (diffuse and specular reflection of gas molecules from the surface of meteoroid) and three gas ejection models (leading to very different ejection velocities) were assumed. The rotational characteristics of ejected meteoroid population were obtained by numerical integration of equations of motion with random initial conditions and random shape sele...
Diffuser Augmented Horizontal Axis Tidal Current Turbines
Directory of Open Access Journals (Sweden)
Nasir Mehmood
2012-09-01
Full Text Available The renewal energy technologies are increasingly popular to ensure future energy sustenance and address environmental issues. The tides are enormous and consistent untapped resource of renewable energy. The growing interest in exploring tidal energy has compelling reasons such as security and diversity of supply, intermittent but predictable and limited social and environmental impacts. The tidal energy industry is undergoing an increasing shift towards diffuser augmented turbines. The reason is the higher power output of diffuser augmented turbines compared to conventional open turbines. The purpose of this study is to present a comprehensive review of diffuser augmented horizontal axis tidal current turbines. The components, relative advantages, limitations and design parameters of diffuser augmented horizontal axis tidal current turbines are presented in detail. CFD simulation of NACA 0016 airfoil is carried out to explore its potential for designing a diffuser. The core issues associated with diffuser augmented horizontal axis tidal current turbines are also discussed.
Modular off-axis solar concentrator
Energy Technology Data Exchange (ETDEWEB)
Plesniak, Adam P; Hall, John C
2015-01-27
A solar concentrator including a housing defining a vertical axis and including a receiving wall connected to a reflecting wall to define an internal volume and an opening into the internal volume, wherein the reflecting wall defines at least one primary optical element, and wherein at least a portion of the reflecting wall includes a layer of reflective material, the housing further including a cover connected to the receiving wall and the reflecting wall to seal the opening, and at least one receiver mounted on the receiving wall such that a vertical axis of the receiver is disposed at a non-zero angle relative to the vertical axis of the housing, the receiver including at least one photovoltaic cell.
Oxytocin and hypothalamo-pituitary- adrenal axis
Directory of Open Access Journals (Sweden)
Berrak Ç. Yeğen
2010-05-01
Full Text Available BSTRACT: Upon exposure to different types of stressors, neuroendocrine and behavioral responses that include the activation of the hypothalamus-pituitary-adrenal (HPA axis are given to allow the individuals to cope with stress conditions. It was proven that oxytocin, anonapeptide released from the posterior pituitary, has behavioral and stress-attenuating effects by dampening HPA activity. On the other hand, the neuropeptide was also shown to exert anti-inflammatory effects through the modulation of immune and inflammatory processes in several experimental models of tissue injury. The findings of recent studies suggest that the anti-inflammatory effect of oxytocin depends on its role on HPA axis activity and subsequent release of cortisol. Thus, oxytocin seems to restrain the activity within the HPA-axis, which becomes overactive during many inflammatory processes
New Urban Vertical Axis Wind Turbine Design
Directory of Open Access Journals (Sweden)
Alexandru-Mihai CISMILIANU
2015-12-01
Full Text Available This paper develops a different approach for enhancing the performance of Vertical Axis Wind Turbines for the use in the urban or rural environment and remote isolated residential areas. Recently the vertical axis wind turbines (VAWT have become more attractive due to the major advantages of this type of turbines in comparison to the horizontal axis wind turbines. We aim to enhance the overall performance of the VAWT by adding a second set of blades (3 x 2=6 blades following the rules of biplane airplanes. The model has been made to operate at a maximum power in the range of the TSR between 2 to 2.5. The performances of the VAWT were investigated numerically and experimentally and justify the new proposed design.
Direction of spin axis and spin rate of the pitched baseball.
Jinji, Tsutomu; Sakurai, Shinji
2006-07-01
In this study, we aimed to determine the direction of the spin axis and the spin rate of pitched baseballs and to estimate the associated aerodynamic forces. In addition, the effects of the spin axis direction and spin rate on the trajectory of a pitched baseball were evaluated. The trajectories of baseballs pitched by both a pitcher and a pitching machine were recorded using four synchronized video cameras (60 Hz) and were analyzed using direct linear transform (DLT) procedures. A polynomial function using the least squares method was used to derive the time-displacement relationship of the ball coordinates during flight for each pitch. The baseball was filmed immediately after ball release using a high-speed video camera (250 Hz), and the direction of the spin axis and the spin rate (omega) were calculated based on the positional changes of the marks on the ball. The lift coefficient was correlated closely with omegasinalpha (r = 0.860), where alpha is the angle between the spin axis and the pitching direction. The term omegasinalpha represents the vertical component of the velocity vector. The lift force, which is a result of the Magnus effect occurring because of the rotation of the ball, acts perpendicularly to the axis of rotation. The Magnus effect was found to be greatest when the angular and translational velocity vectors were perpendicular to each other, and the break of the pitched baseball became smaller as the angle between these vectors approached 0 degrees. Balls delivered from a pitching machine broke more than actual pitcher's balls. It is necessary to consider the differences when we use pitching machines in batting practice.
A users guide to HPA axis research.
Spencer, Robert L; Deak, Terrence
2016-11-18
Glucocorticoid hormones (cortisol and corticosterone - CORT) are the effector hormones of the hypothalamic-pituitary-adrenal (HPA) axis neuroendocrine system. CORT is a systemic intercellular signal whose level predictably varies with time of day and dynamically increases with environmental and psychological stressors. This hormonal signal is utilized by virtually every cell and physiological system of the body to optimize performance according to circadian, environmental and physiological demands. Disturbances in normal HPA axis activity profiles are associated with a wide variety of physiological and mental health disorders. Despite numerous studies to date that have identified molecular, cellular and systems-level glucocorticoid actions, new glucocorticoid actions and clinical status associations continue to be revealed at a brisk pace in the scientific literature. However, the breadth of investigators working in this area poses distinct challenges in ensuring common practices across investigators, and a full appreciation for the complexity of a system that is often reduced to a single dependent measure. This Users Guide is intended to provide a fundamental overview of conceptual, technical and practical knowledge that will assist individuals who engage in and evaluate HPA axis research. We begin with examination of the anatomical and hormonal components of the HPA axis and their physiological range of operation. We then examine strategies and best practices for systematic manipulation and accurate measurement of HPA axis activity. We feature use of experimental methods that will assist with better understanding of CORT's physiological actions, especially as those actions impact subsequent brain function. This research approach is instrumental for determining the mechanisms by which alterations of HPA axis function may contribute to pathophysiology.
Chernodub, M N
2012-01-01
Recently, we have demonstrated that for a certain class of Casimir-type systems ("devices") the energy of zero-point vacuum fluctuations reaches its global minimum when the device rotates about certain axis rather than remains static. This rotational vacuum effect may lead to emergence of permanently rotating objects - philosophically similar to "time crystals" proposed recently by Shapere and Wilczek in classical and quantum mechanical systems - provided the negative rotational energy of zero-point fluctuations cancels the positive rotational energy of the device itself. In this paper we show that for massless electrically charged particles the rotational vacuum effect should be drastically (astronomically) enhanced in the presence of magnetic field. As an illustration, we show that in a background of experimentally available magnetic fields the zero-point energy of massless excitations in rotating torus-shaped doped carbon nanotubes may indeed overwhelm the classical energy of rotation for certain angular f...
High accuracy NURBS interpolation for five-axis machine of table-rotating/spindle-tilting type
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
In this paper, the definition of NURBS curve and a speed-controlled interpolation in which the feed rate is automatically adjusted in order to meet the specified chord error limit were discussed. Besides those, a definition of linear interpolation error of post-processed data was proposed, which should be paid more attention to because it will not only reduce quality of the surface but also may cause interference and other unexpected trouble. In order to control the error, a robust algorithm was proposed, which successfully met a desired error limit through interpolating some essential CL data. The excellence of the proposed algorithm, in terms of its reliability and self-adaptiveness, has been proved by simulation results.
High accuracy NURBS interpolation for five-axis machine of table-rotating/spindle-tilting type
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
In this paper, the definition of NURBS curve and a speed-controlled interpolation in which the feed rate is automatically adjusted in order to meet the specified chord error limit were discussed. Besides those, a definition of linear interpolation error of post-processed data was proposed, which should be paid more attention to because it will not only reduce quality of the surface but also may cause interference and other unexpected trouble. In order to control the error, a robust algorithm was proposed, w...
ship propulsion and cycloidal ship propulsion . Approximately 1200 references are listed. A series of cross-index tables is also included to provide a quick means for the reader to determine the content and availability of the references. An analysis of the various lift systems pertinent to the HARWAS field is made with a view to potential air vehicle applications. Over 20 original aeronautical applications are identified and evaluated in the light of recent advances in power plants, transmissions and lightweight structural techniques. This analysis
Alignment Solution for CT Image Reconstruction by Fixed Point and Virtual Rotation Axis
Jun, Kyungtaek; Kwon, Kyu
2016-01-01
Since X-ray tomography is now widely adopted in many different areas, it becomes more crucial to find a robust routine of handling tomographic data to get quality reconstructed images. Though there are several existing techniques, it seems helpful to have a more automated method to remove the possible errors that hinder clearer image reconstruction. Here, we proposed an alternative method and new algorithm using the sinogram and the fixed point. A new physical concept of Center of Attenuation (CA) was also introduced to figure out how this fixed point is applied to the image reconstruction with errors we further categorized. Our technique showed a promising performance in restoring images with translation and vertical tilt errors.
On the rotation and pitching of flat plates
Jin, Yaqing; Ji, Sheng; Chamorro, Leonardo P.
2016-11-01
Wind tunnel experiments were performed to characterize the flow-induced rotation and pitching of various flat plates as a function of the thickness ratio, the location of the axis of rotation and turbulence levels. High-resolution telemetry, laser tachometer, and hotwire were used to get time series of the plates motions and the signature of the wake flow at a specific location. Results show that a minor axis offset can induce high-order modes in the plate rotation under low turbulence due to torque unbalance. The spectral decomposition of the flow velocity in the plate wake reveals the existence of a dominating high-frequency mode that corresponds to a static-like vortex shedding occurring at the maximum plate pitch, where the characteristic length scale is the projected width at maximum pitch. The plate thickness ratio shows inverse relation with the angular velocity. A simple model is derived to explain the linear relation between pitching frequency and wind speed. The spectra of the plate rotation show nonlinear relation with the incoming turbulence, and the dominating role of the generated vortices in the plate motions.
Solar polar rotation and its effect on heliospheric neutral fluxes
Sokol, J. M.; Grzedzielski, S.; Bzowski, M.
2016-12-01
The magnetic field in the solar polar corona exhibit a regular "ray-like" structure associated with large polar coronal holes during solar minimum. The solar rotation twists the magnetic field lines of the expanding fast solar wind over the poles. The twist induces a toroidal component of the polar magnetic field which results in magnetic forces directed towards the rotation axis. That is tantamount to a (weak) zeta pinch, known also in other astrophysical contexts (e.g. AGN plasmas). The pinch compresses the polar solar corona plasma and a cone-like enhancement in the solar wind density forms along the rotation axis. Though the effect is likely very dynamic, a time independent description is used here to get an order-of-magnitude estimate. The weak pinch is treated as a 1st order perturbation to the zero-order radial flow. The obtained density enhancement may affect the near and far heliosphere, modifying the charge-exchange and electron impact ionization rates of neutral atoms in interplanetary space. The charge exchange is the most effective ionization process for hydrogen and oxygen atoms, and electron impact ionization is a significant loss reaction for the helium atoms at close distances to the Sun. The change in the polar density due to the solar polar corona rotation could be of importance in the inner heliosphere for low energy atoms. We will present the influence of this effect on interstellar neutral gas distribution and H ENA fluxes observed by IBEX.
Component rotation and anterior knee pain after total knee arthroplasty.
Barrack, R L; Schrader, T; Bertot, A J; Wolfe, M W; Myers, L
2001-11-01
All patients undergoing cruciate-retaining primary total knee arthroplasty for degenerative osteoarthritis at one center were studied prospectively. Clinical and radiographic followup was obtained at a minimum 5 years in 102 knees in 73 patients. Patients were asked specifically about the presence of the pain in the anterior aspect of the knee in the vicinity of the patella and rated the severity of the pain on a visual analog scale. Significant anterior knee pain rating at least 3 of 10 on the visual analog scale was present in 16 knees (13 patients). Eleven patients with 14 symptomatic knees agreed to undergo computed tomography scanning to accurately determine the rotation of the tibial and femoral components. The epicondylar axis and tibial tubercle were used as references using a previously validated technique. A control group of 11 asymptomatic patients (14 knees), matched for age, gender, and length of followup also underwent computed tomography scanning. All patients in both groups had normal axial alignment. There was a highly significant difference in tibial component rotation between the two groups with the patients with anterior knee pain averaging 6.2 degrees internal rotation compared with 0.4 degrees external rotation in the control group. There also was a significant difference in combined component rotation with the patients with anterior knee pain averaging 4.7 degrees internal rotation compared with 2.6 degrees external rotation in the control group. There was no significant difference in the degree of radiographic patellar tilt or patellar subluxation between the two groups. Patients with combined component internal rotation were more than five times as likely to experience anterior knee pain after total knee arthroplasty compared with those with combined component external rotation. Component malrotation is a significant factor in the development of anterior knee pain after total knee arthroplasty.
Effect of rotation on a rotating hot-wire sensor
Hah, C.; Lakshminarayana, B.
1978-01-01
An investigation was conducted to discern the effects of centrifugal and Coriolis forces on a rotating hot-wire. The probe was calibrated in a wind tunnel as well as in a rotating mode. The effect of rotation was found to be negligibly small. A small change in cold resistance (1.5%) was observed in the rotating wire. The rotation seems to have a negligible effect on the fluid mechanics, heat transfer and material characteristics of the wire. This is a significant conclusion in view of the potential application of the hot-wire probe in a rotating passage (such as turbomachinery).
Rotational stabilization of q < 1 modes
Energy Technology Data Exchange (ETDEWEB)
Waelbroeck, F.L.; Aydemir, A.Y. [Univ. of Texas, Austin, TX (United States)
1996-12-31
Analyses of high performance discharges with central safety factor below unity have shown that the ideal Magnetohydrodynamic stability threshold for the n=1 kink mode is often violated with impunity. For TFTR (Tokamak Fusion Test Reactor) supershots, the experimental observations can be explained by diamagnetic stabilization of the reconnecting model provided that the fluid free energy is suitably reduced by trapped particle effects. For the broader profiles typical of other high confinement regimes, however, diamagnetic effects cannot account for the experimental results. Furthermore, there is evidence that the Mercier stability condition can also be violated in some cases. Here, we show that toroidal rotation of the plasma can stabilize the kink mode even in the presence of resistivity in configurations that would otherwise be ideally unstable. Two effects can be distinguished. The first effect consists in a reduction of the ideal driving energy. This can be understood in view of the fact that, to a good approximation, the internal kink is a rigid body displacement combining a tilt of the plasma inside the q = 1 surface with a translation along the tilt axis. In the presence of rotation, this displacement must be accompanied by a precessional motion so as to conserve angular momentum. The kinetic energy of the precessional motion must be extracted from the energy driving the displacement. The second effect of rotation is to resolve the Alfven singularity. This is a consequence of the pressure perturbation caused by the equilibrium variation of the entropy within the flux surfaces. It results in the stabilization of resistive as well as weak ideal instabilities, including Mercier modes. For rotationally stabilized equilibria, it also implies the presence of a neutrally stable mode with frequency of the order of the growth rate of the internal kink.
Differential rotation of stretched and twisted thick magnetic flux tube dynamos in Riemannian spaces
de Andrade, Garcia
2007-01-01
The topological mapping between a torus of big radius and a sphere is applied to the Riemannian geometry of a stretched and twisted very thick magnetic flux tube, to obtain spherical dynamos solving the magnetohydrodynamics (MHD) self-induction equation for the magnetic flux tubes undergoing differential (non-uniform) rotation along the tube magnetic axis. Constraints on the shear is also computed. It is shown that when the hypothesis of the convective cyclonic dynamo is used the rotation is ...
Molecular collisions. 11: Semiclassical approximation to atom-symmetric top rotational excitation
Russell, D.; Curtiss, C. F.
1973-01-01
In a paper of this series a distorted wave approximation to the T matrix for atom-symmetric top scattering was developed which is correct to first order in the part of the interaction potential responsible for transitions in the component of rotational angular momentum along the symmetry axis of the top. A semiclassical expression for this T matrix is derived by assuming large values of orbital and rotational angular momentum quantum numbers.
DRIVE AND CONTROL OF VIRTUAL-AXIS NC MACHINE TOOLS
Institute of Scientific and Technical Information of China (English)
无
1999-01-01
The structure features and driving modes of virtual-axis NC machine tools are studied.Accor- ding to different application requirements,the three-axis control method,the five-axis control method and the six-freedom control method are put forward.These results lay a foundation for the product development of the virtual-axis NC machine tools.
2013-01-01
Position-dependent geometric errors, or “error map, ” of a rotary axis represent how position and orientation of the axis of rotation change with its rotation. This paper proposes a scheme to calibrate the error map of rotary axes by on-the-machine measurement of test pieces by using a contact-type touch-trigger probe installed on the machine's spindle. The present scheme enables more efficient and automated error calibration, which is crucial to implement periodic check of rotary axes error ...
Schache, Anthony G; Baker, Richard; Lamoreux, Larry W
2006-08-01
Minimising measurement variability associated with hip axial rotation and avoiding knee joint angle cross-talk are two fundamental objectives of any method used to define the knee joint flexion-extension axis for purposes of quantitative gait analysis. The aim of this experiment was to compare three different methods of defining this axis: the knee alignment device (KAD) method, a method based on the transepicondylar axis (TEA) and an alternative numerical method (Dynamic). The former two methods are common approaches that have been applied clinically in many quantitative gait analysis laboratories; the latter is an optimisation procedure. A cohort of 20 subjects performed three different functional tasks (normal gait; squat; non-weight bearing knee flexion) on repeated occasions. Three-dimensional hip and knee angles were computed using the three alternative methods of defining the knee joint flexion-extension axis. The repeatability of hip axial rotation measurements during normal gait was found to be significantly better for the Dynamic method (pknee varus-valgus kinematic profile and the degree of knee joint angle cross-talk were smallest for the Dynamic method across all functional tasks. The Dynamic method therefore provided superior results in comparison to the KAD and TEA-based methods and thus represents an attractive solution for orientating the knee joint flexion-extension axis for purposes of quantitative gait analysis.
The implications of particle rotation on the effect of photophoresis
van Eymeren, Janine
2011-01-01
In a laboratory experiment, water-ice aggregates are trapped in a vacuum chamber at a pressure of 2 mbar due to photophoresis and thermophoresis. The particles are located between a Peltier element at the bottom at 250 K and a reservoir of liquid nitrogen at the top at 77 K. Particle sizes vary between 20 micrometres and a few hundred micrometres. It is found that 95% of all the particles rotate about their vertical axis. A qualitative model is developed which explains why particles should mainly align to and rotate around the vertical. The results imply that rotation does not decrease the vertical strength of photophoretically driven motion in, e.g., protoplanetary discs.
Possible Reasons for the Slow Rotation of BF Ori
Shulman, S. G.
2016-03-01
Possible reasons for the very low projected rotation velocity of BF Ori compared to other UX Ori stars are discussed. The hypothesis of a close companion that slows down the star's rotation by a tidal interaction is examined. Based on a theory of synchronization and modern models of evolution, the interaction is calculated numerically for different masses of the companion and values of the semi-major axis. It is shown that in order to obtain the projected velocity observed for BF Ori, the companion must have a mass greater than 0.5M⊙ . Such a large companion should have been discovered observationally. It is suggested that the low rotation velocity of BF Ori is more likely to be related to the distribution of the angular momentum of a protostellar cloud between the angular momentum of the star and the orbital angular momentum of a low-mass companion.
DEFF Research Database (Denmark)
Rasmusson, Allan
2009-01-01
The inherent demand for unbiasedness for some stereological estimators imposes a demand of not only positional uniform randomness but also isotropic randomness, i.e. directional uniform randomness. In order to comply with isotropy, one must perform a random rotation of the object of interest befo...
Connors, G. Patrick
Many baseball players suffer from shoulder injuries related to the rotator cuff muscles. These injuries may be classified as muscular strain, tendonitis or tenosynovitis, and impingement syndrome. Treatment varies from simple rest to surgery, so it is important to be seen by a physician as soon as possible. In order to prevent these injuries, the…
Connors, G. Patrick
Many baseball players suffer from shoulder injuries related to the rotator cuff muscles. These injuries may be classified as muscular strain, tendonitis or tenosynovitis, and impingement syndrome. Treatment varies from simple rest to surgery, so it is important to be seen by a physician as soon as possible. In order to prevent these injuries, the…
Compact rotating cup anemometer
Wellman, J. B.
1968-01-01
Compact, collapsible rotating cup anemometer is used in remote locations where portability and durability are factors in the choice of equipment. This lightweight instrument has a low wind-velocity threshold, is capable of withstanding large mechanical shocks while in its stowed configuration, and has fast response to wind fluctuations.
Davies, Paul Charles William; Manogue, C A; Davies, Paul C W; Dray, Tevian; Manogue, Corinne A
1996-01-01
We derive conditions for rotating particle detectors to respond in a variety of bounded spacetimes and compare the results with the folklore that particle detectors do not respond in the vacuum state appropriate to their motion. Applications involving possible violations of the second law of thermodynamics are briefly addressed.
Rotationally Actuated Prosthetic Hand
Norton, William E.; Belcher, Jewell G., Jr.; Carden, James R.; Vest, Thomas W.
1991-01-01
Prosthetic hand attached to end of remaining part of forearm and to upper arm just above elbow. Pincerlike fingers pushed apart to degree depending on rotation of forearm. Simpler in design, simpler to operate, weighs less, and takes up less space.
Galaxy rotation and supermassive black hole binary evolution
Mirza, M. A.; Tahir, A.; Khan, F. M.; Holley-Bockelmann, H.; Baig, A. M.; Berczik, P.; Chishtie, F.
2017-09-01
Supermassive black hole (SMBH) binaries residing at the core of merging galaxies are recently found to be strongly affected by the rotation of their host galaxies. The highly eccentric orbits that form when the host is counterrotating emit strong bursts of gravitational waves that propel rapid SMBH binary coalescence. Most prior work, however, focused on planar orbits and a uniform rotation profile, an unlikely interaction configuration. However, the coupling between rotation and SMBH binary evolution appears to be such a strong dynamical process that it warrants further investigation. This study uses direct N-body simulations to isolate the effect of galaxy rotation in more realistic interactions. In particular, we systematically vary the SMBH orbital plane with respect to the galaxy rotation axis, the radial extent of the rotating component, and the initial eccentricity of the SMBH binary orbit. We find that the initial orbital plane orientation and eccentricity alone can change the inspiral time by an order of magnitude. Because SMBH binary inspiral and merger is such a loud gravitational wave source, these studies are critical for the future gravitational wave detector, Laser Interferometer Space Antenna, an ESA/NASA mission currently set to launch by 2034.
Direct imaging of rotating molecules anchored on graphene
Choe, Jeongheon; Lee, Yangjin; Fang, Lei; Lee, Gun-Do; Bao, Zhenan; Kim, Kwanpyo
2016-07-01
There has been significant research interest in controlling and imaging molecular dynamics, such as translational and rotational motions, especially at a single molecular level. Here we applied aberration-corrected transmission electron microscopy (ACTEM) to actuate and directly image the rotational motions of molecules anchored on a single-layer-graphene sheet. Nanometer-sized carbonaceous molecules anchored on graphene provide ideal systems for monitoring rotational motions via ACTEM. We observed the preferential registry of longer molecular axis along graphene zigzag or armchair lattice directions due to the stacking-dependent molecule-graphene energy landscape. The calculated cross section from elastic scattering theory was used to experimentally estimate the rotational energy barriers of molecules on graphene. The observed energy barrier was within the range of 1.5-12 meV per atom, which is in good agreement with previous calculation results. We also performed molecular dynamics simulations, which revealed that the edge atoms of the molecule form stably bonds to graphene defects and can serve as a pivot point for rotational dynamics. Our study demonstrates the versatility of ACTEM for the investigation of molecular dynamics and configuration-dependent energetics at a single molecular level.There has been significant research interest in controlling and imaging molecular dynamics, such as translational and rotational motions, especially at a single molecular level. Here we applied aberration-corrected transmission electron microscopy (ACTEM) to actuate and directly image the rotational motions of molecules anchored on a single-layer-graphene sheet. Nanometer-sized carbonaceous molecules anchored on graphene provide ideal systems for monitoring rotational motions via ACTEM. We observed the preferential registry of longer molecular axis along graphene zigzag or armchair lattice directions due to the stacking-dependent molecule-graphene energy landscape. The
The Effect of Rotation on Oscillatory Double-diffusive Convection (Semiconvection)
Moll, Ryan; Garaud, Pascale
2017-01-01
Oscillatory double-diffusive convection (ODDC, more traditionally called semiconvection) is a form of linear double-diffusive instability that occurs in fluids that are unstably stratified in temperature (Schwarzschild unstable), but stably stratified in chemical composition (Ledoux stable). This scenario is thought to be quite common in the interiors of stars and giant planets, and understanding the transport of heat and chemical species by ODDC is of great importance to stellar and planetary evolution models. Fluids unstable to ODDC have a tendency to form convective thermocompositional layers that significantly enhance the fluxes of temperature and chemical composition compared with microscopic diffusion. Although a number of recent studies have focused on studying properties of both layered and nonlayered ODDC, few have addressed how additional physical processes such as global rotation affect its dynamics. In this work, we study first how rotation affects the linear stability properties of rotating ODDC. Using direct numerical simulations, we then analyze the effect of rotation on properties of layered and nonlayered ODDC, and we study how the angle of the rotation axis with respect to the direction of gravity affects layering. We find that rotating systems can be broadly grouped into two categories based on the strength of rotation. The qualitative behavior in the more weakly rotating group is similar to nonrotating ODDC, but strongly rotating systems become dominated by vortices that are invariant in the direction of the rotation vector and strongly influence transport. We find that whenever layers form, rotation always acts to reduce thermal and compositional transport.
Electron cyclotron heating and core intrinsic rotation reversal in DIII-D
Energy Technology Data Exchange (ETDEWEB)
Grassie, J. S. de, E-mail: degrassie@fusion.gat.com [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Boedo, J. A. [University of California, San Diego, San Diego, CA 94550 (United States); Grierson, B. A. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States)
2015-12-10
The effect of electron cyclotron heating (ECH) on the intrinsic rotation profile in DIII-D is shown experimentally. Former DIII-D experiments have shown that ECH tends to cause an interior reduction in the normally co-Ip directed intrinsic rotation profile, and this core rotation can be fully reversed to the opposite direction. This effect is due to a turbulent rearrangement of the interior rotation profile. Here, we show results that there is more than one mechanism causing this. We compare two low density L-mode discharges where the only operational difference is the location of the ECH deposition. At low ECH power, comparable to the Ohmic power, the primary change is in the q-profile accompanied by a reversal of the core intrinsic rotation direction for the more off-axis deposition. The change in the shear of the q-profile fits well with a recent theoretical prediction for this rotation reversal. At higher ECH power, the primary change is in the core electron temperature, Te, accompanied by a hollowing of the rotation profile near the magnetic axis. This effect appears to be due to the change in electron collisionality, consistent with another theoretical, gyrokinetic prediction. The variety of phenomena that could allow ECH to modify the intrinsic rotation profile give some expectation that regions of large velocity shear in the interior could be generated, with the possibility of triggering internal transport barriers.
Integrated power and single axis attitude control system with two flywheels
Han, Bangcheng
2012-05-01
The existing research of the integrated power and attitude control system (IPACS) in satellites mainly focuses on the IPACS concept, which aims at solving the coupled problem between the attitude control and power tracking. In the IPACS, the configuration design of IPACS is usually not considered, and the coupled problem between two flywheels during the attitude control and energy storage has not been resolved. In this paper, an integrated power and single axis attitude control system using two counter rotating magnetically suspended flywheels mounted to an air table is designed. The control method of power and attitude control using flywheel is investigated and the coupling problem between energy storage and attitude control is resolved. A computer simulation of an integrated power and single axis attitude control system with two flywheels is performed, which consists of two counter rotating magnetically suspended flywheels mounted to an air rotary table. Both DC bus and a single axis attitude are the regulation goals. An attitude & DC bus coordinator is put forward to separate DC bus regulation and attitude control problems. The simulation results of DC bus regulation and attitude control are presented respectively with a DC bus regulator and a simple PD attitude controller. The simulation results demonstrate that it is possible to integrate power and attitude control simultaneously for satellite using flywheels. The proposed research provides theory basis for design of the IPACS.
Micro-vision servo control of a multi-axis alignment system for optical fiber assembly
Chen, Weihai; Yu, Fei; Qu, Jianliang; Chen, Wenjie; Zhang, Jianbin
2017-04-01
This paper describes a novel optical fiber assembly system featuring a multi-axis alignment function based on micro-vision feedback control. It consists of an active parallel alignment mechanism, a passive compensation mechanism, a micro-gripper and a micro-vision servo control system. The active parallel alignment part is a parallelogram-based design with remote-center-of-motion (RCM) function to achieve precise rotation without fatal lateral motion. The passive mechanism, with five degrees of freedom (5-DOF), is used to implement passive compensation for multi-axis errors. A specially designed 1-DOF micro-gripper mounted onto the active parallel alignment platform is adopted to grasp and rotate the optical fiber. A micro-vision system equipped with two charge-coupled device (CCD) cameras is introduced to observe the small field of view and obtain multi-axis errors for servo feedback control. The two CCD cameras are installed in an orthogonal arrangement—thus the errors can be easily measured via the captured images. Meanwhile, a series of tracking and measurement algorithms based on specific features of the target objects are developed. Details of the force and displacement sensor information acquisition in the assembly experiment are also provided. An experiment demonstrates the validity of the proposed visual algorithm by achieving the task of eliminating errors and inserting an optical fiber to the U-groove accurately.
Triple-axis spectrometer DruechaL
Energy Technology Data Exchange (ETDEWEB)
Buehrer, W.; Keller, P. [Lab. for Neutron Scattering ETH Zurich, Zurich (Switzerland) and Paul Scherrer Institute, Villigen (Switzerland)
1996-11-01
DruechaL is a triple-axis spectrometer located at a cold guide. The characteristics of guide and instrument allow the use of a broad spectral range of neutrons. The resolution in momentum and energy transfer can be tuned to match the experimental requirements by using either collimators or focusing systems (monochromator, antitrumpet, analyser). (author) figs., tabs., refs.
Resolution of a triple axis spectrometer
DEFF Research Database (Denmark)
Nielsen, Mourits; Bjerrum Møller, Hans
1969-01-01
A new method for obtaining the resolution function for a triple-axis neutron spectrometer is described, involving a combination of direct measurement and analytical calculation. All factors which contribute to the finite resolution of the instrument may be taken into account, and Gaussian...
A Portable Single Axis Magnetic Gradiometer
DEFF Research Database (Denmark)
Merayo, José M.G.; Petersen, Jan Raagaard; Nielsen, Otto V
2001-01-01
The single axis magnetic gradiometer based on two compact detector compensation (CDC) fluxgate ringcore sensors separated 20 cm is described. Despite its high stability and precision better than 1 nT, the calibration procedures are not straightforward. Firstly, the mono-axial measurement does not...
Tennis Rackets and the Parallel Axis Theorem
Christie, Derek
2014-01-01
This simple experiment uses an unusual graph straightening exercise to confirm the parallel axis theorem for an irregular object. Along the way, it estimates experimental values for g and the moment of inertia of a tennis racket. We use Excel to find a 95% confidence interval for the true values.
The Trading Axis in Irkutsk Downtown
Directory of Open Access Journals (Sweden)
Elena Grigoryeva
2016-10-01
Full Text Available The article reveals a linear concentration of the trading function in the historical center of Irkutsk. It features historical prerequisites and continuation of the tradition in the post-Soviet period, given the conversion of plants and factories. The article analyses the current state and prospects of modernization of the trading axis with its transformation into a modern public space.
Seismic constraints on rotation of Sun-like star and mass of exoplanet.
Gizon, Laurent; Ballot, Jérome; Michel, Eric; Stahn, Thorsten; Vauclair, Gérard; Bruntt, Hans; Quirion, Pierre-Olivier; Benomar, Othman; Vauclair, Sylvie; Appourchaux, Thierry; Auvergne, Michel; Baglin, Annie; Barban, Caroline; Baudin, Fréderic; Bazot, Michaël; Campante, Tiago; Catala, Claude; Chaplin, William; Creevey, Orlagh; Deheuvels, Sébastien; Dolez, Noël; Elsworth, Yvonne; García, Rafael; Gaulme, Patrick; Mathis, Stéphane; Mathur, Savita; Mosser, Benoît; Régulo, Clara; Roxburgh, Ian; Salabert, David; Samadi, Réza; Sato, Kumiko; Verner, Graham; Hanasoge, Shravan; Sreenivasan, Katepalli R
2013-08-13
Rotation is thought to drive cyclic magnetic activity in the Sun and Sun-like stars. Stellar dynamos, however, are poorly understood owing to the scarcity of observations of rotation and magnetic fields in stars. Here, inferences are drawn on the internal rotation of a distant Sun-like star by studying its global modes of oscillation. We report asteroseismic constraints imposed on the rotation rate and the inclination of the spin axis of the Sun-like star HD 52265, a principal target observed by the CoRoT satellite that is known to host a planetary companion. These seismic inferences are remarkably consistent with an independent spectroscopic observation (rotational line broadening) and with the observed rotation period of star spots. Furthermore, asteroseismology constrains the mass of exoplanet HD 52265b. Under the standard assumption that the stellar spin axis and the axis of the planetary orbit coincide, the minimum spectroscopic mass of the planet can be converted into a true mass of 1.85(-0.42)(+0.52)M(Jupiter), which implies that it is a planet, not a brown dwarf.
Seismic constraints on rotation of Sun-like star and mass of exoplanet
Gizon, Laurent; Michel, Eric; Stahn, Thorsten; Vauclair, Gérard; Bruntt, Hans; Quirion, Pierre-Olivier; Benomar, Othman; Vauclair, Sylvie; Appourchaux, Thierry; Auvergne, Michel; Baglin, Annie; Barban, Caroline; Baudin, Fréderic; Bazot, Michaël; Campante, Tiago; Catala, Claude; Chaplin, William; Creevey, Orlagh; Deheuvels, Sébastien; Dolez, Noël; Elsworth, Yvonne; García, Rafael; Gaulme, Patrick; Mathis, Stéphane; Mathur, Savita; Mosser, Benoît; Régulo, Clara; Roxburgh, Ian; Salabert, David; Samadi, Réza; Sato, Kumiko; Verner, Graham; Hanasoge, Shravan; Sreenivasan, Katepalli R
2013-01-01
Rotation is thought to drive cyclic magnetic activity in the Sun and Sun-like stars. Stellar dynamos, however, are poorly understood owing to the scarcity of observations of rotation and magnetic fields in stars. Here, inferences are drawn on the internal rotation of a distant Sun-like star by studying its global modes of oscillation. We report asteroseismic constraints imposed on the rotation rate and the inclination of the spin axis of the Sun-like star HD 52265, a principal target observed by the CoRoT satellite that is known to host a planetary companion. These seismic inferences are remarkably consistent with an independent spectroscopic observation (rotational line broadening) and with the observed rotation period of star spots. Furthermore, asteroseismology constrains the mass of exoplanet HD 52265b. Under the standard assumption that the stellar spin axis and the axis of the planetary orbit coincide, the minimum spectroscopic mass of the planet can be converted into a true mass of 1.85 (+0.52,-0.42) M...
Elliptical Galaxies: Rotationally Distorted, After All
Directory of Open Access Journals (Sweden)
Caimmi, R.
2009-12-01
Full Text Available On the basis of earlier investigations onhomeoidally striated Mac Laurin spheroids and Jacobi ellipsoids (Caimmi and Marmo2005, Caimmi 2006a, 2007, different sequences of configurations are defined and represented in the ellipticity-rotation plane, $({sf O}hat{e}chi_v^2$. The rotation parameter, $chi_v^2$, is defined as the ratio, $E_mathrm{rot}/E_mathrm{res}$, of kinetic energy related to the mean tangential equatorial velocity component, $M(overline{v_phi}^2/2$, to kineticenergy related to tangential equatorial component velocity dispersion, $Msigma_{phiphi}^2/2$, andresidual motions, $M(sigma_{ww}^2+sigma_{33}^2/2$.Without loss of generality (above a thresholdin ellipticity values, the analysis is restricted to systems with isotropic stress tensor, whichmay be considered as adjoint configurationsto any assigned homeoidally striated density profile with anisotropic stress tensor, different angular momentum, and equal remaining parameters.The description of configurations in the$({sf O}hat{e}chi_v^2$ plane is extendedin two respects, namely (a from equilibriumto nonequilibrium figures, where the virialequations hold with additional kinetic energy,and (b from real to imaginary rotation, wherethe effect is elongating instead of flattening,with respect to the rotation axis.An application is made toa subsample $(N=16$ of elliptical galaxies extracted from richer samples $(N=25,~N=48$of early type galaxies investigated within theSAURON project (Cappellari et al. 2006, 2007.Sample objects are idealized as homeoidallystriated MacLaurinspheroids and Jacobi ellipsoids, and theirposition in the $({sf O}hat{e}chi_v^2$plane is inferred from observations followinga procedure outlined in an earlier paper(Caimmi 2009b. The position of related adjoint configurations with isotropic stresstensor is also determined. With a singleexception (NGC 3379, slow rotators arecharacterized by low ellipticities $(0lehat{e}<0.2$, low anisotropy parameters$(0ledelta<0
Two-dimensionalization of the flow driven by a slowly rotating impeller in a rapidly rotating fluid
Machicoane, Nathanaël; Cortet, Pierre-Philippe
2016-01-01
We characterize the two-dimensionalization process in the turbulent flow produced by an impeller rotating at a rate $\\omega$ in a fluid rotating at a rate $\\Omega$ around the same axis for Rossby number $Ro=\\omega/\\Omega$ down to $10^{-2}$. The flow can be described as the superposition of a large-scale vertically invariant global rotation and small-scale shear layers detached from the impeller blades. As $Ro$ decreases, the large-scale flow is subjected to azimuthal modulations. In this regime, the shear layers can be described in terms of wakes of inertial waves traveling with the blades, originating from the velocity difference between the non-axisymmetric large-scale flow and the blade rotation. The wakes are well defined and stable at low Rossby number, but they become disordered at $Ro$ of order of 1. This experiment provides insight into the route towards pure two-dimensionalization induced by a background rotation for flows driven by a non-axisymmetric rotating forcing.
Turbulent Compressible Convection with Rotation. 2; Mean Flows and Differential Rotation
Brummell, Nicholas H.; Hurlburt, Neal E.; Toomre, Juri
1998-01-01
The effects of rotation on turbulent, compressible convection within stellar envelopes are studied through three-dimensional numerical simulations conducted within a local f-plane model. This work seeks to understand the types of differential rotation that can be established in convective envelopes of stars like the Sun, for which recent helioseismic observations suggest an angular velocity profile with depth and latitude at variance with many theoretical predictions. This paper analyzes the mechanisms that are responsible for the mean (horizontally averaged) zonal and meridional flows that are produced by convection influenced by Coriolis forces. The compressible convection is considered for a range of Rayleigh, Taylor, and Prandtl (and thus Rossby) numbers encompassing both laminar and turbulent flow conditions under weak and strong rotational constraints. When the nonlinearities are moderate, the effects of rotation on the resulting laminar cellular convection leads to distinctive tilts of the cell boundaries away from the vertical. These yield correlations between vertical and horizontal motions that generate Reynolds stresses that can drive mean flows, interpretable as differential rotation and meridional circulations. Under more vigorous forcing, the resulting turbulent convection involves complicated and contorted fluid particle trajectories, with few clear correlations between vertical and horizontal motions, punctuated by an evolving and intricate downflow network that can extend over much of the depth of the layer. Within such networks are some coherent structures of vortical downflow that tend to align with the rotation axis. These yield a novel turbulent alignment mechanism, distinct from the laminar tilting of cellular boundaries, that can provide the principal correlated motions and thus Reynolds stresses and subsequently mean flows. The emergence of such coherent structures that can persist amidst more random motions is a characteristic of turbulence
Wave-driven Rotation in Supersonically Rotating Mirrors
Energy Technology Data Exchange (ETDEWEB)
A. Fetterman and N.J. Fisch
2010-02-15
Supersonic rotation in mirrors may be produced by radio frequency waves. The waves produce coupled diffusion in ion kinetic and potential energy. A population inversion along the diffusion path then produces rotation. Waves may be designed to exploit a natural kinetic energy source or may provide the rotation energy on their own. Centrifugal traps for fusion and isotope separation may benefit from this wave-driven rotation.
A three-axis Intersecting Degree Measurement%三轴相交度的一种测量方法
Institute of Scientific and Technical Information of China (English)
王明元; 杨连春; 余海盛; 张新
2012-01-01
A measurement method of three-axis turntable's axis intersecting degree is described. The measurement method is the use of laser tracker to measure the turntable, the two fixed points on the frame (the target mirror seat position) around the rotation axis of movement of some of the space coordinates of the point where the fit of these points to construct two circles and its center, and then construct a . circle by the two rotary axes. Thus, the rotation axis of the three-axis turntable constructed after three rotary as can be calculated the distance between each, according to three rotary as the distance between any two three-axis can be calculated intersection degree of three-axis turntable.%介绍一种通过激光跟踪仪测量三轴转台三轴相交度的测量方法.该测量方法是利用激光跟踪仪测量出转台内、中、外框上两固定点(靶镜座位置)绕其回转轴线运动时一些位置点的空间坐标,拟合这些点从而构造出两个圆及其圆心,再由两个圆心构造出一条回转轴线.这样,将三轴转台的三条回转轴线构造出来以后就可计算出三条回转轴线两两之间的距离,根据三条回转轴线两两之间的距离就能求出三轴转台的三轴相交度.
Giannitti, Federico; Margineda, Carlos A; Cid, María S; Diab, Santiago S; Weber, Natalia; Rodríguez, Alejandro; Campero, Carlos M; Odriozola, Ernesto R
2012-11-01
The current study describes a naturally occurring cluster of cases of Wedelia glauca intoxication. Seven of 14 axis deer (Axis axis) and 1 of 8 llamas (Lama glama) in a zoo of Buenos Aires province, Argentina, died suddenly after ingestion of a new batch of alfalfa (Medicago sativa) hay bales contaminated with the hepatotoxic plant W. glauca. Necropsies of 1 deer and 1 llama were performed. Pathological findings in both animals included severe diffuse acute centrilobular hepatocellular necrosis and hemorrhage, and clear yellowish translucent gelatinous edema on the wall of the gall bladder and the serosa of the choledochoduodenal junction. Fragments of W. glauca plants were identified in the hay based on the botanical characteristics of the leaves. Samples of gastric contents were examined by microhistological analysis, which identified epidermal fragments of W. glauca based on the presence of characteristic uniseriate glandular hairs (trichomes), confirming recent ingestion of W. glauca in both cases. The fragments were quantified and represented 5% of all examined vegetal fragments in the deer and 10% in the llama.
Rotator Cuff Injuries - Multiple Languages
... Are Here: Home → Multiple Languages → All Health Topics → Rotator Cuff Injuries URL of this page: https://medlineplus.gov/ ... V W XYZ List of All Topics All Rotator Cuff Injuries - Multiple Languages To use the sharing features ...
Directory of Open Access Journals (Sweden)
S. Wittig
1998-01-01
Full Text Available Cooling of high speed rotating components is a typical situation found in turbomachinery as well as in automobile engines. Accurate knowledge of discharge coefficients and heat transfer of related components is essential for the high performance of the whole engine. This can be achieved by minimized cooling air flows and avoidance of hot spots. In high speed rotating clutches for example aerodynamic investigations improving heat transfer have not been considered in the past. Advanced concepts of modern plate design try to reduce thermal loads by convective cooling methods. Therefore, secondary cooling air flows have to be enhanced by an appropriate design of the rotor stator system with orifices. CFD modelling is used to improve the basic understanding of the flow field in typical geometries used in these systems.
DEFF Research Database (Denmark)
Rasmusson, Allan
2009-01-01
is obeyed by randomizing the orientation of the virtual probe itself within the thick section. Overall, the benefit is that positional information is kept for any block and section of the specimen. As the Spatial Rotator is a 3D probe, data must be gathered from sections thicker than 25 micro meters to form......The inherent demand for unbiasedness for some stereological estimators imposes a demand of not only positional uniform randomness but also isotropic randomness, i.e. directional uniform randomness. In order to comply with isotropy, one must perform a random rotation of the object of interest before...... it is embedded and sectioned. This has the unfortunate side effect that all information about positioning within the object is lost for blocks and sections. For complex tissue, like the mammalian brain, this information is of utmost importance to ensure measurements are performed in the correct region...
Earth rotation and geodynamics
Bogusz, Janusz; Brzezinski, Aleksander; Kosek, Wieslaw; Nastula, Jolanta
2015-12-01
This paper presents the summary of research activities carried out in Poland in 2011-2014 in the field of Earth rotation and geodynamics by several Polish research institutions. It contains a summary of works on Earth rotation, including evaluation and prediction of its parameters and analysis of the related excitation data as well as research on associated geodynamic phenomena such as geocentre motion, global sea level change and hydrological processes. The second part of the paper deals with monitoring of geodynamic phenomena. It contains analysis of geodynamic networks of local, and regional scale using space (GNSS and SLR) techniques, Earth tides monitoring with gravimeters and water-tube hydrostatic clinometer, and the determination of secular variation of the Earth' magnetic field.
Rotational spectrum of tryptophan
Energy Technology Data Exchange (ETDEWEB)
Sanz, M. Eugenia, E-mail: maria.sanz@kcl.ac.uk; Cabezas, Carlos, E-mail: ccabezas@qf.uva.es; Mata, Santiago, E-mail: santiago.mata@uva.es; Alonso, Josè L., E-mail: jlalonso@qf.uva.es [Grupo de Espectroscopia Molecular (GEM), Edificio Quifima, Laboratorios de Espectroscopia y Bioespectroscopia, Unidad Asociada CSIC, Parque Científico Uva, Universidad de Valladolid, 47011 Valladolid (Spain)
2014-05-28
The rotational spectrum of the natural amino acid tryptophan has been observed for the first time using a combination of laser ablation, molecular beams, and Fourier transform microwave spectroscopy. Independent analysis of the rotational spectra of individual conformers has conducted to a definitive identification of two different conformers of tryptophan, with one of the observed conformers never reported before. The analysis of the {sup 14}N nuclear quadrupole coupling constants is of particular significance since it allows discrimination between structures, thus providing structural information on the orientation of the amino group. Both observed conformers are stabilized by an O–H···N hydrogen bond in the side chain and a N–H···π interaction forming a chain that reinforce the strength of hydrogen bonds through cooperative effects.
Rotational Spectrum of Tryptophan
Sanz, M. Eugenia; Cabezas, Carlos; Mata, Santiago; Alonso, José L.
2014-06-01
The rotational spectrum of the natural amino acid tryptophan has been observed using a recently constructed LA-MB-FTMW spectrometer, specifically designed to optimize the detection of heavier molecules at a lower frequency range. Independent analyses of the rotational spectra of individual conformers have conducted to a definitive identification of two different conformers of tryptophan, with one of the observed conformers never reported before. The experimental values of the 14N nuclear quadrupole coupling constants have been found capital in the discrimination of the conformers. Both observed conformers are stabilized by a O-H\\cdotsN hydrogen bond in the side chain and a N-H\\cdotsπ interaction forming a chain that reinforces the strength of hydrogen bonds through cooperative effects.
A Translational Polarization Rotator
Chuss, David T; Pisano, Giampaolo; Ackiss, Sheridan; U-Yen, Kongpop; Ng, Ming wah
2012-01-01
We explore a free-space polarization modulator in which a variable phase introduction between right- and left-handed circular polarization components is used to rotate the linear polarization of the outgoing beam relative to that of the incoming beam. In this device, the polarization states are separated by a circular polarizer that consists of a quarter-wave plate in combination with a wire grid. A movable mirror is positioned behind and parallel to the circular polarizer. As the polarizer-mirror distance is separated, an incident linear polarization will be rotated through an angle that is proportional to the introduced phase delay. We demonstrate a prototype device that modulates Stokes Q and U over a 20% bandwidth.
Costella, J P; Rawlinson, A A; Costella, John P.; Kellar, Bruce H. J. Mc; Rawlinson, Andrew A.
2001-01-01
We review why the Thomas rotation is a crucial facet of special relativity, that is just as fundamental, and just as "unintuitive" and "paradoxical", as such traditional effects as length contraction, time dilation, and the ambiguity of simultaneity. We show how this phenomenon can be quite naturally introduced and investigated in the context of a typical introductory course on special relativity, in a way that is appropriate for, and completely accessible to, undergraduate students. We also demonstrate, in a more advanced section aimed at the graduate student studying the Dirac equation and relativistic quantum field theory, that careful consideration of the Thomas rotation will become vital as modern experiments in particle physics continue to move from unpolarized to polarized cross-sections.
Rotator cuff tendon connections with the rotator cable.
Rahu, Madis; Kolts, Ivo; Põldoja, Elle; Kask, Kristo
2017-07-01
The literature currently contains no descriptions of the rotator cuff tendons, which also describes in relation to the presence and characteristics of the rotator cable (anatomically known as the ligamentum semicirculare humeri). The aim of the current study was to elucidate the detailed anatomy of the rotator cuff tendons in association with the rotator cable. Anatomic dissection was performed on 21 fresh-frozen shoulder specimens with an average age of 68 years. The rotator cuff tendons were dissected from each other and from the glenohumeral joint capsule, and the superior glenohumeral, coracohumeral, coracoglenoidal and semicircular (rotator cable) ligaments were dissected. Dissection was performed layer by layer and from the bursal side to the joint. All ligaments and tendons were dissected in fine detail. The rotator cable was found in all specimens. It was tightly connected to the supraspinatus (SSP) tendon, which was partly covered by the infraspinatus (ISP) tendon. The posterior insertion area of the rotator cable was located in the region between the middle and inferior facets of the greater tubercle of the humerus insertion areas for the teres minor (TM), and ISP tendons were also present and fibres from the SSP extended through the rotator cable to those areas. The connection between the rotator cable and rotator cuff tendons is tight and confirms the suspension bridge theory for rotator cuff tears in most areas between the SSP tendons and rotator cable. In its posterior insertion area, the rotator cable is a connecting structure between the TM, ISP and SSP tendons. These findings might explain why some patients with relatively large rotator cuff tears can maintain seamless shoulder function.
Use of two-axis joystick for control of externally powered shoulder disarticulation prostheses
Directory of Open Access Journals (Sweden)
Robert D. Lipschutz, BSME, CP
2011-07-01
Full Text Available We explored a new method for simple and accurate control of shoulder movement for externally powered shoulder disarticulation prostheses with a two-axis joystick. We tested 10 subjects with intact shoulders and arms to determine the average amount of shoulder motion and force available to control an electronic input device. We then applied this information to two different input strategies to examine their effectiveness: (1 a traditional rocker potentiometer and a pair of force-sensing resistors and (2 a two-axis joystick. Three nondisabled subjects and two subjects with shoulder disarticulation amputations attempted to control an experimental externally powered shoulder using both control strategies. Two powered arms were tested, one with powered flexion/extension and humeral rotation and one with powered flexion/extension and adduction/abduction. Overwhelmingly, the subjects preferred the joystick control, because it was more intuitively linked with their shoulder movement. Additionally, two motions (one in each axis could be controlled simultaneously. This pilot study provides valuable insight into an effective means of controlling high-level, externally powered prostheses with a two-axis joystick.
High Resolution Triple Axis X-Ray Diffraction Analysis of II-VI Semiconductor Crystals
Volz, H. M.; Matyi, R. J.
1999-01-01
The objective of this research program is to develop methods of structural analysis based on high resolution triple axis X-ray diffractometry (HRTXD) and to carry out detailed studies of defect distributions in crystals grown in both microgravity and ground-based environments. HRTXD represents a modification of the widely used double axis X-ray rocking curve method for the characterization of grown-in defects in nearly perfect crystals. In a double axis rocking curve experiment, the sample is illuminated by a monochromatic X-ray beam and the diffracted intensity is recorded by a fixed, wide-open detector. The intensity diffracted by the sample is then monitored as the sample is rotated through the Bragg reflection condition. The breadth of the peak, which is often reported as the full angular width at half the maximum intensity (FWHM), is used as an indicator of the amount of defects in the sample. This work has shown that high resolution triple axis X-ray diffraction is an effective tool for characterizing the defect structure in semiconductor crystals, particularly at high defect densities. Additionally, the technique is complimentary to X-ray topography for defect characterization in crystals.
Use of a Two-Axis Joystick for Control of Externally Powered, Shoulder Disarticulation Prostheses
Lipschutz, Robert D.; Lock, Blair; Sensinger, Jonathon; Schultz, Aimee E.; Kuiken, Todd A.
2015-01-01
We explored a new method for simple and accurate control of shoulder movement for externally powered shoulder disarticulation prostheses using a two-axis joystick. Ten subjects with intact shoulders and arms were tested to determine the average amount of shoulder motion and force available for control of an electronic input device. This information was then applied to two different input strategies in order to examine their effectiveness: (1) a traditional strategy implemented with a rocker potentiometer and a pair of force-sensing resistors (FSRs), and (2) a strategy implemented with a two-axis joystick. Three able-bodied subjects and two subjects with shoulder disarticulation amputations attempted to control an experimental powered shoulder using both control strategies. Two powered arms were tested, one with powered flexion/extension and humeral rotation, and one with powered flexion/extension and adduction/abduction. Overwhelmingly, the subjects preferred the joystick control, as it was more intuitively linked with their shoulder movement. Additionally, two motions (one in each axis) could be controlled simultaneously. This pilot study provides valuable insight into an effective means of controlling high-level, externally powered prostheses via a two-axis joystick. PMID:21938653
Use of two-axis joystick for control of externally powered shoulder disarticulation prostheses.
Lipschutz, Robert D; Lock, Blair; Sensinger, Jonathon; Schultz, Aimee E; Kuiken, Todd A
2011-01-01
We explored a new method for simple and accurate control of shoulder movement for externally powered shoulder disarticulation prostheses with a two-axis joystick. We tested 10 subjects with intact shoulders and arms to determine the average amount of shoulder motion and force available to control an electronic input device. We then applied this information to two different input strategies to examine their effectiveness: (1) a traditional rocker potentiometer and a pair of force-sensing resistors and (2) a two-axis joystick. Three nondisabled subjects and two subjects with shoulder disarticulation amputations attempted to control an experimental externally powered shoulder using both control strategies. Two powered arms were tested, one with powered flexion/extension and humeral rotation and one with powered flexion/extension and adduction/abduction. Overwhelmingly, the subjects preferred the joystick control, because it was more intuitively linked with their shoulder movement. Additionally, two motions (one in each axis) could be controlled simultaneously. This pilot study provides valuable insight into an effective means of controlling high-level, externally powered prostheses with a two-axis joystick.
Properties of Rotating Neutron Star
Directory of Open Access Journals (Sweden)
Shailesh K. Singh
2015-08-01
Full Text Available Using the nuclear equation of states for a large variety of relativistic and non-relativistic force parameters, we calculate the static and rotating masses and radii of neutron stars. From these equation of states, we evaluate the properties of rotating neutron stars, such as rotational frequencies, moment of inertia, quadrupole deformation parameter, rotational ellipticity and gravitational wave strain amplitude. The estimated gravitational wave strain amplitude of the star is found to be~sim 10-23.
Topographic instability of flow in a rotating fluid
Directory of Open Access Journals (Sweden)
K. I. Patarashvili
2006-01-01
Full Text Available Here are presented the results of experimental and theoretical studies on a stability of zonal geostrophic flows in the rotating layer of the shallow water. In the experiments, a special apparatus by Abastumani Astrophysical Observatory Georgian Academy of Science was used. This apparatus represents a paraboloid of rotation, which can be set in a regulable rotation around the vertical axis. Maximal diameter of the paraboloid is 1.2 m, radius of curvature in the pole is 0.698 m. In the paraboloid, water spreads on walls as a layer uniform on height under the period of rotation 1.677 s. Against a background of the rotating fluid, the zonal flows are formed by the source-sink system. It consists of two concentric circular perforations on the paraboloid bottom (width is 0.3 cm, radiuses are 8.4 and 57.3 cm, respectively; water can be pumped through them with various velocities and in all directions. It has been established that under constant vertical depth of the rotating fluid the zonal flows are stable. There are given the measurements of the radial profiles for the water level and velocity in the stationary regime. It has been found that zonal flows may lose stability under the presence of the radial gradient of full depth formed by a change of angular velocity of paraboloid rotation. An instability origin results in the loss of flow axial symmetry and in the appearance of self-excited oscillations in the zonal flow. At the given angular velocity of rotation, instability is observed only in the definite range of intensities of the source-sink system. The theoretical estimations are performed in the framework of the equations of the shallow water theory, including the terms describing the bottom friction. It has been shown that the instability of zonal flows found experimentally has a topographical nature and is related with non-monotone dependence of the potential vorticity on radius.
Physics of Rotating and Expanding Black Hole Universe
Directory of Open Access Journals (Sweden)
Seshavatharam U. V. S.
2010-04-01
Full Text Available Throughout its journey universe follows strong gravity. By unifying general theory of relativity and quantum mechanics a simple derivation is given for rotating black hole's temperature. It is shown that when the rotation speed approaches light speed temperature approaches Hawking's black hole temperature. Applying this idea to the cosmic black hole it is noticed that there is "no cosmic temperature" if there is "no cosmic rotation". Starting from the Planck scale it is assumed that universe is a rotating and expanding black hole. Another key assumption is that at any time cosmic black hole rotates with light speed. For this cosmic sphere as a whole while in light speed rotation "rate of decrease" in temperature or "rate of increase" in cosmic red shift is a measure of "rate of cosmic expansion". Since 1992, measured CMBR data indicates that, present CMB is same in all directions equal to $2.726^circ$ K, smooth to 1 part in 100,000 and there is no continuous decrease! This directly indicates that, at present rate of decrease in temperature is practically zero and rate of expansion is practically zero. Universe is isotropic and hence static and is rotating as a rigid sphere with light speed. At present galaxies are revolving with speeds proportional to their distances from the cosmic axis of rotation. If present CMBR temperature is $2.726^circ$ K, present value of obtained angular velocity is $2.17 imes 10^{-18}$ rad/sec $cong$ 67 Km/sec$imes$Mpc. Present cosmic mass density and cosmic time are fitted with a $ln (volume ratio$ parameter. Finally it can be suggested that dark matter and dark energy are ad-hoc and misleading concepts.
Broadband Rotational Spectroscopy
Pate, Brooks
2014-06-01
The past decade has seen several major technology advances in electronics operating at microwave frequencies making it possible to develop a new generation of spectrometers for molecular rotational spectroscopy. High-speed digital electronics, both arbitrary waveform generators and digitizers, continue on a Moore's Law-like development cycle that started around 1993 with device bandwidth doubling about every 36 months. These enabling technologies were the key to designing chirped-pulse Fourier transform microwave (CP-FTMW) spectrometers which offer significant sensitivity enhancements for broadband spectrum acquisition in molecular rotational spectroscopy. A special feature of the chirped-pulse spectrometer design is that it is easily implemented at low frequency (below 8 GHz) where Balle-Flygare type spectrometers with Fabry-Perot cavity designs become technologically challenging due to the mirror size requirements. The capabilities of CP-FTMW spectrometers for studies of molecular structure will be illustrated by the collaborative research effort we have been a part of to determine the structures of water clusters - a project which has identified clusters up to the pentadecamer. A second technology trend that impacts molecular rotational spectroscopy is the development of high power, solid state sources in the mm-wave/THz regions. Results from the field of mm-wave chirped-pulse Fourier transform spectroscopy will be described with an emphasis on new problems in chemical dynamics and analytical chemistry that these methods can tackle. The third (and potentially most important) technological trend is the reduction of microwave components to chip level using monolithic microwave integrated circuits (MMIC) - a technology driven by an enormous mass market in communications. Some recent advances in rotational spectrometer designs that incorporate low-cost components will be highlighted. The challenge to the high-resolution spectroscopy community - as posed by Frank De
Energy Technology Data Exchange (ETDEWEB)
Allouche, Erez; Jaganathan, Arun P.
2016-10-11
The invention is a new turbine structure having a housing that rotates. The housing has a sidewall, and turbine blades are attached to a sidewall portion. The turbine may be completely open in the center, allowing space for solids and debris to be directed out of the turbine without jamming the spinning blades/sidewall. The turbine may be placed in a generator for generation of electrical current.
Dobrovolskis, Anthony R.; Cuzzi, Jeffrey N. (Technical Monitor)
1995-01-01
The shape and spin of Neptune's outermost satellite Nereid are still unknown. Ground-based photometry indicates large brightness variations, but different observers report very different lightcurve amplitudes and periods. On the contrary, Voyager 2 images spanning 12 days show no evidence of variations greater than 0.1 mag. The latter suggest either that Nereid is nearly spherical, or that it is rotating slowly. We propose that tides have already despun Nereid's rotation to a period of a few weeks, during the time before the capture of Triton when Nereid was closer to Neptune. Since Nereid reached its present orbit, tides have further despun Nereid to a period on the order of a month. For Nereid's orbital eccentricity of 0.75, tidal evolution ceases when the spin period is still approximately 1/8 of the orbital period. Furthermore, the synchronous resonance becomes quite weak for such high eccentricities, along with other low-order spin orbit commensurabilities. In contrast, high-order resonances become very strong particularly the 6:1, 6.5:1, 7:1, 7.5:1, and 8:1 spin states. If Nereid departs by more than approximately 1% from a sphere, however, these resonances overlap, generating chaos. Our simulations show that Nereid is likely to be in chaotic rotation for any spin period longer than about 2 weeks.
Energy Technology Data Exchange (ETDEWEB)
Lee, S.Y.
1990-06-18
The generalized snake configuration offers advantages of either shorter total snake length and smaller orbit displacement in the compact configuration or the multi-functions in the split configuration. We found that the compact configuration can save about 10% of the total length of a snake. On other hand, the spilt snake configuration can be used both as a snake and as a spin rotator for the helicity state. Using the orbit compensation dipoles, the spilt snake configuration can be located at any distance on both sides of the interaction point of a collider provided that there is no net dipole rotation between two halves of the snake. The generalized configuration is then applied to the partial snake excitation. Simple formula have been obtained to understand the behavior of the partial snake. Similar principle can also be applied to the spin rotators. We also estimate the possible snake imperfections are due to various construction errors of the dipole magnets. Accuracy of field error of better than 10{sup {minus}4} will be significant. 2 refs., 5 figs.
Bioreactor rotating wall vessel
2001-01-01
The NASA Bioreactor provides a low turbulence culture environment which promotes the formation of large, three-dimensional cell clusters. Due to their high level of cellular organization and specialization, samples constructed in the bioreactor more closely resemble the original tumor or tissue found in the body. The work is sponsored by NASA's Office of Biological and Physical Research. The bioreactor is managed by the Biotechnology Cell Science Program at NASA's Johnson Space Center (JSC). NASA-sponsored bioreactor research has been instrumental in helping scientists to better understand normal and cancerous tissue development. In cooperation with the medical community, the bioreactor design is being used to prepare better models of human colon, prostate, breast and ovarian tumors. Cartilage, bone marrow, heart muscle, skeletal muscle, pancreatic islet cells, liver and kidney are just a few of the normal tissues being cultured in rotating bioreactors by investigators. Cell constructs grown in a rotating bioreactor on Earth (left) eventually become too large to stay suspended in the nutrient media. In the microgravity of orbit, the cells stay suspended. Rotation then is needed for gentle stirring to replenish the media around the cells.
Energy Technology Data Exchange (ETDEWEB)
Bambi, Cosimo, E-mail: bambi@fudan.edu.cn; Modesto, Leonardo, E-mail: lmodesto@fudan.edu.cn
2013-04-25
The formation of spacetime singularities is a quite common phenomenon in General Relativity and it is regulated by specific theorems. It is widely believed that spacetime singularities do not exist in Nature, but that they represent a limitation of the classical theory. While we do not yet have any solid theory of quantum gravity, toy models of black hole solutions without singularities have been proposed. So far, there are only non-rotating regular black holes in the literature. These metrics can be hardly tested by astrophysical observations, as the black hole spin plays a fundamental role in any astrophysical process. In this Letter, we apply the Newman–Janis algorithm to the Hayward and to the Bardeen black hole metrics. In both cases, we obtain a family of rotating solutions. Every solution corresponds to a different matter configuration. Each family has one solution with special properties, which can be written in Kerr-like form in Boyer–Lindquist coordinates. These special solutions are of Petrov type D, they are singularity free, but they violate the weak energy condition for a non-vanishing spin and their curvature invariants have different values at r=0 depending on the way one approaches the origin. We propose a natural prescription to have rotating solutions with a minimal violation of the weak energy condition and without the questionable property of the curvature invariants at the origin.
Bioreactor rotating wall vessel
2001-01-01
The NASA Bioreactor provides a low turbulence culture environment which promotes the formation of large, three-dimensional cell clusters. Due to their high level of cellular organization and specialization, samples constructed in the bioreactor more closely resemble the original tumor or tissue found in the body. The work is sponsored by NASA's Office of Biological and Physical Research. The bioreactor is managed by the Biotechnology Cell Science Program at NASA's Johnson Space Center (JSC). NASA-sponsored bioreactor research has been instrumental in helping scientists to better understand normal and cancerous tissue development. In cooperation with the medical community, the bioreactor design is being used to prepare better models of human colon, prostate, breast and ovarian tumors. Cartilage, bone marrow, heart muscle, skeletal muscle, pancreatic islet cells, liver and kidney are just a few of the normal tissues being cultured in rotating bioreactors by investigators. Cell constructs grown in a rotating bioreactor on Earth (left) eventually become too large to stay suspended in the nutrient media. In the microgravity of orbit, the cells stay suspended. Rotation then is needed for gentle stirring to replenish the media around the cells.
Coordinate-Free Rotation Operator.
Leubner, C.
1979-01-01
Suggests the use of a coordinate-free rotation operator for the teaching of rotations in Euclidean three space because of its twofold didactic advantage. Illustrates the potentialities of the coordinate-free rotation operator approach by a number of examples. (Author/GA)
Trenkler, G.; Trenkler, D.
2008-01-01
Using the elementary tools of matrix theory, we show that the product of two rotations in the three-dimensional Euclidean space is a rotation again. For this purpose, three types of rotation matrices are identified which are of simple structure. One of them is the identity matrix, and each of the other two types can be uniquely characterized by…
The calculation of the mass moment of inertia of a fluid in a rotating rectangular tank
1977-01-01
This analysis calculated the mass moment of inertia of a nonviscous fluid in a slowly rotating rectangular tank. Given the dimensions of the tank in the x, y, and z coordinates, the axis of rotation, the percentage of the tank occupied by the fluid, and angle of rotation, an algorithm was written that could calculate the mass moment of inertia of the fluid. While not included in this paper, the change in the mass moment of inertia of the fluid could then be used to calculate the force exerted by the fluid on the container wall.
Detecting Nano-Scale Vibrations in Rotating Devices by Using Advanced Computational Methods
Directory of Open Access Journals (Sweden)
Raúl M. del Toro
2010-05-01
Full Text Available This paper presents a computational method for detecting vibrations related to eccentricity in ultra precision rotation devices used for nano-scale manufacturing. The vibration is indirectly measured via a frequency domain analysis of the signal from a piezoelectric sensor attached to the stationary component of the rotating device. The algorithm searches for particular harmonic sequences associated with the eccentricity of the device rotation axis. The detected sequence is quantified and serves as input to a regression model that estimates the eccentricity. A case study presents the application of the computational algorithm during precision manufacturing processes.
Experimental evidence of a triadic resonance of plane inertial waves in a rotating fluid
Bordes, Guilhem; Dauxois, Thierry; Cortet, Pierre-Philippe
2011-01-01
Plane inertial waves are generated using a wavemaker, made of oscillating stacked plates, in a rotating water tank. Using particle image velocimetry, we observe that, after a transient, the primary plane wave is subject to a subharmonic instability and excites two secondary plane waves. The measured frequencies and wavevectors of these secondary waves are in quantitative agreement with the predictions of the triadic resonance mechanism. The secondary wavevectors are found systematically more normal to the rotation axis than the primary wavevector: this feature illustrates the basic mechanism at the origin of the energy transfers towards slow, quasi two-dimensional, motions in rotating turbulence.
On some geometric features of the Kramer interior solution for a rotating perfect fluid
Chinea, F J
1999-01-01
Geometric features (including convexity properties) of an exact interior gravitational field due to a self-gravitating axisymmetric body of perfect fluid in stationary, rigid rotation are studied. In spite of the seemingly non-Newtonian features of the bounding surface for some rotation rates, we show, by means of a detailed analysis of the three-dimensional spatial geodesics, that the standard Newtonian convexity properties do hold. A central role is played by a family of geodesics that are introduced here, and provide a generalization of the Newtonian straight lines parallel to the axis of rotation.
Initial Test Results from a 3-axis Vibrating Ring Gyroscope
Energy Technology Data Exchange (ETDEWEB)
Gallacher, B J; Neasham, J A; Burdess, J S; Harris, A J [INSAT University of Newcastle upon Tyne NE1 7RU (United Kingdom)
2006-04-01
There are several application areas where the simultaneous measurement of rates of rotation about three mutually orthogonal axes is required. In this paper the principle features of a 3-axis vibrating ring gyroscope are described. The fabrication process for the gyroscope is presented and employs standard MEMS techniques. The modal properties for the ring are measured experimentally using laser vibrometry and electrostatic sensing and compared with the design predictions. In operation as a rate gyroscope it is necessary to excite the primary motion of the gyroscope and control is amplitude. As Q-factors of vibratory gyroscope are typically of the order 10{sup 3}-10{sup 4} slight variations in environmental conditions will perturb the natural frequency of the primary mode significantly. To ensure the primary motion of the gyroscope is maintained with constant amplitude a control scheme employing both frequency tracking and amplitude control is required. An electronic control system using digital signal processing (DSP) has been developed to ensure excitation of the primary motion occurs at resonance with controlled amplitude. The control scheme employs an embedded processor to generate the drive frequency (via a D/A converter) and to monitor the primary vibration (via an A/D converter). Experimental results from the control scheme highlighting its effectiveness over conventional PLL approaches are presented.
The Parameters Affect on Power Coefficient Vertical Axis Wind Turbine
Directory of Open Access Journals (Sweden)
Ahmed Y. Qasim
2012-04-01
Full Text Available ABSTRACT: This study describes the design of a special type of vertical axis rotor wind turbine with moveable vertically positioned vanes. The novel design increases the torque in the left side of the wind turbine by increasing the drag coefficient. It also reduces the negative torque of the frame which rotates contrary to the wind in the other side. Two different types of models, having different vane shapes (flat vane and cavity shaped vane, were fabricated. Each type consisted of two models with varying number of frames (three and four frames. The models were tested in a wind tunnel with variable wind speed in order to understand the effect of shape, weight, and number of frames on the power coefficient of the wind turbine. ABSTRAK: Di dalam kajian ini, rotor turbin angin berpaksi vertikel sebagai rangka khusus telah direkabentuk dengan lokasi vertikel mudahalih oleh bilah kipas. Rekabentuk ini meningkatkan tork di bahagian kiri turbin angin dengan meningkatkan pekali seretan dan mengurangkan tork negatif rangka yang berputar berlawanan dengan angin pada bahagian lain. Dua jenis model berbentuk berlainan telah difabrikasi (bilah kipas rata dan bilah kipas berbentuk kaviti, dengan setiap jenis mempunyai dua model dengan bilangan rangka yang berlainan (berangka tiga dan berangka empat. Model-model telah diuji di dalam terowong angin dengan kelajuan angin yang berbeza bagi mendapatkan kesan rekabentuk, berat dan bilangan rangka ke atas pekali kuasa.KEYWORDS: design; wind turbine; drag coefficient; vane
Numerical study on small scale vertical axis wind turbine
Directory of Open Access Journals (Sweden)
Parra-Santos Teresa
2016-01-01
Full Text Available The performance of a Vertical Axis Wind Turbine (VAWT is numerically analyzed. The set-up is Hdarrieus with three straight blades airfoils NACA attached to a rotating vertical shaft. The wind turbine has solidity equals to the unity operating with wind velocity of 7 m/s. Influence of pitch angle is tested to get design tendencies. 2D, transient, Navier Stokes equations are solved using the code Ansys-Fluent. Conservation equations were solved with a Third-Order MUSCL scheme using SIMPLE to couple pressure and velocity. More than six revolutions must be simulated to get the periodic behavior. Two models of turbulence have been contrasted Realizable k-epsilon and Transition SST concluding the last one show more realistic flow features. Pitch angles of 0º, -6º and -10º have been tested with Tip Speed Ratios ranging from 0.7 and 1.6. The no null pitch angles improve the performance of the wind turbine. Instantaneous and averaged power coefficients as well as detailed flow field around the airfoils are showed.
NEAR WAKE OF A MODEL HORIZONTAL-AXIS WIND TURBINE
Institute of Scientific and Technical Information of China (English)
HU Dan-mei; DU Zhao-hui
2009-01-01
An experimental investigation on the properties of the near wake behind the rotor of a Horizontal-Axis Wind Turbine (HAWT) was carried out at model scale. Measurements were made with a stationary slanted hot-wire anemometer using the technique of phase-locked averaging. The primary aim is to study the formation and development of the three-dimensional wake. Five axial locations were chosen within four chord lengths of the blades over a range of tip speed ratios. The results show that during the downstream development of the wake, the wake centre traces a helical curve with its rotation direction opposite to that of the rotor. The distribution of mean velocity behind the HAWT rotor reveals an expansion and a decay of the three-dimensional wake. The shapes of the mean velocity distribution are similar along the blades span at the same downstream axial location. It is shown that the turbulence levels in the wake are higher than those in the non-wake region. The circumferential component and the radial component of the turbulence intensity are higher than the axial component. Our study offers some food of thought for better understanding of the physical features of the flow field as well as the performance of HAWT.
Differentially Rotating White Dwarfs I: Regimes of Internal Rotation
Ghosh, Pranab; Wheeler, J. Craig
2017-01-01
Most viable models of Type Ia supernovae (SNe Ia) require the thermonuclear explosion of a carbon/oxygen white dwarf that has evolved in a binary system. Rotation could be an important aspect of any model for SNe Ia, whether single or double degenerate, with the white dwarf mass at, below, or above the Chandrasekhar limit. Differential rotation is specifically invoked in attempts to account for the apparent excess mass in the super-Chandrasekhar events. Some earlier work has suggested that only uniform rotation is consistent with the expected mechanisms of angular momentum transport in white dwarfs, while others have found pronounced differential rotation. We show that if the baroclinic instability is active in degenerate matter and the effects of magnetic fields are neglected, both nearly uniform rotation and strongly differential rotation are possible. We classify rotation regimes in terms of the Richardson number, Ri. At small values of Ri ≤slant 0.1, we find both the low-viscosity Zahn regime with a nonmonotonic angular velocity profile and a new differential rotation regime for which the viscosity is high and scales linearly with the shear, σ. Employment of Kelvin–Helmholtz viscosity alone yields differential rotation. Large values of Ri ≫ 1 produce a regime of nearly uniform rotation for which the baroclinic viscosity is of intermediate value and scales as {σ }3. We discuss the gap in understanding of the behavior at intermediate values of Ri and how observations may constrain the rotation regimes attained by nature.
DEFF Research Database (Denmark)
Miles, James Edward
2016-01-01
Objective: To describe the effects of internal and external femoral rotation on radiographic measurements of the anatomical lateral distal femoral angle (a-LDFA) using two methods for defining the anatomical proximal femoral axis (a-PFA). Methods: Digital radiographs were obtained of 14 right fem...
Rotating Bullets from A Variable Protostar
Chen, Xuepeng; Zhang, Qizhou; Launhardt, Ralf; Henning, Thomas
2016-01-01
We present SMA CO(2-1) observations toward the protostellar jet driven by SVS13A, a variable protostar in the NGC1333 star-forming region. The SMA CO(2-1) images show an extremely high-velocity jet composed of a series of molecular 'bullets'. Based on the SMA CO observations, we discover clear and large systematic velocity gradients, perpendicular to the jet axis, in the blueshifted and redshifted bullets. After discussing several alternative interpretations, such as twin-jets, jet precession, warped disk, and internal helical shock, we suggest that the systematic velocity gradients observed in the bullets result from the rotation of the SVS13A jet. From the SMA CO images, the measured rotation velocities are 11.7-13.7 km/s for the blueshifted bullet and 4.7+/-0.5 km/s for the redshifted bullet. The estimated specific angular momenta of the two bullets are comparable to those of dense cores, about 10 times larger than those of protostellar envelopes, and about 20 times larger than those of circumstellar disks...
Strongly magnetized rotating dipole in general relativity
Pétri, J.
2016-10-01
Context. Electromagnetic waves arise in many areas of physics. Solutions are difficult to find in the general case. Aims: We numerically integrate Maxwell equations in a 3D spherical polar coordinate system. Methods: Straightforward finite difference methods would lead to a coordinate singularity along the polar axis. Spectral methods are better suited for such artificial singularities that are related to the choice of a coordinate system. When the radiating object rotates like a star, for example, special classes of solutions to Maxwell equations are worthwhile to study, such as quasi-stationary regimes. Moreover, in high-energy astrophysics, strong gravitational and magnetic fields are present especially around rotating neutron stars. Results: To study such systems, we designed an algorithm to solve the time-dependent Maxwell equations in spherical polar coordinates including general relativity and quantum electrodynamical corrections to leading order. As a diagnostic, we computed the spin-down luminosity expected for these stars and compared it to the classical or non-relativistic and non-quantum mechanical results. Conclusions: Quantum electrodynamics leads to an irrelevant change in the spin-down luminosity even for a magnetic field of about the critical value of 4.4 × 109 T. Therefore the braking index remains close to its value for a point dipole in vacuum, namely n = 3. The same conclusion holds for a general-relativistic quantum electrodynamically corrected force-free magnetosphere.
A rotating molecular jet in Orion
Zapata, Luis A; Muders, Dirk; Schilke, Peter; Menten, Karl; Guesten, Rolf
2009-01-01
We present CO(2-1), $^{13}$CO(2-1), CO(6-5), CO(7-6), and SO(6$_5-5_4$) line observations made with the {\\it IRAM 30 m} and {\\it APEX} radiotelescopes and the {\\it Submillimeter Array} toward the highly collimated and extended southwest lobe of the bipolar outflow {\\it Ori-S6} located in the Orion South region. We report, for all these lines, the detection of velocity asymmetries about the flow axis, with velocity differences roughly on the order of 1 km s$^{-1}$ over distances of about 5000 AU, 4 km s$^{-1}$ over distances of about 2000 AU, and close to the source of between 7 and 11 km s$^{-1}$ over smaller scales of about 1000 AU. We interpret these velocity differences as a signature of rotation but also discuss some alternatives which we recognize as unlikely in view of the asymmetries' large downstream continuation. This rotation across the {\\it Ori-S6} outflow is observed out to (projected) distances beyond 2.5 $\\times$ 10$^4$ AU from the flow's presumed origin. Comparison of our large-scale and small-...
Koishi, Hayato; Goto, Akira; Tanaka, Makoto; Omori, Yasushi; Futai, Kazuma; Yoshikawa, Hideki; Sugamoto, Kazuomi
2011-10-01
The purpose of this study was to assess accurately the three-dimensional movements of the scapula and humerus relative to the thorax during internal/external rotation motion with abduction of the shoulder joint. Ten right shoulders of ten healthy volunteers were examined using a wide-gantry open magnetic resonance imaging (MRI) system. MRI was performed every 30° from 90° external rotation to 90° internal rotation of the shoulder joint. The contribution ratio of the scapulothoracic joint was 12.5% about the long axis of the humerus during internal/external rotation motion. With arm position changes from 90° external rotation to 60° internal rotation, most movement was performed by the glenohumeral joint. Conversely, at internal rotation of ≥60°, the scapula began to markedly tilt in the anterior direction. At 90° internal rotation, the scapula was significantly tilted anteriorly (p specific scapulohumeral motion pattern, whereby the glenohumeral joint moves with internal rotation and the scapulothoracic joint moves with anterior tilt together with internal rotation motion of the shoulder joint.
Switchable polarization rotation of visible light using a plasmonic metasurface
Directory of Open Access Journals (Sweden)
Stuart K. Earl
2017-01-01
Full Text Available A metasurface comprising an array of silver nanorods supported by a thin film of the phase change material vanadium dioxide is used to rotate the primary polarization axis of visible light at a pre-determined wavelength. The dimensions of the rods were selected such that, across the two phases of vanadium dioxide, the two lateral localized plasmon resonances (in the plane of the metasurface occur at the same wavelength. Illumination with linearly polarized light at 45° to the principal axes of the rod metasurface enables excitation of both of these resonances. Modulating the phase of the underlying substrate, we show that it is possible to reversibly switch which axis of the metasurface is resonant at the operating wavelength. Analysis of the resulting Stokes parameters indicates that the orientation of the principal linear polarization axis of the reflected signal is rotated by 90° around these wavelengths. Dynamic metasurfaces such as these have the potential to form the basis of an ultra-compact, low-energy multiplexer or router for an optical signal.
Neuroanatomy and physiology of the avian hypothalamic/pituitary axis: clinical aspects.
Ritchie, Midge
2014-01-01
This article describes the anatomy of the avian hypothalamic/pituitary axis, the hypothalamic-pituitary-thyroid axis, the hypothalamic-pituitary-adrenal axis, the hypothalamic-pituitary-gonadal axis, the somatotrophic axis, and neurohypophysis.
Rotation and internal dynamics of terrestrial planets
Dehant, V.
2009-04-01
In the last decades, several missions and observations have brought new insight on the inner structure of the terrestrial planets. This information is a big challenge for the planet interior models; these data are also our best chance to improve our knowledge of the interior. Data obtained through new space missions are the basis of the future progress in this field. Classically, as done for the Earth, the interior models are constrained through seismic data provided from an extended network of seismometers. However, for planets, in the absence of such a network, gravitation and rotation studies are the most efficient ways to learn about the interior of the planets. Practically, our study is based on the analysis of the precise orbits of spacecrafts around the planets and on the positions of landers. Experiments on the planet Mars and Mercury will allow us to answer some of the most debated questions of the moment. On Mars, we plan in particular for the LaRa (Lander radioscience) instrument to be part of the Humboldt Payload (on the fixed platform lander) of the ExoMars ESA mission. LaRa is a coherent transponder using one uplink and one downlink in X-band. LaRa will measure the variation of Mars' rotation rate (related to the length-of-day) and the orientation of Mars' rotation axis in space (precession and nutations), by measuring Doppler shifts resulting from the motion of Mars relative to the Earth, through monitoring a radio signal between the ExoMars lander and the tracking stations from ESA (ESTRACK stations) and NASA (the Deep Space Network, DSN) on Earth. The primary objective of LaRa is a precise measurement of precession, nutations, and length-of-day. Comparing the data with theoretical modeling allows inferring knowledge on Mars' interior and on the global circulation in its atmosphere. Precession and nutations are induced by the well-known gravitational forcing of the Sun on Mars. Nutations depend on the internal properties of Mars, in particular on
CISM Course on Rotating Fluids
1992-01-01
The volume presents a comprehensive overview of rotation effects on fluid behavior, emphasizing non-linear processes. The subject is introduced by giving a range of examples of rotating fluids encountered in geophysics and engineering. This is then followed by a discussion of the relevant scales and parameters of rotating flow, and an introduction to geostrophic balance and vorticity concepts. There are few books on rotating fluids and this volume is, therefore, a welcome addition. It is the first volume which contains a unified view of turbulence in rotating fluids, instability and vortex dynamics. Some aspects of wave motions covered here are not found elsewhere.
Counter-Rotating Accretion Discs
Dyda, Sergei; Lovelace, Richard V. E.; Ustyugova, Galina V.; Romanova, Marina M.; Koldoba, Alexander V.
2014-01-01
Counter-rotating discs can arise from the accretion of a counter-rotating gas cloud onto the surface of an existing co-rotating disc or from the counter-rotating gas moving radially inward to the outer edge of an existing disc. At the interface, the two components mix to produce gas or plasma with zero net angular momentum which tends to free-fall towards the disc center. We discuss high-resolution axisymmetric hydrodynamic simulations of a viscous counter-rotating disc for cases where the tw...
Vibrational Suspension of Light Sphere in a Tilted Rotating Cylinder with Liquid
Directory of Open Access Journals (Sweden)
Victor G. Kozlov
2014-01-01
Full Text Available The dynamics of a light sphere in a quickly rotating inclined cylinder filled with liquid under transversal vibrations is experimentally investigated. Due to inertial oscillations of the sphere relative to the cavity, its rotation velocity differs from the cavity one. The intensification of the lagging motion of a sphere and the excitation of the outstripping differential rotation are possible under vibrations. It occurs in the resonant areas where the frequency of vibrations coincides with the fundamental frequency of the system. The position of the sphere in the center of the cylinder could be unstable. Different velocities of the sphere are matched with its various quasistationary positions on the axis of rotating cavity. In tilted rotating cylinder, the axial component of the gravity force appears; however, the light sphere does not float to the upper end wall but gets the stable position at a definite distance from it. It makes possible to provide a vibrational suspension of the light sphere in filled with liquid cavity rotating around the vertical axis. It is found that in the wide range of the cavity inclination angles the sphere position is determined by the dimensionless velocity of body differential rotation.
Khalil, Hossam; Kim, Dongkyu; Jo, Youngjoon; Park, Kyihwan
2017-06-01
An optical component called a Dove prism is used to rotate the laser beam of a laser-scanning vibrometer (LSV). This is called a derotator and is used for measuring the vibration of rotating objects. The main advantage of a derotator is that it works independently from an LSV. However, this device requires very specific alignment, in which the axis of the Dove prism must coincide with the rotational axis of the object. If the derotator is misaligned with the rotating object, the results of the vibration measurement are imprecise, owing to the alteration of the laser beam on the surface of the rotating object. In this study, a method is proposed for aligning a derotator with a rotating object through an image-processing algorithm that obtains the trajectory of a landmark attached to the object. After the trajectory of the landmark is mathematically modeled, the amount of derotator misalignment with respect to the object is calculated. The accuracy of the proposed method for aligning the derotator with the rotating object is experimentally tested.
AC electric field induced dipole-based on-chip 3D cell rotation.
Benhal, Prateek; Chase, J Geoffrey; Gaynor, Paul; Oback, Björn; Wang, Wenhui
2014-08-01
The precise rotation of suspended cells is one of the many fundamental manipulations used in a wide range of biotechnological applications such as cell injection and enucleation in nuclear transfer (NT) cloning. Noticeably scarce among the existing rotation techniques is the three-dimensional (3D) rotation of cells on a single chip. Here we present an alternating current (ac) induced electric field-based biochip platform, which has an open-top sub-mm square chamber enclosed by four sidewall electrodes and two bottom electrodes, to achieve rotation about the two axes, thus 3D cell rotation. By applying an ac potential to the four sidewall electrodes, an in-plane (yaw) rotating electric field is generated and in-plane rotation is achieved. Similarly, by applying an ac potential to two opposite sidewall electrodes and the two bottom electrodes, an out-of-plane (pitch) rotating electric field is generated and rolling rotation is achieved. As a prompt proof-of-concept, bottom electrodes were constructed with transparent indium tin oxide (ITO) using the standard lift-off process and the sidewall electrodes were constructed using a low-cost micro-milling process and then assembled to form the chip. Through experiments, we demonstrate rotation of bovine oocytes of ~120 μm diameter about two axes, with the capability of controlling the rotation direction and the rate for each axis through control of the ac potential amplitude, frequency, and phase shift, and cell medium conductivity. The maximum observed rotation rate reached nearly 140° s⁻¹, while a consistent rotation rate reached up to 40° s⁻¹. Rotation rate spectra for zona pellucida-intact and zona pellucida-free oocytes were further compared and found to have no effective difference. This simple, transparent, cheap-to-manufacture, and open-top platform allows additional functional modules to be integrated to become a more powerful cell manipulation system.
Angle calculations for a z-axis/(2S+2D) hybrid diffractometer
DEFF Research Database (Denmark)
Bunk, Oliver; Nielsen, Martin Meedom
2004-01-01
calculations are presented for a new 'hybrid' diffractometer consisting of a base instrument that can be combined with two different detector arms. With one of the detector arms, the instrument is a standard z-axis diffractometer as commonly used in surface studies. The other detector arm is designed...... for a heavy two-dimensional detector. The calculations are formulated in a general framework making it easy to incorporate, e. g. a second sample rotation stage, whereby it is possible to perform reflectivity and standard surface-crystallography measurements in the same geometry....
National Research Council Canada - National Science Library
Martens, Daan; Luesink, Mark; Huizenga, Henk; Pasma, Kasper L
2015-01-01
... in the calculated correction. The full rotational information available from CBCT imaging is not used. Neglecting a typical rotational setup error of 2° may cause up to 1.7 mm deviation at a distance of 50 mm from the isocenter. This can occur when the planning target volume (PTV) or an organ at risk (OAR) is located off‐axi...
An integrated MEMS piezoresistive tri-axis accelerometer
Yongping, Zhang; Changde, He; Jiaqi, Yu; Chunhui, Du; Juanting, Zhang; Xiujian, Chou; Wendong, Zhang
2013-10-01
An integrated MEMS accelerometer has been designed and fabricated. The device, which is based on the piezoresistive effect, accomplishes the detection of three components of acceleration by using piezoresistors to compose three Wheatstone bridges that are sensitive to the only given orientation. The fabrication of the accelerometer is described, and the theory behind its operation developed. Experimental results on sensitivity, cross-axis-coupling degree, and linearity are presented. The sensitivity of X, Y and Z were 5.49 mV/g, 5.12 mV/g and 4.82 mV/g, respectively; the nonlinearity of X, Y and Z were 0.01%, 0.04% and 0.01%, respectively; the cross-axis-coupling factor of X axis to Y axis and Z axis are 0.119% and 2.26% the cross-axis-coupling factor of Y axis to X axis and Z axis are 0.157% and 4.12% the cross-axis-coupling factor of Z axis to X axis and Y axis are 0.511% and 0.938%. The measured performance indexes attain accurate vector-detection in practical applications, and even at a navigation level. In conclusion, the accelerometer is a highly integrated sensor.
Anomalous Faraday rotation in the ISM/ICM
Medvedev, Mikhail V.
2016-10-01
Faraday effect is a common and useful way to deduce cosmic magnetic fields in the interstellar and intracluster media (ISM and ICM). Faraday rotation is the result of magnetically-induced birefringence in a dielectric medium causing a linearly polarized wave to suffer a rotation of its polarization axis as it traverses such a medium. However, the standard λ2-law of the rotation angle may not hold in strongly turbulent plasmas. Electromagnetic high-frequency and/or small-scale fluctuations may lead to effective collisionality with the pitch-angle diffusion coefficient being an effective ``quasi-collision'' frequency. Recently, we showed that quasi-collisionality may radically alter radiative transport properties of plasmas, such as absorption, transmission and reflection and other effects, which can be very important in laboratory and astrophysical plasmas. Here we briefly discuss the quasi-collisional generalization of the classical Faraday effect, which is drastically modified and can even become negative. Furthermore, we explore the origin of the long-known anomaly of Faraday rotation in a famous Cygnus regions. We argue that the anomaly can be due to the anomalous Faraday rotation in a thin ``blanket'' of turbulent plasma at the front of an interstellar bubble/shock. Supported by KU CLAS and DOE Grant ID0000225143 (07/01/16).
Energy Technology Data Exchange (ETDEWEB)
Hata, S., E-mail: hata.satoshi.207@m.kyushu-u.ac.jp [Department of Electrical and Materials Science, Kyushu University, Kasuga, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); Miyazaki, H. [Mel-Build, Nishi-ku, Fukuoka 819-0052 (Japan); Miyazaki, S. [FEI Company Japan Ltd., Minato-ku, Tokyo 108-0075 (Japan); Mitsuhara, M. [Department of Electrical and Materials Science, Kyushu University, Kasuga, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); Tanaka, M.; Kaneko, K.; Higashida, K. [Department of Materials Science and Engineering, Kyushu University, Nishi-ku, Fukuoka 819-0395 (Japan); Ikeda, K.; Nakashima, H. [Department of Electrical and Materials Science, Kyushu University, Kasuga, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); Matsumura, S. [Department of Applied Physics and Nuclear Engineering, Kyushu University, Nishi-ku, Fukuoka 819-0395 (Japan); Barnard, J.S. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Sharp, J.H. [Department of Materials Science and Engineering, Sir Robert Hadfield Building, Mappin Street, Sheffield, S1 3JD (United Kingdom); Midgley, P.A. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)
2011-07-15
Electron tomography requires a wide angular range of specimen-tilt for a reliable three-dimensional (3D) reconstruction. Although specimen holders are commercially available for tomography, they have several limitations, including tilting capability in only one or two axes at most, e.g. tilt-rotate. For amorphous specimens, the image contrast depends on mass and thickness only and the single-tilt holder is adequate for most tomographic image acquisitions. On the other hand, for crystalline materials where image contrast is strongly dependent on diffraction conditions, current commercially available tomography holders are inadequate, because they lack tilt capability in all three orthogonal axes needed to maintain a constant diffraction condition over the whole tilt range. We have developed a high-angle triple-axis (HATA) tomography specimen holder capable of high-angle tilting for the primary horizontal axis with tilting capability in the other (orthogonal) horizontal and vertical axes. This allows the user to trim the specimen tilt to obtain the desired diffraction condition over the whole tilt range of the tomography series. To demonstrate its capabilities, we have used this triple-axis tomography holder with a dual-axis tilt series (the specimen was rotated by 90{sup o} ex-situ between series) to obtain tomographic reconstructions of dislocation arrangements in plastically deformed austenitic steel foils. -- Highlights: {yields} A double tilt-rotate specimen holder for diffraction contrast imaging in electron tomography. {yields} Precise alignment of a diffraction condition for tilt-series acquisition of TEM/STEM images. {yields} Complete visualization of 3D dislocation arrangements by dual-axis STEM tomography.
In vivo movement of femoral flexion axis of a single-radius total knee arthroplasty.
Shimizu, Norimasa; Tomita, Tetsuya; Yamazaki, Takaharu; Yoshikawa, Hideki; Sugamoto, Kazuomi
2014-12-01
The objective of this study was to investigate in vivo femoro-tibial motion using the movement of femoral flexion axis of a single-radius TKA. We examined 20 clinically successful knees with a single-radius posterior stabilized TKA to evaluate the kinematics of deep knee flexion using 2-3-dimensional registration techniques. The mean knee flexion range of motion was 117.8°. The mean rotation of the femoral component was 7.6° external rotation. The mean knee flexion angle at initial post-cam engagement was 55.2°. No paradoxical movement of femoral component was shown until 70° flexion, afterward the femoral component rolled back with flexion. The data showed that the design of this prosthesis might contribute to reduce the paradoxical anterior femoral movement and provide stability in mid-flexion ranges.
Brown, Gerald V.; Kascak, Albert F.; Jansen, Ralph H.; Dever, Timothy P.; Duffy, Kirsten P.
2006-01-01
For magnetic-bearing-supported high-speed rotating machines with significant gyroscopic effects, it is necessary to stabilize forward and backward tilt whirling modes. Instability or low damping of these modes can prevent the attainment of desired shaft speed. We show analytically that both modes can be stabilized by using cross-axis proportional gains and high- and low-pass filters in the magnetic bearing controller. Furthermore, at high shaft speeds, where system phase lags degrade the stability of the forward-whirl mode, a phasor advance of the control signal can partially counteract the phase lag. In some range of high shaft speed, the derivative gain for the tilt modes (essential for stability for slowly rotating shafts) can be removed entirely. We show analytically how the tilt eigenvalues depend on shaft speed and on various controller feedback parameters.
NIMROD validation using 3-axis probe data from the TCSU experiment
Milroy, Richard; Velas, Katherine
2013-10-01
Recent analysis the data from a 3-axis translatable magnetic probe on the TCSU experiment has revealed new details of the magnetic structure of rotating magnetic field (RMF) sustained FRCs. This data was acquired from TCSU just prior to its shutdown in 2011. This analysis which reveals the 3D structure of the magnetic field shows the field lines are opened and relatively short with even-parity current drive, but can be much longer with odd-parity current drive. A torque analysis has revealed new details about the flow of magnetic torque due to both the RMF field and the steady component of the field. This detailed magnetic data provides a good platform for the validation of numerical simulations, and will be compared with predictions from the NIMROD code, which has been adapted to simulate the formation and sustainment of FRCs using Rotating Magnetic Fields (RMF).
EVALUATION OF PERFORMANCE OF HORIZONTAL AXIS WIND TURBINE BLADES BASED ON OPTIMAL ROTOR THEORY
Directory of Open Access Journals (Sweden)
Nitin Tenguria
2011-01-01
Full Text Available Wind energy is a very popular renewable energy resource. In order to increase the use of wind energy, it is important to develop wind turbine rotor with high rotations rates and power coefficient. In this paper, a method for the determination of the aerodynamic performance characteristics using NACA airfoils is given for three bladed horizontal axis wind turbine. Blade geometry is obtained from the best approximation of the calculated theoretical optimum chord and twist distribution of the rotating blade. Optimal rotor theory is used, which is simple enough and accurate enough for rotor design. In this work, eight different airfoils are used to investigate the changes in performance of the blade. Rotor diameter taken is 82 m which is the diameter of VESTAS V82-1.65MW. The airfoils taken are same from root to tip in every blade. The design lift coefficient taken is 1.1. A computer program is generated to automate the complete procedure.
EVALUATION OF PERFORMANCE OF HORIZONTAL AXIS WIND TURBINE BLADES BASED ON OPTIMAL ROTOR THEORY
Directory of Open Access Journals (Sweden)
Nitin Tenguria
2011-06-01
Full Text Available Wind energy is a very popular renewable energy resource. In order to increase the use of wind energy, it is important to develop wind turbine rotor with high rotations rates and power coefficient. In this paper, a method for the determination of the aerodynamic performance characteristics using NACA airfoils is given for three bladed horizontal axis wind turbine. Blade geometry is obtained from the best approximation of the calculated theoretical optimum chord and twist distribution of the rotating blade. Optimal rotor theory is used, which is simple enough and accurate enough for rotor design. In this work, eight different airfoils are used to investigate the changes in performance of the blade. Rotor diameter taken is 82 m which is the diameter of VESTAS V82-1.65MW. The airfoils taken are same from root to tip in every blade. The design lift coefficient taken is 1.1. A computer program is generated to automate the complete procedure.
Rotation at 1122 Hz and the neutron star structure
Bejger, M; Zdunik, J L
2006-01-01
Recent observations of XTE J1739-285 suggest that it contains a neutron star rotating at 1122 Hz. Such rotation imposes bounds on the structure of neutron star in XTE J1739-285. These bounds may be used to constrain poorly known equation of state of dense matter. One-parameter families of stationary configurations rotating rigidly at 1122 Hz are constructed, using a precise 2-D code solving Einstein equations. Hydrostatic equilibrium solutions are tested for stability with respect to axi-symmetric perturbations. A set of ten diverse EOSs of neutron stars is considered. Hypothetical strange stars are also studied. For each EOS, the family of possible neutron star models is limited by the mass shedding limit, corresponding to maximum allowed equatorial radius, R_max, and by the instability with respect to the axi-symmetric perturbations, reached at the minimum allowed equatorial radius, R_min. We get R_min \\simeq 10-13km, and R_max \\simeq 16-18km, with allowed mass 1.4-2.3 M_\\odot. Allowed stars with hyperonic ...
Study on Parallel 2-DOF Rotation Machanism in Radar
Jiang, Ming; Hu, Xuelong; Liu, Lei; Yu, Yunfei
The spherical parallel machine has become the world's academic and industrial focus of the field in recent years due to its simple and economical manufacture as well as its structural compactness especially suitable for areas where space gesture changes. This paper dwells upon its present research and development home and abroad. The newer machine (RGRR-II) can rotate around the axis z within 360° and the axis y1 from -90° to +90°. It has the advantages such as less moving parts (only 3 parts), larger ratio of work space to machine size, zero mechanic coupling, no singularity. Constructing rotation machine with spherical parallel 2-DOF rotation join (RGRR-II) may realize semispherical movement with zero dead point and extent the range. Control card (PA8000NT Series CNC) is installed in the computer. The card can run the corresponding software which realizes radar movement control. The machine meets the need of radars in plane and satellite which require larger detection range, lighter weight and compacter structure.
Predicted rotation signatures in MHD disc winds and comparison to DG Tau observations
Pesenti, N; Cabrit, S; Ferreira, J; Casse, F; García, P; O'Brien, D
2004-01-01
Motivated by the first detections of rotation signatures in the DG Tau jet (Bacciotti et al. 2002), we examine possible biases affecting the relation between detected rotation signatures and true azimuthal velocity for self-similar MHD disc winds, taking into account projection, convolution as well as excitation gradients effects. We find that computed velocity shifts are systematically smaller than the true underlying rotation curve. When outer slower streamlines dominate the emission, we predict observed shifts increasing with transverse distance to the jet axis, opposite to the true rotation profile. Determination of the full transverse rotation profile thus requires high angular resolution observations ( 50) are ruled out for the medium-velocity component in the DG Tau jet.
Predicted rotation signatures in MHD disc winds and comparison to DG Tau observations.
Pesenti, N.; Dougados, C.; Cabrit, S.; Ferreira, J.; Casse, F.; Garcia, P.; O'Brien, D.
2004-03-01
Motivated by the first detections of rotation signatures in the DG Tau jet (Bacciotti et al. \\cite{bacciotti2002}), we examine possible biases affecting the relation between detected rotation signatures and true azimuthal velocity for self-similar MHD disc winds, taking into account projection, convolution as well as excitation gradients effects. We find that computed velocity shifts are systematically smaller than the true underlying rotation curve. When outer slower streamlines dominate the emission, we predict observed shifts increasing with transverse distance to the jet axis, opposite to the true rotation profile. Determination of the full transverse rotation profile thus requires high angular resolution observations ( 50) are ruled out for the medium-velocity component in the DG Tau jet.
The global rotating scalar field vacuum on anti-de Sitter space–time
Directory of Open Access Journals (Sweden)
Carl Kent
2015-01-01
Full Text Available We consider the definition of the global vacuum state of a quantum scalar field on n-dimensional anti-de Sitter space–time as seen by an observer rotating about the polar axis. Since positive (or negative frequency scalar field modes must have positive (or negative Klein–Gordon norm respectively, we find that the only sensible choice of positive frequency corresponds to positive frequency as seen by a static observer. This means that the global rotating vacuum is identical to the global nonrotating vacuum. For n≥4, if the angular velocity of the rotating observer is smaller than the inverse of the anti-de Sitter radius of curvature, then modes with positive Klein–Gordon norm also have positive frequency as seen by the rotating observer. We comment on the implications of this result for the construction of global rotating thermal states.
Exact two-dimensionalization of rapidly rotating large-Reynolds-number flows
Gallet, Basile
2015-01-01
We consider the flow of a Newtonian fluid in a three-dimensional domain, rotating about a vertical axis and driven by a vertically invariant horizontal body-force. This system admits vertically invariant solutions that satisfy the 2D Navier-Stokes equation. At high Reynolds number and without global rotation, such solutions are usually unstable to three-dimensional perturbations. By contrast, for strong enough global rotation, we prove rigorously that the 2D (and possibly turbulent) solutions are stable to vertically dependent perturbations: the flow becomes 2D in the long-time limit. These results shed some light on several fundamental questions of rotating turbulence: for arbitrary Reynolds number and small enough Rossby number, the system is attracted towards purely 2D flow solutions, which display no energy dissipation anomaly and no cyclone-anticyclone asymmetry. Finally, these results challenge the applicability of wave turbulence theory to describe stationary rotating turbulence in bounded domains.
The rotating scalar field vacuum on anti-de Sitter space-time
Kent, Carl
2015-01-01
We consider the definition of the vacuum state of a quantum scalar field on $n$-dimensional anti-de Sitter space-time as seen by an observer rotating about the polar axis. Since positive (or negative) frequency scalar field modes must have positive (or negative) Klein-Gordon norm respectively, we find that the only sensible choice of positive frequency corresponds to positive frequency as seen by a static observer. This means that the rotating vacuum is identical to the nonrotating vacuum. If the angular velocity of the rotating observer is smaller than the inverse of the anti-de Sitter radius of curvature, then modes with positive Klein-Gordon norm also have positive frequency as seen by the rotating observer. We comment on the implications of this result for the construction of rotating thermal states.
Luyten, P. J.
1988-02-01
The oscillations and stability of a homogeneous self-gravitating rotating cylinder in a toroidal magnetic field are investigated. It is assumed that the field is proportional to the distance to the axis of the cylinder. We show the existence of four infinite discreta spectra of magnetic (or rotational) modes. Rotation stabilizes the magnetic m = 1 instability. The magnetic field decreases the growth rate of rotational instability and reduces the interval of unstable wavenumbers. If m = 1, instability always occurs with the exception of the equipartition state. If m> 1, the instability can be suppressed by a sufficiently large magnetic field. Resistivity decreases the growth rate of magnetic instability, but increases the growth rate of rotational instability. For zero wavenumber perturbations secular instability occurs due to the action of resistivity before a neutral point is attained where a second secular instabiliity initiates due to the action of resistivity
Cetera, Maureen; Ramirez-San Juan, Guillermina R; Oakes, Patrick W; Lewellyn, Lindsay; Fairchild, Michael J; Tanentzapf, Guy; Gardel, Margaret L; Horne-Badovinac, Sally
2014-01-01
Tissues use numerous mechanisms to change shape during development. The Drosophila egg chamber is an organ-like structure that elongates to form an elliptical egg. During elongation the follicular epithelial cells undergo a collective migration that causes the egg chamber to rotate within its surrounding basement membrane. Rotation coincides with the formation of a 'molecular corset', in which actin bundles in the epithelium and fibrils in the basement membrane are all aligned perpendicular to the elongation axis. Here we show that rotation plays a critical role in building the actin-based component of the corset. Rotation begins shortly after egg chamber formation and requires lamellipodial protrusions at each follicle cell's leading edge. During early stages, rotation is necessary for tissue-level actin bundle alignment, but it becomes dispensable after the basement membrane is polarized. This work highlights how collective cell migration can be used to build a polarized tissue organization for organ morphogenesis.
Effect of steady rotation on low Reynolds number vortex shedding behind a circular cylinder
Satish, Paluri; Patwardhan, Saurabh S.; Ramesh, O. N.
2013-08-01
In this paper control of oblique vortex shedding in the wake behind a straight circular cylinder is explored experimentally and computationally. Towards this, steady rotation of the cylinder about its axis is used as a control device. Some limited studies are also performed with a stepped circular cylinder, where at the step the flow is inevitably three-dimensional irrespective of the rotation rate. When there is no rotation, the vortex shedding pattern is three dimensional as described in many previous studies. With a non-zero rotation rate, it is demonstrated experimentally as well as numerically that the shedding pattern becomes more and more two-dimensional. At sufficiently high rotation rates, the vortex shedding is completely suppressed.
Institute of Scientific and Technical Information of China (English)
李林娟; 郑金海; 彭于轩; 张继生; 吴修广
2015-01-01
Horizontal axis tidal turbines have attracted more and more attentions nowadays, because of their convenience and low expense in construction and high efficiency in extracting tidal energy. The present study numerically investigates the flow motion and performance of a horizontal axis tidal turbine with a supporting vertical cylinder under steady current. In the numerical model, the continuous equation and incompressible Reynolds-averaged Navier-Stokes equations are solved, and the volume of fluid method is employed to track free surface motion. The RNG k-εmodel is adopted to calculate turbulence transport while the fractional area/volume obstacle representation method is used to describe turbine characteristics and movement. The effects of installation elevation of tidal turbine and inlet velocity on the water elevation, and current velocity, rotating speed and resultant force on turbine are discussed. Based on the comparison of the numerical results, a better understanding of flow structure around horizontal axis tidal turbine and turbine performance is achieved.
Le Doeuff, René
2013-01-01
In this book a general matrix-based approach to modeling electrical machines is promulgated. The model uses instantaneous quantities for key variables and enables the user to easily take into account associations between rotating machines and static converters (such as in variable speed drives). General equations of electromechanical energy conversion are established early in the treatment of the topic and then applied to synchronous, induction and DC machines. The primary characteristics of these machines are established for steady state behavior as well as for variable speed scenarios. I
Optical fiber rotation sensing
Burns, William K; Kelley, Paul
1993-01-01
Optical Fiber Rotation Sensing is the first book devoted to Interferometric Fiber Optic Gyros (IFOG). This book provides a complete overview of IFOGs, beginning with a historical review of IFOG development and including a fundamental exposition of basic principles, a discussion of devices and components, and concluding with industry reports on state-of-the-art activity. With several chapters contributed by principal developers of this solid-state device, the result is an authoritative work which will serve as the resource for researchers, students, and users of IFOGs.* * State-of-t
Zeps, Dainis
2009-01-01
Using a notation of corner between edges when graph has a fixed rotation, i.e. cyclical order of edges around vertices, we define combinatorial objects - combinatorial maps as pairs of permutations, one for vertices and one for faces. Further, we define multiplication of these objects, that coincides with the multiplication of permutations. We consider closed under multiplication classes of combinatorial maps that consist of closed classes of combinatorial maps with fixed edges where each such class is defined by a knot. One class among them is special, containing selfconjugate maps.
2014-01-01
The report presents a methodology to determine the directions of the stiffness principal axis (in this case subject to the linear displacement and forced rotation angle) of a solid object interact with the surrounding environment by resilient bearing supports. The results also show that determining the coordinates of the stiffness center in the vibrating system with damping factors is necessary in our research.
Dikpati, Mausumi
2013-01-01
Meridional circulation in stellar convection zones is not generally well observed, but may be critical for MHD dynamos. Coriolis forces from differential rotation (DR) play a large role in determining what the meridional circulation is. Here we consider whether a stellar DR that is constant on cylinders concentric with the rotation axis can drive a meridional circulation.Conventional wisdom says that it can not. Using two related forms of governing equations that respectively estimate the longitudinal components of the curl of meridional mass flux and the vorticity, we show that such DR will drive a meridional flow. This is because to satisfy anelastic mass conservation, non-spherically symmetric pressure contours must be present for all DRs, not just ones that depart from constancy on cylinders concentric with the rotation axis. Therefore the fluid is always baroclinic if DR is present, because, in anelastic systems, the perturbation pressure must satisfy a Poisson type equation, as well as an equation of st...
An automatic registration system of multi-view 3D measurement data using two-axis turntables
He, Dong; Liu, Xiaoli; Cai, Zewei; Chen, Hailong; Peng, Xiang
2016-09-01
Automatic registration is a key researcher issue in 3D measurement field. In this work, we developed the automatic registration system, which is composed of a stereo system with structured light and two axis turntables. To realize the fully automatically 3D point registration, the novel method is proposed for calibration the stereo system and the two turntable direction vector simultaneously. The plane calibration rig with marked points was placed on the turntable and was captured by the left and right cameras of the stereo system with different rotation angles of the two axis turntable. By the shot images, a stereo system (intrinsically and extrinsically) was calibrated with classics camera model, and reconstruction 3D coordinates of the marked points with different angle of the two turntable. The marked point in different angle posted the specific circle, and the normal line of the circle around the turntable axis direction vector. For the each turntable, different points have different circle and normal line, and the turntable axis direction vector is calculated by averaging the different normal line. And the result show that, the proposed registration system can precisely register point cloud under the different scanning angles. In addition, there are no the ICP iterative procedures, and that make it can be used in registration of the point cloud without the obvious features like sphere, cylinder comes and the other rotator.
The optical axis optimization in measurement of decentration of lens
Wang, Yajing; Yang, Lin; Wang, Chunyu
2013-09-01
Measure of optical decentration plays an important role in inspection, installation and adjustment of optical system. This article describes optical measurement principle of decentration, analyzes the reason of the decentration measurement accuracy, and indicates the necessity of optimizing the optical axis. Finally, because of the error of the decentration optical axis fitting. A new method of optical axis optimization is put forward here. A mathematical model to find the best optical axis is established, which improved the optical performance of the system.
Soft initial-rotation and HΦ robust constant rotational speed control for rotational MEMS gyro
Institute of Scientific and Technical Information of China (English)
Ma Gaoyin; Chen Wenyuan; Cui Feng; Zhang Weiping; Wang Liqi
2009-01-01
A novel soft initial-rotation control system and an Hoo robust constant rotational speed controller (RCRSC) for a rotational MEMS (micro-electro-mechanical system) gyro are presented. The soft initial-rotation control system can prevent the possible tumbling down of the suspended rotor and ensure a smooth and fast initial-rotation process. After the initial-rotation process, in order to maintain the rotational speed accurately constant, the RCRSC is acquired through the mixed sensitivity design approach. Simulation results show that the actuation voltage disturbances from the internal carrier waves in the gyro is reduced by more than 15.3 dB, and the speed fluctuations due to typical external vibrations ranging from 10 Hz to 200 Hz can also be restricted to 10-3 rad/s order.
Moore, K.; Chan, N. H.; Daradich, A.; Mitrovica, J. X.
2016-12-01
The long-term rotational stability of terrestrial planets is a classic problem in geophysics and planetary science. Modern theoretical treatments stem from Gold (1955) and Goldreich and Toomre (1969) who: (1) argued that the rotation axis orientation of terrestrial planets is inherently unstable since any stabilization due to the rotational bulge is transient; and (2) established conditions for rapid, large-scale reorientation of the axis relative to the surface geography (true polar wander, TPW). Willemann (1984) and Matsuyama et al. (2006) extended this work, demonstrating that an elastic lithosphere stabilizes the rotation axis through elastic stresses induced in the lithosphere by planetary reorientation. In this case, the magnitude of load-induced TPW can be significantly more muted. The above studies describe equilibrium theories concerned with the final state of the rotation axis. More recent studies (e.g., Ricard et al., 1993; Tsai & Stevenson, 2007; Harada, 2012; Chan et al., 2014) incorporate time dependence into the governing theory. We build on this earlier work to derive a new theory of time-dependent TPW on terrestrial planets with viscoelastic lithospheres. Our formalism more realistically models the time evolution of TPW by bridging the two end-member cases: an infinite viscosity (elastic) lithosphere; and a fully relaxed, finite viscosity lithosphere that provides no stabilization. On short timescales the rotation axis is stabilized by the lithosphere (the Willemann case), but on timescales longer than the relaxation time of the lithosphere the axis becomes unstable (the Gold case). We illustrate our theory with numerical simulations for Mars. Published work suggests that Martian TPW would not continue for any significant time after the addition of a load, and thus that an equilibrium theory is adequate. Our results demonstrate, in contrast, that the slow relaxation of a high viscosity lithosphere can lead to TPW on Mars that continues for billions
Observation of Central Toroidal Rotation Induced by ICRF on EAST
Pan, Xiayun; Wang, Fudi; Zhang, Xinjun; Lyu, Bo; Chen, Jun; Li, Yingying; Fu, Jia; Shi, Yuejiang; Yu, Yi; Ye, Minyou; Wan, Baonian
2016-02-01
Core plasma rotation of both L-mode and H-mode discharges with ion cyclotron range of frequency (ICRF) minority heating (MH) scheme was measured with a tangential X-ray imaging crystal spectrometer on EAST (Experimental Advanced Superconducting Tokamak). Co-current central impurity toroidal rotation change was observed in ICRF-heated L- and H-mode plasmas. Rotation increment as high as 30 km/s was generated at ∼1.7 MW ICRF power. Scaling results showed similar trend as the Rice scaling but with significant scattering, especially in L-mode plasmas. We varied the plasma current, toroidal field and magnetic configuration individually to study their effect on L-mode plasma rotation, while keeping the other major plasma parameters and heating unchanged during the scanning. It was found that larger plasma current could induce plasma rotation more efficiently. A scan of the toroidal magnetic field indicated that the largest rotation was obtained for on-axis ICRF heating. A comparison between lower-single-null (LSN) and double-null (DN) configurations showed that LSN discharges rendered a larger rotation change for the same power input and plasma parameters. supported by the National Magnetic Confinement Fusion Science Program of China (Nos. 2013GB112004 and 2015GB103002), National Natural Science Foundation of China (Nos. 11175208, 11305212, 11375235, 11405212 and 11261140328), the Innovative Program of Development Foundation of Hefei Center for Physical Science and Technology (2014FXCX003) and Brain Korea 21 Program for Leading Universities & Students (BK21 PLUS)
Physics of Rotating and Expanding Black Hole Universe
Directory of Open Access Journals (Sweden)
Seshavatharam U. V. S.
2010-04-01
Full Text Available Throughout its journey universe follows strong gravity. By unifying general theory of relativity and quantum mechanics a simple derivation is given for rotating black hole’s temperature. It is shown that when the rotation speed approaches light speed temperature approaches Hawking’s black hole temperature. Applying this idea to the cosmic black hole it is noticed that there is “no cosmic temperature” if there is “no cosmic rotation”. Starting from the Planck scale it is assumed that- universe is a rotating and expanding black hole. Another key assumption is that at any time cosmic black hole rotates with light speed. For this cosmic sphere as a whole while in light speed rotation “rate of decrease” in temperature or “rate of increase” in cosmic red shift is a measure of “rate of cosmic expansion”. Since 1992, measured CMBR data indicates that, present CMB is same in all directions equal to 2 : 726 K ; smooth to 1 part in 100,000 and there is no continuous decrease! This directly indicates that, at present rate of decrease in temperature is practically zero and rate of expansion is practically zero. Universe is isotropic and hence static and is rotating as a rigid sphere with light speed. At present galaxies are revolving with speeds proportional to their distances from the cosmic axis of rotation. If present CMBR temperature is 2 : 726 K, present value of obtained angular velocity is 2 : 17 10 Present cosmic mass density and cosmic time are fitted with a ln ( volume ratio parameter. Finally it can be suggested that dark matter and dark energy are ad-hoc and misleading concepts.
Lombard, Jean-Eloi; Xu, Hui; Moxey, Dave; Sherwin, Spencer
2016-11-01
For open wheel race-cars, such as Formula One, or IndyCar, the wheels are responsible for 40 % of the total drag. For road cars, drag associated to the wheels and under-carriage can represent 20 - 60 % of total drag at highway cruise speeds. Experimental observations have reported two, three or more pairs of counter rotating vortices, the relative strength of which still remains an open question. The near wake of an unsteady rotating wheel. The numerical investigation by means of direct numerical simulation at ReD =400-1000 is presented here to further the understanding of bifurcations the flow undergoes as the Reynolds number is increased. Direct numerical simulation is performed using Nektar++, the results of which are compared to those of Pirozzoli et al. (2012). Both proper orthogonal decomposition and dynamic mode decomposition, as well as spectral analysis are leveraged to gain unprecedented insight into the bifurcations and subsequent topological differences of the wake as the Reynolds number is increased.
Bambi, Cosimo
2013-01-01
The formation of spacetime singularities is a quite common phenomenon in General Relativity and it is regulated by specific theorems. It is widely believed that spacetime singularities do not exist in Nature, but that they represent a limitation of the classical theory. While we do not yet have any solid theory of quantum gravity, toy models of black hole solutions without singularities have been proposed. So far, there are only non-rotating regular black holes in the literature. These metrics can be hardly tested by astrophysical observations, as the black hole spin plays a fundamental role in any astrophysical process. In this letter, we apply the Newman-Janis algorithm to the Hayward and to the Bardeen black hole metrics. In both cases, we obtain a family of rotating solutions. Every solution corresponds to a different matter configuration. Each family has one solution with special properties, which can be written in Kerr-like form in Boyer-Lindquist coordinates. These special solutions are of Petrov type ...