Opposite Rotation Research Articles

Steady vortex patches with opposite rotation directions in a planar ideal fluid

In this paper we consider steady vortex solutions for the ideal incompressible Euler equation in a planar bounded domain. By solving a variational problem for the vorticity, we construct steady vortex patches with opposite rotation directions concentrated at a strict local minimum point of the Kirchhoff–Routh function with $$k=2$$ . Moreover, we show that such steady vortex patches are in fact local maximizers of the kinetic energy among isovortical patches, which correlates stability to uniqueness.

MHD swirling flow and heat transfer in Maxwell fluid driven by two coaxially rotating disks with variable thermal conductivity

We develop a mathematical modeling for an electrically conducting non-Newtonian Maxwell fluid flow occurring between two coaxially parallel stretchable rotating disks at constant distant apart. The pressure and heat transfer analysis is carried out subject to the effects of axial magnetic field and temperature dependent thermal conductivity. The stretching and rotating rates of both disks are assumed different from each other. The two diverse phenomena, such as, when both disks are rotating with different angular velocities in the same as well as in the opposite directions are discussed. The similarity procedure adopted by von Kármán is utilized to reduce the governing momentum and energy equations into nonlinear ordinary differential equations. The solution of the governing problem is obtained numerically using bvp4c scheme in Matlab. The effects of active parameters including stretching rates, Deborah number, magnetic number, Prandtl number, thermal conductivity parameter and Reynolds number are examined for same as well as opposite rotation direction for radial, azimuthal, and axial flows, pressure and temperature fields. The classical flow pattern happening between the disks is significantly altered by the stretching action which is a main physical significances of this study. The azimuthal flow is observed higher for the same direction of disks rotation as compared to opposite disks rotation. The pressure field drops near the lower disk with increasing values of Reynolds number. The role of thermal conductivity parameter is quite useful to enhance the fluid temperature.

Effect of vane sweep angle on vortex generator wake

The effect of varying the vane sweep angle of different vortex generators (VGs) on the statistics of the wake flow and the coherent structures was investigated. Pairs of rectangular, trapezoid, and delta vanes with sweep angle varying in ascending order were arranged at an equal but opposite angle with respect to the flow. A single rectangular vane was also investigated to identify the effect of vane pairing. The VGs were installed in the thin laminar boundary layer of a flat plate at Reynolds number of 930, based on VG height and free-stream velocity. Time-resolved tomographic particle image velocimetry (tomo-PIV) was carried out in a volume covering the wake, and stereo-PIV was applied to two cross-flow planes of the wake. The measurements showed two counter-rotating streamwise vortices, which induce a strong upward motion along the centerline of the wake. A pair of secondary counter-rotating streamwise vortices were also observed. The single rectangular vane showed a primary streamwise vortex and a weaker secondary streamwise vortex with opposite rotation. The evaluation of wall-normal momentum transport along the wake centerline showed that the paired configuration enhanced flow mixing. The investigation of the instantaneous coherent structures and proper-orthogonal-decomposition of the three-dimensional velocity fluctuations indicated that the coherence and strength of the vortices were inversely proportional to the sweep angle of the VG. The delta vane VG, with the largest sweep angle, produced more small-scale turbulence while the rectangular VG, with an upswept vane, produced the most coherent streamwise vortices. The investigation of wall-normal momentum transport showed that the rectangular VG had the best performance in improving flow mixing, followed by the trapezoidal, single rectangular, and delta VG. When evaluating the performance of VG using the ratio of mixing enhancement over drag, the trapezoidal VG was the most efficient one. The investigation confirmed the possibility of lowering the device drag while maintaining the effectiveness of VG using an optimum sweep angle. The performance of delta VG was about 60% of the trapezoidal VG, which suggests a large sweep angle can adversely affect the VG performance.

Implementation of Flat Gain Broadband Power Amplifier With Impedance Rotation Compensation

The conventional broadband impedance matching network in low-pass structure cannot present adequate broadband impedance rotation for the optimum broadband operation of the power amplifier (PA), resulting in performance variations and degradations. The underlying constraint is the phenomenon of opposite impedance rotation. Against such a backdrop, this paper presents a methodology using the band-pass topology to compensate the frequency-variable response of the PA. The CGH40010F from Cree is used to verify the effectiveness of this compensation method. The experimental results are in good agreement with the simulation. The proposed PA yields good gain flatness (±0.5 dB), input/output return loss (>13 dB), and high power added efficiency (>60 %) over the band from 1.7 to 2.7 GHz. After digital predistortion, the measured adjacent channel power ratio is about −55 and −50 dBc at ±5 and ±10 MHz offset when the PA is driven by 5- and 10-MHz WCDMA signals at 6.5 ~ 7 dB power back-off.

Simple shear: eigenvectors of cauchy-green tensors rotate against each other

Simple shear represents a somewhat complex case of deformation although it is very good studied. In this paper, we discuss a new aspect of simple shear which has not been observed before. Rotations of the eigenvectors of the right and left Cauchy-Green tensors with increasing amount of shear under the kinematically defined simple shear are theoretically studied. An analysis has been done within a framework of the nonlinear theory of elasticity. Mathematical processor Maple is used for the calculations and animation of the results. Phenomena of mutually opposite rotations of the eigenvectors of the right and left Cauchy-Green tensors is fond that can be important for anisotropic and in particular fibre-reinforced materials. We studied rotations of principal strain directions under the kinematically defined simple shear. Accordingly, eigenvectors of the right and left Cauchy-Green tensors rotate against each other with the increasing amount of shear. Interestingly, the eigenvectors of b rotate in the same direction as line elements of the material while the eigenvectors of C in the opposite direction. For example, this can be important for anisotropic and in particular fiber reinforced materials. In this case, the direction of the maximal stretch will rotate with respect to reinforcement directions.

Evolution of calcite surface reconstruction and interface adsorption of calcite-CO2 with temperature

Molecular dynamics (MD) simulation was performed to research the effect of the various temperatures on the calcite (1 0 4) surface reconstruction and the interface adsorption behavior of CO2 molecules. It is found that the carbonate groups on the surface have opposite rotation directions and the parameters of surface structure are positively related to the temperature. The evolution of surface reconstruction is almost unchanged after the inflection point 673 K. Meanwhile calcite clusters structure should be formed at the crystal surface. According to the surface structure parameters and adsorption energy, the effect of CO2 molecules on surface structure is eliminated. In addition, CO2 molecules are adsorbed perpendicularly at the point of Ca ions by electrostatic interaction. And desorption of CO2 molecules is positively correlated with temperature.

Effect of geometry and fill level on the transport and mixing behaviour of a co-rotating twin screw extruder

The transport and mixing properties of a co-rotating twin screw extruder with both screw elements and kneading blocks are explored using the smoothed particle hydrodynamics method. The use of a Lagrangian method enables simulation of extruders partially or fully filled with fluid and is not limited by problems associated with extreme mesh deformation due to the opposite rotation of the impellors or the small gaps between them. The cross-channel and axial fluid transport and mixing in the screw elements and kneading blocks are analysed. The effect of parametric variations in both impeller elements on the nature of the fluid flow and the mixing are explored; specifically the effects of varying the screw pitch (positively correlated to mixing rate), kneading block stagger angle (the mixing rate peaks at a block angle of 30°) and gap size between the rotating elements (positively correlated to mixing rate). Flow and mixing behaviour is also investigated for partially filled cases, with a fill level of 50% producing the highest mixing rates for the screw elements. The presence of fluid free surfaces is shown as generally positive for mixing. We demonstrate significantly improved mixing when the orientation handedness of the screw and kneading blocks leads to concentration of fluid in the kneading elements.

Synthetic cADPR analogues may form only one of two possible conformational diastereoisomers

Cyclic adenosine 5′-diphosphate ribose (cADPR) is an emerging Ca2+-mobilising second messenger. cADPR analogues have been generated as chemical biology tools via both chemo-enzymatic and total synthetic routes. Both routes rely on the cyclisation of a linear precursor to close an 18-membered macrocyclic ring. We show here that, after cyclisation, there are two possible macrocyclic product conformers that may be formed, depending on whether cyclisation occurs to the “right” or the “left” of the adenine base (as viewed along the H-8 → C-8 base axis). Molecular modelling demonstrates that these two conformers are distinct and cannot interconvert. The two conformers would present a different spatial layout of binding partners to the cADPR receptor/binding site. For chemo-enzymatically generated analogues Aplysia californica ADP-ribosyl cyclase acts as a template to generate solely the “right-handed” conformer and this corresponds to that of the natural messenger, as originally explored using crystallography. However, for a total synthetic analogue it is theoretically possible to generate either product, or a mixture, from a given linear precursor. Cyclisation on either face of the adenine base is broadly illustrated by the first chemical synthesis of the two enantiomers of a “southern” ribose-simplified cIDPR analogue 8-Br-N9-butyl-cIDPR, a cADPR analogue containing only one chiral sugar in the “northern” ribose, i.e. 8-Br-D- and its mirror image 8-Br-L-N9-butyl-cIDPR. By replacing the D-ribose with the unnatural L-ribose sugar, cyclisation of the linear precursor with pyrophosphate closure generates a cyclised product spectroscopically identical, but displaying equal and opposite specific rotation. These findings have implications for cADPR analogue design, synthesis and activity.

Ab initio study of the structure, isotope effects, and vibrational properties in KDP crystals

The lattice dynamics of potassium dihydrogen phosphate (KDP) and its deuterated analog DKDP was studied via first-principles DFT calculations. A thorough assessment of the quality of a wide range of functionals supplemented with the approximate inclusion of quantum nuclear effects indicated that the nonlocal van der Waals functional vdW-DF [M. Dion et al., Phys. Rev. Lett. 92, 246401 (2004); J. Klime\ifmmode \check{s}\else \v{s}\fi{} et al., Phys. Rev. B 83, 195131 (2011)] produces the best agreement with structural data for both compounds. This enabled the calculation of full phonon dispersions in the ferroelectric phase, and hence the phonon density of states and specific heat, in very good agreement with experimental data. Phonon bands and especially modes at the $\mathrm{\ensuremath{\Gamma}}$ point of the Brillouin zone were classified according to their vibrational pattern. This allowed for the assignment of stretching and bending modes of the hydrogen bonds. Internal modes involving the phosphate units were identified at lower frequencies, while the lowest-lying modes were those involving the ${\mathrm{K}}^{+}$ ion. These assignments were used to interpret infrared and Raman spectra along the $c$ axis and in the perpendicular plane. Phonon modes calculated at the $\mathrm{\ensuremath{\Gamma}}$ point showed two types of instabilities. One was a normal mode polarized along the $c$ axis of the crystal, while the other corresponded to a twofold-degenerate mode polarized in the perpendicular plane. The former gives rise to a spontaneous polarization in the ferroelectric phase at low temperatures by coupling to an optical ${\mathrm{K}}^{+}\text{\ensuremath{-}}{\mathrm{H}}_{2}{\mathrm{PO}}_{4}^{\ensuremath{-}}$ stretching mode, consistently with a significant off-diagonal Born effective charge on the hydrogen atoms. A mode describing the opposite rotation of neighboring ${\mathrm{PO}}_{4}$ tetrahedra was also found to couple strongly to the ferroelectric mode, as this modulates the O-O distance, which determines the barrier for proton transfer. The present study suggests that a minimal model to describe isotope effects in KDP should involve at least three fully coupled vibrational modes.

An equatorial thermal wind equation: Applications to Jupiter

To relate the vertical wind shear to horizontal temperature gradients at and near the equator, we derive an “Equatorial Thermal Wind Equation” (EQTWE) using a minimum set of assumptions that are easily satisfied for the atmospheres of all the giant planets and Earth. Similar to the textbook Thermal Wind Equation (TWE), the EQTWE requires a small Rossby number, but the relevant Rossby number for the EQTWE depends on the velocity and length scales of the equatorial flows, and on the Coriolis parameter at the north pole (which is large), rather than the Coriolis parameter at the equator (which goes to zero). Unlike the TWE, the EQTWE is valid only for the east-west component of the wind. We apply the EQTWE to the Jovian wind measured by the Galileo probe Doppler wind experiment at jovicentric latitude 6.53°N (7.46°N jovigraphic), which is valid because the EQTWE is accurate at latitudes θ < 18°. Assuming that this wind profile holds at all longitudes, the EQTWE shows that near the equator at altitudes at 0.8 bar < P < 5 bar, the atmosphere is anomalously cool with respect to the surrounding flow, and at 5 bar ≤ P < 13 bar, it is warm. These anomalies imply adiabatic up-welling (down-welling) at 0.8 bar < P < 5 bar (at 5 bar ≤ P ≤ 13 bar), which suggests a Jovian global circulation model with two layers of Hadley cells, with an upper layer like the one on Earth, and the lower has cells with the opposite rotation. Applying the EQTWE to CIRS temperatures at altitudes above 330 mbar, shows that the large vertical wind shears measured by the Galileo probe extend to higher altitudes, and at 3 mbar create a stratospheric equatorial jet with a velocity of 205 m/s (almost 50% faster than the speed that had been obtained earlier with the TWE).

Magnetoelectricity in multiferroic hexaferrites as understood by crystal symmetry analyses

Magnetoelectric (ME) properties under rotating magnetic field H are comparatively investigated in two representative hexaferrites Y-type Ba0.5Sr1.5Zn2(Fe0.92Al0.08)12O22 and Z-type Ba0.52Sr2.48Co2Fe24O41, both of which have exhibited a similar transverse conical spin structure and giant ME coupling near room temperature. When the external H is rotated clockwise by 2pi, in-plane P vector is rotated clockwise by 2pi in the Y-type hexaferrite and counterclockwise by 4pi in the Z-type hexaferrite. A symmetry-based analysis reveals that the faster and opposite rotation of P vector in the Z-type hexaferrite is associated with the existence of a mirror plane perpendicular to c-axis. Moreover, such a peculiar crystal symmetry also results in contrasting microscopic origins for the spin-driven ferroelectricity; only the inverse DM interaction is responsible for the Y-type hexaferrite while additional p-d hybridization becomes more important in the Z-type hexaferrite. This work demonstrates the importance of the crystal symmetry in the determination of ME properties in the hexaferrites and provides a fundamental framework for understanding and applying the giant ME coupling in various ferrites with hexagonal crystal structure.

Gender-Specific Kinematics for Rotational Coordination Between Hips and Lumbar Spine During Downswing

The purpose of this study was to compare and evaluate the inter-joint coordination between the hips and lumbar spine in both male and female skilled golfers during the downswing phase. Six infrared MCAM2 cameras were used for capturing each participant’s swing motion. In order to evaluate the inter-joint coordination, kinematic data and continuous relative phase (CRP) were obtained during downswing phase. The lead hip-lumbar spine CRP in male golfers showed a typical parabola pattern with a minimum value at around 60% of the downswing phase. On the other hand, the CRP between the lead hip and lumbar spine of female golfers barely changed from the initial to middle downswing stages, and increased at the later stage. Male golfers typically used their lead hip more than their lumbar spine during the early downswing, while the rotational contribution of the lumbar spine and lead hip in female golfers were comparable until the middle of the downswing phase. These findings result from the opposite rotation of the lumbar spine for even the early downswing phase due to the muscular and articular flexibility of female golfers. This study has the potential to help develop gender-specific coaching materials for the improvement of swing skills.

Realization of photonic spin Hall effect by breaking the rotation symmetry of optical field in light–matter interaction

Photonic spin Hall effect (SHE) manifests itself as spin-dependent shift or splitting of a light beam, which is derived from spin–orbit interactions, and can be realized by breaking the rotation symmetry of light–matter interaction systems. Here, we demonstrate the observation of a photonic SHE by breaking the rotation symmetry of the optical field, while keeping the rotation symmetry of the inhomogeneous waveplate. The inhomogeneous waveplate constructed by dielectric nanostructures, introduces a spin-dependent Pancharatnam–Berry phase to the two spin components of the input beam, i.e., the left- and right-circular polarization components acquire exactly opposite vortex phases. During beam propagation, they experience opposite azimuthal rotations, and induce a four-lobe spin-dependent splitting in the azimuthal direction. In addition, the spin-dependent splitting becomes more evident upon beam propagation, and can be enhanced by increasing the topological orders of the nanostructures. For comparison, we also examine that no spin-dependent splitting can be observed when keeping the rotation symmetry of the incident optical field.

Interference between competing motor memories developed through learning with different limbs.

Learning from motor errors that occur across different limbs is essential for effective tool use, sports training, and rehabilitation. To probe the neural organization of error-driven learning across limbs, we asked whether learning opposing visuomotor mappings with the two arms would interfere. Young right-handers first adapted to opposite visuomotor rotations A and B with different arms and were then reexposed to A 24 h later. We observed that relearning of A was never faster nor were initial errors smaller than prior A learning, which would be expected if there was no interference from B. Rather, errors were greater than or similar to, and learning rate was slower than or comparable to, previous A learning depending on the order in which the arms learned. This indicated robust interference between the motor memories of A and B when they were learned with different arms in close succession. We then proceeded to uncover that the order-dependent asymmetry in performance upon reexposure resulted from asymmetric transfer of learning from the left arm to the right but not vice versa and that the observed interference was retrograde in nature. Such retrograde interference likely occurs because the two arms require the same neural resources for learning, a suggestion consistent with that of our past work showing impaired learning following left inferior parietal damage regardless of the arm used. These results thus point to a common neural basis for formation of new motor memories with different limbs and hold significant implications for how newly formed motor memories interact. NEW & NOTEWORTHY In a series of experiments, we demonstrate robust retrograde interference between competing motor memories developed through error-based learning with different arms. These results provide evidence for shared neural resources for the acquisition of motor memories across different limbs and also suggest that practice with two effectors in close succession may not be a sound approach in either sports or rehabilitation. Such training may not allow newly acquired motor memories to be stabilized.

SIMULASI NUMERIK PADA DIFFUSER AUGMENTED WIND TURBINES DENGAN ROTOR GANDA KONTRA ROTASI

Wind energy is one form of renewable energy in Indonesia and its potential is very large to be utilized. Wind energy can be converted into electrical energy using wind turbines. Horizontal axis wind turbine will be the subject of this study, where the wind turbine model will be given additional diffuser. In addition, this wind turbine model will also be developed from a single rotor wind turbine into a double rotor wind turbine with opposite rotation direction or counter rotation. This research uses numerical simulation method using ANSYS Fluent software to know wind turbine performance. Simulations were performed at wind speeds of 3 m/s, with the ratio of the length and diameter of the inlet diffuser 0.5; 1; 1.5; 2; and 2.5. Based on the simulation results, it can be seen that the greater the ratio of inlet length and diameter, the mechanical power generated by the wind turbine rotor is greater. Double rotor wind turbine with a length ratio and 2.5 inlet diameter produces the highest performance on the front rotor and rotor rear. The greater the ratio of the length and diameter of the inlet, the mechanical power generated by the front rotor and the rotor inside the diffuser also increases.

Aerodynamics of a Wing with a Wingtip Flapper

In the present study, an oscillating membrane flapper was pivotally attached to the tip of a conventional rigid wing. Stroke-averaged aerodynamic forces were measured for the range of the flapping frequency, showing significant increases in the lift coefficient and lift-to-drag ratio for the wing with a flapper. Major vortex patterns were deduced from observations of smoke-wire visualization and 2D phase-locked particle image velocimetry (PIV). The centerline of the primary vortex wanders in the counterclockwise direction. On the contrary, its core rotates in the same sense of rotation as a wingtip vortex in a conventional wing. The secondary weaker vortex of opposite rotation lasts for a half stroke. The vortex ring sheds from the flapper during the second half of the upstroke and pronation. The outer parts of the vortex system are much stronger than the inner ones. The circulation and size of vortices decrease significantly at the most distant station from the wing. Strong vertical jets were found in smoke-wire visualization and confirmed with velocity and vorticity fields obtained by PIV. These jets are formed between undulating vortices and inside of the vortex ring. The jet airflow moves away from the flapper and downward or upward depending on the flapping direction.

Optically Active Precision Aliphatic Polyesters via Cross‐Metathesis Polymerization

AbstractPrecision synthesis of optically active poly(lactic‐alt‐caprolactic acid) is realized using cross‐metathesis polymerization (CMP) and hydrogenation. Enantiopure monomers ML and MD are generated through two consecutive esterification reactions. CMP of these two monomers in different feed ratios, followed by hydrogenation, afford saturated polymers HPL, HPD, and HPDL comprising L‐lactic and/or D‐lactic acid and ε‐caprolactone‐derived motifs with alternating sequences. CMP kinetic analysis by nuclear magnetic resonance (NMR) is performed by employing a racemic monomer Mrac. Enantiomeric polyesters HPL and HPD display opposite rotation values and mirror‐imaged cotton effects in circular dichroism (CD) spectra, whereas HPDL derived from equimolar ML and MD shows inactive optical rotation and no CD response. Stereocomplex HPD+HPL is obtained by equimolar mixing of HPL and HPD, since this specimen is the only one to exhibit a sharp melting peak on differential scanning calorimetry (DSC) curve at 45.7 °C. Hence, an amorphous, enantiomerically pure polyester becomes crystalline via stereocomplexation with its complementary enantiomer.

Ferroelectric critical size and vortex domain structures of PbTiO3 nanodots: A density functional theory study

The ferroelectric critical size and microscopic domain structure of PbTiO3 nanodots with unit cells of N × N × N (N = 1–3) have been investigated by ab initio (first-principles) density functional theory calculations. Nanodots with PbO and TiO surface terminations are investigated, and the ground state of TiO-terminated nanodots is found to be paraelectric regardless of the size. However, for PbO-terminated nanodots, the ferroelectric state is energetically favorable even in the smallest nanodot, indicating the absence of an intrinsic critical size for ferroelectricity in the nanodot structure. Moreover, the distributions of polarizations in nanodots with different sizes are analyzed. The vortex polarizations rotating around both the central [001] axis and diagonal [11¯1] directions of nanodots can stably exist. The vortex polarization arises from the opposite rotation between the cations and anions around the [001] and the [11¯1] directions of nanodots, respectively. On the other hand, the toroidal moments of vortex polarizations both around the [001] and [11¯1] directions increase with the increment of nanodot size, and these vortex polarizations are energetically favorable in small and large nanodots, respectively.

Modeling of fluid flow in a biological reactor of rotational type

The technology using for the replacement of damaged tissues the own cells of the patient, which are placed in a three-dimensional frame - scaffold, is promising for solving the problem of the bone tissue regeneration. A new biological reactor of the rotational type, in which the scaffold tissue rotates in a medium for cultivating the cells, was designed for the development of this technique. A numerical algorithm based on the ANSYS program was developed, which enables one to estimate in a new bioreactor the level of the mechanical load on the cells, which affects their pro-perties. The algorithm enables the computation of the values of the shear stress and static pressure acting on the scaf-fold surface. The computations have shown that the necessary shear stress is reached in the proposed rotational biore-actor on the outer side of the inner cylinder (0.002−0.1 Pa) in the range of rotation frequencies 0.083 < f < 0.233 Hz. At the same time, computational results have revealed the presence of an inhomogeneity in the mechanical action distribution along the scaffold tissue, which is due to the appearance of two Taylor vortices with opposite rotation directions in the gap between the cylinders. The experiments on the flow field visualization inside the rotational bio-logical reactor have shown a qualitative agreement of the flow character with computational results. The proposed numerical algorithm may simulate with sufficient accuracy the fluid flow in a real system. The obtained dependencies can be used in practice for creating an optimal microenvironment of the cells cultivated in the biological reactor.

Can Stereoclusters Separated by Two Methylene Groups Be Related by DFT Studies? The Case of the Cytotoxic Meroditerpenes Halioxepines.

QM/NMR-DFT (quantum mechanics combined with nuclear magnetic resonance parameters calculated by density functional theory approximations) studies allowed us to link two stereoclusters separated by two methylene groups present in the new meroditerpenes halioxepine B (2) and halioxepine C (3) and the known halioxepine (1), isolated from two Indonesian sponges of the genus Haliclona (Reniera). DP4 and DP4+ probabilities were used to discriminate the two diastereotopic arrangements of the two stereoclusters, whose unconnected relative configurations were determined by ROESY and J-based configurational analysis. To confirm the DFT studies, the full relative configuration of 1 was deduced using a mixture of benzene-d6 and pyridine-d5 as the NMR solvent. ROESY measurements connected the two stereoclusters and demonstrated that DFT calculations accurately predict the configuration when two methylenes separate the two stereoclusters. The different arrangements of the distant stereoclusters C-1/C-2/C-7 and C-10/C-15 for compounds 2 and 3 were deduced by DFT calculations and explained the opposite optical rotations observed for the two compounds. Halioxepines B (2) and C (3) display moderate cytotoxicity against different human cancer cell lines.