Toroidal Form Research Articles

ANALYSIS OF WORK CONDITIONS AND CAUSES WEAR HOLES SEPARATING SIEVES IN SERVICE

Advantages and disadvantages of sieves for the crusher were considered. The research focuses on changes of the holes of the sieves toroidal shape and establishes common time to failure. The result of experimental research is to establish the durability of the separating sieves with holes design close to the wear in comparison with standard sieves. The result shows the efficiency of using sieves with toroidal form of holes similar to the natural wearing, which persists for the entire lifetime and provides high-quality completion of the separation process. The principal difference in the experimental separation of the sieves is that they are in the process of operation and wear effectively perform the function of sifting the grain mass desired fraction. The new form of holes, close to form normal wearing has led to the possibility of such profiles forming that change their shape.

Integrated Inductor and Capacitor With Co-Located Electric and Magnetic Fields

Passive components such as inductors and capacitors are fundamental components of nearly all power electronic conversion systems. This paper presents an innovative approach to highly integrated inductor ( L ) and capacitor ( C ) design by storing magnetic and electric field energy in a common volume, constituting a dual energy core (DEC). This is dissimilar from other integrated designs that primarily exploit a distributed parasitic capacitance between planar inductor windings, ultimately parsing electric, and magnetic fields into separate locations unnecessarily. The DEC enables a four terminal integrated LC device that may be applied in series, parallel, or in separate parts of the circuit, since its terminal characteristics appear as decoupled lumped elements. The fields in the core geometry are analytically modeled and the effects and tradeoffs of selecting different core parameters/dimensions are explored. Proof of concept prototypes of toroidal form factor demonstrate techniques for fabricating DEC integrated devices, and experimental measurements correlate with the analytical models used in the design process. A boost converter is constructed and tested with a prototype integrated device to demonstrate decoupled operation of the fields in the core on a large signal basis.

Principle and Design of a Novel Lorenz Force Type Bearingless Motor with Single-Axis Actively Regulated Capability

This paper proposes a novel Lorenz-force-type bearingless motor with single-axis actively positioned functionality. The novel motor consists of two slotless surface-mounted permanent magnet(SPM) motors, which have six skewed coils for each motor to constitute 3-phase windings and are in tandem along axial direction so as to achieve actively regulated axial motion. Additionally, two repulsive permanent magnet bearings (RPMBs) are used to passively stabilize radial- and tilting movements of the rotor. The slotless stator iron is employed for arrangement of the skewed coils in toroidal form. Compared with state-of-the-art single-axis actively controlled bearingless motors utilizing field weakening or strengthening effect of d-axis current to regulate axial movement, perhaps suffering irreversible demagnetization of permanent magnets especially at the time of start-up, the merit of this proposed motor is beneficial to prevent the demagnetization risk of permanent magnets. To verify the novel concept, firstly, theoretical analysis is carried out for modeling back electromagnetic force (back-EMF), axial force, drive torque. Followed by the analytical model, a detailed design process by integration of analytical method and finite element analysis (FEA) for the structural parameters are revealed. At last, 3-D FEA is performed to validate the correctness of analytical model, design process as well as to evaluate the performance of proposed motor.

A non-singular boundary element method for modelling bubble dynamics in viscoelastic fluids

When a cavity forms near a solid boundary a liquid jet can form directed towards the boundary, causing the generation of high pressures at the wall (potentially causing damage) and the formation of a toroidal bubble. In this paper several recent developments in the boundary element modelling of the dynamics of cavitation bubbles in viscoelastic fluids are presented. The standard formulation of the boundary element method (BEM) is in terms of a boundary integral equation with a singular kernel. A reformulation of the BEM in terms of a non-singular kernel is shown to provide enhanced stability. In situations when a liquid jet forms and impacts the far side of the bubble there is a transition to a toroidal form. This topological singularity in bubble geometry is modelled by placing a vortex ring inside the bubble to account for the circulation in the fluid and the discontinuity in potential following jet impact. The bubble dynamics are dependent on the initial stand-off distance from the boundary as well as the viscous and elastic properties of the fluid. It is shown that, while the viscosity of the fluid inhibits jet formation, the dynamics are particularly dependent on the relative strength of viscous, elastic and inertial forces. In particular, if the Deborah number is large enough elastic effects effectively negate fluid viscosity and behaviour similar to the inviscid case is recovered in terms of liquid jet formation.

ATP and Magnesium Promote Cotton Short-Form Ribulose-1,5-bisphosphate Carboxylase/Oxygenase (Rubisco) Activase Hexamer Formation at Low Micromolar Concentrations

We report a fluorescence correlation spectroscopy (FCS) study of the assembly pathway of the AAA+ protein ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activase (Rca), a ring-forming ATPase responsible for activation of inhibited Rubisco complexes for biological carbon fixation. A thermodynamic characterization of simultaneously populated oligomeric states appears critical in understanding Rca structure and function. Using cotton β-Rca, we demonstrate that apparent diffusion coefficients vary as a function of concentration, nucleotide, and cation. Using manual fitting procedures, we provide estimates for the equilibrium constants for the stepwise assembly and find that in the presence of ATPγS, the Kd for hexamerization is 10-fold lower than with ADP (∼0.1 vs ∼1 μM). Hexamer fractions peak at 30 μM and dominate at 8-70 μM Rca, where they comprise 60-80% of subunits with ATPγS, compared with just 30-40% with ADP. Dimer fractions peak at 1-4 μM Rca, where they comprise 15-18% with ATPγS and 26-28% with ADP. At 30 μM Rca, large aggregates begin to form that comprise ∼10% of total protein with ATPγS and ∼25% with ADP. FCS data collected on the catalytically impaired WalkerB-D173N variant in the presence of ATP provided strong support for these results. Titration with free magnesium ions lead to the disaggregation of larger complexes in favor of hexameric forms, suggesting that a second magnesium binding site with a Kd value of 1-3 mM mediates critical subunit contacts. We propose that closed-ring toroidal hexameric forms are stabilized by binding of Mg·ATP plus Mg2+, whereas Mg·ADP promotes continuous assembly to supramolecular aggregates such as spirals.

Effect of Al-ion substitution on structural and magnetic properties of Co–Ni ferrites nanoparticles prepared via citrate precursor method

Nanocrystalline Co0.8Ni0.2AlyFe2−yO4 (y = 0.00, 0.15, 0.30, 0.45, 0.60, 0.75) powders have been synthesized by the citrate precursor auto-combustion method. The effect of the nonmagnetic aluminum ion substitution on the structural and magnetic properties has been studied. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy revealed that the obtained powders have a single phase of cubic spinel structure. The crystallite sizes estimated from XRD data have been confirmed using high-resolution transmission electron microscopy (HRTEM). Photographs showed powders consisting of nanosized grains with an average size ranging from 10 to 45 nm, depending on the Al content. Magnetic hysteresis loops were traced at room temperature using vibrating sample magnetometer (VSM). It was found that, due to the aluminum substitution, the values of magnetic losses and saturation and remanent magnetization were decreased, indicating a reduction in the ferrimagnetic behavior. This reduction of magnetization, compared to the undoped sample, was attributed to the increase of spin noncollinearity with increasing Al content. Samples with toroidal forms were used to measure both the initial permeability (μi) and Curie temperature (TC). The obtained results showed a decrease in the values of both μi and TC as the Al content increases. This behavior was explained in view of the weakness in the interaction of A and B sublattices with increasing Al3+ ion concentration.

Publisher's Note: “Momentum transport in the vicinity of q min in reverse shear tokamaks due to ion temperature gradient turbulence” [Phys. Plasmas 21, 012302 (2014)

Publisher's Note: “Momentum transport in the vicinity of <i>q</i> <i>min</i> in reverse shear tokamaks due to ion temperature gradient turbulence” [Phys. Plasmas 21, 012302 (2014)

Effect of Oxygen Content during Sintering on the Losses of MnZn Ferrites

The magnetic properties of MnZn ferrites are highly influenced by the partial oxygen pressure during sintering. In this work MnZn ferrites with different chemical compositions were pressed in a toroidal form and sintered at 1290 °C for 6 h at different oxygen pressures. X ray diffraction using K-edge radiation of Fe, Zn and Mn were performed in order to identify the atomic preference in the MnZn ferrite spinel structure, by means of Rietveld analysis. Magnetic losses were measured at 25 °C and 100 °C (200mT, 100 kHz). The high temperature loss decreased with the increase of oxygen content during sintering whereas at room temperature this effect was opposite. The losses behavior as function of frequency was analyzed according the loss separation model.

Supplementary comparison COOMET.EM-S12: Measurements of magnetic loss power in electrical steel at frequencies of 50 Hz and 60 Hz

The decision to carry out a COOMET supplementary comparison in the field of magnetic loss power measurements was taken in October 2010. It is registered in the BIPM key comparison database with the identifier COOMET.EM-S12. The comparison was piloted by UNIIM (Russia) and two other laboratories participated, namely PTB (Germany) and CMI (Czech Republic).The results of the comparison allow one to demonstrate the equivalence of the standards of the three National Metrology Institutes, and thus confirm the corresponding claimed Calibration and Measurement Capabilities (CMCs).It is noted that the deviation of the measurement results obtained with sheet samples exceeds that obtained with samples of toroidal form and of Epstein strips, a point that requires further investigation.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Toroidal quadrupole form factor of the deuteron

We calculate the toroidal quadrupole moment and form factor of the deuteron, which violate time-reversal symmetry but conserve parity, at leading order in two-flavor chiral effective field theory with perturbative pion exchange. We take into account time-reversal and parity violation due to the QCD vacuum angle combined with parity violation resulting from the weak interaction in the Standard Model. We also consider time-reversal and parity violation that at the quark-gluon level results from effective dimension-six operators originating from physics beyond the Standard Model.

Sophisticated Modeling Uncovers Atomic DNA Structure in Bacteriophage Φ29 Cavity

Sophisticated Modeling Uncovers Atomic DNA Structure in Bacteriophage Φ29 Cavity

Graphs of Hecke operators

Let $X$ be a curve over $\F_q$ with function field $F$. In this paper, we define a graph for each Hecke operator with fixed ramification. A priori, these graphs can be seen as a convenient language to organize formulas for the action of Hecke operators on automorphic forms. However, they will prove to be a powerful tool for explicit calculations and proofs of finite dimensionality results. We develop a structure theory for certain graphs $G_x$ of unramified Hecke operators, which is of a similar vein to Serre's theory of quotients of Bruhat Tits trees. To be precise, $G_x$ is locally a quotient of a Bruhat Tits tree and has finitely many components. An interpretation of $G_x$ in terms of rank 2 bundles on $X$ and methods from reduction theory show that $G_x$ is the union of finitely many cusps, which are infinite subgraphs of a simple nature, and a nucleus, which is a finite subgraph that depends heavily on the arithmetics of $F$. We describe how one recovers unramified automorphic forms as functions on the graphs $G_x$. In the exemplary cases of the cuspidal and the toroidal condition, we show how a linear condition on functions on $G_x$ leads to a finite dimensionality result. In particular, we re-obtain the finite-dimensionality of the space of unramified cusp forms and the space of unramified toroidal automorphic forms. In an Appendix, we calculate a variety of examples of graphs over rational function fields.

Calculation of thin shells with a small number of unidirectional layers by using 3D deformation models

A method for calculating thin shells with one or more unidirectional layers is developed on the basis of 3D deformation models of fiber-reinforced materials at small and large deformations. Contrary to the shell model, the 3D model of shells, which is based on 3D governing equations, allows one to solve the problems on contact interaction of shells between themselves or with other bodies. The use of an applied theory of fibrous materials as a 3D deformation model is considered. The validity of the method is confirmed by using the applied theory in solving the problem on blowing of a rubber-cord diaphragm of toroidal form used in the tire production technology.

Toroidal automorphic forms for function fields

The space of toroidal automorphic forms was introduced by Zagier in 1979. Let F be a global field. An automorphic form on GL(2) is toroidal if it has vanishing constant Fourier coefficients along all embedded non-split tori. The interest in this space stems from the fact (amongst others) that an Eisenstein series of weight s is toroidal if s is a non-trivial zero of the zeta function, and thus a connection with the Riemann hypothesis is established. In this paper, we concentrate on the function field case. We show the following results. The (n −1)-th derivative of a non-trivial Eisenstein series of weight s and Hecke character x is toroidal if and only if L(x, s+1/2) vanishes in s to order at least n (for the “only if” part we assume that the characteristic of F is odd). There are no non-trivial toroidal residues of Eisenstein series. The dimension of the space of derivatives of unramified Eisenstein series equals h(g −1)+1 if the characteristic is not 2; in characteristic 2, the dimension is bounded from below by this number. Here g is the genus and h is the class number of F. The space of toroidal automorphic forms is an admissible representation and every irreducible subquotient is tempered.

Automorphic forms for elliptic function fields

Let F be the function field of an elliptic curve X over \({\mathbb{F}_q}\). In this paper, we calculate explicit formulas for unramified Hecke operators acting on automorphic forms over F. We determine these formulas in the language of the graph of an Hecke operator, for which we use its interpretation in terms of \({\mathbb{P}^1}\)-bundles on X. This allows a purely geometric approach, which involves, amongst others, a classification of the \({\mathbb{P}^1}\)-bundles on X. We apply the computed formulas to calculate the dimension of the space of unramified cusp forms and the support of a cusp form. We show that a cuspidal Hecke eigenform does not vanish in the trivial \({\mathbb{P}^1}\)-bundle. Further, we determine the space of unramified F′-toroidal automorphic forms where F′ is the quadratic constant field extension of F. It does not contain non-trivial cusp forms. An investigation of zeros of certain Hecke L-series leads to the conclusion that the space of unramified toroidal automorphic forms is spanned by the Eisenstein series E( · , s) where s + 1/2 is a zero of the zeta function of X—with one possible exception in the case that q is even and the class number h equals q + 1.

Vibrational analysis and thermodynamic properties of C120 nanotorus: a DFT study

Density functional theory (DFT) computational methods are applied to a C120 carbon nanotorus studied as an isolated molecular species, using the functional GGA PW91. This toroidal form of carbon contains five fold, six fold, and sevenfold rings. The calculated cohesive energy of the nanotorus, indicates that the ground state of this structure is energetically more stable than that of fullerene C60. Geometry and stability, Raman and IR vibrational analysis and thermodynamic properties have been reported and compared to the values obtained by other authors.

Particle removal from a surface by a bounded vortex flow

A bounded vortex flow consists of an axisymmetric vortex that is confined top and bottom between two plates (the “confinement plate” and “impingement plate”, respectively) and surrounded laterally by a swirling annular slot jet. The bottom of the vortex terminates on the boundary layer along the impingement plate and the top of the vortex is drawn into a suction port positioned at the center of the confinement plate. The circumferential flow within the annular jet is important for supplying circulation to the central wall-normal vortex. This flow field is proposed as a method for mitigation of dust build-up on a surface, where the vortex–jet combination supplements the more traditional vacuum port by enhancing the surface shear stress and related particle transport rate. The paper reports on a computational study of the velocity field and particle transport by a bounded vortex flow. Fluid flow computations are performed using a finite-volume approach for an incompressible fluid and particle transport is simulated using a discrete-element method. Computations are performed for different values of two dimensionless parameters – the ratio of the plate separation distance and the average radial location of the jet inlet (the dimensionless confinement height) and the ratio of flow rate withdrawn at the suction outlet and that injected by the jet (the flow rate ratio). For small values of the flow rate ratio, the impinging jet streamlines pass down to the boundary layer along the bottom surface and then travel up the vortex core. By contrast, for large values of flow rate ratio, the annular jet is quickly entrained into the suction outlet and no wall-normal vortex is formed. Particles are observed to roll along the impingement surface in a direction determined by the fluid shear stress lines. Particles roll outward when they lie beyond a separatrix curve of the surface shear stress lines, where particles within this separatrix curve roll inward, piling up at the center of the flow field. A toroidal vortex ring forms for the small confinement height case with flow rate ratio equal to unity, which yields double separatrix curves in the shear stress lines. The inward rolling particles intermittently lift up due to collision forces and burst away from the impingement surface, eventually to become entrained into the flow out the suction port or resettling back onto the impingement surface.

Electrostatic contribution to DNA condensation—application of ‘energy minimization’ in asimple model in the strong Coulomb coupling regime

The process of bending of straight DNA to a circular form in the presence of any of themono-, di-, tri- or tetravalent counterions has been simulated in a strong Coulomb couplingenvironment, employing a previously developed energy minimization simulation technique.The inherent characteristics of the simulation technique allow the monitoring of therequired electrostatic contribution to the bending. The curvature of the bending has beenfound to play a crucial role in facilitating the electrostatic attractive potential energy. Thetotal electrostatic potential energy has been found to decrease with bending, whichindicates that bending straight DNA to a circular form or to a toroidal form in thepresence of neutralizing counterions is energetically favourable and is practically aspontaneous phenomenon.

Non-spherical bubble dynamics in a compressible liquid. Part 2. Acoustic standing wave

This paper investigates the behaviour of a non-spherical cavitation bubble in an acoustic standing wave. The study has important applications to sonochemistry and in understanding features of therapeutic ultrasound in the megahertz range, extending our understanding of bubble behaviour in the highly nonlinear regime where jet and toroidal bubble formation may be important. The theory developed herein represents a further development of the material presented in Part 1 of this paper (Wang &amp; Blake,J. Fluid Mech. vol. 659, 2010, pp. 191–224) to a standing wave, including repeated topological changes from a singly to a multiply connected bubble. The fluid mechanics is assumed to be compressible potential flow. Matched asymptotic expansions for an inner and outer flow are performed to second order in terms of a small parameter, the bubble-wall Mach number, leading to weakly compressible flow formulation of the problem. The method allows the development of a computational model for non-spherical bubbles by using a modified boundary-integral method. The computations show that the bubble remains approximately of a spherical shape when the acoustic pressure is small or is initiated at the node or antinode of the acoustic pressure field. When initiated between the node and antinode at higher acoustic pressures, the bubble loses its spherical shape at the end of the collapse phase after only a few oscillations. A high-speed liquid bubble jet forms and is directed towards the node, impacting the opposite bubble surface and penetrating through the bubble to form a toroidal bubble. The bubble first rebounds in a toroidal form but re-combines to a singly connected bubble, expanding continuously and gradually returning to a near spherical shape. These processes are repeated in the next oscillation.

Impact of Depth of Penetration on Mutual Inductance and Electrical Resistance of Individual Toroidal Coils Using Analytical and Finite Element Methods Applicable to Tokamak Reactors

A toroidal field coil is composed of several individual toroidal coils (ITCs) which are connected in a series and distributed in a toroidal and symmetrical form. Cross section of ITCs is rectangular or negligible. This paper presents analytical equations of mutual inductance of two ITCs applicable to tokamak reactors using the filament method. These equations are based on those formulated by Neumann. The numerical analysis of the integrations resulting from these equations is solved using the extended three-point Gaussian algorithm. The finite element method (FEM) is employed to verify the mutual inductance equations of ITCs. The results obtained using FEM, when dimensional parameters of ITCs are changed, confirm the analytical and empirical results showing an error of less than 0.2043% in the worst case. This indicates the reliability of the presented equations. This paper also employs FEM to obtain depth of penetration of electromagnetic waves in high-conductivity conductors (HCCs). The results show that the ratio of real depth of penetration, obtained by FEM, to ideal depth of penetration in HCCs is independent of frequency. This ratio shows that the magnitude of traveling plane waves in HCC decreases with <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$e^{-1.7916}$</tex></formula> rather than <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX"> $e^{-1}$</tex></formula> .