High Rotational Frequencies Research Articles

STUDY OF MASS MOTION ON VIBRATING DEVICE: DESIGN AND PROCESS SIMULATION

The simulation of mass motion using a vibrating device that was laboratory designed was the main idea of the work. The construction of an experimental vibrating device and the associated measuring station along with the measurement of dynamic properties of the vibrating device depending on preselected input parameters of the device of bulk material on this experimental model is presented. The simulation of the general behavior of particles on an experimental vibrating device at rotational frequencies of 20 Hz, 25 Hz and 35 Hz, and the rotation of contact vibrators at 30°, 45° and 75° by mass flow modeling using software ROCKY DEM is done. It was observed that the particles were moving at the fastest speed at 45° and at 35 Hz and that the top layers fall to the bottom especially at higher rotational frequencies, which may ultimately cause aeration of the particulate matter, thus reducing the angle of internal friction of the bulk material.

Anomalous temperature dependence of self-interstitial diffusivity in metallic lithium and sodium

Despite the abundance and importance of alkali metals for various applications, the behavior of point and dimensional defects in them has remained terra incognita. At the same time, the growing interest to high-capacity Li-metal batteries and the study of Li electrodeposition mechanisms dictates the need to investigate the defect dynamics. Here, we report the results of MD simulations of atomic motions in bulk Li and Na, including vacancy and interstitial (particularly <111>-crowdion) defect dynamics. Our main finding is an anomalous temperature dependence of the apparent diffusion coefficient for self-interstitial atoms (SIA), namely, the diffusivity decrease with the temperature rise. To uncover the underlying mechanism, we analyzed the interplay between 1D motions in terms of mean squared displacement (MSD) and 3D motions due to SIA rotations or switching. We found that the coefficient for 1D crowdion migration along the 〈111〉 axes is virtually temperature independent in case of both Li and Na. This implies linear temperature dependence of the drag coefficient γ, in contrast to other BCC metals. High rotation frequency reaching several THz at 300 K seems to drive the 1D diffusion into a semi-ballistic mode, therefore also affecting the temperature dependence of the apparent 3D diffusion coefficient. We believe that our results contribute to the atomistic understanding of low-barrier processes in a crystal lattice.

Effective potentials in a rotating spin-orbit-coupled spin-1 spinor condensate

We theoretically study the stationary-state vortex lattice configurations of rotating spin-orbit (SO)- and coherently-coupled spin-1 Bose–Einstein condensates (BECs) trapped in quasi-two-dimensional harmonic potentials. The combined effects of rotation, SO and coherent couplings are analyzed systematically from the single-particle perspective. Through the single-particle Hamiltonian, which is exactly solvable for one-dimensional coupling, we illustrate that a boson in these rotating SO- and coherently-coupled condensates are subjected to effective toroidal, symmetric double-well, or asymmetric double-well potentials under specific coupling and rotation strengths. In the presence of mean-field interactions, using the coupled Gross–Pitaevskii formalism at moderate to high rotation frequencies, the analytically obtained effective potential minima and the numerically obtained coarse-grained density maxima position are in excellent agreement. On rapid rotation, we further find that the spin-expectation per particle of an antiferromagnetic spin-1 BEC approaches unity indicating a similarity in the response with ferromagnetic SO-coupled condensates.

Metaheuristic Algorithm-Based Vibration Response Model for a Gas Microturbine.

Data acquisition and processing are areas of research in fault diagnosis in rotating machinery, where the rotor is a fundamental component that benefits from dynamic analysis. Several intelligent algorithms have been used to optimize investigations of this nature. However, the Jaya algorithm has only been applied in a few instances. In this study, measurements of the amplitude of vibration in the radial direction in a gas microturbine were analyzed using different rotational frequency and temperature levels. A response surface model was generated using a polynomial tuned by the Jaya metaheuristic algorithm applied to the averages of the measurements, and another on the whole sample, to determine the optimal operating conditions and the effects that temperature produces on vibrations. Several tests with different orders of the polynomial were carried out. The fifth-order polynomial performed better in terms of MSE. The response surfaces were presented fitting the measured points. The roots of the MSE, as a percentage, for the 8-point and 80-point fittings were 3.12% and 10.69%, respectively. The best operating conditions were found at low and high rotational frequencies and at a temperature of 300 C. High temperature conditions produced more variability in the measurements and caused the minimum value of the vibration amplitude to change in terms of rotational frequency. Where it is feasible to undertake experiments with minimal variations, the model that uses only the averages can be used. Future work will examine the use of different error functions which cannot be conveniently implemented in a common second-order model. The proposed method does not require in-depth mathematical analysis or high computational capabilities.

Study of shape evolution of nuclei with 40 ≤ Z ≤ 48 and 50 < N < 60

A systematic investigation of the structural evolution of the even-even isotones of 40<Z<50 nuclei in 50<N<60 range of neutron numbers has been done from the calculations of total Routhian surfaces (TRS) in the macroscopic-microscopic formalism. The calculations predict that the nuclei with N=56 are transitional ones with an onset of deformation at N≥56. It has been found that the shape of the midshell Ru (Z=44) isotopes is mostly γ-soft near the ground state. The TRS calculations at higher rotational frequencies (ħω) for 100,102Ru show a shape evolution in these nuclei from a prolate-like γ-soft to a stable triaxial shape. Such stable triaxial shapes in the even-even cores are important to explain the observed chiral bands in the odd-odd Rh nuclei. A common general feature that has been found for the heavier nuclei from this work is the shape invariance of the nuclei with same numbers of total (proton + neutron) valence particles away from N,Z=50.

Dynamic Characteristics of a Traction Drive System in High-Speed Train Based on Electromechanical Coupling Modeling under Variable Conditions

The traction drive system of a high-speed train has a vital role in the safe and efficient operation of the train. This paper established an electromechanical coupling model of a high-speed train. The model considers the interaction of the gear pair, the equivalent connecting device of the transmission system, the equivalent circuit of the traction motor, and the direct torque control strategy. Moreover, the numerical simulation of the high-speed train model includes constant speed, traction, and braking conditions. The results indicate that the meshing frequency and the high harmonics rotation frequency constitute the stator current. Furthermore, both frequencies are evident during constant speed. However, they are blurry among other conditions except for twice the rotation frequency. Meanwhile, the rotor and stator currents’ root-mean-square (RMS) values during traction are less than the RMS value during braking. The initiation of traction and braking causes a significant increase in current. During the traction and braking process, the RMS value of the current gradually decreases. Therefore, it is necessary to pay attention to the impact of the transition process on system reliability.

Numerical modeling of straight and helical elastic rods under fluid flow using immersed boundary method

This paper presents a three-dimensional computational model built using immersed boundary finite volume method to explore the dynamics of straight and helical elastic rods rotating under an applied fluid flow in a channel. Numerical simulations are done for low and high rotational frequencies of a base motor attached at one fixed end of the rods. Simulations reveal that under low rotational frequency, a straight rod (bend at free end) always performs stable twirling motion and eventually attains straight state (mechanical equilibrium) under an applied fluid flow. But on the other hand, for the same conditions a helical rod always keeps its helical shape during interaction with fluid and never attains stable straight state. For the case of high rotational frequency, the straight rod executes whirling motion in which it attains helical shape during all the time. Whirling motion is also observed for helical rod under high rotational frequency. For similar conditions, the instantaneous shapes obtained by straight and helical rods are different which indicates that the initial configuration of the rod as well as rotational frequency have significant impact in deciding the dynamics of the elastic rod under fluid flow. In the biological realm, these elastic rods represent flagellum of monotrichous bacteria which helps for propulsion in fluid. Hence, the present simulation results will help to develop efficient bacteria inspired artificial microrobot for biomedical applications.

High-accuracy longitudinal position measurement using self-accelerating light.

Radially self-accelerating light exhibits an intensity pattern that describes a spiraling trajectory around the optical axis as the beam propagates. In this article, we show in simulation and experiment how such beams can be used to perform a high-accuracy distance measurement with respect to a reference using simple off-axis intensity detection. We demonstrate that generating beams whose intensity pattern simultaneously spirals with fast and slow rotation components enables a distance measurement with high accuracy over a broad range, using the high and low rotation frequency, respectively. In our experiment, we achieve an accuracy of around 2 µm over a longitudinal range of more than 2 mm using a single beam and only two quadrant detectors. Because our method relies on single-beam interference and only requires a static generation and simple intensity measurements, it is intrinsically stable and could find applications in high-speed measurements of longitudinal position.

Analytical and experimental investigation of the centrifugal softening and stiffening effects in rotational energy harvesting

Depending on its mounting orientation, the rotational piezoelectric harvester can be subjected to the centrifugal softening or stiffening effects, which may pose a positive or negative influence on the energy harvesting performance. This paper firstly presents the comprehensive comparison of the centrifugal softening and stiffening harvesters with a unified dimensionless analytical model. The analytical expressions of the optimum short-circuit and open-circuit rotational frequencies, the optimum resistances and the optimum centrifugal coefficients are derived to reveal the influence mechanism of the centrifugal effects. The proposed model is validated experimentally and used for case studies to compare the centrifugal softening and stiffening harvesters. Results illustrate that the centrifugal softening harvester has a superior energy harvesting performance at low rotational frequencies while the centrifugal stiffening harvester is better at high rotational frequencies. Furthermore, the peak power of the centrifugal softening harvester is higher while the frequency bandwidth of the centrifugal stiffening harvester is wider. In addition, it is found that the centrifugal stiffening harvester is more sensitive to the centrifugal coefficient. Based on the centrifugal stiffening effect, the self-tuning harvester can be achieved with a wide frequency bandwidth. Meanwhile, this requires that the centrifugal coefficient is precisely determined, and the fundamental natural frequency of the harvester without the centrifugal force should be low enough when operating at low rotational frequencies. Compared with the centrifugal stiffening effect, the centrifugal softening effect may be more suitable to be used in MEMS/NEMS applications since it can reduce the fundamental resonant frequency of the harvester during the rotation.

Stationary states, dynamical stability, and vorticity of Bose-Einstein condensates in tilted rotating harmonic traps

We theoretically investigate a Bose-Einstein condensate confined by a rotating harmonic trap whose rotation axis is not aligned with any of its principal axes. The principal axes of the Thomas-Fermi density profiles of the resulting stationary solutions are found to be tilted with respect to those of the rotating trap, representing an extra degree of freedom that is associated with the existence of additional branches of stationary solutions for any given rotation axis alignment. By linearizing the time-dependent theory about the stationary states, we obtain a semi-analytical prediction of their dynamical instability at high rotation frequencies against collective modes arising from environmental perturbations. Comparing the stationary states to direct simulations of the Gross-Pitaevskii equation, we predict the nucleation of quantum vortices in the dynamically unstable rotational regime. These vortex lines are aligned along the rotation axis despite the tilting of the rotating trap although the background density profile is tilted with respect to the trapping and rotation axes.

1997 JET DT experiments revisited—comparative analysis of DD and DT stationary baseline discharges

This paper compares the stationary ELMy H-mode baseline 50%–50% deuterium-tritium (DT) mixture discharges in the first high -power JET DT experimental campaign in 1997 (JET-DTE1) with the counterpart 100% deuterium (DD) baseline discharges which have the same engineering parameters, i.e. Ip, Bt, q95, NBI power, plasma shape, no gas dosing, divertor structure, and the carbon wall. There is no difference in profile peaking of Te, Ti, and ne between the DT and the counterpart DD baseline discharges, indicating that there was no isotopic effect on the core transport in the stationary baseline DT discharges in the 1997 JET-DTE1. The core values of Te, Ti, and ne are higher in some DT discharges compared to their counterpart DD discharges, but this is attributed to the higher pedestal values, rather than any improvement in the core transport. The interpretive TRANSP simulations also show that the local heat diffusivity is not consistently different between the DT and the counterpart DD baseline discharges.The baseline discharges in the 1997 JET-DTE1 are also compared to the latest high-power ELMy H-mode baseline DD discharges with an ITER-like wall (ILW) in 2016. Despite the similar effective collisionality and ion heat deposition in the core, it was observed that Ti/Te is consistently close to unity in the 1997 JET-DTE1 discharges, while the 2016 JET baseline discharges have high Ti, exceeding Te, which enabled the highest fusion performance in the ITER-Like Wall. The high rotation frequency was the key factor in increasing Ti/Te in the 2016 JET baseline discharges, and it is also the main difference compared to the stationary baseline discharges in the 1997 JET-DTE1. Based on this, it is prospected that higher rotation frequency is the key factor to achieving high fusion power in the stationary baseline discharges in the 2020 JET-DTE2, and the plasma operation with the low gas dosing and increased torque available in the present NBI system would enable such a high rotation frequency.

The 31 yr Rotation History of the Millisecond Pulsar J1939+2134 (B1937+21)

Abstract The timing properties of the millisecond pulsar PSR J1939+2134—very high rotation frequency, very low time derivative of rotation frequency, no timing glitches, and relatively low timing noise—are responsible for its exceptional timing stability over decades. It has been timed by various groups since its discovery, at diverse radio frequencies, using different hardware and analysis methods. Most of the timing data is now available in the public domain in two segments, which have not been combined so far. This work analyzes the combined data by deriving uniform methods of data selection, derivation of Dispersion Measure (DM), accounting for correlation due to “red” noise, etc. The timing noise of this pulsar is very close to a sinusoid, with a period of approximately 31 yr. The main results of this work are: (1) the clock of PSR J1939+2134 is stable at the level of almost one part in 1015 over about 31 yr; (2) the power-law index of the spectrum of electron density fluctuations in the direction of PSR J1939+2134 is 3.86 ± 0.04; (3) a Moon-sized planetary companion, in an orbit of semimajor axis about 11 astronomical units and eccentricity ≈0.2, can explain the timing noise of PSR J1939+2134; (4) precession under electromagnetic torque with very small values of oblateness and wobble angle can also be the explanation but with reduced confidence; and (5) there is an excess timing noise of about 8 μs amplitude during the epochs of steepest DM gradient, of unknown cause.

Dynamic Stiffness Analysis and Measurement of Radial Active Magnetic Bearing in Magnetically Suspended Molecular Pump

Current stiffness and displacement stiffness are two important parameters of radial active magnetic bearing (RAMB) that are generally considered as constants in a control system. However, such presumption may lead to the probable degradation of the control performance of the RAMB system when the perspective that the current and displacement stiffness should be variable due to variations in the speed. On this regard, a structure analysis and stiffness measurement method based on non-variable stiffness would not be feasible for RAMB under high-speed conditions. This paper presented an analysis of the dynamic stiffness characteristics of RAMB by means of a dynamic equivalent magnetic circuit method and laid out a comparison between the results of the theoretical analysis and the simulation results of finite element method. In particular, a novel dynamic stiffness measurement method of RAMB under high-rotation frequency was introduced. Results of experiments on the dynamic stiffness of RAMB demonstrated an excellent agreement with the theoretical research and the finite element analysis results, thereby verifying the rationality of the discussed dynamic stiffness characteristics. Practically, the proposed measurement method of RAMB dynamic stiffness provides an accurate analysis for the dynamic stiffness and contributes inspiring research significance for the dynamic properties of RAMB.

Centrifugal gyration mill for fine product self-grinding

A simplified design of a centrifugal mill for fine grinding of the product based on a parallelogram mechanism is proposed. A high dynamic balance was achieved, providing a high rotation frequency of the grinding chambers, and hence a high degree of the product grinding. Keywords centrifugal mill, parallelogram mechanism, selfgrinding, fine grinding

Effect of toroidal rotation on plasma response to resonant magnetic perturbations in HL-2A

&lt;sec&gt;Resonant magnetic perturbation (RMP), generated by externally applied magnetic perturbation coils, is an important method of controlling plasma edge localized mode. Many experiments have shown that RMP can effectively mitigate/suppress edge localized mode, but its intrinsic physical mechanism is not completely clear. The response of plasma to RMP is the key to understanding the RMP physics. In the presence of RMP, the circumferential symmetry of the tokamak magnetic field will be broken, forming a new three-dimensional(3D) equilibrium, and this process is called the plasma response to RMP. Currently, the parameter range and control effect of RMPs to control edge localized mode on different devices are quite different, implying that the plasma response to RMPs has different response results in different parameter ranges on different devices. Therefore, it is necessary to study the RMP response characteristics of specific devices.&lt;/sec&gt;&lt;sec&gt;In this work, the effect of the plasma rotation frequency on the linear response process of plasma to the resonant magnetic perturbations is investigated in the framework of MARS-F in the HL-2A configuration, and the physical reasons are analyzed in detail. It is found that the shielding and amplification effects in plasma response do not change linearly with plasma rotation frequency, since the plasma resistivity plays an important role. The shielding effect for the magnetic perturbation on the rational surface is enhanced with the increase of the rotation frequency in the high rotation frequency range. However, this rule no longer holds true in the low rotation frequency range due to the deviation of the strongest shielding position from the rational surface caused by the plasma resistivity. As for the amplification effect, the resistivity weakens the amplification effect of plasma response due to the dissipation of induced current. The variation trend of the amplification effect with the rotation frequency and resistivity is consistent with that of the core-kink response, which indicates that the amplification effect of the magnetic perturbation is mainly caused by the core-kink response.&lt;/sec&gt;

Thermal Damage of Intake Valves in ICE with Variable Timing

The article provides the study on causes of damage to ICE intake valves, in the course of which the intake valve heads have been overheated and deformed as a result of material creep. On the example of the failure detected in the analysed engine, it has been established that the traditionally known reasons such as the combustion process failure cannot cause the damage described. For the purpose of determining the real causes of damage to the intake valves the authors simulated the thermal state of the intake valve in the heatingcooling conditions with the impact of gas in the cylinder and the impact of air in the intake pipe as well as the contact heat exchange with the seat with regard to thermal conductivity along the stem. The calculations have shown that with the increase of rotation frequency the failure of the control system that causes the engine to run at high rotation frequencies with a small intake valve lift leads to the temperature increase higher than it is recommended for the materials used, which causes the described overheating. Based on the conducted research the authors have developed recommendations for improving the reliability of the intake valves performance in the ICEs with variable valve timing.

The evolution of kicked stellar-mass black holes in star cluster environments - II. Rotating star clusters

Abstract In this paper, we continue our study on the evolution of black holes (BHs) that receive velocity kicks at the origin of their host star cluster potential. We now focus on BHs in rotating clusters that receive a range of kick velocities in different directions with respect to the rotation axis. We perform N-body simulations to calculate the trajectories of the kicked BHs and develop an analytic framework to study their motion as a function of the host cluster and the kick itself. Our simulations indicate that for a BH that is kicked outside of the cluster’s core, as its orbit decays in a rotating cluster the BH will quickly gain angular momentum as it interacts with stars with high rotational frequencies. Once the BH decays to the point where its orbital frequency equals that of local stars, its orbit will be circular and dynamical friction becomes ineffective since local stars will have low relative velocities. After circularization, the BH’s orbit decays on a longer time-scale than if the host cluster was not rotating. Hence BHs in rotating clusters will have longer orbital decay times. The time-scale for orbit circularization depends strongly on the cluster’s rotation rate and the initial kick velocity, with kicked BHs in slowly rotating clusters being able to decay into the core before circularization occurs. The implication of the circularization phase is that the probability of a BH undergoing a tidal capture event increases, possibly aiding in the formation of binaries and high-mass BHs.

Backbending, seniority, and Pauli blocking of pairing correlations at high rotational frequencies in rapidly rotating nuclei

Garrett et al. systematically investigated band-crossing frequencies resulting from the rotational alignment of the first pair of i13/2 neutrons (AB) in rare-earth nuclei. In that study, evidence was found for an odd-even neutron number dependence attributed to changes in the strength of neutron pairing correlations. The present paper carries out a similar investigation at higher rotational frequencies for the second pair of aligning i13/2 neutrons (BC). Again, a systematic difference in band-crossing frequencies is observed between odd-N and even-N Er, Yb, Hf, and W nuclei, but in the BC case, it is opposite to the AB neutron-number dependence. These results are discussed in terms of a reduction of neutron pairing correlations at high rotational frequencies and of the effects of Pauli blocking on the pairing field by higher-seniority configurations. Also playing a significant role are the changes in deformation with proton and neutron numbers, the changes in location of single-particle orbitals as a function of quadrupole deformation, and the position of the Fermi surface with regard to the various Ω components of the neutron i13/2 shell.Received 22 March 2019DOI:https://doi.org/10.1103/PhysRevC.100.014302©2019 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasCollective levelsCollective modelsNuclear forcesNuclear structure & decaysProperties150 ≤ A ≤ 189Nuclear Physics

Analysis of the Characteristics of an Electromechanical Starter in a Gas Turbine Plant

The article explores the possibility of using synchronous motors excited from permanent magnets (PMs) for electric starting of gas turbine powerplants (GTPPs) in gas transport systems. The two analyzed versions of the starter are one with radially magnetized inductor-surface-mounted permanent magnets (SPMs) and one with V-shaped inductor-core-interior-mounted permanent magnets (IPMs). The performance specifications entail that the starter has a multimode operation (hot start, dry run, gas–air flow duct flushing) in a short period of time and repeated short-time modes with target torque characteristics. The analyzed parameters of the compared rotor designs are magnetic flux distribution, harmonic composition of the field and counter-EMF, torque values and ripple, PM energy efficiency, and resistance to irreversible demagnetization. It is established that the SPM starter has a better torque density and overload capacity and weaker torque ripple and can be recommended for the electric startup of GTPPs with an increased inertia torque. The starter with an IPM rotor is preferable in terms of energy efficiency and ability to counteract the demagnetizing action of armature response. The technological difficulties of producing rotors with external magnets make it more complicated to use them in motors with high rotation frequencies.

A music-box-like extended rotational plucking energy harvester with multiple piezoelectric cantilevers

Vibrational interference has been found to incur inefficient system responses and suboptimal energy harvesting performance as the rotational frequency increases in the conventional rotational plucking energy harvester. As a result, this letter proposes a music-box-like structure of a rotational plucking energy harvester to overcome the problem by extending the rotary cylinder out of plane. A model is proposed and experimentally validated by characterizing its dynamic and energetic characteristics. Numerical analyses show that the proposed rotational plucking structure can reduce the vibrational interference and be capable of harvesting more energy at high rotational frequencies as well as extending the operating frequency range and broadening the half-power bandwidth.