Faster Rotation Speed Research Articles

Aircraft deicing based on large vibration of wings

Since aircraft icing will decrease the ability of aircraft to generate lift, it is significant to consider the aircraft deicing problem. The paper presents an aircraft deicing method based on the cracking of the ice layer caused by the large deformations of wings. To describe the deformation of wings, the absolute coordinate-based formulation is used. The aircraft with high aspect ratio wings is simplified as a hub-beam system. Such a rigid-flexible system with the fast rotation speed of hub and the large deformation of the beam is modeled using absolute coordinate-based formulation accurately. The maneuver of the rigid body will lead to the large deformation of wings to do the de-icing. Numerical examples are presented to reveal that the maximum tensile strength on the wing surface with sinusoidal control torques with some amplitudes and frequencies is larger than the ice’s tensile strength. Hence, the proposed de-icing method based on the aircraft maneuvering is potential.

Study on dynamic response characteristics of the scanning angle in a liquid crystal cladding waveguide beam scanner

This paper studies the dynamic response characteristics of the scanning angle in a liquid crystal cladding waveguide beam scanner. Based on liquid crystal dynamic theory, finite element analysis and vectorial refraction law, a dynamic response calculation model of scanning angle is constructed. The simulation results show that the dynamic responses of the scanning angle during the electric field-on and field-off processes are asymmetric, and exhibit “S”-shape and “L”-shape changing trends, respectively. In addition, by comparing with the bulk phase modulation response process of traditional liquid crystal devices, the intrinsic physical reason for the rapid light regulation of the liquid crystal cladding waveguide beam scanner is clarified to be that the liquid crystal close to the core layer has a faster rotation speed during the electric field-off process. Moreover, the liquid crystal cladding waveguide beam scanner is experimentally tested, and the experiment results are in good agreement with theoretical simulations.

Two-photon absorption of oxindole-based push–pull molecular motors

Future applications of light-driven molecular motors in bio-based systems and soft materials require their operation with benign, low-energy light irradiation. Here we report four rotary molecular motors based on oxindole units which can be driven by near-infrared light. By installing an electron-withdrawing CN group on the oxindole lower half, in direct conjugation through the alkene axle to the electron-donating OMe substituent on the upper half, our design establishes a rigid push–pull system which red-shifts the absorption maximum further into the visible region. We also show that the induced nonlinearity to the system increases their two-photon absorption cross section, and the operation of oxindole based molecular motors with 800 nm light for the very first time. The motors prepared in this work show improved performance compared to previous oxindole based motors, e.g. visible light addressability up to 530 nm and 1.5-fold increase in quantum yields in both directions, whilst retaining their desirable qualities of easy synthesis and fast rotation speed.

Enhancing friction stir welding efficiency through rotational speed adjustment: a microstructural and mechanical analysis of Al-Cu alloy

Friction stir welding (FSW) has gained prominence in the aerospace and automotive industries due to its ability to produce high-strength and defect-free welds in aluminum alloys. The present investigation focuses on the impact of different tool rotational speeds (such as 700 rpm, 900 rpm, 1100 rpm and 1300 rpm), on the microstructure and mechanical characteristics of friction stir welded Al-Cu alloys. With the use of optical microscopy, scanning electron microscopy (SEM), x-ray diffraction (XRD), and evaluations of hardness, tensile characteristics, and fracture behavior, a thorough analysis was carried out. The weld nugget zone contained significant changes in grain size and shape as a function of rotational speed, as shown by microstructural analysis. The grain structure gradually became more refined when the rotating speed was raised from 900 to 1500 rpm. According to SEM observations, at faster speeds, the weld zone showed fewer defects per unit area and better bonding properties, which might be attributed to better material flow and plastic deformation. The effect was further clarified by XRD analysis, which showed differences in phase composition with varying rotating speeds. Evaluations of the mechanical properties showed a significant relationship between rotating speed and the mechanical performance of the welds. Hardness measurements showed that as rotating speed increased, hardness levels gradually increased. Welds made at faster rotational speeds had better elongation and tensile qualities, according to tensile tests. Additionally, fracture behavior study revealed that higher rotational speed welds displayed a more ductile fracture mode, indicating increased toughness.

Transient Electromyographic Responses by Isokinetic Torque Release during Mechanically Assisted Elbow Flexion.

Power assistance on joint torque may not be beneficial to all the related muscles. We investigated the effects of power assistance on torque release during isokinetic elbow flexion. An isokinetic dynamometer system was used to simulate dynamic elbow flexion with power assistance, which altered the exercise conditions of baseline isometric torque (greater and lower) and rotation speed (faster and slower) of the lever arm. Ten male right-handed participants performed exercise tasks using the system. We measured (1) the electromyogram (EMG) amplitudes of the biceps brachii (BB), brachioradialis (BR), and triceps brachii (TB) muscles, (2) torque output and its variability, and (3) the perceived assistance level. Transient responses of the objective measurements were analyzed by observing three time epochs before and after power assistance. Greater variability and lower perceived assistance levels were observed when greater torque was released at a faster rotation speed. The torque output and EMG amplitudes of BB and BR muscles decreased over time. However, EMG amplitudes in the TB muscle were relatively constant until 200 ms after power assistance resulting in greater muscle co-contraction. This could be attributed to the increased postural stability of the human musculature system when the external perturbation on joint movement occurred by power assistance, independent of exercise conditions.

Interannual eddy variability in the eastern Ryukyu Island chain

Interannual eddy variability in the eastern Ryukyu Island chain (RIC) was analyzed based on eddy trajectories and assimilation data. Analysis of the eddy trajectory data suggested a predominance of eddies originating near the study area. The occurrence frequency of eddies has interannual variability, but it demonstrates a different tendency with eddy kinetic energy (EKE): few eddies appear when EKE is high; however, they are strong with fast rotation speeds and increase in size. The EKE variability was correlated with the baroclinic conversion rates, suggesting a vital role of baroclinic instability in the study area. Baroclinic instability was found to be affected by the North Equatorial Current (NEC), during which more NEC water entered the eastern RIC, intensifying the vertical velocity shear between the upper and lower oceans. Consequently, baroclinic instability in the study area was enhanced.

Influence of coded mask rotation speed and central detector to imaging performance for time-encoded imager

Time-encoded imaging could be useful for searching potential radioactive sources for preventing illicit transportation and trafficking of nuclear materials. A 2-D, dual-particle, time-encoded imager was developed for gamma-ray and neutron source imaging. The influence of central detector and coded mask rotation speed to imaging performance, such as angular resolution, signal-to-noise ratio and detection time, was investigated by Am–Be neutron source imaging experiments. The EJ276 plastic scintillator (Size: Φ5.08 cm × 5.08 cm) and CLYC scintillator (Size: Φ2.54 cm × 2.54 cm) couple to photomultiplier tubes was set as the central detector, respectively. Under the experiment conditions (Am–Be neutron source; 300 mCi; 1.8 m), for the neutron and gamma-ray images with EJ276 detector, the best horizontal and vertical angular resolution was (3.7°, 4.8°) and (5.9°, 6.6°), minimum detection time was 100 s and 600 s, respectively; for the neutron and gamma-ray images with CLYC detector, the best horizontal, vertical angular resolution was (3.1°, 3.1°) and (3.5°, 3.3°), minimum detection time was 2200 s and 1600 s, respectively. For different central detector, the results showed that the smaller volume of detector, the better angular resolution; the lower detection efficiency, the longer detection time. For different rotation speed, too fast rotation speed can lead to failure to locate the source.

Numerical Study of Temperature Evolution During Friction Element Welding

Abstract Welding of dissimilar materials is critical in industries where mixed materials with high strength-to-weight ratios are urgently needed. Friction element welding (FEW) is a promising solution, with the ability to join high strength materials for a wide range of thicknesses with low input energy and a short processing time. However, the temperature evolution and the influence of different processing parameters remain unclear. To bridge this knowledge gap, this work develops a coupled thermal–mechanical finite element model to study the FEW process. The simulation results agree well with the experimental measurements of material deformation and transient temperature evolution. It is found that the friction element’s rotational speed has the greatest impact on friction heat generation, followed by the processing times for different steps. The aluminum layer is heated during the penetration and cleaning steps, thus a lower rotational speed during the penetration step can help prevent the aluminum layer from undesired overheating. The steel layer and the friction element are mainly heated during the cleaning and welding steps. The strong heating, potentially melting, will be beneficial to the friction element’s plastic deformation and bond formation. To enhance the heating of the steel layer and the friction element, faster rotational speeds or longer processing periods could be employed during the cleaning and welding steps. The results by this study establish the relationship between processing conditions and the temperature evolution of different parts, which will guide the design and optimization of the FEW technique for various applications.

Imbalance compensation of active magnetic bearing systems using model predictive control based on linear parameter-varying models

Active magnetic bearing (AMB) is a suspension system to levitate a rotating shaft freely without any physical contact which allows extremely fast rotation speeds. One big control challenge of the AMB systems, which appears during high rotation speeds, is the non-uniform distribution of the rotor weight about its rotating axis. This is usually referred to as the rotor imbalance problem which produces sinusoidal disturbance forces. These disturbances lead to undesirable vibrations and large deviations of the rotor shaft from its desired trajectories. We adopt in this work model predictive control (MPC) to reduce the effect of these sinusoidal disturbances and to achieve a stable levitation of the rotor shaft while tracking a reference trajectory. Owing to the MPC capability of handling constraints in an optimal manner, physical input constraints can be committed. Moreover, state constraints can be imposed to ensure safety of operation. For tractable implementation, we embed the nonlinear dynamics of the system in a linear parameter-varying (LPV) representation. To guarantee stability of the closed-loop system, a terminal cost and a terminal constraint set are included in the MPC optimization problem. For tractable computations of these terminal ingredients, a reduced LPV model is considered. The performance of the proposed LPV-MPC scheme is validated via simulation on the nonlinear model of an experimental setup of an AMB system and it is compared with two other classical controllers commonly used for these AMB systems in practice.

A Multilevel Model for Calculating the Motion of Rocks

The presence of a large number of loose rocks, often accompanied by giant rocks, which are highly destructive to the surface are an important factor in geological hazard risk assessment. In rocks moving along a slope, the scale of movement and the scale of deformation differ substantially in magnitude owing to their movement characteristics of large moving distance, fast rotation speed, and small deformation. A multilevel model for rock motion calculation is established to separate the rigid displacement and deformation displacement of the rock. The total rock movement displacement comprises translational displacement, rotational displacement, and deformation displacement. Three corresponding coordinate systems are set up. These include the translational coordinate system, which is used to describe the translational displacement of the rock, the rotational coordinate system, which is used to describe the rotational displacement of the rock, and the co-rotational coordinate system, which is used to describe the deformation displacement of the rock. The origin and the direction of the coordinate axis of the co-rotational coordinate system change with the movement of the rock. Lagrange’s principle establishes the equations of motion, which is solved by an explicit approach in the framework of the Continuum-discontiuum element method. Several numerical cases verify that this method can accurately calculate the rotational movement of the rock.

Comparison of the characteristics of magnetars born in death of massive stars and merger of compact objects with swift gamma-ray burst data

ABSTRACT Assuming that the shallow-decaying phase in the early X-ray light curves of gamma-ray bursts (GRBs) is attributed to the dipole radiations (DRs) of a newborn magnetar, we present a comparative analysis for the magnetars born in death of massive stars and merger of compact binaries with long and short GRB (lGRB and sGRB) data observed with the Swift mission. We show that the typical braking index (n) of the magnetars is ∼3 in the sGRB sample, and it is ∼4 for the magnetars in the lGRB sample. Selecting a sub-sample of the magnetars whose spin-down is dominated by DRs (n ≲ 3) and adopting a universal radiation efficiency of 0.3, we find that the typical magnetic field strength (Bp) is 1016 G versus 1015 G and the typical initial period (P0) is ∼20 ms versus 2 ms for the magnetars in the sGRBs versus lGRBs. They follow the same relation between P0 and the isotropic GRB energy as $P_0\propto E_{\rm jet}^{-0.4}$. We also extend our comparison analysis to superluminous supernovae (SLSNe) and stable pulsars. Our results show that a magnetar born in merger of compact stars tends to have a stronger Bp and a longer P0 by about one order of magnitude than that born in collapse of massive stars. Its spin-down is dominated by the magnetic DRs as old pulsars, being due to its strong magnetic field strength, whereas the early spin-down of magnetars born in massive star collapse is governed by both the DRs and gravitational wave (GW) emission. A magnetar with a faster rotation speed should power a more energetic jet, being independent of its formation approach.

Distribution and kinematics of 26Al in the Galactic disc.

26Al is a short-lived radioactive isotope thought to be injected into the interstellar medium (ISM) by massive stellar winds and supernovae (SNe). However, all-sky maps of 26Al emission show a distribution with a much larger scale height and faster rotation speed than either massive stars or the cold ISM. We investigate the origin of this discrepancy using an N-body+hydrodynamics simulation of a Milky-Way-like galaxy, self-consistently including self-gravity, star formation, stellar feedback, and 26Al production. We find no evidence that the Milky Way's spiral structure explains the 26Al anomaly. Stars and the 26Al bubbles they produce form along spiral arms, but, because our simulation produces material arms that arise spontaneously rather than propagating arms forced by an external potential, star formation occurs at arm centres rather than leading edges. As a result, we find a scale height and rotation speed for 26Al similar to that of the cold ISM. However, we also show that a synthetic 26Al emission map produced for a possible Solar position at the edge of a large 26Al bubble recovers many of the major qualitative features of the observed 26Al sky. This suggests that the observed anomalous 26Al distribution is the product of foreground emission from the 26Al produced by a nearby, recent SN.

Performance Effects of Different Table Tennis Ball Materials

ABSTRACT The performance of two different table tennis balls (i.e. a seamless poly ball and a seamed celluloid ball) is compared both experimentally and numerically. No significant difference is found in the coefficients of restitution of the two balls in free-fall impact tests onto a flat rubber surface. However, the celluloid ball has a faster rotational speed on serving, while the poly ball has a greater rebound angle. However, on serving, the celluloid ball has a faster spinning speed than the poly ball, while the poly ball has a greater rebound angle. In addition, for a given spin rotation speed and serving speed, the celluloid ball has a faster sink velocity than the seamless poly ball.

Annular Surface Micromachining of Titanium Tubes Using a Magnetorheological Polishing Technique.

In this study, a novel magnetorheological (MR) polishing device under a compound magnetic field is designed to achieve microlevel polishing of the titanium tubes. The polishing process is realized by combining the rotation motion of the tube and the reciprocating linear motion of the polishing head. Two types of excitation equipment for generating an appropriate compound magnetic field are outlined. A series of experiments are conducted to systematically investigate the effect of compound magnetic field strength, rotation speed, and type and concentration of abrasive particles on the polishing performance delivered by the designed device. The experiments were carried out through controlling variables. Before and after the experiment, the surface roughness in the polished area of the workpiece is measured, and the influence of the independent variable on the polishing effect is judged by a changing rule of surface roughness so as to obtain a better parameter about compound magnetic field strength, concentration of abrasive particles, etc. It is shown from experimental results that diamond abrasive particles are appropriate for fine finishing the internal surface of the titanium-alloy tube. It is also identified that the polishing performance is excellent at high magnetic field strength, fast rotation speed, and high abrasive-particle concentration.

A Break in Spiral Galaxy Scaling Relations at the Upper Limit of Galaxy Mass

Abstract Super spirals are the most massive star-forming disk galaxies in the universe. We measured rotation curves for 23 massive spirals with the Southern African Large Telescope (SALT) and found a wide range of fast rotation speeds (240–570 km s−1), indicating enclosed dynamical masses of (0.6−4) × 1012 M ⊙. Super spirals with mass in stars log M stars / M ⊙ > 11.5 break from the baryonic Tully–Fisher relation (BTFR) established for lower-mass galaxies. The BTFR power-law index breaks from 3.75 ± 0.11 to 0.25 ± 0.41 above a rotation speed of ∼340 km s−1. Super spirals also have very high specific angular momenta that break from the Fall relation. These results indicate that super spirals are undermassive for their dark matter halos, limited to a mass in stars of log M stars / M ⊙ < 11.8 . Most giant elliptical galaxies also obey this fundamental limit, which corresponds to a critical dark halo mass of log M halo / M ⊙ ≃ 12.7 . Once a halo reaches this mass, its gas can no longer cool and collapse in a dynamical time. Super spirals survive today in halos as massive as log M halo / M ⊙ ≃ 13.6 , continuing to form stars from the cold baryons they captured before their halos reached critical mass. The observed high-mass break in the BTFR is inconsistent with the Modified Newtonian Dynamics theory.

Resolving Single-Nanoconstruct Dynamics during Targeting and Nontargeting Live-Cell Membrane Interactions.

This paper describes how differences in the dynamics of targeting and nontargeting constructs can provide information on nanoparticle (NP)-cell interactions. We probed translational and rotational dynamics of functionalized Au nanostar (AuNS) nanoconstructs interacting with cells in serum-containing medium. We found that AuNS with targeting ligands had a larger dynamical footprint and faster rotational speed on cell membranes expressing human epidermal growth factor receptor 2 (HER-2) receptors compared to that of AuNS with nontargeting ligands. Targeting and nontargeting nanoconstructs displayed distinct membrane dynamics despite their similar protein adsorption profiles, which suggests that targeted interactions are preserved even in the presence of a protein corona. The high sensitivity of single-NP dynamics can be used to compare different nanoconstruct properties (such as NP size, shape, and surface chemistry) to improve their design as delivery vehicles.

Analysis of particle rotation in fluidized bed by use of discrete particle model

The particle rotation was found important in the fluidized bed when the heterogeneous structures appeared. Some researches show that Magnus lift force might play an pivotal role in fluid-solid system, especially when the particles have fast rotation speed. As the Magnus lift force is acted at the single particle level, a pseudo two-dimensional discrete particle model (DPM) was used to investigate the influence of Magnus lift force in fluidized bed. The rotational Reynolds number (Rer) bases on the angular velocity and the diameter of the spheres is used to characterize the rotational movement of particles. We studied the influence of Magnus lift force for particles with rotational Reynolds number in the range of 1–100. Our results show that the influence of Magnus lift force is enhanced with a higher Rer. Magnus lift force affects the movement of particles in both radial and axial directions while Rer is high. However, in low Rer case it can be neglected in computational simulation model. This indicates the introduction of Magnus lift force may improve the discrete particle model only in high Rer case and Magnus effect should be considered in real gas-solid two phase system when the particle rotational speed is high.

Effect of gantry rotation speed and scan mode on peristalsis motion artifact frequency and severity at abdominal CT.

The purpose of the study was to understand the effect of CT gantry speed and axial vs. helical scan mode on the frequency and severity of bowel peristalsis artifacts. We retrospectively identified 150 oncologic abdominopelvic CT scans obtained on a 256 slice CT scanner: 50 scans obtained with Axial mode and 0.5-s gantry rotation time (Slow-Axial); 50 with Axial mode and 0.28-s gantry rotation time (Fast-Axial); and 50 scans with Helical mode and 0.28-s gantry rotation time (Fast-Helical). The patients included 74 women and 76 men with a mean age of 61years (range 22-85years). Two readers viewed all CT scans to record the presence and severity of bowel peristalsis artifact, location of artifact (stomach, duodenum/jejunum, ileum, and colon) and artifact location relative to bowel interface (gas-bowel, fluid-bowel, and gas-fluid). The severity of artifacts was recorded subjectively on a 3-point scale, and objectively based on maximum length of the artifact. Peristalsis artifact was more commonly seen with Slow-Axial scan acquisition (37 of 50 patient scans, or 74%) than Fast-Axial (15 in 50 patient scans, or 30%, p<0.001) and Fast-Helical (22 of 50 patient scans, or 44%, p<0.005). The bowel segment distribution and severity of peristalsis artifacts were not significantly different between scan techniques. Peristalsis artifacts are common at abdominopelvic CT scans. Fast gantry rotation speed significantly reduces the frequency of bowel peristalsis artifacts and should be a consideration when imaging of bowel and structures near bowel is critical.

Mixing efficiency enhancing in micromixer by controlled magnetic stirring of Fe3O4 nanomaterial

Rapid and complete mixing are fundamental criteria in the design of microfluidic chips and to date, magnetic stir bars are proving convenient and efficient tools for both macroscale and lab-on-chip applications. In this work, we implement magnetic stirring of Fe3O4 nanomateral to mediate active mixing in T-shape micromixers, where passive diffusion of two solutes (blue phenol dye and citric acid) has otherwise proven inefficient. The Fe3O4 magnetic nanoparticles are added to the citric acid which then transform into nano- or micro-rods that rotate synchronously with an external rotating magnetic field. As such, the local flow field that each rod generates can perturb the hydrodynamic flow in the mixing channel. The mixing performance with magnetic nanoparticles added at different concentrations and rotation speeds reveal that higher concentration of magnetic particles in the solution and fast rotation speeds improve the efficiency significantly. More efficient mixing with microrods is also achievable using wide channels and low flow rates. Efficient mixing has been realized for a 6.6 mT driving field if the magnetic materials are rotated at 10.47 rad sź1 and 0.05 wt% concentration. The same parameters applied to a 300 µm micro channel at 2 µL minź1 flow rate more than double the efficiency of a passive micromixer.

An experimental evaluation of a new designed apparatus (NDA) for the rapid measurement of impaired motor function in rats

BackgroundAssessment of the ability of rat to balance by rotarod apparatus (ROTA) is frequently used as a measure of impaired motor system function. Most of these methods have some disadvantages, such as failing to sense motor coordination rather than endurance and as the sensitivity of the method is low, more animals are needed to obtain statistically significant results. New methodWe have designed and tested a new designed apparatus (NDA) to measure motor system function in rats. Our system consists of a glass box containing 4 beams which placed with 1cm distance between them, two electrical motors for rotating the beams, and a camera to record the movements of the rats. The RPM of the beams is adjustable digitally between 0 and 50 rounds per minute. ResultsWe evaluated experimentally the capability of the NDA for the rapid measurement of impaired motor function in rats. Also we demonstrated that the sensitivity of the NDA increases by faster rotation speeds and may be more sensitive than ROTA for evaluating of impaired motor system function. Comparison with existing methodsCompared to a previous version of this task, our NDA provides a more efficient method to test rodents for studies of motor system function after impaired motor nervous system. ConclusionsIn summary, our NDA will allow high efficient monitoring of rat motor system function and may be more sensitive than ROTA for evaluating of impaired motor system function in rats.