Initial Rotation Research Articles

The Source Structure Design of the Rotating Magnetic Beacon Based on Phase-Shift Direction Finding System.

Target azimuth information can help further improve the accuracy of magnetic orientation, but the current periodic magnetic field generated by the magnetic beacon is multivalued, so it is not suitable for azimuth measurement. According to the distribution of a rotating magnetic field and the phase angle measuring principle, we put forward a new magnetic source structure design of a multiple rotating permanent magnet array by adjusting the spacing d, the rotating speed ω and the initial rotation angle φ, and then verified the mathematical model using COMSOL simulation software. A triple structure was obtained by comparison (d3=3d1=3d2=43 m, d3=3d1=3d2=43 m, φ1=0, φ2=4π5 rad. φ3=π rad), which can produce a strong characteristic magnetic signal similar to a heart-shaped field pattern. Finally, a signal transceiver system was set up for the experiment. The experimental result shows that the waveform of the magnetic signal generated by the real beacon meets the requirement of having a unique maximum value and good directivity within a period, which proves the practical application effect of the structure.

3 Phase Synchronous Motor Speed Control System Using PID Control

Synchronous motor is an alternating current (AC) motor that operates with the prime mover as the initial rotation of the rotor until the rotational speed is equal to the rotational speed of the imaginary poles on the stator. In its application a 3-phase synchronous motor needs to be set in advance so that the resulting speed is stable. In this big task of Electric Motor Control, a speed experiment was carried out on a 3-phase synchronous motor using Mathlab simulation with Siemens motor specifications, namely 50 Hz, 400 V with 16kVA power and 1500 RPM rotational speed using PID control to control the speed of a 3-phase synchronous motor so that it is more stable. From the calculations that have been carried out and the PID tuning that has been carried out, the results show that the PID control can control the motor so as to produce a more stable and efficient speed in the industry

HDRNet: High‐Dimensional Regression Network for Point Cloud Registration

AbstractAbstract‐3D point cloud registration is a crucial topic in the reverse engineering, computer vision and robotics fields. The core of this problem is to estimate a transformation matrix for aligning the source point cloud with a target point cloud. Several learning‐based methods have achieved a high performance. However, they are challenged with both partial overlap point clouds and multiscale point clouds, since they use the singular value decomposition (SVD) to find the rotation matrix without fully considering the scale information. Furthermore, previous networks cannot effectively handle the point clouds having large initial rotation angles, which is a common practical case. To address these problems, this paper presents a learning‐based point cloud registration network, namely HDRNet, which consists of four stages: local feature extraction, correspondence matrix estimation, feature embedding and fusion and parametric regression. HDRNet is robust to noise and large rotation angles, and can effectively handle the partial overlap and multi‐scale point clouds registration. The proposed model is trained on the ModelNet40 dataset, and compared with ICP, SICP, FGR and recent learning‐based methods (PCRNet, IDAM, RGMNet and GMCNet) under several settings, including its performance on moving to invisible objects, with higher success rates. To verify the effectiveness and generality of our model, we also further tested our model on the Stanford 3D scanning repository.

Period change rates of Large Magellanic Cloud Cepheids using mesa

ABSTRACT Pulsating stars, such as Cepheids and RR Lyrae, offer us a window to measure and study changes due to stellar evolution. In this work, we study the former by calculating a set of evolutionary tracks of stars with an initial mass of 4 to 7 M⊙, varying the initial rotation rate and metallicity, using the stellar evolution code modules for experiments in stellar astrophysics (mesa). Using Radial Stellar Pulsations (rsp), a recently added functionality of mesa, we obtained theoretical instability strip (IS) edges and linear periods for the radial fundamental mode. Period–age, period–age–temperature, period–luminosity, and period–luminosity–temperature relationships were derived for three rotation rates and metallicities, showing a dependence on crossing number, position in the IS, rotation, and metallicity. We calculated period change rates (PCRs) based on the linear periods from rsp. We compared our models with literature results using the geneva code, and found large differences, as expected due to the different implementations of rotation between codes. In addition, we compared our theoretical PCRs with those measured in our recent work for Large Magellanic Cloud Cepheids. We found good overall agreement, even though our models do not reach the short-period regime exhibited by the empirical data. Implementations of physical processes not yet included in our models, such as pulsation-driven mass-loss, an improved treatment of convection that may lead to a better description of the IS edges, as well as consideration of a wider initial mass range, could all help improve the agreement with the observed PCRs.

Air core vortexing in liquid draining tanks: Influence of surface roughness

This paper study the influence of roughness of the tank base in the formation of air core vortex when liquid inside the cylindrical tank is rotated and subsequently drained. The vortex air core formation in drain tanks can lead to the blockage of drain port and can result in reduced discharge of draining liquid as an immediate consequence. The formation of such a vortex in propellant tanks of spacecraft and rockets will lead to underutilization of propellants and can adversely affect the performance of rocket engines. Ingestion of air core vortex in metal casting process can affect the mechanical properties of casted metal. Hence, suppression of air core vortex is inevitable in the fields of aerospace, metal casting and other hydraulic engineering systems. Current study makes use of roughness of the tank base to suppress vortexing which is the first of its kind and therefore, novel. Experimental investigations have been carried out at several values of roughness height and initial fluid rotation to study the characteristics of air core vortex. It is found that at the highest value of initial rotation provided to the liquid, air core vortexing can be subdued up to 25% by making use of base roughness. Current study also recommends drain tank manufacturers not to smoothen the tank base surface spending time at extra cost. In addition, applying roughness on the tank base will further weaken the formation of air core vortex, in the light of this study.

Fire resistance design of the bolted-welded hybrid composite connection in steel frame

As a key component of the steel frame, the connection is important for the behaviour of the steel frame and for the prevention of progressive collapse under fire. To investigate the fire resistance of the bolted-welded hybrid composite connection in steel frame (BWC-SF), based on a completed test, a refined finite element model of the BWC-SF with a reinforced concrete slab was established. A parametric analysis was carried out to investigate the effects of the beam end load ratio, axial compression ratio of the column, thickness of the beam web and flange, thickness of the column web and flange, thickness of the concrete slab and reinforcing bar diameter. The fire resistance of the connection improved with a decrease in the beam end load ratio and reinforcing bar diameter and with an increase in the thicknesses of the beam flange, beam web and concrete slab. The flexural capacity and stiffness of BWC-SF components, which had great effects on the fire resistance, were analysed. The flexural capacity and initial rotation stiffness calculation method of the BWC-SF at elevated temperatures were established based on the component method and verified according to the test and finite element results.

Kinetics of Electrochemical Removal of Nickel using Bio-electrochemical Reactor with Packed Bed Rotating Cylinder Cathode

The kinetics of nickel removal from aqueous solutions using a bio-electrochemical reactor with a packed bed rotating cylinder cathode was investigated. The effects of applied voltage, initial nickel concentration, the rotation speed of the cathode, and pH on the reaction rate constant (k) were studied. The results showed that the cathodic deposition occurred under mass transfer control for all values of the applied voltage used in this research. Accordingly, the relationship between concentration and time can be represented by a first-order equation. The rate constant was found to be dependent on the applied voltage, initial nickel concentration, pH, and rotation speed. It was increased as the applied voltage increased and decreased as the initial concentration increased. Its relation to the applied voltage can be fitted as follows: where ko =0.01695 min-1 and -β=0.431. pH and rotation speed have two dissimilar effects on the rate constant. Increasing the pH from 3-6 leads to an increase in the rate constant, while a decrease in the rate constant beyond pH=6 has occurred. Increasing the rotation from 100 to 300 rpm results in an increase in the rate constant. However, the rate constant decreases significantly beyond a rotation speed of 300 rpm.

Mobile Robot Application with Hierarchical Start Position DQN.

Advances in deep learning significantly affect reinforcement learning, which results in the emergence of Deep RL (DRL). DRL does not need a data set and has the potential beyond the performance of human experts, resulting in significant developments in the field of artificial intelligence. However, because a DRL agent has to interact with the environment a lot while it is trained, it is difficult to be trained directly in the real environment due to the long training time, high cost, and possible material damage. Therefore, most or all of the training of DRL agents for real-world applications is conducted in virtual environments. This study focused on the difficulty in a mobile robot to reach its target by making a path plan in a real-world environment. The Minimalistic Gridworld virtual environment has been used for training the DRL agent, and to our knowledge, we have implemented the first real-world implementation for this environment. A DRL algorithm with higher performance than the classical Deep Q-network algorithm was created with the expanded environment. A mobile robot was designed for use in a real-world application. To match the virtual environment with the real environment, algorithms that can detect the position of the mobile robot and the target, as well as the rotation of the mobile robot, were created. As a result, a DRL-based mobile robot was developed that uses only the top view of the environment and can reach its target regardless of its initial position and rotation.

Assessment of Design Approaches for Stainless‐Steel Joints Through an Equivalent FE Modelling Technique

AbstractConsidering the significant strain‐hardening and ductility characteristics of stainless steel and the influential role of beam to column joints in the overall response of structures, a clear understanding of their moment rotation behaviour appears fundamental. In the present study, a review of the European design code for three typical semi‐continuous beam‐to‐column joints (extended end plate, flush end plate and top‐and‐seat angle connections) is first carried out. Then, using a hybrid modelling strategy with uncoupled elastic‐plastic springs for the bolts and shell elements for the members, more refined 3D finite element (FE) models are developed and validated against available test results. An equivalent stress definition is then proposed for calculating the joint moment resistance. Finally, the initial rotational stiffness, moment resistance, rotation capacity, and failure patterns are used to evaluate critically the accuracy of the predictions of the European design code. As a result, the need for more comprehensive design guidance in accordance with the observed findings is pointed out.

How Prepared Are They? Pediatric Boot Camps and Intern Performance.

To determine whether participation in a pediatric boot camp during medical school was associated with higher intern performance. Secondary objectives were to determine whether participation in general boot camps, pediatric subinternships or pediatric electives was associated with higher performance. Intern surveys and faculty performance assessments during early internship were collected from a convenience sample of pediatric residency programs. Interns completed a survey regarding participation in medical school boot camps, pediatric subinternships and pediatric electives. Faculty assessed intern performance on selected Milestone-based subcompetencies on a 5-point scale following each intern's initial inpatient rotation and results were compared between groups. Seventeen pediatric residency programs participated. Two hundred eighty-seven interns completed the survey (69%), and faculty completed assessments on 71% of these interns. Of interns with complete faculty assessments (n=198), 25% participated in 5 or more days of pediatric boot camp, 30% in general boot camp, and 45% in no boot camp. There were no educationally significant associations between participation in 5 or more days of pediatric boot camp, general boot camp, subinternships, or electives and intern performance. Interns completing at least 10 days of pediatric boot camp (n=25) had slightly higher ratings for incorporating feedback and engaging in help-seeking behavior during June and July only. Participation in pediatric boot camps, general boot camps, pediatric subinternships or electives was not associated with substantially higher intern performance as measured by selected Milestone subcompetencies. Pediatric educators should carefully consider boot camp curricula and anticipated outcomes associated with boot camp participation.

Dynamics of asteroid systems post-rotational fission

Asteroid binaries found among the near-Earth objects are believed to have formed from rotational fission. In this paper, we study the dynamical evolution of asteroid systems the moment after fission. The model considers two bodies the moment after a contact binary separates due to rotational fission. Both bodies are modeled as ellipsoids, and the secondary is given an initial rotation angle about its body-fixed y-axis. Moreover, we consider six different cases, three where the density of the secondary varies and three where the shape of the secondary varies. The simulations consider 45 different initial tilt angles of the secondary, each with 37 different mass ratios. We start the dynamical simulations at the moment the contact binary reaches a spin fission limit, and our model ensures that the closest distance between the surfaces of the two bodies is always kept at 1 cm. The forces, torques, and gravitational potential between the two bodies are modeled using a newly developed surface integration scheme, giving exact results for two ellipsoids. We find that more than 80% of the simulations end with the two bodies impacting, and collisions between the bodies are more common when the density of the secondary is lower, or when it becomes more elongated. In comparison with observed data on asteroid pairs, we find that variations in density and shape of the secondary can account for some of the spread seen in the rotation period for observed pairs. Furthermore, the secondary may also reach a spin limit for surface disruption, creating a ternary or multiple system. We find that secondary fission typically occurs within the first five hours after the contact binary separates, and is more common when the secondary is less dense or more elongated.

Geodesic congruences in 5D warped Ellis–Bronnikov spacetimes

We study the timelike geodesic congruences in the generalised Ellis–Bronnikov spacetime (4D-GEB) and in recently proposed 5D model where a 4D-GEB is embedded in a warped geometry (5D-WGEB) and conduct a comparative study. Analytical expressions of ESR variables (for 4D geometries) are found which reveal the role of the wormhole parameter. In more general 4D and 5D scenarios geodesic equation, geodesic deviation equation and Raychaudhuri equations are solved numerically. The evolution of cross-sectional area of the congruences of timelike geodesics (orthogonal to the geodesic flow lines) projected on 2D-surfaces yield an interesting perspective and shows the effects of the wormhole parameter and growing/decaying warp factors. The presence of warping factor triggers rotation or accretion even in the absence of initial congruence rotation. The presence of rotation in the congruence is also found to be playing a crucial role which we discuss in detail.

Rotation in stellar interiors: General formulation and an asteroseismic-calibrated transport by the Tayler instability

Context. Asteroseismic measurements of the internal rotation of evolved stars indicate that at least one unknown efficient angular momentum (AM) transport mechanism is needed in stellar radiative zones in addition to hydrodynamic transport processes. Aims. We investigate the impact of AM transport by the magnetic Tayler instability as a possible candidate for such a missing physical mechanism. Methods. We derived general equations for AM transport by the Tayler instability to be able to test different versions of the Tayler-Spruit (TS) dynamo by comparing rotational properties of these models with asteroseismic constraints available for sub-giant and red giant stars. Results. These general equations highlight, in a simple way, the key role played by the adopted damping timescale of the azimuthal magnetic field on the efficiency of the resulting AM transport. Using this framework, we first show that the original TS dynamo provides an insufficient coupling in low-mass red giants that have a radiative core during the main sequence (MS), as was found previously for more massive stars that develop a convective core during the MS. We find that the core rotation rates of red giant branch (RGB) stars predicted by models computed with various prescriptions for the TS dynamo are nearly insensitive to the adopted initial rotation velocity. We then derived a new calibrated version of the original TS dynamo and find that the damping timescale adopted for the azimuthal field in the original TS dynamo has to be increased by a factor of about 200 to correctly reproduce the core rotation rates of stars on the RGB. This calibrated version predicts no correlation of the core rotation rates with the stellar mass for RGB stars in good agreement with asteroseismic observations. Moreover, it correctly reproduces the core rotation rates of clump stars similarly to a revised prescription proposed recently. Interestingly, this new calibrated version of the TS dynamo is found to be in slightly better agreement with the core rotation rates of sub-giant stars, while simultaneously better accounting for the evolution of the core rotation rates along the RGB compared to the revised dynamo version. These results were obtained with both the Geneva and the MESA stellar evolution codes.

Simulation of the movement of a robot mower with direction control

The question of the stability of the movement of the robot-mower in a given direction is considered. The direction of movement is controlled using an angle sensor and a programmable controller by changing the engine power of one of the two driving wheels. The maximum control ratio in the drive wheel drive when the mower is moving on a flat surface depends on the direction of the initial rotation of the chassis. Keywords: robot mower, regulation, direction of movement. B-Mikhael@yandex.ru, anashin@rgau-msha.ru, Kabdin-nek@mail.ru, v.storchevoy@rgau-msha.ru, sudnikya@mail.ru

Non-integer order analysis of electro-magneto-thermoelastic with diffusion and voids considering Lord–Shulman and dual-phase-lag models with rotation and gravity

This study developed the effect of the diffusion with voids within the generalized thermoplastic half-space having initial stress, rotation, a field of electromagnetism, and gravity for the following two models: Lord–Shulman and dual-phase-lag. The authors expressed the study’s problem in the dimensionless form and resolved it analytically by the normal mode analysis and Lame’s potential method. The analytical solutions for the temperature, stresses, displacements, concentration of diffusion, and volume fraction field were gained in the physical field using the analysis of normal mode. The outcome of all parameters was given and portrayed graphically. Comparisons were made with the findings gained in appearance and nonappearance of the examined variables and presented in graphs. The study reported that the impacts of the initial stress, diffusion, gravity, voids, rotation, and electromagnetic field are obvious on the phenomenon. The impact of fractional calculus and a comparison between the presence and absence of fractal calculus were discussed to clear the physical meaning of the fractional parameter and their related applications in biology, geophysics, etc.

Prograde spin-up during gravitational collapse

Asteroids, planets, stars in some open clusters, and molecular clouds appear to possess a preferential spin-orbit alignment, pointing to shared processes that tie their rotation at birth to larger parent structures. We present a new mechanism that describes how collections of particles, or “clouds”, gain a prograde rotational component when they collapse or contract while subject to an external, central force. The effect is geometric in origin, as relative shear on curved orbits moves their shared center-of-mass slightly inward and toward the external potential during a collapse, transferring orbital angular momentum into aligned (prograde) rotation. We perform illustrative analytical and N-body calculations to show that this process of prograde spin-up proceeds quadratically in time (δLrot ∝ t2) until the collapse nears completion. The total rotational gain increases with the size of the cloud prior to its collapse, δLrot /LH ∝ (Rcl/RH)5, and typically with distance to the source of the potential (LH ∝ r0). For clouds that form at the interface of shear and self-gravity (Rcl ~ RH), prograde spin-up means that even setups with large initial retrograde rotation collapse to form prograde-spinning objects. Being a geometric effect, prograde spin-up persists around any central potential that triggers shear, even those where the shear is strongly retrograde. We highlight an application to the Solar System, where prograde spin-up can explain the frequency of binary objects in the Kuiper belt with prograde rotation.

A Study on the Thermo-Mechanical History, Residual Stress, and Dynamic Recrystallization Mechanisms in Additively Manufactured Austenitic Stainless Steels

In this work, both numerical simulations and experimental characterization were used to obtain a broad understanding of the thermo-mechanical history, residual stress, and microstructure of the directed energy deposition (DED) process of austenitic stainless steels. To investigate the effect of process factors on residual stress, the global sensitivity analysis approach based on D-MORPH-HDMR was utilized. The results of the research reveal that the amplified effect of the influence of the three input variables (layer thickness, L; laser power, P; and scanning speed, v) on the transverse residual stress and thickness-direction residual stress is L > P > v; in contrast, the influence of longitudinal residual stress is P > L > v. We also found that general tendencies in local plastic strain accumulation are analogous to the relative distribution of geometrically necessary dislocations (GNDs). Additionally, we investigated post-solidification structures connected to residual stress, such as submicron dislocation cells and dynamic recrystallization (DRX) in austenitic stainless steels during DED. The investigation revealed that the DDRX and CDRX phenomena were caused by the bulging of initial grain boundaries and progressive sub-grain rotation (PSR). The fact that the sample bottom had more thermo-mechanical cycles than the top led to a higher dislocation density and hence more DDRX. This study presents a unique perspective on the link between residual stress and microstructure in additive manufacturing.

On the synthesis of heavy nuclei in protomagnetar outflows and implications for ultra-high energy cosmic rays

ABSTRACT It has been suggested that strongly magnetized and rapidly rotating protoneutron stars (PNSs) may produce long duration gamma-ray bursts (GRBs) originating from stellar core collapse. We explore the steady-state properties and heavy element nucleosynthesis in neutrino-driven winds from such PNSs whose magnetic axis is generally misaligned with the axis of rotation. We consider a wide variety of central engine properties such as surface dipole field strength, initial rotation period, and magnetic obliquity to show that heavy element nuclei can be synthesized in the radially expanding wind. This process is facilitated provided the outflow is Poynting-flux dominated such that its low entropy and fast expansion time-scale enables heavy nuclei to form in a more efficient manner as compared to the equivalent thermal GRB outflows. We also examine the acceleration and survival of these heavy nuclei and show that they can reach sufficiently high energies ≳ 1020 eV within the same physical regions that are also responsible for powering gamma-ray emission, primarily through magnetic dissipation processes. Although these magnetized outflows generally fail to achieve the production of elements heavier than lanthanides for our explored electron fraction range 0.4–0.6, we show that they are more than capable of synthesizing nuclei near and beyond iron peak elements.

Hidden spatiotemporal sequence in transition to shear band in amorphous solids

Localization of plastic flow into a narrow shear band is a fundamental and ubiquitous nonequilibrium phenomenon in amorphous solids. Because of the intrinsic entangling of three types of elementary local atomic motion---shear, dilatation, and rotation---the precise physical process of shear band emergence is still an enigma. Here, to unveil this mystery, we formulate a theoretical protocol covering both affine and nonaffine components of deformation, to decode these three highly entangled local atomic-scale events. In contrast to the broad concept of the shear transformation zone, the plastic behavior can be demonstrated comprehensively as the operative manipulation of more exact shear-dominated zones, dilatation-dominated zones, and rotation-dominated zones. Their spatiotemporal evolution exhibits a transition from synchronous motion to separate distribution at the onset of the shear band. The hidden mechanism is then revealed with the help of extreme value theory and percolation analysis. Numerical evidence from extreme value theory indicates that dilatation is the dominant mode at the embryonic stage of the initial plastic units, as evidenced through the larger degree of dilatation localization compared with shear and rotation. The percolation analysis points towards the critical power-law scaling nature at the transition from stochastic activation to percolation of plastic regions. Then the comprehensive picture underlying shear banding emergence is uncovered. Firstly, dilatation triggers initial shear and rotation in soft regions, leading to the embryos of the initial flow units, which are followed by the secondary activation of rotation in neighboring hard material, thus causing an alternating distribution of rotation and shear-dilatation regions. Such rotation activation contributes to further perturbation in these regions and ultimately leads to percolation transition and shear band formation. Our findings also reinforce that the discussion of plastic behavior in disordered materials must take into account both affine and nonaffine component deformation.

Observational signatures of black hole accretion: rotating versus spherical flows with tilted magnetic fields

ABSTRACT We study the observational signatures of magnetically arrested black hole accretion with non-rotating inflow on to a rotating black hole; we consider a range of angles between the black hole spin and the initial magnetic field orientation. We compare the results of our general relativistic magneto-hydrodynamic simulations to more commonly used rotating initial conditions and to the Event Horizon Telescope (EHT) observations of M87. We find that the mm intensity images, polarization images, and synchrotron emission spectra are very similar among the different simulations when post-processed with the same electron temperature model; observational differences due to different electron temperature models are significantly larger than those due to the different realizations of magnetically arrested accretion. The orientation of the mm synchrotron polarization is particularly insensitive to the initial magnetic field orientation, the electron temperature model, and the rotation of the inflowing plasma. The largest difference among the simulations with different initial rotation and magnetic tilt is in the strength and stability of the jet; spherical inflow leads to kink-unstable jets. We discuss the implications of our results for current and future EHT observations and for theoretical models of event-horizon-scale black hole accretion.