Rolling Phase Research Articles

Human Vehicle Dynamics Coupling of Miniature Electric Vehicle Roll Stability: Effects of Driver Weight, Wheel Base and Track Width

As a continuation of the previous research, influences of human vehicle dynamics coupling (HVDC) on miniature electric vehicle (MEV) roll stability are studied by varying driver weight, wheel base and track width. A multi-body dynamics model is developed for the human-vehicle system by ADAMS/Car software considering driver’s dynamics and is validated theoretically. Simulation results show that the MEV roll stability is decreased by the HVDC; the influences become greater with an increase in the proportion of the driver weight to curb weight of the MEV in both time and frequency domain; with the decrease of wheel base, the differences caused by the HVDC exhibit an increasing trend in the maximum value and overshoot; and the differences in the steady stable roll angle and phase lag at 0.6 Hz indicate an increasing tendency with the decrease of track width.

TRAFIC: statistical design and analysis plan for a pragmatic early phase 1/2 Bayesian adaptive dose escalation trial in rheumatoid arthritis

BackgroundAdaptive model-based dose-finding designs have demonstrated advantages over traditional rule-based designs but have increased statistical complexity but uptake has been slow especially outside of cancer trials. TRAFIC is a multi-centre, early phase trial in rheumatoid arthritis incorporating a model-based design.MethodsA Bayesian adaptive dose-finding phase I trial rolling into a single-arm, single-stage phase II trial. Model parameters for phase I were chosen via Monte Carlo simulation evaluating objective performance measures under clinically relevant scenarios and incorporated stopping rules for early termination. Potential designs were further calibrated utilising dose transition pathways.DiscussionTRAFIC is an MRC-funded trial of a re-purposed treatment demonstrating that it is possible to design, fund and implement a model-based phase I trial in a non-cancer population within conventional research funding tracks and regulatory constraints. The phase I design allows borrowing of information from previous trials, all accumulated data to be utilised in decision-making, verification of operating characteristics through simulation, improved understanding for management and oversight teams through dose transition pathways. The rolling phase II design brings efficiencies in trial conduct including site and monitoring activities and cost.TRAFIC is the first funded model-based dose-finding trial in inflammatory disease demonstrating that small phase I/II trials can have an underlying statistical basis for decision-making and interpretation.Trial registrationTrials Registration: ISRCTN, ISRCTN36667085. Registered on September 26, 2014.

Investigation on an Nflation phase diagram with multifield polynomial potential

This study aims to investigate an Nflationary phase diagram with a multifield polynomial potential. The gradual vanishing of the inflationary phase during slow roll phase of the Nflation model has been demonstrated for a large number of fields in the case when there are voluminous [Formula: see text] phase transitions occurring in it. A phase diagram for Nflation model illustrates its phase transitions for a multifield potential [Formula: see text]. We use Marčenko–Pastur law to find likely distribution of different mass-scales of the fields. Further, the study for the conditions of entropy is carried out in the form of a bound that conforms to the number of e-folds [Formula: see text] and the number of fields [Formula: see text]. These drive Nflationary phase and are mostly responsible for the phenomena taking place in it. We investigate in addition, that all the de Sitter entropy in the neighborhood of the critical point is concentrated around it and is largely condensed in the number of fields [Formula: see text] for the selected potential.

Production and Mechanical Properties of Cu-Al-Ni-Be Shape Memory Alloy Thin Ribbons Using a Cold Co-Rolled Process

The use of shape memory alloys for micro-actuators constitutes a field of application in which copper–aluminum-based alloys find their usefulness because they can reach higher activation temperatures and are easier to produce than titanium-based alloys, particularly by the method proposed in this work. SMA tapes are a two-dimensional structure that offers many design options such as stamping, punching, and deep drawing, but they are also suitable for laser cutting, engraving, stamping, and EDM machining. This work has been made to study the manufacture of copper-based shape memory alloys (SMAs) using the cold co-rolling process also called the cold-roll bonding (CRB) process. In this process, a thin metal sandwich can be produced with a rolling machine. This sandwich consists of layers of CuNiBe master alloy and Al. During the rolling phase, the sandwich has no shape memory effect (SME) or superelastic effect (SE), so thin strips can be easily produced. After the rolling phase, the sandwich is subjected to a complex heat treatment to gain the SME. To validate this process to produce Cu-based SMAs, several alloys with different CuAlNiBe compositions have been tested. The SMAs obtained were characterized by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The martensitic transformation was studied by Differential Scanning Calorimetry (DSC) and SME and SE were studied by three-point bending tests. This work shows that the CRB is a good process for making a wide variety of Cu-based SMA ribbons.

On primordial black holes from rapid turns in two-field models

We study rapid-turn trajectories in a class of two-field cosmological models, whose scalar manifold is the Poincaré disk. Background solutions in multi-field inflation, with field-space trajectories exhibiting sharp turns, can seed primordial black hole (PBH) formation. We investigate a class of exact solutions with hidden symmetry and show that they exhibit the kind of transient rapid-turn period, needed to induce PBH generation. Furthermore, we relax the symmetry condition and find, in a certain regime, modified solutions with improved behavior of the Hubble η-parameter, which preserve the desired shape of the turning rate function. Interestingly, the modified solutions describe a brief ultra-slow roll phase, followed by long-term slow roll inflation. It is notable that slow roll occurs near the center (not near the boundary) of the Poincaré disk, unlike in the standard α-attractor case.

Digital Twin for 5G and Beyond

Although many countries have started the initial phase of rolling out 5G, it is still in its infancy with researchers from both academia and industry facing the challenges of developing it to its full potential. With the support of artificial intelligence, development of digital transformation through the notion of a digital twin has been taking off in many industries such as smart manufacturing, oil and gas, construction, bio-engineering, and automotive. However, digital twins remain relatively new for 5G/6G networks, despite the obvious potential in helping develop and deploy the complex 5G environment. This article looks into these topics and discusses how digital twin could be a powerful tool to fulfill the potential of 5G networks and beyond.

Transient contact-impact behavior for passive walking of compliant bipedal robots

When bipedal robots walk, the compliance of local contact zone and whole structure usually causes high amplitude contact force and wave propagation excited by impact. The object of this paper is to analyze the transient contact-impact behavior during the walking of compliant bipedal robots (CBR) using a completely flexible body model (CFBM) and obtain its fine contact modes. The applicability of the traditional method based on completely rigid body model (CRBM) to the compliant bipedal robots is also discussed. In CFBM, the structural deformation field and inertial field are discretized by finite element theory, and the penalty function method is adopted to account for the unilateral contact constraint. The dynamic equations, strain and stress equations for the CFBM are derived. The contact forces, impact-induced wave propagation and total mechanical energy of the CBR are calculated. The results show that the relative contact motions between the foot and the slope experience two phases: (1) macroscopic oblique impact phase (duration time is 0.1∼0.2 s) and (2) rolling phase (duration time is 0.6∼0.7 s). Phase 1 consists of a series of fast normal contact-separation switches and tangential stick–slip switches. Phase 2 means there are continuous normal compression and tangential stick. Since the traditional method neglects the first phase, it is not comprehensive for investigating the CBR with impact-induced waves and vibration, especially for the case of lower coefficient of friction (COF) μ. In addition, a ‘dynamic self-locking’ phenomenon is found as μ>0.9, which will lead to the walking unstable.

Numerical simulation of boiling two-phase flow in the subchannel under static state and rolling motion

The design and operation of the offshore floating reactor cannot follow those of the land-based reactor affected by the complex marine environment. This study investigated subcooled flow boiling in the subchannel under static state and rolling motion numerically. Clear interfaces between the vapor and liquid phases are obtained.The numerical result of void fraction deviates from the experimental value by 11.9% at a given elevation. The transverse flow fields and phase-distributions are centrosymmetric under static state. The vapor only exists near the rod surfaces under static state, which is in the shape of “H”. Under rolling motion, flow fields and phase distributions vary periodically with time and the positions of the subchannel, which are significantly different from static state. At the same elevation, the time-averaged void fraction under roll motion is slightly higher than that under static state.

Seismic imaging of the Solfatara crater (Campi Flegrei caldera, southern Italy): New evidence of the fluids migration pathways in the shallow structures

Seismic imaging is used in this work, to reconstruct the shallow structure of the Solfatara crater, a surface marker of deep magmatic activity inside Campi Flegrei caldera (Southern Italy). We analyze the 1D orthogonal seismic arrays deployed in NNE-SSW directions for 400 m through the Solfatara crater during the recent active experiment RICEN (Repeated Induced Earthquake and Noise) performed in the framework of the EU project MEDSUV. Seismic data have been edited in the pre-stack stage by removing the noisy traces, low-frequency noise, and reduce the ground roll phases. Then, a velocity analysis has been carried out starting from the velocity spectrum to obtain a RMS velocity model, which has been followed by NMO, residual statics, and DMO corrections. We used the post-stack Kirchhoff migration technique before the extraction of the energy, root mean square, envelope and sweetness attributes defining the highest amplitude zones, the time-gain attribute in order to interpret the deep reflectors and the variance attribute to define the faults, discontinuities, and chaotic zones. Amplitude Versus Offset (AVO) analysis has been performed to identify the gas-saturated zone using partial angle-stacks, which is a benchmark to verify the presence of gas. The main contribution of this work is to provide a more detailed and improved seismic reflection image of the shallow depth of the Solfatara crater. The reliability of our velocity model has been assessed through the use of the Vp velocity model previously obtained by the non-linear Bayesian technique. This provides a final stack showing that the shallower minor faults and the extension of the major faults represent the main pathways for the uprising fluids. We present the visual evidence for the fluids trapped in the shallower part of the crater at depths between 20 and 50 m below the surface of the crater.

Hall-Sensor-Based Position Detection for Quick Reversal of Speed Control in a BLDC Motor Drive System for Industrial Applications

This paper proposes the novel idea of eliminating the front-end converters used indirect current (DC) bus voltage variation, thereby allowing for control of the speed of the brushless direct current (BLDC) motors in the two-quadrant operation of a permanent magnet brushless direct current (PMBLDC) motor, which is required for multiple bi-directional hot roughing steel rolling mills. The first phase of steel rolling, the manufacture of plates, strips etc., using hot slabs from the continuous casting stage, is carried out for thickness reduction, before the same is sent to the finishing mill for further mechanical processing. The hot roughing process involves applying high, compressive pressure, using a hydraulically operated mechanism, through a pair of backup rolls and work rolls for rolling. Overall, the processes consist of multiple passes of forward and reverse rolling at increasing roll speeds. The rolling process was modeled, taking into account parameters like roller dimensions, angle and length of contact, and rolling force, at various temperatures, using actual data obtained from a steel mill. From this data, speed and torque profiles at the motor shaft, covering the entire rolling process, were created. A profile-based feedback controller is proposed for setting the six-pulse inverter frequency and parameters of the pulse width modulated (PWM) waveform for current control, based on Hall sensor position, and the same is implemented for closed loop operation of the brushless direct current motor drive system. The performance enhancement of the two different controllers was also evaluated, during the rolling of 1005 hot rolled (HR) steel, and was taken into consideration in the research analysis. The entire process was simulated in the MATLAB/Simulink platform, and the results verify the suitability of an entire-drive system for industrial steel rolling applications.

Understanding the role of water-based nanolubricants in micro flexible rolling of aluminium

To comprehend the role of water-based nanolubricant in micro flexible rolling, corresponding characterisation with respect to different concentrations of nanolubricants, surface roughness variation subjected to each micro flexible rolling phase and dispersion of nanoparticles (NPs) were studied systematically. The results reveal that increasing NPs get trapped into the surfaces from the thicker zone to the thinner zone. Downward transition zone with favourable deformation features leads to the smoother surface roughness. Nanolubricants can effectively decrease rolling traces due to the beneficial nanolubrication mechanisms. Notably, the maximum reduction for rolling force is around 18% for the case under 2.0 wt% nanolubricant rolling condition. The current study provides great potential insights in how nanolubrication takes effect in microforming areas.

Linear two-dimensional stability of a Lamb-Oseen dipole as an aircraft wake model

The dynamics of perturbed aircraft wake models is investigated in the two-dimensional limit by means of a linear stability analysis. The base flow, computed by a direct numerical simulation of the incompressible Navier-Stokes equations, is a viscous counter-rotating vortex dipole obtained from an initial condition which is either a superposition of two Lamb-Oseen vortices or a vorticity sheet with elliptical vorticity distribution. The former, referred to as the Lamb-Oseen dipole (LOD), is a model for the far field of the wake and gives rise to a family of quasisteady dipoles parametrized by their aspect ratio only. The later approaches the near-field wake of a wing during the rolling phase which eventually converges towards the LOD model at later times. First, a modal stability analysis of the LOD under the assumption of a frozen base flow is performed for aspect ratios a/b ranging from 0.05 to 0.36 at various Reynolds numbers. Several families of unstable antisymmetric and symmetric modes are observed. The maximal growth rates are reached at low Reynolds numbers. The results are consistent with those obtained by Brion et al. [Phys. Fluids 26, 064103 (2014)] for the higher aspect ratio inviscid Lamb-Chaplygin dipole (LCD). However, the a posteriori verification of the validity of the frozen base flow assumption shows that, except for a few modes occurring at the highest aspect ratios and large Reynolds numbers, these two-dimensional instabilities do not survive the base flow unsteadiness due to viscous diffusion. They are thus not likely to develop in the flow. Second, we focus on the transient dynamics of the dipoles by looking for the optimal perturbations through a nonmodal stability analysis based on a direct-adjoint approach. The observed energy gains are substantial and indicate the potential of transient mechanisms. In the short time dynamics, the optimal perturbation consists of intertwined vorticity layers located within each vortex core and leading to a m=2 deformation Kelvin wave excited by the Orr mechanism. For moderate to large horizon times, the optimal perturbation takes the form of vorticity layers localized outside the vortex core which eventually give rise to the two-dimensional unstable mode unveiled by the modal analysis through a combination of Orr mechanism and velocity induction. The robustness of these modes is examined by considering the initial stage of the development of aircraft wakes. The optimal perturbations developing on an elliptic and a double-elliptic vorticity sheet present a similar structure and rely on the same mechanisms as the ones observed for the LOD but come with lower energy gains. It is concluded that the rolling-up of the vorticity sheet in the near-field of the wake does not influence significantly the linear development of these two-dimensional perturbations.

Study of Strain and Structural Peculiarities in Different Stages of Two- and Three-High Screw Rolling

This study includes the screw rolling of several blank parts of 12Kh18N10T steel on a two- and a three-roll mill, followed by modeling test rollings in the DEFORM FEM software. The test rolling results were used to evaluate changes in the dispersion of average grain size and hardness in the nonstationary and stationary phases of screw rolling. The computer-aided modeling results were used to evaluate variations in strain effective. The studies allowed identifying the changes in the average grain size and hardness in the different rolling phases and defined the compliance with the kind of changes in the average grain size, hardness, and strain effective across the blank part volume. The computer-aided modeling and test evaluation showed the differences in the kind of strain effective variations in the nonstationary phase at two- and three-high rolling.

Approximation of capsize probability using a Roll Excedance (RE) probability with a threshold chosen in roll phase plane

Abstract The paper investigates the correlation of capsizing and non-capsizing trajectories in an attempt to identify a relevant parameter for capsize probability assessment. The probability of capsize of decommissioned French naval ships, a Frigate and helicopter carrier Jeanne D'Arc, have been determined by a Monte Carlo procedure. Despite the computation cases are limited to two ships and two sea states, data sets generated tend to show in trajectory phase plane a convergence of the envelopes of non-capsized trajectories and of capsizing cycles. The presumed convergence of the envelopes would indicate a correlation between capsized and non-capsized trajectories. This suggest a faster and more cost effective probability assessment method is conceivable, using a reduced number of computations and set of data compared to Monte Carlo Method. Statistical analysis of capsizing cycles shows a normal law can approximate properly the roll rates distribution before capsize, particularly the roll rate at zero crossing and the roll rate extrema after zero crossing. However, partial match is obtained between these criteria associated to the probability obtained from Monte-Carlo method and the curve of probability of roll rate exceedance obtained with non-capsizing cycles. Additional computations, that widen the scope of ships and sea states, are in progress.

Computer-Integrated Platform for Automatic, Flexible, and Optimal Multivariable Design of a Hot Strip Rolling Technology Using Advanced Multiphase Steels

The paper presents the design and implementation of a computer system dedicated to the optimization of a hot strip rolling process. The software system proposed here involves the flexible integration of virtual models of various devices used in the process: furnace, descalers, rolling stands, accelerated cooling systems, and coiler. The user can configure an arbitrary sequence of operations and perform simulations for this sequence. The main idea of the system and its implementation details are described in the paper. Besides the computer science part, the material models describing the rolling parameters, microstructure evolution, phase transformations, and product properties are also presented. Effect of precipitation was accounted for various stages of the rolling cycle. Experimental tests were performed to generate data for identification of the models. These include plastometric tests, two-step compression tests, and dilatometric tests. Following this, physical simulations of rolling cycles were performed on Gleeble 3800 to supply data for the verification and validation of the models. Finally, case studies of modern industrial processes were performed, and the selected results are presented.

Numerical study of bubble rising in quiescent liquid under rolling motion conditions using MPS – MAFL method

Purpose of this research is to study the effect of rolling motion on single gas bubble rising in stagnant liquid. The effect of rolling motion has been incorporated in the Navier-Stokes equations and simulations have been performed using MPS – MAFL technique in two dimensions. Some experiments have also been conducted to study the phenomenon for validation purposes. The bubble trajectory, rise velocity, aspect ratio and shapes obtained from simulations have been compared with experimental data. The numerical results have been found in good agreement with the experimental findings. Effect of various factors including rolling amplitude, rolling period, rolling phases, distance from the rolling pivot, liquid properties and bubble diameter have been studied on bubble trajectory and rise velocity under the rolling motion conditions. It has been found that effect of rolling conditions is enhanced as the rolling amplitude is increased or rolling period is decreased.

Optimization-Based Nonimpact Rolling Locomotion of a Variable Geometry Truss

A variable geometry truss (VGT) is a modular truss-structured robot consisting of linear actuators and three-degree-of-freedom joints. Having a sophisticated structure, the VGT can easily be damaged when it rolls and impacts the ground. This letter proposes a nonimpact rolling locomotion scheme to avoid VGT damage. It is assumed that the VGT moves quasi-statically and maintains a static stability. There exists a control phase and a rolling phase during locomotion. During the control phase, the VGT can freely move its center of mass within the supporting polygon. During the rolling phase, the VGT's center of mass is fixed at the edge of the support polygon, and it tilts forward until a node touches the ground to make a new support polygon. This algorithm optimizes the velocity of the VGT's nodes at every time step so that the center of mass follows a desired trajectory of rolling motion. A simulation verifies that the algorithm ensures that the VGT maintains its static stability, does not tumble, and accurately follows its desired trajectory.

Analysis of surface roughness alteration in micro flexible rolling

Thin strip with varying thickness, a novel structural and functional material, is fabricated by micro flexible rolling, and has three thickness features including the thicker zone, the thinner zone and the transition zone. Rolling and roll lifting speeds determine the thickness distributions, and have a great influence on the surface roughness, then the final product quality which is of significant importance for thin materials in subsequent processing. In this study, surface roughness alteration of aluminium alloy strips during micro flexible rolling was investigated with considering the influences of rolling speeds, roll lifting speeds, thickness ratios (the ratio of the thicker zone to the thinner zone) and lubrication conditions, and the mechanisms were discussed. The results show that rolling parameters have a significant effect on the alteration of surface roughness from the thicker zone to the thinner zone along the rolling direction. The experimental observations indicate that the surface roughness of thin strips with varying thicknesses presents a decreasing tendency with the increase of contact area results from downward rolling phase along the transition zone, however, it is constantly higher than that in the upward rolling phase.

Dark energy as a remnant of inflation and electroweak symmetry breaking

It is shown that dark energy can be obtained from the interplay of the Higgs boson and the inflaton. A key element is the realization that electroweak symmetry breaking can trigger a second phase of rolling of the inflaton, which, when provided with the appropriate couplings between the fields, can be sufficiently slow to source accelerated expansion in the late time Universe. The observed dark energy density is obtained without fine-tuning of parameters or initial conditions due to an intricate conspiracy of numbers related to inflation, gravity and electroweak physics.

L-selectin expression is regulated by CXCL8-induced reactive oxygen species produced during human neutrophil rolling.

Neutrophils destroy invading microorganisms by phagocytosis by bringing them into contact with bactericidal substances, among which ROS are the most important. However, ROS also function as important physiological regulators of cellular signaling pathways. Here, we addressed the involvement of oxygen derivatives in the regulation of human neutrophil rolling, an essential component of the inflammatory response. Flow experiments using dihydroethidium-preloaded human neutrophils showed that these cells initiate an early production of intracellular ROS during the rolling phase of the adhesion cascade, a phenomenon that required cell rolling, and the interaction of the chemokine receptor CXCR2 with their ligand CXCL8. Flow cytometry experiments demonstrated that L-selectin shedding in neutrophils is triggered by ROS through an autocrine-paracrine mechanism. Preincubation of neutrophils with the NADPH oxidase complex inhibitor diphenyleniodonium chloride significantly increased the number of rolling neutrophils on endothelial cells. Interestingly, the same effect was observed when CXCL8 signaling was interfered using either a blocking monoclonal antibody or an inhibitor of its receptor. These findings indicate that, in response to CXCL8, neutrophils initiate ROS production during the rolling phase of the inflammatory response. This very early ROS production might participate in the modulation of the inflammatory response by inducing L-selectin shedding in neutrophils.