Gear Rattle during a start-up transient in a driveline equipped with a tuneable torsional Vibration Damper with Magneto-Rheological Elastomers

The paper reports a numerical investigation on the dynamic behaviour of a vehicle driveline, equipped with a Torsional Vibration Damper (TVD) based on Magneto-Rheological Elastomeric (MRE) spring elements, during the start-up transient considering an abrupt manoeuvre of clutch engagement. The TVD device consists of a flywheel and a damper disk, with interposed some elastomeric samples which react for relative angular displacements of the two disks. The dynamical parameters of the TVD can be properly tuned by varying the magnetic field surrounding the MRE springs to mitigate the torsional oscillations of the flywheel, causes of many undesired inconveniences as critical speeds or vibro-acoustic issues. The present study promotes the use of the MRE torsional vibration damper to reduce the annoying vibroacoustic phenomenon of “gear rattle” arising in the unloaded gear pairs of the gear box, during and after the rapid clutch engagement transients in the vehicle start-up phase and is conducted on a simplified automotive driveline equipped with a dry clutch. The possibility of quickly tuning the mechanical properties of the MRE-TVD, makes this device particularly eligible for suppressing the above disturbance, adapting to the various operative conditions of the automotive driveline. Results of the analysis, by the help of a Gear Rattle Index (GRI), demonstrate the effectiveness of the proposed device in reducing the vibroacoustic phenomenon during the transient phases of the vehicle start-up, until the vehicles speed conditions are reached.

Role of extended gravity theory in matter bounce dynamics

In this work, we have studied some bouncing cosmologies in the frame work of $f(R,T)$ gravity. The bouncing scenario has been formulated to avoid the big bang singularity. The physical and geometrical parameters are investigated. The effect of the extended gravity theory on the dynamical parameters of the model is investigated. It is found that, the $f(R,T)$ gravity parameter affects the cosmic dynamics substantially. We have also, tested the model through the calculation of the cosmographic coefficients and the $Om(z)$ parameter. A scalar field reconstruction of the bouncing scenario is also carried out. The stability of the model are tested under linear, homogeneous and isotropic perturbations.

Ozone Variation during the Development of a Tropical Cyclone: Case Study

The aim of this work was to study the variation in the total ozone column amount (TOC) during the life cycle of the tropical cyclone (TC) that occurred over the northwest Indian Ocean from 14 to 25 October 2008. This goal was achieved through examining the behavior of the tropical cyclone tilt under vertically varying background flows in association with the cyclone development. Thus, the vertical wind shear (VWS) was estimated as one of the most important dynamical parameters related to TC formation and intensity changes. Moreover, we estimated the variations in the daily values of TOC during the period of cyclone activity. We found that the magnitude of VWS increased during the growth period, and VWS weakened during the decay period. Anomalies of daily TOC were found to reduce steadily before and during the cyclone formation, followed by an increasing trend after the dissipation of cyclone. It was also found that during the development of the tropical cyclone, an outflow developed in the upper levels, having high velocities that extended beyond the tropopause up to the lower stratosphere. As a result, the lowest value of TOC during the tropical cyclone was due to a large amount of injected water vapor from the troposphere into the stratosphere through the convection processes. This was mostly photo-dissociated into OH and atomic O by deep solar radiation in the upper and lower stratosphere, leading to a severe reduction in stratospheric ozone.

A General Origin for Multiplanetary Systems With Significantly Misaligned USP Planets

Ultra-short-period (USP) planets are exoplanets that have orbital periods of less than one day and are unique because they orbit inside the nominal magnetic truncation gap of their host stars. In some cases, USP planets have also been observed to exhibit unique dynamical parameters such as significant misalignments in inclination angle with respect to nearby planets. In this paper, we explore how the geometry of a multiplanet system hosting a USP planet can be expected to evolve as a star ages. In particular, we explore the relationship between the mutual inclination of the USP planet and the quadrupole moment (J 2) of the host star. We use secular perturbation theory to predict the past evolution of the example TOI-125 system, and then confirm the validity of our results using long-term N-body simulations. Through investigating how the misalignment between the candidate USP planet and the three other short-period planets in the TOI-125 system arose, we intend to derive a better understanding of the population of systems with misaligned USP planets and how their observed parameters can be explained in the context of their dynamical histories.

Classical T Tauri stars: accretion, wind, dust

Classical T Tauri stars (CTTS) are at the early evolutionary stage when the processes of planet formation take place in the surrounding accretion disks. Most of the observed activity in CTTS is due to magnetospheric accretion and wind flows. Observations of the accreting gas flows and appearance of the line-dependent veiling of the photospheric spectrum in CTTS are considered. Evidence for the dusty wind causing the observed irregular variability of CTTS is presented. Photometric and spectroscopic monitoring of two CTTS, RY Tau and SU Aur, has been carried out atthe Crimean Astrophysical Observatory since 2013 aimed at studying the dynamics of accretion and wind flows on time scales from days to years. The observed variations in the dynamical parameters may be caused by changes in the accretion rate and in the global magnetic fields of CTTS.

Kantowski–Sachs Tsallis holographic dark energy model with sign-changeable interaction

In this work devoted to the investigation of the Tsallis holographic dark energy (IR cut-off is Hubble radius) in homogeneous and anisotropic Kantowski–Sachs Universe within the frame-work of Saez–Ballester scalar tensor theory of gravitation. We have constructed non-interacting and interacting Tsallis holographic dark energy models by solving the field equations using the relationship between the metric potentials. This relation leads to a viable deceleration parameter model which exhibits a transition of the Universe from deceleration to acceleration. In interacting case, we focus on sign-changeable interaction between Tsallis holographic dark energy and dark matter. The dynamical parameters like equation of state parameter, energy densities of Tsallis holographic dark energy and dark matter, deceleration parameter, and statefinder parameters of the models are explained through graphical representation. And also, we discussed the stability analysis of the our models.

Multi-electron excitation contributions towards primary and satellite states in the photoelectron spectrum

The computation of Dyson orbitals and corresponding ionization energies has been implemented within the Equation of Motion Coupled Cluster Singles, Doubles, and Perturbative Triples (EOMCC3) method. Coupled to an accurate description of the electronic continuum via a time-dependent density functional approach using a multicentric B-spline basis, this yields highly accurate photoionization dynamical parameters (cross-sections, branching ratios, asymmetry parameters, and dichroic coefficients) for primary states (1h) as well as satellite states of (2h-1p) character. Illustrative results are presented for the molecular systems H2O, H2S, CS, CS2 and (S)-propylene oxide (a.k.a. methyloxirane).

The discharge initiation in vacuum gap by moderate intensity optical range radiation

The hypothesis of discharge initiation in vacuum gap by optical range radiation based on previously obtained experimental data. During the laser pulse interaction with electrode erosion products the glow discharge has ignited. In result of ioniza-tion-overheating instability the discharge has had current channel contraction and has transferred to arc. The dependences of material of target thermo dynamical parameters on the minimal and threshold laser pulse energy have demonstrated. The threshold laser pulse energy – the energy which enough to effective impact on the laser plasma.

Analyzing the Effect of Temperature on Squash Ball Impacts Using High-Speed Camera Recordings

Description of the impact characteristics of different types of balls has a great importance in sport science and in engineering. The primary objective of the present paper is to investigate the effect of the temperature on the impacts of different types of squash balls from a given company. The shots were performed using a self-built air-cannon. The impacts were recorded by a high-speed camera and the recorded videos were analyzed by an image-processing method based on a background subtraction technique. Summarizing the main dynamical parameters, we can conclude that increasing the initial speed will decrease the contact time, the coefficient of restitution (COR) and the rebound resilience, whereas these parameters increase at elevated temperatures. The compression tests revealed that within the low velocity range the deformation of the ball’s material and not the compression of the inner gas is the main contribution in the force needed to compress the ball. However, when the ball suffers large deformations, the internal air pressure has a huge effect on the rebound behavior. The measurements revealed that there is an optimal initial velocity distinct from the maximum one where the rebound velocity of the ball is higher than in all other cases. From the results we can state that the ball's overall stiffness grows as the temperature increases.