Damping Of Kinetic Energy Research Articles

Modeling collisional kinetic energy damping, heating, and cooling of ions in mass spectrometers: A tutorial perspective

Many powerful methods in mass spectrometry rely on activation of ions by high-energy collisions with gas particles. For example, multiple Collision Induced Dissociation (CID) has been used for many years to determine structural information for ions ranging from small organics to large, native-like protein complexes. More recently, Collision Induced Unfolding (CIU) has proved to be a very powerful method for understanding high-order protein structure and detecting differences between similar proteins. Quantifying the thermochemistry underlying dissociation/unfolding in these experiments can be quite challenging without reliable models of ion heating and cooling. Established physical models of CID are valuable in predicting ion heating but do not explicitly include mechanisms for cooling, which may play a large part in CID/CIU in modern instruments. Ab initio and Molecular Dynamics methods are extremely computationally expensive for modeling CID/CIU of large analytes such as biomolecular ions. In this tutorial perspective, limiting behaviors of ion kinetic energy damping, heating, and cooling set by “extreme” cases are explored, and an Improved Impulsive Collision Theory and associated software (“Ion Simulations of the Physics of Activation”, IonSPA) are introduced that can model all of these for partially inelastic collisions. Finally, examples of modeled collisional activation of native-like protein ions under realistic experimental conditions are discussed, with an outlook toward the use of IonSPA in accessing the thermochemical information hidden in CID breakdown curves and CIU fingerprints.

Large-scale vortex formation in three-dimensional rotating Rayleigh-Bénard convection

Numerical experiments are performed on three-dimensional thermal convection between parallel plates in a rotating system with a larger horizontal region than in previous studies. It is confirmed that a large-scale vortex (LSV) with positive vorticity (cyclonic) is formed over a significant part of the region and its horizontal size increases if the horizontal region is extended. The correlation analysis in the vertical direction shows that the small-scale motion has a typical structure of the baroclinic vortex of thermal convection in the rotating system, whereas the large-scale motion is a barotropic vortex that is not associated with thermal convection. A horizontal spectral analysis of the individual terms in the kinetic energy equation reveals that the nonlinear effect of the small-scale vortex motion caused by the buoyancy force induces a large-scale toroidal component, and that the LSV is maintained by the balance between the nonlinear effect and the viscous dissipation of the large-scale motion. The results of this analysis indicate the importance of kinetic energy damping mechanism for the appearance of LSVs. When weak damping operates at larger scales, it is expected that the maximum extent of the vortex appears even if the horizontal region is extended further. On the other hand, the emergence of LSVs will be prevented when strong enough damping is effective at larger scales.

Integrated Textile Supercapacitors Enhanced with Energy‐Absorbing Spacer Fabrics and Ti3C2Tx MXene

AbstractThe rapid development of wearable electronics requires energy storage devices capable of withstanding both static and dynamic deformations. The versatility of textile supercapacitors renders them promising candidates, but their low electrochemical performance especially under mechanical deformation, poses many limitations for practical use. In this study, MXene‐based textile supercapacitors are designed and fabricated using hierarchical spacer fabrics as the skeleton to provide robust mechanical support and stable performance. Ti3C2Tx MXene is adopted as the current collector and active material for the spacer fabric supercapacitor, resulting in an impressive areal capacitance of 415 mF cm−2 with a MXene loading of 4.2 mg cm−2. Remarkable stability and durability are achieved in the form of three‐dimensional (3D) textile supercapacitors, even under both static and dynamic deformations. The compressive behaviors of these supercapacitors can be easily adjusted (e.g., from 10 to 168 KPa at 50% compression) by altering the spacer fabric structure, demonstrating their energy‐absorption (damping of kinetic energy) capability and their potential to meet the requirements of various wearable applications.

Increasing Collisional Activation of Protein Complexes Using Smaller Aperture Source Sampling Cones on a Synapt Q-IM-TOF Instrument with a Stepwave Source.

Quadrupole ion mobility time-of-flight (Q-IM-TOF) mass spectrometers have revolutionized investigation of native biomolecular complexes. High pressures in the sources of these instruments aid transmission of protein complexes through damping of kinetic energy by collisional cooling. As adducts are removed through collisional heating (declustering), excessive collisional cooling can prevent removal of nonspecific adducts from protein ions, leading to inaccurate mass measurements, broad mass spectral peaks, and obfuscation of ligand binding. We show that reducing the source pressure using smaller aperture source sampling cones (SC) in a Waters Synapt G2-Si instrument increases protein ion heating by decreasing collisional cooling, providing a simple way to enhance removal of adducted salts from soluble proteins (GroEL 14-mer) and detergents from a transmembrane protein complex (heptameric Staphylococcus aureus α-hemolysin, αHL). These experiments are supported by ion heating and cooling simulations which demonstrate reduced collisional cooling at lower source pressures. Using these easily swapped sample cones of different apertures is a facile approach to reproducibly extend the range of activation in Synapt-type instruments.

Predicting pillar burst by an explicit modelling of kinetic energy

Violent pillar failures known as pillar bursts are suspected to be a possible cause of large collapses in underground mines. A classical stability criterion for mine pillars, based on the relative stiffness of the host rock and the pillars during their post-peak unloading, was proposed by Starfield & Fairhurst (1968)6 and further demonstrated by Salamon (1970)7. An energy balance indicates that an excess kinetic energy is generated when this pillar stability criterion is violated. The present study focuses on demonstrating how an explicit numerical modelling method may be used to calculate and locate the damping of this kinetic energy during pillar failure, considering simple 2D geometries. Arguments in favour of the validation of the numerical results are provided by comparison to analytical calculations and to an empirical classification of rockbursts proposed by Ortlepp (1997)1. The good correlation between numerical, analytical and empirical approaches suggest that explicit numerical modelling of kinetic energy damping, following a procedure proposed in this paper, could be a useful tool for predicting zones submitted to a pillar burst hazard in underground mines and for consequently optimizing the mining method.

About assembling and operation of safety system with pneumohydraulic buffers of overhead cranes

Analysis of hoist crane’s park shows that more of them are worked-out their rated source,and safety systems of cranes have unsatisfactory conditions. It establishes situation for developmentnew reliable safety systems of cranes in particular in dead-ends of crane runway, which will providesafe operation of hoist cranes preventing accidents.It is shown that assembling of end stops must be realized with crane’s buffers and by designand producing of hoist cranes organizations. It is pointed that rigidity of end stop must be calculatedin such way that impact of crane into end stop must be not very hard for safe stop of hoist cranesand it must be provided full and smooth damping of kinetic energy of crane. The method ofsettlements of end stop’s rigidity is shown.It is concluded that operation of safety system with pneumohydraulic buffers allows to stopoverhead cranes running into end stops with rated speed and with specifiable decelerationsustaining all kinetic energy of crane. It decreases loads on crane’s metal constructions and cranegirders and prevents it’s destroying decreasing volume of repair works conducting on a crane andincreases safety during operation of the hoist cranes.

Electrodynamic Brakes for Unmanned Aerial Vehicles

A generalized mathematical model allowing to investigate dynamic processes in electromagnetic damping elements in unmanned aerial vehicles brake system in transients and steady state was obtained. An application of a mathematical model in some particular cases of the operation of a damper under the action of a constant external force in the mode damping and also in the mode damping of kinetic energy of abutting objects was shown.

Vertical Dynamics Analysis on Evaluation Standard of Ballastless Track Damping Effect

Vibration and noise reduction was the trend of ballastless track, however, evaluation of different types of damping effect of the track was not easy to achieve. The orbit of the traditional vertical displacement of the components, to evaluate the damping effect of the acceleration was not accurate when the difference between the track structure larger. From the principle of energy conservation, the flexibility to select a long pillow, long pillow vertical, orbital plate of three ballastless track fragments, respectively, without the establishment of a vehicle - track couplin model, the vertical acceleration, the vertical track of the various components of displacement, acceleration, maximum kinetic energy was calculated out when train speed was 250km/h by numerical simulation methods. By analyzing the relationship between their body vertical acceleration and found that the largest track the existence of kinetic energy correlation between the changes in, made with the greatest kinetic energy damping effect as the track of one of the evaluation criteria, and it was easy to implement.

Excitation energy division in the quasielastic region from reactions of 12 MeV/nucleon 48Ti with 150Nd.

Internal excitation of projectile-like fragments and target-like fragments was investigated for the system 12 MeV/nucleon $^{48}$Ti${+\mathrm{}}^{150}$Nd, by measuring the discrete \ensuremath{\gamma} rays emitted by both fragments in coincidence with the charge-separated projectile-like fragments. Two quasielastic exit channels of the projectile-like fragments were studied: Z=20 and Z=22. Characteristic \ensuremath{\gamma} rays were used to determine the average masses of products, after separation and neutron evaporation, as a function of kinetic energy loss. Our results show that the mass-to-charge equilibration occurs quickly for the Z=20 exit channel, but is slower for the Z=22 channel. Comparison between the average masses of products with the masses calculated using the statistical model show that the excitation energy is divided approximately equally between the projectile-like and the target-like fragments for the Z=20 exit channel. The excitation energy appears to be divided equally up to \ensuremath{\sim}105 MeV of the kinetic energy loss corresponding to \ensuremath{\sim}36% of kinetic energy damping. This result is consistent with predictions made by the stochastic nucleon-exchange models for a small kinetic energy loss.

The analysis of simultaneous mass and charge data from damped heavy-ion reactions

Procedures are described to identify simultaneously the mass and charge of projectile-like fragments produced in damped heavy-ion reactions and derived from data recorded with a ΔE− E time-of-flight telescope. Corrections for the effects of particle emission from the primary reaction products are also discussed. The average properties of the resultant charge, neutron and mass distributions can be described by six parameters obtained from a two-dimensional Gaussian fit. These parameters, which are a function of kinetic energy damping, summarize the properties of nucleon exchange in the damped process. After the effects of experimental resolution (in two dimensions, charge and mass) and the effects of binning of the data have been taken into account, most physically relevant quantities of interest and their uncertainties can be calculated with the formulas presented.

One- and two-body dissipation in heavy-ion collisions

A microscopic theory has been formulated for one- and two-body dissipation in collisions between two heavy nuclei. With a nucleon-nucleon interaction as the basic perturbation in a density matrix approach with “linear response” approximations, the one- and two-body nuclear friction coefficients for the 40 Ca + 40 Ca system have been calculated and their dependence on relative kinetic energy and smearing of nuclear single-particle states was obtained. The results of our calculation show that: (a) the combined one- and two-body friction coefficients compare favourably with phenomenological values, (b) the one-body dissipation is more effective than two-body in kinetic energy damping, while both the mechanisms are comparable for the damping of relative angular momentum, (c) the importance of the two-body friction compared to one-body increases at higher relative kinetic energies and (d) the effect of introducing a smearing in nuclear levels appears as a lowering of nuclear friction.

Nucleon diffusion and absence of fusion in strongly damped collisions ofKr86onEr166

The measured element distribution in collisions of $^{86}\mathrm{Kr}$ with $^{166}\mathrm{Er}$ at ${E}_{\mathrm{c}.\mathrm{m}.}=463$ MeV is examined in the framework of the one-body dissipation model with an empirical potential energy surface deduced from fission. The fragment $Z$ distributions over the entire range of kinetic energy damping are consistent with a driftless nucleon diffusion process. No evidence is found for a fusion-fission component.NUCLEAR REACTIONS $^{166}\mathrm{Er}(^{86}\mathrm{Kr},{A}_{L}){A}_{H}{E}_{\mathrm{c}.\mathrm{m}.}=326 \mathrm{and} 463$ MeV. Measured $\ensuremath{\sigma}({A}_{L}, Q \mathrm{value})$; deduced reaction mechanism.

Equilibrium velocities of a planetesimal population

The random velocities v( m) of planetesimal populations specified by maximum and minimum masses and a number density n( m) ∝ m − q are calculated interatively based on two different physical models involving ratios of rates: (1) excitation of kinetic energy by gravitational perturbation and elastic collision equal to damping of kinetic energy by inelastic collisions; and (2) excitation of kinetic energy a ratio b (∼3 usually) to doubling of mass. Model (2) follows the theory of Safronov closely. Both physical models are developed approximately, using averaged factors for collision dissipation and velocity ratios, and then more precisely, allowing for reference orbit differences and for plausible variations in collisional energy dissipation with impact velocity and planetesimal mass ratios. The approximate model (2) agrees reasonably well with the results of Safronov. Both precise models are applied to populations approximating those generated by the calculations of Greenberg, Cox, and Wetherill, producing qualitatively similar velocities v( m). These results encourage analytic models of planetesimal population growth, incrementing masses and calculating velocity distributions in alternate steps. The principal improvement needed in the models is more realistic collision energy partitioning.

Dissipation, mass exchange and the microscopic time scale of heavy-ion collisions

The time scale provided by the nucleon exchange mechanism in heavy-ion reactions is employed to study kinetic energy damping. The experimental kinetic energy lost per nucleon exchanged in Kr- and Xe-induced reactions is observed to decrease linearly with the total kinetic energy loss. These results, which are consistent with energy dissipation and nucleon exchange occuring on a similar time scale, are compared with the predictions of a one-body dissipation mechanism and a diffusion model.