Relative Kinetic Energy Research Articles

Упругое рассеяние атомных пар Mo-Mo, Mo-S и S-S в диапазоне относительных кинетических энергий 2-200 eV

AbstractThe interatomic binary potentials of Mo-Mo, Mo-S and S-S, approved by Molecular Dynamics, were used to calculate elastic phase shifts and cross sections of the atomic pairs in the relative kinetic energy range of 2–200 eV. It is expected the obtained differential and integral cross sections to be of help to describe sputtering of MoS_2 nanometer layers in design of perspective devices of nanoelectronics and photonics.

Experimental investigation into deposition/splashing behavior of droplets impacting vibrating surface

An experimental investigation is performed into the behavior of ethanol droplets impacting on a vibrating stainless steel surface. In characterizing the impact behavior, the dimensionless kinetic energy of the droplet prior to its impact on the surface is represented by the original Weber number (We). Meanwhile, the dimensionless relative impact kinetic energy of the droplet as it impacts the vibrating surface, and thus undergoes a change in its relative impact speed, is represented by the relative Weber number (Wer). Impact experiments are performed for various values of the original Weber number We and vibration frequency f. The impact behavior in each case is classified as either post-spreading deposition or crown splashing. It is shown that for a static (non-vibrating) surface, the critical Weber number for the generation of splashing is Wec = 400. Furthermore, for a given impact speed and vibration frequency, if no splashing occurs without vibration but splashing takes place after vibration, the difference between the original Weber number (We) and the critical Weber number (Wec) is proportional to the additional impact Weber number provided by the vibrating surface, that is, (Wer − Wec). For a given relative impact speed, a higher vibration frequency ƒ results in a greater relative impact distance during splashing and a larger effective impact energy. Overall, the experimental results show that the relation between We and Wer for the generation of splashing is given as We=(−cf/(1−cf))Wer+(1/(1−cf))Wec, where c=3.45×10−4.

Coordinated collision avoidance for connected vehicles using relative kinetic energy density

Vehicular collision often leads to serious casualties and traffic congestion, and the consequences are worse for multiple-vehicle collision. Many previous works on collision avoidance have only focused on the case for two consecutive vehicles using on-board sensors, which ignored the influence on upstream traffic flow. This paper proposes a novel coordinated collision avoidance (CCA) strategy for connected vehicles, which has potential to avoid collision and smooth the braking behaviors of multiple vehicles, leading to an improvement of traffic smoothness. Specifically, model predictive control (MPC) framework is used to formulate the CCA into an optimization problem, where the objective is to minimize the total relative kinetic energy density (RKED) among connected vehicles. Monte Carlo simulations are used to demonstrate the effectiveness of proposed CCA strategy by comparison with other two strategies. Among all the three control strategies, the RKED based control strategy shows the best performance of collision avoidance, including the best crash prevention rates (99.2 % on dry asphalt road and 90.5 % on wet asphalt road) and the best control of distance headways between vehicles.

Stark-induced adiabatic Raman ladder for preparing highly vibrationally excited quantum states of molecular hydrogen

We present a multi-color ladder excitation scheme that exploits Stark-induced adiabatic Raman passage to selectively populate a highly excited vibrational level of a molecule. We suggest that this multi-color coherent ladder excitation provides a practical way of accessing levels near the vibrational dissociation limit as well as the dissociative continuum, which would allow the generation of an entangled pair of fragments with near-zero relative kinetic energy. Specifically, we consider four- and six-photon coherent excitation of molecular hydrogen to high vibrational levels via intermediate vibrational levels, which are pairwise coupled by two-photon resonant interaction. Using a sequence of three partially overlapping, single-mode, nanosecond laser pulses we show that the sixth vibrational level of H2, which is too weakly coupled to be easily accessed by direct two-photon Raman excitation from the ground vibrational level, can be efficiently populated without leaving any population stranded in the intermediate level. Furthermore, we show that the fourteenth vibrational level of H2, which is the highest vibrational level in the ground electronic state with a binding energy of 22 meV, can be efficiently and selectively populated using a sequence of four pulses. The present technique offers the unique possibility of preparing entangled quantum states of H atoms without resorting to an ultracold system.

Secondary motion in three-dimensional branching networks

A major aim of the present work is to understand and thoroughly document the generation, the three-dimensional distribution, and the evolution of the secondary motion as the fluid progresses downstream through a branched network. Six generations (G0-G5) of branches (involving 63 straight portions and 31 bifurcation modules) are computed in one go; such computational challenges are rarely taken in the literature. More than 30 × 106 computational elements are employed for high precision of computed results and fine quality of the flow visualization diagrams. The study of co-planar vis-à-vis non-planar space-filling configurations establishes a quantitative evaluation of the dependence of the fluid dynamics on the three-dimensional arrangement of the same individual branches. As compared to the secondary motion in a simple curved pipe, three distinctive features, viz., the change of shape and size of the flow-cross-section, the division of non-uniform primary flow in a bifurcation module, and repeated switchover from clockwise to anticlockwise curvature and vice versa in the flow path, make the present situation more complex. It is shown that the straight portions in the network, in general, attenuate the secondary motion, while the three-dimensionally complex bifurcation modules generate secondary motion and may alter the number, arrangement, and structure of vortices. A comprehensive picture of the evolution of quantitative flow visualizations of the secondary motion is achieved by constructing contours of secondary velocity [Formula: see text], streamwise vorticity [Formula: see text], and [Formula: see text] iso-surfaces. It is demonstrated, for example, that for in-plane configuration, the vortices on any plane appear in pair (i.e., for each clockwise rotating vortex, there is an otherwise identical anticlockwise vortex), whereas the vortices on a plane for the out-of-plane configuration may be dissimilar, and there may even be an odd number of vortices. We have formulated three new parameters (ES/P , [Formula: see text], and [Formula: see text]) for a quantitative description of the overall features of the secondary flow field. [Formula: see text] represents a non-uniformity index of the secondary flow in an individual branch, ES/P represents the mass-flow-averaged relative kinetic energy of the secondary motion in an individual branch, and [Formula: see text] provides a measure of the non-uniformity of the secondary flow between various branches of the same generation Gn. The repeated enhancement of the secondary kinetic energy in the bifurcation modules is responsible for the occurrence of significant values of ES/P even in generation G5. For both configurations, it is found that for any bifurcation module, the value of ES/P is greater in that daughter branch in which the mass-flow rate is greater. Even though the various contour plots of the complex secondary flow structure appear visually very different from one another, the values of [Formula: see text] are found to lie within a small range ([Formula: see text]) for the six-generation networks studied. It is shown that [Formula: see text] grows as the generation number Gn increases. It is established that the out-of-plane configuration, in general, creates more secondary kinetic energy (higher ES/P ), a similar level of non-uniformity in the secondary flow in an individual branch (similar [Formula: see text]), and a significantly lower level of non-uniformity in the distribution of secondary motion among various branches of the same generation (much lower [Formula: see text]), as compared to the in-plane arrangement of the same branches.

Width of NΔ and ΔΔ states

It is seen by a coupled-channel calculation that in the two-baryon N-Delta or Delta-Delta system the width of the state is greatly diminished due to the relative kinetic energy of the two baryons, since the internal energy of the particles, available for pionic decay, is smaller. A similar state dependent effect arises from the centrifugal barrier in N-Delta or Delta-Delta systems with non-zero orbital angular momentum. The double-Delta width can become even smaller than the free width of a single Delta. This has some bearing to the interpretation of the d'(2380) resonance recently discovered at COSY.

Influence of collective nonideal shielding on fusion reaction in partially ionized classical nonideal plasmas.

The collective nonideal effects on the nuclear fusion reaction process are investigated in partially ionized classical nonideal hydrogen plasmas. The effective pseudopotential model taking into account the collective and plasma shielding effects is applied to describe the interaction potential in nonideal plasmas. The analytic expressions of the Sommerfeld parameter, the fusion penetration factor, and the cross section for the nuclear fusion reaction in nonideal plasmas are obtained as functions of the nonideality parameter, Debye length, and relative kinetic energy. It is found that the Sommerfeld parameter is suppressed due to the influence of collective nonideal shielding. However, the collective nonideal shielding is found to enhance the fusion penetration factor in partially ionized classical nonideal plasmas. It is also found that the fusion penetration factors in nonideal plasmas represented by the pseudopotential model are always greater than those in ideal plasmas represented by the Debye-Hückel model. In addition, it is shown that the collective nonideal shielding effect on the fusion penetration factor decreases with an increase of the kinetic energy.

Wake Dynamics Resulting from Trailing-Edge Spanwise Sinusoidal Perturbation

The investigation identified and characterized the changes in the near wake of a bluff body produced by trailing-edge spanwise sinusoidal perturbation, which resulted in an overall reduction in the base drag. This study investigated a flat-plate body with an elliptic leading edge and blunt trailing edge, with and without trailing-edge spanwise sinusoidal perturbation. Base-pressure measurements were used to quantify the base-drag reduction associated with spanwise sinusoidal perturbation. In addition, particle-image-velocimetry measurements were performed in the near wake with and without spanwise sinusoidal perturbation, and a proper-orthogonal-decomposition analysis was used to analyze the velocity data. The findings suggest that the spanwise sinusoidal perturbation redistributed the relative kinetic energy, which enhanced the streamwise vortices and suppressed the von Kármán–Bénard vortices as a result.

Quantum shielding effects on the Gamow penetration factor for nuclear fusion reaction in quantum plasmas

The quantum shielding effects on the nuclear fusion reaction process are investigated in quantum plasmas. The closed expression of the classical turning point for the Gamow penetration factor in quantum plasmas is obtained by the Lambert W-function. The closed expressions of the Gamow penetration factor and the cross section for the nuclear fusion reaction in quantum plasmas are obtained as functions of the plasmon energy and the relative kinetic energy by using the effective interaction potential with the WKB analysis. It is shown that the influence of quantum screening suppresses the Sommerfeld reaction factor. It is also shown that the Gamow penetration factor increases with an increase of the plasmon energy. It is also shown that the quantum shielding effect enhances the deuterium formation by the proton-proton reaction in quantum plasmas. In addition, it is found that the energy dependences on the reaction cross section and the Gamow penetration factor are more significant in high plasmon-energy domains.

Improving Mesoscale Altimetric Data From a Multitracer Convolutional Processing of Standard Satellite-Derived Products

Multisatellite measurements of altimeter-derived sea surface height (SSH) have provided a wealth of information on the ocean. Yet, horizontal scales below 100 km remain scarcely resolved. Especially, in the Mediterranean Sea, an important fraction of the mesoscale range, characterized by a small Rossby radius of deformation of 15–20 km, is not properly retrieved by altimeter-derived gridded products. Here, we investigate a novel processing of AVISO products with a view to resolving the horizontal scales sensed by current along-track altimeter data. The key feature of our framework is the use of linear convolutional operators to model the fine-scale SSH detail as a function of different sea surface fields, especially optimally interpolated SSH and sea surface temperature (SST). The proposed model embeds the surface quasi-geostrophic SST–SSH synergy as a special case. Using an observing system simulation experiment with simulated SSH data from model outputs in the Western Mediterranean Sea, we show that the proposed approach has the potential for improving current optimal interpolations of gridded altimeter-derived SSH fields by more than 20% in terms of relative SSH and kinetic energy mean square error, as well as in terms of spectral signatures for horizontal scales ranging from 30 to 100 km. Our results also suggest that SST–SSH relationship may only play a secondary role compared with the interscale SSH cascade. We further discuss the relevance of the proposed approach in the context of future altimetric satellite missions.

The effect of vortex merging and non-merging on the transfer of modal turbulent kinetic energy content

A defining feature of the turbulent free shear layer is that its growth is hindered by compressibility effects, thus limiting its potential to sufficiently mix the injected fuel and surrounding airstream at the supersonic Mach numbers intrinsic to the combustor of air-breathing hypersonic vehicles. The introduction of streamwise vorticity is often proposed in an attempt to counteract these undesired effects. This fact makes the strategy of introducing multiple streamwise vortices and imposing upon them certain modes of mutual interaction in order to potentially enhance mixing an intriguing concept. However, many underlying fundamental characteristics of the flowfields in the presence such interactions are not yet well understood; therefore, the fundamental physics of these flowfields should be independently investigated before the explicit mixing performance is characterized. In this work, experimental measurements are taken with the stereoscopic particle image velocimetry technique on two specifically targeted modes of vortex interaction—the merging and non-merging of two corotating vortices. The fluctuating velocity fields are analyzed utilizing the proper orthogonal decomposition (POD) in order to identify the content, organization, and distribution of the modal turbulent kinetic energy content of the fluctuating velocity eigenmodes. The effects of the two modes of vortex interaction are revealed by the POD analysis which shows distinct differences in the modal features of the two cases. When comparing the low-order eigenmodes of the two cases, the size of the structures contained within the first ten modes is seen to increase as the flow progresses downstream for the merging case, whereas the opposite is true for the non-merging case. Additionally, the relative modal energy contribution of the first ten eigenmodes increases as the vortices evolve downstream for the merging case, whereas in the non-merging case the relative modal energy contribution decreases. The POD results show that the vortex merging process reorients and redistributes the relative turbulent kinetic energy content toward the larger-scale structures within the low-order POD eigenmodes. This result suggests that by specifically designing the vortex generation system to impose preselected modes of vortex interaction upon the flow it is possible to exert some form of control over the downstream evolution and distribution of the global and modal turbulent kinetic energy content.

Production of high density molecular beams with wide velocity scanning.

We describe modifications of a pulsed rotating supersonic beam source that improve performance, particularly increasing the beam density and sharpening the pulse profiles. As well as providing the familiar virtues of a supersonic molecular beam (high intensity, narrowed velocity distribution, and drastic cooling of rotation and vibration), the rotating source enables scanning the translational velocity over a wide range. Thereby, beams of any atom or molecule available as a gas can be slowed or speeded. Using Xe beams in the slowing mode, we have obtained lab speeds down to about 40 ± 5 m/s with density near 10(11) cm(-3) and in the speeding mode lab speeds up to about 660 m/s and density near 10(14) cm(-3). We discuss some congenial applications. Providing low lab speeds can markedly enhance experiments using electric or magnetic fields to deflect, steer, or further slow polar or paramagnetic molecules. The capability to scan molecular speeds facilitates merging velocities with a codirectional partner beam, enabling study of collisions at very low relative kinetic energies, without requiring either beam to be slow.

Elastic scattering process for argon ions and oxygen atoms in 10-500 eV range of relative kinetic energies

SynopsisThe interaction potential between oxygen atoms (3P state) and argon ions (2P state) has been calculated on ab initio level in the vast range of internuclear distances (0.8-100 a.u.). The elastic scattering process has been studied for relative kinetic energies of 10-500 eV.

Velocity Map Imaging Study of Charge-Transfer and Proton-Transfer Reactions of CH3 Radicals with H3(.).

The velocity map imaging method has been applied to crossed beam studies of charge transfer and proton transfer between methyl (CH3) radicals formed by pyrolysis and H3(+) cations over the collision energy range from 1.2 to 3.4 eV. Vibrational excitation in the H3(+) reactants plays an important role both in promoting endoergic charge transfer and in supplying energy to the products of the proton-transfer reaction. Excited H3(+) reactants with vibrational energy in excess of the barrier lead to energy-resonant charge transfer via long-range collisions. A small fraction of collisions that take place at low impact parameters appear to form charge-transfer products with higher levels of internal excitation. The proton-transfer reaction exhibits direct, stripping-like dynamics. Consistent with the kinematics of proton transfer, incremental kinetic energy supplied to the reactants is strongly directed into product relative kinetic energy, as predicted by the concept of "induced repulsive energy release".

Longitudinal collision mitigation via coordinated braking of multiple vehicles using model predictive control

The vehicular collision can lead to serious casualties and traffic congestions, especially multiple-vehicle collision. Most recent studies mainly focused on collision warning and avoidance strategies for two consecutive vehicles, but only a few on multiple-vehicle situations. This study proposes a coordinated brake control CBC strategy for multiple vehicles to minimize the risk of rear-end collision using model predictive control MPC framework. The objective is to minimize total impact energy by determining the desired braking force, where the impact energy is defined as the relative kinetic energy for a consecutive pair of vehicles. Under the MPC framework, this problem is further converted to a quadratic programming at each time step for numerical computations. To compare the performance, three other control strategies, i.e. direct brake control DBC, driver reaction based brake control DRBC and linear quadratic regulator LQR control are also considered in this paper. The simulation results, in both a typical scenario and a huge number of scenarios under stochastic situations, show that CBC strategy has the best performance among these four strategies. The proposed CBC strategy has the potential to avoid the collision among a group of vehicles, and to mitigate the impact in cases where the collision is unavoidable.

Development of a miniature time-of-flight mass/charge spectrometer for ion beam source analyzing

To diagnose the vacuum arc discharge process, a miniature time-of-flight mass spectrometer (TOF MS) with compact structure was developed for cathodic vacuum arc discharge ion source. An orthogonal acceleration region and an angle reflector were employed for the miniature TOF MS instrument. Especially, a small extraction hole in the acceleration region was set for getting relative high mass resolution, an ion detector with a large rectangular effective area were designed for getting wide ion kinetic energy distribution measurement capability. The compact size of the TOF MS is 413mm×250mm×414mm, the mass resolution is 600 (FWHM) and the detection range of ion kinetic energy is two orders of magnitude. A copper cathodic vacuum arc discharge ion source was tested and the charge states of Cu ions from 1+ to 3+ were detected. The miniature TOF MS was successfully developed with relative high mass resolution and wide ion kinetic energy distribution measurement capability which could be used to diagnose the cathodic vacuum arc discharge plasma.

Elastic scattering of an oxygen atom on a silicon atom in the 10–500 eV range of relative kinetic energies

The potential of interaction between oxygen and silicon atoms in a range of interatomic distances within 0.75–11.5 au has been calculated from first principles (ab initio) using the multiconfigurational interaction (MRCI) method with the aug-pp-AVQZ basis set of atomic wave functions. An analytical approximation of the numerically calculated potential is presented. The elastic scattering of oxygen on silicon was studied in the 10–500 eV range of relative kinetic energies. The obtained differential, integral, and transport scattering cross sections and the proposed interatomic potential can be used in the field of nanotechnologies.

Usual Approximations to the Equations of Atmospheric Motion: A Variational Perspective

Abstract The usual geophysical approximations are reframed within a variational framework. Starting from the Lagrangian of the fully compressible Euler equations expressed in a general curvilinear coordinates system, Hamilton’s principle of least action yields Euler–Lagrange equations of motion. Instead of directly making approximations in these equations, the approach followed is that of Hamilton’s principle asymptotics; that is, all approximations are performed in the Lagrangian. Using a coordinate system where the geopotential is the third coordinate, diverse approximations are considered. The assumptions and approximations covered are 1) particular shapes of the geopotential; 2) shallowness of the atmosphere, which allows for the approximation of the relative and planetary kinetic energy; 3) small vertical velocities, implying quasi-hydrostatic systems; and 4) pseudoincompressibility, enforced by introducing a Lagangian multiplier. This variational approach greatly facilitates the derivation of the equations and systematically ensures their dynamical consistency. Indeed, the symmetry properties of the approximated Lagrangian imply the conservation of energy, potential vorticity, and momentum. Justification of the equations then relies, as usual, on a proper order-of-magnitude analysis. As an illustrative example, the asymptotic consistency of recently introduced shallow-atmosphere equations with a complete Coriolis force is discussed, suggesting additional corrections to the pressure gradient and gravity.

Crystallization in organic semiconductor thin films: A diffuse-interface approach

The crystallization of organic semiconductor thin films from an amorphous phase often results in a broad range of microstructures and molecular arrangements that in turn critically impact the electronic properties of the film. Here we present a diffuse-interface model of thin film crystallization that accounts for out-of-plane tilting of the kinetically favored crystalline orientation as well as the simultaneous appearance of multiple polymorphs. By adjusting the relative thermodynamic stability of grains oriented with the fast-growing axis either parallel or perpendicular to the substrate, crystallization can be made to occur in the form of either commonly observed spherulites or more complex morphologies such as sectors and centers. Furthermore, tuning the relative kinetic coefficients and free energies of multiple polymorphs can result in a spherulite of one crystal structure embedded within a spherulite of another crystal structure. A parametric study of the effects of anisotropy, densification, time-varying treatments, and substrate patterning reveals a wide variety of morphologies that are possible in these thin films, driven by a combination of kinetic and thermodynamics effects.

Experiments on nonlinear harmonic wave generation from colliding internal wave beams

Internal waves are abundant in both the ocean and atmosphere. Their propagation and breaking are essential to energy transfer and dissipation. However, nonlinear generation of harmonic waves due to interactions among internal waves of the same scale has not been adequately explored experimentally. When two nonresonant internal waves collide, harmonics are formed at the sum and difference of multiples of the colliding waves’ frequencies, transferring energy from the initial wave beams to the harmonics. Here we experimentally explore interactions between nonresonant internal waves of the same scale and determine the relative kinetic energy transfer to their harmonics for eight unique configurations. We compare the harmonics generated here to those determined through the analysis of Tabaei et al. (2005) [1] and Jiang and Marcus (2009) [2]. It is found that approximately 7–16% of the original relative kinetic energy of the two interacting waves is transferred to the harmonics discussed here. For these configurations this value is more dependent on the relative direction the colliding waves approach each other than on their particular frequencies.