Collision Kinetic Energy Research Articles

A quantum mechanical insight into SN2 reactions: Semiclassical initial value representation calculations of vibrational features of the Cl-⋯CH3Cl pre-reaction complex with the VENUS suite of codes.

The role of vibrational excitation of reactants in driving reactions involving polyatomic species has been often studied by means of classical or quasi-classical trajectory simulations. We propose a different approach based on investigation of vibrational features of the Cl-⋯CH3Cl pre-reaction complex for the Cl- + CH3Cl SN2 reaction. We present vibrational power spectra and frequency estimates for the title pre-reaction complex calculated at the level of classical, semiclassical, and second-order vibrational perturbation theory on a pre-existing analytical potential energy surface. The main goals of the paper are the study of anharmonic effects and understanding of vibrational couplings that permit energy transfer between the collisional kinetic energy and the internal vibrations of the reactants. We provide both classical and quantum pictures of intermode couplings and show that the SN2 mechanism is favored by the coupling of a C-Cl bend involving the Cl- projectile with the CH3 rocking motion of the target molecule. We also illustrate how the routines needed for semiclassical vibrational spectroscopy simulations can be interfaced in a user-friendly way to pre-existing molecular dynamics software. In particular, we present an implementation of semiclassical spectroscopy into the VENUS suite of codes, thus providing a useful computational tool for users who are not experts of semiclassical dynamics.

Optimized installation angle and distance of a grading channel for dried jujube fruit with a push-pull actuating mechanism

Grading dried jujube fruit would improve economic efficiency of fruit production and allow more rapid industrial development of this process in China. The common grading mechanism of dried jujube is air-blowing, which causes little mechanical damage but requires a complex mechanical structure that requires significant space. This work describes a system with a push-pull actuating mechanism that offers easy operation and a simpler structure that requires less space. However, components of this mechanism might cause mechanical damage to dried jujube. The mechanical damage to the fruit is positively correlated with the collision kinetic energy caused by movement in the grading channel. With a goal to minimize mechanical damage, this study was designed to analyze the main factors related to the collision kinetic energy of dried jujube fruit, the installation angle and distance of the grading channel. By theoretical calculation, the appropriate ranges of installation angle and distance were determined as 30–60° and 10–30 cm, respectively. After that, capturing video images at different angles and distances using high-speed camera and then analyzing these video images using computer, the experimental results were obtained and showed that the collision kinetic energy was reduced with increased installation angle, and increased with increased installation distance. Accordingly, the optimized installation angle and distance were 60° and 10 cm, respectively, and the maximum collision kinetic energy on dried jujube fruit was 0.058 J, a level unlikely to cause mechanical damage.

The impact of a vehicle braking system state on safe driving – part one

The state of a vehicle braking system is one of the key factors determining the safety of the driver, passengers and other road users. During operation of a vehicle, the elements of its braking system undergo the process of wear and they are exposed to damage. Deterioration of the braking system efficiency has a direct impact on the collision speed. Thus, diagnosing a braking system during a vehicle operation is of key importance. Therefore, the authors of this article have undertaken the task to identify the influence of the state of a braking system particular element on the collision speed and kinetic energy of the impact. The obtained results of simulation calculations have proven a significant role of a braking system diagnosing in elimination of vehicles whose braking systems do not function properly as using inefficient brakes poses a significant threat to road traffic users and vehicles.

Investigation of Trace Element Content in the Seeds, Pulp, and Peel of Mashui Oranges Using Microwave Digestion and ICP-MS Analysis.

Fresh Mashui orange samples were pretreated with microwave digestion using an HNO3-H2O2 system. The levels of Mg, K, Ca, Fe, Mn, Cu, Zn, As, Cd, and Pb in the seeds, pulp, and peel were then determined using inductively coupled plasma mass spectrometry (ICP-MS) combined with collision cell technology (CCT) and kinetic energy discrimination (KED). The standard curve coefficient of determinations of the ten tested elements were between 0.9995 and 0.9999. The instrument detection limit was between 0.112ng/L and 3.05ng/mL. The method detection limit was between 0.0281 and 763ng/g. The average recovery rate was between 85.0 and 117%. The current results showed that Mashui oranges are rich in three elements, namely Mg, K, and Ca. The concentrations of K and Ca were significantly higher than that of Mg in the peel. The content of K was the highest in the seeds. Fe, Mn, Cu, and Zn had the second highest concentrations, and Fe was the highest in the seeds, while Cu was the lowest in the peel. As, Cd, and Pb (hazardous elements) had the lowest concentrations of all the tested elements.

Numerical Validation of the Combined Extrusion-Splitting Process of Energy Absorption Through Experimental Study

This paper describes the validation process of numerical model of combined collision kinetic energy absorber of rail vehicles based on results of experimental investigations. Combined absorber works on the principle of extrusion-splitting the seamless tube. With the aim to choose the most appropriate tube geometry, the tubes of different geometry of cross-section were made and tested. Key geometry parts have the shape and length of the grooves along the inner tube wall. During the second phase of deformation comes to controlled splitting of the tube wall along these grooves. Experimental and numerical investigations were realised on the scaled samples. Using this type of absorber, energy absorption occurs by friction between absorption elements and elastic-plastic deformation of the tube. Combining the two deformation processes gives a higher absorption power as well as compact dimensions of absorber which can be installed in a very limited space in the front part of the vehicle structure. Creation of the numerical model and numerical simulations of extrusion-splitting processes were realised using SolidWorks and ANSYS LS-Dyna software packages. Results of experimental investigations and numerical simulations show very good agreement which verifies developed numerical model for use in further investigations in this field.

Ice Multiplication by Breakup in Ice–Ice Collisions. Part I: Theoretical Formulation

Abstract For decades, enhancement of ice concentrations above those of active ice nucleus aerosols was observed in deep clouds with tops too warm for homogeneous freezing, indicating fragmentation of ice (multiplication). Several possible mechanisms of fragmentation have been suggested from laboratory studies, and one of these involves fragmentation in ice–ice collisions. In this two-part paper, the role of breakup in ice–ice collisions in a convective storm consisting of many cloud types is assessed with a modeling approach. The colliding ice particles can belong to any microphysical species, such as crystals, snow, graupel, hail, or freezing drops. In the present study (Part I), a full physical formulation of initiation of cloud ice by mechanical breakup in collisions involving snow, graupel, and/or hail is developed based on an energy conservation principle. Theoretically uncertain parameters are estimated by simulating laboratory and field experiments already published in the literature. Here, collision kinetic energy (CKE) is the fundamental governing variable of fragmentation in any collision, because it measures the energy available for breakage by work done to create the new surface of fragments. The developed formulation is general in the sense that it includes all the types of fragmentation observed in previous published studies and encompasses collisions of either snow or crystals with graupel/hail, collisions among only graupel/hail, and collisions among only snow/crystals. It explains the observed dependencies on CKE, size, temperature, and degree of prior riming.

Crushing analysis and multiobjective crashworthiness optimization of bitubular polygonal tubes with internal walls

In order to reduce casualties and property losses in a collision accident, thin-walled structure has been extensively used as energy absorber in crashworthiness design of train. With the help of energy absorber, collision kinetic energy can be controllably dissipated by the plastic deformation of structures. A new kind of multi-cell thin-walled structure called as bitubular polygonal tubes with internal walls (BPTIW) was constructed. The crashworthiness characteristics of BPTIWs were investigated by LS-DYNA. It can be found that the BPTIW with 12 sides has the most excellent crashworthiness characteristics. Therefore, based on response surface method (RSM) and multiobjective particle optimization (MOPSO) algorithm, the BPTIW with 12 sides was selected to optimize the dimensions of cross-sectional configuration under different constraints of energy absorption (EA) and crushing peak force (CPF). The results show that the optimal designs of BPTIW12 under different constraints present excellent crashworthiness characteristics and can be used in the practical engineering.

DESIGN PARAMETERS OF BUFFER STOPS

Paper discuses reasons of building buffer stops and situations that may occur in railway station leading to build safety tracks. Also discusses parameters of buffer stops that enter its design, such as collision speed and kinetic energy absorbing capacity. Furthermore, presents categories of<br />buffer stops depending on principles of absorbing the kinetic energy and points pros and cons of each structure.

A Parameterization of Sticking Efficiency for Collisions of Snow and Graupel with Ice Crystals: Theory and Comparison with Observations*

Abstract A new parameterization of sticking efficiency for aggregation of ice crystals onto snow and graupel is presented. This parameter plays a crucial role for the formation of ice precipitation and for electrification processes. The parameterization is intended to be used in atmospheric models simulating the aggregation of ice particles in glaciated clouds. It should improve the ability to forecast snow. Based on experimental results and general considerations of collision processes, dependencies of the sticking efficiency on temperature, surface area, and collision kinetic energy of impacting particles are derived. The parameters have been estimated from some laboratory observations by simulating the experiments and minimizing the squares of the errors of the prediction of observed quantities. The predictions from the new scheme are compared with other available laboratory and field observations. The comparisons show that the parameterization is able to reproduce the thermal behavior of sticking efficiency, observed in published laboratory studies, with a peak around −15°C corresponding to dendritic vapor growth of ice. Finally, a new theory of sticking efficiency is proposed. It explains the empirically derived parameterization in terms of a probability distribution of the work that would be required to separate two contacting particles colliding in all possible ways among many otherwise identical collisions of the same pair with a given initial collision kinetic energy. For each collision, if this work done would exceed the initial collision kinetic energy, then there is no separation after impact. The probability of that occurring equals the sticking efficiency.

Design and optimization of a new composite bumper beam in high-speed frontal crashes

Normally, automobile bumper system absorbs the collision kinetic energy by deflection in low-speed crash and by deformation in high-speed crash. The main component of this system is the bumper beam, generally made of steel. The purpose of this paper is to improve energy absorption and light the weight of bumper by applying Fruit Fly Optimization Algorithm (FOA) in frontal bumper beam. The simulation of the frontal crash by using the Finite Element (FE) model is based on the New Car Assessment Program (NCAP). The most important parameters including the type of materials, thicknesses and layup of composite layers are studied by Rescaled Range Analysis (RRA). Then, the diminution of the value of Head Injury Criterion (HIC) is treated as optimization objective in the simulation of FE model, the thicknesses of composite beam are designed and analyzed through Fruit Fly Optimization Algorithm (FOA). In addition, the optimization results are compared with the results analyzed by Genetic Algorithm (GA). It can be observed from the results that the value of HIC is reduced by 6.37 %, the new composite beam will be just 4.84 % lighter than the steel part, and its peak value of collision energy absorption is 1.36 times larger than that of the steel part. In conclusion, the FOA can be applied in design of the new composite bumper beam in improving energy absorption and lightweight.

Experimental investigation of the aggregation‐disaggregation of colliding volcanic ash particles in turbulent, low‐humidity suspensions

AbstractWe present the results of laboratory experiments on the aggregation and disaggregation of colliding volcanic ash particles. Ash particles of different composition and size <90 µm were held in turbulent suspension and filmed in high speed while colliding, aggregating, and disaggregating, forming a growing layer of electrostatically bound particles along a vertical plate. At room conditions and regardless of composition, 60–80% of the colliding particles smaller than 32 µm remained aggregated. In contrast, aggregation of particles larger than 63 µm was negligible, and, when a layer formed, periods when disaggregation (mainly by collisions or drag) exceeded aggregation occurred twice as frequently than for smaller particles. An empirical relationship linking the aggregation index, i.e., the effective fraction of aggregated particles surviving disaggregation, to the mean particle collision kinetic energy is provided. Our results have potential implications on the dynamics of volcanic plumes and ash mobility in the environment.

Experimental investigations of the shrinking–splitting tube collision energy absorber

This paper researches a type of absorber of kinetic collision energy that works on the principle of shrinking and splitting a tube of circular cross section. During collision, a seamless tube is thrust through a cone bush, squeezing the tube. Energy is absorbed by the plastic deformation, and through the friction between the tube and the bush. After passing through the cone bush, the tube presses against a splitter, and further energy is lost to friction and plastic deformation during the splitting process. Grooves on the inner wall of the tube prevent uncontrolled longitudinal tearing of the wall during the splitting. This new combined method of energy absorption enables greater absorption power with compact dimensions. Scaled samples have been tested in the laboratory. The influence of geometry and manufacturing technology of the samples, as well as the benefits of using such an absorber, are presented and discussed in this paper. The results show that the combined absorber has approximately 60% higher absorption power than the shrinking absorber by itself.

Effects of kinetic energy and collision gas on measurement of cross sections by Fourier transform ion cyclotron resonance mass spectrometry

Cross sections for removal of ions, under pressure-limited conditions, from the coherently orbiting ion packet in a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer can be measured by analysis of the FTICR line width as a function of collision gas pressure. We show that the FTICR pressure-limited line width is proportional to the square root of the collision kinetic energy (i.e., directly proportional to the ion velocity) in the center-of-mass reference frame. Cross sections increase with kinetic energy until they approach a high-energy limit, suggesting that collision-induced dissociation contributes significantly to ion dephasing. As the collision gas is varied, the cross sections are inversely proportional to the reduced mass of the collision system, and are also weakly sensitive to the physical size of the neutral collision gas. We show that N2, Ar, and SF6 are all suitable collision gases for these experiments. Analytical discrimination (the ability to detect small differences in cross sections) is greatest for the lighter collision gases, but the ease of reaching high kinetic energies in the center-of-mass reference frame increases with collision gas mass. Under the conditions of our instrument and experiments, Ar is the preferred collision gas.

Platinum in PM2.5 of the metropolitan area of Mexico City.

The increase in platinum (Pt) in the airborne particulate matter with size ≤2.5µm (PM2.5) in urban environments may be interpreted as result of the abrasion and deterioration of automobile catalyst. Nowadays, about four million vehicles in Mexico City use catalytic converters, which means that their impact should be considered. In order to evaluate the contribution of Pt to environmental pollution of the metropolitan area of Mexico City (MAMC), airborne PM2.5 was collected at five different sites in the urban area (NW, NE, C, SW, SE) in 2011 during April (dry-warm season), August (rainy season) and December (dry-cold season). Analytical determinations were carried out using a ICP-MS with a collision cell and kinetic energy discrimination. The analytical and instrument performance was evaluated with standard road dust reference material (BCR-723). Median Pt concentration in the analyzed particulate was is 38.4pgm(-3) (minimal value 1pgm(-3) maximal value 79pgm(-3)). Obtained Pt concentrations are higher than those reported for other urban areas. Spatial variation shows that SW had Pt concentration significantly higher than NW and C only. Seasonal variation shows that Pt median was higher in rainy season than in both dry seasons. A comparison of these results with previously reported data of PM10 from 1991 and 2003 in the same studied area shows a worrying increase in the concentration of Pt in the air environment of MAMC.

Use of Structural Equation Modeling to Measure Severity of Single-Vehicle Crashes

Injury severity and vehicle damage are two of the main indicators of the level of crash severity. Other factors, such as driver characteristics, roadway conditions, highway geometry, environmental factors, vehicle type, and roadside objects, may also be directly or indirectly related to crash severity. All these factors interact in such complicated ways that it is often difficult to identify their interrelationships. The aim of this study was to examine the relationships between these contributors and the severity of single-vehicle crashes. Structural equation modeling (SEM) offers the opportunity to explore the complex relationships between variables by handling endogenous variables and exogenous variables simultaneously. Furthermore, SEM allows latent variables to be included in the model and bridges the gap between dependent and explanatory variables. In this study, the number of latent variables was defined by the understanding of collision force, kinetic energy, and mechanical process of a collision, as well as statistical goodness of fit that was based on available data. Three SEM models (one with one latent variable, one with two, and one with three) representing the hypothesized relationships between collision force, speed of a vehicle, and severity of a crash were developed and evaluated in an attempt to unravel the relationships between exogenous factors and severity of single-vehicle crashes. On the basis of goodness of fit and model predictive power, the model with two latent variables outperformed the other two. Additional insights about model selection were provided through the development and comparison of the three models.

Electronic processes in adatom dynamics at epitaxial semiconductor surfaces studied using MBE-STM combined system

Thermal desorption flux of cation adatoms is modeled in the context of the transition state theory. The model, on the basis of thermally excited electron tunneling to surface adatoms, suggests that the rate of phonon-stimulated electronic transition (In+ + e− → In0) by tunneling is essential to explain the desorption flux at the InAs surface. The adatom thermal desorption is electronic in nature. The importance of an electronic process as one of elemental dynamics of epitaxy, as well as collisional kinetic energy transfer among heavy nuclei of atoms and surface, is emphasized. By means of verifying the equivalence of electrons and phonons as excitation sources in the case of the electronic transition, usefulness of low-temperature scanning tunneling microscopy (LT-STM) as a tool for studying the crystal growth mechanism is explained. A molecular beam epitaxy (MBE) system equipped with the LT-STM provides a promising complement to in situ STM observation during MBE.

Metal-armouring for shock protection of MEMS

This paper demonstrates a novel concept for the shock protection of MEMS suspensions: solder is incorporated within the sidewalls of the suspension to produce protective metal armouring. This provides solder–solder contact at the extremes of the suspension travel, greatly increasing the shock resistance. Model suspension systems were fabricated using deep reactive ion etching (DRIE) and shock tested in a drop-test rig at acceleration levels up to 6000×g. The solder armour proved to absorb ∼90% of the collision kinetic energy and double the shock resistance of the MEMS suspension.

Effects of momentum transfer on particle dispersions of dense gas–particle two-phase turbulent flows

A modified momentum transfer coefficient of dense gas–particle two-phase turbulent flows is developed and its effect on particle dispersion characteristics in high particle concentration turbulent downer flows has been numerically simulated incorporating into a second-order moment (USM) two-phase turbulent model and the kinetic theory of granular flow (KTGF) to consider particle–particle collisions. The particle fractions, the time-averaged axial particle velocity, the particle velocities fluctuation, and their correlations between gas and particle phases based on the anisotropic behaviors and the particle collision frequency are obtained and compared using traditional momentum transfer coefficients proposed by Wen (1966), Difelice (1985), Lu (2003) and Beetstra (2007). Predicted results of presented model are in good agreement with experimental measurement by Wang et al. (1992). The particle fluctuation velocity and its fluctuation velocity correlations along axial–axial and radial–radial directions have stronger anisotropic behaviors. Furthermore, the presented model is in a better accordance with Lu’s model in light of particle axial velocity fluctuation, particle temperature, particle kinetic energy and correlations of particle–gas axial–axial velocity fluctuation. Also, they are larger than those of other models. Beetstra’s model is not suitable for this downer simulation due to the relative lower particle volume fraction, particle collision and particle kinetic energy.

Effects of Altitude on Maximum Raindrop Size and Fall Velocity as Limited by Collisional Breakup

Abstract Coalescence and breakup of drops are recognized as the main mechanisms determining raindrop size distributions on the ground. Full knowledge of these processes is hindered by the challenging difficulties both in the laboratory and tunnel experiments and during observations in the open air. In real rain breakup is mainly due to collision between drops of different sizes (collisional breakup) and occurs when the collisional kinetic energy (CKE) is not absorbed by the colliding drops. In this work, the authors observe and measure the dependence on altitude of the occurrence of collisional breakup in real rainfall events, and then estimate the corresponding limit terminal velocities of drops and their size when breakup significantly takes place. Data from Pludix, an X-band microwave disdrometer, were collected at three locations at different elevations: collisional breakup position in the power spectrum of Pludix increases toward higher frequencies with increasing altitude. Terminal velocities and sizes of the drops at breakup were determined consequently, with drop sizes resulting in 4.55 ± 0.35, 4.02 ± 0.32, and 3.16 ± 0.3 mm for altitudes of 15, 950, and 3300 m MSL, respectively. The authors computed the CKE of the colliding drops at the breakup, finding an upper limiting value of about 1.22 × 10−5 J for all three altitudes. This shows that most dominant collisional breakup signature occurs at similar CKE values for all three locations, corresponding to different drop diameters at different altitudes because of the effect of air density on the drop terminal velocity.

Influence assessment of the passive restraint system devices of the passenger locomotive on its dynamic loading during accidenton the railroad

The purpose. To evaluate the work of passenger locomotive protective devices in the test scenarios of collisions adopted in the Russian requirements to the passive safety system. Methodology. Minimization of the effects of incident collisions is done by inclusion of the passive safety devices designed to absorb the kinetic energy of collision in the car bodies bearing constructions. To estimate the maximum accelerations of the train, as well as the compressing longitudinal forces arising in the intercar connection during collisions the discrete mass model of the train is used. Interaction of the train cars was simulated by introducing intercar connections. Findings. At collision of a locomotive at 20 km/h speed (both in separate and in standard train), which does not have a passive safety system, with a vehicle of 10 tones weight the plastic deformations in the locomotive structural elements are observed. At collision of a locomotive with a vehicle, which a mass is comparable to the mass of the loaded car, the plastic deformations in the locomotive structural elements occur at the 10 km/h speed of collision. Originality. It is shown that to decrease the maximum longitudinal force occurring between the locomotive and an obstacle like a freight car of 80 tons mass to the standard value it is necessary to equip the end parts of locomotive with safety devices, which deformation is about 1.5 m. Practical value. To preserve the car structures integrity and passengers, staff and locomotive brigade safety at the incident collisions, a new generation passenger locomotives have to be equipped with the passive safety system devices. On this basis, it is necessary to conduct further researches in the field of passive safety systems for carriages.