Bounce Phenomenon Research Articles

Contribution of resonance to ground bounce in lossy thin film planes

This paper discusses the pulse propagation effects on lossy thin film planes. The ground bounce phenomena produced by the resonance on planes has been captured using a combination of modeling techniques and measurements. Macromodeling method has been used to explain the transient phenomena on planes by using the dominant poles and residues of the system.

Dynamics of the Chiral-Homeotropic Liquid Crystal Displays

The dynamic response of the chiral-homeotropic liquid crystal cell has been investigated. The well-known optical bounce which was originally found in the TN cell also appears in the chiral-homeotropic cell. We have examined this bounce phenomenon both in experiments and performing computer simulations.

Microphonic and DPOAE measurements suggest a micromechanical mechanism for the ‘bounce’ phenomenon following low-frequency tones

Neural auditory thresholds in the guinea pig can be temporarily improved by up to 6 dB about 2 min after the cessation of an moderately intense low-frequency tone (Kirk and Patuzzi, 1997). We have measured changes in the f 2-f 1 distortion product otoacoustic emission (DPOAE) and low-frequency microphonic potential in scala tympani before, during and after a low-frequency tone (200 Hz) to determine the cause of this so-called bounce phenomenon. In particular we have analysed the low-frequency microphonic waveform in detail to estimate changes in the maximal receptor current through the outer hair cells (OHCs), the sensitivity of the OHC forward transduction process and the change in OHC operating point on the mechano-electrical transduction transfer curve. Our results indicate that a 200 Hz tone changes the maximal current and sensitivity of the OHCs minimally, but more importantly, it transiently changes the operating point on the OHC transfer curve. In particular, the operating point changes are consistent with a movement of the OHC stereocilia away from the OHC basal body at the peak of the bounce. These changes detected using the microphonic potential are associated with changes in the level of the f 2-f 1 DPOAE that correlate well with the electrical measurements. We suggest that the shift in operating point is largely responsible for the increase in cochlear sensitivity, and is due to a disruption of the salt balance within the cochlea during the intense low-frequency tone.

Spherical collapse of a nonrotating perfect fluid in the non-symmetric theory of gravitation

A set of time-dependent differential equations governing the behaviour of a spherically symmetric non-rotating perfect fluid in the non-symmetric theory of gravitation (NGT), is derived in a form suitable for numerical computations. This is then applied to the pressureless collapse of such a fluid. If the Newtonian potential does not exceed a certain value, and if the NGT potential is large enough, the collapse stops and reverses itself into an expansion before the Schwarzschild horizon is reached. A solution is presented for the case where the attractive tensor component of the NGT force is negligible. Bounds are found on the Newtonian potential and the ratio of NGT to Newtonian potentials within which the bounce phenomenon must occur.

Finite-cladding fibres: HE12 and local-normal-mode coupling evolution

A discussion of the evolution of the HE12 (LP02) field, and thus the rôle of the core in HE11-H12 (LP01-LP02) local-mode coupling for a tapered ‘doubly-clad’ lightguide as may be formed by the combination finite-cladding fibre and external medium (i.e. outer cladding) is presented. Consideration of more than one interface injects interesting novel features into the local-normal-mode viewpoint: examination of the HE12 lobe maximum and field evolution leads to the discovery of a core/cladding bounce phenomenon (related to an HE12 leaky-mode property) as well as an intriguing coupling phase dependence.

Bouncing mechanism of two identical liquid fuel droplets upon head-on collision.

A physical model is developed to describe the phenomenon of bouncing which was observed in our previous two-body collision experiment for hydrocarbon liquid droplets. The repulsive forces acting between the colliding droplets are caused by the intervening air flow, which is analyzed on the basis of the lubrication theory taking into account the deformation of the droplets. The droplet bouncing takes place for a restricted range of the collision Weber number which depends on the droplet size and rheological properties. Its bounderies are identified in terms of the underlying elementary physics. In particular, the upper limit is proportional to the liquid viscosity, while the lower has little dependence, consistent with the experimental result.

Collection, Bouncing, and Adhesion on Crossed Fibers in Mono- and Multilayer Design

The author studies the theoretical simulation of filtration by fabrics with special attention to the bouncing phenomena of particles on fibers. The differences in efficiency between single- and crossed-fiber flow fields are detailed; from these the computation of fiber junction helps to predict the efficiency of filters with respect to particle bouncing and leads to an advance over calculations based on a single-fiber model.

Analysis of a high speed driven valve system of internal combustion engines with consideration of the design of valve-springs. 1st Report. Dynamic rehavior of a driven valve train.

This paper presents a method for solving the dynamic response problems of a driven valve system of internal combustion engines. In this system there is a hysteresis behavior between the restoring force and the deflection for the locker arm. To treat this nonlinearity, the rigidity of each section is assumed to be the one of a partly linear spring. For the valve trains, the cam profile is complex in general. For treating a general cam profile, this paper applies a combination method of the Fourier expansion and the Laplace transform methods given by the author. Numerical calculations have been carried out for a sample problem of high speed driven valve trains, and the jump and the bounce phenomena are discussed in detail.

Innovative aerosol sampling devices based upon PIXE capabilities

Within the past few years, the critical roles of particle size and chemistry have been recognized in areas of atmospheric physics and chemistry. Earlier hopes that one or the other would suffice for an adequate characterization of aerosols have faded under the stress of new data, and extensive efforts have now been devoted to obtaining such information. The physics of the particle sizing process, however, has placed severe constraints on the amount of mass that can be collected for the subsequent chemical or elemental analyses. Generally, only a few monolayers of particles can be collected, limited either by particle bounce phenomena in inertial impactors or by clogging in filters. Such small amounts of mass are ideal for PIXE. In addition, the variability of meteorological parameters demands many such analyses for an adequate understanding of atmospheric processes, and thus the ability of PIXE systems to automate reduces costs to manageable proportions. Once PIXE has a role to play in such analyses, devices can be designed to take advantage of the small analysis areas of ion beams, and new classes of light, cheap, and accurate particle sizing devices have appeared. The nature of the match between PIXE and these devices will be considered for the Florida State streaker, the Batelle impactor, the Lundgren impactor, and the Davis Stacked Filter Units, with discussion of efforts to make such devices independent of traditional power sources.

Neutral Atmospheric Effects on the Dissipation of Aircraft Vortex Wakes

Enhanced dispersion of two-dimensional trailed vortex pairs within simplified neutral atmospheric backgrounds is studied numerically for three conditions: when the pair is imbedded in a constant turbulent bath (constant dissipation); when the pair is subjected to a mean crosswind shear; and when the pair is near the ground. Turbulent transport is modeled using second-order closure turbulent transport theory. The computed results allow several general conclusions to be drawn with regard to the reduction in circulation of the vortex pair and the rolling moment induced on a following aircraft: 1) the rate of decay of a vortex pair increases with increasing background dissipation rate; 2) crosswind shear disperses the vortex whose vorticity is opposite to the background; and 3) the proximity of a ground plane reduces the hazard of the pair by scrubbing. The phenomenon of vortex bounce is explained in terms of secondary vorticity produced at the ground plane. Qualitative comparisons are made with available experimental data, and inferences of these results upon the persistence of aircraft trailing vortices are discussed.

MONTE CARLO SIMULATION OF HORIZONTAL PNEUMATIC CONVEYING BASED ON THE ROUGH WALL MODEL

On the basis of wall roughness, a simple model is presented to explain the irregular bouncing phenomena of particles in pneumatic conveying. By introducing a random factor to the model, a pneumatic transport process was simulated by Monte Carlo method. The model could fairly well account for the concentration and velocity distribution and the rate of revolution of particles. Even very small degree of roughness was found to have a great influence upon the behaviour of particles.

ON THE MECHANISM OF SUSPENSION OF PARTICLES IN HORIZONTAL PNEUMATIC CONVEYING: MONTE CARLO SIMULATION BASED ON THE IRREGULAR BOUNCING MODEL

The mechanism of suspension of particles in horizontal pneumatic conveying was studied by experimental and numerical analyses. It was found from experiment that the particles flowing in the duct were rotating at high speeds such as 1, 000 r. p. s. or more. A model based on the ellipsoid approximation of the particle shape was constructed and was applied to account for the irregular bouncing phenomena of nonspherical particles. Moreover, the real pneumatic transport process was simulated satisfactorily by introducing a random factor into the ellipsoid model.

A Study of the Contact Bounce Phenomenon

A combination of energy and force concepts are applied to a study of several aspects of the contact bounce phenomenon. Energy dissipation at the contact interface is studied by quasistatic and dynamic techniques. Both work hardening and deformation result in a progressive reduction in the energy dissipating properties of common contact metals. The significant effect of the support structure upon bounce is analyzed by means of simple models leading to criteria for the minimization of contact bounce duration.

Two Methods of Measuring Recovery following Short-Duration Fatigue

Recovery to a tone one-half-octave above a 4000-cps, 3-min, 90-dB SL, fatiguing exposure was measured by the methods of continuous-tone Békésy audiometry and determinations of threshold following periods of silence. Such a high-level exposure results in a two-part recovery function. The first is a rapid recovery occurring in the 1st min, and the second is a slower gradual recovery occurring after the 1st min. These types of recovery have been labeled R-1 and R-2, respectively, by Hirsh and Bilger. The study was divided into four experiments. Experiment 1 revealed a difference at the end of 6 min between the two methods on the order of 7 dB in favor of the method of periodic determinations of threshold as the more accurate descriptive measure. The subsequent experiments attempted to determine if this difference occurred primarily in R-1 or R-2. The results were confusing and contradictory. The immediate introduction of silence rather than continuous tone trace resulted in faster recovery. However, of the periods of silence studied in R-1—20, 40, and 60 sec—the longest period resulted in the slowest recovery. Ignoring R-1 recovery, silent periods resulted in faster recovery than continuous tone trace in R-2 recovery, but the design was unable to detect any critical differences in the length of silent periods used. The results of these experiments may have been confounded by the finding that repeated exposures to the fatiguing stimulus, while not seeming to effect the pre-exposure threshold, do modify the pattern of recovery in the direction of no change in the fatigued threshold after the 1st to 6th min of recovery. After repeated exposures, the sensitivity of the ear following high-level exposure is changed. Other relevant findings are discussed, such as the bounce phenomenon and the index of fatigued threshold.

Mechanics of particle bounce

AbstractIrregular particles bounce with randomly distributed angles of reflection. There is a certain probability that a particle striking at low angle will bounce at a high angle and be carried far out into the main fluid flow. Bounce phenomena were investigated with respect to bounce of a model particle, limitations on dust collection (back mixing), and energy loss during the flow of suspensions.