Instantaneous Propagation Research Articles

Direct penetration of the polar electric field to the equator during a DP 2 event as detected by the auroral and equatorial magnetometer chains and the EISCAT radar

The quasi‐periodic DP 2 magnetic fluctuations (period of 30–40 min) appearing coherently at the auroral and equatorial latitudes during the day are analyzed based on the high time resolution magnetometer data recorded at the International Monitor for Auroral Geomagnetic Effects (IMAGE) stations in Scandinavia and at the Brazilian and African equatorial stations. It is shown that the correlation between the DP 2 magnetic fluctuations at both latitudes is excellent (correlation coefficient of 0.9). No discernible time shift has been found within the resolution of 25 s. The European incoherent scatter (EISCAT) radar observations in Scandinavia show that the DP 2 fluctuations at auroral latitudes are caused by an ionospheric Hall current which is controled by the convection electric field. The DP 2 fluctuations exhibit a strong decrease in magnitude with decreasing latitude, however, it is enhanced considerably at the dip equator with an amplitude comparable to that at the subauroral latitude. The considerable equatorial enhancement of the magnitude of the DP 2 fluctuations with an enhancement ratio of 4 is due to the concentration of the electric current along the highly conductive dayside equatorial ionosphere. These observational facts can be explained in terms of an ionospheric current which is generated by the magnetospheric electric field at the high latitude and extends to the equatorial ionosphere almost instantaneously. From the viewpoint of the electric field penetration, we conclude that the magnetospheric electric field penetrates to the equatorial ionosphere through the polar ionosphere almost instantaneously within the time resolution of 25 s. The nearly instantaneous propagation of the electric field to the equator can be explained primarily by a parallel plane transmission line model composed of the conductive Earth and ionosphere. In addition to our finding of the fast propagation of the DP 2 electric field, it is found that an impulsive magnetic change with a timescale of 100 s appears at the dayside dip equator with a time delay of about 10 s, which requires to include the effect of the high conductivity of the dayside equatorial ionosphere in future studies of the propagation model.

(2+1)-Gravity with moving particles in an instantaneous gauge

By defining a regular gauge which is conformal-like and provides instantaneous field propagation, we investigate classical solutions of (2+1)-Gravity coupled to arbitrarily moving point-like particles. We show how to separate field equations from self-consistent motion and we provide a solution for the metric and the motion in the two-body case with arbitrary speed, up to second order in the mass parameters.

Effect of nonunity lewis number on premixed flame propagation through isotropic turbulence

Direct numerical simulations of a passive premixed flame surface propagating through stationary isotropic turbulence have been performed in three dimensions on a 96 3 mesh with a particular emphasis on characterizing the effect of Lewis number on the rate of propagation of the flame surface and flame surface topology. The simulations were based on the flame sheet assumption that implies that the time scale for chemical reaction is short as compared with the time scales for the turbulent fluctuations (so-called flamelet regime). In this limit, the flame surface can be represented by a field equation (Sivashinsky equation) which accounts for local advection of the reaction front due to instantaneous velocity fluctuations and propagation due to reaction. The Navier Stokes equations and scalar field equation for the flame surface were updated using a pseudo-spectral method with fourth order accuracy in time. Lewis number effects were incorporated into the simulations by using a modified Sivashinsky equation for the flame surface. At zero turbulence level, the simulation yielded the familiar steady and nonsteady cellular structures seen previously by several investigators. At finite turbulence levels the flame speed was augmented above the cellular flame speed due to additional wrinkling from the hydrodynamic field. Comparisons with experimental measurements in the literature agree with the simulations to within 30% over a wide range of turbulence intensities and Lewis numbers. In addition spectral analysis of the Sivashinsky equation provides insight into the effect of varying the Lewis number and how that effect may be incorporated into a relatively simple spectral model for the flame surface.

The evolution of unstable regions in impulsively started pipe entrance flows

A unified stability curve was generated for impulsively started pipe entrance flows, comprising the variation of critical Reynolds number with a novel dimensionless velocity profile shape parameter. Time dependent regions of stability and instability were obtained, explaining qualitatively the measured almost instantaneous upstream propagation of turbulence in a starting pipe flow. In so doing they provide a formal alternative to the widely held view that the observation of turbulence far downstream under steady-state conditions is purely from the evolution and washdown of turbulent structures in the unstable entrance region of the pipe, suggesting the possibility that local downstream instabilities and turbulence from an earlier time, play a role.

Absolute continuity results for superprocesses with some applications

Let ${X^1}$ and ${X^2}$ be instances of a measure-valued Dawson-Watanabe $\xi$-super process where the underlying spatial motions are given by a Borel right process, $\xi$, and where the branching mechanism has finite variance. A necessary and sufficient condition on $X_0^1$ and $X_0^2$ is found for the law of $X_s^1$ to be absolutely continuous with respect to the law of $X_t^2$. The conditions are the natural absolute continuity conditions on $\xi$, but some care must be taken with the set of times $s$, $t$ being considered. The result is used to study the closed support of super-Brownian motion and give sufficient conditions for the existence of a nontrivial "collision measure" for a pair of independent super-Lévy processes or, more generally, for a super-Lévy process and a fixed measure. The collision measure gauges the extent of overlap of the two measures. As a final application, we give an elementary proof of the instantaneous propagation of a super-Lévy process to all points to which the underlying Lévy process can jump. This result is then extended to a much larger class of superprocesses using different techniques.

The performance of available copy protocols for the management of replicated data

Available copy protocols guarantee the consistency of replicated data objects against any combination of non-Byzantine failures that do not result in partial communication failures. While the original available copy protocol assumed instantaneous detection of failures and instantaneous propagation of this information, more realistic protocols that do not rely on these assumptions have been devised. Two such protocols are investigated in this paper: a naive available copy (NAC) protocol that does not maintain any state information, and an optimistic available copy (OAC) protocol that only maintains state information at write and recovery times. Markov models are used to compare the performance of these two protocols with that of the original available copy protocol. These protocols are shown to perform nearly as well as the original available copy protocol, which is shown to perform much better than quorum consensus protocols.

銅とダイヤモンドの原子配列モデルによる計算機内での切削実験

A method of atomic scale cutting in a computer has been developed based on the nonlinear finite element formulation which regards atoms and atomic interaction as nodes and elements, respectively. This method can handle discontinuous phenomena due to instantaneous propagation of dislocation in a workpiece during cutting. Experiments carried out using two kinds of assumed interactive potential energy between tool and workpiece atoms have revealed that the process of chip formation as well as the stress distribution on the tool face during cutting is strongly dependent on the type of interaction energy between the tool and workpiece, while the size effect for the specific cutting coefficient and the discontinuity of cutting force variation during cutting are common in both types of potential energy. The experiments have also shown that the intermittent drop of the potential energy accumulated in the workpiece during cutting is the result of heat generation associated with plastic deformation of the workpiece, while the heat generation causes impulsive temperature rise on the tool face repeatedly during cutting.

Effect of electrical stimulus parameters on the development and propagation of action potentials in short excitable fibres

Intracellular action potentials (IAPs) produced by short fibres in response to their electrical stimulation were analysed. IAPs were calculated on the basis of the Hodgkin-Huxley (1952) model by the method described by Joyner et al. (1978). Principal differences were found in processes of activation of short (semilength L < 5 λ) and long fibres under near-threshold stimulation. The shorter the fibre, the lower was the threshold value (I thr). Dependence of the latency on the stimulus strenght (I st) was substantially non-linear and was affected by the fibre length. Both fibre length and stimulus strength influenced the IAP amplitude, the instantaneous propagation velocity (IPV) and the site of the first origin of the IAP (and, consequently, excitability of the short fibre membrane). With L ⩽ 2 λ and I thr ⩽ I st ⩽ 1·1I thr, IPV could reach either very high values (so that all the fibre membrane fired practically simultaneously) or even negative values. The latter corresponded to the first origin of the propagated IAP, not at the site of stimulation but at the fibre termination or at a midpoint. The characters of all the above dependencies were unchanged irrespective of the manner of approaching threshold (variation of stimulus duration or its strength). Reasons for differences in processes of activation of short and long fibres are discussed in terms of electrical load and latency. Applications of the results to explain an increased jitter, velocity recovery function and velocity-diameter relationship are also discussed.

On a new functional form for the dispersive flux in porous media

A recently developed second‐order model for local dispersive transport in porous media has been simplified to yield a new, closed‐form relationship for the dispersive flux. In situations characterized by negligible velocity gradients, the flux can generally be represented as a convolution or “memory” integral over time of previous concentration gradients. The strength of this memory is controlled by an exponential weighting factor related to the magnitudes of the velocity and local molecular diffusive flux. The form of this result is consistent with other models of diffusive and dispersive transport phenomena over various spatial scales. In circumstances where the memory strength is small, the integral can be simplified and cast in the form of a standard Fickian relationship with apparent time‐dependent dispersivity functions that grow to finite, asymptotic values. This specific formulation can be manipulated to yield a one‐equation transport balance law in the form of a telegraph equation. Nonphysical effects, such as spurious upstream dispersion and instantaneous propagation of mass to extremely distant points predicted with a Fickian law, are reduced or eliminated. Although the importance of the new result in transport simulations will depend on the spatial and temporal scales of interest, it should provide some insight in the interpretation and design of new experiments.

Diffusion in Fissured Media

The nonlinear initial-boundary value problem \[\begin{gathered} \frac{{\partial u}}{{\partial t}} + \frac{1}{\varepsilon }(\alpha (u) - v) = f_1 ,\quad - {\operatorname{div}}\,(k{\operatorname{grad}}\,v) + \frac{1}{\varepsilon }(v - \alpha (u)) = f_2 \quad {\text{in }}G \times (0,T), \hfill u(x,0) = u_0 (x)\quad {\text{in }}G,\quad v(s,t) = 0\quad {\text{on }}\partial G \times (0,T) \hfill \end{gathered} \] is a well-posed model of diffusion in a fissured porous medium. Special features of the solution include the perseverance of local spatial continuity or singularities in the concentration u, the instantaneous propagation of the partially-saturated region throughout G, the delayed and limited advance of the fully-saturated region into G, and the concentration discontinuity on the boundary of the fully-saturated region. Weak maximum and order-comparison principles are obtained as $L^\infty $ and $L^1 $ estimates on a solution and a difference of solutions, respectively.

Image transmission through a turbulent medium using a point reflector and four-wave mixing in BSO crystal

A method of one-way image transmission through a turbulent medium is presented using four-wave mixing in BSO crystal. In this method, a pointlike reflector is placed on the observation plane to return part of the incident wave, giving the instantaneous wave propagation function of the turbulent medium to the image transmission side. The returned wave together with the plane reference wave and the Fourier-transformed input image wave is impinged in BSO crystal to modulate the image wave by the phase-conjugate wave, so that transmission of the image with reduced turbulence effects is achieved. The principle and laboratory experimental results are given.

Explanatory axiomatics of quantum theory: Resolution of the Einstein-Podolsky-Rosen paradox

This paper is concerned with resolving the famous Einstein-Podolsky-Rosen paradox within the scope of the explanatory axiomatics of quantum theory, developed by one of the present authors. It is shown that the possibility, arising as a result of the analysis, for practically instantaneous propagation of a material perturbation over arbitrary distances is so specific that it cannot serve as a means for transmitting information at velocities higher than the velocity of light. The presence of such noninformative material excitations requires reformulating the principle of microcausality. This fact makes necessary a clear distinction between the terms “preparation of material excitation” and “transmission of information.”

Inertial Effects in Transport of Radioactive Waste Through Engineered Barriers

ABSTRACTAddition of an inertial term to the constitutive relation for mass flux leads to a mass transport equation which is hyperbolic and describes propagation of a distorted wave with a finite velocity. This approach eliminates the “instantaneous propagation paradox” inherent in parabolic transport equations based on Fick's law. Analytical solutions of the wave transport equation have been derived and have the properties that the leading edge of a solute front propagates at a finite, predictable velocity and is truncated by a step function which decreases in magnitude exponentially with time. The inertial effects on computed solute fronts are most evident near the leading edge, and have potential significance in the prediction of engineered barrier performance.

Nicole Oresme on the Nature, Reflection, and Speed of Light

L ATE MEDIEVAL VISUAL THEORY presents an untidy amalgam of Aristotelian natural philosophy, geometric optics, scholastic metaphysics, and even theology. Modern scholarship has treated each of these medieval categories of thought separately, and it has therefore proved very difficult for the student of medieval visual theory to comprehend his subject fully-that is, both to analyze what the medieval authors who wrote about vision were trying to accomplish, and to discern what sources they drew upon. Keeping these difficulties in view, the present paper unravels a hitherto unexamined instance of late medieval visual theory: Nicole Oresme's discussion of light in Questiones super libros Aristotelis de anima, based on Aristotle's On the Soul. I The details of Oresme's argument on the properties of light cannot be fully elucidated without reference to Book II of De anima, in which Aristotle suggested that a medium capable of bearing light could become light-bearing instantaneously.2 This passage forms the basis for Oresme's discussion. Being a careful scholastic, however, Oresme did not simply record his agreement with Aristotle. Rather, he set out first to explain what light was and what it meant for the medium to become instantaneously light-bearing. Only then did he attempt to discuss the possible immediacy of illumination. If we treat Oresme's argument under two headings-his preliminary explanations of the nature of light and the medium, and his specific arguments about instantaneous propagation-it appears that each part has a different relation to his sources. The specific arguments about instantaneous propagation may be unique to Oresme; at least I have not uncovered any precedents for them, although many comparable late medieval texts remain unedited. His preliminary considerations, however, have definite precedents in the many diverse elements of medieval visual theory, as comparison of those ideas of Oresme's with similar arguments in earlier texts will show. Oresme's preliminary arguments are conveniently treated before his special arguments about instantaneous propagation. In considering them, it is possible to test David Lindberg's recent division of late medieval visual theory into three

Numerical simulation of triple shock behavior of gaseous detonation

A numerical analysis of performed on the nonsteady two-dimensional behavior of self-sustaining detonations. In order to produce realistic two-dimensional structures during propagation in a finite width channel, an initially assumed plane one-dimensional Chapman-Jouguet detonation was perturbed by locating up to five pairs of exothermicity spots in the passage of the detonation. The most interesting feature of the simulation was the number of triple shock waves existing after a certain time of transition from plane to periodically nonsteady two-dimensional structures. In other words, the final number of transverse shock waves becomes mostly two, which are nearly irrelevant to the assumed number of initial exothermicity spots. Details of the disappearance of several transverse waves during their rearrangement were clearly observed and are discussed. In addition, despite considerable deviation of the instantaneous propagation velocity from from the C-J value, the average of such oscillations was close to the C-J value. Thus, the results of the simulation provided the numerous features observed in the present gaseous detonations experiments. The numerical schemes utilized were the explicit first-order Van Leer and second-order MacCormack methods. The effect of artificial viscosity was examined and found to affect the transition to fully developed detonation.

Kinematics of experimentally produced deformation bands in stibnite

Using videotape techniques, we have observed the kinematic development of a variety of microstructures during experimental deformation of single crystals of stibnite (Sb 2S 3). The crystals were deformed by flexure or uniaxial compression at room P- T conditions in a small strain device attached to the stage of a reflecting microscope. In more than 50 experimental runs, the primary microstructures produced in stibnite were deformation bands, not deformation twins as often reported in the literature. Translation gliding along (010) [001] results in visible slipbands and produces two basic types of deformation bands, each with a variety of subtypes. Kink bands form with φ (angle of internal rotation) ≊70° and perpendicular bands develop with φ≊ 90°. Other optical deformation features seen forming were: breccia fragments, bent and opened cleavages, and microfolds. Four stages could be seen in the kinematic development of deformation bands. During initiation, bands form by nearly instantaneous propagation of a narrow bent zone across the crystal. During later migration, the bands widen at a rate invariably slower than the rate of initiation. Termination of bands occurs when growth is impeded by intersections with grain boundaries or other deformation features. During late modification, previously formed bands with straight boundaries are sheared, bent, and compressed. Unconfined crystals tend to form kinks, whereas the perpendicular bands formed in samples confined in relatively rigid plastic. Naturally deformed stibnites show the same features. Television photomicroscopy has great potential for studying microstructures during deformation.

On the Instantaneous Propagation Paradox of Heat Conduction

On the Instantaneous Propagation Paradox of Heat Conduction

Relativistic elasticity of dissipative media and its wave propagation modes

A phenomenological, general relativistic theory of dissipative elastic solids whose equations form a hyperbolic system is proposed. The non-stationary transport equations for dissipative fluxes containing new cross-effect terms, as required by compatibility with irreversible thermodynamics, have been adopted. As opposed to some conventional theories which are parabolic and predict instantaneous propagation of wavefronts, the theory formulated, consisting of 14 partial differential equations (in the case of special relativity), of total order 17, is hyperbolic and predicts, for all existing propagation modes, finite front speeds. The complete system of special relativistic propagation modes of an elastic solid is determined from the linearised equations. There are four mutually distinct non-trivial propagation modes, two for longitudinal waves and two for transverse waves. If the rigidity modulus decreases to zero one obtains as a special case the normal modes for fluid according to the theory of Muller (1972) and Israel (1976). Weber's equation is also briefly discussed.

Hyperbolic elasticity of dissipative media and its wave propagation modes

A phenomenological theory of dissipative elastic solids whose equations form a hyperbolic system is proposed. The Muller-Israel non-stationary transport equations for dissipative fluxes containing new cross-effect terms, as required by compatibility with irreversible thermodynamics, have been adopted. As opposed to usual conventional theories, which are parabolic and predict instantaneous propagation of wavefronts, the theory formulated, formed of 14 partial differential equations, all of 17th order, is hyperbolic and predicts, for all existing propagation modes, finite front speeds. The complete system of propagation modes is determined from the linearized equations. There are four mutually distinct non-trivial propagation modes, two for longitudinal waves and two for transverse waves.

Nonstationary irreversible thermodynamics: A causal relativistic theory

Conventional theories of irreversible thermodynamics predict instantaneous propagation of thermal and viscous effects. This defect can be traced to the omission of terms quadratic in the heat flux and viscous stresses from the expression for the entropy 4-vector in terms of the fluxes of 4-momentum and material. By a systematic restoration of the quadratic terms, a generalized theory is formulated which is applicable to the description of transient irreversible effects and reconcilable with causality. Also discussed is the relativistic formulation of the second law of thermodynamics for the exchange of heat and matter between bodies with arbitrary relative velocities.