Showing papers on "Impulse (physics) published in 1981"
TL;DR: A new analytic expression for the impulse response of concave radiators is used to compute the transient pressure distributions of phased annular arrays with spherical geometry.
166 citations
TL;DR: In this paper, a theoretical model for evaluating the transient velocity potential and pressure fields radiated by a planar piston set in an infinite rigid baffle and having an arbitrary spatial velocity distribution is presented.
Abstract: A theoretical model is presented for evaluating the transient velocity potential and pressure fields radiated by a pulsed planar piston set in an infinite rigid baffle and having an arbitrary spatial velocity distribution. The method is based on the development of a generalized spatial impulse response function which describes the velocity potential, either at a point or averaged over a finite receiving surface, resulting from the velocity impulse excitation of a uniformly or nonuniformly vibrating piston source. For the specific case of a circular source and receiver this function is plotted using several source distributions and receiver sizes. Then corresponding plots are presented for two piston velocity waveforms: a Gaussian pulse and a Gaussian‐modulated sinusoidal burst. These plots are compared and the effects of a nonuniformly vibrating source and finite receiver are discussed. Lastly, a previous solution by Schoch, in which the field of a rigid piston is separated into geometrical and boundary diffraction waves, is extended to account for a nonuniform source, and the relationship of this more general result to the present approach is illustrated.
118 citations
TL;DR: The transfer function of the system responding to a 1° stimulus shows a band-pass filter type of processing for transients, confirming quantitatively earlier findings.
109 citations
TL;DR: Changes in pulse speed and interspike interval during propagation are predicted quantitatively by a simple kinematic approximation which applies the dispersion relation, instantaneously, to individual pulses.
102 citations
Patent•
06 Nov 1981
TL;DR: In this paper, a method and devices for mixing at least two individual streams having different variables is described. But the method is not suitable for mixing a large number of individual streams.
Abstract: The present invention relates to a method and devices for mixing at least two individual streams having different variables. In order to produce a low-loss, effective mixing within a short flow section, at least one eddy impulse is produced in the cross section of flow of at least one individual stream, which impulse spreads out downstream transverse to the direction of flow to form a discrete eddy system whose components transverse to the main direction of flow overlap into the other flow cross section of the other individual stream. This eddy impulse can be produced either by at least one curved surface or by at least one edge of a surface or of a body. The eddy impulse is preferably produced by two burble (flow break-away) edges of a delta-shaped insert element which extend at an acute angle to each other.
93 citations
66 citations
TL;DR: The results showed that the taste quality was represented in the characteristic temporal patterning of impulses as well as in the across-neuron patterns of responses in the impulse trains as a stochastic point process.
Abstract: 1. The present study was intended to elucidate the role of temporal patterns of impulse discharges of the gustatory primary afferents in the coding of taste qualities by the use of simultaneous analyses of the across-neuron patterning (5) and the temporal patterning of impulses. 2. Impulse discharges of 43 rat chorda tympani fibers elicited by gustatory stimulation (0.1 M NaCl, 0.5 M sucrose, 0.01 N HCl, 0.02 M quinine hydrochloride, 0.3 M KCl, and 0.02 M saccharin sodium) were recorded. The temporal patterns of impulse discharges elicited by these stimuli were statistically analyzed both in an initial dynamic phase and a succeeding stationary phase of responses. In the dynamic phase, the time courses of firing frequency were studied; however, these were not clearly associated with the qualities of taste stimuli. In the stationary phase, the stochastic properties of impulse trains were studied regarding the impulse trains as a stochastic point process (30). In this study, interspike interval histograms (ISI histograms), joint interval histograms, serial correlograms, and autocorrelograms were computed. 3. In general, the distribution patterns of ISI histogram were not absolutely specific to the taste qualities. However, the gamma or the exponential distribution occurred most often with 0.1 M NaCl, and the bimodal or the skewed distribution was dominated with 0.5 M sucrose stimulation among the stimuli tested. The rhythmic discharges did not occur exclusively with the sweet taste stimulation, though they occurred more often with the sweet taste stimulation than with other taste stimulations. The joint interval histogram and the serial correlogram were used to examine the stochastic properties of impulse trains with particular reference to the time dependence in the impulse trains. Generally, the time dependence was not concerned with the taste qualities. 4. The chorda tympani fibers were classified into three types according to the magnitude of responses and the temporal patterns of impulse discharges. The neurons predominantly responsive to NaCl and unresponsive to sucrose were classified as type I neurons. The remaining neurons, which moderately responded to both NaCl and sucrose, were further categorized into type II neurons and type III neurons, depending on their temporal patterns of impulse discharge. The type II neurons tended to show the rhythmic or burstlike firing of impulses in response to more than one kind of taste stimuli. 5. The results showed that the taste quality was represented in the characteristic temporal patterning of impulses as well as in the across-neuron patterning of responses. The possible origin of the temporal discharge pattern and its significance in gustatory information processing were discussed on the basis of the neuron types described above.
52 citations
01 Jan 1981-Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology
TL;DR: The impulse response of the tympanal membrane was determined in six species of crickets and bushcrickets by stimulating the ear with impulse sounds and recording the resulting tyMPanal vibration with a laser vibrometer.
46 citations
TL;DR: A γ-motoneuron pathway to intrafusal muscle has been added to a previously studied model of the neuromuscular system and its reflex pathways which offers the advantage of stability at the expense of increased sluggishness of response.
Abstract: A ?-motoneuron pathway to intrafusal muscle has been added to a previously studied model of the neuromuscular system and its reflex pathways. A general differential-difference equation is derived for the system which can be solved analytically and numerically. The homogeneous part of the solution determinas the stability of the feedback pathway which to a first approximation is unchanged from the previous model. However, the additional filtering in the ?-pathway reduces the tendency for oscillations to central inputs, which is illustrated for the particular solutions to sinusoidal and impulse inputs. Thus, the gamma pathway offers the advantage of stability at the expense of increased sluggishness of response.
46 citations
TL;DR: A wave packet generated by a localized impulse can be defined in terms of an integral or sum of periodic wavetrains, which can be represented asymptotically in a number of different ways as mentioned in this paper.
Abstract: A wave packet generated by a localized impulse can be defined in terms of an integral or sum of periodic wavetrains. This integral can be represented asymptotically in a number of different ways. Wave forms of a twodimensional wave packet defined by various expansions are evaluated numerically and compared over a range of distances from their point of origin.
TL;DR: The experiments suggest that for the technique to be used in the detection of local reflecting sites such as might result from vascular occlusive disease, the lesions should occlude at least 70% of the lumen and should be no more than 0.20 m distal to the impulse generator.
Abstract: The propagation of a transient pressure impulse in a viscoelastic medium was investigated by experiments using water-filled latex rubber tubing and the aorta of anaesthetised dogs. A 5 ms pressure impulse was produced by the impact of a solenoid driven hammer. The propagation characteristics of the impulse (attenuation and propagation velocity) along the vessel were determined by means of a catheter-tip pressure manometer placed at various distances distal to the impulse generator. The presence of stenoses of varying degrees of severity resulted in reflection of the impulse and the appearance of reflected pulses whose magnitude depended on the stenotic severity. The experiments suggest that for the technique to be used in the detection of local reflecting sites such as might result from vascular occlusive disease, the lesions should occlude at least 70% of the lumen and should be no more than 0.20 m distal to the impulse generator.
TL;DR: In this paper, the authors examined the energy balance in an impact machine and derived simple and helpful expressions for the radiated sound energy in terms of the internal energy level, a modified radiation efficiency, a structural damping factor, and a bulkness factor.
TL;DR: In this article, it was shown that the density and the two Lame profiles of a layered elastic medium can be uniquely determined from the impulse responses due to obliquely incident SH plane waves at two precritical angles of incidence and a normally incident P plane wave.
Abstract: It is shown that the density and the two Lame profiles of a layered elastic medium can be uniquely determined from the impulse responses due to obliquely incident SH plane waves at two precritical angles of incidence and a normally incident P plane wave. A direct (noniterative) inversion algorithm is developed which construct the three elastic profiles of the layered medium from the reflection data. The equation of motion for an obliquely incident SH plane wave is transformed to the Schrodinger equation whose potential is related to the density profile, shear modulus profile, and the angle of incidence. The Gelfand–Levitan theory is used to recover the potential of the Schrodinger equation from the impulse response. When the impulse response is available at two angles of incidence, the shear modulus and density profiles can be separately obtained as a function of depth. It is further shown that the incompressibility profile can be obtained from the impulse response due to a normally incident P plane wave and the density and shear modulus profiles.
TL;DR: In this paper, the impulse impedance of a grounding grid is analyzed for determining its performance while discharging impulse currents to ground if problems concerning lightning protection and transients under ground faults are to be accurately analyzed.
Abstract: The impulse impedance of a grounding grid must be known for determining its performance while discharging impulse currents to ground if problems concerning lightning protection and transients under ground faults are to be accurately analysed. This paper out-lines the basic concepts required for this study, analyses the equivalent circuit ,21]of a grounding grid for its response to practical impulses like ramp (i.e. idealised lightning stroke) and double exponential wave inputs and establishes expressions for the impulse impedance. Its value is shown to be higher than the grid's power-frequency grounding resistance, decaying to this latter value with passage of time. Inductance of the grid is shown to be the governing factor contributing to its impulse impedance. Only those values of current which do not cause breakdown of the soil are considered
TL;DR: In this article, an experimental verification of the impulse response method to evaluate the transient acoustic field of pulsed ultrasonic radiators is presented, where several piezoelectric disk radiators were constructed for the experiments.
Abstract: An experimental verification of the impulse‐response method to evaluate the transient acoustic field of pulsed ultrasonic radiators is presented. Several piezoelectric disk radiators were constructed for the experiments. Transient pressure measurements were obtained at several field points for pulsed wide bandwidth electrical excitations of the radiators. The pressure data were processed via an iterative deconvolution method to obtain experimental impulse responses. The method ideally eliminates the effects of the dynamic response of the transmit and receive system on the impulse responses. A comparison of the experimental and theoretical impulse responses shows the responses to be in general agreement.
01 Oct 1981
TL;DR: In this article, the authors studied pre-discharge discharges in clean SF6 gas-insulated power transmission systems under highly non-uniform electric fields under controlled laboratory conditions.
Abstract: In clean SF6 gas-insulated power transmission systems significant pre-breakdown discharges are rarely observed. This is so because the prevailing electric field is only moderately non-uniform. In practical systems, however, conducting particle contamination creates regions of highly non-uniform fields. Initial ionization, under contaminated conditions, takes the form of pre-breakdown discharges. An understanding of pre-breakdown discharges is essential for evaluating the conducting particle effects and the insulation capability of SF6 gas-insulated systems. Rod-to-plane gaps provide a convenient way of studying pre-breakdown discharges in SF6 under highly non-uniform fields under controlled laboratory conditions. The relatively few published reports of investigations of prebreakdown discharges in SF6 are reviewed. Based on the authors' and other published experimental results, several pre-breakdown regimes (for example, single pulse and multiple pulse pre-discharges and incomplete breakdowns etc.) are identified. The randomness of the time delay of the first pre-discharge current pulse is attributed to the rate of production of initiatory electrons near the anode and the growth of electron avalanches thus generated. The importance of the spatial electric field distribution around the rod electrode (anode) is emphasized. Since in practice transient overvoltages may be superimposed on the system 60 Hz ac voltage, the effect of continuous corona and the space charge due to the 60 Hz ac voltage on the overall insulation performance of SF6 gas-insulated systems under combined ac and impulse voltages also is discussed.
DOI•
01 Nov 1981TL;DR: In this paper, the distribution of time lags to corona inception is examined theoretically and experimentally for the case where a doubleexponential positive impulse voltage waveform is applied, at a fixed repetition rate, to a rod/plane gap.
Abstract: The distribution of time lags to corona inception is examined theoretically and experimentally for the case where a double-exponential positive impulse voltage waveform is applied, at a fixed repetition rate, to a rod/plane gap. The influence of atmospheric humidity, temperature and pressure on the conditions for corona formation are discussed. Experimentally, the spread of the time-lag distribution is studied primarily as a function of humidity. The results are related to the variation, with humidity, of the negative-ion density prior to each impulse. Models for the conditions for detachment of electrons from negative ions, and for corona formation, which are derived from experiments using small air gaps, have been shown to agree with the results obtained in large air gaps.
01 Sep 1981
TL;DR: In this article, the impulsive nature of noise due to the interaction of a rotor blade with a tip vortex is studied, and the time signature of this noise is calculated theoretically based on the measured blade surface pressure fluctuation of an operational load survey rotor in slow descending flight and is compared with the simultaneous microphone measurement.
Abstract: The impulsive nature of noise due to the interaction of a rotor blade with a tip vortex is studied. The time signature of this noise is calculated theoretically based on the measured blade surface pressure fluctuation of an operational load survey rotor in slow descending flight and is compared with the simultaneous microphone measurement. Particularly, the physical understanding of the characteristic features of a waveform is extensively studied in order to understand the generating mechanism and to identify the important parameters. The interaction trajectory of a tip vortex on an acoustic planform is shown to be a very important parameter for the impulsive shape of the noise. The unsteady nature of the pressure distribution at the very leading edge is also important to the pulse shape. The theoretical model using noncompact liner acoustics predicts the general shape of interaction impulse pretty well except for peak amplitude which requires more continuous information along the span at the leading edge.
TL;DR: In this article, the responses of fluid targets are computed using space-time integral equations formulated in the time domain, where the incident pressure wave is a smoothed-impulse with a Gaussian shaped time dependence whose width is of the order of a target dimension.
Abstract: The responses of fluid targets are computed using space–time integral equations formulated in the time domain. The incident pressure wave is a ’’smoothed‐impulse’’ with a Gaussian shaped time dependence whose width is of the order of a target dimension. A space–time integral equation for the pressure field on the outside of the target surface and a space–time integral equation for the pressure field on the inside of the target surface are solved simultaneously for the pressure and the pressure gradient by stepping on in time and making use of the boundary conditions (continuity of pressure and displacement). The farfield is then computed from these source fields. The technique is applicable to targets of arbitrary contour and is demonstrated for a sphere and right circular cylinder at various angles of incidence. Fluid targets support interior compression waves; sound‐hard and sound‐soft targets are treated as limiting cases of this formulation. The technique has been verified for the case of a sphere by comparison with the response computed by classical expansions.
TL;DR: In this paper, the authors discuss the background of impulse turbine technology, its applicability to sea water R.O. energy recovery systems, and the economic benefit of energy recovery on product water price.
01 Apr 1981
TL;DR: In this article, the thrust and efficiency of a quasi-steady multi-MW argon MPD thruster with one-millisecond current pulses were determined for a benchmark thruster geometry on a swinging gate thrust stand in a dielectric vacuum tank.
Abstract: Thrust and efficiency of a quasi-steady multi-MW argon MPD thruster are determined for one-millisecond current pulses. Terminal voltage and impulse bit per pulse are measured for a benchmark thruster geometry on a swinging gate thrust stand in a dielectric vacuum tank, at a background pressure of 0.0001 torr, for a range of argon flow rates and arc currents. The quasi-steady thrust data scale quadratically with arc current, and confirm previous estimates of the electromagnetic and electrothermal components of thrust from magnetic and pressure probe measurements. Thruster efficiency is found to increase monotonically with specific impulse, reaching a value of 25% for 4.5 to 6.0 g/sec at 2000 seconds. Results of further experiments show that the inferred specific impulse for voltage fluctuation onset can be increased to 3000 seconds, and the thrust efficiency to above 30%.
TL;DR: In this paper, the impact parameter dependence of the capture of a target L-subshell electron by a light projectile is calculated within the semiclassical impulse approximation (SCIA), and the anisotropy of the resulting target 2 p vacancies is strongly dependent on impact parameter and projectile energy.
Abstract: The impact parameter dependence of the capture of a target L-subshell electron by a light projectile is calculated within the semiclassical impulse approximation (SCIA). The anisotropy of the resulting target 2 p vacancies is strongly dependent on impact parameter and projectile energy. As an example, (p, Ar) and (p, Ne) collisions are studied and the capture cross sections are compared with experimental data.
TL;DR: In this article, a method for the voltage distribution of a multiple-package air core power reactor was presented, and the necessary equivalent circuit elements required for the calculation of the impulse and the steady state voltage response were developed.
Abstract: This paper presents a calculation method for the voltage distribution of a multiple-package air core power reactor. The necessary equivalent circuit elements required for the calculation of the impulse and the steady state voltage response were developed. The results of the experimental investigation are in a good agreement with the calculated impulse voltage distribution. A more precise analysis of the steady state voltage distribution is presented, which has produced satisfactory results, judging from the correspondence between the calculated and the measured steady state voltage distribution.
TL;DR: In this paper, a general theoretical formulation of the Rydberg-atom neutral-atom inelastic processes is presented in order to define precisely the physical content of the simple impulse picture and to develop a systematic correction procedure.
Abstract: A general theoretical formulation of the Rydberg-atom-neutral-atom inelastic processes is presented in order to define precisely the physical content of the simple impulse picture and to develop a systematic correction procedure A simple modification of the impulse amplitude is then introduced to incorporate the distortion effect caused by the presence of the core of Rydberg atom A preliminary calculation provides a reasonable description of the inelastic scattering involving low principal quantum numbers as well
TL;DR: In this paper, it was shown that the anomalies of the Coulomb T matrix introduce corrections to the impulse approximation which do not depend on this ratio, and that more accurate estimates lead to a dependence of their correction on the charge asymmetry.
Abstract: For electron capture in asymmetric ion-atom collisions the projectile-target charge ratio is a natural expansion parameter. Recently Macek and Taulbjerg (1981) have claimed that the anomalies of the Coulomb T matrix introduce corrections to the impulse approximation which do not depend on this ratio. The authors show that this is due to the approximations they introduced, and that more accurate estimates lead to a dependence of their correction on the charge asymmetry. This correction may nevertheless be important even for rather asymmetric systems.
TL;DR: In this article, Glimm's scheme is used to obtain the solution for the shallow water equations, which can be used to solve one-dimensional gas dynamic problems and is tested successfully on the dam break problems.
Abstract: Numerical solutions are given for surface waves generated by underwater explosions. The shallow water approximation is used for the governing equations. An axisymmetric initial impulse is applied to the surface of the water. The initial impulse distribution is taken from the results obtained by Falade and Holt. Due to the unavailability of the initial displacement distribution, the latter is assumed to be zero, but the method can work for the case when both initial impulse and displacement are presented. Glimm’s scheme is used to obtain the solution for the shallow water equations. The scheme was developed to solve one‐dimensional gas dynamic problems. With slight modification, the scheme can be used for the shallow water equations. It is tested successfully on the dam break problems. The calculations confirm the existence of the upper critical depth effect, namely, that for near surface explosions, the maximum amplitude surface wave is that generated by an explosion just below the surface.
TL;DR: In this article, the authors describe a method whereby impulses of known shape and spectrum can be reliably reproduced by using this technique and demonstrate that the method can be used to reproduce pulses of shorter duration than the impulse response of the transducer.
TL;DR: In this article, the authors determine the optical heating of an ideal gas, which is contained in a cylinder equipped with a piston having a given arbitrary motion and which is coupled to a heat bath, so that the work produced is maximal given a total pumping energy.
Abstract: We determine the optical heating of an ideal gas, which is contained in a cylinder equipped with a piston having a given arbitrary motion and which is coupled to a heat bath, so that the work produced is maximal given a total pumping energy. We show that the optimal heating is impulsive and we determine the location of the impulse. Efficiency and thermodynamic analyses are obtained for sinusoidal piston motion.