Showing papers on "Impulse (physics) published in 1976"

Dynamic properties of the responses of single neurones in the cochlear nucleus of the rat.

Abstract: 1. The dynamic properties of unit responses to amplitude-modulated tones were studied using modulation with pseudorandom noise and described by cross-covariance and integrated cross-covariance functions between the discharge rate and the modulation. Under the experimental conditions used, these two functions are valid approximations of the system's impulse and step response functions respectively. 2. On the basis of their impulse response functions units could be classified into two groups, Type I with a low adaptation and Type II with a large degree of adaptation as well as a damped oscillation in their impulse response functions. 3. The response pattern of the Type II units is most likely the result of a negative feed-back striving to keep the discharge rate at a nearly constant level. 4. The cross-covariance functions are shown to remain unchanged during long duration recordings from the same unit.

Sequential impluse model of direct reactions

Abstract: A model in which the reaction A(BC, C) AB occurs as the result of a sequence of two hard sphere elastic impulses between the A–B and B–C pairs is analyzed. It is shown that the limits of the product velocity vector distribution can be readily obtained from the analytic geometry of the impulse sequence, and that an analytical expression for the detailed product distribution for all mass combinations and energies can be deduced. The results show a propensity for processes in which the velocity of the C atom is changed very little and which therefore lead to products near the spectator stripping velocity. The angular distribution is dependent on, but relatively insensitive to, the ratio of the mutual hard sphere diameter of B and C to their bond distance. The predictions of the model are generally consistent with the features found in the experimental investigations of high energy ion–molecule reactions.

Inverse problem for a vibrating beam

Abstract: The problem of inferring the flexural rigidity and density of a beam from its eigenfrequencies is considered for the particular case in which one end is clamped. It is shown that three spectra associated with three sets of boundary conditions at the other end are required in order to insure a unique solution of the inverse problem. Furthermore, it is shown that this data set is equivalent to the information contained in the time history of the displacement and slope of the free end of the beam set in motion by a concentrated impulse.

Influence of rain on switching impulse sparkover voltage of large-electrode air gaps

Abstract: The paper deals with a laboratory investigation into the influence of rain on the switching impulse sparkover characteristics of large-sphere and toroid plane air gaps. Tests were also carried out on coneterminated rod-plane gaps for reference purposes. The factors investigated include the high voltage electrode geometry, nature of the surface, rain intensity as well as the impulse form and polarity. Attention is also paid to the influence of rain on the statistical dispersion of the sparkover voltage and on the nature of the cumulative probability curve. A general correlation, valid for a wide variety of electrodes, has been established between the mean spark-over voltage gradient for positive switching impulses under dry conditions, and the corresponding influence of rain on the breakdown voltage.

Electric game set

Abstract: A game set comprises a board having indicia which relate to indicia on individual pieces which can be associated with the board. There is an interconnection between the pieces and electrical impulse means also associated with the board whereby if the pieces are placed in incorrect positions on the board the impulse means will respond, such as by actuating a buzzer. The connections are identical, but the pieces need not be.

Generation of the nervous impulse and periodic oscillations

Abstract: Usually the models for the excitation and propagation of the nervous impulse are studied either in the space-clamp situation or on a model axon extended on both sides to infinity. Following Fitzhugh in the present paper the release of an impulse train at the axon hillock is studied within the scope of Fitzhugh's BVP model. The existence and stability of periodic oscillations are studied by direct methods, also the relation to Lienard's equation. The exact correspondence between the BVP model and the socalled Nagumo-equation is established. For typical examples the solutions are computed by numerical methods.

Impulse sealing apparatus

Abstract: Impulse sealing apparatus having a forced cooling cycle following the impulse heating cycle, and comprising in combination, a vortex tube which converts a source of compressed gas at ambient temperature into a cold gas stream, a heat exchanger cooled by the cold gas stream generated by the vortex tube, a second source of pressurized ambient temperature gas communicating with the heat exchanger and cooled thereby, and means for removing the second source gas stream from the heat exchanger and communicating with the impulse sealer for supplying chilled gas thereto.

Improved cw laser penetration of solids using a superimposed pulsed laser

Abstract: The enhancement of cw laser melt‐through of solids resulting from melt removal produced by a blowoff impulse generated by short superimposed laser pulses is investigated. A simple model is used to develop an expression for the minimum impulse criteria.

Modelling a Loaded Two-Way Pneumatic Actuator

Abstract: This paper describes experiments on a low-pressure pneumatic actuator and load. An impulse test is described, in which the transient behaviour of a loaded actuator, operating in a particularly simp...

Antenna for underground pipe detector

Abstract: An apparatus and method wherein an electrial impulse source transmits a radar-type signal through an antenna into the ground and is reflected by a target. The reflected signal or echo is detected by the antenna and an analog-to-digital converter converts it to a digital form which may be readily operated on, stored and recalled. A memory stores the information until recalled for comparison with a subsequent signal to give an indication of the location of metallic and non-metallic buried targets.

High-Speed Photography of Surface Flashover Across High-Density Alumina in Vacuum under Direct and Impulse Voltages

Abstract: High-speed streak and framing photography of surface flashover across solid insulators in vacuum is reported. Experiments were performed with direct and impulse voltages. It is shown that the initial propagation of a visible arc across an alumina surface in vacuum occurs at a speed greater than 109 cm ? s-1 . It is shown that previously observed two-stage arcs under impulse voltages are the result of the interaction between the external supply and the arc impedance.

Transient response from a small antenna in an anisotropic plasma

Abstract: The linear response of a cold anisotropic plasma to a point source under impulse excitation displays a frequency spectrum having maxima at the two frequencies determined by the resonance cone condition and at the upper hybrid frequency. A laboratory demonstration is reported.

Generation of a stepped ultrasonic plane wave: application to piezoelectric transducer calibration

Abstract: A method allowing the generation of an ultrasonic plane wave by means of a thick piezoelectric transducer excited by a short current impulse is described. The resulting pressure step is then used to determine experimentally, in shape and amplitude, the time and frequency responses of different probes subjected to a step, as well as, pressure impulse (obtained by derivation). Finally, the validity of the results is confirmed after comparison with those provided by a receiving transducer, already calibrated using the reciprocity method.

Impulse breakdown of positive rod-plane gaps in hydrogen and hydrogen-SF 6 mixtures

Abstract: Impulse breakdown voltages have been measured for negative rod-plane gaps in hydrogen and in H2/SF6 mixtures for pressures in the range 0.5-3.0 bar and electrode spacings up to 0.25m. In hydrogen, the negative-impulse breakdown voltages are 60-100% higher than those previously reported for positive polarity: However the increase in breakdown voltage with the addition of small quantities (?1%) of SF6 is smaller than for positive-impulse conditions and is confined to pressures below~H2 bar, with the result that the positive and negative impulse strengths of rod-plane gaps in such low SF6-concentration mixtures are almost equal. The results are discussed with reference to observations of the effect of SF6 on the prebreakdown corona activity.

Switching impulse results obtained on the outdoor testing area at renardieres

Abstract: This paper reports the switching impulse test results obtained simultaneously indoors and outdoors. New tests on the conductor-ground and conductor-rod configurations are presented. Mathematical expressions have been established to represent these results, and some explanation has been attempted by the study of the electrostatic field distribution.

Solid Propellant Pulsed Plasma Propulsion System Design

Abstract: Fundamental definitions, a few semiempirical correlations of experimental data, and two design constraints of solid propellant-pulsed plasma thrusters are used to illustrate the design analysis of such an electric propulsion system. The semiempirical relations presented have been generated from thruster data covering impulse bits extending from 2.7 dyne-sec (6/i Ib-sec) to 31 mN-sec (7 mlb-sec) and a specific impulse up to 5100 sec. They are descriptive to within about 8%.

Method and apparatus for forming a material web

Abstract: A web is formed from particulate material, for example wood fibres, by depositing the fibres on a movable deposition surface in a chamber. The particulate material is carried to the surface in an air stream to form a composite material flow which is caused to oscillate across the surface by impulses from separate control means preferably disposed on opposite sides of the stream. The control means is preferably opposed control flows which are caused to vary alternatingly between a minimum and a maximum impulse by use of one or more fluidistors. The fluidistors may be controlled by self-oscillation or by measuring the evenness of the particulate material deposited on the deposition surface. The control may also be effected by adjusting the walls of the chamber to utilize the coanda-effect. The particulate material may be admixed with additives from the control flow and may be charged electrostatically.

The physics of left ventricular ejection and its implications for muscle mechanics.

Abstract: The ejection stage of the left ventricle of the heart is analyzed using the proper form of Newton's Second Law of Motion and a simple cylindrical ventricular model. The Laplace relation is then used to calculate the dynamic relationship between force, velocity and acceleration in an average, circumferential, equitorial myocardial wall fiber, yielding: Fm=Fa + Cacf + Dvcf2 where Fm is the force in the fiber, Fa the fiber force that would be required to match aortic pressure, acf the acceleration and vcf the velocity of shortening of the fiber. C is a constant, and D is a geometrical parameter that varies smoothly with time. The significance of the above equation is discussed both in terms of muscle function (total muscular force) and pump function afterload Fa and the differential force, Fm - Fa): The afterload component Fa provides the pressure head needed to force the blood through the capillaries (Poiseuille flow) and varies with time in accordance with the impedance of the vascular system (auxotonic loading). The differential component force Fm - Fa provides the ventricular impulse needed to overcome the inertia of the system due to (1) the mass of the blood, (2) the geometrical constriction of the outflow tract as one moves downstream (Bernoulli effect), and (2) the moving ventricular walls. Analysis of this sort should help in attempting to separate the intrinsic properties of cardiac muscle and the pump function of the intact heart. The important role that isolated muscle experiments can play in this effort is discussed.

Recoil impulse received by metal targets as a result of interaction with microsecond CO2 laser radiation

Abstract: The first measurements were made of the recoil impulse J received by bismuth, lead, zinc, and aluminum targets in vacuum as a result of interaction with microsecond CO2 laser pulses of I = 108–109 W/cm2 intensity. The measurements were carried out under conditions of planar one-dimensional target damage. It was found that the specific recoil impulse J/E (E is the pulse radiation energy) was independent of the intensity I, which had been observed earlier only in the low intensity range (I ~ 106–107 W/cm2) and correspondingly low target temperatures. This suggested a need for developing a theory of steady-state "advanced" evaporation at high laser radiation intensities. Possible physical mechanisms of this process were considered.

Locating of intracorporeal catheters already in place - using impulse generator linked to skin mounted electrodes

Abstract: A device for the accurate position finding of already innerted intracorporeal catheters plastic heart and vessel catheters produces direct-current impulses which are introduced into the patient by means of electrodes attached to the skin. The location of the catheter tip is then done by means of a commercial E.C.G. machine, such that the electrical potential between the catheter tip and the skin mounted electrode is detected by the E.C.G. machine. The positioning device may also produce various forms of alternating current impulses which allows usage of several electrical fields simultaneously if any one impulse type is transmitted only by specific skin mounted electrodes.

Investigation of gasdynamic processes and recoil impulse produced by optical breakdown of air near a target surface by radiation of an electron-beam-controlled CO2 laser

Abstract: An experimental investigation was made of gasdynamic processes resulting from the action of high-power (109 W) radiation of an electron-beam-controlled CO2 laser on a metal target The large area of the resultant optical breakdown (up to 27 cm2), which appeared near the target surface, and the short duration of the laser pulses (τ1/2 = 120 nsec) made it possible to establish nearly one-dimensional gasdynamic motion The development of a plasma jet under these conditions could be described by the model of a strong planar explosion The breakdown threshold of air qth 5×107 W/cm2 decreased under the action of the radiation emitted from the plasma jet The velocity of propagation of a wave of absorption of the laser radiation differed from the theoretical dependence predicted for an optical detonation wave The ratio of the recoil impulse to the energy, 126 dynsecJ–1, was measured and it was found that high values of the impulse could be obtained in large focusing spots

Film frame counter for camera - has impulse cover at top and counter devices coupled to film transport and display systems

Abstract: The device is for indicating the frame number of a film in a camera with a filter transportation system, and has an impulse generator which produces at least one single impulse when the film transportation system has been completely operated. This impulse generator is connected to an impulse counter which counts the impulses generated by the impulse generator device during film transport. An indicator is provided to display, in an optical manner, the status of the impulse counter, typically a forwards-backwards counter.

Impulse activated counting device

Abstract: Method and apparatus for actuating a counting device for recording and stng data. The invention comprises an activator for a counter device and includes a mass or weight having an eccentric center of mass which is freely pivotable in one plane in response to an externally applied impulse force of a predetermined magnitude to apply a torque force to a shaft which, on rotation thereof under the influence of said torque force, activates the counter mechanism to record a count. Means are also provided to apply counter torque force of a constant predetermined magnitude or value to the shaft so that the counting device is actuated only in response to a resultant torque force of a predetermined magnitude or value generated by the impulse.

Fluctuation Mechanism of D. C. Partial Discharge in Polyethylene and Impulse Noise in Submarine Cable

Abstract: It has been made clear theoretically and experimentally that the d.c. partial discharge in polyethylene occurs in accordance with the Poisson process. This phenomenon is explained by assuming that the fluctuation of the d.c. partial discharge is due to the fluctuation of the current density, that is, the fluctuation of the carrier concentration in polyethylene. The repetition rate of the d.c. partial discharge is closely related to the current density, and is expressed as f=f0Vnexp (-W/kT) (n=4, W=1.0 eV). It is then possible to estimate the number of impulse noises as a result of the d.c. partial discharge occurring in a cable, and to clarify the effect of the d.c. partial discharge on data transmission.

Impulse and Frequency Response of Channel Electron Multipliers

Abstract: Publisher Summary This chapter analyzes the secondary electron multiplication within the channel electron multipliers (CEM) by computer simulation to obtain the impulse response characteristics of a CEM, which is excited by a single electron Transit time, rise time, and full width at half maximum of the output pulse are obtained from the computer simulation The Fourier transform of the output pulse gives the frequency response of the CEM The analysis shows that thinner channel plates with finer capillaries have faster responses Calculations for a channel 40 μm in diameter and 2 mm long operated at 3 kV show it to have a flat response up to 53 GHz and to have an output pulse width of 61 ps The results show that a CEM plate of fine microchannels is superior for high speed operation to the crossed field electron multiplier designed for high speed photon detection The phase shift that has a linear relation to frequency is described It is found that only signal delay is important in describing the transmission of the wave