Showing papers on "Impulse (physics) published in 1980"

Impulse Impedance of Grounding Grids

Abstract: A method and an empirical formula to calculate the inductance of square grounding grids fed at either centre or one of the corners is presented. Empirical formulae for the effective area and impulse coefficient for centre fed and corner fel square grids are determinel. The valility of the analytical methol has been verified experimentally with model tests. It is shown that the effect of soil ionization on the impulse impedance of grounding grils can be ignored for grounding grids in high voltage sub-stations.

On linear shift-variant digital filters

Abstract: The paper considers filters described by linear shift-variant difference (LSV) equations. We present the notion of a generalized transfer function and discuss the frequency characteristic of a shift-variant digital filter in terms of the generalized transfer function. A method is presented for determining LSV difference equations from a certain class of impulse responses, and vice versa. In addition, some properties of the impulse response and the generalized transfer function of a shift-variant system are investigated in the present work.

Impulse Impedance of Buried Ground Wire

Abstract: The performance of ground electrode under impulse currents must be known if problems concerning lightning protection and transients under ground faults are to be accurately analysed. This paper deals with such performance and establishes a simple analytical expression to determine the impulse impedance of a buried ground wire to a short impulse discharge, taking into account its parameters like metallic resistance, inductance, etc.

Dynamics of ventilation, heart rate, and gas exchange: sinusoidal and impulse work loads in man

Abstract: Dynamic characteristics of ventilation, heart rate, and gas exchange in response to sinusoidally varying work loads were analyzed in four male subjects, exercising in the upright position on a bicycle ergometer. Mean work-load and sinusoidal amplitude were about 1.5 and 0.9 W/kg, fat-free mass), respectively. Seven different frequencies were used, the periods ranging from 12 to 0.75 min. To further investigate the linearity of the variables under study, 10-s impulse loads were also applied to three of the four subjects. Harmonic analysis of the sine-wave data and comparison of the sine-wave fundamental responses with the impulse frequency responses showed that only O2 uptake behaves in a linear fashion. Ventilation and CO2 production showed quasi- to nonlinear behaviors, whereas the responses of heart rate and alveolar partial pressures were clearly dependent on the type of forcing used. By means of mathematical parameter identification techniques, it was found that the individual frequency responses of O2 uptake could be almost completely described by a four-parameter transfer function with parameter values showing second-order underdamped to critically damped dynamics.

Primer vector theory applied to the linear relative-motion equations

Abstract: Prime vector theory is used in analyzing a set of linear relative-motion equations - the Clohessy-Wiltshire (C/W) equations - to determine the criteria and necessary conditions for an optimal N-impulse trajectory. The analysis develops the analytical criteria for improving a solution by: (1) moving any dependent or independent variable in the initial and/or final orbit, and (2) adding intermediate impulses. If these criteria are violated, the theory establishes a sufficient number of analytical equations. The subsequent satisfaction of these equations will result in the optimal position vectors and times of an N-impulse trajectory. The solution is examined for the specific boundary conditions of: (1) fixed-end conditions, two impulse, and time-open transfer; (2) an orbit-to-orbit transfer; and (3) a generalized renezvous problem.

On the semiclassical impulse approximation for electron capture in asymmetric ion-atom collisions

Abstract: A derivation of the impulse approximation for the capture of a targetK-shell electron by a light projectile in ion-atom collisions is given in the framework of the semiclassical approximation. The impact-parameter dependence of the capture probability is calculated numerically without further approximations, and shows good agreement with recent experimental results for protons colliding with Ne and Ar. The validity of several peaking approximations and the relation to ionisation theories is briefly discussed.

Flashover Characteristics of Extremely Long Gaps in Transformer Oil under Non-Uniform Field Conditions

Abstract: Flashover characteristics of rod-rod and rod-plane electrode configurations in transformer oil are studied for extremely long gap lengths in the range of 150 to 1000 mm under conditions of lightning impulse, switching impulse, and alternating current voltages. The relation between flahsover voltage and gap length and the polarity reversal effect for switching impulse voltages are described in detail.

The arterial system characterised in the time domain

Abstract: When an impulse of flow is applied to the arterial system then the resulting pressure, the impulse response, is a characterisation of the arterial tree. The impulse is generated by means of an occluder around the ascending aorta. The impulse response shows an initial sharp peak followed by an exponential decay with two peaks superimposed on it. The exponential decay is due to diffuse reflection and is linked to the windkessel properties of the arterial tree.1 The superimposed peaks arise from two distinct reflection sites in the arterial tree. By means of the pulse wave velocity the location of these reflection sites may be calculated; one is found in the bed distal to the brachiocephalic and subclavian arteries and the other in the bed distal to the descending aorta. The distinct reflections are linked to the reflection sites in the asymmetric T-model of the arterial tree.2 Vasodilatation (nitroprusside) and vasoconstriction (angiotensin) mainly influence the diffuse reflections, while the locations of the distinct reflection sites appear to be unchanged. Inflation of a balloon in the descending aorta shows up as a sharp peak in the impulse response function. The results obtained are compared with the impulse response function computed from pressure and flow waves in the steady-state.3

Digital roughness sensor

Abstract: An engine roughness sensor for generating speed normalized digital roughness signals indicative of the variations in magnitude between successive torque impulses imparted to the engine's crankshaft by measuring the period or time it takes the crankshaft to rotate through the same angle for each torque impulse is disclosed herein. The digital roughness signal is normalized as a function of engine speed by dividing the measured magnitude of each torque impulse by a signal indicative of the engine speed to reduce the magnitude of operator induced variations in the generated roughness signals. In an alternate embodiment, the disclosed engine roughness sensor generates a second difference roughness signal which is the difference between the sequentially generated roughness signals.

Thermal and impulse coupling to an aluminum surface by a pulsed KrF laser

Abstract: The amount of heat deposited on an aluminum target after irradiation in air by a KrF laser at 249 nm has been measured to be ∼40% of the incident pulse energy for long pulses (0.5 μsec), moderate flux levels (106–108 W/cm2), and spot diameter ⩾0.5 cm. The impulse generated by the laser has also been measured. Significant impulse levels were observed at low incident fluence levels.

Numerical Correction of HV Impulse Deformed by the Measuring System

Abstract: High voltage impulse measuring systems give an output signal that is a deformed replica of the input signal. This paper presents a method of reconstructing the input signal from the deformed output. The method retains its validity even if the input impulse is shorter than the duration of the step function response.

Digital Impulse Recorder for High-Voltage Laboratories

Abstract: A digital recorder has been developed for use in HV laboratories as a prospective replacement for conventional impulse oscilloscopes. The new apparatus has a sufficiently high time resolution to record the fastest microsecond impulses used for HV testing and also allows slower switching transients to be monitored.

Impulse approximation calculations for capture of K-shell electrons by fast light nuclei

Abstract: A succession of peaking approximations is used to study the structure of the impulse approximation in its impact parameter form. The results of numerical calculations are compared with experimental results.

Impulse Propagation in Excitable Systems

Abstract: Publisher Summary This chapter focuses on impulse propagation in excitable systems. The interaction of diffusion with reaction dynamics, which exhibit multiple steady states or temporal oscillations, can lead to a variety of spatio-temporal patterns. However, this can also occur in cases where the reaction dynamics has a unique stable steady state as a global attractor. A solitary pulse, propagating into a resting medium, travels with fixed speed c o . However, in a train of more than one pulse, a non-leading pulse cannot advance into a medium at rest, so its speed in general cannot equal c o . The speed of the train is determined by its period and this dependence constitutes a dispersion relation. Dispersion effects can be assessed from a description of speed versus temporal period as opposed to spatial period; which is more suitable and depend on the geometry of the medium and time scale of observation. The chapter presents alteration of spatio-temporal pattern during propagation.

Oscillator actuated hydraulic impulse device

Abstract: An oscillator actuated hydraulic impulse of the type including a spool valve actuated by an alternating signal from an oscillator to switch the hydraulic pressure in a double acting cylinder in order to cause reciprocating motion of a piston which strikes a boring tool. The hydraulic impulse device further includes a means for controlling the transition from the impulse stroke to the return stroke of the piston. In some embodiments, the hydraulic impulse device may further include a means for varying the duration of the impulse stroke and the return stroke of the piston.

A symmetric impulse approximation for charge exchange

Abstract: A symmetric form of the impulse approximation for charge exchange is developed. This approximation preserves the equivalence of post and prior forms of the transition amplitude. As in the usual impulse approximation the dynamics of charge transfer is seen primarily as the ionisation of a bound state. The usual impulse approximation considers ionisation of an electron from the bound state, whether initial or final, of the stronger potential. However, the symmetric form presented here includes contributions from the ionisation of an electron from both initial and final bound states.

Analytical representation of transient ultrasonic phased-array near- and far-fields

Abstract: The present contribution provides a method for the derivation of analytical near- and far-field expressions for the pressure step-function response of nonuniformly excited ultrasonic transducers modeled as pistons of arbitrary shape in an infinite rigid baffle. Explicit inversion of the Laplace transformed ultrasonic field using Cagniard's idea results in elementary functions or definite integrals of elementary functions, depending on the assumed nonuniform aperture distribution. The basic signal distortion is illustrated in terms of three-dimensional space-time plots of the pressure unit step-function response of a rectangular uniform aperture. The corresponding results for a phased-array transducer are also given. In addition, we investigate the pressure profile on the axis perpendicular to a uniform rectangular piston and its horizontal radiation pattern for different bandwidths of the exciting impulse.

Thermal collisions of Rydberg atoms with neutrals

Abstract: A new theoretical method outlined here for an important inelastic mechanism based on A-B+ encounters in A-B(n) thermal collisions indicates a substantial contribution to l-changing transitions which therefore cannot be viewed as proceeding via (e-A) encounters alone. Recent descriptions of l-changing thermal collisions which are based on an (e-A) impulse treatment appear defective in that they disregard certain impulse validity criteria and yield results which greatly exceed the upper limit specified by the basic impulse expression, and do not recognise the above important inelastic mechanism associated with the non-inertiality of the core.

Recoilless air weapon

Abstract: In a sporting air gun in the nature of a recoilless pressurized-air weapon, having a recoilable system which is translatably mounted so as to slide forward and backward on the gunstock of the weapon in a direction which is generally longitudinal. The recoil system compensates by opposed motion the impulse from the firing of the weapon arising from the impulse of each projectile, from the propellant gas, and from individual components which are accelerated for the purpose of the firing. The system minimally comprises a breech casing to which a barrel, a firing mechanism, other functional parts of the weapon, or added masses may be attached to increase the weight of the system. The system has a center of mass lying off the line of action of the impulse resulting from the firing, whereby a torsional impulse is superposed on the firing-resultant impulse. The improvement in the air gun includes at least one torsional impulse generator which is positioned in or on the weapon. This generator forms an autonomous functioning unit with other parts of the weapon, whereby the torsional impulse resulting from the generator is simultaneous with and directed opposite to the torsional impulse which is induced by the recoil system in the firing phase of operation, whereby the torsional impulse from the generator acts substantially in the same plane as or substantially in a parallel plane to the torsional impulse from the recoilable system.

Impulse breakdown and prebreakdown corona processes in sf6sf6 and sf6/n2 mixtures

Abstract: The paper reports on impulse breakdown and prebreakdown studies in rod-plane gaps for a variety of SF 6 /N 2 mixtures at pressures up to 3 bar and spacing up to 20 mm. The results show that the stabilisation process is less effective under impulse conditions and that the supply of initiatory electrons greatly influence the characteristics. Image-intensifier/converter camera records of the discharge development have been obtained and compared with dc observations. It is shown that stepped-leader formation occurs even in such short gaps and that the occurrence of the leader is responsible for the loss of corona stabilisation in nonuniform-field gaps.

Space-time response of a cloud communication channel to an optical signal

Abstract: An optical signal,an impulse in space and step in time,is incident on a plane,parallel fixed,homogeneous cloud. The incident signal is modelled as a stream of photons, each of them executing a random walk. A Monte Carlo simulation technique is applied to obtain the space-time response of the channel when an optical receiver with a specified field of view is located at a specified distance below the cloud. The response is obtained as angular, spatial and temporal dispersions. Various simulation steps are described. For thin clouds two variance reduction techniques, i.e. Russian roulette and forced collision, are used. It is shown that the bottom of the cloud tends to diffuse uniformly and the 3 dB exit beam width saturates. The rise time in this channel is found to be of the order of several nanoseconds.

Fluidic angular rate sensor with integrated impulse jet pump assembly

Abstract: An angular rate sensor includes a unitary structure impulse pump for providing fluid under pressure, at a constant rate of flow, to a nozzle disposed at one end of a jet chamber to form a constant flow fluid jet, the jet chamber including a pair of temperature sensitive elements disposed at the other end in such a manner as to be differentially cooled by the fluid jet in dependence on the angular rotation of the sensor.

Transfer function determination from impulse responsevia walsh functions

Abstract: This paper presents a new method for calculating a rational transfer function matrix using a Walsh expansion of the impulse response matrix. The algorithm proposed appears to be computationally convenient owing to certain properties of the Walsh functions. An example is given to illustrate the method.