Showing papers on "Acceleration published in 1983"

A modification of the newtonian dynamics as a possible alternative to the hidden mass hypothesis

Abstract: The author considers the possibility that there is not, in fact, much hidden mass in galaxies and galaxy systems. If a certain modified version of the Newtonian dynamics is used to describe the motion of bodies in a gravitational field (of a galaxy, say), the observational results are reproduced with no need to assume hidden mass in appreciable quantities. Various characteristics of galaxies result with no further assumptions. The basis of the modification is the assumption that in the limit of small acceleration a very low a0, the acceleration of a particle at distance r from a mass M satisfies approximately a2/a0 a MGr-2, where a0 is a constant of the dimensions of an acceleration.

Stochastic simulation of high-frequency ground motions based on seismological models of the radiated spectra

Abstract: Theoretical predictions of seismic motions as a function of source strength are often expressed as frequency-domain scaling models. The observations of interest to strong-motion seismology, however, are usually in the time domain (e.g., various peak motions, including magnitude). The method of simulation presented here makes use of both domains; its essence is to filter a suite of windowed, stochastic time series so that the amplitude spectra are equal, on the average, to the specified spectra. Because of its success in predicting peak and rms accelerations (Hanks and McGuire, 1981), an ω -squared spectrum with a high-frequency cutoff ( f m), in addition to the usual whole-path anelastic attenuation, and with a constant stress parameter (Δ σ ) has been used in the applications of the simulation method. With these assumptions, the model is particularly simple: the scaling with source size depends on only one parameter—seismic moment or, equivalently, moment magnitude. Besides peak acceleration, the model gives a good fit to a number of ground motion amplitude measures derived from previous analyses of hundreds of recordings from earthquakes in western North America, ranging from a moment magnitude of 5.0 to 7.7. These measures of ground motion include peak velocity, Wood-Anderson instrument response, and response spectra. The model also fits peak velocities and peak accelerations for South African earthquakes with moment magnitudes of 0.4 to 2.4 (with f m = 400 Hz and Δ σ = 50 bars, compared to f m = 15 Hz and Δ σ = 100 bars for the western North America data). Remarkably, the model seems to fit all essential aspects of high-frequency ground motions for earthquakes over a very large magnitude range . Although the simulation method is useful for applications requiring one or more time series, a simpler, less costly method based on various formulas from random vibration theory will often suffice for applications requiring only peak motions. Hanks and McGuire (1981) used such an approach in their prediction of peak acceleration. This paper contains a generalization of their approach; the formulas used depend on the moments (in the statistical sense) of the squared amplitude spectra, and therefore can be applied to any time series having a stochastic character, including ground acceleration, velocity, and the oscillator outputs on which response spectra and magnitude are based .

Solar type II radio emission and the shock drift acceleration of electrons

Abstract: Many of the properties of energetic electrons and ions accelerated by interplanetary shock waves can be understood in terms of the shock drift acceleration mechanism. In this paper we show that the shock drift acceleration of electrons can be responsible for solar type II radio bursts as well. We review the shock drift acceleration mechanism and show that the streaming distribution of reflected electrons produced upstream of the shock front by this mechanism can be unstable to the generation of electrostatic plasma waves, which in turn interact to produce the observed radio emission. We derive constraints upon the density and energy of suprathermal electrons required to produce a typical type II burst.

Apparatus and method for monitoring motion of a railroad train

Abstract: An apparatus for monitoring the motion of a railroad train includes an on-board unit which computes the speed, acceleration/deceleration, and distance traveled events of the train and stores such computed data for retention by a non-volatile memory after a power interruption or outage occurs. The apparatus also includes a portable unit to which the on-board unit, or the data retaining memory thereof, can be connected for conducting data transfers from the on-board unit memory to the portable unit. Once stored in the portable unit, the information can be formated and displayed as a history of the train operation for management and maintenance personnel, for example.

On the application of the mode‐acceleration method to structural engineering problems

Abstract: Mode-superposition has been extensively used in computing the dynamic response of complex structures. Two versions of mode-superposition, namely the mode-displacement method and the mode-acceleration method, have been employed. The present paper summarizes the results of a systematic study comparing the accuracy of the mode-displacement and mode-acceleration methods when applied to structures with various levels of damping or various excitation frequencies. The paper also discusses several details concerning the implementation of the mode-acceleration method.

Creation of high‐energy electron tails by means of the modified two‐stream instability

Abstract: Particle simulations of the modified two-stream instability demonstrate strong electron acceleration rather than bulk heating when the relative drift speed is below a critical speed Vc A very interesting nonlinear mode transition and autoresonance acceleration process is observed which accelerates the electrons much above the phase speed of the linearly unstable modes Simple criteria are presented that predict the value of Vc and the number density of the accelerated electrons

First-order Fermi acceleration in solar flares as a mechanism for the second-step acceleration of prompt protons and relativistic electrons

Abstract: Solar flare data from June 27, 1980 balloon-based observations were studied in terms of the hard X ray component. A temporal delay of 3 sec was observed for the X ray emissions above 235 keV. The delay occurred relative to the low-energy electrons and indicated a second acceleration stage. An estimation of the acceleration rate of the first-order Fermi process operating in a closed flare loop was found to be in agreement with the resulting data, including the acceleration of both protons and relativistic electrons. Additional support for the first-order Fermi process is noted in the fact that flares generally occur in magnetic loops, a condition which allows energetic particles to continually interact with the upward moving shock fronts. A correlation has also been observed between the delay times and the H-alpha areas, encouraging the interpretation that the delay times are the shock transit times.

Vibration Absorption Control of Industrial Robots by Acceleration Feedback

Abstract: This paper describes an electrical control method of absorbing arm vibrations of industrial robots Arm vibration problems are divided into two categories: resonance vibration phenomenon depending on actuator velocity and transient oscillations caused by acceleration change of actuators Because resonance frequency of an industrial robot changes more than double due to the arm posture, mechanical vibration absorbing methods may not be easily utilized The method applied in this paper is to compose dampers as electric manners by utilizing arm acceleration feedback to actuators of an industrial robot Acceleration sensors are attached on three axes which construct a robot arm Acceleration signals are fed back to the corresponding actuators passed through phase compensation circuits By experiments applied to an industrial robot, this method has been proved to be effective in eliminating both resonance and transient vibrations According to this control, a smart motion industrial robot which does not have resonance characteristics and operates speedily and smoothly has been realized

Improved resonance technique for materials characterization

Abstract: An improved resonance apparatus for materials characterization is described. The apparatus accurately determines the propagation constants of an extensional acoustic wave by exciting a bar of material at one end with a noise source, while the other end is allowed to move freely. Miniature accelerometers measure the acceleration at two locations and their output signals are analyzed by a dual channel FFT spectrum analyzer. At certain frequencies, the acceleration ratio goes through resonant peaks whose amplitudes and frequencies are related to the Young’s moduli and loss factors of the material. The apparatus is capable of measuring the acceleration ratio over a frequency range of 25 Hz to 20 kHz. As illustrations of the technique, Young’s modulus and loss factor were determined on a viscoelastic material; polyurethane (over a temperature range −13.4° to 81 °C) and on two metal matrix composite materials: a silicon carbide–aluminum and a graphite–aluminum. The apparatus was found to be a fast and reliable method to determine dynamic constants.

Ion acceleration in the suprauroral region: A Monte Carlo Model

Abstract: The acceleration of ions and the formation of ion conics in the suprauroral region is studied using a model which includes the effects of wave-particle interaction, the inhomogeneous geomagnetic field, and field-aligned potential drops. Particle acceleration by interaction with turbulence is treated as a random process in a simplified way using a Monte Carlo technique. Applying the model to ion acceleration by lower-hybrid turbulence between 1000 and 5000 km, we find that the observed amplitudes of the waves are sufficient to accelerate ions to the energies often found in conics.

Azimuth determination for vector sensor tools

Abstract: This invention relates to mapping or survey apparatus and methods, and more particularly concerns derivation of the azimuth output indications for such apparatus in a borehole from the outputs or output indications of either an inertial angular rate vector sensor (or sensors) and an acceleration vector sensor (or sensors), or a magnetic field vector sensor (or sensors), and from the outputs of an acceleration vector sensor (or sensors). Borehole tilt is also derived.

Method and apparatus to automatically determine the weight or mass of a moving vehicle

Abstract: This invention teaches a method and apparatus for the determination of the weight of a moving vehicle driven by an internal combustion engine. The invention provides means for the determination of a value corresponding to the driving torque of the engine, and for the determination of an acceleration value corresponding to the acceleration of the vehicle. The measuring means are controlled in such a manner that the torque value can be determined at the same time as the acceleration value. Furthermore, a calculating device is provided in which one or two values of the driving torque value--determined at different times--as well as values of the acceleration variable--determined at said times--are utilized for the determination of a weight variable corresponding with the weight of the vehicle.

Ion heating and acceleration by strong magnetosonic waves

Abstract: Large-amplitude magnetosonic waves (kperpendicularB) with ..omega../sub ci/<..omega..<..omega../sub lh/ (..omega../sub ci/ and ..omega../sub lh/ are the ion-cyclotron and lower-hybrid frequencies) are investigated by particle simulation. Some ions are accelerated and trapped in the potential troughs of the waves; the v x B/c force accelerates these particles parallel to the phase fronts. Ultimately, the v x B/c force detraps the ions but only when v is much larger than the Alfven velocity; the wave is strongly damped by this effect.

Nonlinear hydrodynamic pressure on an accelerating plate

Abstract: A nonlinear theory is developed to determine accurately the hydrodynamic pressure on an accelerating vertical plate. The plate is assumed to move horizontally towards the fluid with an acceleration which may be expressed in a power series in time. The fluid is initially at rest and the plate motion is impulsive. When the horizontal plate displacement is small in comparison with the undisturbed fluid depth, the method of small‐time expansions is adopted to obtain analytical solutions up to and including the third‐order velocity potential. The free surface profile of the fluid is also determined. An example for the constant acceleration case is presented to illustrate the method.

Numerical evaluation of near-field, high-frequency radiation from quasi-dynamic circular faults

Abstract: We compute the near-field, high-frequency radiation from a circular crack expanding with constant rupture velocity and discuss the characteristics of the stopping phases. We then introduce rupture velocity jumps in the fracture process. The computed accelerations show the dominant role played by the rupture front kinematics. The high acceleration pulses are associated with sudden changes of the rupture velocity. For a sudden jump (or a sudden stop), there is no theoretical high-frequency limit to the spectral density of acceleration. In order to account for f max , we introduce a smooth deceleration of the rupture front over a time t ′ in place of a sudden stop. This results in a spectral fall-off for frequencies greater than 1/ t ′ and supports the interpretation of f max as a source effect.

Convergence acceleration in Monte Carlo computer simulation on water and aqueous solutions

Abstract: The convergence characteristics of standard Metropolis Monte Carlo calculations on liquid water and aqueous solutions are described, and documentation of the need for convergence acceleration procedures is presented. The acceleration procedures are additional importance sampling schemes added to the Metropolis method. The recently proposed ‘‘forced bias’’ and ‘‘preferential sampling’’ procedures are specifically considered. Comparative studies on liquid water at T=25 °C using the force bias method show that convergence is improved by a factor of 2–3 over standard Metropolis results. For aqueous solutions, force bias and preferential sampling procedures used separately and together were studied on a prototype aqueous solution problem based on the liquid water simulation. Neither method alone was found to be adequate for describing structural characteristics of solutions in realizations of the length presently used for simulations on pure liquids. A combination of the force bias and preferential sampling methods was found to be quite successful, and makes aqueous solutions accessible to simulation studies at levels of rigor commensurate with that obtained for pure liquids. Preliminary convergence acceleration results on [CH4]aq using the combined force bias‐preferential sampling acceleration methods are also presented.

Device for determining the at least approximately true speed of a motor vehicle

Abstract: The invention relates to a device for determining the at least approximately true speed of a motor vehicle during the phases in which it is retarded and/or accelerated due to wheel slippage, in which a simple accelerometer based on the principle of inertia and mounted fixed on the body supplies an acceleration signal which is continuously calibrated during the operating phase not endangered by wheel slippage by comparison with acceleration values determined from speed signals of speed sensors, and the true speed occurring is determined during the acceleration and/or retardation phases in an electronic evaluation device in accordance with the equation b being the calibrated acceleration signal and v0 the speed determined from speed signals of speed sensors at a time t0 not endangered by wheel slippage.

Acceleration/deceleration circuit

Abstract: An acceleration/deceleration circuit for raising or lowering a feed velocity, in order to achieve a commanded velocity, over a prescribed time constant irrespective of the magnitude of a change in velocity. The acceleration/deceleration circuit includes means (301) for computing a traveling distance along each axis every sampling period (T), a first storage section (#1 through #n) for storing n samplings of traveling distance components along each axis, a second storage section SUM for storing results of computation, and an arithmetic section (ADD, ACC, DIV) for performing an operation: .sub.Δ Xn-.sub.Δ Xo+St→St where .sub.Δ Xn represents the latest sampled traveling distance component, .sub.Δ Xo represents the oldest sampled traveling distance component among the traveling distance components stored in the first storage section, and St represents the contents of the second storage section, and for dividing the result St by n, wherein the result St is stored in the second storage section, and St/n is output as a traveling distance component at a present sampling instant.

Tracking system for controlling the radial positioning of a transducer on a disc medium

Abstract: A data track searching device capable of switching between two modes; one being the rough searching mode in which a transducer is displaced at a high velocity to a desired track and the other being the fine searching mode which follows the rough searching mode and in which the transducer is displaced at a relative low velocity and positioned over the proper or desired track. The operating point of a tracking element is shifted or deviated as a result of the high-velocity displacement of the transducer in the rough searching mode so that stable searching cannot be ensured. According to the present invention, therefore, the acceleration of the transducer in the rough searching mode is detected and a signal representative of the thus detected acceleration is applied to the tracking element so that the shift or deviation of the operating point of the tracking element can substantially made nil.

Optimal control of automobiles for fuel economy

Abstract: This paper describes an application of dynamic programming to determining optimal driver control of an automobile for fuel economy. The objective function is provided by a simulator that uses vehicle performance maps derived from statistical analysis of road data collected by the authors. One dynamic program controls acceleration as a function of time subject to constraints on speed, acceleration, and distance covered. Another controls acceleration and gearshift subject to constraints on speed, acceleration, and time required to shift gears. Results are presented for acceleration to a given cruising speed, driving over hills while achieving a given average speed, and driving from one stop sign to another.

Method for determining acceleration

Abstract: An accelerometer has two proof masses each constrained from movement by a beam resonant force transducer The proof mass-force transducer systems are mounted with the sensitive axes of the proof masses aligned and the force transducers arranged so that their resonant frequencies f1 and f2 vary oppositely with a change in acceleration The acceleration is determined in accordance with the relation a=A1 f1 -A2 f3 +A0 or a=A1 f1 2 -A2 f2 2 +A0 where a is the acceleration and A1, A2 and A0 are calibration coefficients

An electromagnetic accelerator

Abstract: An electromagnetic accelerator employing a capacitor bank is described, which can be used to accelerate masses up to 1 g to velocities between 10 m s-1 and 300 m s-1. The theoretical model is compared with experimental results and photographs of the acceleration process are shown. The results indicate that the electromagnetic accelerator is a highly reliable device; the operation is reproducible. It can be used to accelerate all kinds of mases (dust, liquids, organic material, etc.) in any environment (vacuum, atmospheric pressure, high pressure, or liquids).

Fiber-optic acceleration sensor based on the photoelastic effect

Abstract: A novel type of fiber-optic acceleration sensor was constructed of a photoelastic substance such as isotropic epoxy resin, DAP (diallylphthalate polymer), or LiNbO3 single crystal. By a weight placed on the upper surface of the rectangular rod of photoelastic material, stress-induced birefringence is brought about in response to vibrational acceleration. With this sensor, acceleration from 10−3 to 30 G was accurately measured in the frequency range from dc to 3 kHz.

Fuel control for controlling helicopter rotor/turbine acceleration

Abstract: The difference in the speed (54, 56) of a helicopter gas engine (20), free turbine (40) from a reference speed (62, 64) generates (80) a desired acceleration signal (81). The difference (82) in actual turbine acceleration (84, 86) from desired acceleration is integrated (100) to provide an engine fuel command signal (67-73) whenever (88) the speed error signal exceeds (90) a predetermined threshold magnitude.

Soft X-Ray Driven Ablation and Its Positive Use for a New Efficient Acceleration

Abstract: The ablation process driven by soft X-ray is investigated by one-dimensional hydrodynamic code coupled with LTE, average ion model and multi-group radiation package. The following two major results are obtained: (1) the ablation pressure and mass ablation rate scalings, and (2) a new acceleration scheme which positively uses the unique property of soft X-ray transport.

Data track searching device

Abstract: A data track searching device capable of switching between two modes; one being the rough searching mode in which a transducer is displaced at a high velocity to a desired track and the other being the fine searching mode which follows the rough searching mode and in which the transducer is displaced at a relative low velocity and positioned over the proper or desired track. The operating point of a tracking element is shifted or deviated as a result of the high-velocity displacement of the transducer in the rough searching mode so that stable searching cannot be ensured. According to the present invention, therefore, the acceleration of the transducer in the rough searching mode is detected and a signal representative of the thus detected acceleration is applied to the tracking element so that the shift or deviation of the operating point of the tracking element can substantially made nil.

Motion control system with adaptive deceleration

Abstract: A microprocessor-based motor control system operates the rapid advance motor on a slide transfer machine to carry out rapid traverse motions in minimal time A velocity profile is stored during the acceleration portion of the move and this data is employed to determine when deceleration should begin and to control velocity during the deceleration portion of the move A position feedback circuit having programmable resolution is employed to develop the velocity profile

Further Studies on the Acceleration Sensitivity of Quartz Resonators

Abstract: : Further studies on the acceleration sensitivity of quartz resonators have been performed. These studies have included conventional AT, strip AT, GT, IT, AK, and SC-cut resonators. No significant differences have been found in the best achievable acceleration sensitivities of the various cuts. The dependence of the acceleration sensitivity of 4-point mounted SC-cut resonators on design parameters and operating conditions has been investigated. These parameters include blank geometry, angle of cut, mounting orientation, temperature, drive current, and overtone. No significant systematic variation of acceleration sensitivity has been found as a function of any of these parameters except overtone for the same resonator.

Seismic design response by an alternative SRSS rule

Abstract: The square root of the sum of the squares (SRSS) procedure and its modified forms are often used to obtain seismic design response. The design inputs for such procedures are usually defined in terms of pseudo velocity or acceleration response spectra. Erroneous results have been obtained with these existing SRSS procedures, especially in the calculation of responses where high frequency effects dominate. Here an alternative SRSS procedure is developed using the so-called mode acceleration approach of structural dynamics. The design input in this procedure is defined in terms of relative acceleration and relative velocity spectra. The relative spectra can be related to pseudo spectra. For a given number of modes to be included in the analysis the new SRSS rule proposed here will reduce the error due to the so-called ‘missing mass’ effect and predict a more accurate response value than the rules which use pseudo spectra as input, for systems either with or without dominant high frequency mode effects.