Showing papers on "Transient (oscillation) published in 1972"

A computer algorithm to determine the steady-state response of nonlinear oscillators

Abstract: In the computer-aided analysis of nonlinear autonomous oscillators, the steady-state periodic response is usually found by integrating the system equations from some initial state until the transient response appears to be negligible. In lightly damped systems, convergence to the steady-state response is very slow, and this integration could extend over many periods making the computation costly. Also, one is never sure if a stable orbit exists or if the response might eventually decay to a singular point. If a stable orbit does exist, sometimes it is difficult to determine the period T of the orbit. In this paper, a Newton algorithm is defined which in the neighborhood of an orbit converges to it rapidly and gives a precise value for the period T of this oscillation. This algorithm represents a substantial step forward in the analysis of nonlinear systems. In addition, the algorithm meshes easily with most computer-aided circuit-analysis programs, and the initial iterates give information on the transient behavior of the circuit.

The Effect of Support Flexibility and Damping on the Synchronous Response of a Single-Mass Flexible Rotor

Abstract: Single mass flexible rotor in elastic bearings mounted on damped flexible supports, analyzing dynamic unbalance response and transient motions

Nature of the on-state in chalcogenide glass threshold switches

Abstract: By superimposing transient voltage pulses during the On -state of a threshold switching cycle, the transient voltage-current characteristic of the on -state filament has been determined for two types of switching systems, using different froms of graphite electrodes. Both systems employed ∼ 1 μm films of Te40As35Ge7Si18 as the active material. From the data, the lifetime of free charge carriers following cessation of the on -state can be inferred. Until the free carrier decay is complete the on -state can be re-established without any switching process. As the on -current approaches the minimum holding current, the maximum permissible interruption period approaches zero. It is concluded that the decay of non-equilibrium carriers in trapping centers follows the decay of free charge carriers until complete equilibrium is restored (after 1 μmsec approximately). It is shown that the transient on -state characteristics are dependent on the electrode material. The conclusions heavily reinforce electronic interpretations of threshold switching.

A finite element solution of coupled electrokinetic and hydrodynamic flow in porous media

Abstract: The finite element method is applied to the solution f seepage problems where both electrokinetic and hydrodynamic forces occur. The resulting system of coupled equations is used to solve both the steady state and transient conditions in a one-dimensional system and compared with the theoretical result. An analysis is then made of a more complex two-dimensional problem where the application of electro-osmosis may be used successfully to prevent piping.

Dynamic Energy Balance Studies for Simulation of Power-Frequency Transients

Abstract: Dynamic energy balance is a new technique for power system dynamic simulation. It requires about one tenth the computatioanl effort of a transient stability study yet gives similar results so far as frequency transients are concerned. Applications, methodology and comparison with a transient stability study are treated in this paper.

Circuit for protecting semiconductors against transient voltages

Abstract: A surge protector is connected in parallel across each of the line-side and load-side circuits, that on the line-side having a relatively high clipping voltage and relatively high energy handling capability, and that at the load-side having a lower clipping voltage and lower energy handling capability. An LCnetwork is connected between the surge protectors to slope off the incoming transient voltage so that the line-side protector initiates the clipping action before the load-side protector starts to clip the voltage. The line-side protector dissipates most of the transient energy and the load-side protector clips the voltage to the required level.

Josephson junctions with 1 μm dimensions and with picosecond switching times

Abstract: Josephson junctions with 1 × 3 μm dimensions have no resonances. For a current density of about 1000 A/cm2, the risetime of the switching transient from zero to the gap voltage is below 38 ps.

Determination of Waterwheel Alternator Transient Reactances from Flux Plots

Abstract: In the transient analysis of salient pole alternators, the reactances X'd and X'q are assumed to be constants. In saturated machines, however, these reactances are functions of the pre-transient load of the alternator. For more exact analyses saturated reactances should be used. The expression of rotor quantities in stator terms, or vice versa, at nonlinear condition is explained. The operational impedances Xd(p), Xq(p) and the various time constants of alternators without amortisseur windings are developed from leakage reactance concepts. After a first approximation of the transient reactances is obtained from the operational impedances, a step-by-step correction procedure is used for finding the operationally dependent direct transient reactance. This is obtained from a simulated dynamical test. Only a few step-by-step corrections are necessary to yield good values for the transient reactances. Since there is a slight difference between Xq and X'q, the analysis will concentrate only to X'd. Notations not explained here are the same as in Concordia [1]. The analysis is applied to a General Electric alternator with nameplate data 82.5 MVA, 16.5 kV, wye-connected, 40 poles and 60 Hz, described in [2].

On the theory of transient electromagnetic sounding over a stratified earth

Abstract: Electromagnetic transient coupling between two small ungrounded loops is considered for the case where the earth is a two-layer conducting half-space. The formal solution for the impulse response is approximated with special attention to the initial stages of the time function. Various limiting cases are also considered. It is shown that the most convenient scheme for interpretation is when the two loops are raised above the earth's surface.

A transient solution for domain wall motion

Abstract: Approximate analytic solutions of transient wall motion in a bulk ferromagnetic material are obtained from the dynamic torque equations with a Gilbert damping term. These transient solutions reduce to previously obtained well-known solutions under steady-state velocity conditions.

Transient Phenomena of the Light‐Induced Memory in Amorphous Semiconductor Films

Abstract: Transient phenomena of write‐in and erasing processes of the light‐induced memory in Te81Ge15Sb2S2 films were observed by the transmission mode using a He–Cd laser. Crystallization was completed in 50 μsec under illumination, which supports the photon‐enhanced crystallization.

On the Determination of Minority Carrier Lifetime and Surface Recombination Velocity from the Transient Response of MOS Capacitors

Abstract: A method was developed to measure minority carrier lifetime and surface recombination velocity simultaneously. This method consists of measuring the transient C-V response of several MOS capacitors by application of a step voltage to gate electrodes. Experiment proved that this method was useful in evaluating Si slices.

Solution of transient groundwater flow problems by the finite element method

Abstract: The derivation of the basic equations of a finite element method for transient groundwater flow problems is simplified when the approximation of the time derivative by a finite difference equation is made before the introduction of the variational principle. Existing programs for steady state problems can easily be extended to the transient case in this way, and a stable numerical procedure can be obtained.

Transient oscillator analysis of a high‐pressure electrically excited CO laser

Abstract: A molecular kinetic model and self‐consistent oscillator analysis have been developed for electrically excited transient and steady‐state (CO, N2, He, Ar, …) laser systems. Theoretical calculations for a transient oscillator are compared with experimental data obtained from a high‐pressure electron‐beam‐stabilized long‐pulse transverse‐discharge CO device.

On calculating transient electromagnetic fields of a small current-carrying loop over a homogeneous earth

Abstract: The basic theory of airborne EM surveying, in the time domain, is considered. Rather than resorting to tediousdouble numerical integration, a more direct approach is adopted. This method, valid in the quasi-static regime, is illustrated for a homogeneous flat earth. The results exhibit a number of clear-cut features that are relevant to remote sensing. For example, a vertical co-axial loop system has a desirable transient response from the standpoint of yielding conductivity data without requiring accurate information on the height of the device above the ground.

A Dynamic Surge Arrester Model for Use in Power System Transient Studies

Abstract: The valve-type surge arrester with current-limiting gap has dynamic performance capabilities which provide improved protection against system transient overvoltages. This paper interprets these dynamic characteristics as revealed in laboratory tests and translates them to a set of differential equations which can be solved with the aid of a computer. Alternatively, the differential equations can serve as an important guide in developing an equivalent circuit, and hence a physical model for the arrester which might be found useful in direct analog studies. Comparison between laboratory test results and computer results establish the validity of the simulation. Extension of the approach to more general system voltage transient studies is contemplated.

Dynamic Aggregation and the Calculation of Transient Stability Incides

Abstract: A method of dynamic aggregation is introduced to define power system transient stability indices based on the previously used concepts of potential and kinetic energies. The indices are easier to compute and less conservative than those introduced by other authors. They reflect quantitatively the seriousness of the system instability threat created by actual or postulated faults. They are thus useful for purposes of on-line system security monitoring and interpretation of transient stability studies.

A General Technique for the Spectroscopy of Transient Absorbing Species

Abstract: A convenient routine method for the study of spectra of transient absorbing species produced by radiation is described. The specific example discussed in detail is an addition to the stroboscopic pulse radiolysis system to allow determination of the spectra of transient species after 30 psec or after several nanoseconds. New electronic circuits have been designed to increase the sensitivity and linearity of the detection system. The electronic systems have been carefully evaluated, and the over‐all performance of the system is shown by a sample spectrum of the hydrated electron.

Transient heat flow from a thin circular disk — small-time solution

Abstract: In a previous paper [1] an approximate analytical solution, useful for large times, was obtained for the transient heat flow from a thin circular disk held at constant temperature and immersed in an infinite medium. In the present work a first approximation has been found for the complementary \"small-time\" solution and the details of this solution examined. Some numerical calculations are included.

Lumped-circuit representation of Gunn diodes in domain mode

Abstract: It is shown that the lumped circuit that has been used to date to represent a Gunn diode with a steadily propagating domain cannot and does not properly account for the transient, and therefore, high-frequency behavior of a Gunn diode. We have derived the nodal equations that must be obeyed by any circuit that is to represent a Gunn diode with a steadily propagating domain under all conditions --small signal and large signal, sinusoidal steady state, and transient. The validity of the new circuit and the fact that the conventional circuit would give erroneous results under transient conditions have been checked by transient experiments on the computer simulated Gunn diode. It is also shown that the domain differential capacitance is approximately half of what is given by zero diffusion theory, a result first predicted by Kuru, Robson, and Kino, and the discrepency is accounted for by the nonzero width of the accumulation layer, and incomplete depletion in the depletion layer.