Showing papers on "Transient (oscillation) published in 1974"

On the accuracy of finite element solutions to the transient heat-conduction equation

Abstract: This paper discusses three numerical integration schemes connected with a finite element solution to the transient heat-conduction equation. The main emphasis is on the achievable accuracy. A simple recurrence relation derived from the Galerkin process is suggested for the treatment of fast-varying boundary conditions as being significantly better than the usual Crank-Nicholson scheme in matters of short-time accuracy.

Transient electric field and space‐charge behavior for unipolar ion conduction

Abstract: New analysis is presented using a unipolar ion‐mobility conduction model in planar geometry which solves for the transient behavior of the bulk electric field and space‐charge distributions as a function of time and space, as well as the resulting time dependence of the terminal quantities of voltage and current The charge‐conservation quasilinear partial differential equation is solved using Lagrange's method with the method of characteristics The analysis is generalized to handle any physically allowed initial and boundary conditions for any type of applied excitation Special cases are examined of the turn‐on transient with the application of a step voltage or current, contrasting the behavior between space‐charge‐limited conditions where the emitter electric field is zero to those where the emitter field is nonzero Much of the analysis yields closed‐form expressions

Transient emission, off‐resonant transient absorption, and Fourier transform microwave spectroscopy

Abstract: Transient emission and off‐resonant absorption methods are used to measure T2 in different M states of several (J,K) transitions in 15NH3 and in the J=1→2, M=0,±1 transitions in OCS. No M dependence in T2 was observed. Transient emission signals were recorded and Fourier transformed in several (J,K) 15NH3 transitions, some of which were doublets. Faithful spectra are obtained, and the time domain experiments hold some advantage in high‐resolution microwave spectroscopy over the normal steady state technique.

Inrush current limit circuit with reset response to lowered input voltage

Abstract: A converter circuit includes an inrush current limit circuit to limit the initial transient surge of inrush current to a power supply upon the initial application of voltage to the power supply input. After the initial start-up transient inrush current surge, the inrush current limit circuit is switched out of the input signal path to reduce power dissipation during normal steady state operation of the circuit. If the input voltage magnitude decreases significantly at any time, the inrush current limit circuit is reset to limit any further current surges.

Application of the small-signal transmission line equivalent circuit model to the a.c., d.c. and transient analysis of semiconductor devices

Abstract: It is shown that the use of the small signal transmission line equivalent circuit model is not restricted solely to the small signal a.c. analysis of semiconductor devices. Simple algorithms are described which allow it to be used to compute the d.c. and the large signal transient properties of semiconductor devices to any desired precision. The approach is demonstrated by computing the a.c., d.c. and transient properties of an N + P junction diode.

Transient absorption and emission and the measurement of T1 and T2 in the J O→1 rotational transition in OCS

Abstract: Stark switching microwave experiments on transient absorption and transient emission that allow the measurement of T1 and T2 in the J = 0→1 transition in OCS are described. The results from the transient absorption experiments are T1 = (26±4) × 10−6 sec · mtorr and T2 = (33±7) × 10−6 sec · mtorr. The results of the transient emission experiments give T2 = (31±3) × 10−6 sec · mtorr. Thus, T1 = T2 within the experimental uncertainties. We also demonstrate the effects of π/2 and π pulses by using Stark switching.

A note on the first two moments of times in transient states in a semi-Markov process

Abstract: This paper derives results for computing the first two moments of times in transient states and times to absorption in a transient semi-Markov process. An illustrative example is presented at the end. SEMI-MARKOV PROCESS; FIRST TWO MOMENTS; TIMES IN TRANSIENT STATES

Coherency based dynamic equivalents for transient stability studies

Abstract: The development of a coherency-based technique to form dynamic equivalents for use in transient stability studies is summarized. The resulting simplification in representing areas some distance from a disturbance will reduce the time and storage requirements necessary for transient stability studies. Potential areas of application are in planning and in operations where computational savings in transient stability studies are important. The four areas of development discussed include: techniques to determine coherent areas; a coherency-based network reduction technique; aggregation of dynamic elements--machines, exciters and prime movers; and methods of updating the equivalents during daily load fluctuations. Examples being used to test the dynamic equivalencing techniques and results obtained in preliminary studies are described.

Transfer switch and transient eliminator system and method

Abstract: A method and apparatus is disclosed for transferring an electrical load to an inverter from a utility A.C. power source without causing transient changes in the voltage and current fed to the load when such transfer is effected.

Audible alarm device

Abstract: A piezoelectric transducer is utilized in conjunction with a tone generator, a pulsator means, and a transient protection means to produce an audible alarm in response to various input electrical signals.

Motor protection device

Abstract: Electrical and electronic circuitry offering protection to motors, compressors and the like, from conditions of low energizing voltage or momentary voltage interruptions resulting in excessive mechanical load (locked rotor). When the undesirable condition is present, an internal relay prevents the equipment from being energized - transient conditions being allowed for by means of suitable time delay circuitry. The protection device provides significant improvement in safety and economy by preventing equipment from burning up.

A Method of Improving Transient Stability by Bang-Bang Control of Tie-Line Reactance

Abstract: This paper presents a new approach to the problem of improvement of transient stability of a power system by means of optimal control of transients and is in continuation of the work reported in a previous paper.1 Essentially the system state is transferred from that at the beginning of the transient to a post-transient steady state in a nonoscillatory manner by means of a bang-bang control, thereby contributing significantly to the improvement of transient stability. A power system model with two interconnecting tie-lines is considered. It is shown that the control process may be implemented with two intermittent duty series capacitors or a capacitor and a reactor. Results of the synthesis of the optimal controllers and evaluation of realistic indices of performance are presented along with practical considerations.

Far-field transient backscattering by ice spheres

Abstract: Approximate far-field, backscattering transient responses are shown for three ice-sphere sizes. Signal ringing continues for a longer time, but the effective transient decay time is less than a space-equivalent time of six diameters. Glory, axial, and stationary rays in combination with an internal surface wave of one cut are the principal contributors to the scattering by ice, but the dipole must be included for small electrical sizes.

Short-circuit protection circuit

Abstract: A short-circuit protection circuit for use in an arrangement in which a load is connected to a source of electrical power by way of switch, operates to open the switch only when a true short circuit condition exists, the circuit discrminating between a true short circuit condition and short duration high current surges caused, for example, by bouncing of the contacts of the switch or transient characteristics of the load

Predicting an equilibrium state value from transient state data

Abstract: Values of many biological, chemical and physical factors approach their respective equilibrium state values when constant reactive potentials are applied to these factors. These equilibrium state values are frequently required for analyzing their transient processes. Mathematical analyses of available data on transient state values of various factors revealed that most of these values could be estimated by using an exponential formula, A procedure was developed for the reliable prediction of equilibrium values through the proper application of the formula to transient state values. For this development, it was assumed that transient state values were given at equal time intervals. According to a number of experimental computations, errors of equilibrium state values predicted by the developed procedure were less than 5%. The procedure estimated equilibrium values with less than 50% the time effort required by conventional procedures and will be of great use for reliably predicting equilibrium state values, especially when a factor converges very slowly to its equilibrium condition.

Response of a quadrupolar spin system in zero applied field to a long, off‐resonant radio‐frequency pulse

Abstract: The response of a system of nuclear spins I=3/2 experiencing electric quadrupole couplings in zero applied field to a long, off‐resonant radio‐frequency pulse is investigated using simple time‐dependent perturbation theory. It is found that the height of the transient following such a pulse varies with the distance from exact resonance, Δω, in the same manner as previously found for the case of a purely magnetically coupled spin system in high field, in which the rf pulse is of sufficient duration to allow the magnetization to become aligned along the effective field when viewed from the rotating frame. We find, in addition, that if a short resonant ``sampling'' pulse is applied after the transient from the long pulse has died down, the maximum height of the transient following this second pulse varies with Δω in the same manner as the response of the Zeeman system to this pulse sequence. Furthermore, with this two‐pulse sequence, an echo‐type transient is predicted to appear at a time 2τ, where τ is the ...

Transient Behaviour of Damped Capacitive Voltage Dividers of Some Million Volts

Abstract: This paper describes the basic design of two types of damped capacitive voltage dividers. The impedance characteristic of the voltage divider and of the complete measuring circuit is discussed. The actual response characteristics of damped capacitive voltage dividers are surveyed and the possible application evaluated.

Power system transient stability regions : transient stability limits involving saliency and the optimized Szego's Liapunov function

Abstract: The optimized Szego's Liapunov function has been formulated for a single-machine system connected to a large power system taking into account saliency and the effect of non-linear damping, A computer-oriented approach using Szego's Liapunov function has been outlined for the determination of transient stability limits. The specific advantages of the present method over those of Zubov and Popov (Yu and Vongsuriya 1967, Chang and Davies 1972) have been clearly brought out.

High voltage transient protection means as for piezoelectric transducers

Abstract: This invention refers to a means for providing high voltage transient protection to piezoelectric wafers used in ultrasonic converters. The means is particularly useful in converters used for ultrasonic insertion applications.