Smooth Waveform Research Articles

Studies on the Operation Behavior of Differential Protection During a Loaded Transformer Energization

Recently, several cases of maloperation of the differential protection with second harmonic blocking due to transformer switching on with load have been reported. Quite a few maloperation occurred at the nonrestraint region of percentage restraint plane. The previous theory cannot be utilized directly to analyze this phenomenon. Therefore, a novel model for analyzing the transient course of the loaded transformer energization, together with the CT model involving the magnetic hysteresis effect, is proposed to explain above-mentioned category of maloperation. It is disclosed that the magnetic linkage of CT core can be pushed into the region nearby the saturation point by the aperiodic component of through inrush. When the aperiodic component decays rapidly, the magnetic linkage formed by the periodic component of primary current with low amplitude is not enough to pull the operating point of the magnetic linkage back to the linear region. This phenomenon is named as CT local transient saturation, which results in the big measuring angle error and relative smooth waveform. In this case, the transformer differential protection using second harmonic blocking inevitably maloperates. This point of view is verified with the simulation tests.

２層構造の自己組織化複合ボンド磁石の作製

The magnetic properties of radially-anisotropic ring-shaped magnets deteriorate when their diameter decreases, so the miniaturization of their magnet motors becomes difficult. In order to overcome this difficulty, we developed a self-organization technique of binder for anisotropic rare-earth bonded-magnets. By using this technique, we controlled the flexibility of perpendicularly-anisotropic rigid sheet-shaped magnets (approximately 1 mm in thickness), transformed them into various specific shapes, and succeeded in preparing radially-anisotropic ring-shaped magnets. In this contribution, we report a new technique which enables us to prepare an composite bonded magnet with a two-layered structure. In the magnet prepared by the developed technique, the direction of easy magnetization varies from the circumferential direction to the radial direction without deterioration of the degree of alignment. Consequently, the multi-polar magnetized magnets observed a smooth flux waveform and the initial irreversible flux loss reduction compared with that of conventional radially anisotropic magnets.

Oscillator providing waveform having dynamically continuously variable waveshape

An oscillator for digital music synthesis that provides a smooth waveform that is rich in harmonic content and whose shape is continuously and dynamically variable over a wide range of harmonically rich shapes. The oscillator is efficient in that it generates the shapes in a time consonant with sampling rates commonly used in music synthesis, and is generally free of discontinuities which would otherwise create audible alias components on subsequent signal processing.

Investigation and verification of a cascade double –CL current source resonant inverter

The current source resonant inverter (CSRI) is at the heart of many systems and equipment (e.g. uninterruptible power supply (UPS) and high-frequency annealing (HFA) equipment). Many topologies shown in open literature are series resonant converters (SRC) and parallel resonant converters (PRC) that consist of two or three energy storage elements. However, they have a number of limitations. These limitations of two- or/and three- element resonant topologies can be overcome by adding a fourth energy storage element. This paper introduces a cascade double /spl Gamma/-CL CSRI, which has very smooth waveforms for output voltage and current, and a very low total harmonic distortion (THD) value. It effectively reduces the power losses and largely increases the power transfer efficiency. Simulation and testing results verified the authors' design and analysis.

Spatiotemporal properties of an evoked population activity in rat sensory cortical slices.

We have examined the spatiotemporal properties of ensemble activity, an evoked all-or-none polysynaptic activity in rat neocortical slices. Ensemble activity occurred in cortical slices bathed in normal artificial cerebrospinal fluid (ACSF) and was evoked by a single electrical shock either to the white matter or directly to the cortical tissue. This activity was seen in slices of somatosensory and auditory cortices; in other cortical areas we have not been able to evoke it. The activity developed 10 to 250 ms poststimulus and lasted 280 +/- 120 ms in local field potential (LFP) recordings. Voltage-sensitive dye imaging showed that this activity was an area of activation 0.8 +/- 0.4 mm wide that propagated slowly (11.4 +/- 6.2 mm/s, n = 60, 6 animals) in the horizontal direction. Due to this propagation, the actual duration in the whole tissue may be longer (approximately 400 ms) than that recorded by a single LFP electrode. Ensemble activity produced a low-amplitude optical signal (7-14% of the interictal-like spikes in the same tissue), suggesting a moderate net depolarization of the population. These were very different from hyperexcitable (epileptiform) events in the same tissue that had about 10 times the optical signal amplitude and propagated at 125 +/- 24 mm/s (n = 21, 6 animals). On a global spatial scale (approximately 0.8 mm wide in layers II-III) ensemble activity had a smooth waveform in voltage-sensitive dye signals (population transmembrane potential). On a local scale, field potential recordings showed large fluctuations with complex oscillations and substantial trial-to-trial variation. This suggests that oscillations in cortical circuits occurred only in small clusters of correlated neurons. Ensemble activity was sensitive to the excitation-inhibition balance of the local network. Antagonists of N-methyl-D-aspartate, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, and GABAa receptors, and muscarinic agonists and other modest manipulations such as increasing bath concentration of Mg(2+) to 2.5-4 mM (normally at 2 mM), or K(+) to 5-7 mM (normally 3 mM), all significantly reduced the probability of evoking the activity. The metabotropic glutamate receptor agonist, aminocyclopentane-1,3-dicarboxylic acid, blocked the activity at a low concentration (10-15 microM), while the antagonist (R,S)-alpha-methyl-4-carboxyphenylglycine had no effect even at high concentration (240 microM). Our data suggest that locally organized neuronal clusters may play a role in the organization of oscillatory activities in the gamma band and may participate in cortical integration/amplification occurring on a scale of approximately 1 mm x 300 ms.

Use of a genetic algorithm for the analysis of eye movements from the linear vestibulo-ocular reflex.

It is common in vestibular and oculomotor testing to use a single-frequency (sine) or combination of frequencies [sum-of-sines (SOS)] stimulus for head or target motion. The resulting eye movements typically contain a smooth tracking component, which follows the stimulus, in which are interspersed rapid eye movements (saccades or fast phases). The parameters of the smooth tracking--the amplitude and phase of each component frequency--are of interest; many methods have been devised that attempt to identify and remove the fast eye movements from the smooth. We describe a new approach to this problem, tailored to both single-frequency and sum-of-sines stimulation of the human linear vestibulo-ocular reflex. An approximate derivative is used to identify fast movements, which are then omitted from further analysis. The remaining points form a series of smooth tracking segments. A genetic algorithm is used to fit these segments together to form a smooth (but disconnected) wave form, by iteratively removing biases due to the missing fast phases. A genetic algorithm is an iterative optimization procedure; it provides a basis for extending this approach to more complex stimulus-response situations. In the SOS case, the genetic algorithm estimates the amplitude and phase values of the component frequencies as well as removing biases.

An Iterative Learning-Based Modulation Scheme for Torque Control in Switched Reluctance Motors

This paper deals with an iterative learning approach for modulating the desired torque profile so as to obtain ripple-free torque in switched reluctance motors. Because of the highly nonlinear relation between torque, current, and rotor position for this motor, it is not possible to obtain a closed-form mathematical expression for current as a function of torque and rotor position. Thus, the current waveforms are conventionally computed by using the linear torque model of the motor, and it is well known that such a scheme results in high torque ripple. In this paper, a novel method is proposed to minimize the ripple. In this new scheme, the current is still computed using the linear torque model, but the value of the torque used for this is not the desired (specified) torque, but rather a modulated-desired torque that is obtained by repeated corrections to the desired torque from iteration to iteration. The conventional rectangular pulse profile is taken as the initial current waveform. The method requires much less a priori knowledge of the magnetic characteristics of the motor. The algorithms have been formulated for both one-phase-on and two-phase-on schemes, for a four-phase switched reluctance motor, in the light of the principles behind iterative learning. Based on the observations from the simulation results of these schemes, a modified scheme has been proposed by incorporating a suitable commutation process, often called torque sharing functions, in order to generate reasonably smooth current waveforms for the ease of tracking by the stator circuit of the motor. The performances of all the proposed schemes have been verified by computer simulation.

A multiband excited waveform-interpolated 2.35-kbps speech codec for bandlimited channels

Following a brief portrayal of the activities in 2.4-kbps speech coding, a wavelet-based pitch detector is invoked, which reduces the complexity of conventional autocorrelation-based pitch detectors, while ensuring smooth pitch trajectory evolution. This scheme is incorporated in a waveform-interpolated codec, which uses voiced-unvoiced (V/U) classification, and instead of simple Dirac pulses, an unconventional zinc basis function excitation is employed for modeling the voiced excitation. The required zinc-function parameters are determined in an analysis-by-synthesis loop, and for the sake of smooth waveform evolution and reduced complexity, a focused search strategy and a few further suboptimum restrictions are imposed without seriously affecting the speech quality. This baseline codec operates at a rate of 1.9 kbps, but it suffers from slight buzziness during the periods of excessive voicing. This impediment is then mitigated by invoking a mixed V/U multiband excitation, which slightly increases the bit rate to 2.35 kbps due to the transmission of the 3-b voicing strength code in each of the three excitation bands.

A method for activating neurons using endogenous synaptic waveforms

Neuronal input-output functions are traditionally studied using rectangular or ramp waveforms of injected current. These waveforms are easy to produce and responses to them easy to quantify; thus they have been central to our understanding of the roles that membrane properties play in controlling repetitive firing. However, since smooth rectangular step and ramp waveforms lack the dynamic features of endogenous synaptic input, their use has the potential to underemphasize the importance of input patterns in controlling physiological patterns of neuronal output. To activate neurons with current waveforms that replicate natural synaptic input, we developed a method for acquiring, digitally manipulating and reinjecting endogenous synaptic currents. We demonstrate, by applying this technique to phrenic motoneurons (PMNs) in rhythmically-active in vitro preparations from neonatal rats, that stimulation of neurons with endogenous current waveforms produces responses that mimic those produced by spontaneous synaptic inputs. Acquired waveforms can be reinjected repeatedly to produce consistent responses, and can also be amplified or filtered prior to reinjection to yield a range of information including standard descriptors of firing behavior such as frequency/current plots. This technique provides a valuable tool for analysing characteristics of the synaptic waveform important in generating neuronal output and how synaptic factors interact with membrane properties to control repetitive firing.

Application of iterative learning for constant torque control of switched reluctance motors

Abstract The paper deals with the investigations on an iterative learning approach to determine the desired current waveforms for switched reluctance motors, which give rise to ripple-free torque. The current waveforms are generated by repeated corrections from iteration to iteration starting from the conventional rectangular pulse profile as the initial waveform. The scheme requires much less a priori knowledge of the magnetic characteristics of the motor. The algorithms have been formulated for both one-phase-on and two-phase-on schemes, for a four-phase switched reluctance motor, in the light of the principles behind iterative learning. Based on the observations from the test results of these schemes, a modified scheme has been proposed by incorporating a suitable commutation process, often called as torque sharing functions, in order to generate reasonably smooth current waveforms for the ease of tracking by the stator circuit of the motor. The performances of all the proposed schemes have been verified by computer simulation.

Determination of current waveforms for torque ripple minimisation in switched reluctance motors using iterative learning: an investigation

The paper deals with the investigations on an iterative learning approach to determine the desired current waveforms for switched reluctance motors, which give rise to ripple-free torque. The current waveforms are generated by repeated corrections from iteration to iteration starting from the conventional rectangular pulse profile as the initial waveform. The scheme requires much less a priori knowledge of the magnetic characteristics of the motor. The algorithms have been formulated for both one-phase-on and two-phase-on schemes, for a four-phase switched reluctance motor, in the light of the principles behind iterative learning. Based on the observations from the simulation results of these schemes, a modified scheme has been proposed by incorporating a suitable commutation process, often called torque sharing functions, in order to generate reasonably smooth current waveforms for the ease of tracking by the stator circuit of the motor. The performances of all the proposed schemes have been verified by computer simulation.

Saccadic Ping-Pong Gaze

Ping-pong gaze (PPG), or short-cycle periodic alternating gaze, consists of horizontal conjugate ocular deviations alternating every few seconds. This alternating gaze has been described as appearing to be smooth. However, our electrooculographic study of four consecutive unconscious patients with PPG showed smooth waveforms in one patient but saccadic cog-wheeling in three patients. In one of the three patients with saccadic PPG, a transition from smooth to saccadic waveforms was noted with clinical improvement. Whereas the patient with smooth PPG died immediately, the patients with saccadic PPG survived in a persistent vegetative state. These findings suggest that saccadic PPG is a clinical variant of PPG in patients in a lighter state of consciousness, possibly related to less extensive brain damage.

Thermodynamic equivalence of steady-state shocks and smooth waves in general media; Applications to elastic-plastic shocks and dynamic fracture

By comparing the First Law of thermodynamics in its shock wave form to its smooth wave form, and applying standard continuum mechanical conservation laws and geometrical compatibility, we prove for arbitrary media that a shock wave which propagates without rotating under steady-state conditions is thermodynamically identical to a suitably-chosen steadily propagating smooth wave (and that this is not so in general for nonsteady shocks). This legitimizes the derivation of restrictions on steady-state shock waves by the analysis of suitably-chosen steady smooth waves in purely mechanical material models. Doing so for a broad class of rate-independent elastic-plastic materials rigorously corroborates several recentlypublished shock restrictions whose derivations involved some (now validated) heuristic arguments, and substantially generalizes the material class for which these restrictions apply. Thus, e.g. within smalldisplacement-gradient theory, stress jumps are ruled out across steadily propagating shock waves in quasistatic deformations of any nonsoftening material satisfying plastic normality and positive-definiteness of the elastic modulus tensor (removing the previous limitation of this result to materials that satisfy the global maximum plastic work inequality and whose current yield locus always incorporates all prior yield loci). We also confirm that steady-state shock waves in dynamic anti-plane strain or plane strain deformations cannot exist except at elastic wave speeds for nonhardening materials in the same broad constitutive class unless the yield surface contains a linear segment. Application of these results to steady-state dynamic subsonic plane strain crack growth in elastic-ideally plastic Prandtl-Reuss-Mises material proves that this problem's solution must be shock-free. This implies that certain solutions containing strong discontinuity surfaces, obtained in a recently-published numerical finite element study of this dynamic crack growth problem, are not physically realizable. The conclusion is that either a more robust numerical procedure is necessary which incorporates the thermodynamics-mandated shock restrictions derived here, or that steadystate subsonic dynamic plane-strain elastic-plastic crack growth is not possible in this material model (and potentially not in nature for materials exhibiting plastic normality, purely nonlinear yield surfaces and no hardening).

Voltage and current characteristics of pulsed hollow cathode discharges in hydrogen

Volt-ampere characteristics of a hollow-cathode, hollow-anode discharge in hydrogen were measured by using a very fast di/dt probe. The large bandwidth of the probe enabled us to observe fast oscillations occurring at the onset of the current pulse and also at the moment of its quenching. Three different modes of operation are observed, the first with smooth voltage and current waveforms. The second mode occurs for voltages higher than 1500 V and is characterized by strong oscillations and the occurrence of current quenching. The third, mode occurs with a sharp transition and in it the current rises more rapidly to a much higher maximum value, while the oscillations are less pronounced. This mode has identical characteristics with the superdense glow mode of pseudospark discharges. At the point of transition a sudden change in the frequency of oscillations, of the impedance, and of the maximum transmitted power occur. Current quenching is observed in the second and in the third mode. The development of the superdense glow changes the character of the waveforms and current quenching while the mechanism leading to the superdense glow may be associated with the available voltage.

Electronic sound processing system

An electronic sound processing system comprises a sound waveform looping apparatus which cuts out a portion of an input sound waveform and conducts a looping process for a predetermined cycle of the portion of the waveform. The sound waveform looping process comprises a discrete Fourier transformer for applying a discrete Fourier transform to the input sound waveform, a frequency band remover for removing a predetermined frequency band of the discrete Fourier transformed sound waveform, an inverse discrete Fourier transformer for applying an inverse discrete Fourier transform to the sound waveform from which the predetermined frequency band has been removed, and a looping processor for looping a predetermined cycle of the inverse discrete Fourier transformed sound waveform. By executing the sound waveform looping process, the electronic sound processing system can obtain smooth looped waveforms with easy processes and simple equipment.

Scalar gravitation: A laboratory for numerical relativity. II. Disks.

While not a correct physical theory, relativistic scalar gravitation provides a simple test site for developing many of the tools of numerical relativity. Using this theory, we have built a mean-field particle simulation scheme to study the dynamical behavior of collisionless disks. Disks are one-dimensional matter sources of two-dimensional gravitational fields. One-dimensional disk sources can be evolved without excessive computational resources and yet they are able to generate nonspherical gravitational waves. We find that we are able to calculate smooth and accurate wave forms from time-varying disks, despite the stochastic representation of the matter source terms caused by sampling with a finite number of particles. A similar scheme should provide accurate wave forms in general relativity, provided sufficient computer resources are used.

Scalar gravitation: A laboratory for numerical relativity. III. Axisymmetry.

We construct a two-dimensional axisymmetric mean-field particle simulation scheme that solves the equations of relativistic scalar gravitation coupled to collisionless matter. Although scalar gravitation theory disagrees with experiment, it is useful as a testing ground for numerical methods used to solve the equations of general relativity, particularly in the generation of gravitational waves. We discuss methods for extracting the gravitational wave amplitude from the field variables, as well as methods for imposing an accurate outgoing-wave boundary condition on the scalar field at a finite radius. We find that for continuous matter distributions, our code is able to calculate smooth and accurate gravitational wave forms, despite the stochastic representation of the matter source terms caused by sampling with a finite number of particles. A similar scheme should provide accurate wave forms in general relativity, provided sufficient computer resources are used.

Influence of loading pulse duration on dynamic load transfer in a simulated granular medium

An experimental and numerical investigation was conducted to study the dynamic response of granular media when subjected to impact loadings with different periods or wavelengths. The granular medium was simulated by a one-dimensional assembly of circular disks arranged in a straight single chain. In the experimental study, the dynamic loading was produced using projectile impact from a gas gun onto one end of the granular assembly, and the measured wave signal was collected using strain gages. The numerical simulations were conducted using the distinct element method. It was found from the experiments and numerical simulations that input waves with a short period (τ ≈ 90 μs) will propagate in this granular medium with little waveform change under steady amplitude attenuation ; whereas longer waves (τ $ ̆ 200 μs) will propagate with significant waveform dispersion. For these longer wavelength signals, the smooth waveform will undergo separation into a series of short oscillatory signals, and this rearrangement of energy allows a portion of the transmitted signal to increase in amplitude during the initial phases of propagation. Thus the granular medium acts as a nonlinear wave guide, and local microstructure and contact nonlinearity will allow input signals of sufficiently long wavelength to excite resonant sub-units of the medium to produce this observed ringing separation. Following a modeling scheme originally proposed by Nesterenko [J. Appl. Mech. Tech. Phys. 5,733 (1983)], a nonlinear wave equation model was developed which is related to soliton dynamics and leads to travelling wave solutions of specific wavelength found in our experimental and numerical studies.

Geometrical and numerical considerations in computing advanced-propeller noise

A previously developed technique for numerically solving the acoustic analogy equation for rotating surfaces with supersonic regions results in smooth pressure-time waveforms. The method appears to provide results superior to those of other schemes because it eliminates erratic in the computed waveforms and deals only with nonsingular integrals. This article discusses the application of the method to propeller-type rotor blades. Several different sweep geometries are considered, and presented results show the effect of blade shape on the noise produced and on the numerical procedure for computing that noise. Computed waveforms exhibit expected behavior, deduced from analysis of the retarded blade shapes (acoustic planforms) and the critical points along the blade edges where the Mach number in the direction of the observer equals one.

Scalar gravitation: A laboratory for numerical relativity.

While not a correct physical theory, relativistic scalar gravitation provides a simple test site for developing many of the tools of numerical relativity. In contrast with general relativity, scalar gravitation allows gravitational waves to be generated in spherical symmetry. Hence one needs only one spatial dimension to try out methods of calculating wave emission and propagation. Using this theory, we have built a mean-field particle simulation scheme to study the dynamical behavior of collisionless matter in spherical symmetry. We find that we are able to calculate smooth and accurate wave forms, despite the stochastic representation of the matter source terms caused by sampling with a finite number of particles. A similar scheme should provide accurate wave forms in general relativity, provided sufficient computer resources are used.