Traveling Wave Phenomena Research Articles

EEG simulation: variation of spectral envelope, pulse synchrony and approximately 40 Hz oscillation.

Macroscopic EEG travelling wave phenomena and cortical pulse synchronisation effects are related within a single simple simulation. Non-specific activation acts to control the transfer function of the simulated cortex, and thus determines the relative amplitude of macroscopic EEG waves generated by rhythmic inputs. When concurrent asynchronous excitatory inputs to separate, local, cortical sites are introduced, the simulation reproduces both gamma-band (40 Hz) electrocorticogram (ECoG) activity and synchronous oscillation of action potential pulse density at the separate sites. The gamma-band ECoG and pulse synchrony effects depend on different mechanisms: the former upon local excitatory/inhibitory interactions, and the latter on corticocortical interactions. The pattern of synchronous activity depends upon both structural and dynamic aspects of gain, and is sustained by linearised versions of the simulation's state equations. Dynamic properties of the simulation, which are independent of scale, describe both microscopic and macroscopic phenomena, all in accord with physiological findings.

ストロボ検査

The purpose of laryngostroboscopy is to observe the vibration of the vocal fold. The essential principle of human vocal fold vibration during phonation is the travelling wave phenomenon of the mucous membrane. This wave crest travels from the lower portion to the upper-lateral portion of the vocal fold continuously. Consequenly, both the so-called upper lip and the lower lip indicate the wave crest of the travelling wave.This travelling wave phenomenon was clearly observed by the newly developed digital subtraction X-ray stroboscopy.Furthermore, easy visualization and quantitative analysis of vibrations of the vocal fold synchronously with some voice-ralated signals (VRS) including the voice signal, EGG, subglottic pressure on laryngostroboscopy has become possible by the newly developed laryngostrobography.The observation of the travelling wave by conventional laryngostroboscopy was explained by the aforementioned method.

Autowaves and spatio-temporal chaos in CNNs. I. A tutorial

This paper presents a summary of the most commonly observed spatio-temporal phenomena in discrete cellular neural networks (CNNs) of dimension one and two. Among the phenomena discussed are traveling wave phenomena in chains and 2-D arrays, and spiral waves and target waves in both excitable and fluctuating media. Chua's circuit is used as the basic cell in the CNN arrays. Parameter values and initial conditions for the corresponding simulations are given so they can be reproduced with different simulators.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

デジタルサブトラクションX線ストロボスコピーによる声帯振動の解析

The main point of the X-ray laryngostroboscopy (X-ray stroboscopy) which was first developed. by Saito is that the trigger pulse for the strobo light of the laryngostroboscope is used as the external trigger for the pulse X-ray radiation of the pulse X-ray angiography system.The critical defect of the X-ray stroboscopy of human phonations from the frontal plane was that the vibratory image of the vocal cord was masked by the overlapped image of the cervical vertebrae.This defect was, first in the world, completely resolved by recent development of the digital subtraction X-ray stroboscopy. This is a combined system of the laryngostroboscope and the digital subtraction angiography system. Clear vibratory images of only the vibrating portion of human vocal cords in the frontal plane can be extracted by the digital subtraction of the image of the cervical vertebrae.The essential principle of the vibration of human vocal cords during phonation is the travelling wave phenomenon whose wave crest travells from the lower portion to the upper portion of the vocal cord continuously.

Modelling short packed and tray-type distillation columns for controller design

Parametric transfer-function matrix (T.F.M.) models are derived from the differential equations describing the variation of liquid and vapour compositions within symmetrical distillation columns separating binary mixtures. Both packed and tray-type columns are considered, the models developed having minimal order 6 and 4, respectively, (implying perfectly-stirred mixtures and minimum number of trays in each column section), so removing the complications introduced by spatial variations encountered in earlier studies by Edwards and Tabrizi [1] and Tabrizi [2] of longer columns.The T.F.M.'s obtained are again shown to be diagonal with the same choice of input and output vectors as were employed in the ”long“ column studies. Furthermore, the fundamental behavioural differences between packed and tray-type columns are again revealed using these low-order physical models as were demonstrated in the previous studies. In particular, the sign of the static gain of packed-columns, responding to total flow changes, is again shown to be parameter-sensitive and the sign of the total-flow gain at high-frequency is shown to be the reverse of that for tray-type columns, so again causing non-minimum-phase behaviour in packed-columns in some circumstances.Because of their behavioural and parametric similarities, it is proposed that the minimal-order models developed in this paper be used as a future basis for control system design studies for spatially-distributed and multi-tray columns in situations where travelling-wave phenomena are unimportant.The present paper has revealed a precise diagonal dynamic structure for symmetrical columns using the same inputs and outputs. This deduction accords well with the findings of previous authors based on part impirical by McMoran [3], Shinskey [4], and Stainthorp [5], approximate analytical by Edwards [6], or purely simulation methods Rosenbrock [7]. Near first-order-lag behaviour is also a feature common to the findings of these earlier investigations and precise derivation herein reported. This paper is confined essentially to model derivation while the predictions of the system behaviour and control system design for tray-type distilltion column is considered in separate papers Tabrizi and Edwards [8].

Modeling and Optimization of Traveling Wave Field Effect Transistors

This paper provides new insight on traveling wave phenomena, along the transverse direction, in field effect transistors. Specially designed structures are proposed, either in single gate form or in dual gate form, which allow overcoming inherent limitations due to gate losses and realizing on-chip wideband amplifiers. Demonstration of these capabilities is done using testing and modeling procedures based on distributed equivalent circuits.

Performance of the Pramod Johns scheme for UHS protection of EHV transmission lines under arcing fault conditions

The performance of the scheme of Pramod Agrawal (1989) for ultra-high-speed (UHS) protection of EHV transmission lines under arcing fault conditions is described. The arc with reignition effect is modeled, and a method for digital simulation of the superimposed arc voltage is discussed. Simulated tests have shown that the arc voltage has significant higher-frequency components. These tests also confirm that the arcing fault response repeats every half-cycle for a fault inception angle of the voltage from 0 to 90 degrees , which is a significant improvement over schemes based on traveling-wave phenomena which have been considered a failure for faults at 0 degrees C fault inception.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Digital Protection of EHV/UHV Transmission Line Based upon Travelling Wave Phenomena

ABSTRACT A challenging Job for the protection of EHV/UHV transmission lines is to have reliable, maintainable and quick acting relaying schemes. This paper presents a novel relaying scheme which possesses these features. The signal for the purpose of relay pick up uses the travelling waves of voltage and current which are produced after the fault in such long transmission lines having distributed parameters. Time domain as well as frequency domain methods are available for this purpose. The paper presents the transient fault analysis of a multinode power system network which employs the nodal formulation for frequency domain analysis. Finally, the paper concludes with the discussion of the results of the proposed digital relaying scheme based upon travelling wave phenomena.

A digitally-controlled, real-time, analog power-system simulator for closed-loop protective relaying testing

A power-system simulator is described that uses a control computer to configure an electronic analog model of a three-phase symmetrical power system and to set the model parameters. The model closely represents the dynamics of the real world up to 3 kHz. Precision high-power amplifiers convert the low-level analog signals to supply the protective relays under test. The design has been influenced by the key feature of closed-loop operation, with the relays functioning dynamically and in real time with the model. Nonlinearities are represented where significant, including the fault, transformer, arrester, and series-capacitor protection modules. The long-line transmission models represent the traveling-wave phenomena. Numerous system configurations can be selected. The data-acquisition system utilizes four digital computers, storing analog data at up to 25 kHz rate. The computers also analyze and manipulate the analog and event data and control a color plotter and printer. The emphasis of the discussion is on the analog models and the power amplifier designs. >

Parametric Transfer Functions for Packed Binary Distillation Columns

Abstract Using similar assumptions to those adopted in the companion paper on tray columns, a parametric transfer-function matrix is derived packed columns. For simpli-city, calculations are illustrated for a column that is symmetrical statically and dynamically i.e. having a vapour/liquid capacitance ratio c = 1.0 producing a diagonal T.F.M. between the sum and difference of output composition changes and the circulating and product take-off flow rates. The non diagonal T.F.M. is also presented for c≠ 1.0 and subsequent analysis and simulation show that the column behaviour is not greatly affected by changes in this parameter. Long packed columns are shown to produce novel nonminimum phase effects when twin product control is attempted, whereas serious travelling-wave phenomena can limit controller performance in short columns. The poss-ibility of zero separation-gain is also revealed. Computed inverse Nyquist loci are confirmed by analysis and by numerical simulation. The chief cause of discrepancy between tray and packed column behaviour stems from the continuous equilibrium assumption for theoretical trays.

A Travelling Wave-Based Fault Locator for Two- and Three-Terminal Networks

The high frequency components in fault waveforms present undesirable effects to most fault location algorithms and as a consequence filtering of postfault signals, to remove the high frequency transients, is essential for accurate fault location. A fault location algorithm that derives from travelling wave principles can cope with high frequency transients since these basically depend on travelling wave phenomena. The development of such an algorithm is the objective of this paper. Using the telegraph equations as a line model, voltage and current samples taken at one end of a line within the first 5 ms of fault inception are used to generate instantaneous voltage and current profiles for the rest of the transmission line. The voltage and current estimation is based on the solution of the equations of the line model by the method of characteristics. Criteria functions involving any of the square of the voltage, the square of the current, or the product of the two are applied for determination of the fault position. Fault position is given by the peak variation in tangent to the above basic functions. The algorithm finds application in fault location on two and three-terminal networks at both transmission and distribution levels.

A New Approach to E.H.V. Direction Comparisn Protection Using Digital Signal Processing Techniqles

Some problems concerning the performance of superimposed component directional relays are discussed, and it is shown that the basic directional criteria can be violated due to travelling wave phenomena or for fault occurrence approaching a voltage zero. A relay design is developed using digital signal processing techniques to overcome these problems. Tlhe complete relay is tested using a typical 40OkV transmission line application.

An Investigation Into the Dynamics and Control of a Liquid Heat Exchanger

Parametric transfer-function matrices are derived completely analytically for the symmetrically operated liquid heat exchanger to provide a basis for the assessment of approximate models obtained by joining low-and high frequency asymptotic behaviour. The complex form of transfer function, make them inconvenient, to use for simulation and conventional control system design. This paper therefore addresses itself mainly to the problem of finding simple and suitable analytical transfer function models to represent the heat exchanger dynamics.It is shown that, whereas multivariable first order models readily produce excellent approximation to the low and fairly high frequency behaviours of the heat exchanger, the travelling wave phenomena can nevertheless give rise to instability when high performance proportional plus integral controllers are employed. To overcome the problem of failure to predict the travelling-wave effect, the fundamental idea of matching high - and low frequency asymptotic behaviour is developed beyond the level of first order lag approximation to produce a single and multivariable lag-delay model structure for the process. Such structures are shown to be derivable with almost the same facility as the multivariable lag models and to reproduce the above mentioned resonance effects very closely indeed.The lag-delay model is verified by using it to design very satisfactory feed-forward controllers.

A rational approach to the traveling wave phenomenon

To aid comprehension of cochlear traveling waves, the present article will explain this complex phenomenon in terms of its underlying principles: (1) fluid mechanics, with particular reference to a tangible, analogous event, wave transformation on sloping beaches; (2) the central role of the cochlear stiffness gradient with respect to an energy exchange between travel speed and amplitude of cochlear waves, low pass filter action with distance, and impedance matching for the benefit of wave progression; (3) spatial domain and frequency domain considerations; (4) the solution to the classic dilemma between cochlear tuning and damping; and (5) the task of the helicotrema. I will not discuss the ultimate mechanical stimulation of cochlear hair cells that is mediated by shearing interactions between the tectorial membrane and the organ proper.

Narrow-band AP latencies in normal and recruiting human ears.

Derived narrow-band action potential latencies increase monotonically with decreasing central frequency, and can be interpreted as reflecting the traveling wave delay in the cochlea. It was found that, for recruiting human ears with average flat hearing losses around 40 dB, this accumulating latency increase was smaller than for normal ears. A comparison of 15 normal ears and 37 recruiting ears showed, however, that in only half of the recruiting ears this difference was significant. These recruiting ears were therefore divided in two groups based on the waveform of the narrow-band action potential AP, which correlated well with the subdivision according to latency. The findings have been explained on the basis that latency of the narrow-band APs is not determined solely by the mechanical traveling-wave delay, but also by the response time of the (second?) cochlear filter. When this filter broadens, one expects a decrease in its impulse response time. Since this impulse response time. Since this impulse response depends on the sum of the high- and low-frequency slope values of the cochlear filter, one expects only a latency decrease when the steep high-frequency slope also becomes more shallow. A support for the influence of the response times of the cochlear filter is found in the narrow-band AP latencies for restricted cochlear losses (e.g., in a 4-kHz noise dip). It appears that the latency in that area actually is shorter than for the higher central frequencies, a fact which cannot be explained solely on the basis of a traveling wave phenomenon.

Computation of sheath transient response in a single-point bonded cable section

The procedure that was adopted for the computation of traveling-wave phenomena in a slngle-point bonded buried cable section is described. Also included is the method of representing the non-linear cable covering protection units (CCPU's) and the results of computation are presented so as to illustrate the transient performance of the CCPU's when a typical three-phase single-point bonded cable section is faulted. The system model accounts for frequency-dependent parameters such as conductor, sheath and earth path skin-effects. The system is first defined in terms of its basic wave propagation characteristics, i.e., its unit step response functions in the time domain. For this purpose the modified Fourier transform method is applied and the transient solution to include specific system boundary conditions is completed in the time domain using convolution and Bergeron's method of characteristics. In this way the non-linear voltage-current relationships of the CCPU's can be taken into account much more readily and with comparatively greater efficiency than would be the case using the modified Fourier transform method throughout.

Transient analysis of underground power-transmission systems. System-model and wave-propagation characteristics

A mathematical model suitable for the analysis of travelling-wave phenomena in underground power-transmission systems is presented. The model is developed in terms of a generalised angular frequency, and may therefore be applied to the solution of steady-state problems or, by means of Fourier-transform techniques, to the solution of transient problems. The model takes into account skin effect in the conductors and in the soil. It is then shown how the system model may be analysed using multiconductor-transmission-line theory to give the transient response of the cable system. The wave-propagation characteristics are given for the natural modes of a certain cable system. These characteristics are examined with a view to their implications on transient phenomena.

Parallel EHV Untransposed Transmission Lines Studied for Overvoltages Due to Switching Surges AND Resonance

The proposed 345-kV transmission system interconnecting three Texas utility companies was studied for overvoltages due to switching surges-and resonance. The results of the study are presented and evaluation is made of the effects of nontransposition of the lines, close coupling of parallel lineson the same tower right- of-way, and the presence of compensating reactors under particular circuital configurations. The means for carrying out the study was provided by a general purpose analog computer equipped with peripheral transport time-delay components allowing the simulation of traveling wave phenomena.

Circuit Breaker and Transformer models for the Solution of Wavy Propagation in Distributed-Parameter Systems

Many models for the representation of transmission lines may be found in the present literature. The increasing use of digital techniques to solve the switching surge problem has prompted the development of models for other particular components of a power system. Specifically, the accurate representation of circuit breakers and power transformers is of vital importance in almost all switching surge studies. Presented here is a generalized direct-integration method that, while accurately reproducing the traveling-wave phenomena in transmission lines, advances a procedure for the simulation of circuit breakers (with insertion resistors) and power transformers. The results from a switching surge study on a representative three-phase system are discussed in detail.

The application of diakoptics and the escalator method to the solution of very large eigenvalue problems

AbstractThe eigenvalue method is well‐known as an aid to the solution of a wide range of engineering problems. In power system analysis it has relevance to travelling wave phenomena,1 sensitivity and dynamic stability in synchronous multimachine2 systems, critical speed calculation, vibration of structures and other related topics. The method of numerical solution of eigenvalues depends on the size and nature of the problem and often where large matrices are involved presents great difficulties.This paper describes in detail the application of the escalator method and diakoptics to large eigenvalue problems. The escalator method is a well‐established one which consists of a systematic way of escalating from a 2 × 2 matrix up to any desired order in steps of one row and column at a time. The diakoptical method reduces computer storage, calculation time and improves accuracy. This results in the more economical solution of large and complicated problems which cannot be conveniently solved by any orthodox method. The paper deals with problems of degeneracy and means of overcoming these by simple routine processes. It concludes by indicating the particular advantages of the method and its usefulness for a wide variety of general engineering problems.