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Topic: Signal velocity

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	Velocity Transducer/Installation
		Velocity pickups have been used as vibration transducers on rotating machines for a very long time, and they are still utilized for a variety of applications today.
		Velocity sensors are also susceptible to cross axis vibration, which if great enough may damage a velocity sensor.
		Where practical, a velocity sensor should be mounted in the vertical, horizontal, and axial planes to measure vibration in the three directions.
	www.stiweb.com /appnotes/velocity.htm (1059 words)

	Group velocity - Wikipedia, the free encyclopedia
		The group velocity of a wave is the velocity with which the variations in the shape of the wave's amplitude (known as the modulation or envelope of the wave) propagates through space.
		This "group velocity dispersion" is an important effect in the propagation of signals through optical fibers and in the design of short pulse lasers.
		The idea of a group velocity distinct from a wave's phase velocity was first proposed by W.R. Hamilton in 1839, and the first full treatment was by Rayleigh in his "Theory of Sound" in 1877.
	en.wikipedia.org /wiki/Group_velocity (292 words)

	Group velocity -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-11-04)
		The group velocity of a ((physics) a movement up and down or back and forth) wave is the (Distance travelled per unit time) velocity with which the overall shape of the wave's amplitude (known as the envelope of the wave) propagates through space.
		The group velocity is often thought of as the velocity at which ((physics) the capacity of a physical system to do work; the units of energy are joules or ergs) energy or (A message received and understood) information is conveyed along a wave.
		This "group velocity dispersion" is an important effect in the propagation of signals through (A very thin fiber made of glass that functions as a waveguide for light; used in bundles to transmit images) optical fibers and in the design of short pulse lasers.
	www.absoluteastronomy.com /encyclopedia/g/gr/group_velocity.htm (452 words)

	Refractive index (Site not responding. Last check: 2007-11-04)
		The phase velocity is defined as the rate at which the crests of the waveform propagate; that is, the rate at which the phase of the waveform is moving.
		The group velocity is the rate that the envelope of the waveform is propagating; that is, the rate of variation of the amplitude of the waveform.
		It is the group velocity that (almost always) represents the rate that information (and energy) may be transmitted by the wave, for example the velocity at which a pulse of light travels down an optical fibre.
	www.sciencedaily.com /encyclopedia/refractive_index (856 words)

	[No title] (Site not responding. Last check: 2007-11-04)
		A radio transceiver, comprising: a receiver, for receiving radio signals; a quality estimator, for estimating a first measure of quality of received radio signals; and a speed estimator, for obtaining a measure of relative velocity of the transceiver, wherein the measure of relative velocity is used as an input to the quality estimator.
		A method of estimating quality of received radio signals in a transceiver, comprising: obtaining a measure of relative velocity of the transceiver; and estimating the quality using an estimation algorithm, including using the measure of relative velocity as an input to the estimation algorithm.
		A method of estimating quality of radio signals received in a receiver, comprising: obtaining a measure of relative velocity of the transceiver; and estimating the quality using an estimation algorithm, including using the measure of relative velocity as an input.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=01/28124.010419&ELEMENT_SET=DECL (1737 words)

	RADAR
		Velocity is determined by means of measuring the change in frequency of the output signal bursts.
		The limits on the range of detectable velocities are determined primarily by two factors, the interburst period and the carrier frequency of the radar.
		Since velocity determination involves decimating the original signal, velocity aliasing occurs, limiting the range of velocities that are detectable in both the negative and positive directions.
	www.owlnet.rice.edu /~elec431/projects95/radar/project.html (2821 words)

	sciforums.com - Phase velocity > Signal velocity?
		If I understand Phase Velocity, it is the rate at which of any point of a wave (the crest, for example) propagates through space.
		phase velocity is the speed of a single "harmonic" of a wave packet.
		the phase velocity of a wave is ω/k, and the group velocity is dω/dk.
	www.sciforums.com /printthread.php?t=28083 (255 words)

	Automatically cancelling turn signal apparatus - Patent 4358751
		Self-cancelling turn signals have long been employed in automobiles, where the turn signal is cancelled by the turning of the steering wheel as the automobile emerges from the turn.
		The turn signal cancelling apparatus comprises left turn and right turn indicator means together with means for selectively activating the indicator means and means for inactivating the turn indicator responsive to a predetermined positive change in vehicle velocity.
		The turn signals are controlled by a thumb-operated lever 16 having an arcuate, knurled control surface 18 which permits easy movement of the lever 16 to the left or right by use of the thumb.
	www.freepatentsonline.com /4358751.html (2626 words)

	Hybrid suspension position and body velocity sensing system for automotive suspension control system - Patent 4838574
		The computer may then use a body velocity signal and suspension velocity signal obtained by differentiating the suspension position signal for producing a control signal with a value based upon a comparison of the two velocity signals-- i.e., the body velocity signal and the suspension velocity signal.
		If this mode of implementation is chosen, the control signal output by the controller to the adjustable suspension unit may be selected such that the magnitude of the damping produced by the suspension unit is proportional to the magnitude of the relative motion of the body with respect to the road wheel.
		When a control signal is applied to coil 70 by means of coil connector 74 and control lead 76, the coil and permanent magnet will combine to produce a force tending to close sleeve valve 66 against sleeve valve seat 67, thereby preventing flow past the sleeve valve.
	www.freepatentsonline.com /4838574.html (5482 words)

	Phase, Group, and Signal Velocity
		The velocity of a wave can be defined in many different ways, partly because there many different kinds of waves, and partly because we can focus on different aspects or components of any given wave.
		On this basis we might say that the velocity of the signal is unambiguously equal to the "phase velocity", but in this context the phase velocity could only be defined as the speed of the leading (or trailing) edge of the overall signal.
		The "phase velocity" of the internal oscillations is
	www.mathpages.com /home/kmath210/kmath210.htm (1990 words)

	Wilcoxon: Industrial Vibration Sensor Selection: Piezovelocity Transducers
		Velocity, which increases in direct proportion to machine speed, allows the destructive vibration energy to be evaluated independent of frequency.
		The relative motion of the magnet induces a voltage in the coil proportional to velocity.
		Above the crossover frequency the amplitude of the velocity signal is attenuated and decreases by one half as the frequency is doubled.
	www.wilcoxon.com /technotes/tn18.html (2196 words)

	Technical considerations in Magnetic Resonance Angiography (Site not responding. Last check: 2007-11-04)
		The MR signal is proportional to the transverse magnetization i.e.
		For the vessels in the brain, the flow velocity is 60cm/s.
		If a scan is made in which the specified flow velocity is smaller than the peak blood velocity, the signal in the middle of the vessel will be aliased and will be presented as backward flow.
	mripractice.tripod.com /mrpractice/id24.html (3483 words)

	Group velocity
		The group velocity of a wave is the velocity with which the overall shape of the wave's amplitude (known as the envelope of the wave) progagates through space.
		The group velocity is defined in terms of the wave's angular frequency ω and wave number k by
		However, it is possible to design experiments where the group velocity of laser light pulses sent through specially prepared materials significantly exceeds the signal velocity, and even exceeds the speed of light.
	www.brainyencyclopedia.com /encyclopedia/g/gr/group_velocity.html (266 words)

	High accuracy signal processing for magnetic flowmeter - US Patent 6505517 (Site not responding. Last check: 2007-11-04)
		A signal processor includes the wavelet transformer and is disposed to perform a wavelet transformation on the EMF output and provide a decomposition signal related to velocity of the fluid.
		where E is the isolated signal output 153 which is related to the EMF output 134, V is the velocity of the fluid, D is the diameter of flow tube 108 and B is the strength of the magnetic field in the fluid.
		The isolated signal is analyzed by neural network 250 at 280 and the output from the neural network 250 is filtered using median filter 206 at 282.
	www.patentstorm.us /patents/6505517.html (7457 words)

	Print head servo and velocity controller with non-linear compensation - US Patent 6554395 (Site not responding. Last check: 2007-11-04)
		The print head controller forms a motor drive signal from the sum of a first term corresponding to the square root of the absolute value of the error signal and a second term corresponding to a dead band signal having a predetermined slope if said error signal exceeds a predetermined value.
		forming a motor drive signal from the sum of a first term corresponding to the square root of the absolute value of the error signal and a second term corresponding to a dead band signal having a predetermined slope if said error signal exceeds a predetermined value.
		supply a motor drive signal to said drive motor from the sum of a first term corresponding to the square root of the absolute value of said error signal and a second term corresponding to a dead band signal having a predetermined slope if said error signal exceeds a predetermined value.
	www.patentstorm.us /patents/6554395.html (4307 words)

	AOE 3054 Experiment #4 LASER DOPPLER ANEMOMETRY
		The frequency of this fluctuation is proportional to the velocity of the particle normal to the fringes.
		The proportion of the scattered light that is focused on to the photodetector increases with the area of the lens and decreases as the inverse square of the distance from the measurement volume to the lens.
		You might be wise to measure the inflow velocity far upstream of the cylinder - since this is the logical velocity to normalize all your measurements on, you might be unwise to trust the nominal calibration (done ages ago, without the cylinder in the flow).
	www.aoe.vt.edu /~devenpor/aoe3054/manual/expt4/text.html (9123 words)

	MOTION PERCEPTION DURING SELF-MOTION
		The present model explains the phenomenon as being identical to the velocity underestimation phenomenon during pursuit eye movements: when a stimulus is tracked with the eyes, it moves in the same direction as the eyes, and thus its velocity is underestimated.
		However, at a certain moment fixation point velocity became equal to the velocity of the pattern, that is, it became part of the pattern.
		Since velocity relates mathematically to position, it might be possible to extend the present model to include the subjective perception of the position of stimuli in space, and maybe also the perception of direction and orientation of stimuli in space.
	www.bbsonline.org /Preprints/OldArchive/bbs.wertheim.html (17761 words)

	Faster-than-Light Laser Pulses? - UFO Evidence
		The phase velocity is the speed with which the maxima and minima of the light wave move forward.
		The observed group velocity that the NEC group reports is vg = -c/310, i.e., the group velocity is a small negative fraction of the speed of light.
		He points out that a signal must both rise above the zero baseline and return to zero, and that the superluminal effect that he observed was sufficiently small that with pulses of a width compatible with his apparatus, there was no possibility of having a rise-and-fall signal pulse that could violate Einsteinian causality.
	www.ufoevidence.org /documents/doc1096.htm (2114 words)

	Superluminal signal velocity, Ann. Phys. (Leipzig) 7 (1998) 7 - 8, 618 - 624, G. Nimtz, for scientific review and study
		In vacuum or in a medium with normal dispersion the signal velocity is equal to both, the energy and the group velocities.
		The linewidth of the pulse represents the signal.
		The existence of a superluminal signal velocity ensures the possibility of an interchange of chronological order which is established by Radar coordinates.
	members.fortunecity.com /celfers/nimtz-paper.html (2147 words)

	FEEE - Fundamentals of Electrical Engineering and Electronics: Computational circuits
		Note that the voltmeter registering velocity (at the output of the differentiator circuit) is connected in "reverse" polarity to the output of the op-amp.
		To illustrate this problem, suppose we were deriving a measurement of car acceleration from the velocity signal obtained from a tachogenerator with worn brushes or commutator bars.
		Noise voltage present in a signal to be differentiated need not be of significant amplitude to cause trouble: all that is required is that the noise profile have fast rise or fall times.
	www.vias.org /feee/analog_07.html (3743 words)

	10.4.1 Electrical Methods (Site not responding. Last check: 2007-11-04)
		Velocity of the P-wave in homogenous "isotropic" media is related to the modulus and density of the medium through which the wave travels and is given as:
		Although pulse velocity varies with different concrete mixes, the average pulse velocity of typical concrete is approximately 3,600 m/s.
		However, the tradeoff is that the higher the source signal frequency, the greater the signal absorption and the shorter the wavelength.
	www.cflhd.gov /agm/geoApplications/BoreholeMethods/1048Hole2HoleLogging.htm (1920 words)

	Dictionary of Technical Terms for Aerospace Use - V
		In sense 1, velocity is often used synonymously with speed, as in the velocity of the airplane, but in such contexts speed is properly the preferred term; except in the compound airspeed, velocity is preferred to speed in reference to motion of air or other fluid.
		The velocity of escape on the surface of the earth is nearly 7 miles per second, neglecting air resistance.
		In this gyro, output signals are produced by gimbal angular displacements which correspond to components of the angular displacements of the base about two orthogonal axes.
	tcp-impl.grc.nasa.gov /~dglover/dictionary/v.html (3242 words)

	Magnetic Resonance TIP - MRI Database : Angiography
		The signal will be directly proportional to the velocity because of the relation between blood flow-velocity and signal intensity.
		Two data volumes are measured; the flow-rephased images show bright signal, the flow-dephased image show dark flow, whereby in both data volumes the signal of the stationary tissue looks the same.
		The data volumes are subtracted and the signal intensity of flowing blood remains.
	www.mr-tip.com /serv1.php?type=db1&dbs=Angiography (939 words)

	Transducers
		By performing square root extraction and scaling to the velocity pressure signal, the resulting output signal is linear to velocity (fpm) or volume (cfm).
		The Square Root Extractor Circuits are used in all flow transducers to conform the output to the square root curve of velocity vs. velocity pressure.
		This circuit is essential for signal accuracy when the output is made linear to velocity or airflow.
	www.paragoncontrols.com /Transducers.htm (429 words)

	Velocity Electronics
		Velocity Electronics' senior management team brings together industry veterans with a deep knowledge of electronic components and professionals from a wide variety of highly successful businesses.
		Velocity CEO Tim Gray is an entrepreneur and business leader with experience overseeing all aspects of a company's operations from finance, accounting and legal, to sales, marketing, software development and international expansion.
		Prior to joining the Velocity team in 2003, Kris Kelly served as global strategic manager for one of the largest independent distributors in the world, where he coordinated global sales initiatives with a number of Fortune 500 companies, including Solectron, AMD and Alcatel.
	velocityelec.com /about-velocity/executive-team.jsp (1704 words)

	Good news for causality (November 2004) - News - PhysicsWeb
		Two types of velocity are used to describe the propagation of a wave in a dispersive medium: the phase velocity and the group velocity.
		The phase velocity is the speed at which light of a single wavelength moves.
		This means, therefore, that neither the group nor the phase velocity can be used to describe the speed at which the information in the pulse travels, and we need to define it by another velocity - the "signal velocity".
	physicsweb.org /articles/news/8/11/10/1 (484 words)

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