Velocity of signal propagation

The relation between the velocity of signal propagation and the velocity of polar transport of auxin molecules (V ), then, is as follows ... 

The velocities of the propagation of electrical signals that have values from 0.0005 to 40m/s are sufficiently high to facilitate rapid long-distance communication and account for the rapid response phenomena observed in plants. Both the speed of propagation and the duration of action potential depend on the type of external stimulus. 

Bartlett and Corle [46] proposed modification of Maxwell s equations in the vacuum by assigning a small nonzero electric condictivity to the formalism. As pointed out by Harmuth [47], there was never a satisfactory concept of propagation velocity of signals within the framework of Maxwell s theory. Thus, the equations of the latter fail for waves with nonnegligible relative frequency bandwidth when propagating in a dissipative medium. To resolve this problem, a nonzero electric conductivity ct and a corresponding current density... 

Fig. 31. Initiation of a chemical wave on Pt(lOO) by rapidly desorbing CO locally by means of a laser pulse. The integral rate of C02 formation increases immediately after the pulse, while the local A signal is delayed due to the finite velocity of wave propagation. (From Ref. 137.)...

Fromm and Bauer [36] found that action potentials in maize sieve tubes change phloem translocation. Using macro- and microautoradiography in mature leaves of maize, Fromm and Bauer [36] studied the inhibition of phloem translocation caused by electric and cold shock. They stimulated the leaf tip with ice water and found that the velocity of signal transmission was 3-5cm/s. Upon stimulation, the microelectrode recorded a basipetally propagating action potential with a depolarizing amplitude of 80 mV in the sieve tubes (Fig. 2). During electrical stimulation, the action potential was measured in the sieve-tube system with a speed of 5cm/s. 

The velocities of these propagation modes are different. Longitudinal waves are the fastest with about twice the velocity of transverse waves. The result is that the sensor detects a rather complex waveform. In process analytical applications this situation is somewhat relaxed due to these measurements being made in what is termed a diffuse field . This arises for two reasons (1) it is impossible to resolve individual acoustic events and (2) acoustic emission waves mix due to reflections from interfaces. This means that within a small area there is no real difference in the measured acoustic emission signal, no matter where the acoustic emission sensor is mounted or its orientation. 

Velocity of propagation The velocity of signal transmission. In free space, electromagnetic waves travel at the speed of light. In a cable, the velocity is substantially lower. 

Pis are used in mieroeleetronies industry as interdielectric layers, passivation layers and a-particle barriers. The electrical performance of Pis in these applications is dictated by its dielectric constant and can be further improved by reducing the dielectric constant. The propagation velocity of signal in microelectronic devices is inversely proportional to the square of the dielectric constant of the propagating medium. Therefore, signal propagation in microelectronics devices is faster, when the dielectric constant is low. Fnrther, lower dielectric constant materials reduce crosstalk between adjacent circuit lines and transmission delay time. 

For coaxial cables, the following electrical properties related to the dielectric constant of the core material and the dimensions determine the quaUty of the signal impedance, capacitance, attenuation, crosstalk, and time delay and velocity of propagation. 

Time Delay and Velocity of Propagation. Time delay is direcdy proportional to the square root of the dielectric constant and describes the time that it takes for a signal to travel through a cable. The lower the dielectric constant, the less time required for a signal to travel through a cable. 

Multiphoton Absorption and Ionization. High laser powers can induce the simultaneous absorption of two or more photons that together provide the energy necessary to excite a transition this transition may be one that is forbidden as a single-photon process (8,297). Such absorption can be made Doppler-free by propagating two laser beams of frequency V in opposite directions, so the Doppler shifts cancel and a two-photon transition occurs at 2v for any absorber velocity. The signal is strong because aU absorbers contribute, and peak ampHtudes are enhanced by, which may... 

This type of meter can simply be clamped on the outside surface of the pipe which avoids the possibility of the transducer probes being affected by fouling. In this instance care must be taken to avoid acoustic short-circuiting, i.e. transducer signals being transmitted and received via the pipe wall. Both clamp-on and wetted versions of the counter-propagating meter are sensitive to variations in the velocity profile of the measured liquid—but not to the velocity of sound in the medium (equation 6.3). 

The velocity of propagation (v) indicates how fast a signal may travel in a medium and is given by ... 

The detector operates according to the delay-hne principle. Here a 20 pm thick anode wire and a cathode which consist out of parallel metal strips connected to a delay line are used. The charge creating event induces a signal in the cathode which propagates with a velocity of about 0.2 mm ns in both directions of the... 

---