Excitation variable

Panfilov and Rudenko [34] published results of numerical experiments using Pushchino kinetics, with Dj = 0, that lend credence to equations (21). (By convention, when Di D2, Dy refers to the excitation variable and D2 to the recovery variable.) They found R< N and R( B to be linear functions of K even up to very high curvatures, 0 < k < 3/Aq (where Aq is the wavelength of the underlying spiral wave). They also found that scroll rings may expand (62 < 0) as well as shrink (62 > 0) when diffusion coefficients are not equal. 

Fokker Bond Tester. An ultrasonic inspection technique commonly used for aircraft structures is based on ultrasonic spectroscopy [2]. Commercially available instruments (bond testers) used for this test operate on the principle of mechanical resonance in a multi-layer structure. A piezoelectric probe shown in Figure 3b, excited by a variable frequency sine signal is placed on the surface of the inspected structure. A frequency spectrum in the range of some tens of kHz to several MHz is acquired by the instrument, see Figure 3a. 

As with the quadmpole ion trap, ions with a particular m/z ratio can be selected and stored in tlie FT-ICR cell by the resonant ejection of all other ions. Once isolated, the ions can be stored for variable periods of time (even hours) and allowed to react with neutral reagents that are introduced into the trapping cell. In this maimer, the products of bi-molecular reactions can be monitored and, if done as a fiinction of trapping time, it is possible to derive rate constants for the reactions [47]. Collision-induced dissociation can also be perfomied in the FT-ICR cell by tlie isolation and subsequent excitation of the cyclotron frequency of the ions. The extra translational kinetic energy of the ion packet results in energetic collisions between the ions and background... 

An interferometric method was first used by Porter and Topp [1, 92] to perfonn a time-resolved absorption experiment with a -switched ruby laser in the 1960s. The nonlinear crystal in the autocorrelation apparatus shown in figure B2.T2 is replaced by an absorbing sample, and then tlie transmission of the variably delayed pulse of light is measured as a fiinction of the delay This approach is known today as a pump-probe experiment the first pulse to arrive at the sample transfers (pumps) molecules to an excited energy level and the delayed pulse probes the population (and, possibly, the coherence) so prepared as a fiinction of time. 

Excitable media are some of tire most commonly observed reaction-diffusion systems in nature. An excitable system possesses a stable fixed point which responds to perturbations in a characteristic way small perturbations return quickly to tire fixed point, while larger perturbations tliat exceed a certain tlireshold value make a long excursion in concentration phase space before tire system returns to tire stable state. In many physical systems tliis behaviour is captured by tire dynamics of two concentration fields, a fast activator variable u witli cubic nullcline and a slow inhibitor variable u witli linear nullcline [31]. The FitzHugh-Nagumo equation [34], derived as a simple model for nerve impulse propagation but which can also apply to a chemical reaction scheme [35], is one of tire best known equations witli such activator-inlribitor kinetics ... 

Precisely controllable rf pulse generation is another essential component of the spectrometer. A short, high power radio frequency pulse, referred to as the B field, is used to simultaneously excite all nuclei at the T,arm or frequencies. The B field should ideally be uniform throughout the sample region and be on the order of 10 ]ls or less for the 90° pulse. The width, in Hertz, of the irradiated spectral window is equal to the reciprocal of the 360° pulse duration. This can be used to determine the limitations of the sweep width (SW) irradiated. For example, with a 90° hard pulse of 5 ]ls, one can observe a 50-kHz window a soft pulse of 50 ms irradiates a 5-Hz window. The primary requirements for rf transmitters are high power, fast switching, sharp pulses, variable power output, and accurate control of the phase. 

Atomic Absorption/Emission Spectrometry. Atomic absorption or emission spectrometric methods are commonly used for inorganic elements in a variety of matrices. The general principles and appHcations have been reviewed (43). Flame-emission spectrometry allows detection at low levels (10 g). It has been claimed that flame methods give better reproducibiHty than electrical excitation methods, owing to better control of several variables involved in flame excitation. Detection limits for selected elements by flame-emission spectrometry given in Table 4. Inductively coupled plasma emission spectrometry may also be employed. 

It is, however, recommended for better control and machine utilization that when the load s demand is for constant-speed operation, this must be met through separate synchronous motors at unity p.f. and the p.f. must be improved separately through synchronous condensers with variable field excitation. 

The exciter is an AC generator with a stator-mounted field. Direct cur rent for the exciter field is provided from an external source, typically u small variable voltage rectifier mounted at the motor starter. Exciter oui put is converted to DC through a three-phase, full-wave, silicon-diode bridge rectifier. Thyristors (silicon-controlled rectifiers) switch the cur rent to the motor field and the motor-starting, field-discharge resistors These semiconductor elements are mounted on heat sinks and assembled on a drum bolted to the rotor or shaft. 

Sometimes, because of process requirements, it is impossible to avoid some excitation frequencies. If the Campbell diagram shows this will occur, then the blade in question must be carefully designed to keep stresses low. When properly addressed in design, operation can take place in an area of excitation. The major variables affecting turbine selection may be listed as follows ... 

The discrete line sources described above for XPS are perfectly adequate for most applications, but some types of analysis require that the source be tunable (i.e. that the exciting energy be variable). The reason is to enable the photoionization cross-section of the core levels of a particular element or group of elements to be varied, which is particularly useful when dealing with multielement semiconductors. Tunable radiation can be obtained from a synchrotron. 

For relatively small loads, the power factor correction equipment usually takes the form of static capacitors. In larger installations, it may be more economic to install an A.C. synchronous motor that, if its excitation is adjusted correctly, can be made to draw a leading current from the supply. In most industrial plants, the load is variable, and to gain the maximum benefit from the power factor correction plant this must be varied to suit the load conditions. 

The reason for this complication of the theory is evident the truncated set may contain certain variable parameters, and, if these are carefully adjusted to render the best possible description of a specific state, they may become rather unsuitable for the description of another state. According to Section II.C(3), a truncated set should, e.g., always contain a scale factor as a variable parameter and, if this quantity is fitted to the ground state, it may give a basic set which is rather "out of scale for even the first excited state. Since the virial theorem is not satisfied for this state, the corresponding total energy may be comparatively poorly reproduced. This implies that in treating excited states, it is desirable to have reliable criteria for the accuracy of both energies and wave functions. 

Intensity variable with time during excitation No Yes... 

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