Effect of Waveform

Assuming that the cyclic waveform used in the previous section was sinusoidal then the effect of using a square wave is to reduce, at any frequency, the level of stress amplitude at which thermal softening failures start to occur. This is because there is a greater energy dissipation per cycle when a square wave is used. If a ramp waveform is applied, then there is less energy dissipation per cycle and so higher stresses are possible before thermal runaway occurs. 

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Barker A.T., Garnham C.W., and Freeston I.L. Magnetic nerve stimulation — the effect of waveform on efficiency, determination of neural membrane time constants and the measurement of stimulator output, in magnetic motor stimulation basic principles and clinical experience. Electroenceph. Clin. Neurophysiol. 1991 43 227-237. 

Sau, M. and Jana, S.C. (2004) Effect of waveforms on morphology development in chaotic mixing of polymers. 

Kuge K, Lay T (1994) Data-dependent non-double-couple components of shallow earthquake source mechanisms effects of waveform inversion instability. Geophys Res Lett 21 9-12... 

Figure 3-27 The effects of interleaving on the electrical waveforms of an off-line flyback converter. (Note spike amplitude and overall degree of "ringing.")...

Both single-phase charging systems and three-phase charging systems would contain power electronic devices that as a side effect introduce waveform distortion and create power quality problems. Filtering devices used in conjunction with residential charging systems could be used to reduce harmonics and other power quality problems, but the cost of such filtering devices is currently quite high. 

Barsom, J. M., Effect of cyclic stress waveform on corrosion fatigue crack propagation... 

FIGURE 2.18 Inotropic and lusitropic responses of guinea pig left atria to (3-adrenoceptor stimulation. Panels A to C isometric tension waveforms of cardiac contraction (ordinates are mg tension abscissae are msec), (a) Effect of 0.3 nM isoproterenol on the waveform. The wave is shortened due to an increase in the rate of diastolic relaxation, whereas no inotropic response (change in peak tension) is observed at this concentration, (b) A further shortening of waveform duration (lusitropic response) is observed with 3 nM isoproterenol. This is concomitant with positive inotropic response (increase maximal tension), (c) This trend continues with 100 nM isoproterenol, (d) Dose-response curves for ino tropy (filled circles) and lusitropy (open circles) in guinea pig atria for isoproterenol, (e) Dose-response curves for inotropy (filled circles) and lusitropy (open circles) in guinea pig atria for the P-adrenoceptor partial agonist prenalterol. Data redrawn from [6]. 

Guzelsu, N., A. J. Salkind, X. Shen, U. Patel, S. Thaler, and R. Berg, Effect of electromagnetic stimulation with different waveforms on cultured fibroplasts. Bioelectromagnetics, 15, 115 (1994). 

The effect of DP-2) is to produce a virtual pulse whose length is the width of the central lobe. Of course, this is never completely perfect since it does have side-lobes, but waveforms have been described for which the performance in this respect is excellent. DP-3) means that the Doppler frequency shift is being sampled at a discrete set of time points. If the sampling rate is faster than the Nyquist of the Doppler frequency shift, then the Doppler can be unambiguously extracted. 

In designing or improving a waveform library certain questions arise. Firstly it is important to establish the measure of effectiveness (MoE) for individual waveforms (cost function) and then to extend this to an MoE for the library. If a particular set of waveforms is added, will this improve the library in these terms and, on the other hand, how much will removing some waveforms reduce the utility of the library It is the purpose of this chapter to develop an information theoretic framework... 

The realization that current sampling on a step pulse can increase the detection sensitivity by increasing the faradaic/charging ratio is the basis for the development of various pulse voltammetric (or polarographic) techniques. Also, the pulses can be applied when it is necessary and can reduce the effect of diffusion on the analyte. Figure 18b. 11 shows the waveform and response for three commonly used pulse voltammetric techniques normal pulse voltammetry (NPY), differential pulse voltammetry (DPV), and square-wave voltammetry (SWV). 

Figure 2.21 Interference effects. Combination of the waveforms (A) and (B) which, despite having different amplitudes, are of the same wavelength and in phase with each other, results in a constructive effect and the final waveform (C) has an increased amplitude. Combination of waveforms (D) and (E), which are out of phase with each other, results in destructive interference and the final waveform (F) has a reduced amplitude.

One of the more useful functions of the DC Sweep is to plot transfer curves. A transfer curve usually plots an input versus an output. A DC transfer curve plots an input versus an output, assuming all capacitors are open circuits and all inductors are short circuits. In a DC Sweep, all capacitors are replaced by open circuits and all inductors are replaced by short circuits. Thus the DC Sweep is ideal for DC transfer curves. The Transient Analysis can also be used for DC transfer curves, but you must run the analysis with low-frequency waveforms to eliminate the effects of capacitance and inductance. Usually a DC Sweep works better for a transfer curve. The one place where a transient analysis works better is plotting a hysteresis curve for a Schmitt Trigger. For a Schmitt Trigger, the input must go from positive to negative, and then from negative to positive to trace out the entire hysteresis loop. This is not possible with a DC Sweep. 

Suppose we wish to see the effect of the other parameters. You may change any of the parameters in the SIN Attributes dialog box and then click theApply button to view the waveform. Modify the parameters as shown below ... 

Figure 4.11 Transient current and voltage waveforms showing effect of trapping and detrapping, (a) No trapping, (b) Trapping, no detrapping, (c) Trapping and detrapping (from Ref. [13]).

The effect of Sb on electron transport is not so drastic. Although Sb alloying increases the transit time dispersion, the transit time shown contains a clearly identifi-ably break in the waveform. The electron drift mobihty in a-Sb Sci alloys exhibits Arrhenius behavior. The experimentally observed activation energy of a-Se—namely,... 

The effects of the circuit in the frequency domain were also characterized. The Fourier transform of the quasi-square waveform in Figure 8.41 was taken and the results shown in Fig. 8.44. Note that the third, fifth, seventh, and ninth harmonics are suppressed by about 40db, while the eleventh and thirteenth harmonics are about 20 dB less. The IsSpice simulation of this circuit was generated using the ICL feature of IsSpice. The format of the FOURIER command is shown below in Table 8.2. The resulting circuit characteristics in the frequency domain (Fig. 8.44) compare favorably to the resulting output from the IsSpice file (Table... 

The graphical representation of this protocol is shown schematically in Fig. 10.15. Signals from two amperometric electrodes, representing channel 1 (blue) and channel 2 (red) detect to electroactive species, which is delivered to them with frequency modulation of, for example, 1 Hz. The experiment is performed in the benchtop fluid setup shown in Fig. 10.16. The first interesting observation is the presence of higher harmonics in the coherence spectrum. They arise as the effect of nonsinusoidal modulation. A pure sine wave would transform to the frequency domain as a single line. Any other waveform of the same frequency will contain higher harmonics in the spectrum. 

The ability to express a nonsinusoidal waveform as a sum of sinusoidal waves allows us to use the more common mathematical expressions and formulas to solve power system problems. In order to find the effect of a nonsinusoidal voltage or current on a piece of equipment, we only need to determine the effect of the individual harmonics and then vectorially sum the results to derive the net effect. Figure 4.4 illustrates how individual harmonics that are sinusoidal can be added to form a nonsinusoidal waveform. 

While the phase-shift angle has the effect of altering the shape of the composite waveform, the phase sequence order of the harmonics is not affected. 

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