Rectangular voltage

The considerations so far rely on constant heating power, and the way how this power is applied to the microhotplate does not play a role. In fact, a monolithically integrated control circuitry does not apply constant power but acts as an adjustable current source. Moreover, for measuring the thermal time constant experimentally, either a rectangular voltage or rectangular current pulse is applied. Analyzing the dynamic temperature response of the system leads to a measured time constant, which... 

The electrodeposition of CdS films on conductive substrates from aqueous solutions is a low-cost process, which is well suited for the preparation of film solar cells. Polycrystalline CdS films of good quality were obtained by electrolysis with rectangular voltages on indium... 

Exposure of cells to low intensity trains of unipolar rectangular voltage pulses is carried out by electric pulse generator (e.g., Grass S44 Stimulator, West Warwick, RI, USA). 

Fig. 50 Domain growth kinetics observed with PFM. Background poling prior to pulse poling was performed with 17=+30 V. Rectangular voltage pulses of 17=-30 V and length variations from 50 ps to 50 ms were applied to the back electrode. PFM imaging was done with 4 V at 92.33 kHz...

Figure 106 Experimental j—U characteristics of polymer films for various temperatures (a) and two different thickness (o,A) samples at room temperature (b). (a) Steady-state currents in poly(dialkoxy-p-phenylene vinylene) (PPV) (the layer thickness d = 125 nm). After Ref. 471. (b) Response current to 10 ps rectangular voltage pulses in poly[2-5-dimethoxy-l,4-phenylene-l,2-ethenylene-2methoxy-5-(2-ethylhexyloxy)-l,4-phenylene-l,2-ethenylene (M3EH-PPV) AU = U-Ubi, where U is the applied voltage and f/bi is the built-in potential due to a difference in the work functions of the electrodes. After Ref. 472. Copyright 2000 American Institute of Physics.

Figure 160 Voltage (a) and current (b) dependence of the time-resolved EL in tetracene single crystals, (a) Reading from bottom to top are the bias voltage Uo, the rectangular voltage pulses (U— U0), the relaxation curves of electroluminescence (F) referring to the steady-stale EL level F0, the analyzing voltage pulses with varying duration time to and delay time t(. (b) The EL decay for two different thickness (d) tetracene crystals (crystal I d 16.5 pm pm crystal II d = 118 pm) under different steady-state current conditions (1 j 63 pA/cirr 2 j 23 pA/cm2 3 j = 0.7 pA/cm2 4 / 28 pA/cirr 5 6.1 pA/cm2). Adapted from Ref. [415],...

Figure 161 EL evolution in time (a) and early time regime of the onset of EL (b) from an ITO/TPD(60nm)/ALq3(60mn)/Mg/Ag DL LED after application of a rectangular voltage pulses as a function of pulse amplitude (V). The vertical arrows show the EL onset. After Ref. [309]. Copyright 1998 American Institute of Physics.

DPOP-PPV) 50% PVK/20% PBD 80% methylpolystyvene(PS)/Al LED upon application of a rectangular voltage pulse of variable duration marked by the spikes of the overshoot EL signals. Adapted from Ref. 528. 

Figure 7.3 exhibits an example of experiment where rectangular voltage pulse of microsecond duration (upper panel) was applied and led to the respective EL responses for varied pulse magnitudes. The stationary EL appears when voltage pulse magnitude is raised above a certain threshold ( 70 V in the conditions of Figure 7.3). The appearance of the regular EL is associated with noticeable current through the device due to injection of the charge carriers, as will be shown below.

Benoit (1) performed a calculation similar to that of O Konski at a somewhat earlier date and included equations for the rise and decay of the birefringence under the action of a rectangular voltage pulse. Since the rise time depends on both permanent and induced dipole moments, it is a complex function involving more than one time constant and rather difficult to deal with experimentally. The decay time of birefringence, however, depends only on the molecular dimensions and for a rigid rod Benoit obtained the simple formula... 

An extensive but unfortunately, as yet, unpublished study by Yamaoka (28) was concerned with the mode of orientation of several polypeptides in varied solvents under the influence of a rectangular voltage pulse. While measurements could be made in most organic solvents, he was unable to obtain steady-state values for the birefringence of PBLG dissolved in benzene and dioxane, except at low concentrations in dioxane. Extremely long rise times were observed in these solvents, and the 1.4-millisecond limit on his pulse width prevented establishment of equilibrium. Yamaoka showed by means of optical rotatory dispersion that PBLG assumes a helical conformation in benzene. 

The direct measurement of the time course of the influx of Na during a depolarising rectangular voltage-clamp pulse, and during an action potential discussed in Section 3b, resolved the question of specificity of the voltage-clamp measurements, and the concept of two independent kinetic components in the membrane currents, each representing an ionic pathway with different ionic selectivity, was established without doubt. 

In the multiplexing scheme considered by Alt and Pleshko, rectangular voltage pulses with duty ratio 1/N and a common amplitude are applied to each of the N rows in succession. These row signals Fj, which may be called strobe signals, are mutually orthogonal and have identical rms values F, i.e.. 

The manganin pressure gauge is supplied by a constant voltage source that gives a rectangular voltage pulse. The pulse has an amplituduration time of 100 ps, and a current of 3-30 A. 

For reversible electrode processes, the peak current is dependent on the superimposed rectangular voltage ... 

DifTerential Pulse Polarography. The most important pulse method is differential pulse polarography (DPP). In this technique a stepped voltage rise (modern staircase technique) is used and a rectangular voltage pulse with con.stant amplitude A p of 10-100 mV is applied to each mercury drop at the end of its drop time the pulse duration fp is 40 - 60 ms. 

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