Equivalent circuit model dependence

Using the generalized equivalent circuit model for conversion coated surfaces shown in Fig. 22, it is possible to track the time-dependent changes in the resistances and capacitances of the intact coating and evolving pits. Figure 25 shows representative Bode plots for CeCl3-passivated and bare A1 7075-T6 immersed in 0.5 M NaCl solution (81). Spectra like these were collected over 35... 

Figure 31 Time-dependent changes in equivalent circuit model element values due to interrupted sealing, (a) Solution resistance, Rs, (b) porous layer resistance, Ra, (c) porous layer capacitance, CH, (d) barrier layer resistance, Rb, (e) barrier layer capacitance, Cb. (From J. L. Dawson, G. E. Thompson, M. B. H. Ahmadun. p. 255, ASTM STP 1188, ASTM, Philadelphia, PA (1993).)...

While reaction parameters were not identified by regression to impedance data, the simulation presented by Roy et al. demonstrates that side reactions proposed in the literature can account for low-frequency inductive loops. Indeed, the results presented in Figures 23.4 and 23.5 show that both models can account for low-frequency inductive loops. Other models can also account for low-frequency inductive loops so long as they involve potential-dependent adsorbed intermediates. It is generally understood that equivalent circuit models are not unique and have therefore an ambiguous relationship to physical properties of the electrochemical cell. As shown by Roy et al., even models based on physical and chemical processes are ambiguous. In the present case, the ambiguity arises from uncertainty as to which reactions are responsible for the low-frequency inductive features. 

Plasma processing reactors normally operate with the wafer biased at radio frequencies, typically in the range 0.1 to 13.56 MHz. Even if the ions injected at the sheath edge were monoenergetic, an lED would result in an RF (time-dependent) sheath, even in the absence of collisions. The literature on RF sheaths is voluminous. Both fluid [170-175] and kinetic (e.g., Monte Carlo) [176-180] simulations have been reported. One of the most important results of such simulations is the lED. The ion angular distribution (IAD) [74, 75] and sheath impedance (for use in equivalent circuit models) [32] are also of importance. 

Although the visual membrane (that contains rhodopsin) does not function as a photosynthetic membrane, the fast photoelectric signal is similar and indeed analogous to the signal from a reconstituted bacteriorhodopsin membrane. In fact, the names B1 and B2 were chosen primarily on the basis of their similarity in temperature dependence to the R1 and the R2 components of the ERP, respectively Both B1 and R1 are temperature insensitive, but both B2 and R2 are inhibited by low temperature. The ERP data published by Ostrovsky s and Skulachev s groups (60, 61) suggest that the equivalent circuit model may be applicable to the analysis of the ERP. These authors considered possible physiological roles of the ERP. However, the majority of... 

For the DDQ-doped dodecathiophene/In diode a complex impedance analysis was performed (Figure 13.35). The two partly overlapping circles can be analyzed with an equivalent circuit model shown in the inset. Instead of pure capacitance, constant phase elements Q were used which are defined as Q = 1 /((ict))"C7) which represents the impedance of a pure capacitance for n=l. Impedance scans at different bias voltages, showed that the right-hand circle strongly depends on the bias voltage. It dominates at reverse bias and rapidly diminishes with increasing forward bias. This circle can thus be ascribed to the Schottky junction impedance. The left circle may be ascribed to the impedance of a resistive layer of about 30 nm thickness at the interface between metal and semiconductor. 

This model is known as the model of the common diffuse layer (CDL) [27]. As shown in Ref. [30], both models can describe only some limiting cases and the exposition for the total capacity of the PC electrode (equivalent circuit) investigated depends on the relationship between the three lengths (1) the characteristic size of the individual planes at a PC electrode surface (2) the effective... 

The impedance of a modified electrode depends on the impedance of each of the bulk phases and on interfacial properties as well. The equivalent circuit model (ECM) is used to elucidate the contribution of different charge transfer or transport processes to the overall impedance of electrodes. The equivalent circuit modeling concern finding equivalent electrical elements best representing physical processes within a range of frequencies by assuming each element... 

In addition to capacitors and resistors, equivalent circuit models include elements that do not have electrical analogs, i.e., as the Warburg (W) element and the constant phase element (CPE). These elements can explain the deviations from theoretical predictions of the models. The Warburg element is frequency-dependent, and its impedance may be represented by following equation ... 

Table 6.7 Content of PANA dependence of parameters calculated from the equivalent circuit model for the electrospun nanofibers of PANA/PAN blends...

A picture of a microfabricated interdigitated microsensor electrode, (b) a schematic illustration of the IME, (c) the Bode plot of I Z I and 9 obtained from the frequency-dependent interrogation of an IME 1525.3 ITO device in 0.01 M PBS containing 10 mM [Ee(CN)e] (solid line, 10 mV p-t-p, offset = 0) and the corresponding fitting data (dotted line), and (d) the equivalent circuit model derived from the NLLS fitting of the impedance data... 

Device Models of Bulk Heterojunction Solar Cells. 10-27 The Equivalent Circuit Model Extended One-Diode Model Electric Field-Dependent Dissociation of the Coulomb-Coupled E-H Pairs Numerical Solution to the Drift-Diffusion Equations... 

Figure 5.13. Bode magnitude and phase angle plots showing the frequency dependence of electrochemical impedance for the equivalent circuit model in Fig. 5.11(a) [15]. (Reprinted with permission of ASM International. All rights reserved, www.asminternational.org.)...

Andreasen et al. introduced a stack model that is suitable for prediction and analysis using EIS [45]. The typical output of such a measurement is a Nyquist plot, which shows the imaginary and real parts of the impedance of the measured system. The fuU stack impedance depends on the impedance of each of the single cells of the stack. Equivalent circuit models for each single cell can be used to predict the stack impedance at different temperature profiles of the stack. The results showed that a simple equivalent circuit model can be used to simulate the stack behavior. It was concluded that a more thorough characterization is required to predict the voltage dynamics under all operating conditions. 

SAW component design is based on the application of an equivalent circuit model [29] using the values of the piezoelectric coupling coefficient of the material, Fo. and the static capacitance [30], The frequency at which the AW device operates depends on ... 

EIS data can be analyzed by modeling or fitting the impedance spectrum with an equivalent circuit to extract the physically meaningful properties of the studied system. However, the design of the equivalent circuit is very important, and sometimes, the complexity of the PEM fuel cell system makes this process difficult. Depending on the shape of the EIS spectrum, the equivalent circuit model is usually composed of resistors (R), conductors (L), and capacitors (C), which are connected in series or in parallel, as shown in Fig. 3.11 in this equivalent circuit, R, R, and Rmt represent the membrane resistance, charge transfer resistance, and mass transfer resistance, respectively, and CPEi and CPE2 represent the Rt and Rmt associated capacitances, respectively. 

Answer Hoyen, Jr.) The capacitance measured over the frequency range from 40 to lO cps decreased with increasing frequency, approaching a limit at both the high- and low-frequency values. Using an equivalent circuit model as described in the text, the capacitance of the bulk and of the space charge regions for the crystal can be calculated. The dependency is not simple function of the square of the frequency. 

FTEIS is an experimentally convenient technique for such potentiodynam-ic impedance measurements. In this approach, a series of Nyquist (or Bode) spectra is obtained in parallel with the recording of CV data. DC voltage-dependent electrode equivalent-circuit models can be developed through CNLLS analysis of the impedance spectra. However, in FTEIS postexperiment processing is often cumbersome and inconvenient, and FTEIS limits the amplitude of the excitation signal to imder 10 mV (for aqueous solutions) because of the nonlinearity of the electrochemical system. 

Yoo S, Domercq B, Kippelen B (2005) Intensity-dependent equivalent circuit parameters of organic solar cells based on pentacene and Cgo- J Appl Phys 97 103706 Mazhari B (2006) An improved solar cell circuit model for organic solar cells. Sol Energy Mater Sol Cells 90 1021... 

Access to contact resistance was first sought by modeling. Figure 1.11 shows equivalent circuits used for that purpose. Note that the bottom circuit includes head-to-toe diodes to account for non-linear contact resistance [35]. The model developed by Necliudov and coworkers also assumed a gate voltage-dependent mobility (this point will be discussed in more detail below). 

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