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Equivalent Circuit (equivalent + circuit)
Terms modified by Equivalent Circuit Selected AbstractsAC impedance analysis and EMI shielding effectiveness of conductive SBR compositesPOLYMER ENGINEERING & SCIENCE, Issue 10 2006G.T. Mohanraj Flexible conductive polymer composites were prepared using styrene,butadiene rubber (SBR) as a matrix and conductive carbon black as filler. The filler loading was varied from 10 to 60 phr. The complex AC impedance and electromagnetic interference shielding effectiveness (EMI SE) of the composites were measured at the microwave frequencies of 7.8,12.4 GHz. The effect of variation in filler concentration and measurement frequency on the AC impedance and EMI SE of the composites were investigated. Equivalent circuits describing the conduction behavior of the composites were determined by means of Nyquist plots. The complex electric modulus of the composites was also determined. Increase in the filler loading increased the capacitive nature of the materials. The composites were better defined by a parallel resistor,capacitor circuit in series with a resistor. The EMI SE was found to pass through a maximum with increase in frequency. However, with the increase in filler loading and sample thickness of the material, the EMI SE was found to increase continuously. POLYM. ENG. SCI., 46:1342,1349, 2006. © 2006 Society of Plastics Engineers. [source] Application of Electrochemical Impedance Spectroscopy for Fuel Cell Characterization: PEFC and Oxygen Reduction Reaction in Alkaline Solution,FUEL CELLS, Issue 3 2009N. Wagner Abstract The most common method used to characterise the electrochemical performance of fuel cells is the recording of current/voltage U(i) curves. Separation of electrochemical and ohmic contributions to the U(i) characteristics requires additional experimental techniques like electrochemical impedance spectroscopy (EIS). The application of EIS is an approach to determine parameters which have proved to be indispensable for the characterisation and development of all types of fuel cell electrodes and electrolyte electrode assemblies [1]. In addition to EIS semi-empirical approaches based on simplified mathematical models can be used to fit experimental U(i) curves [2]. By varying the operating conditions of the fuel cell and by the simulation of the measured EIS with an appropriate equivalent circuit, it is possible to split the cell impedance into electrode impedances and electrolyte resistance. Integration in the current density domain of the individual impedance elements enables the calculation of the individual overpotentials in the fuel cell (PEFC) and the assignment of voltage loss to the different processes. In case of using a three electrode cell configuration with a reference electrode, one can directly determine the corresponding overvoltage. For the evaluation of the measured impedance spectra the porous electrode model of Göhr [3] was used. This porous electrode model includes different impedance contributions like impedance of the interface porous layer/pore, interface porous layer/electrolyte, interface porous layer/bulk, impedance of the porous layer and impedance of the pores filled by electrolyte. [source] An investigation into the relationship between apical root Impedance and canal anatomyINTERNATIONAL ENDODONTIC JOURNAL, Issue 9 2008S. M. Ardeshna Aim, To investigate a possible relationship between apical root impedance and canal anatomy. Methodology, Twenty-three roots from human extracted teeth (mostly single rooted but also from molars) with different apical anatomy were selected. The apical anatomy was initially classified by staining the root tip to identify number of canal exits; after impedance measurements, the anatomy was confirmed by staining and clearing the dentine. The roots were divided into two groups; 12 had simple (S) anatomy (Vertucci type 1 with a single exit) and 11 had complex (C) anatomy (various Vertucci canal types with multiple exist). Impedance measurements were taken using a frequency response analyser at seven levels in the root (0.0, 0.5, 1.0, 2.0, 3.0, 4.0 and 5.0 mm short of the apical terminus) at 14 frequencies ranging from 1120 to 100 000 Hz. Care was taken to control the temperature and other variables that could confound measurement accuracy. The impedance characteristics of individual roots were compared with 37 equivalent circuits (based on a pool created from a previous study); the best fitting equivalent circuit was selected. The equivalent circuits were used as the single outcome measure describing the impedance characteristics and correlated with the canal anatomy (S/C). Generalized estimating equations were used to perform logistic regression to analyse the data. Results, Canal anatomy had a significant (P = 0.046) effect on the equivalent circuit model. One circuit (model 10) was found to be the commonest and occurred significantly more commonly in the simple canals. The odds of prevalence of circuit model 10 were 2.2 times (odds ratio 2.17, 95% confidence interval 1.01,4.63) higher in canals with simple anatomy compared with canals with complex anatomy. Conclusions, Canal anatomy had a significant effect on the equivalent circuit describing its impedance characteristics. It should be possible to use impedance spectroscopy to clinically predict and image apical canal complexities. [source] New RF extrinsic resistances extraction procedure for deep-submicron MOS transistorsINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 2 2010J. C. Tinoco Abstract The modeling of MOS transistors used for RF applications needs the definition of a lumped equivalent circuit where the intrinsic device and series extrinsic resistances are properly evaluated. The model accuracy depends on the extraction precision of each intrinsic lumped element. In order to determine the intrinsic device behavior, it is necessary to first remove the series extrinsic resistances. For this reason their extraction becomes critical for the modeling of MOS transistors in RF circuit design. Several extraction methods have been proposed; nevertheless, the measurement noise strongly affects the obtained results. The method proposed by Bracale and co-workers is the most robust extraction procedure against measurement noise, but fails to predict correctly the series extrinsic resistances for deep-submicron devices. For those reasons, we deeply analyze the method proposed by Bracale in order to understand and then overcome its limitations. Based on those analyses, a robust extraction method for deep-submicron devices is proposed. Copyright © 2009 John Wiley & Sons, Ltd. [source] An efficient neural network approach for nanoscale FinFET modelling and circuit simulationINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 5 2009M. S. Alam Abstract The present paper demonstrates the suitability of artificial neural network (ANN) for modelling of a FinFET in nano-circuit simulation. The FinFET used in this work is designed using careful engineering of source,drain extension, which simultaneously improves maximum frequency of oscillation ,max because of lower gate to drain capacitance, and intrinsic gain AV0,=,gm/gds, due to lower output conductance gds. The framework for the ANN-based FinFET model is a common source equivalent circuit, where the dependence of intrinsic capacitances, resistances and dc drain current Id on drain,source Vds and gate,source Vgs is derived by a simple two-layered neural network architecture. All extrinsic components of the FinFET model are treated as bias independent. The model was implemented in a circuit simulator and verified by its ability to generate accurate response to excitations not used during training. The model was used to design a low-noise amplifier. At low power (Jds,10,µA/µm) improvement was observed in both third-order-intercept IIP3 (,10,dBm) and intrinsic gain AV0 (,20,dB), compared to a comparable bulk MOSFET with similar effective channel length. This is attributed to higher ratio of first-order to third-order derivative of Id with respect to gate voltage and lower gds in FinFET compared to bulk MOSFET. Copyright © 2009 John Wiley & Sons, Ltd. [source] A global time domain circuit simulation of a microwave rectennaINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 1-2 2007Brahim Essakhi Abstract The paper presents a global time domain simulation of a microwave rectenna studied for wireless energy transfer. The novelty of the work is to take into account both distributed electromagnetic parts of the antenna and the rectifier circuit including lumped elements. From a 3D finite element time domain electromagnetic modelling of the structure an equivalent circuit of the antenna is deduced: the input impedance is obtained as a function of frequency over a broad band. Then a rational approximation gives a corresponding PSPICE representation. The electromotive force induced between the ports of the antenna during the microwave illumination is directly computed from the 3D transient scattering problem. The resulting equivalent circuit of the antenna is finally incorporated into the electronic simulator PSPICE, together with the lumped components of the rectenna (ideal diodes and load). Thus a global non-linear time domain analysis of the whole structure becomes available. The results obtained with the methods presented in the paper are compared with those resulting from other techniques. The approach developed in the work could efficiently improve the design stage of rectennas devoted to microwave power transfer. Copyright © 2006 John Wiley & Sons, Ltd. [source] A new equivalent circuit for inverters and its application for the determination of coupling matrix elements of narrow RF bandpass filtersINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 1 2010M. K. Haldar Abstract A new equivalent circuit for inverters is presented. Using this circuit, expression for the elements of the coupling matrix of narrow RF band pass filters is derived. The derivation is based on frequency independent coupling assumed in the synthesis of narrow RF band pass filters. Our expression is different from an earlier expression obtained using lumped circuit representations of different types of coupling and their analysis. It is shown that the earlier expression can be derived from our analysis if the coupling is assumed frequency-variant. Unlike earlier work, our derivation shows how the sign of the coupling coefficient can be obtained. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010. [source] On the small signal modeling of advanced microwave FETs: A comparative studyINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 5 2008Giovanni Crupi Abstract Although many successful techniques have been proposed in the last decades for extracting the small signal equivalent circuit for microwave transistors from scattering parameter measurements, small signal modeling is still object of intense research. Further improvement and development of the proposed methods are incessantly required to take into account the continuous and rapid evolution of the transistor technology. The purpose of this article is to facilitate the choice of the most appropriate strategy for each particular case. For that, we present a brief but thorough comparative study of analytical techniques developed for modeling different types of advanced microwave transistors: GaAs HEMTs, GaN HEMTs, and FinFETs. It will be shown that a crucial step for a successful modeling is to adapt accurately the small signal equivalent circuit topology under "cold" condition to each investigated technology. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008. [source] Computer-aided design of planar bandpass filtersINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 2 2008Rong-Chan Hsieh Abstract This article presents a simple computer-aided design method for planar bandpass filters. The filter is sequentially designed, based on the equivalent circuit of subfilters. A filter with optimal responses may be obtained. If it needs the second design iteration, the designed filter is very adequate to serve as an initial guess for optimally adjusting. Three filters were designed and tested. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008. [source] Comparison of the corrosion protection of mild steel by polypyrrole,phosphate and polypyrrole,tungstenate coatingsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008M. G. Hosseini Abstract The electrodeposition of polypyrrole,phosphate (PPy,P) and polypyrrole,tungstenate (PPy,W) on mild steel (MS) were achieved in an oxalic acid medium with cyclic voltammetry techniques. Adherent and homogeneous PPy,P and PPy,W films were obtained. The corrosion behavior of mild steel with phosphate (PPy,P) and tungstenate (PPy,W) composite coatings in 3.5% NaCl solutions were investigated through a potentiodynamic polarization technique, open-circuit potential,time curves, and electrochemical impedance spectroscopy (EIS). On the basis of a physical model for corrosion of mild steel composites, Zview (II) software was applied to the EIS to estimate the parameters of the proposed equivalent circuit. It was found that the PPy,W coatings could provide much better protection than the PPy,P and polypyrrole coatings. The effects of the phosphate and tungstenate process parameters on the morphology and structure of the passive films were investigated by scanning electron microscopy and electron dispersion X-ray analyses. The results reveal that the PPy,P and PPy,W coated electrodes offered a noticeable enhancement in protection against corrosion processes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Mechanical and corrosion behaviour of a Ti-Al-Nb alloy after deformation at elevated temperaturesMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2008M. V. Popa Abstract The mechanical properties of Ti6Al7Nb alloy deformed and heat treated at elevated temperatures were correlated with its microstructure and corrosion behaviour in Ringer (of different pH values: 2.49, 6.9 and 8.9) and Ringer,Brown solutions. Microstructural analysis revealed a Widmanstatten structure for the alloys deformed at 1100,°C (, field) and structure with , grains at 930,°C (,,+,, field). The thermo-mechanical processing improved the electrochemical behaviour of Ti6Al7Nb alloys, especially their passive state. Open circuit potential variations in time reflected more compact, stable, resistant passive films on the surface of the treated alloys. Open circuit potential gradients simulating the non-uniformities of pH along the implant surface have very low values that cannot generate galvanic corrosion. Corrosion rates and ion release are very much reduced. Impedance spectra were fitted with a two time-constants equivalent circuit for some alloys and with three time-constants equivalent circuit for other alloys. [source] Modelling and parameter comparison of equivalent circuits on the basis of impedance measurements of stainless steelsMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 4 2006M. Slemnik Abstract In our former work [1] we have discussed the impedance of differently heat treated steels X20Cr13 in 0.1 M H2SO4, undergoing an active passive transition. Impedance spectra were interpreted in terms of a model by Armstrong [2, 3], describing the electrochemical reaction at interfaces with adsorbed intermediates. The present work was performed in order to study this phenomenon in more detail, with computer simulations of a new created and more convenient equivalent circuit in comparison with the former model. Computer simulations of equivalent circuits were also made in the region of passivity which was also continuation of our earlier work [4]. In this sense the entire study for these steels was completed by collating distinctive parameter values, demonstrating electrochemical characteristics of steel X20Cr13, undergoing different heat treatments in the active-passive and passive region. [source] Exfoliation corrosion of aluminum alloy AA7075 examined by electrochemical impedance spectroscopyMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 1 2004F.-H. Cao Abstract A typical aluminum alloy, AA7075, was immersed in the EXCO solution, and its corrosion properties during different immersion time were measured repetitively using electrochemical impedance spectroscopy technique (EIS). The EIS data a were simulated using equivalent circuit with ZView program. The results show that once the exfoliation occurs, the low frequency inductive loop in the Nyquist plot associated with the relaxation phenomenon of reaction intermediates disappears, and the Nyquist plane is mainly composed of two capacitive arcs in the high frequency range and low frequency range respectively. The former originates from the original corroded surface, while the latter from the newly formed interface by exfoliation corrosion (EXCO). With the increased immersion time, the high frequency capacitance arc decreases gradually, while the low frequency capacitance arc increases gradually. From the beginning of immersion up to 9 hours, charge transfer resistance gradually decreases, illustrating the acceleration of the corrosion rate, whereas the proton concentration decreases steeply, indicating the cathodic process is pre-dominant. Then the corrosion rate decreases gradually corresponding to the exhausting of proton ions. The results also show that the exfoliation corrosion is developed from pitting corrosion through intergranular corrosion to general corrosion at the end. [source] Bandpass filter modeling employing Lorentzian distributionMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2009Mahmoud Al Ahmad Abstract This letter takes a close outlook of modeling a bandpass filter performance with the Lorentzian distribution function. Lorentzian function parameters are correlated with the filter parameters, namely, its bandwidth and center frequency. The zeros and poles of the filter are extracted from the closed form expression of the Lorentzian function, which is used to construct the rational model of the filter. This procedure is expected to optimize the overall filter performance and to construct a consistent equivalent circuit from its computed poles and zeros. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1167,1169, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24288 [source] Resonant properties of the Sierpinski-based fractal resonator and its application on low-loss miniaturized dual-mode bandpass filterMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2009Chang-Sin Ye Abstract In this article, resonant characteristics of novel microstrip resonators based on the Sierpinski carpet fractal geometries are proposed in detail. With increasing the iteration order of the Sierpinski-based fractal resonators, the resonant frequency is decreased but the unloaded quality factor is slightly enhanced. The resonant properties are discussed using the RLC equivalent circuit. Additional, the design guide for bandpass filter using the nth order resonator is also developed. Using these fractal resonators, several dual-mode bandpass filters using different order resonators can be designed and fabricated to verify the advantages of the size and insertion loss reduction. It is also found good agreement between the simulation and measurement is achieved. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1358,1361, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24321 [source] Compact low pass filter using novel elliptic shape DGSMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2009XiaoQun Chen Abstract A novel elliptic shape defected ground structure (DGS) is investigated for low pass filter (LPF) applications. An equivalent RLC circuit model is presented and its corresponding parameters are also extracted from the measured S-parameters. The filter presents the advantages of compact size, high selectivity, low insertion loss and high out-band suppression more than 32 dB from 5.15 to 10 GHz. Good agreements with response of equivalent circuit, electromagnetic simulation, and measurement is demonstrated. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1088,1091, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24263 [source] Closed-form expression of asymmetric stripline open-end and its applications for analysis of LTCC components and circuitsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2009Wanchun Tang Abstract In this article, we have obtained simple excess capacitance formula for asymmetric stripline open-end. The average error of the formula is less than 2%. On the basis of this formula and the field-based equivalent circuit model obtained by the authors before, a low-pass filter and an edge coupled stripline band-pass filter are analyzed by the field-based equivalent circuit together with the excess capacitance formula of this article. Compared with numerical results, the average errors of S parameters are less than 2%. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 406,408, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24072 [source] Lumped element equivalent circuit for the cymbal resonator bandpass filterMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2008James R. Kelly Abstract This article presents an equivalent circuit for the microstrip cymbal bandpass filter (Strassner and Chang, Microwave Opt Technol Lett 28 (2001), 33,34; Strassner and Chang, IEEE Trans Microwave Theory Techn 50 (2002), 1431,1432), together with an ABCD matrix. The circuit models the frequency response of the filter accurately. A set of polynomial equations were also developed as a design aid. These equations give the equivalent circuit component values. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2381,2384, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23671 [source] Interdevice isolation characteristics for design and fabrication of 60-GHz WPAN SoCsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2008Sungil Kim Abstract The high interdevice isolation levels is one of the key technologies in the design and fabrication of 60-GHz WPAN SoC. To obtain proper interdevice isolation levels, we have analyzed and measured substrate coupling effects with various isolation techniques like a trench and implant structure. From the analyzed and measured results, the feasibility of the implant has confirmed to be applicable to the mm-wave SoC, and also derived an equivalent circuit form these results, which can be helpful to the design and fabrication of the 60-GHz WPAN SoC. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1699,1702, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23470 [source] Modified principle of distributed ferroelectric phase shifter considering the influence of interconnecting linesMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2008An Yu Abstract The deviation between theoretic values and real data of distributed ferroelectric phase shifter is investigated by simulating an ideal model and analyzing an equivalent circuit. The deviation is shown to come from the parasitic inductance of interconnecting lines between loaded capacitors and center strip of CPW, which reduces the Bragg frequency, increases the insertion loss and phase shift. By introducing an effective capacitance to consider the effect of interconnecting lines, a modified principle is presented, which forecasts performances better. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 748,751, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23212 [source] A new analytical method to extract the small-signal equivalent circuit of high frequency FET transistorsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2008J. L. Olvera Cervantes Abstract A new set of simply analytical equations is proposed as an alternative method to calculate the intrinsic transistor elements of an extended model for microwave FET's. This method is based on Y-parameters as well as on a new process to determine the differential resistances Rfs and Rfd, including the frequency effect, in such way that measurements at very low frequencies are not required and long iterative methods are avoided. The method was applied to FET's transistors and the validity of the model is certified by direct comparison with measured data from 1 to 45 GHz. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 453,457, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23130 [source] Analysis and equivalent circuit of aperture-coupled cavity-fed microstrip patch antennaMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2006Jeong Phill Kim Abstract A simple but accurate equivalent circuit of an aperture-coupled cavity-fed microstrip patch antenna is developed. It consists of ideal transformers, admittance elements, and transmission lines, and the related circuit-element values are computed by applying the reciprocity theorem and complex power concept with the spectral-domain immittance approach. The antenna input impedance calculated from network theory is compared with the measured data, and their good agreement validates the simplicity and accuracy of the proposed equivalent-circuit model. Based on the proposed theory, the effect of structural parameters on the antenna characteristics is also examined. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 843,846, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21493 [source] A comprehensive study and modeling of centre-tap differentially driven single-turn integrated inductors for 10-GHz applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2003S. F. Lim Abstract This paper presents a complete characterization of single-turn differentially driven high-quality (Q) factor inductors at 10 GHz. The separate characterization of individual physical dimension through a series of 3D electromagnetic (EM) simulations allows us to evaluate their effects on the inductor's Q and inductance L separately. The results show that single-turn inductors can generate Q greater than 20 at 10 GHz with inductance L at the sub-nano Henry range. Finally, a lumped-element equivalent circuit of the inductor was developed for predicting associated Q, L, and frequency behavior. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 182,185, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11008 [source] Comparison of constitutive wheat bran tissues by dielectric spectroscopy and effect of their moisture contentPOLYMER INTERNATIONAL, Issue 12 2004Carole Antoine Abstract The dielectric properties of hand-isolated wheat bran tissues (outer pericarp, intermediate and aleurone layers) were studied at 58 % and 75 % RH between 0.001 and 1E10 + 6 Hz. The measured values of the real and imaginary parts of bran tissue capacitances were modelled using an electrical circuit consisting of a constant phase angle component (CPA), a Warburg impedance and a parallel capacitance. The theoretical data from the equivalent circuit are in close agreement with the experimental values and allowed us to characterize the dielectric properties of the tissue. These results showed that the aleurone layer was the most capacitive tissue even though the outer pericarp exhibited the highest resistivity. Finally, tissue moisture contents were deduced from isotherm sorption measurements for a range of RH, and the water effect on their dielectric properties was analyzed. Copyright © 2004 Society of Chemical Industry [source] Effect of 1,1,-dibenzyl-4,4,-bipyridyl dichloride (DBD) on charge-conduction process and photovoltaic response of a polypyrrole (PPy) thin-film devicePOLYMER INTERNATIONAL, Issue 4 2002S Roy Abstract The present communication deals with analysing the effect of 1,1,-dibenzyl-4,4,-bipyridyl dichloride (DBD) substitution at the N -position of 2,5-polypyrrole (PPy), on electrical, impedance and photovoltaic properties. The thin-film device was fabricated by sandwiching DBD-substituted PPy between indium tin oxide (ITO) and aluminium (Al) electrodes. The formation of a Schottky barrier with Al and ohmic contact with ITO are explained in terms of p-type semiconducting behaviour of DBD-substituted PPy. In the low-voltage region, Ohm's law is followed, while in the high-voltage region, a space-charge-limited conduction (SCLC) controlled by the exponential-trap distribution was observed. DBD substitution causes shifting of the Fermi level towards the valence-band edge and an increase in charge-carrier mobility. A remarkable change in dark electrical conductivity of the order of five has been observed in DBD-substituted PPy. The electrical and impedance measurements of an ITO/PPy:DBD/Al device confirms the formation of a Schottky barrier at the DBD-substituted PPy/Al interface. Additionally, it can be modelled by a simple equivalent circuit of two resistance,capacitance (RC) elements in series representing the bulk and a junction-region. At low frequency, the device capacitance follows a pronounced voltage dependence. From a detailed analysis of the J,V and C,V characteristics, the ionized acceptor concentration (Na), width of depletion layer (W) and potential barrier height (,b) have been evaluated. We observed a significant enhancement in photocurrent on DBD substitution. The increase in photocurrent is explained by the efficient charge separation induced by the intermolecular transfer of photo-excited electrons from PPy to DBD. The substitution also causes a reduction in the trapping centres in the material. © 2002 Society of Chemical Industry [source] Fourier Transformed Large Amplitude Square-Wave Voltammetry as an Alternative to Impedance Spectroscopy: Evaluation of Resistance, Capacitance and Electrode Kinetic Effects via an Heuristic ApproachELECTROANALYSIS, Issue 15-16 2005Abstract A detailed simulation of Fourier transformed large amplitude square-wave voltammetry is presented in the frequency domain for the process Red,Ox+e,. The simulation takes into account the influence of the electrode kinetics (Butler,Volmer model), uncompensated resistance (Ru) and double layer capacitance (Cdl). Of particular significance is the prediction that the even harmonic responses are only detected in the presence of quasi-reversibility or uncompensated resistance, and also are essentially devoid of charging current. In contrast, the DC and odd harmonic AC components exhibit much larger faradaic currents and also contain charging current. Conveniently, detailed analysis of the simulated DC and AC harmonic components reveals the presence of readily recognised patterns of behaviour with unique levels of sensitivity to electrode kinetics, Ru and Cdl, that facilitate quantitative analysis of these terms. These electrochemical parameters are generally calculated by small amplitude impedance spectroscopy and utilisation of linear analysis of equivalent circuits. Experimental studies on the one electron oxidation of ferrocene in dichloromethane (0.1,M Bu4NPF6) and the one electron reduction of [Fe(CN)6]3, in aqueous 0.5,M KCl electrolyte analysed via heuristic forms of data analysis based on recognition of patterns of behaviour, are presented as examples of a reversible process with significant uncompensated resistance and a quasi-reversible process with minimal ohmic drop, respectively. Results demonstrate the advantages of a more intuitively implemented form of data analysis than presently available with conventional forms of impedance spectroscopy. [source] An investigation into the relationship between apical root Impedance and canal anatomyINTERNATIONAL ENDODONTIC JOURNAL, Issue 9 2008S. M. Ardeshna Aim, To investigate a possible relationship between apical root impedance and canal anatomy. Methodology, Twenty-three roots from human extracted teeth (mostly single rooted but also from molars) with different apical anatomy were selected. The apical anatomy was initially classified by staining the root tip to identify number of canal exits; after impedance measurements, the anatomy was confirmed by staining and clearing the dentine. The roots were divided into two groups; 12 had simple (S) anatomy (Vertucci type 1 with a single exit) and 11 had complex (C) anatomy (various Vertucci canal types with multiple exist). Impedance measurements were taken using a frequency response analyser at seven levels in the root (0.0, 0.5, 1.0, 2.0, 3.0, 4.0 and 5.0 mm short of the apical terminus) at 14 frequencies ranging from 1120 to 100 000 Hz. Care was taken to control the temperature and other variables that could confound measurement accuracy. The impedance characteristics of individual roots were compared with 37 equivalent circuits (based on a pool created from a previous study); the best fitting equivalent circuit was selected. The equivalent circuits were used as the single outcome measure describing the impedance characteristics and correlated with the canal anatomy (S/C). Generalized estimating equations were used to perform logistic regression to analyse the data. Results, Canal anatomy had a significant (P = 0.046) effect on the equivalent circuit model. One circuit (model 10) was found to be the commonest and occurred significantly more commonly in the simple canals. The odds of prevalence of circuit model 10 were 2.2 times (odds ratio 2.17, 95% confidence interval 1.01,4.63) higher in canals with simple anatomy compared with canals with complex anatomy. Conclusions, Canal anatomy had a significant effect on the equivalent circuit describing its impedance characteristics. It should be possible to use impedance spectroscopy to clinically predict and image apical canal complexities. [source] On circuit models for quantum-classical networks,INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 5-6 2007Árpád I. Csurgay Abstract Physics is not scale invariant, and today the scale of atoms and molecules challenges designers of machines in which quantum effects have dominant sway. What role could circuit theory play in designing machines described by quantum-classical models? Classical equivalent circuits do exist for systems composed of metal contacted and wired devices, such as resonant tunneling diodes, single electron transistors, metal,insulator,metal diodes, etc. circuits, but not for quantum-entangled networks, such as multi-quantum-state atoms. If devices were not contacted and wired by macroscopic metals, i.e. devices were classically field coupled, then generalized circuit models can be introduced. Case studies have been presented on the role of circuit models in quantum-classical systems. However, there are no ideal circuit elements capable of capturing the port properties of quantum-mechanical and/or quantum-optical subsystems and their coupling to classical waveguides or cavities. Copyright © 2007 John Wiley & Sons, Ltd. [source] Temperature-frequency characteristics simulation of piezoelectric resonators and their equivalent circuits based on three-dimensional finite element modellingINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 6 2003N. Wakatsuki Abstract The electromechanical resonators made of piezoelectric crystals such as a quartz crystal are widely used for electronic devices. Their frequency,temperature characteristics are of primary importance for their applications to the frequency control devices. The present paper demonstrates numerical simulation for several types of resonators using 3-D Finite Element Modelling. The results are compared with the theoretical values whenever they are available. As they are electronic devices, the equivalent circuit representation is often favourable for describing the admittance at the electrical terminals which enables the circuit analysis including the effect of the temperature change by using commercially available circuit simulators. Copyright © 2003 John Wiley & Sons, Ltd. [source] Equivalent circuit representation for integral formulations of electromagnetic problemsINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 1 2002H. Baudrand The purpose of this study is to investigate the resources offered by electromagnetic equivalent circuits as a tool for the systematic derivation of integral equations and also, to propose consistent models for active sources. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||