Electrical Equivalent Research Articles

Intermingled fractal units model and electrical equivalence fractal approach for prediction of thermal conductivity of porous materials

The effective thermal conductivity of porous materials is a function of the intrinsic characteristic of the solid and the fluid phases that occupy the pores, of the volume fraction of the pores, and of their dimensional distribution. This last aspect is less known and studied than the others because the porous microstructure is difficult to define in conventional geometric terms. In this work, an Intermingled Fractal Units model (denominated IFU) is presented, developed by varying some constructive aspects of the Sierpinski carpet. Simple fractals can be used effectively to describe pore size distributions which present a regular growth toward the larger diameters and therefore are not suited to describe very common structures which present one or more peaks in their distribution. But the use of more fractal units means that the IFU is able to effectively simulate the pore size distribution, the volume fractions of the voids as well as the geometry of the microstructure of non-fractal porous materials.By turning IFU model into electrical fractal pattern, it is possible to calculate effective thermal conductivity of the materials. In this approach the value of effective thermal conductivity coefficient derived from the nth stage was used as a default value for the solid phase in the nth + 1 step.This full fractal procedure has been verified with deterministic or random fractal models as well as with some porosity–conductivity experimental data, namely, those obtained from advanced ceramics (Yitria stabilized zirconia) already available in the scientific literature and the results are comparable and very close.

Computational Modeling of Two Partly Coupled Coils Supplied by a Double Half-Bridge Resonant Inverter for Induction Heating Appliances

In this paper, an induction heating system composed of two partly coupled coils connected to a double half-bridge resonant inverter is deeply analyzed. Induction coils are electrically characterized by their electrical equivalents, usually a series RL circuit, where the inductance is determined by the magnetic energy stored in the system and the resistance is associated with the power dissipated in the load, generally, a metallic workpiece. The aim of this work is to obtain the electrical equivalent of an inductor system with two concentric coils used in domestic cookers by means of computational methods, in order to be included into the models used in computational aided electronic tools to simulate the time-domain behavior of the associated electronics. The multiple-coil system is characterized with a frequency-dependent impedance matrix, where the diagonal terms are the impedance of each isolated coil, and the nondiagonal terms are coupling impedance components describing the mutual coupling between coils. The impedance matrix is calculated with finite-element analysis tools, and equivalent passive networks are proposed to perform time-domain simulation with a good accuracy in the frequency range of interest. The proposed system has been experimentally verified, obtaining accurate time-domain waveforms and output power calculation.

FPGA-Based Test-Bench for Resonant Inverter Load Characterization

Resonant converters often require accurate load characterization in order to ensure appropriate and safe control. Besides, for systems with a highly variable load, as the induction heating systems, a real-time load estimation is mandatory. This paper presents the development of an FPGA-based test-bench aimed to extract the electrical equivalent of the induction heating loads. The proposed test-bench comprises a resonant power converter, sigma-delta ADCs, and an embedded system implemented in an FPGA. The characterization algorithm is based on the discrete-time Fourier series computed directly from the ΔΣ ADC bit-streams, and the FPGA implementation has been partitioned into hardware and software platforms to optimize the performance and resources utilization. Analytical and simulation results are verified through experimental measurements with the proposed test-bench. As a result, the proposed platform can be used as a load identification tool either for stand-alone or PC-hosted operation.

Support forces in a synchronized rotating spring-mass system and its electromagnetic equivalent

This paper deals with the dynamic analysis for the calculation of the support forces in a rotating elastic rod when subjected to simple types of axial forces. For simplicity the model starts with a linear straight spring and a lumped mass and expands into a distributed system. The analysis shows a shift in the natural frequency of the support forces, due to rotation and additional axial oscillations, these are highly influenced by both the axial and the shear forces, which are induced by the centripetal and Coriolis forces, respectively. Based on this finding, the paper shows that it is not possible to take advantage of the inertial forces and create long-term inertial thrust, even if the rotation is synchronized with the shifted natural frequency. The discussion includes extensions into the electromagnetic realm by comparing the mechanical system with its electrical equivalent.

Determining Attenuation of Impulse Noise With an Electrical Equivalent of a Hearing Protection Device

Determining the effectiveness of impulse noise attenuation with hearing protection devices (HPDs) is an important part of their selection. Measuring impulse noise parameters under an HPD would involve exposing subjects to impulses with a high peak sound pressure level. This paper presents a computational method of determining impulse noise parameters under the cups of earmuffs. Calculations are done using the transfer function of earmuffs, determined with Shaw’s electrical equivalent of an HPD, taking into account the design parameters of earmuffs. The developed method was used for calculations in the presence of impulse noise generated by gunshots. To verify the computational method, the results of these calculations were compared with the results of measurements.

Fault-Tolerant Operation of a Fully Electric Gearbox Equivalent

A fault-tolerant operation method for a dynamic electric vehicle propulsion system using variable torque versus speed characteristics is presented. With this method, the electrically powered vehicle can continue driving with a minimum performance reduction, and without the need for redundant systems on machine or electronics level. One of the possible single module fault scenarios, during which the system must continue operation, is shown. The accompanying theoretical analysis of the fault scenario is presented, and simulations and measurements are executed to demonstrate the presented solution.

HfxZr1−xO2 compositional control using co-injection atomic layer deposition

As a replacement for SiO2 based gate dielectrics, HfO2 with an admixture of ZrO2 has the potential to provide a higher dielectric constant than pure HfO2 by means of stabilization of higher-k phases. Accordingly, in this study the authors have pursued a means to control composition of HfxZr1−xO2 films grown by atomic layer deposition by simultaneously flowing Hf and Zr metal precursors during the precursor exposure step and varying the molar flow ratio. Using the tetrakis(ethylmethylamino) Hf and Zr precursors, TEMAH and TEMAZ, with either H2O or O3 co-reactants, the co-injection approach for HfxZr1−xO2 was compared with alternating HfO2 and ZrO2 growth cycles and was observed to allow uniform and tunable composition control. For the co-injection process, deviation from the cycle ratio trendline suggests more efficient chemisorption of TEMAZ compared to TEMAH. The authors have also evaluated these films in metal–oxide–semiconductor capacitor structures and verified the electrical equivalence and similar within-wafer distributions of Hf0.2Zr0.8O2 obtained from both processing schemes.

CMOS weak‐inversion log‐domain glycolytic oscillator: a cytomimetic circuit example

SUMMARYThis paper presents a 3 V, 1.21μW subthreshold log‐domain circuit which mimics the oscillations observed during the biochemical process of glycolysis due to the phosphofructokinase enzyme. The proposed electronic circuit is able to simulate the dynamics of the glycolytic oscillator and represent the time‐dependent concentration changes of the reactants and the products of the chemical process based on nonlinear differential equations which describe the biological system. By modifying specific circuit parameters, which correspond to certain chemical parameters, good agreement between the biochemical and electrical model results has been reached. The paper details the similarities between the equations that describe the biochemical process and the equations derived from the circuit analysis of a transistor and a source‐connected linear capacitor, a topology also known as the Bernoulli Cell. With the use of the Bernoulli Cell formalism, the chemical equations which describe the biochemical system have been transformed into their electrical equivalents. The analog circuit, which implements the whole process, has been synthesised, and simulation results including Monte Carlo analysis are provided, in order to verify the robustness of the proposed circuit and to compare its dynamics with prototype biological behaviour. Copyright © 2012 John Wiley & Sons, Ltd.

Electrical Cross-Correlation Spectroscopy: Measuring Picoliter-per-Minute Flows in Nanochannels

We introduce all-electrical cross-correlation spectroscopy of molecular number fluctuations in nanofluidic channels. Our approach is based on a pair of nanogap electrochemical transducers located downstream from each other in the channel. When liquid is driven through this device, mesoscopic fluctuations in the local density of molecules are transported along the channel. We perform a time-of-flight measurement of these fluctuations by cross-correlating current-time traces obtained at the two detectors. Thereby we are able to detect ultralow liquid flow rates below 10 pL/min. This method constitutes the electrical equivalent of fluorescence cross-correlation spectroscopy.

Acid-induced gelation of aqueous WPI–CMC solutions: Effect on orange oil aroma compounds retention

Electrostatic gelation under benign conditions of mixed whey protein isolate–carboxymethylcellulose aqueous solutions of relatively low biopolymer concentration was effected following pH reduction from neutral to values between the protein pI and the polysaccharide pK. Small deformation dynamic rheometry (time and frequency sweep measurements) was applied to determine the gel point and characterize the gel structure. State diagrams of biopolymer solutions in absence or presence of Tween 40 were also constructed to assess the contribution of interactions other than ionic ones to the development of the mixed gel structure. The findings are discussed in terms of the attainment of a stoichiometric electrical charge equivalence as the pH was moved towards acidity. As a consequence, the biopolymer molecules carried equal but opposite charges and protein–polysaccharide interactions took place. Retention of selected orange aroma compounds as a result of gel matrix formation was also investigated by applying the Headspace Solid Phase Microextraction technique, followed by gas chromatography–mass spectrometry analysis. The measurements indicated that a number of terpenic constituents of the orange oil were better retained in the matrix while the same was not observed in the case of the aldehydes.

Synergies from combined pulp&paper and fuel production

In this paper, the prospect of integrating a combined paper&pulp mill with fuel production via biomass gasification was investigated. In the study, three different types of gasifiers (circulating fluidised bed, entrained flow and indirect gasification) and three fuel processes (dimethyl ether, methanol and Fischer-Tropsch wax synthesis) were investigated using computer simulations. The paper reports differences from the stand-alone cases and the integrated cases, using the electricity equivalence efficiency as a measure. Only 6 out of the 18 integrated cases studied displayed a positive result from integration and no obvious fuel selection that stand out as the most beneficial one, however the synthesis of dimethyl ether is, in combination with all gasifiers assessed a rather good choice, with an change in efficiency from integration ranging from −1% to 4%. Dimethyl ether is not the best choice if the electrical equivalence is to be maximised however. In this case the combination of circulating fluidised bed gasification and methanol synthesis should be pursued. The production of Fischer-Tropsch wax should according to the chosen measure not be produced; however there is an added value in the production of a non-oxygenated fuel which has not been taken into account in this particular study. All cases leads to a reduction of 0.4–0.9 kg CO 2 per kg of dry biomass used in the process for fuel synthesis and the possibility to export bark is a more significant factor in this respect than which type of fuel is synthesised. ► A system integration with three gasifier types used for synthesising three different synthetic fuels. ► Energy efficiencies and electrical equivalence efficiencies reported. ► Results differ and the benefit of integration is not given, only some of the investigated cases show synergies on integration.

Dynamic Testing & Simulation of 4 KW (5.5 Hp) Switched Reluctance Motor using PSpice

In this paper, the requirement of mechanical model of SR Motor for determination of dynamic characteristic is presented. The PSpice is circuit oriented software package and it is believed that no direct mechanical models are available. Therefore electrical equivalent of mechanical sub systems were used for determination of dynamic characteristics.The variable inductor model is also proposed using voltage controlled component. Index Terms – Switched Reluctance Motor, Dynamic Characteristics, Torque DOI: http://dx.doi.org/10.11591/ijpeds.v1i1.42

Efecto de la movilización articular sobre la amplitud del Reflejo H en personas con espasticidad

Objective: To determine the effect of ankle joint mobilization on the H reflex amplitude of thesoleus muscle in people with spasticity. Materials and methods: A quasi-experimental study withcrossover design and simple masking was conducted in 24 randomized subjects to initiate thecontrol or experimental group. Traction and rhythmic oscillation were applied for five minutesto the ankle joint. H wave amplitude changes of Hoffmann reflex (electrical equivalent of themonosynaptic spinal reflex) was assessed, stimulating the tibial nerve at the level of the poplitealfossa and recording in the soleus muscle. In each subject 12 measurements were taken: basalrate, during and after mobilization. Changes in H reflex amplitude were calculated in relationto basal measurement. For each measurement a hypothesis test was performed (Student t test).Results: In groups of patients with brain injury and incomplete spinal cord injury, a significantdifference was found between measurements of both studies, concerning variation in H reflexamplitude during the application of joint mobilization techniques, with a decrease in the experimentalgroup and an increase in the control group. In contrast, no significant differences werefound after mobilization therapy. Patients with complete spinal cord injury showed no significantdifferences in any measurements. Conclusion: We demonstrate the effectiveness of jointmobilization in the decrease of H reflex amplitude in patients with brain injury or incompletespinal cord injury during the mobilization maneuver, but no residual effect after completion ofthe trial. This research showed no evidence regarding excitability reduction in complete spinalcord injury. We suggest that therapeutic interventions to decrease muscle tone based on the jointmobilization should be reconsidered.

Extrusion as a pretreatment to increase biogas production

Application of an extruder to increase the methane yield in a biogas production was examined, and large potential was proved. An extruder was tested on five agricultural biomass types, represented by 13 samples. The samples were analyzed for temperature, maximum particle size, biogas potential, and energy consumption. The extruder treatment increased biomass temperature by 5–35°C. Large particles (>1mm) were most affected by the extruder. Extrusion accelerated the degradation of slowly degradable organic compounds, and some otherwise nondegradable organic compounds were also degraded. The methane yield increased significantly: by 18–70% after 28days, and by 9–28% after 90days. The electrical energy equivalent of the extra methane, after subtracting the energy used by the extruder, resulted in energy surpluses of 6–68%. By day 90, the energy-efficiency of the extrusion process was ranked as follows: grass=straw=solids of flocculated manure<solids of screw-pressed manure<deep litter.

Experimental and Simulation Analysis of the Third-Order Input Interception Point in an All-Optical RF Mixer Based on a Semiconductor Optical Amplifier

We present an experimental and computing analysis of the nonlinear distortions of an all-optical radiofrequency mixer based on cross-gain modulation (XGM) in a semiconductor optical amplifier (SOA). Such an all-optical mixer is well suited for radio-over-fiber (RoF) applications. The simulation results are based on a SOA model developed under ADS™ software and are compared to experimental results in various cases. The good correlation between experimental and simulation results permits to demonstrate the ability of our SOA model to study mixing phenomenon by using a Harmonic Balance (HB) simulation method. Optical third-order input intercept point (IIP3) and its electrical equivalent are determined experimentally and by simulation with a good concordance. An optical IIP3 of -5 dBm and a spurious free dynamic range (SFDR) of 85.7 dB/Hz are obtained for a radiofrequency signal at 1 GHz. Moreover, simulations show that the IIP3 increases, all other parameters being equal, when the SOA active zone is shortened.

Low frequency constant-phase behavior in the respiratory impedance

The paper presents an underpinning theory and modeling approach for determining the origins of the constant-phase behavior in the input impedance of the respiratory system. The theory and model structure are validated using (i) simulations of the intrinsic airway anatomy and (ii) measurements in 10 healthy subjects. By means of an electrical equivalent of the air flow dynamics from trachea to alveoli, a recurrent ladder network is developed and simulated with nominal morphological values available from the literature. The result of the simulated model using morphological data was similar to the measured impedance values in 23 healthy subjects in the 4–48 Hz frequency range, suggesting that it is a suitable candidate model. In this paper, we propose to use an augmented ladder network model to identify the respiratory impedance from 10 healthy subjects in the 0.9–5.7 Hz frequency range. The identification is done by means of upper airway tract (a series RLC circuit) in cascade with the recurrent ladder network described by their initial values (i.e. trachea) and corresponding recurrent ratios for resistance, inertance and compliance. The results show that (i) the identified values are close to the conditions imposed by the theory and (ii) the constant phase appearing at lower frequencies in the measured data from the volunteers is well captured by the proposed modeling approach. We conclude that next to viscoelastic and diffusion properties, the fractal geometry plays an important role in determining the phase-constancy in the input respiratory impedance. We also speculate that pathology affecting the morphology of the lungs will lead to variations in the identified model parameters, enabling thus a classification of model parameters with disease.

Nozzle size effects on the nanoelectrospraying of Au nanocolloid in a fully voltage-controlled form

Nozzle size effects on the nanoelectrospraying of Au nanocolloid were investigated in a pure voltage controlled form. The nanoelectrospraying system was set up in a nozzle-to-plate geometry and the spray current was monitored to evaluate the performance of the nozzles during the atomization of Au colloid. Current–voltage characteristic shows that nanoelectrospray properties strongly depend on the nozzle size. In the spraying of Au nanocolloid using nozzles sized from 4 to 30 μm in diameter, two well-distinguished regimes of pulsation and cone-jet were observed with an increasing of voltage. The onset voltages for entering both modes were found to increase with the nozzle size. In the pulsation mode, pulsating frequency ranged from several tens kHz up to hundred kHz was witnessed and current with low oscillation amplitude was detected in the case of small nozzles, indicating the rate of ejected charges decreases with a fine nozzle. Meanwhile, the DC equivalent resistance derived from the best-fit model was determined to be in the range of 0.89–3.16 GΩ. In cone-jet region the equivalent resistance, representing an electrical equivalence of the spray gap, was measured to be between 0.49 and 1.41 GΩ. The relatively low resistance at high field implies better efficiency of spray in cone-jet mode compared with in pulsating mode. In both modes the equivalent resistances fall with increasing nozzle size, reflecting large nozzles easier process high volume ejections.

Real surface conductivity component as indicator for the hydraulic conductivity

Estimation of hydraulic conductivity from surface resistivity measurements is one of the most difficult and challenging hydrogeophysical targets. The promising side of this relation is the analogy between electric current flow and water flow, whereas the grand ambiguity is the non-dimensionality between both two quantities. Imaginary surface conductivity component is used recently to deduce the hydraulic conductivity via complex resistivity measurements. Since there are similar properties between imaginary (out-of-phase) and real (in-phase) surface conductivity components, the latter is used in this paper to predict the hydraulic conductivity. Two mathematical parameters were determined to express the electrical equivalent of hydraulic conductivity in sand and clay systems based on the mode of electrical double-layer formation in both systems. The reliability of the proposed method is tested through applying on two datasets representing sand and clay systems. The first dataset is a clean sand and gravel aquifer in the Keritis basin in Chania, Crete, Greece. The second is mostly clayey sand aquifer in Wadi El-Assuity, Egypt. Application of the present approach in these two cases resulted in promising nearly identical values with the measured hydraulic conductivity via pumping test or geometric hydraulic conductivity via grain size analysis.

A full voltage-controlled nanoelectrospray system and its steady characteristic analysed by empirically equivalent circuit method

Nanoelectrospray technique, or electrohydrodynamic spraying, has been utilised in wide applications including mass spectrometry, microcolloid thrusters and micro/nano-fabrication areas. In this article, a nanoelectrospray system was developed in a pure voltage-controlled fashion with low flow rates of nL/min. Electrospray occurs by applying a voltage to overcome surface tension of the liquid without auxiliary backpressure. Pronounced increase of current with applied voltage was revealed during the pressure-free spray. In the steady spray regime a linear correlation between current and voltage was clearly identified; this can be attributed directly to the unforced electrospray where the spray properties are uniquely dictated by the voltage. This behaviour may be captured by an equivalent circuit method based upon empirical results. The equivalent circuit resistance, derived from the best-fit model, represents an electrical equivalence of the gap between the nozzle and the collector; this resistance strongly depends on both the nozzle size and the spray distance. The suitability of an electrical equivalent is further confirmed by incorporating a series resistor. No obvious difference can be distinguished electrically between a resistor and the resistance of the gap, suggesting that unforced spray can be adjusted and stabilised externally by using the series resistor method.

Mathematical model for kinetics of organic particle adhesion at an electrified interface

We developed a new rigorous mathematical model of the first order and proposed a methodology for determination of kinetic parameters of organic particle adhesion at electrified interface. Mathematical model of consecutive multi-step processes contains analytical solutions of the product amount and the rate of product formation, which correspond to an electrical equivalent of charge and current transients, respectively. Synthetic data simulating amperometric measurement of particle adhesion are offered to illustrate the proposed methodology. Methodology refers to a unique experiment, which is analyzed according to the mathematical model of the two- and the three-step processes in order to discuss the validity and pertinence of both model variants. The methodology shows the principle how to sequentially separate individual components of the two- and the three-step processes using both data sets (current and charge transients), in order to accurately determine the corresponding kinetic parameters. Transition from the model of the two- to the three-step processes is examined and the criteria for their differentiation are pointed out.