Electrical Equivalent Research Articles

Modeling of multi-physics transients in PEM fuel cells using equivalent circuits for consistent representation of electric, pneumatic, and thermal quantities

Digital simulators of electric networks have been indispensable tools for engineers and researchers engaged in the analysis and design of electric power and energy systems. With the increasing interest to extend electric energy toward multi-energy systems covering multiple energy carriers, there arises a need to also extend the capabilities of today’s simulators. Such an extension is proposed here in the form of a Proton Exchange Membrane Fuel Cell (PEMFC) model that covers the multi-physics transients involved in the flows of the electric current, hydrogen and other gases, and the enthalpy. The modeling makes use of given analogies to allow for a uniform representation of electric, pneumatic, and thermal transients based on electric circuit equivalents. It is shown how these models representing different transients are coupled as part of a PEM fuel cell system. Validation and application are carried out to verify the value of the modeling. The investigations are performed with an electric network simulator of type EMTP (Electromagnetic Transients Program) and so substantiate the possibility of using the latter for studying multi-energy systems.

Electrostatic time dilation and redshift

We first present the salient features of the gravitational time dilation and redshift effects in two ways; by considering the oscillation frequencies/rates of clocks at different heights/potentials and by considering the photons emitted by these clocks such as atoms/nuclei. We then point out to the extension of these gravitational effects to static electricity along with two experiments performed in the '30s with null results of the electrostatic redshift. We show that the absence of this redshift is a consequence of the conservation of electric charge. We discuss the electrical time dilation and redshift effects in detail and argue that the electrostatic time dilation in an electric field must be a fact of Nature. We then present a general relativistic scheme that explains this effect. We also introduce an electrical equivalence principle analogous to the gravitational one and demonstrate how to obtain the electrostatic time dilation by this principle. We emphasize the importance of ionic atomic clocks to measure this effect whose confirmation would support the general relativistic scheme presented. We finally go over an attempt in the literature to explain the impossibility of the experimental observation of the electrostatic redshift due to its smallness by employing the Reissner - Nordström metric in general relativity. We argue that the Q2 - term in this metric is due to the minuscule contribution of the energy of the electric field of the central body to its gravitational field. Thus being gravitational, this metric cannot be used to calculate the amount of the alleged electrostatic redshift.

Structure and properties of the hybrid and topological transformer models

Three topological transformer models for low-frequency transient simulations are considered in increasing order of their topology. It is first shown that the well-known hybrid model is not a strictly topological one, but despite this, it can be used in many applications. The next is the simplified model, which is a strict electric equivalent of the popular magnetic model, and the last is a detailed electric model, which takes into account thicknesses of transformer windings. This model improvement allows one to reproduce experimentally observed behaviors of the magnetic fluxes in the legs and yokes under short circuit conditions.

Modeling of the Enthalpy Transfer Using Electric Circuit Equivalents: Theory and Application to Transients of Multi-Carrier Energy Systems

Analogies between electric, hydraulic, and thermal quantities do exist for developing various circuit models that involve quantities such as currents and voltages, flows and pressures, and heat transfers and temperatures. With the increasing interest in multi-carrier energy systems, it would be beneficial to extend the scope of analogies to the enthalpy transfer by advection. The presentation of the concept and the realization of this analogy extension are the purpose of this paper. It is shown how the enthalpy transfer is formulated using circuit equivalents and how they can be used in the modeling of components such as junctions and pipes of multi-carrier energy systems. The theoretical considerations are complemented by validation through comparison with software models and physical experiment. The value of implementing the enthalpy transfer using circuit equivalents is illustrated by the modeling of a combined heat and power multi-carrier energy system implemented in a nodal-analysis-based network simulator of the EMTP type.

Low Cost Autonomous Lock-In Amplifier for Resistance/Capacitance Sensor Measurements

This paper presents the design and experimental characterization of a portable high-precision single-phase lock-in instrument with phase adjustment. The core consists of an analog lock-in amplifier IC prototype, integrated in 0.18 µm CMOS technology with 1.8 V supply, which features programmable gain and operating frequency, resulting in a versatile on-chip solution with power consumption below 834 µW. It incorporates automatic phase alignment of the input and reference signals, performed through both a fixed −90° and a 4-bit digitally programmable phase shifter, specifically designed using commercially available components to operate at 1 kHz frequency. The system is driven by an Arduino YUN board, thus overall conforming a low-cost autonomous signal recovery instrument to determine, in real time, the electrical equivalent of resistive and capacitive sensors with a sensitivity of 16.3 µV/Ω @ εrS < 3% and 37 kV/F @ εrS < 5%, respectively.

Development of a pyrotechnically-driven PR2 electrical switch equivalent

Development of a pyrotechnically-driven PR2 electrical switch equivalent

Novel multiwalled carbon nanotube (MWCNT) modified metal oxide semiconductor field effect transistor (MOSFET) based electrode for electrophysiological measurements on human skin

Standard electrodes for electrophysiological signal acquisition in clinical applications such as electrocardiography or electromyography require the use of electrolytic gel and skin abrasion for better electrical interface between electrode and skin. Since gel dries out over a period of time, signal deterioration takes place on long duration with wet electrodes. Dry electrodes are promising alternative for long duration recording; nevertheless, they suffer from high contact impedance and motion artifacts. The proposed work introduces a novel multi-walled carbon nanotube (MWCNT) modified metal oxide semiconductor field effect transistor (MOSFET) based electrode for electrophysiological measurements on human skin. Vertically aligned metallic MWCNTs grown on the gate of MOSFETs form the contact surface of the electrode. MWCNTs penetrate the outer layer of skin for stable and improved electrical contact without the gel. The proposed electrode utilizes advantages of the MOSFET such as direct charge–current conversion, insulation between skin and instrumentation unit, and low noise pre-amplification of electrophysiological signals. Electrical equivalent of MWCNTs, design, and microfabrication of convenient MOSFET are reported. MOSFET parameters are obtained from technology computer-aided design simulation environment and combined with MWCNT parameters in the simulation program for integrated circuits emphasis. Simulated results of the proposed electrode exhibited lower contact impedance and high quality signal capture with respect to wet electrodes. The results show that the proposed electrode can be used for long duration recording of biopotentials with very high stable performance.

Evaluation of Caldera Hosted Geothermal Potential during Volcanism and Magmatism in Subduction System, NE Japan

Deep-seated geothermal reservoirs beneath calderas have high potential as sources of renewable energy. In this study, we used an analysis of melt inclusions to estimate the amount of water input to the upper crust and quantify the properties of a deep-seated geothermal reservoir within a fossil caldera, the late Miocene Fukano Caldera (formation age 8–6 Ma), Sendai, NE Japan. Our research shows that Fukano Caldera consists of the southern part and northern part deposits which differ in the age and composition. The northern deposits are older and have higher potassium and silica contents than the southern deposits. Both the northern and southern deposits record plagioclase and plagioclase–quartz differentiation and are classified as dacite–rhyolite. The fossil magma chamber underlying the caldera is estimated to have a depth of ~2–10 km and a water content of 3.3–7.0 wt.%, and when the chamber was active it had an estimated temperature of 750°C–795°C. The water input into the fossil magma chamber is estimated at 2.3–7.6 t/yr/m arc length based on the magma chamber size the water content in the magma chamber and the length of volcanism periods of Fukano Caldera, NE Japan arc. The total amount of water that is stored in the chamber is ~1014 kg. The chamber is saturated in water and has potential as a deep-seated geothermal reservoir. Based on the shape of the chamber, the reservoir measures ~10 km × 5 km in the horizontal dimension and is 7–9 km in vertical extent. The 0th estimate shows that the reservoir can hold the electric energy equivalent of 33–45 GW over 30 years of power generation. Although the Fukano reservoir has great potential, commercial exploitation remains challenging owing to the corrosive nature of the magmatic fluids and the uncertain permeability network of the reservoir.

Modeling of the hemodynamics in the feet of patients with peripheral artery disease.

To simulate the hemodynamic effects in the feet in response to a thigh cuff occlusion, we have developed a multi-compartmental model in which the circulatory system for the leg is represented by its electrical equivalents. Dynamic vascular optical tomographic imaging data previously obtained from 20 patients with peripheral artery disease (PAD) and 20 healthy subjects is used to test the model. Analyzing the clinical data with the support of the model yields diagnostic specificity and sensitivity in the 90-95% range, significantly higher than previously reported.

Transmission Line Impedance Models Considering Oxygen Transport Limitations in Polymer Electrolyte Membrane Fuel Cells

Electrochemical Impedance Spectroscopy (EIS) is a well-established technique for studying Polymer Exchange Membrane Fuel Cells (PEMFC) but data interpretation remains delicate, mostly because impedance models are either based on oversimplified equations or conversely, include too many correlated parameters. It is thus crucial to carefully choose the models to interpret impedance data, according to FC materials and operation conditions. Most of PEMFC impedance spectra are composed of two loops in Nyquist plot that can be perfectly represented by classical Randles Electrical Equivalent Circuit (EEC). However, several spectra show a straight line at high frequencies associated with proton conduction in the cathode catalyst layer. Assuming an interface electrode, the Randles EEC is poorly adapted to such spectra and one will rather use Transmission Line Models (TLM). However, since TLM do not usually consider mass transport, it is necessary to adapt the EEC, especially at the cathode. Such EEC can then be used as general FC models independently of the occurrence of the straight line at high frequencies, i.e. independently of the ratio between proton conduction and reaction kinetics limitations. These TLM EECs are then used to analyze the layer(s) at the origin of oxygen transport limitations: catalyst and/or the gas diffusion layer.

Immobilization of β-galactosidase by complexation: Effect of interaction on the properties of the enzyme

In the present work, we aimed to explore the molecular binding between alginate and β-galactosidase, as well as the effect of this interaction on the activity retention, thermal stability, and kinetic properties of the enzyme. The impact of pH and enzyme/alginate ratio on physicochemical properties (turbidity, morphology, particle size distribution, ζ-potential, FTIR, and isothermal titration calorimetry) was also evaluated. The ratio of biopolymers and pH of the system directly affected the critical pH of complex formation; however, a low alginate concentration (0.1 wt%) could achieve an electrical charge equivalence at pH 3.4 with 93.72% of yield. The binding between β-galactosidase and alginate was an equilibrium between enthalpic and entropic contributions, which promoted changes in the structure of the enzyme. Nevertheless, this conformational modification was reversible after the dissociation of the complex, which allowed the enzyme to regain its activity. These findings will likely broaden functional applications of enzyme immobilization.

On the Einthoven Triangle: A Critical Analysis of the Single Rotating Dipole Hypothesis.

Since its inception, electrocardiography has been based on the simplifying hypothesis that cardinal limb leads form an equilateral triangle of which, at the center/centroid, the electrical equivalent of the cardiac activity rotates during the cardiac cycle. Therefore, it is thought that the three limbs (right arm, left arm, and left leg) which enclose the heart into a circuit, where each branch directly implies current circulation through the heart, can be averaged together to form a stationary reference (central terminal) for precordials/chest-leads. Our hypothesis is that cardinal limbs do not form a triangle for the majority of the duration of the cardiac cycle. As a corollary, the central point may not lie in the plane identified by the limb leads. Using a simple and efficient algorithm, we demonstrate that the portion of the cardiac cycle where the three limb leads form a triangle is, on average less, than 50%.

Modeling the Contact Interface of Ultrasonic Power Transfer System Based on Mechanical and Electrical Equivalence

An ultrasonic power transfer (UPT) system consists of piezoelectric transducers attached onto a coupling media, and power is transferred through a contact interface between the transducer and medium. This paper proposes an equivalent model that characterizes the mechanisms of power transfer across contact interfaces with the metallic coupling medium. A full impedance analysis of systems with structural links and contact interfaces is conducted to develop the contact model based on the equivalence between mechanical and electrical characteristics. A mutual component representing the interacting mechanical impedance is proposed for the contact model. One practical structurally combined UPT system and two other systems with different contact levels are built using 28 kHz Langevin-type piezoelectric transducers attached to aluminum plates. It was found that the experimental results show a good agreement with the analytical results using the proposed model for both the structural and contact models. Finally, the power transfer capability of systems with structural and contact interfaces is compared using the proposed model.

Human middle-ear muscles rarely contract in anticipation of acoustic impulses

The Auditory Hazard Assessment Algorithm for Humans (AHAAH) is an electrical equivalence model of the human ear designed to predict the risk for auditory injury from a given impulse noise exposure. One concern with the model is that the middle-ear muscle contraction (MEMC) associated with the acoustic reflex is implemented as a protective mechanism for certain instances in which a person is “warned” prior to the impulse. The current study tested the assumption that the MEMC can be elicited by a conditioning stimulus prior to sound exposure (i.e., a “warned” response). In order to quantify the MEMC, we used laser-Doppler vibrometry to measure tympanic membrane motion in response to a reflex-eliciting acoustic impulse. After verifying the MEMC, we attempted to classically condition the response by pairing the reflex-eliciting acoustic impulse (unconditioned stimulus, UCS) with various preceding stimuli (conditioned stimulus, CS). Changes in the magnitude and/or time-course of the MEMC following repeated UCS-CS pairings would be evidence of MEMC conditioning. Out of the 55 subjects tested so far, both non-conditioned (n = 53) and conditioned (n = 2) responses have been observed. These findings suggest that a “warned” MEMC may not be present in enough people to justify inclusion for being considered protective.

Design and analysis of fractional order seismic transducer for displacement and acceleration measurements

Seismic transducers are widely used for measurement of displacement, velocity, and acceleration. This paper presents the design of seismic transducer in the fractional domain for the measurement of displacement and acceleration. The fractional order transfer function for seismic displacement and acceleration transducer are derived using Grünwald–Letnikov derivative. Frequency response analysis of fractional order seismic displacement transducer (FOSDT) and fractional order seismic acceleration transducer (FOSAT) are carried out for different damping ratio with the different fractional order, and the maximum dynamic measurement range is identified. The results demonstrate that fractional order seismic transducer has increased dynamic measurement range and less phase distortion as compared to the conventional seismic transducer even with a lower damping ratio. Time response of FOSDT and FOSAT are derived analytically in terms of Mittag-Leffler function, the effect of fractional behavior in the time domain is evaluated from the impulse and step response. The fractional order system is found to have significantly reduced overshoot as compared to the conventional transducer. The fractional order seismic transducer design proposed in this paper is illustrated with a design example for FOSDT and FOSAT. Finally, an electrical equivalent of FOSDT and FOSAT is considered, and its frequency response is found to be in close agreement with the proposed fractional order seismic transducer.

Finite state machine control for aircraft electrical distribution system

This study deals with the development of new control logic for more electric aircraft (MEA) electrical power systems (EPSs). A key aspect of the MEA concept is that traditional pneumatic and hydraulic loads are replaced by electrical equivalents. These new electrical systems are more reliable, highly efficient, and easier to replace or maintain. However, as the number of on-board electrical loads increases the electrical distribution systems on-board are becoming more and more complex. As a result, the control system needs to be adapted and improved in order to allow better manage the overall electrical energy flow, provide faster computational operations, and ensure operation of safety-critical loads under all fault scenarios. This study first gives a brief analysis of the different electrical system topologies before outlining potential control strategies which may be applicable to future MEA EPSs. A new control concept for MEA EPSs is then investigated and considered as a potential substitute of the classical control systems. Finally, a model of the newly proposed logic is implemented and simulated showing how it is able to select and apply a correct reconfiguration of the electrical system under different operating conditions.

Measurements for Electric Dipole of Selected Clusters Sc<sub>n</sub>-C<sub>60</sub> in Gaseous Phase

We have measured the electric dipole moment of several Scn-C60 molecules (n = 1 - 6) in gaseous phase, by coupling a matrix-assisted laser desorption source to an electric beam deflection setup which is an electric equivalent of the famous Stern Gerlach [1] one. Experimental results are compared to a qualitative charge transfer that occurs between Sc and fullerene.

Modeling of the Human Cardiovascular System for Detection of Atherosclerosis

Atherosclerosis is a pathological condition that can eventually lead to a heart attack, a stroke or a peripheral vascular disease, depending upon its site of occurrence in the human arterial network. In this work, a third order non-linear model of the cardiovascular system is proposed to distinguish between the healthy dynamics and the aforementioned pathological condition. An electrical equivalent of the cardiovascular system is presented with emphasis on systemic circulation and the model equations are derived using circuit theory concepts. The parameters are estimated using non-linear least squares estimation technique that minimizes the error between the modeled arterial blood pressure and the actual measurement data. The model has been tested on ten healthy subjects and five moderately high blood-pressure subjects. Two of the model parameters, namely, arterial compliance and peak cardiac elastance are proposed as indices of atherosclerosis. It has been shown that it is possible to distinguish between healthy and diseased subjects using these two estimated parameters.

Minimization of Ventilator-Induced Lung Injury in ARDS Patients – Part I: Complex Model of Mechanically Ventilated ARDS Lungs

AbstractA complex model of mechanically ventilated ARDS lungs is proposed in the paper. This analogue is based on a combination of four components that describe breathing mechanics: morphology, mechanical properties of surfactant, tissue and chest wall characteristics. Physical-mathematical formulas attained from experimental data have been translated into their electrical equivalents and implemented in MultiSim software. To examine the adequacy of the forward model to the properties and behaviour of mechanically ventilated lungs in patients with ARDS symptoms, several computer simulations have been performed and reported in the paper. Inhomogeneous characteristics observed in the physical properties of ARDS lungs were mapped in a multi-lobe model and the measured outputs were compared with the data from physiological reports. In this way clinicians and scientists can obtain the knowledge on the moment of airway zone reopening/closure expressed as a function of pressure, volume or even time. In the paper, these trends were assessed for inhomogeneous distributions (proper for ARDS) of surfactant properties and airway geometry in consecutive lung lobes. The proposed model enables monitoring of temporal alveolar dynamics in successive lobes as well as those occurring at a higher level of lung structure organization, i.e. in a point P0 which can be used for collection of respiratory data during indirect management of recruitment/de-recruitment processes in ARDS lungs. The complex model and synthetic data generated for various parametrization scenarios make possible prospective studies on designing an indirect mode of alveolar zone management, i.e. with

Grid Load Contributions Through Electric Vehicles and Their Uncertainties

With the numbers of electric vehicles on the increase, their additional electricity demand can no longer be neglected. From a power systems’ perspective, it is the time dependent electricity consumption that matters. In particular, the peak demand is increased in the case of uncontrolled charging, imposing additional stress on the system. Unfortunately, since there is an absence of representative electric vehicle driving patterns, a quantification of such temporal charging requirements is challenging. To overcome this problem, we developed a detailed model, which maps combustion engine vehicles onto electric vehicle equivalents. The model’s main strengths are the consideration of the diversity within the vehicle fleet as well as the differentiation into the boundary cases of pure battery electric vehicles and plug-in hybrid electric vehicles. Applied to a German traffic study, load curves for these two cases were generated. In addition, the existing uncertainty in between was quantified using Monte Carlo method. We show that the peak energy demand through electric vehicles is much greater on working days than on weekend days. Moreover, we find that the distinction between pure and plug-in-hybrid electric vehicles matters, at least for the time being. Apart from the numerical results, the model is well suited to generate input for more sophisticated investigations of charging strategies within energy system simulations.