An Integrated Magnetic Circuit Model and Finite Element Model Approach to Magnetic Bearing Design
NASA Technical Reports Server (NTRS)
Provenza, Andrew J.; Kenny, Andrew; Palazzolo, Alan B.
2003-01-01
A code for designing magnetic bearings is described. The code generates curves from magnetic circuit equations relating important bearing performance parameters. Bearing parameters selected from the curves by a designer to meet the requirements of a particular application are input directly by the code into a three-dimensional finite element analysis preprocessor. This means that a three-dimensional computer model of the bearing being developed is immediately available for viewing. The finite element model solution can be used to show areas of magnetic saturation and make more accurate predictions of the bearing load capacity, current stiffness, position stiffness, and inductance than the magnetic circuit equations did at the start of the design process. In summary, the code combines one-dimensional and three-dimensional modeling methods for designing magnetic bearings.
Modeling the effects of transcranial magnetic stimulation on cortical circuits.
Esser, Steve K; Hill, Sean L; Tononi, Giulio
2005-07-01
Transcranial magnetic stimulation (TMS) is commonly used to activate or inactivate specific cortical areas in a noninvasive manner. Because of technical constraints, the precise effects of TMS on cortical circuits are difficult to assess experimentally. Here, this issue is investigated by constructing a detailed model of a portion of the thalamocortical system and examining the effects of the simulated delivery of a TMS pulse. The model, which incorporates a large number of physiological and anatomical constraints, includes 33,000 spiking neurons arranged in a 3-layered motor cortex and over 5 million intra- and interlayer synaptic connections. The model was validated by reproducing several results from the experimental literature. These include the frequency, timing, dose response, and pharmacological modulation of epidurally recorded responses to TMS (the so-called I-waves), as well as paired-pulse response curves consistent with data from several experimental studies. The modeled responses to simulated TMS pulses in different experimental paradigms provide a detailed, self-consistent account of the neural and synaptic activities evoked by TMS within prototypical cortical circuits. PMID:15788519
A model for coupled magnetic-electric circuits in electric machines with skewed slots
F. Piriou; A. Razek
1990-01-01
A model permitting the simulation of skewed-slot saturated machines associated with nonlinear external circuits is proposed. To take the slot effects into account, the magnetic circuit is modeled through the combined two-dimensional calculations along the machine axis. In this simulation the electric circuit equation is directly coupled with the magnetic one. The solution of the resulting nonlinear time-dependent equation is
NASA Astrophysics Data System (ADS)
Holmberg, P.; Bergqvist, A.; Engdahl, G.
1997-04-01
In electromagnetic drives and actuators electric, magnetic, and mechanical phenomena have to be solved for simultaneously. Moreover, the device is frequently fed by a power supply including components of power electronics. This article shows how the magnetomechanical drive can be modeled by lumped circuit elements and then be simulated together with the external electrical circuit and a mechanical load in a circuit simulation package. The circuit is easily designed and it considers both eddy currents and hysteresis in the magnetic device by means of a dual Cauer circuit.
A non-linear coupled 3D model for magnetic field and electric circuit equations
F. Piriou; A. Razek
1992-01-01
The authors propose a 3-D numerical model in which the magnetic field and electric circuit equations in the absence of eddy currents are solved simultaneously. To consider the magnetic equations, use is made of a magnetic vector potential formulation with the gauge condition (A.w=0) which makes it possible to reduce the number of unknowns. To take into account the magnetic
Magnetic Circuit Model of PM Motor-Generator to Predict Radial Forces
NASA Technical Reports Server (NTRS)
McLallin, Kerry (Technical Monitor); Kascak, Peter E.; Dever, Timothy P.; Jansen, Ralph H.
2004-01-01
A magnetic circuit model is developed for a PM motor for flywheel applications. A sample motor is designed and modeled. Motor configuration and selection of materials is discussed, and the choice of winding configuration is described. A magnetic circuit model is described, which includes the stator back iron, rotor yoke, permanent magnets, air gaps and the stator teeth. Iterative solution of this model yields flux linkages, back EMF, torque, power, and radial force at the rotor caused by eccentricity. Calculated radial forces are then used to determine motor negative stiffness.
AC machine and transformer magnetic circuit model for iron loss calculation at converter feeding
Romuald Luczkowski; R. Muszynski
2003-01-01
A new model of magnetic circuit of AC machine is presented. The model is foreseen for iron loss calculation in condition of non-sinusoidal feeding of the machine especially from the voltage source inverter with PWM. There are the separate channels for saturation, hysteresis and eddy currents phenomena in the model. The structure of the model, parameter identification and its application
Z. Q. Zhu; Y. Pang; D. Howe; S. Iwasaki; R. Deodhar; A. Pride
2005-01-01
A nonlinear adaptive lumped parameter magnetic circuit model is developed to predict the electromagnetic performance of a flux-switching permanent-magnet machine. It enables the air-gap field distribution, the back-electromotive force (back-EMF) waveform, the winding inductances, and the electromagnetic torque to be calculated. Results from the model are compared with finite-element predictions and validated experimentally. The influence of end effects is also
Lumped Circuit Models for Degenerate Band Edge and Magnetic Photonic Crystals
Gokhan Mumcu; Kubilay Sertel; John L. Volakis
2010-01-01
Multiport circuit models are presented to emulate a new class of periodic anisotropic crystals exhibiting dispersion diagrams with degenerate band edges or stationary inflection points (SIPs). Specifically, a 4-port lumped circuit is introduced to model a partially coupled pair of microstrip lines known to emulate propagation in an anisotropic medium. A 6-port circuit is also presented to model three partially
Electrically detected magnetic resonance modeling and fitting: An equivalent circuit approach
NASA Astrophysics Data System (ADS)
Leite, D. M. G.; Batagin-Neto, A.; Nunes-Neto, O.; Gómez, J. A.; Graeff, C. F. O.
2014-01-01
The physics of electrically detected magnetic resonance (EDMR) quadrature spectra is investigated. An equivalent circuit model is proposed in order to retrieve crucial information in a variety of different situations. This model allows the discrimination and determination of spectroscopic parameters associated to distinct resonant spin lines responsible for the total signal. The model considers not just the electrical response of the sample but also features of the measuring circuit and their influence on the resulting spectral lines. As a consequence, from our model, it is possible to separate different regimes, which depend basically on the modulation frequency and the RC constant of the circuit. In what is called the high frequency regime, it is shown that the sign of the signal can be determined. Recent EDMR spectra from Alq3 based organic light emitting diodes, as well as from a-Si:H reported in the literature, were successfully fitted by the model. Accurate values of g-factor and linewidth of the resonant lines were obtained.
Magnetic compression laser driving circuit
Ball, D.G.; Birx, D.; Cook, E.G.
1993-01-05
A magnetic compression laser driving circuit is disclosed. The magnetic compression laser driving circuit compresses voltage pulses in the range of 1.5 microseconds at 20 kilovolts of amplitude to pulses in the range of 40 nanoseconds and 60 kilovolts of amplitude. The magnetic compression laser driving circuit includes a multi-stage magnetic switch where the last stage includes a switch having at least two turns which has larger saturated inductance with less core material so that the efficiency of the circuit and hence the laser is increased.
Quantum Circuit Model Topological Model
Rowell, Eric C.
Quantum Circuit Model Topological Model Comparison of Models Topological Quantum Computation Eric Rowell Texas A&M University October 2010 Eric Rowell Topological Quantum Computation #12;Quantum Circuit Model Topological Model Comparison of Models Outline 1 Quantum Circuit Model Gates, Circuits
A Differential Magnetic Circuit for Teaching Purposes
ERIC Educational Resources Information Center
Kraftmakher, Yaakov
2010-01-01
A differential magnetic circuit (magnetic bridge) is described. The circuit separates the magnetic field sensor and the sample under study. A Hall probe serves as the sensor. The signal from the sensor can be enhanced by concentrating the magnetic flux. The magnetic bridge works even with dc magnetic fields. The device is used for displaying…
A CAE package for an intuitive approach to magnetic circuits
D. Muller; L. Nicolas; F. Buret
1995-01-01
We present a computer aided education package allowing one to visualize the magnetic field in and around the magnetic circuit of a double-U shaped contactor. The objective of this application is to allow students to intuitively understand the distribution of the magnetic field when varying geometric, electric and magnetic parameters. The modeling of this problem is performed by solving in
Computer simulation of magnetic field circuits in ATF
J. A. White; J. M. Googe; L. E. Nickels
1983-01-01
The proposed design of the Advanced Toroidal Facility (ATF) contains several closely coupled magnetic field circuits that are being modeled using the SUPER*SCEPTRE computer program in order to predict their transient behavior. The results of this transient analysis study will be used to determine component values and\\/or special precautions that may be required for power supply and other circuit element
J. K. Kim; S. W. Joo; S. C. Hahn; J. P. Hong; D. H. Kang; D. H. Koo
2004-01-01
This paper presents the static characteristics of the linear BLDC motor. An equivalent magnetic circuit model is derived for the prototype motor. The air-gap flux density is calculated using the equivalent magnetic circuit and compared with results from finite element analysis. The thrust force is measured for the prototype motor and is also compared with those from derived circuit model
Computer simulation of magnetic field circuits in ATF
White, J.A.; Googe, J.M.; Nickels, L.E.
1983-01-01
The proposed design of the Advanced Toroidal Facility (ATF) contains several closely coupled magnetic field circuits that are being modeled using the SUPER*SCEPTRE computer program in order to predict their transient behavior. The results of this transient analysis study will be used to determine component values and/or special precautions that may be required for power supply and other circuit element protection due to the mutual coupling between circuits. ATF is a continuous-coil torsatron device using resistive coils in a pulsed mode of operation in which a current fluctuation in one coil induces voltages in the other circuit element protection due to the mutual coupling between circuits. ATF is a continuous-coil torsatron device using resistive coils in a pulsed mode of operation in which a current fluctuation in one coil induces voltages in the other circuit that may not be desirable. The model contains the solid-state power supplies' equivalent circuits, the resistance and self-inductance of each magnetic field coil, and the mutual inductances of every coil combination. The SUPER*SCEPTRE program allows for the direct input of all electrical components as well as the mutual inductances. The power supply voltages are entered as preprogrammed wave shapes designed to achieve the desired magnetic field strengths. The outputs of this program are tables and plots of voltages and currents associated with each circuit component.
Bin Li; Gui-Dan Li; Hong-Feng Li
2011-01-01
The paper studies the magnetic field distribution of three degree-of-freedom (3-DOF) permanent magnet (PM) spherical motor adopting the 3-D magnetic equivalent circuits (MEC) method. Compared with the analytical method and finite element analysis (FEA) method, the MEC has such desirable attributes as moderate computational effort and reasonable accuracy. The model of PM spherical motor is evenly meshed into elements in
Coupled problem computation of 3-D multiply connected magnetic circuits and electrical circuits
Yann Le Floch; Gérard Meunier; Christophe Guérin; Patrice Labie; Xavier Brunotte; Dominique Boudaud
2003-01-01
This paper presents the theory and the validation of a new finite-element formulation to realize the coupling between electrical circuits and multiply connected magnetic circuits, using a magnetic scalar potential as state variable. For this purpose, we used formulations in reduced magnetic scalar potential versus T0 taking into account electrical circuits and a total magnetic scalar potential taking into account
An RF circuit model for carbon nanotubes
P. J. Burke
2003-01-01
We develop an RF circuit model for single walled carbon nanotubes for both dc and capacitively contacted geometries. By modeling the nanotube as a nanotransmission line with distributed kinetic and magnetic inductance as well as distributed quantum and electrostatic capacitance, we calculate the complex, frequency dependent impedance for a variety of measurement geometries. Exciting voltage waves on the nanotransmission line
Rohrer, Brandon Robinson; Rothganger, Fredrick H.; Verzi, Stephen J.; Xavier, Patrick Gordon
2010-09-01
The neocortex is perhaps the highest region of the human brain, where audio and visual perception takes place along with many important cognitive functions. An important research goal is to describe the mechanisms implemented by the neocortex. There is an apparent regularity in the structure of the neocortex [Brodmann 1909, Mountcastle 1957] which may help simplify this task. The work reported here addresses the problem of how to describe the putative repeated units ('cortical circuits') in a manner that is easily understood and manipulated, with the long-term goal of developing a mathematical and algorithmic description of their function. The approach is to reduce each algorithm to an enhanced perceptron-like structure and describe its computation using difference equations. We organize this algorithmic processing into larger structures based on physiological observations, and implement key modeling concepts in software which runs on parallel computing hardware.
A transformer model based on optimized Cauer circuits
NASA Astrophysics Data System (ADS)
Krah, J. H.; Engdahl, G.
2005-05-01
A transformer model is presented where both winding and core were modeled by Cauer circuits in order to take into account eddy currents. The physical property of the magnetic circuit allowed the insertion of a hysteresis model. Thermal effects in the winding insulation were also modeled by a Cauer circuit. The discretization of the circuits was optimized by an iterative method that fits the reluctance of a core part or the impedance of a winding layer to known analytical solutions. This reduced the number of required circuit elements substantially and the accuracy was increased.
Magnetic Circuit Analysis of a Tubular Permanent Magnet Linear Alternator
S. A. NASAR; C. CHEN
1987-01-01
A simplified magnetic circuit analysis of a tubular permanent magnet linear alternator (PMLA) is presented. The analysis accounts for saturation, leakage and armature reaction. Under these conditions the fields in every portion of the linear alternator (LA) are determined. The field determination leads to the alternator induced voltage and inductances.
NASA Astrophysics Data System (ADS)
Zhu, Cheng; Li, Ke; Chen, Yang; Li, Tong; Zhai, Hui-Qing; Li, Long; Liang, Chang-Hong
2013-01-01
The equivalent circuit model (ECM) and the design of compact triangular electromagnetic resonator (TER) are both introduced in this paper. ECM with analytic expressions is utilized to obtain the dispersion curves of effective permittivity and effective permeability of four kinds of TER with/without interdigital capacitor. Compared with effective parameters obtained by the parametric retrieval algorithm using simulated and measured s-parameters, the results of ECM correspond very well with the two results above, which demonstrates the effectiveness of ECM and provides us a new way to analyze the effective parameters of metamaterials.
Fermionic Models with Superconducting Circuits
U. Las Heras; L. García-Álvarez; A. Mezzacapo; E. Solano; L. Lamata
2014-11-10
We propose a method for the efficient quantum simulation of fermionic systems with superconducting circuits. It consists in the suitable use of Jordan-Wigner mapping, Trotter decomposition, and multiqubit gates, be with the use of a quantum bus or direct capacitive couplings. We apply our method to the paradigmatic cases of 1D and 2D Fermi-Hubbard models, involving couplings with nearest and next-nearest neighbours. Furthermore, we propose an optimal architecture for this model and discuss the benchmarking of the simulations in realistic circuit quantum electrodynamics setups.
Fermionic Models with Superconducting Circuits
U. Las Heras; L. García-Álvarez; A. Mezzacapo; E. Solano; L. Lamata
2015-03-31
We propose a method for the efficient quantum simulation of fermionic systems with superconducting circuits. It consists in the suitable use of Jordan-Wigner mapping, Trotter decomposition, and multiqubit gates, be with the use of a quantum bus or direct capacitive couplings. We apply our method to the paradigmatic cases of 1D and 2D Fermi-Hubbard models, involving couplings with nearest and next-nearest neighbours. Furthermore, we propose an optimal architecture for this model and discuss the benchmarking of the simulations in realistic circuit quantum electrodynamics setups.
Modeling of electromagnetic circuit of a magnetorheological fluid clutch
J. Deur; Z. Herold; M. Kostelac
2009-01-01
The steady-state and transient accuracy of magnetorheological fluid (MRF) clutch torque control is affected by the magnetic hysteresis and eddy current lag. The paper presents a nonlinear analytical model of the MRF clutch electromagnetic circuit dynamics. The model includes two state variables describing the combined solenoid and eddy current dynamics, and the dynamics induced by the magnetic hysteresis effect. The
VLSI circuits implementing computational models of neocortical circuits.
Wijekoon, Jayawan H B; Dudek, Piotr
2012-09-15
This paper overviews the design and implementation of three neuromorphic integrated circuits developed for the COLAMN ("Novel Computing Architecture for Cognitive Systems based on the Laminar Microcircuitry of the Neocortex") project. The circuits are implemented in a standard 0.35 ?m CMOS technology and include spiking and bursting neuron models, and synapses with short-term (facilitating/depressing) and long-term (STDP and dopamine-modulated STDP) dynamics. They enable execution of complex nonlinear models in accelerated-time, as compared with biology, and with low power consumption. The neural dynamics are implemented using analogue circuit techniques, with digital asynchronous event-based input and output. The circuits provide configurable hardware blocks that can be used to simulate a variety of neural networks. The paper presents experimental results obtained from the fabricated devices, and discusses the advantages and disadvantages of the analogue circuit approach to computational neural modelling. PMID:22342970
Biasing and fast degaussing circuit for magnetic materials
Dress, Jr., William B. (Lenoir City, TN); McNeilly, David R. (Maryville, TN)
1984-01-01
A dual-function circuit is provided which may be used to both magnetically bias and alternately, quickly degauss a magnetic device. The circuit may be magnetically coupled or directly connected electrically to a magnetic device, such as a magnetostrictive transducer, to magnetically bias the device by applying a d.c. current and alternately apply a selectively damped a.c. current to the device to degauss the device. The circuit is of particular value in many systems which use magnetostrictive transducers for ultrasonic transmission in different propagation modes over very short time periods.
Magnetic force microscopy method and apparatus to detect and image currents in integrated circuits
Campbell, Ann. N. (13170-B Central SE #188, Albuquerque, NM 87123); Anderson, Richard E. (2800 Tennessee NE, Albuquerque, NM 87110); Cole, Jr., Edward I. (2116 White Cloud NE, Albuquerque, NM 87112)
1995-01-01
A magnetic force microscopy method and improved magnetic tip for detecting and quantifying internal magnetic fields resulting from current of integrated circuits. Detection of the current is used for failure analysis, design verification, and model validation. The interaction of the current on the integrated chip with a magnetic field can be detected using a cantilevered magnetic tip. Enhanced sensitivity for both ac and dc current and voltage detection is achieved with voltage by an ac coupling or a heterodyne technique. The techniques can be used to extract information from analog circuits.
Magnetic force microscopy method and apparatus to detect and image currents in integrated circuits
Campbell, A.N.; Anderson, R.E.; Cole, E.I. Jr.
1995-11-07
A magnetic force microscopy method and improved magnetic tip for detecting and quantifying internal magnetic fields resulting from current of integrated circuits are disclosed. Detection of the current is used for failure analysis, design verification, and model validation. The interaction of the current on the integrated chip with a magnetic field can be detected using a cantilevered magnetic tip. Enhanced sensitivity for both ac and dc current and voltage detection is achieved with voltage by an ac coupling or a heterodyne technique. The techniques can be used to extract information from analog circuits. 17 figs.
Multilayer magnetic circuit for millimeter scale MEMS air turbine generator
NASA Astrophysics Data System (ADS)
Takato, M.; Kaneko, M.; Nishi, T.; Saito, K.; Uchikoba, F.
2013-12-01
The multilayer magnetic circuit for the millimeter scale MEMS (Micro Electrical Mechanical System) air turbine generator is proposed in this paper. The dimensions of the fabricated air turbine generator were 3.6 mm, 3.4 mm and 3.5 mm, length, width and height, respectively. The air turbine was fabricated by the MEMS technology. Multilayer magnetic circuits were fabricated by the green sheet process. The achieved output voltage and output power of the generator were 6.2mV and 1.92?VA respectively. Moreover, the optimization of the ceramic magnetic circuit for the generator was performed to improve the output power. In this experiment, the horseshoe shape circuit and step-wise shape circuit were compared on the output power by the spindle machine. When two kinds magnetic circuit were compared, the output power of the step-wise shape circuit was higher than that of the horseshoe shape circuit. The output voltage and the output power of the step-wise shape circuit were 28mV and 1.53 mVA when load resistance of 0.512 ? was connected.
Embedded-Circuit Magnetic Metamaterial Substrate Performance for Patch Antennas
Sarabandi, Kamal
Embedded-Circuit Magnetic Metamaterial Substrate Performance for Patch Antennas Kevin Buell due to the reflection at this interface is obvious and further anticipated benefits are improvements perfect value of (99%). B. Embedded Circuit Meta-Malerials The project for this paper is to achieve
Behavioral circuit modeling using neural networks
NASA Astrophysics Data System (ADS)
Kosonocky, Stephen V.
1994-02-01
A technique is presented for automatic generation of Analog Behavioral circuit models using feed-forward neural networks in static and dynamic configurations. These models are generated, by using the data output from an accurate SPICE simulation to train a neural network to model a particular circuit function. Results are given using two types of neural networks, a static neural network to model an analog multiplier, and a recurrent neural network for modeling the dynamics of a bandlimited circuit. Simulations show that neural networks are able to learn the essential nonlinear and dynamic properties found in these circuits using the training technique described.
Behavioral circuit modeling using neural networks
Stephen V. Kosonocky
1994-01-01
A technique is presented for automatic generation of Analog Behavioral circuit models using feed-forward neural networks in static and dynamic configurations. These models are generated, by using the data output from an accurate SPICE simulation to train a neural network to model a particular circuit function. Results are given using two types of neural networks, a static neural network to
Modeling and dynamic stabilization for suspension system using tuned LC circuit
Ju Jin; Toshiro Higuchi
1992-01-01
The authors develop a transfer function model of magnetic suspension systems using a tuned LC circuit by linearizing system equations near the equilibrium state. This model not only explains nicely the inherent dynamic instability but also gives the necessary condition of stability. The authors also present a novel dynamic stabilization method for magnetic suspension systems using a tuned LC circuit.
Equivalent Circuit Modeling of Hysteresis Motors
Nitao, J J; Scharlemann, E T; Kirkendall, B A
2009-08-31
We performed a literature review and found that many equivalent circuit models of hysteresis motors in use today are incorrect. The model by Miyairi and Kataoka (1965) is the correct one. We extended the model by transforming it to quadrature coordinates, amenable to circuit or digital simulation. 'Hunting' is an oscillatory phenomenon often observed in hysteresis motors. While several works have attempted to model the phenomenon with some partial success, we present a new complete model that predicts hunting from first principles.
Proposal for a Quantum Magnetic RC Circuit
NASA Astrophysics Data System (ADS)
van Hoogdalem, Kevin A.; Albert, Mathias; Simon, Pascal; Loss, Daniel
2014-07-01
We propose a setup that is the spin analog of the charge-based quantum RC circuit. We define and compute the spin capacitance and the spin resistance of the circuit for both ferromagnetic and antiferromagnetic systems. We find that the antiferromagnetic setup has universal properties, but the ferromagnetic setup does not. We discuss how to use the proposed setup as a quantum source of spin excitations, and put forward two possible experimental realizations, using either ultracold atoms in optical lattices or artificially engineered atomic-spin chains.
Quantum computation beyond the circuit model
Jordan, Stephen Paul
2008-01-01
The quantum circuit model is the most widely used model of quantum computation. It provides both a framework for formulating quantum algorithms and an architecture for the physical construction of quantum computers. However, ...
Jitter transfer function model and VLSI jitter filter circuits
Hongjiang Song; Jianan Song; A. Dey; Yan Song
2010-01-01
A closed form jitter transfer model is developed for modeling jitter-circuit interaction effects, such as jitter amplification and attenuation, in VLSI high-speed I\\/O circuits. The model is verified using circuit and behavioral simulations with good consistence. A novel jitter filtering concept and circuit is proposed to address VLSI high-speed I\\/O circuit performance issues.
Magnetic Field Analysis of Lorentz Motors Using a Novel Segmented Magnetic Equivalent Circuit Method
Qian, Junbing; Chen, Xuedong; Chen, Han; Zeng, Lizhan; Li, Xiaoqing
2013-01-01
A simple and accurate method based on the magnetic equivalent circuit (MEC) model is proposed in this paper to predict magnetic flux density (MFD) distribution of the air-gap in a Lorentz motor (LM). In conventional MEC methods, the permanent magnet (PM) is treated as one common source and all branches of MEC are coupled together to become a MEC network. In our proposed method, every PM flux source is divided into three sub-sections (the outer, the middle and the inner). Thus, the MEC of LM is divided correspondingly into three independent sub-loops. As the size of the middle sub-MEC is small enough, it can be treated as an ideal MEC and solved accurately. Combining with decoupled analysis of outer and inner MECs, MFD distribution in the air-gap can be approximated by a quadratic curve, and the complex calculation of reluctances in MECs can be avoided. The segmented magnetic equivalent circuit (SMEC) method is used to analyze a LM, and its effectiveness is demonstrated by comparison with FEA, conventional MEC and experimental results. PMID:23358368
Ho Kwon; S.-Y. Kwon; Ju Lee; Seung-kil Choi; Soo-Hyun Baek
2003-01-01
This paper presents the analysis of the permanent magnet overhang effect for permanent magnetic actuator. Generally, The overhang is often used to increase the force density in permanent magnet machineries. The overhang is especially profitable to reduce the volume after increasing the force density per volume when using the overhang effect of the permanent magnet. Therefore, 3D equivalent magnetic circuit
High-frequency power transformer model for circuit simulation
Enrico Dallago; Gabriele Sassone; Giuseppe Venchi
1997-01-01
A model for the circuit simulation of transformers used in high-frequency power processing is proposed. Many important transformer effects are combined in a single formulation. An Atherton-Jiles model with improved minor-loop handling ability is employed to simulate the hysteresis effect in the magnetic core. Eddy currents and skin and proximity effects are simulated by dynamically approximating the field and flux
Quantum Computation Beyond the "Standard Circuit Model"
K. Ch. Chatzisavvas; C. Daskaloyannis; C. P. Panos
2006-08-16
Construction of explicit quantum circuits follows the notion of the "standard circuit model" introduced in the solid and profound analysis of elementary gates providing quantum computation. Nevertheless the model is not always optimal (e.g. concerning the number of computational steps) and it neglects physical systems which cannot follow the "standard circuit model" analysis. We propose a computational scheme which overcomes the notion of the transposition from classical circuits providing a computation scheme with the least possible number of Hamiltonians in order to minimize the physical resources needed to perform quantum computation and to succeed a minimization of the computational procedure (minimizing the number of computational steps needed to perform an arbitrary unitary transformation). It is a general scheme of construction, independent of the specific system used for the implementation of the quantum computer. The open problem of controllability in Lie groups is directly related and rises to prominence in an effort to perform universal quantum computation.
Analysis of Three-Phase Power Transformer Short Circuit Magnetic Field and Forces
Hongkui Li; Gang Cheng
2010-01-01
This research studies the magnetic field and forces on the windings of transformer due to short circuit. Three dimensional finite element computation of three-phase power transformer is carried out. The model developed have been applied to power transformer and the results are verified experimentally. To verify the computation results, they are compared with those obtained using ANSYS software simulation.
Scalable Equivalent Circuit Modelling of the EM Field Coupling to Microstrips in the TEM Cell
Filip Vanhee; Johan Catrysse; Renaud Gillon; Georges Gielen
2009-01-01
A scalable circuit model of the electric and magnetic field coupling to microstrips placed on the top wall of a TEM cell is presented. The coupling parameters have been derived using approximating equations to reduce simulation times as much as possible. Simulation results of the resulting circuit model are validated by S-parameter measurements.
A SPICE-compatible full-wave equivalent circuit model for printed circuit structure analysis
Eng-Kee Chua; Er-Ping Li; Kye-Yak See; Wenyan Yin
2007-01-01
In this paper, a SPICE-compatible full-wave equivalent circuit model, based on the method of moments, for three dimensional printed circuit structure has been developed. It could be easily integrated into any circuit-based simulator to analyze the effects of the printed circuit board interconnects on high-speed circuit performance. The predicted results using the method proposed in this paper and the experimental
Resonant circuit model for efficient metamaterial absorber.
Sellier, Alexandre; Teperik, Tatiana V; de Lustrac, André
2013-11-01
The resonant absorption in a planar metamaterial is studied theoretically. We present a simple physical model describing this phenomenon in terms of equivalent resonant circuit. We discuss the role of radiative and dissipative damping of resonant mode supported by a metamaterial in the formation of absorption spectra. We show that the results of rigorous calculations of Maxwell equations can be fully retrieved with simple model describing the system in terms of equivalent resonant circuit. This simple model allows us to explain the total absorption effect observed in the system on a common physical ground by referring it to the impedance matching condition at the resonance. PMID:24514941
Simplified circuit model for MSM photodetectors
NASA Astrophysics Data System (ADS)
Cahill, Laurence W.
2000-04-01
The metal-semiconductor-metal (MSM) photodetector has the desirable attributes of large bandwidth and ease of fabrication. The lateral structure of the MSM detector allows easy incorporation into optoelectronic integrated circuits. In this paper, a new, simplified, broad-band model of the MSM detector is presented. Practical MSM detectors often exhibit an undesirable low frequency gain that is bias-dependent. It is shown in this paper that the trapping process involved in producing this gain can be modeled, in part, by including a passive equivalent circuit within the circuit model of the detector. The components of the equivalent circuit are related to the trap lifetime and the probability of a hole becoming trapped. The nonlinear effect resulting from the saturation of the electron velocity is modeled as a nonlinear current source whose magnitude is a function of bias voltage. The distributed nature of the interdigitated structure is modeled by a single set of coupled transmission lines. The trapping model and associated current sources are incorporated at the ends of the transmission lines to produce the overall model for the compete detector. Tests have shown that the proposed model provides good agreement with previously published experimental results.
High bandwidth magnetically isolated signal transmission circuit
NASA Technical Reports Server (NTRS)
Repp, John Donald (Inventor)
2005-01-01
Many current electronic systems incorporate expensive or sensitive electrical components. Because electrical energy is often generated or transmitted at high voltages, the power supplies to these electronic systems must be carefully designed. Power supply design must ensure that the electrical system being supplied with power is not exposed to excessive voltages or currents. In order to isolate power supplies from electrical equipment, many methods have been employed. These methods typically involve control systems or signal transfer methods. However, these methods are not always suitable because of their drawbacks. The present invention relates to transmitting information across an interface. More specifically, the present invention provides an apparatus for transmitting both AC and DC information across a high bandwidth magnetic interface with low distortion.
Studies of power conditioning circuits for superconductive magnetic energy store
J. Wang; J. Skiles; R. Kustom; T. Ise; F. Tsang; J. Cleary
1988-01-01
The superconductive magnetic energy store (SMES) approach to utility-load leveling has the potential for very high energy conversion efficiency and fast response to changes in load demands. It can be used to improve utility system operation economics and system stabilities. The power-conditioning circuit interfacing an SMES and a utility network consists of thyristor or gate-turn-off (GTO) device bridges of the
Modeling neural circuits in Parkinson's disease.
Psiha, Maria; Vlamos, Panayiotis
2015-01-01
Parkinson's disease (PD) is caused by abnormal neural activity of the basal ganglia which are connected to the cerebral cortex in the brain surface through complex neural circuits. For a better understanding of the pathophysiological mechanisms of PD, it is important to identify the underlying PD neural circuits, and to pinpoint the precise nature of the crucial aberrations in these circuits. In this paper, the general architecture of a hybrid Multilayer Perceptron (MLP) network for modeling the neural circuits in PD is presented. The main idea of the proposed approach is to divide the parkinsonian neural circuitry system into three discrete subsystems: the external stimuli subsystem, the life-threatening events subsystem, and the basal ganglia subsystem. The proposed model, which includes the key roles of brain neural circuit in PD, is based on both feed-back and feed-forward neural networks. Specifically, a three-layer MLP neural network with feedback in the second layer was designed. The feedback in the second layer of this model simulates the dopamine modulatory effect of compacta on striatum. PMID:25416983
NASA Astrophysics Data System (ADS)
Lai, Dong
2012-09-01
The unipolar induction DC circuit model, originally developed by Goldreich and Lynden-Bell for the Jupiter-Io system, has been applied to different types of binary systems in recent years. We show that there exists an upper limit to the magnetic interaction torque and energy dissipation rate in such a model. This arises because when the resistance of the circuit is too small, the large current flow severely twists the magnetic flux tube connecting the two binary components, leading to the breakdown of the circuit. Applying this limit, we find that in coalescing neutron star binaries, magnetic interactions produce negligible correction to the phase evolution of the gravitational waveform, even for magnetar-like field strengths. However, energy dissipation in the binary magnetosphere may still give rise to electromagnetic radiation prior to the final merger. For ultracompact white dwarf binaries, we find that unipolar induction does not provide adequate energy dissipation to explain the observed X-ray luminosities of several sources. For exoplanetary systems containing close-in Jupiters or super-Earths, the magnetic torque and energy dissipation induced by the orbital motion are negligible, except possibly during the early T Tauri phase, when the stellar magnetic field is stronger than 103 G.
Lai Dong [Department of Astronomy, Cornell University, Ithaca, NY 14850 (United States)
2012-09-20
The unipolar induction DC circuit model, originally developed by Goldreich and Lynden-Bell for the Jupiter-Io system, has been applied to different types of binary systems in recent years. We show that there exists an upper limit to the magnetic interaction torque and energy dissipation rate in such a model. This arises because when the resistance of the circuit is too small, the large current flow severely twists the magnetic flux tube connecting the two binary components, leading to the breakdown of the circuit. Applying this limit, we find that in coalescing neutron star binaries, magnetic interactions produce negligible correction to the phase evolution of the gravitational waveform, even for magnetar-like field strengths. However, energy dissipation in the binary magnetosphere may still give rise to electromagnetic radiation prior to the final merger. For ultracompact white dwarf binaries, we find that unipolar induction does not provide adequate energy dissipation to explain the observed X-ray luminosities of several sources. For exoplanetary systems containing close-in Jupiters or super-Earths, the magnetic torque and energy dissipation induced by the orbital motion are negligible, except possibly during the early T Tauri phase, when the stellar magnetic field is stronger than 10{sup 3} G.
NASA Astrophysics Data System (ADS)
Sakurai, Atsushi; Zhao, Bo; Zhang, Zhuomin M.
2014-12-01
Metamaterial thermal emitters and absorbers have been widely studied for different geometric patterns by exciting a variety of electromagnetic resonances. A resistor-inductor-capacitor (RLC) circuit model is developed to describe the magnetic resonances (i.e. magnetic polaritons) inside the structures. The RLC circuit model allows the prediction of not only the resonance frequency, but also the full width at half maximum and quality factor for various geometric patterns. The parameters predicted by the RLC model are compared with the finite-difference time-domain simulation. The magnetic field distribution and the power dissipation density profile are also used to justify the RLC circuit model. The geometric effects on the resonance characteristics are elucidated in the wire (or strip), cross, and square patterned metamaterial in the infrared region. This study will facilitate the design of metamaterial absorbers and emitters based on magnetic polaritons.
Modeling Advanced Avalanche Effects for Bipolar Transistor Circuit Design
Technische Universiteit Delft
Modeling Advanced Avalanche Effects for Bipolar Transistor Circuit Design Vladimir Milovanovi operating frequency and high output power of modern bipolar transistor circuits increase, designers are trying to exploit transistor operating regions where they would be able satisfy both conditions, namely
NASA Astrophysics Data System (ADS)
Narita, Katsuyuki; Yamada, Takashi; Sakashita, Yoshiyuki; Akatsu, Kan
The high-flux permanent magnet and flux-barrier structure of permanent magnet synchronous machine (PMSM) has strong magnetic saturation and harmonics components. When control algorithms for such machines are examined by performing control simulation, the use of the conventional motor model based on the voltage equation can cause problems. To avoid these problems, we introduce the technique of coupled analysis of the magnetic-field-control/circuit simulation. Further, iron losses generated in PMSM can be estimated by the coupled analysis system. The iron losses at various driving conditions are calculated by the coupled analysis system and are compared with measured losses. The comparison results show that the coupled analysis system is suitable for accurately estimating the iron losses of PMSM.
NSDL National Science Digital Library
Integrated Teaching and Learning Program,
Students are introduced to several key concepts of electronic circuits. They learn about some of the physics behind circuits, the key components in a circuit and their pervasiveness in our homes and everyday lives. Students learn about Ohm's law and how it is used to analyze circuits.
Jung, I.S.; Hur, J.; Hyun, D.S.
1999-09-01
Permanent magnet linear synchronous motors (PMLSM's) are proposed for many applications ranging from ground transportation to servo system and conveyance system. In this paper, the fields and forces of permanent magnet linear synchronous motor (PMLSM) with segmented or skewed magnet arrangement are analyzed according to length of segment or skew. And, the effects according to the lateral overhang of magnet are investigated. For the analysis, 3-dimensional equivalent magnetic circuit network (3-D EMCN) method is used. The analysis results are compared with the experimental ones and shown a reasonable agreement.
The Design of a RapidDischarge Varistor System for the MICE Magnet Circuits
Green, Michael A.
2008-07-23
The need for a magnet circuit discharge system, in order to protect the magnet HTS leads during a power failure, has been discussed in recent MICE reports [1], [2]. In order to rapidly discharge a magnet, one has to put enough resistance across the lead. The resistance in this case is varistor that is put across the magnet in the event of a power outage. The resistance consists of several diodes, which act as constant voltage resistors and the resistance of the cables connecting the magnets in the circuit to each other and to the power supply. In order for the rapid discharge system to work without quenching the magnets, the voltage across the magnets must be low enough so that the diodes in the quench protection circuit don't fire and cause the magnet current to bypass the superconducting coils. It is proposed that six rapid discharge varistors be installed across the three magnet circuits the power the tracker solenoids, which are connected in series. The focusing magnets, which are also connected in series would have three varistors (one for each magnet). The coupling magnets would have a varistor for each magnet. The peak voltage that is allowed per varistor depends on the number of quench protection diodes that make up the quench protection circuit for each magnet coil circuit. It is proposed that the varistors be water cooled as the magnet circuits are being discharged through them. The water cooling circuit can be supplied with tap water. The tap water flows only when the varistor temperature reaches a temperature of 45 C.
Computation of magnetic suspension of maglev systems using dynamic circuit theory
NASA Technical Reports Server (NTRS)
He, J. L.; Rote, D. M.; Coffey, H. T.
1992-01-01
Dynamic circuit theory is applied to several magnetic suspensions associated with maglev systems. These suspension systems are the loop-shaped coil guideway, the figure-eight-shaped null-flux coil guideway, and the continuous sheet guideway. Mathematical models, which can be used for the development of computer codes, are provided for each of these suspension systems. The differences and similarities of the models in using dynamic circuit theory are discussed in the paper. The paper emphasizes the transient and dynamic analysis and computer simulation of maglev systems. In general, the method discussed here can be applied to many electrodynamic suspension system design concepts. It is also suited for the computation of the performance of maglev propulsion systems. Numerical examples are presented in the paper.
Lumped circuit model of RF amplifier for SPICE simulator
NASA Astrophysics Data System (ADS)
Opalska, Katarzyna
2014-11-01
The paper presents the lumped model of RF amplifier for the generic SPICE circuit simulator. Model is constructed on the basis of measured s-parameter data set of the amplifier. Data - transformed to admittance (y) domain - is approximated by rational functions, which later are synthesized as RLC (sub)circuits. Final amplifier model - obtained by representing Y matrix of two-port circuit by the set of passive components and controlled voltage/current sources - is shown to be equivalent to the original s-based model and may be used in any generic circuit simulator.
CMOS Interface Circuits for Spin Tunneling Junction Based Magnetic Random Access Memories
Ganesh Saripalli
2002-12-31
Magneto resistive memories (MRAM) are non-volatile memories which use magnetic instead of electrical structures to store data. These memories, apart from being non-volatile, offer a possibility to achieve densities better than DRAMs and speeds faster than SRAMs. MRAMs could potentially replace all computer memory RAM technologies in use today, leading to future applications like instan-on computers and longer battery life for pervasive devices. Such rapid development was made possible due to the recent discovery of large magnetoresistance in Spin tunneling junction devices. Spin tunneling junctions (STJ) are composite structures consisting of a thin insulating layer sandwiched between two magnetic layers. This thesis research is targeted towards these spin tunneling junction based Magnetic memories. In any memory, some kind of an interface circuit is needed to read the logic states. In this thesis, four such circuits are proposed and designed for Magnetic memories (MRAM). These circuits interface to the Spin tunneling junctions and act as sense amplifiers to read their magnetic states. The physical structure and functional characteristics of these circuits are discussed in this thesis. Mismatch effects on the circuits and proper design techniques are also presented. To demonstrate the functionality of these interface structures, test circuits were designed and fabricated in TSMC 0.35{micro} CMOS process. Also circuits to characterize the process mismatches were fabricated and tested. These results were then used in Matlab programs to aid in design process and to predict interface circuit's yields.
Quantum Computation Beyond the Circuit Model
Stephen P. Jordan
2008-09-13
The quantum circuit model is the most widely used model of quantum computation. It provides both a framework for formulating quantum algorithms and an architecture for the physical construction of quantum computers. However, several other models of quantum computation exist which provide useful alternative frameworks for both discovering new quantum algorithms and devising new physical implementations of quantum computers. In this thesis, I first present necessary background material for a general physics audience and discuss existing models of quantum computation. Then, I present three results relating to various models of quantum computation: a scheme for improving the intrinsic fault tolerance of adiabatic quantum computers using quantum error detecting codes, a proof that a certain problem of estimating Jones polynomials is complete for the one clean qubit complexity class, and a generalization of perturbative gadgets which allows k-body interactions to be directly simulated using 2-body interactions. Lastly, I discuss general principles regarding quantum computation that I learned in the course of my research, and using these principles I propose directions for future research.
Low depth quantum circuits for Ising models
Iblisdir, S., E-mail: iblisdir@ecm.ub.edu [Dept. Estructura i Constituents de la Matèria, Universitat de Barcelona, 08028 Barcelona (Spain); Cirio, M. [Centre for Engineered Quantum Systems, Department of Physics and Astronomy, Macquarie University, North Ryde, NSW 2109 (Australia)] [Centre for Engineered Quantum Systems, Department of Physics and Astronomy, Macquarie University, North Ryde, NSW 2109 (Australia); Boada, O. [Physics of Information Group, Instituto de Telecomunicações, P-1049-001 Lisbon (Portugal)] [Physics of Information Group, Instituto de Telecomunicações, P-1049-001 Lisbon (Portugal); Brennen, G.K., E-mail: gavin.brennen@mq.edu.au [Centre for Engineered Quantum Systems, Department of Physics and Astronomy, Macquarie University, North Ryde, NSW 2109 (Australia)
2014-01-15
A scheme for measuring complex temperature partition functions of Ising models is introduced. Two applications of this scheme are presented. First, through appropriate Wick rotations, those amplitudes can be analytically continued to yield estimates for partition functions of Ising models. Bounds on the estimated error are provided through a central-limit theorem whose validity extends beyond the present context; it holds for example for estimations of the Jones polynomial. The kind of state preparations and measurements involved in this application can be made independent of the system size or the parameters of the system being simulated. Second, the scheme allows to accurately estimate non-trivial invariants of links. Another result concerns the computational power of estimations of partition functions for real temperature classical ferromagnetic Ising models. We provide conditions under which estimating such partition functions allows to reconstruct scattering amplitudes of quantum circuits, making the problem BQP-hard. We also show fidelity overlaps for ground states of quantum Hamiltonians, which serve as a witness to quantum phase transitions, can be estimated from classical Ising model partition functions. Finally, we discuss how accurate corner magnetisation measurements on thermal states of two-dimensional Ising models lead to fully polynomial random approximation schemes (FPRAS) for the partition function.
Design, modeling, and analysis of integrated magnetics for power converters
David Ki-Wai Cheng; Leung-Pong Wong; Yim-Shu Lee
2000-01-01
Some guidelines on the synthesis of integrated magnetics are introduced. Potential problems of integrated magnetics are identified. PSpice models are developed for computer-aided analysis and design purposes. A boost-flyback SSIPP (single-stage isolated power-factor-corrected power supply) with regenerative clamping is used as an example circuit to verify the application and performance of integrated magnetics
Short-Circuit Modeling of a Wind Power Plant: Preprint
Muljadi, E.; Gevorgian, V.
2011-03-01
This paper investigates the short-circuit behavior of a WPP for different types of wind turbines. The short-circuit behavior will be presented. Both the simplified models and detailed models are used in the simulations and both symmetrical faults and unsymmetrical faults are discussed.
ERIC Educational Resources Information Center
Borges, A. Tarciso; Gilbert, John K.
1998-01-01
Investigates the mental models that people construct about magnetic phenomena. Involves students, physics teachers, engineers, and practitioners. Proposes five models following a progression from simple description to a field model. Contains 28 references. (DDR)
NASA Technical Reports Server (NTRS)
Penfield, P., Jr.; Peterson, D. F.; Steinbrecher, D. H.
1972-01-01
A nonlinear circuit model for avalanche diodes is proposed. The model was derived by assuming that the bias dependence of the elements in a known small-signal equivalent-circuit model for existing diodes arises in a manner consistent with the theory of an idealized Read-type device. The model contains a nonlinear R-L branch, a controlled source, and a linear depletion capacitance. The model is used in the nearly linear sense to predict intermodulation distortion and gain compression in avalanche diode amplifiers. Computed results for amplifiers with existing diodes are shown to be in good agreement with experiment.
An improved equivalent circuit model of radial mode piezoelectric transformer.
Huang, Yihua; Huang, Wei
2011-05-01
In this paper, both the equivalent circuit models of the radial mode and the coupled thickness vibration mode of the radial mode piezoelectric transformer are deduced, and then with the Y-parameter matrix method and the dual-port network theory, an improved equivalent circuit model for the multilayer radial mode piezoelectric transformer is established. A radial mode transformer sample is tested to verify the equivalent circuit model. The experimental results show that the model proposed in this paper is more precise than the typical model. PMID:21622062
An equivalent circuit grid model for no-insulation HTS pancake coils
NASA Astrophysics Data System (ADS)
Wang, Y.; Song, H.; Xu, D.; Li, Z. Y.; Jin, Z.; Hong, Z.
2015-04-01
An equivalent circuit grid (ECG) model is proposed to analyse the time-varying characteristics of no-insulation (NI) ReBCO pancake coils. In the model, each turn of the coil is subdivided into fine elements in the azimuthal direction, and each element is equivalent to a circuit parameter. Then, the coil is equivalent to a circuit grid. A math model based on Kirchhoff’s law is proposed to solve the circuit grid model. The distribution of the electrical current inside the NI coil is analysed for the charging and discharging process. A finite element method (FEM) model is coupled to calculate the magnetic field induced by the coil. To validate the model, a double pancake (DP) coil is fabricated by coated conductor ReBCO tapes. Charging and discharging tests are performed on the coil at 77 K. The results from simulations and experiments exhibit a good agreement. Then, this model is used for more studies on the current distribution inside the NI coil in the charging and discharging process. The charging and discharging delay of NI coil is analysed and explained by the model. The model can also be applied to partial insulated (PI) coils and magnets consisting of NI coils.
Parameterized modeling of multiport passive circuit blocks
Mahmood, Zohaib
2010-01-01
System level design optimization has recently started drawing the attention of circuit designers. A system level optimizer would search over the entire design space, adjusting the parameters of interest, for optimal ...
Vahid Abbasi; Ahmad Gholami; Kaveh Niayesh
2012-01-01
A 3-D transient model has been developed to investigate plasma current deformation driven by internal and external magnetic fields and their influences on arc stability in a circuit breaker. The 3-D distribution of electric current density is obtained by solving the current continuity equation along with the generalized Ohm's law in the presence of an external magnetic field, while a
Physical modelling of vertical DMOS power transistors for circuit simulation
NASA Astrophysics Data System (ADS)
Andersson, M.; Kuivalainen, P.
1994-01-01
A physical model for vertical DMOS power transistors is presented. The model takes into account various short channel effects in the DMOS channel region and the velocity saturation and the exact device geometry in the drift region. The model, aimed at computer aided design of power integrated circuits, has been implemented in the APLAC circuit simulator. A good agreement between the measured and simulated results for vertical DMOSTs is demonstrated.
From the Biot-Savart Law to Ampere's Magnetic Circuital Law via Synthetic Differential Geometry
Hirokazu Nishimura
2014-01-31
It is well known in classical electrodynamics that the magnetic field given by a current loop and the electric field caused by the corresponding dipoles in sheets are very similar, as far as we are far away from the loop, which enables us to deduce Ampere's magnetic circuital law from the Biot-Savart law easily. The principal objective in this paper is to show that synthetic differential geometry, in which nilpotent infinitesimals are in abundance, furnishes out a natural framework for the exquisite formulation and its demonstration. This similitude in heaven enables us to transit from the Biot-Savart law to Ampere's magnetic circuital law like a shot on earth.
Note on homological modeling of the electric circuits
Eugen Paal; Märt Umbleja
2014-06-23
Based on a simple example, it is explained how the homological analysis may be applied for modeling of the electric circuits. The homological branch, mesh and nodal analyses are presented. Geometrical interpretations are given.
Modeling of three dimensional defects in integrated circuits
Dani, Sameer Manohar
1993-01-01
Although the majority of defects found in manufacturing lines of Integrated Circuits [ IC's] have predominantly 2- Dimensional [2D] effects, there are many situations in which 2D defect models do not suffice) e.g., tall layer bulks disrupting...
A Wide Bandwidth Model for the Electrical Impedance of Magnetic BearingS
NASA Technical Reports Server (NTRS)
Meeker, David C.; Maslen, Eric H.; Noh, Myounggyu D.
1996-01-01
Magnetic bearings are often designed using magnetic circuit theory. When these bearings are built, however, effects not included in the usual circuit theory formulation have a significant influence on bearing performance. Two significant sources of error in the circuit theory approach are the neglect of leakage and fringing effects and the neglect of eddy current effects. This work formulates an augmented circuit model in which eddy current and flux leakage and fringing effects are included. Through the use of this model, eddy current power losses and actuator bandwidth can be derived. Electrical impedance predictions from the model are found to be in good agreement with experimental data from a typical magnetic bearing.
Application of Neural Networks for Integrated Circuit Modeling
Xi Chen; Gao-Feng Wang; Wei Zhou; Qing-Lin Zhang; Jiang-feng Xu
2006-01-01
\\u000a Application of feedforward neural networks for integrated circuit (IC) modeling is presented. In order to accurately describe\\u000a IC behaviors, a set of improved equations for dynamic feedforward neural networks has been utilized for IC modeling. The rationality\\u000a of the improved equations is elucidated by analyzing the relation between the circuits and the equation parameters. Through\\u000a some special choices of the
A statistical MOSFET modeling method for CMOS integrated circuit simulation
Chen, Jian
1992-01-01
A STATISTICAL MOSFET MODELING METHOD FOR CMOS IN'I'EGRATED CIRCUIT SIMULATION A Thesis by JIAN CHEN Submitted to the Office of Graduate Studies of Texas AE~M University in partial fulfillment of the requirements for the degree of MASTER... OF SCIENCE August l 99'2 Major Sub ject: Electrical Engineering A STATISTICAL MOSFET MODELING METHOD FOR CMOS INTEGRATED CIRCUIT SIMULATION A Thesis by JIAN CHEN Approved as to style and content by: H. Maciej . Styblinski ) (Chair of Committee...
Digital Quantum Rabi and Dicke Models in Superconducting Circuits
Mezzacapo, A.; Las Heras, U.; Pedernales, J. S.; DiCarlo, L.; Solano, E.; Lamata, L.
2014-01-01
We propose the analog-digital quantum simulation of the quantum Rabi and Dicke models using circuit quantum electrodynamics (QED). We find that all physical regimes, in particular those which are impossible to realize in typical cavity QED setups, can be simulated via unitary decomposition into digital steps. Furthermore, we show the emergence of the Dirac equation dynamics from the quantum Rabi model when the mode frequency vanishes. Finally, we analyze the feasibility of this proposal under realistic superconducting circuit scenarios. PMID:25500735
Digital quantum Rabi and Dicke models in superconducting circuits.
Mezzacapo, A; Las Heras, U; Pedernales, J S; DiCarlo, L; Solano, E; Lamata, L
2014-01-01
We propose the analog-digital quantum simulation of the quantum Rabi and Dicke models using circuit quantum electrodynamics (QED). We find that all physical regimes, in particular those which are impossible to realize in typical cavity QED setups, can be simulated via unitary decomposition into digital steps. Furthermore, we show the emergence of the Dirac equation dynamics from the quantum Rabi model when the mode frequency vanishes. Finally, we analyze the feasibility of this proposal under realistic superconducting circuit scenarios. PMID:25500735
NASA Astrophysics Data System (ADS)
Abbasi, V.; Gholami, A.; Niayesh, K.
2012-10-01
A three-dimensional (3D) transient model is developed to investigate plasma current deformation driven by internal and external magnetic fields and their influences on arc stability in a circuit breaker. The 3D distribution of electric current density is obtained by solving the current continuity equation along with the generalized Ohm's law in the presence of an external magnetic field, while the magnetic field induced by the current flowing through the arc column is calculated by the magnetic vector potential equation. The applied external field imposes a rotational electromagnetic force on the arc and influences the plasma current deformation, which is discussed in this paper. In SF6 circuit breakers when gas interacts with the arc column, the fundamental equations such as Ampere's law, Ohm's law, turbulence model, transport equations of mass, momentum, and energy of plasma flow have to be coupled for analysing the phenomenon. The coupled interactions between the arc and the plasma flow are described within the framework of magnetohydrodynamic equations in conjunction with a K-? turbulence model. Simulations are focused on sausage and kink instabilities in the plasma (these phenomena are related to the electromagnetic field distribution and define the plasma deformations). The 3D simulation reveals the relation between plasma current deformation and instability phenomena, which affects the arc stability during the operation. Plasma current deformation is a consequence of coupling between electromagnetic forces (resulting from internal and radial external magnetic fields) and the plasma flow that are described in the simulations.
HID-lamp igniter using a two-stage magnetic-pulse-compression circuit
H. Kakehashi; M. Habu; T. Ninomiya; H. Ogasawara; Y. Ohta
1998-01-01
This paper proposes a high-intensity-discharge (HID) lamp igniter using a two-stage magnetic-pulse compression (MPC) circuit. The circuit operation is analyzed, and an optimal design procedure for selecting the saturable reactors and energy-storage capacitors is derived. Experimental verification is also given. This igniter can generate voltage pulses whose peak value and pulse width are 50 kV and 800 ns, respectively
SIMPEL: Circuit model for photonic spike processing laser neurons.
Shastri, Bhavin J; Nahmias, Mitchell A; Tait, Alexander N; Wu, Ben; Prucnal, Paul R
2015-03-23
We propose an equivalent circuit model for photonic spike processing laser neurons with an embedded saturable absorber-a simulation model for photonic excitable lasers (SIMPEL). We show that by mapping the laser neuron rate equations into a circuit model, SPICE analysis can be used as an efficient and accurate engine for numerical calculations, capable of generalization to a variety of different types of laser neurons with saturable absorber found in literature. The development of this model parallels the Hodgkin-Huxley model of neuron biophysics, a circuit framework which brought efficiency, modularity, and generalizability to the study of neural dynamics. We employ the model to study various signal-processing effects such as excitability with excitatory and inhibitory pulses, binary all-or-nothing response, and bistable dynamics. PMID:25837141
Altarawneh, Moaz M [Los Alamos National Laboratory; Mielke, Charles H [Los Alamos National Laboratory
2009-01-01
A new radio frequency oscillator circuit based on a proximity detector integrated circuit is described as an alternative for the traditional tunnel diode oscillator used for pulsed magnetic field measurements at low temperatures. The new circuit has been successfully applied to measure the superconducting upper critical field in Ba{sub 0.55}K{sub 0.45}Fe{sub 2}As{sub 2} single crystfl.ls up to 60 T. The new circuit design avoids many of the problems associated with tunnel diode circuits while keeping the advantages of contact less measurements in pulsed magnets.
Electrochemical circuit model of a PEM fuel cell
P. Famouri; Randall S. Gemmen
2003-01-01
A dynamic circuit model for a fuel cell is presented. The model accounts for flow transients, the reactant partial pressures, as well as loss mechanisms within the fuel cell. For a selected PEM fuel cell design, analyses are performed to examine load transients imposed on the fuel cell. The PSpice programming environment was employed. Such model capability is required to
Parallel LC circuit model for multi-band absorption and preliminary design of radiative cooling.
Feng, Rui; Qiu, Jun; Liu, Linhua; Ding, Weiqiang; Chen, Lixue
2014-12-15
We perform a comprehensive analysis of multi-band absorption by exciting magnetic polaritons in the infrared region. According to the independent properties of the magnetic polaritons, we propose a parallel inductance and capacitance(PLC) circuit model to explain and predict the multi-band resonant absorption peaks, which is fully validated by using the multi-sized structure with identical dielectric spacing layer and the multilayer structure with the same strip width. More importantly, we present the application of the PLC circuit model to preliminarily design a radiative cooling structure realized by merging several close peaks together. This omnidirectional and polarization insensitive structure is a good candidate for radiative cooling application. PMID:25607485
Coupled model of a magnetic actuator controlling a hydraulic cylinder and load
John R. Brauer
2002-01-01
Magnetic pressures on nonlinear steel are shown to have lower values than typical hydraulic pressures and, thus, small magnetic actuators are often coupled to hydraulic circuits. A new method of modeling a typical electrical\\/magnetic\\/hydraulic\\/mechanical system is described. Results of electromagnetic finite-element analysis of a magnetic actuator are used in a SPICE circuit that contains the differential equations of a hydraulic
Probabilistic Model of Fault Detection in Quantum Circuits
NASA Astrophysics Data System (ADS)
Banerjee, A.; Pathak, A.
Since the introduction of quantum computation, several protocols (such as quantum cryptography, quantum algorithm, quantum teleportation) have established quantum computing as a superior future technology. Each of these processes involves quantum circuits, which are prone to different kinds of faults. Consequently, it is important to verify whether the circuit hardware is defective or not. The systematic procedure to do so is known as fault testing. Normally testing is done by providing a set of valid input states and measuring the corresponding output states and comparing the output states with the expected output states of the perfect (fault less) circuit. This particular set of input vectors are known as test set [6]. If there exists a fault then the next step would be to find the exact location and nature of the defect. This is known as fault localization. A model that explains the logical or functional faults in the circuit is a fault model. Conventional fault models include (i) stuck at faults, (ii) bridge faults, and (iii) delay faults. These fault models have been rigorously studied for conventional irreversible circuit. But with the advent of reversible classical computing and quantum computing it has become important to enlarge the domain of the study on test vectors.
Circuit theory and model-based inference for landscape connectivity
Hanks, Ephraim M.; Hooten, Mevin B.
2013-01-01
Circuit theory has seen extensive recent use in the field of ecology, where it is often applied to study functional connectivity. The landscape is typically represented by a network of nodes and resistors, with the resistance between nodes a function of landscape characteristics. The effective distance between two locations on a landscape is represented by the resistance distance between the nodes in the network. Circuit theory has been applied to many other scientific fields for exploratory analyses, but parametric models for circuits are not common in the scientific literature. To model circuits explicitly, we demonstrate a link between Gaussian Markov random fields and contemporary circuit theory using a covariance structure that induces the necessary resistance distance. This provides a parametric model for second-order observations from such a system. In the landscape ecology setting, the proposed model provides a simple framework where inference can be obtained for effects that landscape features have on functional connectivity. We illustrate the approach through a landscape genetics study linking gene flow in alpine chamois (Rupicapra rupicapra) to the underlying landscape.
Seok-Myeong Jang; Seon-Ik Hwang; Kyoung-Jin Ko; Jang-Young Choi; So-Young Sung
2010-01-01
This paper deals with the method of driving performance evaluation of interior permanent magnet (IPM) motors with 6-pole NdFeB magnets rotor and 9-slot stator. The circuit parameters of IPM motor such as Ld(d-axis inductance), Lq(q-axis inductance), torque and speed are investigated using 2-d finite element analysis(FEA) in each current value with phase angle condition. The low speed region below the
NASA Astrophysics Data System (ADS)
Inoue, Kenta; Takeuchi, Naoki; Narama, Tatsuya; Yamanashi, Yuki; Yoshikawa, Nobuyuki
2015-04-01
Adiabatic quantum-flux-parametron (AQFP) logic is an energy-efficient superconductor logic with zero static power and very small dynamic power due to adiabatic switching operations. In order to build large-scale digital circuits, we built AQFP logic cells using superconductor magnetic shields, which are necessary in order to avoid unwanted magnetic couplings between the cells and excitation currents. In preliminary experimental tests, we confirmed that the unwanted coupling became negligibly small thanks to the superconductor shields. As a demonstration, we designed a four-to-one multiplexor and a 16-junction full adder using the shielded logic cells. In both circuits, we confirmed correct logic operations with wide operation margins of excitation currents. These results indicate that large-scale AQFP digital circuits can be realized using the shielded logic cells.
Structure-Preserving Model Order Reduction of RCL Circuit Equations
Freund, Roland W.
Structure-Preserving Model Order Reduction of RCL Circuit Equations Roland W. Freund Department of Mathematics, University of California at Davis, One Shields Avenue, Davis, CA 95616, U.S.A. freund compute reduced-order models that represent Pad´e #12;2 Roland W. Freund or matrix-Pad´e approximations [5
Timing model extraction for sequential circuits considering process variations
Bing Li; Ning Chen; Ulf Schlichtmann
2009-01-01
As semiconductor devices continue to scale down, process variations become more relevant for circuit design. Facing such variations, statistical static timing analysis is introduced to model variations more accurately so that the pessimism in traditional worst case timing analysis is reduced. Because all delays are modeled using correlated random variables, most statistical timing methods are much slower than corner based
Bipolar transistor modeling of avalanche generation for computer circuit simulation
R. W. Dutton
1975-01-01
An avalanche generation model is developed and incorporated into computer circuit analysis programs SLIC and NICAP. A modified form of Miller's empirical expression for generation is found to agree well with measured data for Western Electric and commercial n-p-n transistors. Measurement techniques and parameter determination for the three model coefficients are discussed. Equation constraints appropriate for computer implementation are presented.
Power semiconductor device modelling dedicated to circuit simulation
Philippe Leturcq
1999-01-01
The aim of this paper is to recall the problematics of circuit simulation in the field of power electronics and to critically review recent approaches to semiconductor device modelling for that purpose. In particular, as far as hardware problems are concerned, the discussion puts forward the need for physics-based models taking into account the distributed nature of charge carrier transport
A Neural Circuit Model of Flexible Sensorimotor Mapping: Learning
Columbia University
Neuron Article A Neural Circuit Model of Flexible Sensorimotor Mapping: Learning and Forgetting, CT 06520, USA *Correspondence: xjwang@yale.edu DOI 10.1016/j.neuron.2007.03.017 SUMMARY Volitional developed a bio- physically based decision-making network model of spiking neurons for arbitrary sensori
Short-Circuit Analysis of Permanent-Magnet Generators
Keith W. Klontz; Timothy J. E. Miller; Malcolm I. McGilp; Haran Karmaker; Peter Zhong
2011-01-01
Permanent-magnet generators (PMGs) have rapidly become important in renewable energy systems, portable and standby generating systems, and in many new applications in industrial, utility, aerospace, and automotive sectors. While there has been some discussion of \\
Equivalent-circuit calculations for built-up magnetic structures by projection method
A. A. Drozdov
1984-01-01
An equivalent circuit for a built-up multishell magnetic structure is developed by the method of projection. Such a structure contains three kinds of elements: segments of ferromagnetic material and joints between them with nonlinear characteristics and air gaps with linear ones. The gist of this method is to satisfy at each step any one of Kirchhoff's laws as well as
An excitable electronic circuit as a sensory neuron model
Medeiros, Bruno N S; Mindlin, Gabriel B; Copelli, Mauro; Leite, José R Rios
2011-01-01
An electronic circuit device, inspired on the FitzHugh-Nagumo model of neuronal excitability, was constructed and shown to operate with characteristics compatible with those of biological sensory neurons. The nonlinear dynamical model of the electronics quantitatively reproduces the experimental observations on the circuit, including the Hopf bifurcation at the onset of tonic spiking. Moreover, we have implemented an analog noise generator as a source to study the variability of the spike trains. When the circuit is in the excitable regime, coherence resonance is observed. At sufficiently low noise intensity the spike trains have Poisson statistics, as in many biological neurons. The transfer function of the stochastic spike trains has a dynamic range of 6 dB, close to experimental values for real olfactory receptor neurons.
External circuit integration with electromagnetic particle in cell modeling of plasma focus devices
NASA Astrophysics Data System (ADS)
Seng, Y. S.; Lee, P.; Rawat, R. S.
2015-03-01
The pinch performance of a plasma focus (PF) device is sensitive to the physical conditions of the breakdown phase. It is therefore essential to model and study the initial phase in order to optimize device performance. An external circuit is self consistently coupled to the electromagnetic particle in cell code to model the breakdown and initial lift phase of the United Nations University/International Centre for Theoretical Physics (UNU-ICTP) plasma focus device. Gas breakdown during the breakdown phase is simulated successfully, following a drop in the applied voltage across the device and a concurrent substantial rise in the circuit current. As a result, the plasma becomes magnetized, with the growing value of the magnetic field over time leading to the gradual lift off of the well formed current sheath into the axial acceleration phase. This lifting off, with simultaneous outward sheath motion along the anode and vertical cathode, and the strong magnetic fields in the current sheath region, was demonstrated in this work, and hence validates our method of coupling the external circuit to PF devices. Our method produces voltage waveforms that are qualitatively similar to the observed experimental voltage profiles of the UNU-ICTP device. Values of the mean electron energy before and after voltage breakdown turned out to be different, with the values after breakdown being much lower. In both cases, the electron energy density function turned out to be non-Maxwellian.
Multiwavelength Magnetic Field Modeling
NASA Astrophysics Data System (ADS)
Jaffe, T. R.
2015-03-01
We model the large-scale Galactic magnetic fields, including a spiral arm compression to generate anisotropic turbulence, by comparing polarized synchrotron and thermal dust emission. Preliminary results show that in the outer Galaxy, the dust emission comes from regions where the fields are more ordered than average while the situation is reversed in the inner Galaxy. We will attempt in subsequent work to present a more complete picture of what the comparison of these observables tells us about the distribution of the components of the magnetized ISM and about the physics of spiral arm shocks and turbulence.
Transmission Line and Equivalent Circuit Models for Plasmonic Waveguide Components
S. E. Kocabas; Georgios Veronis; David A. B. Miller; Shanhui Fan
2008-01-01
Modeling of waveguide junctions using transmission lines and lumped circuit elements is common practice in microwave networks. By the help of the scattering matrix formalism, it is possible to describe junction effects in a very concise way. Such a representation is crucial for the design of complex systems containing many interacting parts. Using scattering matrices, we characterize symmetric junctions between
Monte Carlo Reliability Model for Microwave Monolithic Integrated Circuits
Rubloff, Gary W.
Monte Carlo Reliability Model for Microwave Monolithic Integrated Circuits Aris Christou Materials of the failure rate of each component due to interaction effects of the failed components. The Monte Carlo failure rates become nonconstant. The Monte Carlo technique is an appropriate methodology used to treat
Real time railway traffic management modeling track-circuits
Paris-Sud XI, Université de
Real time railway traffic management modeling track-circuits Paola Pellegrini, Grégory Marlière.rodriguez@ifsttar.fr Abstract The real time railway traffic management seeks for the train routing and scheduling that minimize. 1998 ACM Subject Classification G.1.6 Optimization Keywords and phrases real time railway traffic
Short-circuit analysis of permanent-magnet generators
K. W. Klontz; T. J. E. Miller; H. Karmaker; P. Zhong
2009-01-01
Permanent-magnet generators (PMG) have rapidly become important in renewable energy systems, portable and standby generating systems, and in many new applications in industrial, utility, aerospace and automotive sectors. While there has been some discussion of ldquofault tolerance,rdquo and fault testing of an 8MW machine has recently been reported, understanding the behavior of faulted PMGs remains far from complete. This paper
Yield learning model for integrated circuit package
Balasubramaniam, Gaurishankar
1996-01-01
from chronic yield loss. . 5 Yield due to chronic yield loss. . 6 Time series model. . 7 Estimation of regression coefficients. . . 14 . 16 . 17 . 18 8 Impact of excursions. . . . 19 9 Effect of volume in line. . . . . . 20 10 Impact... of experience level. 11 Final spreadsheet model. . 12 Values for factors. . 21 . . . . 22 . . . . . 23 13 Final yield. . . . . . 24 14 Predicted yield - chronic and excursions. . . 25 15 Percentage rating for PQFP - absolute metric model. . . . . 16...
Approximation properties of a PWL circuit model of hysteresis
NASA Astrophysics Data System (ADS)
Cincotti, Silvano
2000-01-01
In this paper, some identification methods for a piece wise linear (PWL) circuit model of hysteresis phenomenon are presented and compared. The model provides a close prediction of static hysteresis and exhibits realistic dynamic features. The parameter identification problem can be solved by means of a suitable procedures based on representation theorem, on optimisation methods and on neural networks. Basic features are addressed and discussed.
A New Training Approach for Robust Recurrent Neural-Network Modeling of Nonlinear Circuits
Yi Cao; Qi-Jun Zhang
2009-01-01
A new approach for developing recurrent neural-network models of nonlinear circuits is presented, overcoming the conventional limitations where training information depends on the shapes of circuit waveforms and\\/or circuit terminations. Using only a finite set of waveforms for model training, our technique enables the trained model to respond accurately to test waveforms of unknown shapes. To relate information of training
NSDL National Science Digital Library
2012-08-03
This is a summative activity about magnets. Learners will observe a demonstration of the action of a magnet on a test tube of iron filings, answer questions, and, using the concepts learned in previous activities, write an essay about their understanding of the demonstration. This is the fourth activity in the Mapping Magnetic Influence educators guide. Learners should complete the other three activities in that guide (Seeing Magnetism, What Do You Know about Magnets, and Magnet Map) prior to beginning this activity.
Hongkui Li; Yan Li; Xi Sun; Dongxu Li; Youteng Jing
2009-01-01
This research studies the forces on the windings of transformer due to magnetic inrush current. These forces are compared with the corresponding forces due to short-circuit of the windings. Three dimensional finite element computation of three-phase power transformer is carried out based on the maximum permissible magnetic inrush current value where its amplitude is the same as the rated short-circuit
Enyuan Dong; Zhenwei Zhang; Huajun Dong; Chunen Fang
2011-01-01
The mechanism of high voltage circuit breaker required high reliability, recently, requirement for high voltage circuit breaker in phase-control technology need to be high controllability and low mechanical scatter. Traditional permanent magnetic actuator (PMA) and applied high-speed repulsion driver are just propitious to medium voltage and low voltage circuit breaker due to their terribly loss of magnetism on a large
An MOS transistor model for analog circuit design
A. I. A. Cunha; M. C. Schneider; C. Galup-Montoro
1998-01-01
This paper presents a physically based model for the metal-oxide-semiconductor (MOS) transistor suitable for analysis and design of analog integrated circuits. Static and dynamic characteristics of the MOS field-effect transistor are accurately described by single-piece functions of two saturation currents in all regions of operation. Simple expressions for the transconductance-to-current ratio, the drain-to-source saturation voltage, and the cutoff frequency in
Modeling of the Inductance of a Blumlein Circuit Spark Gap
NASA Astrophysics Data System (ADS)
Aboites, V.; Rendón, L.; Hernández, A. I.; Valdés, E.
2015-01-01
In this paper we present an analysis of the time-varying inductance in the spark gap of a Blumlein circuit. We assume several mathematical expressions to describe the inductance and compare theoretical and computational calculations with experimental results. The time-varying inductance is approximated by a constant, a straight line and two parables which differ in their concavity. This is the first time to our knowledge, in which the time-varying ignition inductance of a nitrogen laser is modeled.
Model of photovoltaic cell circuits under partial shading
Atsushi Kajihara; A. T. Harakawa
2005-01-01
The PV-cell and natural energy production systems have been much attracted. Together with global warning and extensive applications of solar power electric generation, defects on PV-cell under the partial shading become interesting technical issue. This paper investigates the equivalent circuit model and its characteristics under the partial shading condition. And we have clarified the mechanism of PV-cell under the partial
The lumped equivalent circuit model of the multi-passband tunable microwave magnetoelectric filters
NASA Astrophysics Data System (ADS)
Zhou, Hao-Miao; Lian, Jing; Zhu, Feng-Jie
2014-08-01
A magnetoelectric tunable microwave filter is proposed, which has multi-passband at corresponding frequencies when different magnetic fields are applied on multi-magnetoelectric laminates. A generalized lumped equivalent circuit model for the filter is established to predict the transmission characteristics. For existing experimental results of the microstrip filter with one magnetoelectric laminate put on the coupling microstrip lines, therefore the lumped circuit model is degraded. And the validity of the model is confirmed from the result that the predictions of the model are in good agreement with the results obtained by the electromagnetic simulation software and experimental results. Then, the performance of the multi-passband microwave filter with a plurality of magnetoelectric laminates is studied by the lumped equivalent circuit. It is found that any single band of multi-passband can be tunable through controlling the applied field on a block of magnetoelectric laminate, which can improve the practicability and flexibility of the bandpass filter. Moreover, when the same field is applied on the magnetoelectric laminates, the multi-passband will be combined into a single passband. The combined single passband has significantly larger bandwidth than the corresponding bandwidth of the filter, which has a single laminate with the same applied field, which can improve the bandpass effect obviously.
Computer model simulation of null-flux magnetic suspension and guidance
He, Jianliang; Rote, D.M.
1992-06-01
This paper discusses the magnetic force computations in a null-flux suspension system using dynamic circuit theory. A computer simulation model that can be used to compute magnetic forces and predict the system performance is developed on the basis of dynamic circuit theory. Numerical examples are presented to demonstrate the application of the model. The performance of the null-flux suspension system is simulated and discussed. 8 refs.
Computer model simulation of null-flux magnetic suspension and guidance
He, Jianliang; Rote, D.M.
1992-01-01
This paper discusses the magnetic force computations in a null-flux suspension system using dynamic circuit theory. A computer simulation model that can be used to compute magnetic forces and predict the system performance is developed on the basis of dynamic circuit theory. Numerical examples are presented to demonstrate the application of the model. The performance of the null-flux suspension system is simulated and discussed. 8 refs.
da Silva, Isaias; Horikawa, Oswaldo; Cardoso, Jose R; Camargo, Fernando A; Andrade, Aron J P; Bock, Eduardo G P
2011-05-01
In previous studies, we presented main strategies for suspending the rotor of a mixed-flow type (centrifugal and axial) ventricular assist device (VAD), originally presented by the Institute Dante Pazzanese of Cardiology (IDPC), Brazil. Magnetic suspension is achieved by the use of a magnetic bearing architecture in which the active control is executed in only one degree of freedom, in the axial direction of the rotor. Remaining degrees of freedom, excepting the rotation, are restricted only by the attraction force between pairs of permanent magnets. This study is part of a joint project in development by IDPC and Escola Politecnica of São Paulo University, Brazil. This article shows advances in that project, presenting two promising solutions for magnetic bearings. One solution uses hybrid cores as electromagnetic actuators, that is, cores that combine iron and permanent magnets. The other solution uses actuators, also of hybrid type, but with the magnetic circuit closed by an iron core. After preliminary analysis, a pump prototype has been developed for each solution and has been tested. For each prototype, a brushless DC motor has been developed as the rotor driver. Each solution was evaluated by in vitro experiments and guidelines are extracted for future improvements. Tests have shown good results and demonstrated that one solution is not isolated from the other. One complements the other for the development of a single-axis-controlled, hybrid-type magnetic bearing for a mixed-flow type VAD. PMID:21595710
Modelling and design for PM/EM magnetic bearings
NASA Technical Reports Server (NTRS)
Pang, D.; Kirk, J. A.; Anand, D. K.; Johnson, R. G.; Zmood, R. B.
1992-01-01
A mathematical model of a permanent magnet/electromagnet (PM/EM) radially active bearing is presented. The bearing is represented by both a reluctance model and a stiffness model. The reluctance model analyzes the magnetic circuit of the PM/EM bearings. By combining the two models, the performance of the bearing can be predicted given geometric dimensions, permanent magnet strength, and the parameters of the EM coils. The overall bearing design including the PM and EM design is subject to the performance requirement and physical constraints. A study of these requirements and constraints is discussed. The PM design is based on the required magnetic flux for proper geometric dimensions and magnet strength. The EM design is based on the stability and force slew rate consideration, and dictates the number of turns for the EM coils and the voltage and current of the power amplifier. An overall PM/EM bearing design methodology is proposed and a case study is also demonstrated.
AN EQUIVALENT CIRCUIT MODEL AND POWER CALCULATIONS FOR THE APS SPX CRAB CAVITIES
Kemner, Ken
/26/2011 Abstract An equivalent parallel resistor-inductor-capacitor (RLC) circuit with beam loading for a polarizedAN EQUIVALENT CIRCUIT MODEL AND POWER CALCULATIONS FOR THE APS SPX CRAB CAVITIES T. Berenc 1 as shown by 90deg. As in [1], an R/Q, which is useful for an equivalent circuit model for the dipole
Comparison of lumped parameter and finite element magnetic modeling in a brushless DC motor
J. P. Wang; D. K. Lieu; W. L. Lorimer; A. Hartman
1997-01-01
The FEM is a favored motor design tool for its high accuracy. Magnetic equivalent circuit analysis, an alternative to FEM, is becoming popular for its fair accuracy and quick repetition of computation. An equivalent circuit model of a brushless DC motor is developed and its ability to accurately predict various motor performance parameters is assessed
Lightning Modelling: From 3D to Circuit Approach
NASA Astrophysics Data System (ADS)
Moussa, H.; Abdi, M.; Issac, F.; Prost, D.
2012-05-01
The topic of this study is electromagnetic environment and electromagnetic interferences (EMI) effects, specifically the modelling of lightning indirect effects [1] on aircraft electrical systems present on deported and highly exposed equipments, such as nose landing gear (NLG) and nacelle, through a circuit approach. The main goal of the presented work, funded by a French national project: PREFACE, is to propose a simple equivalent electrical circuit to represent a geometrical structure, taking into account mutual, self inductances, and resistances, which play a fundamental role in the lightning current distribution. Then this model is intended to be coupled to a functional one, describing a power train chain composed of: a converter, a shielded power harness and a motor or a set of resistors used as a load for the converter. The novelty here, is to provide a pre-sizing qualitative approach allowing playing on integration in pre-design phases. This tool intends to offer a user-friendly way for replying rapidly to calls for tender, taking into account the lightning constraints. Two cases are analysed: first, a NLG that is composed of tubular pieces that can be easily approximated by equivalent cylindrical straight conductors. Therefore, passive R, L, M elements of the structure can be extracted through analytical engineer formulas such as those implemented in the partial element equivalent circuit (PEEC) [2] technique. Second, the same approach is intended to be applied on an electrical de-icing nacelle sub-system.
NASA Technical Reports Server (NTRS)
Flatley, Thomas W.; Henretty, Debra A.
1995-01-01
The Passive Aerodynamically Stabilized Magnetically Damped Satellite (PAMS) will be deployed from the Space Shuttle and used as a target for a Shuttle-mounted laser. It will be a cylindrical satellite with several corner cube reflectors on the ends. The center of mass of the cylinder will be near one end, and aerodynamic torques will tend to align the axis of the cylinder with the spacecraft velocity vector. Magnetic hysteresis rods will be used to provide passive despin and oscillation-damping torques on the cylinder. The behavior of the hysteresis rods depends critically on the 'B/H' curves for the combination of materials and rod length-to-diameter ratio ('l-over-d'). These curves are qualitatively described in most Physics textbooks in terms of major and minor 'hysteresis loops'. Mathematical modeling of the functional relationship between B and H is very difficult. In this paper, the physics involved is not addressed, but an algorithm is developed which provides a close approximation to empirically determined data with a few simple equations suitable for use in computer simulations.
Models wagging the dog: are circuits constructed with disparate parameters?
Nowotny, Thomas; Szücs, Attila; Levi, Rafael; Selverston, Allen I
2007-08-01
In a recent article, Prinz, Bucher, and Marder (2004) addressed the fundamental question of whether neural systems are built with a fixed blueprint of tightly controlled parameters or in a way in which properties can vary largely from one individual to another, using a database modeling approach. Here, we examine the main conclusion that neural circuits indeed are built with largely varying parameters in the light of our own experimental and modeling observations. We critically discuss the experimental and theoretical evidence, including the general adequacy of database approaches for questions of this kind, and come to the conclusion that the last word for this fundamental question has not yet been spoken. PMID:17571936
Hur, J.; Chun, Y.D.; Lee, J.; Hyun, D.S. [Hanyang Univ., Seoul (Korea, Republic of). Dept. of Electrical Engineering
1998-09-01
The distribution of radial force density in brushless permanent magnet DC motor is not uniform in axial direction. The analysis of radial force density has to consider the 3-D shape of teeth and overhand, because the radial force density causes vibration and acts on the surface of teeth inconstantly. For the analysis, a new 3-D equivalent magnetic circuit network method is used to account the rotor movement without remesh. The radial force density is calculated and analyzed by Maxwell stress tensor and discrete Fourier transform (DFT) respectively. The results of 3-D equivalent magnetic circuit method have been compared with the results of 3-D FEM.
NASA Astrophysics Data System (ADS)
Nguyen, Phuong-Bac; Choi, Seung-Bok
2011-12-01
This paper proposes a new approach to modeling the magnetic circuit of an MR brake and applies it to explore an engineering optimization problem. The MR brake used in this work is a bi-directional type whose range of braking torque varies from negative to positive values. The model of the bi-directional MR brake can be split into two components: the mechanical part and the magnetic circuit. While the mechanical part is modeled using Bingham's equation, an approach to modeling the magnetic circuit is proposed in this work. For verification of the effectiveness of this method, an optimal design aiming to minimize the mass subjected to the geometric and desired torque constraints is undertaken. In order to solve such an optimization problem, which consists of numerous constraints and potential local optima, a particle swarm optimization (PSO) algorithm in combination with a gradient-based repair method is proposed. The optimal solution of the problem obtained from the proposed method is then investigated and compared with that obtained from finite element analysis (FEA). In addition, an experiment on a manufactured bi-directional MR brake with the optimal parameters is undertaken to validate the accuracy of the proposed analysis methodology.
Modeling and simulation of insulated-gate field-effect transistor switching circuits
HAROLD SHICHMAN; DAVID A. HODGES
1968-01-01
A new equivalent circuit for the insulated-gate field-effect transistor (IGFET) is described. This device model is particularly useful for computer-aided analysis of monolithic integrated IGFET switching circuits. The results of computer simulations using the new equivalent circuit are in close agreement with experimental observations. As an example of a practical application, simulation results are shown for an integrated circuit IGFET
Circuit model for the explosive-driven plate generator
Caird, R.S.; Erickson, D.J.; Fowler, C.M.; Freeman, B.L.; Goforth, J.H.
1983-01-01
It is useful to model explosive-driven generators as lumped-parameter circuit elements in order to estimate performance in new applications and to optimize the design of experiments. The plate generator is essentially a parallel or tilted-plate transmission line in which the current-carrying flat-plate conductors are driven by plane-wave explosive systems. We have developed a simple model for the time-varying inductance of this system. First, an analytic expression is used to predict the plate motion. Then, the inductance is expressed as a function of plate separation to give the computational model. Time-dependent flux losses are accounted for by an increasing waste inductance. Model predictions are compared with the available shot data.
Ionospheric potential variability in global electric circuit models (Invited)
NASA Astrophysics Data System (ADS)
Mareev, E.; Volodin, E. M.; Kalinin, A.; Sllyunyaev, N.
2013-12-01
The ionospheric potential (IP) represents the electric voltage between the Earth's surface and the lower ionosphere and may be measured with a sufficient accuracy using the balloon soundings over the lowest 15-20 km. This parameter can serve as a global index relating the state of the global electric circuit (GEC) to the planetary climate. Exploring the GEC as a diagnostic tool for climate studies requires an accurate modeling of the IP stationary state and its dynamics, while a question of secular trend of the IP is still under discussion (Markson, 2007; Williams, 2009; Williams and Mareev, 2013). This paper addresses a possibility of correct calculation of the IP in 3D models of the GEC and its adequate parameterization to be used in General Circulation Models (GCM). Our approach is based on the use the integral representation for the contribution of charging currents, supporting the generators (in particular, electrified clouds) in the GEC, into the ionospheric potential (Kalinin et al., 2011; Mareeva et al., 2011). Simple enough analytical expressions for IP induced by the charging electric currents are suggested, including the contribution of the Austausch generator. We have developed also the spherical numerical model of the GEC and applied it for IP calculation for different-type cloud contribution into the circuit. A suggested IP parameterization is appropriate for the use in climate-model simulations (Mareev and Volodin, 2011). We use a high-resolution GCM of the atmosphere and ocean INMCM4.0 for the modeling the GEC. The main characteristics of the model are: atmosphere - 2x1.5 degrees in longitude and latitude, 21 levels; ocean - 1x0.5 degrees in longitude and latitude, 40 levels. We have taken into account quasi-stationary currents of electrified clouds as principal contributors into the DC global circuit. One of the most important aspects of this approach is an account for all the electrified clouds- both thunderstorms and electrified shower cloud. The results have shown that many of the calculated parameters are consistent with measurements on the global circuit, in particular, the diurnal and seasonal variability of the GEC. We found that the inter-annual variability of the IP is low and does not exceed 1% from the mean value. It should be emphasized however that it is correlated tightly with the mean SST in the Pacific ocean (180W-100W, 5S-5N - El-Nigno area). As to long-term trend, mumerical simulations suggest the IP decrease by about 10% for the XXI century if the global warming follows an assumed greenhouse gas emission scenario RCP 8.5. It is interesting that, using Price&Rind parameterizations, it was found that a mean flash rate is increasing by about 20% for the century (from 60 to 72 fl/s) for the same scenario. We conclude that the use of GCM with respective IP parameterizations allows us to study the influence of different factors on the GEC state, including convection intensity and its trends in a warmer climate. Some generalizations of the modeling related to the conductivity perturbations should lead to better description of the electrical generators in the global circuit.
Magnetic circuit of a contactless torque sensor for electric power steering
NASA Astrophysics Data System (ADS)
Fröhlich, Ekkehart; Jerems, Frank
Modern passenger cars are increasingly equipped with electromechanical steering assist rather than hydraulic systems known for many decades. Major benefits are reduced fuel consumption (up to 0.2l/100 km) and increased functionality. As such a system reacts to the drivers input in terms of steering torque or steering effort, a sensor is required that accurately measures the steering torque. Valeo has adopted a magnetic technology and has improved the performance by adding specially designed flux concentration devices. The magnetic circuit consists of a multi-pole ring magnet and a pair of ring-shaped soft magnetic parts rotating together with the steering shaft and an additional pair of soft magnetic flux concentration devices which are fixed stationary inside the housing. The steering torque causes a relative twist between magnet and the soft magnetic rings, therefore implementing a proportional magnetisation of the latter. A U-shape was chosen for the flux concentration devices in order to compensate mechanical tolerances of the system. The main focus of this paper will be on the tolerance behaviour of the sensor system and the impact of the flux concentration devices. Because of the nonlinear nature of the magnetisation curve of the NiFe alloy used extensive 3D FEM simulation was necessary. Simulation enables us to have a look inside the soft magnetic material and predict the spatial magnetisation distribution with the benefit of avoiding saturation. The result is an optimised sensor, which meets both the harsh environmental conditions inside the motor compartment as well as the cost pressure in the automotive business.
Simple model of a photoacoustic system as a CR circuit
NASA Astrophysics Data System (ADS)
Fukuhara, Akiko; Kaneko, Fumitoshi; Ogawa, Naohisa
2012-05-01
We introduce the photoacoustic educational system (PAES), by which we can identify which gas causes the greenhouse effect in a classroom (Kaneko et al 2010 J. Chem. Educ. 87 202-4). PAES is an experimental system in which a pulse of infrared (IR) is absorbed into gas as internal energy, an oscillation of pressure (sound) appears, and then we can measure the absorptance of IR by the strength of sound. In this paper, we construct a simple mathematical model for PAES which is equivalent to the CR circuit. The energy absorption of an IR pulse into gas corresponds to the charge of a condenser and the heat diffusion to the outside corresponds to the energy dissipation by electric resistance. We analyse the experimental results by using this simple model, and check its validity. Although the model is simple, it explains phenomena occurring in PAES and can be a good educational resource.
Analysis of an HID-lamp igniter using a two-stage magnetic-pulse-compression circuit
H. Kakehashil; M. Habu; T. Ninomiya; M. Shoyama; H. Ogasawara; Y. Ohta
1998-01-01
This paper proposes a high-intensity-discharge (HID) lamp igniter using a two-stage magnetic-pulse-compression (MPC) circuit. The circuit operation is analyzed and an optimal design procedure for selecting the saturable reactors and energy storage capacitors is derived. Experimental verification is also given. This igniter can generate voltage pulses whose peak value and pulse width are 50 kV and 800 ns, respectively
Delay modeling of bipolar ECL/EFL (Emitter-Coupled Logic/Emitter-Follower-Logic) circuits
NASA Astrophysics Data System (ADS)
Yang, Andrew T.
1986-08-01
This report deals with the development of a delay-time model for timing simulation of large circuits consisting of Bipolar ECL(Emitter-Coupled Logic) and EFL (Emitter-Follower-Logic) networks. This model can provide adequate information on the performance of the circuits with a minimum expenditure of computation time. This goal is achieved by the use of proper circuit transient models on which analytical delay expressions can be derived with accurate results. The delay-model developed in this report is general enough to handle complex digital circuits with multiple inputs or/and multiple levels. The important effects of input slew rate are also included in the model.
NASA Astrophysics Data System (ADS)
Peterchev, Angel V.; D?Ostilio, Kevin; Rothwell, John C.; Murphy, David L.
2014-10-01
Objective. This work aims at flexible and practical pulse parameter control in transcranial magnetic stimulation (TMS), which is currently very limited in commercial devices. Approach. We present a third generation controllable pulse parameter device (cTMS3) that uses a novel circuit topology with two energy-storage capacitors. It incorporates several implementation and functionality advantages over conventional TMS devices and other devices with advanced pulse shape control. cTMS3 generates lower internal voltage differences and is implemented with transistors with a lower voltage rating than prior cTMS devices. Main results. cTMS3 provides more flexible pulse shaping since the circuit topology allows four coil-voltage levels during a pulse, including approximately zero voltage. The near-zero coil voltage enables snubbing of the ringing at the end of the pulse without the need for a separate active snubber circuit. cTMS3 can generate powerful rapid pulse sequences (\\lt 10 ms inter pulse interval) by increasing the width of each subsequent pulse and utilizing the large capacitor energy storage, allowing the implementation of paradigms such as paired-pulse and quadripulse TMS with a single pulse generation circuit. cTMS3 can also generate theta (50 Hz) burst stimulation with predominantly unidirectional electric field pulses. The cTMS3 device functionality and output strength are illustrated with electrical output measurements as well as a study of the effect of pulse width and polarity on the active motor threshold in ten healthy volunteers. Significance. The cTMS3 features could extend the utility of TMS as a research, diagnostic, and therapeutic tool.
Song, G Hugh
2014-02-01
Based on complex-variable analysis of a Fabry-Perot resonator as a multimode nonsymmetric two-port waveguide device, two versions of equivalent-circuit configurations are presented: Starting from a renewed study on single-mode two-pole circuits, we develop two respective multimode equivalent circuits of an almost identical configuration: one for the reflection coefficient and the other for the pass-through transmission coefficient. In the mathematics language of complex-variable analysis, the two models successfully "approximate" the two scattering coefficients through two "uniformly converging" partial-fraction series expansions. PMID:24562041
HSPICE modelling of a solar array circuit controlled by a fet switch
NASA Technical Reports Server (NTRS)
Cox, Deanna D.; Natarajan, T.; Day, John
1987-01-01
This paper presents a method of modeling a solar array circuit controlled by a hexfet switch on HSPICE. HSPICE models are developed for the solar array current voltage (IV) characteristic and the IRF150 hexfet. Computer simulations are made to verify rate of current change at the load. The equivalent LC circuit for the same current control is modeled to show savings in weight and power in choosing the fet switch over an LC circuit.
Modeling of magnetic cloud expansion
NASA Astrophysics Data System (ADS)
Vandas, Marek; Romashets, Eugene; Geranios, Athanassios
2015-04-01
A model of an expanding elliptic cylindrical force-free flux rope is used to interpret in-situ magnetic cloud observations by spacecraft. Input quantities are measurements of magnetic field components and velocity magnitudes along a spacecraft trajectory inside a magnetic cloud. During the fitting procedure flux-rope geometric parameters and cloud expansion velocity are determined. Observed separate velocity components are not used in the fitting procedure, but in radial (expansion) velocity construction which is compared to model one to test our model more strictly. 24 magnetic clouds with clearly expressed expansion were fitted by the model. Radial velocity profiles qualitatively correspond to model ones in majority of cases (83%), in more than half of them (58%) quantitatively.
Micromagnetic model of magnetization reversal of magnetically hard ultrathin dots
Boyer, Edmond
Micromagnetic model of magnetization reversal of magnetically hard ultrathin dots and stripes M, France Abstract We propose improvements and extensions to an analytical model of magnetization reversal of nucleation volumes in hard magnetic materials, we use the concept of edge demagnetizing torque, where all
Sheath Equivalent Electrical Circuit Model for Equilibrium Child Sheath Description
NASA Astrophysics Data System (ADS)
Dwivedi, C. B.; Deka, U.; Sarma, A.
The Child-Langmuir law is well known in the fields of electronics and plasma physics. This has relevance to the analytical description of the space charge sheath limited current and its dependence on the space charge sheath width. For known values of the applied wall voltage, the current and width are two unknowns to be determined self-consistently and independently. The Child-Langmuir law alone is not sufficient for self-consistent description of the equilibrium Child sheath. Here we use the concept of sheath equivalent electrical circuit model and propose an idea of current equivalence principle to develop an additional equation which closes the usual Child sheath equation. Thereafter, we carry out self-consistent and independent determination of the Child sheath current and width. It is found that the steady state (time averaged) view of Kirchoff's law fulfils the closure property of the Child sheath equation and verifies the constant current approximation of conventional Child sheath description. The proposed idea of current equivalence principle states that the hydrodynamic and electrical circuit views of the Child sheath current are equivalent, which is supposed to govern the equilibrium and dynamic behaviors of the Child sheath.
Chapter II MOS Transistor Modelling for MMW Circuits ChapterChapterChapterChapter IIIIIIII
Paris-Sud XI, UniversitÃ© de
Chapter II MOS Transistor Modelling for MMW Circuits 15 ChapterChapterChapterChapter IIIIIIII MOS transistor model and layout issues One of the most important design issues in millimeter wave circuit design in modern MOS technologies is active devices and related parasitic elements modeling. The MOS transistor
Extraction of Gate Level Models from Transistor Circuits by FourValued Symbolic Analysis
Bryant, Randal E.
Extraction of Gate Level Models from Transistor Circuits by FourÂValued Symbolic Analysis Randal EÂlevel representation of an MOS transistor circuit. The resulting model contains only fourÂvalued unit and zero delay transistors, stored charge, and multiple signal strengths. It produces models with size comparable to ones
NASA Astrophysics Data System (ADS)
Xia, Chun; Keppens, Rony
2014-01-01
The magnetic configuration hosting prominences can be a large-scale helical magnetic flux rope. As a necessary step towards future prominence formation studies, we report on a stepwise approach to study flux rope formation. We start with summarizing our recent three-dimensional (3D) isothermal magnetohydrodynamic (MHD) simulation where a flux rope is formed, including gas pressure and gravity. This starts from a static corona with a linear force-free bipolar magnetic field, altered by lower boundary vortex flows around the main polarities and converging flows towards the polarity inversion. The latter flows induce magnetic reconnection and this forms successive new helical loops so that a complete flux rope grows and ascends. After stopping the driving flows, the system relaxes to a stable helical magnetic flux rope configuration embedded in an overlying arcade. Starting from this relaxed isothermal endstate, we next perform a thermodynamic MHD simulation with a chromospheric layer inserted at the bottom. As a result of a properly parametrized coronal heating, and due to radiative cooling and anisotropic thermal conduction, the system further relaxes to an equilibrium where the flux rope and the arcade develop a fully realistic thermal structure. This paves the way to future simulations for 3D prominence formation.
Experiments on Evolving Software Models of Analog Circuits
NASA Technical Reports Server (NTRS)
Lohn, Jason D.
1999-01-01
Analog circuits are of great importance in electronic system design since the world is fundamentally analog in nature. While the amount of digital design activity far outpaces that of analog design, most digital systems require analog modules for interfacing with the external world. It was recently estimated that approximately 60% of digital application- specific integrated circuit designs incorporated analog circuits. With challenging analog circuit design problems and few analog design engineers, there are economic reasons for automating the analog design process, especially time-to-market considerations. Techniques for analog circuit design automation began appearing about two decades ago. These methods incorporated heuristics [6], knowledge bases [1], simulated annealing [5], and other algorithms. Efforts using techniques from evolutionary computation began appearing over the last few years. These include the use of genetic algorithms to select electronic component values (for example, the resistance value of a resistor), to select circuit topologies, and to design amplifiers using a limited set of canned topologies [4]. A genetic programming-based analog circuit design system has been demonstrated in which the circuit sizes, component values, and the circuit topologies are determined automatically [3]. The genetic-algorithm systems typically represent circuit structures as vectors of parameters encoded in binary strings, while the genetic programming system manipulates tree data structures.
How to model connection wires in a circuit: From physical vector fields to circuit scalar quantities
NASA Astrophysics Data System (ADS)
Vandenbosch, Guy A. E.
2013-09-01
Starting from the basic equations of electromagnetism, Maxwell's equations, the concepts of inductive coupling in a loop and capacitive coupling between two pieces of wire are formally explained. Inductive coupling is linked to Faraday's law and capacitive coupling to the Ampere-Maxwell law. Capacitive coupling is also inherently linked to the phenomenon of surface charges, which has been recently studied thoroughly in the literature, especially in static situations. It is shown that, when applied to the connecting wires in a circuit at higher frequencies, simple circuit theory must be significantly modified in order to take into account the effects of the two types of coupling between the wires.
Maxwell's fluid model of magnetism
Robert Brady; Ross Anderson
2015-02-20
In 1861, Maxwell derived two of his equations of electromagnetism by modelling a magnetic line of force as a `molecular vortex' in a fluid-like medium. Later, in 1980, Berry and colleagues conducted experiments on a `phase vortex', a wave geometry in a fluid which is analogous to a magnetic line of force and also exhibits behaviour corresponding to the quantisation of magnetic flux. Here we unify these approaches by writing down a solution to the equations of motion for a compressible fluid which behaves in the same way as a magnetic line of force. We then revisit Maxwell's historical inspiration, namely Faraday's 1846 model of light as disturbances in lines of force. Using our unified model, we show that such disturbances resemble photons: they are polarised, absorbed discretely, obey Maxwell's full equations of electromagnetism to first order, and quantitatively reproduce the correlation that is observed in the Bell tests.
A functional circuit model of interaural time difference processing.
McColgan, Thomas; Shah, Sahil; Köppl, Christine; Carr, Catherine; Wagner, Hermann
2014-12-01
Inputs from the two sides of the brain interact to create maps of interaural time difference (ITD) in the nucleus laminaris of birds. How inputs from each side are matched with high temporal precision in ITD-sensitive circuits is unknown, given the differences in input path lengths from each side. To understand this problem in birds, we modeled the geometry of the input axons and their corresponding conduction velocities and latencies. Consistent with existing physiological data, we assumed a common latency up to the border of nucleus laminaris. We analyzed two biological implementations of the model, the single ITD map in chickens and the multiple maps of ITD in barn owls. For binaural inputs, since ipsi- and contralateral initial common latencies were very similar, we could restrict adaptive regulation of conduction velocity to within the nucleus. Other model applications include the simultaneous derivation of multiple conduction velocities from one set of measurements and the demonstration that contours with the same ITD cannot be parallel to the border of nucleus laminaris in the owl. Physiological tests of the predictions of the model demonstrate its validity and robustness. This model may have relevance not only for auditory processing but also for other computational tasks that require adaptive regulation of conduction velocity. PMID:25185809
Fuzzy modeling and synchronization of different memristor-based chaotic circuits
NASA Astrophysics Data System (ADS)
Wen, Shiping; Zeng, Zhigang; Huang, Tingwen; Chen, Yiran
2013-11-01
This Letter is concerned with the problem of fuzzy modeling and synchronization of memristor-based Lorenz circuits with memristor-based Chua's circuits. In this Letter, a memristor-based Lorenz circuit is set up, and illustrated by phase portraits and Lyapunov exponents. Furthermore, a new fuzzy model of memristor-based Lorenz circuit is presented to simulate and synchronize with the memristor-based Chua's circuit. Through this new fuzzy model, two main advantages can be obtained as: (1) only two linear subsystems are needed; (2) fuzzy synchronization of these two different chaotic circuits with different numbers of nonlinear terms can be achieved with only two sets of gain K. Finally, numerical simulations are used to illustrate the effectiveness of these obtained results.
Huang, Chi-Fang; Chao, Hsuan-Yi; Chang, Hsun-Hao; Lin, Xi-Zhang
2014-11-01
Abstract Based on the characteristics of cancer cells that cannot survive in an environment with temperature over 42?°C, a magnetic induction heating system for cancer treatment is developed in this work. First, the methods and analyses for designing the multi-cascaded coils magnetic induction hyperthermia system are proposed, such as internal impedance measurement of power generator, impedance matching of coils, and analysis of the system. Besides, characteristics of the system are simulated by a full-wave package for engineering optimization. Furthermore, by considering the safety factor of patients, a two-sectional needle is designed for hyperthermia. Finally, this system is employed to test the liver of swine in ex-vivo experiments, and through Hematoxylin and Eosin (H&E) stain and NADPH oxidase activity assay, the feasibility of this system is verified. PMID:25379959
A Simplified Electric Circuit Model for the Analysis of Hybrid Wind-Fuel Cell Systems
R. Chedid; F. B. Chaaban; R. Shihab
2007-01-01
This paper proposes a simulation methodology for a wind energy conversion system (WECS) incorporating fuel cells as a backup generator. A complete mathematical model for each component of the wind\\/fuel cell hybrid system is presented, and a simplified electric circuit is developed. The complete electric circuit is composed of two parts; the first part models a wind turbine driving a
Large-signal two-terminal device model for nanoelectronic circuit analysis
Garrett S. Rose; Matthew M. Ziegler; Mircea R. Stan
2004-01-01
As the nanoelectronics field reaches the maturity needed for circuit-level integration, modeling approaches are needed that can capture nonclassical behaviors in a compact manner. This paper proposes a universal device model (UDM) for two-terminal devices that addresses the challenge of correctly balancing accuracy, complexity, and flexibility. The UDM qualitatively captures fundamental classical and quantum phenomena and enables nanoelectronic circuit design
Single-pass beam measurements for the verification of the LHC magnetic model
Calaga, R.; Giovannozzi, M.; Redaelli, S.; Sun, Y.; Tomas, R.; Venturini-Delsolaro, W.; Zimmermann, F.
2010-05-23
During the 2009 LHC injection tests, the polarities and effects of specific quadrupole and higher-order magnetic circuits were investigated. A set of magnet circuits had been selected for detailed investigation based on a number of criteria. On or off-momentum difference trajectories launched via appropriate orbit correctors for varying strength settings of the magnet circuits under study - e.g. main, trim and skew quadrupoles; sextupole families and spool piece correctors; skew sextupoles, octupoles - were compared with predictions from various optics models. These comparisons allowed confirming or updating the relative polarity conventions used in the optics model and the accelerator control system, as well as verifying the correct powering and assignment of magnet families. Results from measurements in several LHC sectors are presented.
Burger, Tomáš; Lucová, Marcela; Moritz, Regina E.; Oelschläger, Helmut H. A.; Druga, Rastislav; Burda, Hynek; Wiltschko, Wolfgang; Wiltschko, Roswitha; N?mec, Pavel
2010-01-01
The neural substrate subserving magnetoreception and magnetic orientation in mammals is largely unknown. Previous experiments have demonstrated that the processing of magnetic sensory information takes place in the superior colliculus. Here, the effects of magnetic field conditions on neuronal activity in the rodent navigation circuit were assessed by quantifying c-Fos expression. Ansell's mole-rats (Fukomys anselli), a mammalian model to study the mechanisms of magnetic compass orientation, were subjected to natural, periodically changing, and shielded magnetic fields while exploring an unfamiliar circular arena. In the undisturbed local geomagnetic field, the exploration of the novel environment and/or nesting behaviour induced c-Fos expression throughout the head direction system and the entorhinal–hippocampal spatial representation system. This induction was significantly suppressed by exposure to periodically changing and/or shielded magnetic fields; discrete decreases in c-Fos were seen in the dorsal tegmental nucleus, the anterodorsal and the laterodorsal thalamic nuclei, the postsubiculum, the retrosplenial and entorhinal cortices, and the hippocampus. Moreover, in inactive animals, magnetic field intensity manipulation suppressed c-Fos expression in the CA1 and CA3 fields of the hippocampus and the dorsal subiculum, but induced expression in the polymorph layer of the dentate gyrus. These findings suggest that key constituents of the rodent navigation circuit contain populations of neurons responsive to magnetic stimuli. Thus, magnetic information may be integrated with multimodal sensory and motor information into a common spatial representation of allocentric space within this circuit. PMID:20219838
Suman Dwari; L eila Parsa; Thomas A. Lipo
2007-01-01
This paper presents optimal control of a five-phase Integrated Modular Permanent Magnet Motor for normal and open-circuit fault conditions. Finite element analysis of the motor is carried out to obtain output torque of the motor. It is found that the output torque ripple of the machine when supplied with sinusoidal currents is considerably high. An optimum control technique is presented
YI, YM; Hu, Chia-Ren.
1992-01-01
A previous study [C.-R. Hu and C.-H. Huang, Phys. Rev. B 43, 7718 (1991)] of the phase boundary T(c)(H) of a single-cube superconducting circuit in an external magnetic field H of arbitrary magnitude and direction is extended here to superconducting...
Yan-Ming Zhong; Shi-Jie Xiong
2007-01-01
We investigate the geometric phase produced by nonadiabatic transition of spin states at corners of mesoscopic square circuit with tilted magnetic field at its edges. From the Schrödinger equation, the transitions of electron spin state at corners are described by the transfer matrices. The eigenenergies and eigenstates are obtained from the cyclic condition and the multiplying of the transfer matrices.
Lunar magnetism. [primordial core model
NASA Technical Reports Server (NTRS)
Goldstein, M. L.
1975-01-01
It is shown, for a very simple model of the moon, that the existence of a primordial core magnetic field would give rise to a present day nonzero dipole external field. In the investigation a uniformly magnetized core embedded in a permeable mantle is considered. The significance of the obtained results for the conclusions reported by Runcorn (1975) is discussed. Comments provided by Runcorn to the discussion are also presented.
Dynamic models and model validation for PEM fuel cells using electrical circuits
Caisheng Wang; M. Hashem Nehrir; Steven R. Shaw
2005-01-01
This paper presents the development of dynamic models for proton exchange membrane (PEM) fuel cells using electrical circuits. The models have been implemented in MATLAB\\/SIMULINK and PSPICE environments. Both the double-layer charging effect and the thermodynamic characteristic inside the fuel cell are included in the models. The model responses obtained at steady-state and transient conditions are validated by experimental data
A Novel Prediction Method about Single Components of Analog Circuits Based on Complex Field Modeling
Tian, Shulin; Yang, Chenglin
2014-01-01
Few researches pay attention to prediction about analog circuits. The few methods lack the correlation with circuit analysis during extracting and calculating features so that FI (fault indicator) calculation often lack rationality, thus affecting prognostic performance. To solve the above problem, this paper proposes a novel prediction method about single components of analog circuits based on complex field modeling. Aiming at the feature that faults of single components hold the largest number in analog circuits, the method starts with circuit structure, analyzes transfer function of circuits, and implements complex field modeling. Then, by an established parameter scanning model related to complex field, it analyzes the relationship between parameter variation and degeneration of single components in the model in order to obtain a more reasonable FI feature set via calculation. According to the obtained FI feature set, it establishes a novel model about degeneration trend of analog circuits' single components. At last, it uses particle filter (PF) to update parameters for the model and predicts remaining useful performance (RUP) of analog circuits' single components. Since calculation about the FI feature set is more reasonable, accuracy of prediction is improved to some extent. Finally, the foregoing conclusions are verified by experiments. PMID:25147853
Zhou, Jingyu; Tian, Shulin; Yang, Chenglin
2014-01-01
Few researches pay attention to prediction about analog circuits. The few methods lack the correlation with circuit analysis during extracting and calculating features so that FI (fault indicator) calculation often lack rationality, thus affecting prognostic performance. To solve the above problem, this paper proposes a novel prediction method about single components of analog circuits based on complex field modeling. Aiming at the feature that faults of single components hold the largest number in analog circuits, the method starts with circuit structure, analyzes transfer function of circuits, and implements complex field modeling. Then, by an established parameter scanning model related to complex field, it analyzes the relationship between parameter variation and degeneration of single components in the model in order to obtain a more reasonable FI feature set via calculation. According to the obtained FI feature set, it establishes a novel model about degeneration trend of analog circuits' single components. At last, it uses particle filter (PF) to update parameters for the model and predicts remaining useful performance (RUP) of analog circuits' single components. Since calculation about the FI feature set is more reasonable, accuracy of prediction is improved to some extent. Finally, the foregoing conclusions are verified by experiments. PMID:25147853
Coupling effects throughout the solar atmosphere: 2. Model of energetically open circuit
NASA Astrophysics Data System (ADS)
Ryutova, M.
2006-09-01
EUV structures in the solar atmosphere are studied on the basis of the energetically open equivalent circuits. The systems consist of current carrying magnetic loops that interconnect a high ? energy-production region with a low ? dissipation region and include the transition region where the most efficient generation of currents and transport of the accumulated energy through the resistive stresses occurs. As nonconservative systems with a source and sink of energy, they may be driven into various dynamic forms via nonlinear processes with continuous flow of matter and energy. The corresponding equivalent circuit equation has the form of the Van der Pol oscillator. Depending on the coefficients determined by the system parameters, this equation describes different behaviors of the EUV structures including long-living steady loops with subtle oscillations, loops in the relaxation regime, and the periodically flaring and exploding loop systems. The model predicts that the EUV loops must have a filamentary structure and allows us to estimate the limiting currents and critical radii of elemental filaments associated with the stability criteria. Simple relations between the parameters, most of which are observables, may provide reliable diagnostic tools.
An engineering model of lower thalamo-cortico-basal ganglionic circuit function
Lim, Eugene J. (Eugene Jungsud), 1980-
2003-01-01
An engineering model of lower thalamo-cortico-basal ganglionic circuit functionality was extended and tested. This model attempts to explain the circuitry of the basal ganglia, examine its functional properties, and integrate ...
Speed Flexibility Biomedical Vision Model Using Analog Electronic Circuits and VLSI Layout Design
Masashi Kawaguchi; Shoji Suzuki; Takashi Jimbo; Naohiro Ishii
2009-01-01
We propose here an artificial vision model for the speed flexibility motion detection which uses analog electronic circuits\\u000a and design the analog VLSI layout. In the previous model, the range of speed is quite narrow. However, we use the variable\\u000a resistant parts inside the circuits. This model has speed flexibility property, and it is comprised of four layers. The model
Modeling Earth's magnetic field variation
NASA Astrophysics Data System (ADS)
Wardinski, I.
2012-12-01
Observations of the Earth's magnetic field taken at the Earth's surface and at satellite altitude have been combined to construct models of the geomagnetic field and its variation. Lesur et al. (2010) developed a kinematic reconstruction of core field changes that satisfied the frozen-flux constraint. By constraining the field evolution to be entirely due to advection of the magnetic field at the core surface it maintained the spatial complexity of the field morphology imposed by a satellite field model backward in time [Wardinski & Lesur,2012]. In this study we attempt a kinematic construction of future variation in Earth's magnetic field variation. Our approach, first seeks to identify typical time scales of the magnetic field and core surface flows present in decadal and millennial field and flow models. Therefore, the individual spherical harmonic coefficients are treated by methods of time series analysis. The second step employs stochastic modelling of the temporal variability of such spherical harmonic coefficients that represent the field and core surface flow. Difficulties arise due to the non-stationary behavior of the field and core surface flow. However, the broad behavior may consist of some homogeneity, which could be captured by a generalized stochastic model that calls for the d'th difference of the time series to be stationary (ARIMA-Model), or by detrending the coefficient time series. By computing stochastic models, we obtain two sets of field-forecasts, the first set is obtained from stochastic models of the Gauss coefficients. Here, first results suggest that secular variation on time scales shorter than 5 years behaves rather randomly and cannot be described sufficiently well by stochastic models. The second set is derived from forward modeling the secular variation using the diffusion-less induction equation (kinematic construction). This approach has not provide consistent results.
Saibal Mukhopadhyay; Arijit Raychowdhury; Kaushik Roy
2003-01-01
Dramatic increase of subthreshold, gate and reverse biased junction band-to-band-tunneling (BTBT) leakage in scaled devices, results in the drastic increase of total leakage power in a logic circuit. In this paper a methodology for accurate estimation of the total leakage in a logic circuit based on the compact modeling of the different leakage current in scaled devices has been developed.
High-Accuracy Emission Simulation Models for VLSI Chips including Package and Printed Circuit Board
Thomas Steinecke; Mehmet Goekcen; Dirk Hesidenz; Andreas Gstoettner
2007-01-01
The electromagnetic emission of complex very large scale integrated circuits is determined by their operation activity plus the manifold noise propagation paths through the on-chip power routing, the package traces and the planes and traces on the printed circuit board. The design of any emission test board influences the emission finally measured at defined probing connectors. Good simulation models have
Modeling the cosmic-ray-induced soft-error rate in integrated circuits: An overview
G. R. Srinivasan
1996-01-01
This paper is an overview of the concepts and methodologies used to predict soft-error rates (SER) due to cosmic and high-energy particle radiation in integrated circuit chips. The paper emphasizes the need for the SER simulation using the actual chip circuit model which includes device, process, and technology parameters as opposed to using either the discrete device simulation or generic
Design, modeling and synthesis of an in vitro transcription rate regulatory circuit
Murray, Richard M.
Design, modeling and synthesis of an in vitro transcription rate regulatory circuit Elisa Franco, mathematical mod- eling and synthesis emphin vitro of an RNA transcription rate regulatory circuit for quantitative analysis have been proposed in [8], where protein signaling patters are considere
4th Grade Students Investigate Electric Circuits Through Construction and Illustration
NSDL National Science Digital Library
As an activity related to FOSS unit Magnetism and Electricity, 4th grade science students use a computer download to explore electrical circuits and to generate illustrations of electrical circuits for physical models built in class
A current circuit model of pulsar radio emission
NASA Astrophysics Data System (ADS)
Kunzl, T.; Lesch, H.; Jessner, A.
We present the outline of a new model for the coherent radio emission of pulsars that succeeds in reproducing the energetics and brightness temperatures of the observed radio emission from the observationally deduced distances of 50-100 pulsar radii above the neutron star in a narrow region. The restrictions imposed by energy conservation, plasma dynamics of the coherent radiation process and propagation effects are used to apply the action of a plasma process like coherent inverse Compton scattering (CICS) (see Benford, 1992). In accordance with our findings (Kunzl et al. 1998a) this process requires Lorentz factors of about 10 which are lower than in most other radio emission models. This implies that no significant pair production can take place near the surface and we expect charge densities close to the Goldreich-Julian value (Goldreich & Julian (1969)). To fulfill the energetic and electrodynamic constraints the model requires constant re-acceleration in dissipation regions which can be interpreted as a voltage drop similar to that in a resistive current circuit built of a battery, connecting copper wires and a resistive load. Using the emission heights for PSR 0329+54 published by Mitra and Rankin (2002) and the spectral data from Malofeev et al. (1994) we find that a constant depth of the dissipation region of about 2 rNS can account for the observed luminosities and spectral behavior. The extremely high peak fluxes in the substructures of single pulses can be explained by beaming effects as discussed in Kunzl et al. (1998b).
Advanced modeling of planarization processes for integrated circuit fabrication
Fan, Wei, Ph. D. Massachusetts Institute of Technology
2012-01-01
Planarization processes are a key enabling technology for continued performance and density improvements in integrated circuits (ICs). Dielectric material planarization is widely used in front-end-of-line (FEOL) processing ...
Astrocyte regulation of sleep circuits: experimental and modeling perspectives
Halassa, Michael M.
Integrated within neural circuits, astrocytes have recently been shown to modulate brain rhythms thought to mediate sleep function. Experimental evidence suggests that local impact of astrocytes on single synapses translates ...
Basic Neuron Model Electrical Equivalent Circuit: An Undergraduate Laboratory Exercise
Dabrowski, Katie M.; Castaño, Diego J.; Tartar, Jaime L.
2013-01-01
We developed a hands-on laboratory exercise for undergraduate students in which they can build and manipulate a neuron equivalent circuit. This exercise uses electrical circuit components that resemble neuron components and are easy to construct. We describe the methods for creating the equivalent circuit and how to observe different neuron properties through altering the structure of the equivalent circuit. We explain how this hands-on laboratory activity allows for the better understanding of this fundamental neuroscience concept. At the conclusion of this laboratory exercise, undergraduate students will be able to apply the principles of Ohm’s law, cable theory with regards to neurons, and understand the functions of resistance and capacitance in a neuron. PMID:24319391
Log-domain circuit models of chemical reactions
Mandal, Soumyajit
We exploit the detailed similarities between electronics and chemistry to develop efficient, scalable bipolar or subthreshold log-domain circuits that are dynamically equivalent to networks of chemical reactions. Our ...
n Scroll chaos generators: a simple circuit model
Yaln Zo Guz; M. E. Yaln; S. Zo Guz; J. A. K. Suykens
Introduction: The use of chaotic signals in communications has recently received a great deal of interest. An important part in chaos-based analog /digital communications systems [1] is the choice of the chaotic oscillator. Chua's circuit [2] is probably the most well-known and commonly used chaotic oscillator in this field. Among the many generalizations of Chua's circuit, more complicated attractors have been proposed by Suykens & Vandewalle [3] by introducing additional breakpoints in the nonlinearity of Chua's circuit, leading to so-called n-double scroll attractors. A more complete family of n-scroll instead of n-double scroll attractors has been obtained from a generalized Chua's circuit reported in [4]. Experimental confirmations of 2-double scroll and 5-scroll attractors have been given in [5] and [6], respectively. The same generalization idea has been applied to n-scroll hyperchaotic attractors proposed by Yalcin, Suykens & Vandewalle [7]. The design of chaos generators has r
Three-Dimensional Electro-Thermal Verilog-A Model of Power MOSFET for Circuit Simulation
NASA Astrophysics Data System (ADS)
Chvála, A.; Donoval, D.; Marek, J.; Príbytný, P.; Molnár, M.; Mikolášek, M.
2014-04-01
New original circuit model for the power device based on interactive coupling of electrical and thermal properties is described. The thermal equivalent network for a three-dimensional heat flow is presented. Designed electro-thermal MOSFET model for circuit simulations with distributed properties and three-dimensional thermal equivalent network is used for simulation of multipulse unclamped inductive switching (UIS) test of device robustness. The features and the limitations of the new model are analyzed and presented.
T. Ngnegueu; M. Mailhot; A. Munar; M. Sacotte
1995-01-01
In this paper, we present a finite element model for the calculation of zero phase sequence reactance for three phase three leg core type power transformers. An axisymmetrical approximation is assumed. A simplified model is used to assess the tank's hottest spot temperature
Coupling effects throughout the solar atmosphere: 2. Model of energetically open circuit
M. Ryutova
2006-01-01
EUV structures in the solar atmosphere are studied on the basis of the energetically open equivalent circuits. The systems consist of current carrying magnetic loops that interconnect a high ? energy-production region with a low ? dissipation region and include the transition region where the most efficient generation of currents and transport of the accumulated energy through the resistive stresses
Fast Algorithms for High Frequency Interconnect Modeling in VLSI Circuits and Packages
Yi, Yang
2011-02-22
used in MEMS, RFID and MRAM. We present the first BEM algorithm to extract interconnect inductance with magnetic materials. The algorithm models magnetic characteristics by the Landau Lifshitz Gilbert equation and fictitious magnetic charges...
NASA Astrophysics Data System (ADS)
Jazebi, Saeed
This thesis is a step forward toward achieving the final objective of creating a fully dual model for transformers including eddy currents and nonlinearities of the iron core using the fundamental electrical components already available in the EMTP-type programs. The model is effective for the study of the performance of transformers during power system transients. This is very important for transformer designers, because the insulation of transformers is determined with the overvoltages caused by lightning or switching operations. There are also internally induced transients that occur when a switch is actuated. For example switching actions for reconfiguration of distribution systems that offers economic advantages, or protective actions to clear faults and large short-circuit currents. Many of the smart grid concepts currently under development by many utilities rely heavily on switching to optimize resources that produce transients in the system. On the other hand, inrush currents produce mechanical forces which deform transformer windings and cause malfunction of the differential protection. Also, transformer performance under ferroresonance and geomagnetic induced currents are necessary to study. In this thesis, a physically consistent dual model applicable to single-phase two-winding transformers is proposed. First, the topology of a dual electrical equivalent circuit is obtained from the direct application of the principle of duality. Then, the model parameters are computed considering the variations of the transformer electromagnetic behavior under various operating conditions. Current modeling techniques use different topological models to represent diverse transient situations. The reversible model proposed in this thesis unifies the terminal and topological equivalent circuits. The model remains invariable for all low-frequency transients including deep saturation conditions driven from any of the two windings. The very high saturation region of the iron core magnetizing characteristic is modified with the accurate measurement of the air-core inductance. The air-core inductance is measured using a non-ideal low-power rectifier. Its dc output serves to drive the transformer into deep saturation, and its ripple provides low-amplitude variable excitation. The principal advantage of this method is its simplicity. To model the eddy current effects in the windings, a novel equivalent circuit is proposed. The circuit is derived from the principle of duality and therefore, matches the electromagnetic physical behavior of the transformer windings. It properly models the flux paths and current distribution from dc to MHz. The model is synthesized from a non-uniform concentric discretization of the windings. Concise guidelines are given to optimally calculate the width of the sub-divisions for various transient simulations. To compute the circuit parameters only information about the geometry of the windings and about their material properties is needed. The calculation of the circuit parameters does not require an iterative process. Therefore, the parameters are always real, positive, and free from convergence problems. The proposed model is tested with single-phase transformers for the calculation of magnetizing inrush currents, series ferroresonance, and Geomagnetic Induced Currents (GIC). The electromagnetic transient response of the model is compared to laboratory measurements for validation. Also, 3D finite element simulations are used to validate the electromagnetic behavior of the transformer model. Large manufacturer of transformers, power system designers, and electrical utility companies can benefit from the new model. It simplifies the design and optimization of the transformers' insulation, thereby reducing cost, and enhancing reliability of the system. The model could also be used for inrush current and differential protection studies, geomagnetic induced current studies, harmonic penetration studies, and switching transient studies.
GABAergic circuit dysfunction in the Drosophila Fragile X syndrome model.
Gatto, Cheryl L; Pereira, Daniel; Broadie, Kendal
2014-05-01
Fragile X syndrome (FXS), caused by loss of FMR1 gene function, is the most common heritable cause of intellectual disability and autism spectrum disorders. The FMR1 protein (FMRP) translational regulator mediates activity-dependent control of synapses. In addition to the metabotropic glutamate receptor (mGluR) hyperexcitation FXS theory, the GABA theory postulates that hypoinhibition is causative for disease state symptoms. Here, we use the Drosophila FXS model to assay central brain GABAergic circuitry, especially within the Mushroom Body (MB) learning center. All 3 GABAA receptor (GABAAR) subunits are reportedly downregulated in dfmr1 null brains. We demonstrate parallel downregulation of glutamic acid decarboxylase (GAD), the rate-limiting GABA synthesis enzyme, although GABAergic cell numbers appear unaffected. Mosaic analysis with a repressible cell marker (MARCM) single-cell clonal studies show that dfmr1 null GABAergic neurons innervating the MB calyx display altered architectural development, with early underdevelopment followed by later overelaboration. In addition, a new class of extra-calyx terminating GABAergic neurons is shown to include MB intrinsic ?/? Kenyon Cells (KCs), revealing a novel level of MB inhibitory regulation. Functionally, dfmr1 null GABAergic neurons exhibit elevated calcium signaling and altered kinetics in response to acute depolarization. To test the role of these GABAergic changes, we attempted to pharmacologically restore GABAergic signaling and assay effects on the compromised MB-dependent olfactory learning in dfmr1 mutants, but found no improvement. Our results show that GABAergic circuit structure and function are impaired in the FXS disease state, but that correction of hypoinhibition alone is not sufficient to rescue a behavioral learning impairment. PMID:24423648
Status of the Consolidation of the LHC Superconducting Magnets and Circuits
NASA Astrophysics Data System (ADS)
Tock, J. Ph; Atieh, S.; Bodart, D.; Bordry, F.; Bourcey, N.; Cruikshank, P.; Dahlerup-Petersen, K.; Dalin, J. M.; Garion, C.; Musso, A.; Ostojic, R.; Perin, A.; Pojer, M.; Savary, F.; Scheuerlein, C.
2014-05-01
The first LHC long shutdown (LS1) started in February 2013. It was triggered by the need to consolidate the 13 kA splices between the superconducting magnets to allow the LHC to reach safely its design energy of 14 TeV center of mass. The final design of the consolidated splices is recalled. 1695 interconnections containing 10 170 splices have to be opened. In addition to the work on the 13 kA splices, the other interventions performed during the first long shut-down on all the superconducting circuits are described. All this work has been structured in a project, gathering about 280 persons. The opening of the interconnections started in April 2013 and consolidation works are planned to be completed by August 2014. This paper describes first the preparation phase with the building of the teams and the detailed planning of the operation. Then, it gives feedback from the worksite, namely lessons learnt and adaptations that were implemented, both from the technical and organizational points of view. Finally, perspectives for the completion of this consolidation campaign are given.
Modeling Magnetic Properties in EZTB
NASA Technical Reports Server (NTRS)
Lee, Seungwon; vonAllmen, Paul
2007-01-01
A software module that calculates magnetic properties of a semiconducting material has been written for incorporation into, and execution within, the Easy (Modular) Tight-Binding (EZTB) software infrastructure. [EZTB is designed to model the electronic structures of semiconductor devices ranging from bulk semiconductors, to quantum wells, quantum wires, and quantum dots. EZTB implements an empirical tight-binding mathematical model of the underlying physics.] This module can model the effect of a magnetic field applied along any direction and does not require any adjustment of model parameters. The module has thus far been applied to study the performances of silicon-based quantum computers in the presence of magnetic fields and of miscut angles in quantum wells. The module is expected to assist experimentalists in fabricating a spin qubit in a Si/SiGe quantum dot. This software can be executed in almost any Unix operating system, utilizes parallel computing, can be run as a Web-portal application program. The module has been validated by comparison of its predictions with experimental data available in the literature.
Characterization and modeling of plasma etch pattern dependencies in integrated circuits
Abrokwah, Kwaku O
2006-01-01
A quantitative model capturing pattern dependent effects in plasma etching of integrated circuits (ICs) is presented. Plasma etching is a key process for pattern formation in IC manufacturing. Unfortunately, pattern dependent ...
Darvishi, Mostafa; Blaquière, Yves; Thibeault, Claude
2015-01-01
This paper presents a novel circuit level model that explains and confirms the extra combinational delays in a SRAM-FPGA (Virtex-5) due to radiation, which matches the experimental results by proton irradiation at TRIUMF.
A coupled-circuit model for a DFIG operating under unbalanced conditions
S. Djurovic; S. Williamson
2008-01-01
The paper describes a time-stepped coupled-circuit model for a doubly-fed induction generator. The model, which is based on the summation of the harmonic winding inductances, is capable of representing both open- and short-circuit stator and rotor winding faults. The main purpose of this paper is to present evidence of the validity of this versatile and powerful technique and the advantages
Tosi, Guilherme, E-mail: g.tosi@unsw.edu.au; Mohiyaddin, Fahd A.; Morello, Andrea, E-mail: a.morello@unsw.edu.au [Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, UNSW Australia, Sydney, New South Wales 2052, Australia. (Australia); Huebl, Hans [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, D-85748 Garching (Germany); Nanosystems Initiative Munich (NIM), Schellingstr. 4, D-80799 Munich, Germany. (Germany)
2014-08-15
Recent advances in silicon nanofabrication have allowed the manipulation of spin qubits that are extremely isolated from noise sources, being therefore the semiconductor equivalent of single atoms in vacuum. We investigate the possibility of directly coupling an electron spin qubit to a superconducting resonator magnetic vacuum field. By using resonators modified to increase the vacuum magnetic field at the qubit location, and isotopically purified {sup 28}Si substrates, it is possible to achieve coupling rates faster than the single spin dephasing. This opens up new avenues for circuit-quantum electrodynamics with spins, and provides a pathway for dispersive read-out of spin qubits via superconducting resonators.
Strongly magnetized classical plasma models
NASA Technical Reports Server (NTRS)
Montgomery, D.; Peyraud, J.; Dewitt, C.
1974-01-01
Discrete particle processes in the presence of a strong external magnetic field were investigated. These processes include equations of state and other equilibrium thermodynamic relations, thermal relaxation phenomena, transport properties, and microscopic statistical fluctuations in such quantities as the electric field and the charge density. Results from the equilibrium statistical mechanics of two-dimensional plasmas are discussed, along with nonequilibrium statistical mechanics of the electrostatic guiding-center plasma (a two-dimensional plasma model).
A universal MOSFET mobility degradation model for circuit simulation
Gregory Munson Yeric; A. F. Tasch Jr.; Sanjay K. Banerjee
1990-01-01
From the physical insights provided by the universal effective mobility versus effective vertical electric field curve for electrons in MOS inversion layers, a simple general expression for the gate voltage dependence of the effective electron mobility is derived for use in SPICE circuit simulation. This expression is quite accurate over a wide range of channel doping concentrations and gate oxide
Taylan, O.; Berberoglu, H., E-mail: berberoglu@mail.utexas.edu [Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States)
2014-07-28
This paper reports the electrical characterization and an equivalent circuit of a microhollow cathode discharge (MHCD) reactor in the self-pulsing regime. A MHCD reactor was prototyped for air plasma generation, and its current-voltage characteristics were measured experimentally in the self-pulsing regime for applied voltages from 2000 to 3000?V. The reactor was modeled as a capacitor in parallel with a variable resistor. A stray capacitance was also introduced to the circuit model to represent the capacitance of the circuit elements in the experimental setup. The values of the resistor and capacitors were recovered from experimental data, and the proposed circuit model was validated with independent experiments. Experimental data showed that increasing the applied voltage increased the current, self-pulsing frequency and average power consumption of the reactor, while it decreased the peak voltage. The maximum and the minimum voltages obtained using the model were in agreement with the experimental data within 2.5%, whereas the differences between peak current values were less than 1%. At all applied voltages, the equivalent circuit model was able to accurately represent the peak and average power consumption as well as the self-pulsing frequency within the experimental uncertainty. Although the results shown in this paper was for atmospheric air pressures, the proposed equivalent circuit model of the MHCD reactor could be generalized for other gases at different pressures.
NASA Astrophysics Data System (ADS)
Taylan, O.; Berberoglu, H.
2014-07-01
This paper reports the electrical characterization and an equivalent circuit of a microhollow cathode discharge (MHCD) reactor in the self-pulsing regime. A MHCD reactor was prototyped for air plasma generation, and its current-voltage characteristics were measured experimentally in the self-pulsing regime for applied voltages from 2000 to 3000 V. The reactor was modeled as a capacitor in parallel with a variable resistor. A stray capacitance was also introduced to the circuit model to represent the capacitance of the circuit elements in the experimental setup. The values of the resistor and capacitors were recovered from experimental data, and the proposed circuit model was validated with independent experiments. Experimental data showed that increasing the applied voltage increased the current, self-pulsing frequency and average power consumption of the reactor, while it decreased the peak voltage. The maximum and the minimum voltages obtained using the model were in agreement with the experimental data within 2.5%, whereas the differences between peak current values were less than 1%. At all applied voltages, the equivalent circuit model was able to accurately represent the peak and average power consumption as well as the self-pulsing frequency within the experimental uncertainty. Although the results shown in this paper was for atmospheric air pressures, the proposed equivalent circuit model of the MHCD reactor could be generalized for other gases at different pressures.
NASA Astrophysics Data System (ADS)
>Oon Kheng Heong,
2013-06-01
There are various types of UWB antennas can be used to scavenge energy from the air and one of them is the printed disc monopole antenna. One of the new challenges imposed on ultra wideband is the design of a generalized antenna circuit model. It is developed in order to extract the inductance and capacitance values of the UWB antennas. In this research work, the developed circuit model can be used to represent the rectangular printed disc monopole antenna with double steps. The antenna structure is simulated with CST Microwave Studio, while the circuit model is simulated with AWR Microwave Office. In order to ensure the simulation result from the circuit model is accurate, the circuit model is also simulated using Mathlab program. The developed circuit model is found to be able to depict the actual UWB antenna. Energy harvesting from environmental wirelessly is an emerging method, which forms a promising alternative to existing energy scavenging system. The developed UWB can be used to scavenge wideband energy from electromagnetic wave present in the environment.
An Equivalent Circuit Model for Electrostatic Energy Harvester utilized Energy Harvesting System
NASA Astrophysics Data System (ADS)
Minami, K.; Fujita, T.; Sonoda, K.; Miwatani, N.; Kanda, K.; Maenaka, K.
2014-11-01
In this study, we report an equivalent circuit model of an electrostatic energy harvester for a SPICE circuit simulator. In order to simulate a harvesting system, the output power of the device is calculated in the simulator. The capacitance between the electrodes is obtained by FEM analysis by taking the fringing effect into account and the result is applied to a sub-circuit model for the simulator. Mechanical vibrations are converted into electricity by an equivalent circuit model of a mass-spring structure and an electrostatic energy harvester. The simulated output power and output waveform correspond with the measurement results of our electrostatic energy harvester. We also simulate the operation of a harvesting system connected with a power management IC.
Superior model for fault tolerance computation in designing nano-sized circuit systems
Singh, N. S. S., E-mail: narinderjit@petronas.com.my; Muthuvalu, M. S., E-mail: msmuthuvalu@gmail.com [Fundamental and Applied Sciences Department, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Perak (Malaysia); Asirvadam, V. S., E-mail: vijanth-sagayan@petronas.com.my [Electrical and Electronics Engineering Department, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Perak (Malaysia)
2014-10-24
As CMOS technology scales nano-metrically, reliability turns out to be a decisive subject in the design methodology of nano-sized circuit systems. As a result, several computational approaches have been developed to compute and evaluate reliability of desired nano-electronic circuits. The process of computing reliability becomes very troublesome and time consuming as the computational complexity build ups with the desired circuit size. Therefore, being able to measure reliability instantly and superiorly is fast becoming necessary in designing modern logic integrated circuits. For this purpose, the paper firstly looks into the development of an automated reliability evaluation tool based on the generalization of Probabilistic Gate Model (PGM) and Boolean Difference-based Error Calculator (BDEC) models. The Matlab-based tool allows users to significantly speed-up the task of reliability analysis for very large number of nano-electronic circuits. Secondly, by using the developed automated tool, the paper explores into a comparative study involving reliability computation and evaluation by PGM and, BDEC models for different implementations of same functionality circuits. Based on the reliability analysis, BDEC gives exact and transparent reliability measures, but as the complexity of the same functionality circuits with respect to gate error increases, reliability measure by BDEC tends to be lower than the reliability measure by PGM. The lesser reliability measure by BDEC is well explained in this paper using distribution of different signal input patterns overtime for same functionality circuits. Simulation results conclude that the reliability measure by BDEC depends not only on faulty gates but it also depends on circuit topology, probability of input signals being one or zero and also probability of error on signal lines.
Superior model for fault tolerance computation in designing nano-sized circuit systems
NASA Astrophysics Data System (ADS)
Singh, N. S. S.; Asirvadam, V. S.; Muthuvalu, M. S.
2014-10-01
As CMOS technology scales nano-metrically, reliability turns out to be a decisive subject in the design methodology of nano-sized circuit systems. As a result, several computational approaches have been developed to compute and evaluate reliability of desired nano-electronic circuits. The process of computing reliability becomes very troublesome and time consuming as the computational complexity build ups with the desired circuit size. Therefore, being able to measure reliability instantly and superiorly is fast becoming necessary in designing modern logic integrated circuits. For this purpose, the paper firstly looks into the development of an automated reliability evaluation tool based on the generalization of Probabilistic Gate Model (PGM) and Boolean Difference-based Error Calculator (BDEC) models. The Matlab-based tool allows users to significantly speed-up the task of reliability analysis for very large number of nano-electronic circuits. Secondly, by using the developed automated tool, the paper explores into a comparative study involving reliability computation and evaluation by PGM and, BDEC models for different implementations of same functionality circuits. Based on the reliability analysis, BDEC gives exact and transparent reliability measures, but as the complexity of the same functionality circuits with respect to gate error increases, reliability measure by BDEC tends to be lower than the reliability measure by PGM. The lesser reliability measure by BDEC is well explained in this paper using distribution of different signal input patterns overtime for same functionality circuits. Simulation results conclude that the reliability measure by BDEC depends not only on faulty gates but it also depends on circuit topology, probability of input signals being one or zero and also probability of error on signal lines.
Quantum game simulator, using the circuit model of quantum computation
NASA Astrophysics Data System (ADS)
Vlachos, Panagiotis; Karafyllidis, Ioannis G.
2009-10-01
We present a general two-player quantum game simulator that can simulate any two-player quantum game described by a 2×2 payoff matrix (two strategy games).The user can determine the payoff matrices for both players, their strategies and the amount of entanglement between their initial strategies. The outputs of the simulator are the expected payoffs of each player as a function of the other player's strategy parameters and the amount of entanglement. The simulator also produces contour plots that divide the strategy spaces of the game in regions in which players can get larger payoffs if they choose to use a quantum strategy against any classical one. We also apply the simulator to two well-known quantum games, the Battle of Sexes and the Chicken game. Program summaryProgram title: Quantum Game Simulator (QGS) Catalogue identifier: AEED_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEED_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 3416 No. of bytes in distributed program, including test data, etc.: 583 553 Distribution format: tar.gz Programming language: Matlab R2008a (C) Computer: Any computer that can sufficiently run Matlab R2008a Operating system: Any system that can sufficiently run Matlab R2008a Classification: 4.15 Nature of problem: Simulation of two player quantum games described by a payoff matrix. Solution method: The program calculates the matrices that comprise the Eisert setup for quantum games based on the quantum circuit model. There are 5 parameters that can be altered. We define 3 of them as constant. We play the quantum game for all possible values for the other 2 parameters and store the results in a matrix. Unusual features: The software provides an easy way of simulating any two-player quantum games. Running time: Approximately 0.4 sec (Region Feature) and 0.3 sec (Payoff Feature) on a Intel Core 2 Duo GHz with 2 GB of memory under Windows XP.
Power-Invariant Magnetic System Modeling
Gonzalez Dominguez, Guadalupe Giselle
2012-10-19
POWER-INVARIANT MAGNETIC SYSTEM MODELING A Dissertation by GUADALUPE GISELLE GONZALEZ DOMINGUEZ Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree... of DOCTOR OF PHILOSOPHY August 2011 Major Subject: Electrical Engineering Power-Invariant Magnetic System Modeling Copyright 2011 Guadalupe Giselle González Domínguez POWER-INVARIANT MAGNETIC...
None
2012-01-09
GENI Project: General Atomics is developing a direct current (DC) circuit breaker that could protect the grid from faults 100 times faster than its alternating current (AC) counterparts. Circuit breakers are critical elements in any electrical system. At the grid level, their main function is to isolate parts of the grid where a fault has occurred—such as a downed power line or a transformer explosion—from the rest of the system. DC circuit breakers must interrupt the system during a fault much faster than AC circuit breakers to prevent possible damage to cables, converters and other grid-level components. General Atomics’ high-voltage DC circuit breaker would react in less than 1/1,000th of a second to interrupt current during a fault, preventing potential hazards to people and equipment.
van den Heuvel, Odile A; Van Gorsel, Helene C; Veltman, Dick J; Van Der Werf, Ysbrand D
2013-02-01
The dorsal frontal-striatal circuit is implicated in executive functions, such as planning. The Tower of London task, a planning task, in combination with off-line low-frequency repetitive transcranial magnetic stimulation (rTMS), was used to investigate whether interfering with dorsolateral prefrontal function would modulate executive performance, mimicking dorsal frontal-striatal dysfunction as found in neuropsychiatric disorders. Eleven healthy controls (seven females; mean age 25.5 years) were entered in a cross-over design: two single-session treatments of low-frequency (1 Hz) rTMS (vs. sham rTMS) for 20 min on the left dorsolateral prefrontal cortex (DLPFC). Directly following the off-line rTMS treatment, the Tower of London task was performed during MRI measurements. The low-frequency rTMS treatment impaired performance, but only when the subjects had not performed the task before: we found a TMS condition-by-order effect, such that real TMS treatment in the first session led to significantly more errors (P = 0.032), whereas this TMS effect was not present in subjects who received real TMS in the second session. At the neural level, rTMS resulted in decreased activation during the rTMS versus sham condition in prefrontal brain regions (i.e., premotor, dorsolateral prefrontal and anterior prefrontal cortices) and visuospatial brain regions (i.e., precuneus/cuneus and inferior parietal cortex). The results show that low-frequency off-line rTMS on the DLPFC resulted in decreased task-related activations in the frontal and visuospatial regions during the performance of the Tower of London task, with a behavioral effect only when task experience is limited. PMID:22076808
A proper model for the partitioning of electrical circuits
D. G. Schweikert; B. W. Kernighan
1972-01-01
Partitioning algorithms for electrical circuits are often based on the heuristic manipulation of a simple element-to-element interconnection matrix. However, the element-to-element interconnection matrix does not properly represent an electrical interconnection, or “net”, among more than two elements. This paper expands on several aspects of the discrepancy: 1) its source, 2) the circumstances under which it is likely to be significant,
Quasi-Linear Vacancy Dynamics Modeling and Circuit Analysis of the Bipolar Memristor
Abraham, Isaac
2014-01-01
The quasi-linear transport equation is investigated for modeling the bipolar memory resistor. The solution accommodates vacancy and circuit level perspectives on memristance. For the first time in literature the component resistors that constitute the contemporary dual variable resistor circuit model are quantified using vacancy parameters and derived from a governing partial differential equation. The model describes known memristor dynamics even as it generates new insight about vacancy migration, bottlenecks to switching speed and elucidates subtle relationships between switching resistance range and device parameters. The model is shown to comply with Chua's generalized equations for the memristor. Independent experimental results are used throughout, to validate the insights obtained from the model. The paper concludes by implementing a memristor-capacitor filter and compares its performance to a reference resistor-capacitor filter to demonstrate that the model is usable for practical circuit analysis. PMID:25390634
Quasi-linear vacancy dynamics modeling and circuit analysis of the bipolar memristor.
Abraham, Isaac
2014-01-01
The quasi-linear transport equation is investigated for modeling the bipolar memory resistor. The solution accommodates vacancy and circuit level perspectives on memristance. For the first time in literature the component resistors that constitute the contemporary dual variable resistor circuit model are quantified using vacancy parameters and derived from a governing partial differential equation. The model describes known memristor dynamics even as it generates new insight about vacancy migration, bottlenecks to switching speed and elucidates subtle relationships between switching resistance range and device parameters. The model is shown to comply with Chua's generalized equations for the memristor. Independent experimental results are used throughout, to validate the insights obtained from the model. The paper concludes by implementing a memristor-capacitor filter and compares its performance to a reference resistor-capacitor filter to demonstrate that the model is usable for practical circuit analysis. PMID:25390634
Modeling and simulation of magnetic nanoparticle sensor.
Makiranta, Jarkko; Lekkala, Jukka
2005-01-01
Sensitivity and detection limit of a magnetic nanoparticle sensor is modeled and simulated. A micro coil generates an alternating magnetic field which excites magnetic nanoparticles in its vicinity. A concentric sensing coil applies Faraday's law of induction measuring the excited magnetization of the magnetic particles at high frequency. A differential measurement compensates disturbances and the influence of the driving microcoil leaving only the signal caused by the magnetic particles. The sensing system can be used for detection of magnetic nanoparticle labels in immunological point of care diagnostics. The paper shows simulation results for a microcoil system capable of detecting a single superparamagnetic nanoparticle. PMID:17282422
Reduced-Order Modeling Techniques Based on Krylov Subspaces and Their Use in Circuit Simulation
Roland W. Freund
1998-01-01
In recent years, reduced-order modeling techniques based on Krylov-subspace iterations,especially the Lanczos algorithm and the Arnoldi process, have become populartools to tackle the large-scale time-invariant linear dynamical systems that arise in thesimulation of electronic circuits. This paper reviews the main ideas of reduced-ordermodeling techniques based on Krylov subspaces and describes the use of reduced-ordermodeling in circuit simulation.1 IntroductionKrylov-subspace methods, ...
Object-Oriented Modeling Of Power-Electronic Circuits Using Dymola
Hilding Elmqvist; François E. Cellier; Martin Otter
1994-01-01
In this paper, a new approach to the object--oriented modelingof power--electronic circuits is demonstrated. It enablesthe user to specify power--electronic circuits convenientlyin an easy--to--use modular fashion, yet generate simulationcode that is efficient in its use, not requiring the introductionof artificial fast time--constants as was the case with many ofthe earlier proposed methodologies. Dymola enables the userto specify models for individual
Generalized Partial-Element Equivalent-Circuit Analysis for Planar Circuits With Slotted Ground
Kai Yang; Ke-Li Wu
2009-01-01
A generalized partial-element equivalent-circuit (PEEC) method is proposed for modeling a planar circuit with a thin narrow slot on the ground. The approach is based on the coupled mixed potential integral equations for a problem with mixed electric and magnetic currents. The coupled integral equations are converted into a lumped-element circuit network using Kirchhoff's voltage law and Kirchhoff's current law
NSDL National Science Digital Library
A database for electrical engineering students and professionals, the Circuits Archive provides diagrams of radio, computer, and other miscellaneous circuits (ASCII, .gif, and HTML formats). The archive is just one part of this metasite housed at the University of Washington's Electrical Engineering site. In addition to the circuit diagrams, a searchable database of transistor cross-references, a component reference page (both in the Data Sheets section), and links to models and microprocessors are featured. Other useful tools included are the Reading Capacitors page and links to software sites. Diagrams and links are voluntarily contributed and seem to be updated regularly. Note: the site includes a page on software in the Circuits Archive.
Dynamic Models of Turbine Generators Derived From Solid Rotor Equivalent Circuits
Richard Schulz; William Jones; Donald Ewart
1973-01-01
A method is described for determining the structure and coefficients of dynamic models of turbogenerators from detailed equivalent circuits of the d-and q-axes of a solid rotor generator. These models are intended for analyses of power system dynamics in cases where it is desirable to have a very accurate representation of the synchronous machine. The models have been used to
In vitro investigation of the behaviour of magnetic particles by a circulating artery model
NASA Astrophysics Data System (ADS)
Seliger, Christian; Jurgons, Roland; Wiekhorst, Frank; Eberbeck, Dietmar; Trahms, Lutz; Iro, H.; Alexiou, Christoph
2007-04-01
Magnetic drug targeting is the use of coated magnetic nanoparticles as carriers for cytostatic drugs. After intraarterial application of these carriers, they are attracted with an external magnetic field to, for example, an experimental VX2 tumour. The biological compatibility of this system depends on several physiological and physical parameters. We established an in vitro model to simulate in vivo conditions in a circulating system consisting of a circuit with an intact bovine femoral artery close to an external magnetic field. Nanoparticle suspensions were applied by a side inlet. After the magnetisation procedure particle size, concentration and distribution was examined.
Microfluidic primary culture model of the lower motor neuron-neuromuscular junction circuit.
Southam, Katherine A; King, Anna E; Blizzard, Catherine A; McCormack, Graeme H; Dickson, Tracey C
2013-09-15
Modelling the complex process of neuromuscular signalling is key to understanding not only normal circuit function but also importantly the mechanisms underpinning a range of degenerative diseases. We describe a novel in vitro model of the lower motor neuron-neuromuscular junction circuit, incorporating primary spinal motor neurons, supporting glia and skeletal muscle. This culture model is designed to spatially mimic the unique anatomical and cellular interactions of this circuit in compartmented microfluidic devices, such that the glial cells are located with motor neuron cell bodies in the cell body chamber and motor neuron axons extend to a distal chamber containing skeletal muscle cells whilst simultaneously allowing targeted intervention. This model is suitable for use in conjunction with a range of downstream experimental approaches and could also be modified to utilise other cellular sources including appropriate immortal cell lines, cells derived from transgenic models of disease and also patient derived stem cells. PMID:23774648
Modular, rule-based modeling for the design of eukaryotic synthetic gene circuits
2013-01-01
Background The modular design of synthetic gene circuits via composable parts (DNA segments) and pools of signal carriers (molecules such as RNA polymerases and ribosomes) has been successfully applied to bacterial systems. However, eukaryotic cells are becoming a preferential host for new synthetic biology applications. Therefore, an accurate description of the intricate network of reactions that take place inside eukaryotic parts and pools is necessary. Rule-based modeling approaches are increasingly used to obtain compact representations of reaction networks in biological systems. However, this approach is intrinsically non-modular and not suitable per se for the description of composable genetic modules. In contrast, the Model Description Language (MDL) adopted by the modeling tool ProMoT is highly modular and it enables a faithful representation of biological parts and pools. Results We developed a computational framework for the design of complex (eukaryotic) gene circuits by generating dynamic models of parts and pools via the joint usage of the BioNetGen rule-based modeling approach and MDL. The framework converts the specification of a part (or pool) structure into rules that serve as inputs for BioNetGen to calculate the part’s species and reactions. The BioNetGen output is translated into an MDL file that gives a complete description of all the reactions that take place inside the part (or pool) together with a proper interface to connect it to other modules in the circuit. In proof-of-principle applications to eukaryotic Boolean circuits with more than ten genes and more than one thousand reactions, our framework yielded proper representations of the circuits’ truth tables. Conclusions For the model-based design of increasingly complex gene circuits, it is critical to achieve exact and systematic representations of the biological processes with minimal effort. Our computational framework provides such a detailed and intuitive way to design new and complex synthetic gene circuits. PMID:23705868
NASA Astrophysics Data System (ADS)
Wang, Meng-yao; Pan, Wei; Luo, Bin; Zhang, Wei-li; Zou, Xi-hua
2008-05-01
For V-shaped, thresholdless switching ferroelectric liquid crystals (FLCs), the impedance divider induced by the multilayer structure of FLC cells and the drive circuit play an important role in switching characteristics. In this paper, an equivalent circuit model that can be applied to conventional circuit simulators is proposed for the optical response prediction and drive circuit optimization of V-shaped FLCs. The model is improved from the original model of Moore and Travis; however, the impedance divider is taken into account, and both polar and nonpolar surface anchoring energies are considered to make the model more preferable. The model is then utilized to investigate thresholdless switching characteristics. Simulation results show that the hysteresis inversion frequency fi increases more than one thousand fold with the drive circuit and then decreases with REXT following the relation log fi = -alog REXT + b, and a (b) increases from 0.43 to 0.46 (2.46 to 2.66) as the amplitude of triangular voltage increases from 4 to 10 V, agreeing with experimental results. Also, the same optical transmissions are plotted as different coordinates, as a function of voltage dropping on liquid crystal layer and of drive voltage, and the results show that genuine V-shaped switching is only observed when the transmission is plotted as a function of drive voltage, coinciding with the model suggested by Blinov et al.
NASA Astrophysics Data System (ADS)
Haider, N.; Caratelli, D.; Yarovoy, A. G.
2013-01-01
A planar, directive antenna with large fractional bandwidth is introduced in this paper. A detailed discussion on the proposed antenna topology and its architecture is reported. The proposed element is a combination of a patch and a loop radiator. A proper combination of the electric field radiator (patch) with a magnetic field radiator (loop around the patch) is exploited for expanding the operational bandwidth. A parametric study is presented to investigate the effect of the antenna geometrical parameters on its performance. A general and computationally efficient procedure for extracting the antenna equivalent circuit is described and used to achieve a meaningful circuit theory-based insight into the characteristics of the radiating structure. The theoretical and experimental results are compared, and it is demonstrated that the element features over 100% fractional bandwidth, good impedance matching, and unidirectional and stable radiation patterns.
Sakimura, N., E-mail: n-sakimura@ap.jp.nec.com [Green Platform Research Laboratories, NEC Corporation, Tsukuba (Japan); Research Institute of Electrical Communication, Tohoku University, Sendai (Japan); Nebashi, R.; Sugibayashi, T. [Green Platform Research Laboratories, NEC Corporation, Tsukuba (Japan); Natsui, M.; Hanyu, T. [Research Institute of Electrical Communication, Tohoku University, Sendai (Japan); Ohno, H. [Research Institute of Electrical Communication, Tohoku University, Sendai (Japan); Center for Spintronics Integrated Systems, Tohoku University, Sendai (Japan); WPI Advanced Institute for Materials Research, Tohoku University, Sendai (Japan)
2014-05-07
This paper describes the possibility of a switching upset of a magnetic tunnel junction (MTJ) caused by a terrestrial radiation-induced single-event-upset (SEU) current in spintronic integrated circuits. The current waveforms were simulated by using a 3-D device simulator in a basic circuit including MTJs designed using 90-nm CMOS parameters and design rules. The waveforms have a 400?-?A peak and a 200-ps elapsed time when neutron particles with a linear energy transfer value of 14?MeV cm{sup 2}/mg enter the silicon surface. The authors also found that the SEU current may cause soft errors with a probability of more than 10{sup ?12} per event, which was obtained by approximate solution of the ordinary differential equation of switching probability when the intrinsic critical current (I{sub C0}) became less than 30??A.
Middle school students' mental models of magnets and magnetism
NASA Astrophysics Data System (ADS)
Sederberg, David
The purpose of this study was to conduct a detailed analysis of students' mental models across three themes related to magnetism: what magnets are, what it means to be magnetized, and how magnetic interactions occur. Mental models are organized collections of conceptions, run in one's mind, to help understand the world (Johnson-Laird, 1983). They also provide the learner a means to organize concepts in a way to help understand the world or to explain it to others (Clement & Sarama, 2004; Harrison & Treagust, 1996). While there has been considerable prior research documenting students' conceptions related to magnetism, the majority of the studies comprising this informative and valuable body of work has been confined to specific concepts at points in time. Comparatively, few studies have examined how students make sense of multiple concepts relating to magnetism and how the sophistication and explanatory power of their mental models comprised of these concepts change with instruction. Using an interpretive research design, the goal here was not to count concepts or individuals' representations of them, but rather to qualitatively search for patterns in representations of students' conceptions and lines of reasoning that are indicative of broader interpretations of experience (Strauss & Corbin, 1998) - students' mental models relating to magnetism. Using a variety of methods of elicitation, including free response items prior to and throughout instruction and semi-structured interviews, I identified five categories of concepts from which students constructed their mental models: (1) material-based properties; (2) two-sidedness; (3) internal features; (4) organization; and (5) external spatial features. Analysis of the representation of concepts among these categories yielded five levels of mental models based on model sophistication and ability to explain magnetic phenomena across diverse contexts. Results suggested that through explicitly scaffolded instruction based on a small number of fundamental principles, 8th grade students were able to construct level-appropriate microscale-based mental models of magnetic phenomena.
A digital neurmorphic circuit for a simplified model of astrocyte dynamics.
Nazari, Soheila; Faez, Karim; Karami, Ehsan; Amiri, Mahmood
2014-10-17
Recent neurophysiologic findings have shown that astrocytes (the most abundant type of glial cells) are active partners in neural information processing and regulate the synaptic transmission dynamically. Motivated by these findings, in the present research, a digital neuromorphic circuit to implement the astrocyte dynamics is developed. To model the dynamics of the intracellular Ca(2+) waves produced by astrocytes, we utilize a simplified model which considers the main physiological pathways of neuron-astrocyte interactions. Next, a digital circuit for the astrocyte dynamic is proposed which is simulated using ModelSim and finally, it is implemented in hardware on the ZedBoard. The results of hardware synthesis, FPGA implementations are in agreement with MATLAB and ModelSim simulations and confirm that the proposed digital astrocyte is suitable for applications in reconfigurable neuromorphic devices which implement biologically brain circuits. PMID:25108256
Modeling and magnetic measurements of TNK synchrotron radiation source magnets
NASA Astrophysics Data System (ADS)
Belokrinitsky, S.; Churkin, I.; Oleynik, A.; Pekshev, D.; Philipchenko, A.; Rouvinsky, I.; Steshov, A.; Ushakov, V.
2009-05-01
The TNK synchrotron radiation source is being built by Budker Institute of Nuclear Physics on the base of Lukin State Research Institute of Physical Problems. Magnetic system for the storage ring of TNK synchrotron radiation source was produced at the BINP. It consists of 6 superperiods and includes 24 dipole magnets, 72 quadrupole lenses, 36 sextupole lenses and 12 octupole lenses.The storage ring will operate in a wide range of energies—from 450 to 2200 MeV—which corresponds to 0.3-1.5 T magnetic field in dipole magnets. Dipole magnets have H-shape solid yokes from Armco iron with a curved form. Dipole gap is 42 mm and yoke straight length is 1447 mm. The results of 3D magnetic field modeling executed by means of Mermaid 3D are presented. All dipole magnets were magnetically measured by special Hall probe measurement system developed in BINP. The results of magnetic measurements and modeling are compared and analyzed.
Nanolevel Magnetic Separation Model Considering Flow Limitations
Cotten, Gregory Benedict; Eldredge, H Bradley; Eldredge, H. B.
2002-01-01
This work proposes an enhanced nanolevel magnetic separation model considering flow limitations using simplifying assumptions. The theoretical model builds on magnetic heteroflocculation models described in the literature and couples the magnetic and hydrodynamic forces between two spherical particles with different sizes and different magnetic properties under bulk fluid flow conditions. Separator performance figures are presented showing the relationship between input parameters such as applied magnetic field strength, flow rate, and matrix material size and composition, and output parameters such as Peclet number and capture propensity for various contaminant particle sizes. This purely predictive model work may be useful in estimating actual magnetic separator performance and serve as a starting point for experimental work or more accurate mathematical models. This work provides a simplified mathematical model to predict magnetic separator performance based on single magnetic matrix particle and single magnetic contaminant particle interactions. Local maxima, or transition points, between matrix and contaminant particle size and separator performance indicate magnetic separator performance can be optimized by the selection of appropriate magnetic matrix particle size. Evaluation of points of maximum particle capture force using the Peclet number provides limiting conditions for retention of particles under Stokes flow conditions.
Equivalent-Circuit Model for the TSM Resonator with a Viscoelastic Layer
BANDEY, HELEN L.; CERNOSEK, RICHARD W.; HILLMAN, A.R.; MARTIN, STEPHEN J.
1999-09-16
This paper describes a new equivalent-circuit model for the thickness shear mode resonator with a surface viscoelastic layer operating near film resonance. The electrical impedance of the film is represented by a simple three-element parallel circuit containing a resistor, a capacitor, and an inductor. These elements describe the film's viscous power dissipation, elastic energy storage, and kinetic energy storage, respectively. Resonator response comparisons between this lumped-element model and the general transmission-line model show good agreement over a range of film phase conditions and not just near film resonance.
A Demonstration Model of Magnetic Resonance
ERIC Educational Resources Information Center
Sandhu, H. S.; Peemoeller, H.
1974-01-01
Describes a simple and inexpensive model to demonstrate the pulsed magnetic resonance phenomenon. Gives the details of construction of the device which can provide a direct demonstration of the precessional motion of a magnetic moment in a steady magnetic field. (Author/GS)
Makowiecki, Kalina; Harvey, Alan R; Sherrard, Rachel M; Rodger, Jennifer
2014-08-01
Repetitive transcranial magnetic stimulation (rTMS) is increasingly used as a treatment for neurological and psychiatric disorders. Although the induced field is focused on a target region during rTMS, adjacent areas also receive stimulation at a lower intensity and the contribution of this perifocal stimulation to network-wide effects is poorly defined. Here, we examined low-intensity rTMS (LI-rTMS)-induced changes on a model neural network using the visual systems of normal (C57Bl/6J wild-type, n = 22) and ephrin-A2A5(-/-) (n = 22) mice, the latter possessing visuotopic anomalies. Mice were treated with LI-rTMS or sham (handling control) daily for 14 d, then fluorojade and fluororuby were injected into visual cortex. The distribution of dorsal LGN (dLGN) neurons and corticotectal terminal zones (TZs) was mapped and disorder defined by comparing their actual location with that predicted by injection sites. In the afferent geniculocortical projection, LI-rTMS decreased the abnormally high dispersion of retrogradely labeled neurons in the dLGN of ephrin-A2A5(-/-) mice, indicating geniculocortical map refinement. In the corticotectal efferents, LI-rTMS improved topography of the most abnormal TZs in ephrin-A2A5(-/-) mice without altering topographically normal TZs. To investigate a possible molecular mechanism for LI-rTMS-induced structural plasticity, we measured brain derived neurotrophic factor (BDNF) in the visual cortex and superior colliculus after single and multiple stimulations. BDNF was upregulated after a single stimulation for all groups, but only sustained in the superior colliculus of ephrin-A2A5(-/-) mice. Our results show that LI-rTMS upregulates BDNF, promoting a plastic environment conducive to beneficial reorganization of abnormal cortical circuits, information that has important implications for clinical rTMS. PMID:25100609
Makowiecki, Kalina; Harvey, Alan R.; Sherrard, Rachel M.
2014-01-01
Repetitive transcranial magnetic stimulation (rTMS) is increasingly used as a treatment for neurological and psychiatric disorders. Although the induced field is focused on a target region during rTMS, adjacent areas also receive stimulation at a lower intensity and the contribution of this perifocal stimulation to network-wide effects is poorly defined. Here, we examined low-intensity rTMS (LI-rTMS)-induced changes on a model neural network using the visual systems of normal (C57Bl/6J wild-type, n = 22) and ephrin-A2A5?/? (n = 22) mice, the latter possessing visuotopic anomalies. Mice were treated with LI-rTMS or sham (handling control) daily for 14 d, then fluorojade and fluororuby were injected into visual cortex. The distribution of dorsal LGN (dLGN) neurons and corticotectal terminal zones (TZs) was mapped and disorder defined by comparing their actual location with that predicted by injection sites. In the afferent geniculocortical projection, LI-rTMS decreased the abnormally high dispersion of retrogradely labeled neurons in the dLGN of ephrin-A2A5?/? mice, indicating geniculocortical map refinement. In the corticotectal efferents, LI-rTMS improved topography of the most abnormal TZs in ephrin-A2A5?/? mice without altering topographically normal TZs. To investigate a possible molecular mechanism for LI-rTMS-induced structural plasticity, we measured brain derived neurotrophic factor (BDNF) in the visual cortex and superior colliculus after single and multiple stimulations. BDNF was upregulated after a single stimulation for all groups, but only sustained in the superior colliculus of ephrin-A2A5?/? mice. Our results show that LI-rTMS upregulates BDNF, promoting a plastic environment conducive to beneficial reorganization of abnormal cortical circuits, information that has important implications for clinical rTMS. PMID:25100609
V.DMOS transistor modeling for simulation of power electronic circuits
NASA Astrophysics Data System (ADS)
Napieralska, Malgorzata
1991-08-01
A nonlinear, short channel model of a power V.DMOS transistor, the elements of which depend only on physical and technological data, is presented. By an analysis of the active regions of the V.DMOS structure, in order to study switching modes, this model is simplified to a topology compatible with the SPICE circuit simulator. Parameter extraction methods and validation programs are described. A software library of the SPICE models is created by testing the transistors (N and P channels) covering the available current handling capability 2A to 50A and blocking range 50V to 1000V. A V.DMOS unified model is presented. It requires establishment of two parameters: drain source breakdown voltage, and silicon chip area. An established program linked in Hypercard with SPICE, gives an exact model for characterizing transistors as well as a model for new devices. This modeling takes into account the crystal temperature and several validation tests. Adaptation of the model for irradiation applications is pointed out by comparison between measured and computed characteristics. Use of this model to analyze bridge leg circuit properties and comparison between simulated results and measured data, confirms its application in power electronic circuits. Some problems associated with parasitic elements in these circuits are described.
Validation of an Accurate Three-Dimensional Helical Slow-Wave Circuit Model
NASA Technical Reports Server (NTRS)
Kory, Carol L.
1997-01-01
The helical slow-wave circuit embodies a helical coil of rectangular tape supported in a metal barrel by dielectric support rods. Although the helix slow-wave circuit remains the mainstay of the traveling-wave tube (TWT) industry because of its exceptionally wide bandwidth, a full helical circuit, without significant dimensional approximations, has not been successfully modeled until now. Numerous attempts have been made to analyze the helical slow-wave circuit so that the performance could be accurately predicted without actually building it, but because of its complex geometry, many geometrical approximations became necessary rendering the previous models inaccurate. In the course of this research it has been demonstrated that using the simulation code, MAFIA, the helical structure can be modeled with actual tape width and thickness, dielectric support rod geometry and materials. To demonstrate the accuracy of the MAFIA model, the cold-test parameters including dispersion, on-axis interaction impedance and attenuation have been calculated for several helical TWT slow-wave circuits with a variety of support rod geometries including rectangular and T-shaped rods, as well as various support rod materials including isotropic, anisotropic and partially metal coated dielectrics. Compared with experimentally measured results, the agreement is excellent. With the accuracy of the MAFIA helical model validated, the code was used to investigate several conventional geometric approximations in an attempt to obtain the most computationally efficient model. Several simplifications were made to a standard model including replacing the helical tape with filaments, and replacing rectangular support rods with shapes conforming to the cylindrical coordinate system with effective permittivity. The approximate models are compared with the standard model in terms of cold-test characteristics and computational time. The model was also used to determine the sensitivity of various circuit parameters including typical manufacturing dimensional tolerances and support rod permittivity. By varying the circuit parameters of an accurate model using MAFIA, these sensitivities can be computed for manufacturing concerns, and design optimization previous to fabrication, thus eliminating the need for costly experimental iterations. Several variations were made to a standard helical circuit using MAFIA to investigate the effect that variations on helical tape and support rod width, metallized loading height and support rod permittivity, have on TWT cold-test characteristics.
A new circuit model of HgCdTe photodiode for SPICE simulation of integrated IRFPA
NASA Astrophysics Data System (ADS)
Saxena, Raghvendra Sahai; Saini, Navneet Kaur; Bhan, R. K.; Sharma, R. K.
2014-11-01
We propose a novel sub circuit model to simulate HgCdTe infrared photodiodes in a circuit simulator, like PSPICE. We have used two diodes of opposite polarity in parallel to represent the forward biased and the reverse biased behavior of an HgCdTe photodiode separately. We also connected a resistor in parallel with them to represent the ohmic shunt and a constant current source to represent photocurrent. We show that by adjusting the parameters in standard diode models and the resistor and current values, we could actually fit the measured data of our various HgCdTe photodiodes having different characteristics. This is a very efficient model that can be used for simulation of readout integrated circuit (ROIC) for HgCdTe IR photodiode arrays. This model also allows circuit level Monte Carlo simulation on a complete IRFPA at a single circuit simulator platform to estimate the non-uniformity for given processes of HgCdTe device fabrication and Si ROIC fabrication.
Milton, Graeme W
2008-01-01
The electromagnetic analog of an elastic spring-mass network is constructed. These are called electromagnetic circuits and linear electrical circuits correspond to a subclass of them. They consist of thin triangular magnetic components joined at the edges by cylindrical dielectric components. Some of the edges can be terminal edges to which electric fields are applied. The response is measured in terms of the free currents associated with the terminal edges. The relation between the terminal electric fields and the terminal free currents is governed by a symmetric complex matrix W. In the case where all the terminal edges are disjoint, and the frequency is fixed, a complete characterization is obtained of all possible response matrices W, both in the lossless and lossy cases. There are also dual electromagnetic circuits consisting of thin triangular dielectric components joined at the edges by cylindrical magnetic components
Sub-Circuit Based SPICE Model for High Voltage LDMOS Transistors
NASA Astrophysics Data System (ADS)
Ankarcrona, J.; Olsson, J.
High voltage lateral DMOS transistors are very difficult to model due to the complex structure. As a result of complexity and the range of variation in transistor structure no general LDMOS model exists. Standard SPICE models of MOSFETs, JFETs together with a resistor have been used in the sub-circuit model. Self-heating effects have been included in a specially design unit. The model shows good overall accuracy.
Hu, Chia-Ren; HUANG, CH.
1991-01-01
PHYSICAL REVIEW B VOLUME 43, NUMBER 10 1 APRIL 1991 Phase boundary of a cubic superconducting circuit in a magnetic field of arbitrary magnitude and direction Chia-Ren Hu and Chen-Hong Huang Center for Theoretical Physics, Department of.... 1. The coordinate system used and the definition of [ 6;,i = 1 ?8 I relative to the coordinate system. 7720 CHIA-REN HU AND CHEN-HONG HUANG with ci =bi b?z/3, co=2bi/27 ?bib2/3+bc, and b2 = ?a2, b, =a,a, ?4ao, bo = ?(a, +aoa, ?4aoa, ).2 2...
MODELS FOR AN ANESTHESIA BREATHING CIRCUIT Paul E. Bigeleisen + and Margaret Cheney ++
Cheney, Margaret
MODELS FOR AN ANESTHESIA BREATHING CIRCUIT Paul E. Bigeleisen + and Margaret Cheney ++ + Department of Anesthesia, St. Paul Ramsey Medical Center, St. Paul, MN 55101; per manent address: Department4824. ABSTRACT This paper presents a mathematical model of a semiclosed anesthesia breathing cir cuit
DOI: 10.1002/adma.200702024 Random Circuit Breaker Network Model for Unipolar
Kahng, Byungnam
current Icomp, the TiO2 capacitor would experience a dielectric breakdown and be destroyed. HoweverDOI: 10.1002/adma.200702024 Random Circuit Breaker Network Model for Unipolar Resistance Switching origin is still far from being understood. In addition, no model exists that actually explains how
Technische Universiteit Delft
in Bipolar Circuit Design V. MilovanoviÂ´c* and S. MijalkoviÂ´c** *Delft Institute for Micro A reduction technique for an accurate modeling of complex effects manifested in an avalanche regime of bipolar is practically implemented on the bases of a vertical bipolar compact model Mextram. Extraction of an additional
Stefano Fusi; Wael F. Asaad; Earl K. Miller; Xiao-Jing Wang
2007-01-01
SUMMARY Volitional behavior relies on the brain's ability to remap sensory flow to motor programs when- ever demanded by a changed behavioral con- text. To investigate the circuit basis of such flexible behavior, we have developed a bio- physically based decision-making network model of spiking neurons for arbitrary sensori- motor mapping. The model quantitatively re- produces behavioral and prefrontal single-cell
NEURAL MODELS FOR SOCIAL DEVELOPMENT IN SHARED PARIETO-MOTOR CIRCUITS
Pitti, Alexandre
.ac.jp 2 E-mail address: kuniyosh@isi.imi.i.u-tokyo.ac.jp #12;Neural Models for Shared Parieto-MotorChapter 1 NEURAL MODELS FOR SOCIAL DEVELOPMENT IN SHARED PARIETO-MOTOR CIRCUITS Alexandre Pitti1 Intelligence Project, Japan. ISI laboratory, University of Tokyo, Japan. 1 E-mail address: alex@isi.imi.i.u-tokyo
Branching Patterns and Stepped Leaders in an Electric-Circuit Model for Creeping Discharge
Hidetsugu Sakaguchi; Sahim M. Kourkouss
2010-01-01
We construct a two-dimensional electric circuit model for creeping discharge. Two types of discharge, surface corona and surface leader, are modeled by a two-step function of conductance. Branched patterns of surface leaders surrounded by the surface corona appear in numerical simulation. The fractal dimension of branched discharge patterns is calculated by changing voltage and capacitance. We find that surface leaders
Masashi Kawaguchi; Chunlin Shao; Takashi Jimbo; Masayoshi Umeno
We proposed motion detection artificial vision model by the analog electronic circuits. Recently, the neuro chip and the artificial retina chip are developed. The structure of these chips is by the biomedical vision system and the neural network model. At present, basic image processing such as the edge detection and the image reversing has been achieved. In this research, we
Step-Wise Evolution of Mental Models of Electric Circuits: A "Learning-Aloud" Case Study.
ERIC Educational Resources Information Center
Clement, John J.; Steinberg, Melvin S.
2002-01-01
Describes an approach to teaching complex models in science that uses a model construction cycle of generation, evaluation, and modification. Reports on a case study of a student in a tutoring experiment in the study of electric circuits. Focuses on the role of analogies, discrepant events, and the student's moments of surprise as motivators of…
Mohsen Jalali; Mohammad K. Moravvej-Farshi; Saeid Masudy-Panah; Abdolreza Nabavi
2010-01-01
A staircase approximation method is deployed to model nonuniform field in the multiplication region and its surrounding ambient of a thin avalanche photodiode (APD). To the best of our knowledge, this is the first instance of introducing an equivalent circuit model that is taking the effect of the electric field profile in a thin APD's multiplication region and its surroundings
An equivalent circuit model of Frequency Selective Surfaces embedded within dielectric layers
Filippo Costa; Agostino Monorchio; Giuliano Manara
2009-01-01
A general equivalent circuit model for the analysis of frequency selective surfaces has been presented. The lumped parameters representing the periodic surface are explained and commented. Influence of thin dielectric substrates on FSS behavior is analyzed determining a simple model to correct the lumped parameters. FSS periodicity can be changed by scaling all lumped parameters by the initial and actual
Using Simple Circuits as Thermal Models for Your Home
NASA Astrophysics Data System (ADS)
Poynor, Adele
2014-02-01
In 2009, President Obama proposed an initiative to decrease our country's energy consumption and dependence on fossil fuels. One key to this plan was to decrease the amount of energy used to heat and cool our homes through government incentives. The EPA estimates that the average American household spends over 1000 annually for heating and cooling. One of the most cost-effective ways of decreasing energy use in your home is to stop air penetration and increase the amount of insulation by installing insulated doors, insulated windows, and cavity wall insulation. But not all options are equally effective, nor do they have equal costs. So how can consumers determine which option improves their homes' insulation the most? In this paper, I present an analogy to simple resistor circuits that can be used by introductory students to answer this question.
NASA Astrophysics Data System (ADS)
Engdahl, G.; Krah, J. H.
2002-04-01
A model for medium frequency power transformers is suggested. The model is able to treat arbitrary topologies by use of Cauer circuits for core and windings. An implementation example is given for a 1-phase transformer with turn ratio 1:1. The model can be extended to include winding insulation materials by use of lumped capacitive and resistive circuit elements.
A novel circuit model of double-heterojunction semiconductor laser diode
NASA Astrophysics Data System (ADS)
Fan, Hui; Lu, Yutian
2006-06-01
The issues of modeling the semiconductor laser with circuit elements have been addressed by several authors. Previously reported laser models are based upon rate equations and many relations between electron and photon. This needs the deep understanding of the clear physical meaning of all variables and the electrical and optical properties of the active region of a semiconductor laser diode. The relations and the formulas are very complex and the model's parameters are hard to get. In the previous models, node voltages are used as circuit variables. In practice the LD is powered by a constant or pulse current source. The node voltages are only measurable variables and decided by the input current for a ready-made LD. So taking the input current as the circuit variable is very simply and easy to understand and use. In this paper a circuit model of DHLD has been developed from rate equations and the well known models. Simulink module is built according to the rate equations. The input current is the only variable for the module. The transient response of the LD model is plotted. The simulating results such as transient and frequency responds agree well with the reported data.
Magnetic field diffusion modeling of a small enclosed firing system
Warne, L.K.; Merewether, K.O.
1996-01-01
Intense magnetic fields exist in the immediate vicinity of a lightning strike (and near power lines). Conducting barriers increase the rise time (and thus decrease the rise rate) interior to the barrier, but typically do not prevent penetration of the magnetic field, since the lightning current fall time may be larger than the barrier diffusion time. Thus, substantial energy is present in the interior field, although the degradation of rise rate makes it more difficult to couple into electrical circuits. This report assesses the threat posed by the diffusive magnetic field to interior components and wire loops (where voltages are induced). Analytical and numerical bounding analyses are carried out on a pill box shaped conducting barrier to develop estimates for the worst case magnetic field threats inside the system. Worst case induced voltages and energies are estimated and compared with threshold charge voltages and energies on the output capacitor of the system. Variability of these quantities with respect to design parameters are indicated. The interior magnetic field and induced voltage estimates given in this report can be used as excitations for more detailed interior and component models.
A new OLED SPICE model for pixel circuit simulation in OLED-on-silicon microdisplay design
NASA Astrophysics Data System (ADS)
Bohua, Zhao; Ran, Huang; Jianhui, Bu; Yinxue, Lü; Yiqi, Wang; Fei, Ma; Guohua, Xie; Zhensong, Zhang; Huan, Du; Jiajun, Luo; Zhengsheng, Han; Yi, Zhao
2012-07-01
A new equivalent circuit model of organic-light-emitting-diode (OLED) is proposed. As the single-diode model is able to approximate OLED behavior as well as the multiple-diode model, the new model will be built based on it. In order to make sure that the experimental and simulated data are in good agreement, the constant resistor is exchanged for an exponential resistor in the new model. Compared with the measured data and the results of the other two OLED SPICE models, the simulated I—V characteristics of the new model match the measured data much better. This new model can be directly incorporated into an SPICE circuit simulator and presents good accuracy over the whole operating voltage.
Microelectronic Devices and Circuits
NSDL National Science Digital Library
del Alamo, Jesus
The topics of this course include: modeling of microelectronic devices, basic microelectronic circuit analysis and design, physical electronics of semiconductor junction and MOS devices, relation of electrical behavior to internal physical processes, development of circuit models, and understanding the uses and limitations of various models. The course uses incremental and large-signal techniques to analyze and design bipolar and field effect transistor circuits, with examples chosen from digital circuits, single-ended and differential linear amplifiers, and other integrated circuits.
Akgul, Mehmet; Wu, Lingqi; Ren, Zeying; Nguyen, Clark T-C
2014-05-01
A small-signal equivalent circuit for parallel-plate capacitive-gap-transduced micromechanical resonators is introduced that employs negative capacitance to model the dependence of resonance frequency on electrical stiffness in a way that facilitates circuit analysis, that better elucidates the mechanisms behind certain potentially puzzling measured phenomena, and that inspires circuit topologies that maximize performance in specific applications. For this work, a micromechanical disk resonator serves as the vehicle with which to derive the equivalent circuits for both radial-contour and wine-glass modes, which are then used in circuit simulations (via simulation) to match measurements on actual fabricated devices. The new circuit model not only correctly predicts the dependence of electrical stiffness on the impedances loading the input and output electrodes of parallel-plate capacitive- gap-transduced micromechanical device, but does so in a visually intuitive way that identifies current drive as most appropriate for applications that must be stable against environmental perturbations, such as acceleration or power supply variations. Measurements on fabricated devices confirm predictions by the new model of up to 4× improvement in frequency stability against dc-bias voltage variations for contour- mode disk resonators as the resistance loading their ports increases. By enhancing circuit visualization, this circuit model makes more obvious the circuit design procedures and topologies most beneficial for certain mechanical circuits, e.g., filters and oscillators. PMID:24801124
Equivalent circuit of radio frequency-plasma with the transformer model.
Nishida, K; Mochizuki, S; Ohta, M; Yasumoto, M; Lettry, J; Mattei, S; Hatayama, A
2014-02-01
LINAC4 H(-) source is radio frequency (RF) driven type source. In the RF system, it is required to match the load impedance, which includes H(-) source, to that of final amplifier. We model RF plasma inside the H(-) source as circuit elements using transformer model so that characteristics of the load impedance become calculable. It has been shown that the modeling based on the transformer model works well to predict the resistance and inductance of the plasma. PMID:24593557
A large-signal GaAs MESFET model for nonlinear circuit simulation
Mohamed Imam; Mohamed A. Osman; Yolanda Prieto
1992-01-01
A GaAs MESFET large-signal model suitable for use in time-domain circuit simulation CAD tools such as PSPICE has been developed. The improved model includes accurate analytic representation of the transconductance and conductance dependence upon the operating voltages. The new model gives better fit to GaAs MESFET I-V characteristics over a wider bias voltage range compared with the Curtice quadratic model.
NASA Astrophysics Data System (ADS)
Tong, Shijie
Energy storage is one of society's grand challenges for the 21st century. Lithium ion batteries (LIBs) are widely used in mobile devices, transportation, and stationary energy storages due to lowering cost combined with excellent power/energy density as well as cycle durability. The need for a battery management system (BMS) arises from a demand to improve cycle life, assure safety, and optimize the full pack performance. In this work, we proposed a model based battery on-line state of charge (SoC) and state of health (SoH) estimator for LIBs. The estimator incorporates a comprehensive Equivalent Circuit Model (ECM) as reference, an Extended Kalman Filter (EKF) as state observer, a Recursive Least Square (RLS) algorithm as parameter identifier, and Parameter Varying Approach (PVA) based optimization algorithms for the parameter function regressions. The developed adaptive estimator was applied to a 10kW smart grid energy storage application using retired electric vehicle batteries. The estimator exhibits a high numerical efficiency as well as an excellent accuracy in estimating SoC and SoH. The estimator also provides a novel method to optimize the correlation between battery open circuit voltage (OCV) and SoC, which further improves states estimation accuracy.
Vazquez-Leal, H.; Jimenez-Fernandez, V. M.; Benhammouda, B.; Filobello-Nino, U.; Sarmiento-Reyes, A.; Ramirez-Pinero, A.; Marin-Hernandez, A.; Huerta-Chua, J.
2014-01-01
We present a homotopy continuation method (HCM) for finding multiple operating points of nonlinear circuits composed of devices modelled by using piecewise linear (PWL) representations. We propose an adaptation of the modified spheres path tracking algorithm to trace the homotopy trajectories of PWL circuits. In order to assess the benefits of this proposal, four nonlinear circuits composed of piecewise linear modelled devices are analysed to determine their multiple operating points. The results show that HCM can find multiple solutions within a single homotopy trajectory. Furthermore, we take advantage of the fact that homotopy trajectories are PWL curves meant to replace the multidimensional interpolation and fine tuning stages of the path tracking algorithm with a simple and highly accurate procedure based on the parametric straight line equation. PMID:25184157
Vazquez-Leal, H; Jimenez-Fernandez, V M; Benhammouda, B; Filobello-Nino, U; Sarmiento-Reyes, A; Ramirez-Pinero, A; Marin-Hernandez, A; Huerta-Chua, J
2014-01-01
We present a homotopy continuation method (HCM) for finding multiple operating points of nonlinear circuits composed of devices modelled by using piecewise linear (PWL) representations. We propose an adaptation of the modified spheres path tracking algorithm to trace the homotopy trajectories of PWL circuits. In order to assess the benefits of this proposal, four nonlinear circuits composed of piecewise linear modelled devices are analysed to determine their multiple operating points. The results show that HCM can find multiple solutions within a single homotopy trajectory. Furthermore, we take advantage of the fact that homotopy trajectories are PWL curves meant to replace the multidimensional interpolation and fine tuning stages of the path tracking algorithm with a simple and highly accurate procedure based on the parametric straight line equation. PMID:25184157
Yang, Shaolin; Ajilore, Olusola; Wu, Minjie; Lamar, Melissa; Kumar, Anand
2015-01-01
Previous research has shown that type 2 diabetes mellitus (T2DM) is associated with white matter microstructural changes, cognitive impairment, and decreased resting-state functional connectivity and spontaneous brain activity. This study used magnetization transfer imaging to examine, for the first time, the integrity of macromolecular protein pools in fronto-striato-thalamic circuits and its clinical and cognitive correlates in patients with T2DM. T2DM patients without mood disorders (n = 20, aged 65.05 ± 11.95 years) and healthy control subjects (HCs; n = 26, aged 62.92 ± 12.71 years) were recruited. Nodes of fronto-striato-thalamic circuits-head of the caudate nucleus (hCaud), putamen, globus pallidus, thalamus-and four cortical regions-rostral and dorsal anterior cingulate cortex, dorsolateral prefrontal cortex, and lateral orbitofrontal cortex-were examined. Compared with HCs, patients with T2DM had significantly lower magnetization transfer ratio (MTR) in bilateral anterior cingulate and hCaud. Reduced MTRs in the above regions showed correlations with T2DM-related clinical measures, including hemoglobin A1c level and vascular risk factors, and neuropsychological task performance in the domains of learning and memory, executive function, and attention and information processing. The impaired biophysical integrity of brain macromolecular protein pools and their local microenvironments in T2DM patients may provide insights into the neurological pathophysiology underlying diabetes-associated clinical and cognitive deficits. PMID:25092675
Mathematical modelling of magnetically targeted drug delivery
Andrew D. Grief; Giles Richardson
2005-01-01
A mathematical model for targeted drug delivery using magnetic particles is developed. This includes a diffusive flux of particles arising from interactions between erythrocytes in the microcirculation. The model is used to track particles in a vessel network. Magnetic field design is discussed and we show that it is impossible to specifically target internal regions using an externally applied field.
Quantitative model of the magnetospheric magnetic field
W. P. Olson; K. A. Pfitzer
1974-01-01
Quantitative representations of the magnetic fields associated with the magnetopause currents and the distributed currents (tail and quiet time ring currents) have been developed. These fields are used together with a dipole representation of the main field of the earth to model the total vector magnetospheric magnetic field. The model is based on quiet time data averaged over all 'tilt
Forward modelling of oceanic lithospheric magnetization
NASA Astrophysics Data System (ADS)
Masterton, S. M.; Gubbins, D.; Müller, R. D.; Singh, K. H.
2013-03-01
We construct a model of remanence for the oceans, combine it with a model of induced magnetization for the whole Earth from a previous study, compute the predicted lithospheric geomagnetic field and compare the result with a model, MF7, that is based on satellite data. Remanence is computed by assigning magnetizations to the oceanic lithosphere acquired at the location and time of formation. The magnetizing field is assumed to be an axial dipole that switches polarity with the reversal time scale. The magnetization evolves with time by decay of thermal remanence and acquisition of chemical remanence. The direction of remanence is calculated by Euler rotation of the original geomagnetic field direction with respect to an absolute reference frame, significantly improving previous results which did not include realistic oceanic magnetization computed this way. Remanence only accounts for 24 per cent of the energy of the oceanic magnetization, the induced magnetization being dominant, increasing slightly to 30 per cent of the part of the magnetization responsible for generating geomagnetic anomalies and 39 per cent of the Lowes energy of the geomagnetic anomalies. This is because our model of oceanic crust and lithosphere is fairly uniform, and a uniform layer magnetized by a magnetic field of internal origin produces no external field. The largest anomalies are produced by oceanic lithosphere magnetized during the Cretaceous Normal Superchron. Away from ridges and magnetic quiet zones the prediction fails to match the MF7 values; these are also generally, but not always, somewhat smaller than the observations. This may indicate that the magnetization estimates are too small, in which case the most likely error is in the poorly-known magnetization deep in the crust or upper mantle, or it may indicate some other source such as locally underplated continental lithosphere or anomalous oceanic crust, or even small-scale core fields.
Threshold flux-controlled memristor model and its equivalent circuit implementation
NASA Astrophysics Data System (ADS)
Wu, Hua-Gan; Bao, Bo-Cheng; Chen, Mo
2014-11-01
Modeling a memristor is an effective way to explore the memristor properties due to the fact that the memristor devices are still not commercially available for common researchers. In this paper, a physical memristive device is assumed to exist whose ionic drift direction is perpendicular to the direction of the applied voltage, upon which, corresponding to the HP charge-controlled memristor model, a novel threshold flux-controlled memristor model with a window function is proposed. The fingerprints of the proposed model are analyzed. Especially, a practical equivalent circuit of the proposed model is realized, from which the corresponding experimental fingerprints are captured. The equivalent circuit of the threshold memristor model is appropriate for various memristors based breadboard experiments.
CAD-oriented equivalent-circuit modeling of on-chip interconnects on lossy silicon substrate
Ji Zheng; Yeon-Chang Hahm; Vijai K. Tripathi; Andreas Weisshaar
2000-01-01
A new, comprehensive CAD-oriented modeling methodology for single and coupled interconnects on an Si-SiO2 substrate is presented. The modeling technique uses a modified quasi-static spectral domain electromagnetic analysis which takes into account the skin effect in the semiconducting substrate. Equivalent-circuit models with only ideal lumped elements, representing the broadband characteristics of the interconnects, are extracted. The response of the proposed
NASA Technical Reports Server (NTRS)
Courey, Karim; Wright, Clara; Asfour, Shihab; Onar, Arzu; Bayliss, Jon; Ludwig, Larry
2009-01-01
In this experiment, an empirical model to quantify the probability of occurrence of an electrical short circuit from tin whiskers as a function of voltage was developed. This empirical model can be used to improve existing risk simulation models. FIB and TEM images of a tin whisker confirm the rare polycrystalline structure on one of the three whiskers studied. FIB cross-section of the card guides verified that the tin finish was bright tin.
A high power circuit model for the gate turn off thyristor
C. L. Tsay; R. Fischl; J. Schwartzenberg; H. Kan; J. Barrow
1990-01-01
The authors present GTO (gate turn off thyristor) model which simulates both the static negative differential resistance characteristics and the dynamic switching characteristics. The model consists of parallel connection of two-transistor, three-resistor (2T-3R) circuits which make it compatible with the SPICE program. An experimental validation test shows that the accuracy of the model can be improved by increasing the number
Quantitative modeling and optimization of magnetic tweezers.
Lipfert, Jan; Hao, Xiaomin; Dekker, Nynke H
2009-06-17
Magnetic tweezers are a powerful tool to manipulate single DNA or RNA molecules and to study nucleic acid-protein interactions in real time. Here, we have modeled the magnetic fields of permanent magnets in magnetic tweezers and computed the forces exerted on superparamagnetic beads from first principles. For simple, symmetric geometries the magnetic fields can be calculated semianalytically using the Biot-Savart law. For complicated geometries and in the presence of an iron yoke, we employ a finite-element three-dimensional PDE solver to numerically solve the magnetostatic problem. The theoretical predictions are in quantitative agreement with direct Hall-probe measurements of the magnetic field and with measurements of the force exerted on DNA-tethered beads. Using these predictive theories, we systematically explore the effects of magnet alignment, magnet spacing, magnet size, and of adding an iron yoke to the magnets on the forces that can be exerted on tethered particles. We find that the optimal configuration for maximal stretching forces is a vertically aligned pair of magnets, with a minimal gap between the magnets and minimal flow cell thickness. Following these principles, we present a configuration that allows one to apply > or = 40 pN stretching forces on approximately 1-microm tethered beads. PMID:19527664
Mathematical Modeling and Analysis of Nonlinear Time-Invariant RLC Circuits
Reis, Timo
, television sets, cell phones, coffee machines and laptop computers (the latter two items have been heavily impact to the today's society. When electrical circuits are designed for specific purposes, there are phenomenon is ultimately caused by electromagnetic field effects, we present their mathematical model (namely
Reliability-yield allocation for semiconductor integrated circuits: modeling and optimization
Ha, Chunghun
2005-11-01
: : : : : : : : : : : : : : : : : : : : : : : : : : : 1 II DEFECTS AND DEFECT MANAGEMENT : : : : : : : : : : : : 8 II.1. Defect, Fault, Error, and Failure . . . . . . . . . . . . 8 II.2. Defect Management . . . . . . . . . . . . . . . . . . . 13 III YIELD AND RELIABILITY MODELS... : : : : : : : : : : : : : : : 17 III.1. Manufacturing Yield . . . . . . . . . . . . . . . . . . . 18 III.2. Reliability of Semiconductor Integrated Circuits . . . 19 III.3. Defect Size, Defect Density, and Critical Area . . . . . 22 III.4. Poisson and Negative Binomial Yield...
NASA Technical Reports Server (NTRS)
1976-01-01
Assumptions made and techniques used in modeling the power network to the 480 volt level are discussed. Basic computational techniques used in the short circuit program are described along with a flow diagram of the program and operational procedures. Procedures for incorporating network changes are included in this user's manual.
Open circuit voltage of vanadium redox flow batteries: Discrepancy between models and experiments
K. W. Knehr; E. C. Kumbur
2011-01-01
A major issue with the existing vanadium redox flow battery (VRFB) models is the inaccurate prediction of the open circuit voltage (OCV), which results in a discrepancy of 131 to 140mV in predicted cell voltages when compared to experimental data. This deviation is shown to be caused by the incomplete description of the electrochemical double layers within the cell when
Feng, Jianfeng
ÂHuxley models, Lymnaea stagnalis Abstract Central pattern generators (CPGs) are networks underlying rhythmic to the rhythmogenic circuit. In the feeding system of the pond snail, Lymnaea stagnalis, the extrinsic slow oscillator the CPG-driven motor pattern underlying feeding in the pond snail, Lymnaea (Fig. 1). One type of cell
Biological Circuit Models of Immune Regulatory Response: A Decentralized Control System
Peet, Matthew M.
Biological Circuit Models of Immune Regulatory Response: A Decentralized Control System Matthew control based on recently discovered regulatory properties of the immune system. The immune system. INTRODUCTION The purpose of this paper is to improve our understanding of the immune system by understanding
Circuit modeling of multiband high-impedance surface absorbers in the microwave regime
Yashwanth R. Padooru; Alexander B. Yakovlev; Chandra S. R. Kaipa; Francisco Medina; Francisco Mesa
2011-01-01
In this paper, we present a simple circuit model to study the absorption of electromagnetic waves by a multilayer structure with a high impedance surface in the microwave regime. The absorber consists of a stack of two-dimensional arrays of sub-wavelength meshes or patches separated by dielectric slabs and backed by a metallic ground plane, with a single resistive sheet placed
Analytical Drain Current Model of Nanoscale Strained-Si/SiGe MOSFETs for Analog Circuit Simulation
Kumar, M. Jagadesh
Analytical Drain Current Model of Nanoscale Strained-Si/SiGe MOSFETs for Analog Circuit Simulation for the output current characteristics (I-V) of nanoscale bulk strained-Si/SiGe MOSFETs, suitable for analog-based MOSFETs have reached remarkable levels of performance through device scaling. However, it is becoming
Equivalent circuit model of traveling-wave maser slow-wave structures
NASA Technical Reports Server (NTRS)
Shell, J.
1991-01-01
An approach is presented for deriving transmission line equivalent circuits that can approximately model the S-parameter response of traveling wave maser slow wave structures. The technique is illustrated by computing the S-parameter responses of an X-band and S-band maser slow wave structure and comparing these with experimental measurements.
Stress and Rodent Models of Drug Addiction: Role of VTA-Accumbens-PFC-Amygdala Circuit
Yap, Jasmine J.; Miczek, Klaus A.
2009-01-01
Stress can trigger, intensify, and prolong drug consumption, as well as reinstate previously extinguished drug-taking behavior by directly impacting a neural circuit often referred to as a reward pathways. Animal models of drug abuse have been used to understand these neural circuits mediating stress-induced drug intake and relapse through examination of cellular and subcellular molecular mechanisms. Several types of intermittent stressors have been shown to induce cross-sensitization to psychomotor stimulants, enhance conditioned place preference under most conditions, increase self-administration of cocaine and amphetamine and induce reinstatement of heroin and cocaine seeking via activation of the mesocorticolimbic dopamine system. PMID:20016773
NeuroGPS: automated localization of neurons for brain circuits using L1 minimization model
Quan, Tingwei; Zheng, Ting; Yang, Zhongqing; Ding, Wenxiang; Li, Shiwei; Li, Jing; Zhou, Hang; Luo, Qingming; Gong, Hui; Zeng, Shaoqun
2013-01-01
Drawing the map of neuronal circuits at microscopic resolution is important to explain how brain works. Recent progresses in fluorescence labeling and imaging techniques have enabled measuring the whole brain of a rodent like a mouse at submicron-resolution. Considering the huge volume of such datasets, automatic tracing and reconstruct the neuronal connections from the image stacks is essential to form the large scale circuits. However, the first step among which, automated location the soma across different brain areas remains a challenge. Here, we addressed this problem by introducing L1 minimization model. We developed a fully automated system, NeuronGlobalPositionSystem (NeuroGPS) that is robust to the broad diversity of shape, size and density of the neurons in a mouse brain. This method allows locating the neurons across different brain areas without human intervention. We believe this method would facilitate the analysis of the neuronal circuits for brain function and disease studies. PMID:23546385
Magnetic field screening effect in electroweak model
A. S. Bakry; D. G. Pak; P. M. Zhang; L. P. Zou
2014-10-03
It is shown that in the Weinberg-Salam model a magnetic field screening effect for static magnetic solutions takes place. The origin of this phenomenon can be traced to the mutual cancellation of Abelian magnetic fields created by the SU(2) gauge fields and Higgs boson. The effect implies monopole charge screening in the finite energy system of monopoles and antimonopoles. We consider another manifestation of the screening effect which leads to an essential energy decrease of magnetic solutions. Applying a variational method we have found a magnetic field configuration with a topological azimuthal magnetic flux which minimizes the energy functional and possesses a total energy of order 1 TeV. We suppose that a corresponding magnetic bound state exists in the electroweak theory and can be detected by experiment.
Computer circuit analysis of induced currents in the MFTF-B magnet system
Magnuson, G.D.; Woods, E.L.
1981-10-23
An analysis was made of the induced current behavior of the MFTF-B magnet system. Although the magnet system consists of 22 coils, because of its symmetry we considered only 11 coils in the analysis. Various combinations of the coils were dumped either singly or in groups, with the current behavior in all magnets calculated as a function of time after initiation of the dump.
Olfactory Functions Scale with Circuit Restoration in a Rapidly Reversible Alzheimer's Disease Model
Cheng, Ning; Bai, Li; Steuer, Elizabeth
2013-01-01
Neural circuits maintain a precise organization that is vital for normal brain functions and behaviors, but become disrupted during neurological disease. Understanding the connection between wiring accuracy and function to measure disease progression or recovery has been difficult because of the complexity of behavioral circuits. The olfactory system maintains well-defined neural connections that regenerate throughout life. We previously established a reversible in vivo model of Alzheimer's disease by overexpressing a humanized mutated amyloid precursor protein (hAPP) in olfactory sensory neurons (OSNs). Using this model, we currently show that hAPP is present in the OSN axons of mutant mice, which exhibit strong caspase3 signal and reduced synaptic protein expression by 3 weeks of age. In the olfactory bulb, we show that glomerular structure is distorted and OSN axonal convergence is lost. In vivo functional imaging experiments further demonstrate disruption of the glomerular circuitry, and behavioral assays reveal that olfactory function is significantly impaired. Because OSNs regenerate, we also tested if the system could recover from hAPP-induced disruption. We found that after 1 or 3 weeks of shutting-off hAPP expression, the glomerular circuit was partially restored both anatomically and functionally, with behavioral deficits similarly reversed. Interestingly, the degree of functional recovery tracked directly with circuit restoration. Together, these data demonstrate that hAPP-induced circuit disruption and subsequent recovery can occur rapidly and that behavior can provide a measure of circuit organization. Thus, olfaction may serve as a useful biomarker to both follow disease progression and gauge potential recovery. PMID:23884929
MOSFET modeling for analog circuit CAD: problems and prospects
Yannis P. Tsividis; Ken Suyama
1994-01-01
The requirements for good MOSFET modeling are discussed, as they apply to usage in analog and mixed analog-digital design. A set of benchmark tests that can be easily performed by the reader are given, and it is argued that most CAD models today cannot pass all the tests, even for simple, long-channel devices at room temperature. A number of other
A GLOBAL MAGNETIC TOPOLOGY MODEL FOR MAGNETIC CLOUDS. II
Hidalgo, M. A., E-mail: miguel.hidalgo@uah.es [Departamento de Fisica, Universidad de Alcala, Apartado 20, E-28871 Alcala de Henares, Madrid (Spain)
2013-04-01
In the present work, we extensively used our analytical approach to the global magnetic field topology of magnetic clouds (MCs), introduced in a previous paper, in order to show its potential and to study its physical consistency. The model assumes toroidal topology with a non-uniform (variable maximum radius) cross-section along them. Moreover, it has a non-force-free character and also includes the expansion of its cross-section. As is shown, the model allows us, first, to analyze MC magnetic structures-determining their physical parameters-with a variety of magnetic field shapes, and second, to reconstruct their relative orientation in the interplanetary medium from the observations obtained by several spacecraft. Therefore, multipoint spacecraft observations give the opportunity to infer the structure of this large-scale magnetic flux rope structure in the solar wind. For these tasks, we use data from Helios (A and B), STEREO (A and B), and Advanced Composition Explorer. We show that the proposed analytical model can explain quite well the topology of several MCs in the interplanetary medium and is a good starting point for understanding the physical mechanisms under these phenomena.
A GLOBAL MAGNETIC TOPOLOGY MODEL FOR MAGNETIC CLOUDS. I
Hidalgo, M. A. [Departamento de Fisica, Universidad de Alcala (Spain); Nieves-Chinchilla, T., E-mail: miguel.hidalgo@uah.es, E-mail: teresa.nieves-chinchil-1@nasa.gov [Institute for Astrophysics and Computational Sciences Catholic University of America, Washington, DC (United States)
2012-04-01
We present an analytical approach to the global magnetic field topology of magnetic clouds (MCs) that considers them like close magnetic structures with torus geometry and with a non-uniform (variable maximum radius) cross section along them. Following our previous approach to the problem of MCs (Hidalgo 2003, 2011), we establish an intrinsic coordinate system for that topology, and then we analytically solve the Maxwell equations in terms of it. The purpose of the present work is to present this model, which will lead us to understand in a more realistic way the physical mechanisms inside MCs. The model has a non-force-free character and also takes into account the time evolution of the cross sections of the MCs in their movement through the interplanetary medium. In this first paper, we obtain the expressions for the components of the magnetic field and the plasma current density imposing a large mean radius of the torus, and imposing a circular cross section with a variable maximum radius. Eventually, we fit the model to data related to four well-known MCs measurements at 1 AU, (three of them with circular cross sections and without expansion, as it is deduced from the experimental data). We compare the results of this toroidal model with those obtained with our previous cylindrical circular cross section model, also with a non-force-free character.
Theoretical analysis of microwave and millimeter wave integrated circuits based on magnetic films
NASA Astrophysics Data System (ADS)
Kong, J. A.
1991-11-01
A full modal analysis is used to study the dispersion characteristics of microstrip lines periodically loaded with crossing strips in a stratified uniaxially anisotropic medium. Dyadic Green's functions in the spectral domain for the multilayered medium in conjunction with the vector Fourier transform (VFT) are used to formulate a coupled set of vector integral equations for the current distribution on the signal line and the crossing strips. Galerkin's procedure is applied to derive the eigenvalue equation for the propagation constant. The effect of anisotropy for both open and shielded structures on the stopband properties is investigated. The input impedance of a microstrip antenna consisting of two circular microstrip disks in a stacked configuration driven by a coaxial probe is investigated. A rigorous analysis is performed using a dyadic Green's function formulation where the mixed boundary value problem is reduced to a set of coupled vector integral equations using the vector Hankel transform. Galerkin's method is employed in the spectral domain where two sets of disk current expansions are used. One set is based on the complete set of orthogonal modes of the magnetic cavity, and the other employs Chebyshev polynomials with the proper edge condition for the disk currents. An additional term is added to the disk current expansion to properly model the current in the vicinity of the probe/disk junction.
A smart card CMOS circuit with magnetic power and communication interface
J. Bouvier; Y. Thorigne; S. A. Hassan; M. J. Revillet; P. Senn
1997-01-01
On-chip magnetic interface provides power supply and communication for a chip dedicated to contactless smart card applications. Smart cards equipped with a chip, instead of a magnetic ribbon, are becoming widely used due to the reliability at system level. Contactless solutions present advantages: reduced card cost (no bonding), and improved system reliability due to the absence of electrical contacts between
Analysis, modeling, and simulation of series-parallel resonant converter circuits
Siu-Chung Wong; Andrew D. Brown
1995-01-01
This paper presents a SPICE macromodel for a generic series-parallel resonant converter circuit. The model is derived from the averaged time-invariant state-space equations obtained from a Fourier transform. The conditions are derived under which all but the fundamental harmonic may be discarded, and the model developed based solely on the fundamental Fourier component. The single macromodel developed has a wide
Krylov-Subspace Methods for Reduced-Order Modeling in Circuit Simulation
Roland W. Freund
1999-01-01
The simulation of electronic circuits involves the numerical solution of very largescale,sparse, in general nonlinear, systems of differential-algebraic equations. Often,the size of these systems can be reduced considerably by replacing the equationscorresponding to linear subcircuits by approximate models of much smaller statespacedimension. In this paper, we describe the use of Krylov-subspace methodsfor generating such reduced-order models of linear subcircuits. Particular
Equivalent Circuit Model for Thick Split Ring Resonators and Thick Spiral Resonators
Mancera, Laura Maria Pulido
2014-01-01
A simple theoretical model which provides circuit parameters and resonance frequency of metallic thick resonators is presented. Two different topologies were studied: the original Pendry's SRR and spiral resonators of two and three turns. Theoretical computations of resonant frequencies are in good agreement with values obtained with a commercial electromagnetic solver. The model could be helpful for designing thick frequency selective surfaces (FSS) based on this types of resonators, so called metasurfaces.
Branching Patterns and Stepped Leaders in an Electric-Circuit Model for Creeping Discharge
NASA Astrophysics Data System (ADS)
Hidetsugu Sakaguchi,; Sahim M. Kourkouss,
2010-06-01
We construct a two-dimensional electric circuit model for creeping discharge. Two types of discharge, surface corona and surface leader, are modeled by a two-step function of conductance. Branched patterns of surface leaders surrounded by the surface corona appear in numerical simulation. The fractal dimension of branched discharge patterns is calculated by changing voltage and capacitance. We find that surface leaders often grow stepwise in time, as is observed in lightning leaders of thunder.
Numerical investigation on thermal–hydraulic performance of new printed circuit heat exchanger model
Dong Eok Kim; Moo Hwan Kim; Jae Eun Cha; Seong O. Kim
2008-01-01
Three-dimensional numerical analysis was performed to investigate heat transfer and pressure drop characteristics of supercritical CO2 flow in new Printed Circuit Heat Exchanger (PCHE) model using commercial CFD code, Fluent 6.3. First, numerical analysis for conventional zigzag channel PCHE model was performed and compared with previous experimental data. Maximum deviation of in-outlet temperature difference and pressure drop from experimental data
A computational model for epidural electrical stimulation of spinal sensorimotor circuits.
Capogrosso, Marco; Wenger, Nikolaus; Raspopovic, Stanisa; Musienko, Pavel; Beauparlant, Janine; Bassi Luciani, Lorenzo; Courtine, Grégoire; Micera, Silvestro
2013-12-01
Epidural electrical stimulation (EES) of lumbosacral segments can restore a range of movements after spinal cord injury. However, the mechanisms and neural structures through which EES facilitates movement execution remain unclear. Here, we designed a computational model and performed in vivo experiments to investigate the type of fibers, neurons, and circuits recruited in response to EES. We first developed a realistic finite element computer model of rat lumbosacral segments to identify the currents generated by EES. To evaluate the impact of these currents on sensorimotor circuits, we coupled this model with an anatomically realistic axon-cable model of motoneurons, interneurons, and myelinated afferent fibers for antagonistic ankle muscles. Comparisons between computer simulations and experiments revealed the ability of the model to predict EES-evoked motor responses over multiple intensities and locations. Analysis of the recruited neural structures revealed the lack of direct influence of EES on motoneurons and interneurons. Simulations and pharmacological experiments demonstrated that EES engages spinal circuits trans-synaptically through the recruitment of myelinated afferent fibers. The model also predicted the capacity of spatially distinct EES to modulate side-specific limb movements and, to a lesser extent, extension versus flexion. These predictions were confirmed during standing and walking enabled by EES in spinal rats. These combined results provide a mechanistic framework for the design of spinal neuroprosthetic systems to improve standing and walking after neurological disorders. PMID:24305828
Total dose and dose rate models for bipolar transistors in circuit simulation.
Campbell, Phillip Montgomery; Wix, Steven D.
2013-05-01
The objective of this work is to develop a model for total dose effects in bipolar junction transistors for use in circuit simulation. The components of the model are an electrical model of device performance that includes the effects of trapped charge on device behavior, and a model that calculates the trapped charge densities in a specific device structure as a function of radiation dose and dose rate. Simulations based on this model are found to agree well with measurements on a number of devices for which data are available.
SiC JFET Transistor Circuit Model for Extreme Temperature Range
NASA Technical Reports Server (NTRS)
Neudeck, Philip G.
2008-01-01
A technique for simulating extreme-temperature operation of integrated circuits that incorporate silicon carbide (SiC) junction field-effect transistors (JFETs) has been developed. The technique involves modification of NGSPICE, which is an open-source version of the popular Simulation Program with Integrated Circuit Emphasis (SPICE) general-purpose analog-integrated-circuit-simulating software. NGSPICE in its unmodified form is used for simulating and designing circuits made from silicon-based transistors that operate at or near room temperature. Two rapid modifications of NGSPICE source code enable SiC JFETs to be simulated to 500 C using the well-known Level 1 model for silicon metal oxide semiconductor field-effect transistors (MOSFETs). First, the default value of the MOSFET surface potential must be changed. In the unmodified source code, this parameter has a value of 0.6, which corresponds to slightly more than half the bandgap of silicon. In NGSPICE modified to simulate SiC JFETs, this parameter is changed to a value of 1.6, corresponding to slightly more than half the bandgap of SiC. The second modification consists of changing the temperature dependence of MOSFET transconductance and saturation parameters. The unmodified NGSPICE source code implements a T(sup -1.5) temperature dependence for these parameters. In order to mimic the temperature behavior of experimental SiC JFETs, a T(sup -1.3) temperature dependence must be implemented in the NGSPICE source code. Following these two simple modifications, the Level 1 MOSFET model of the NGSPICE circuit simulation program reasonably approximates the measured high-temperature behavior of experimental SiC JFETs properly operated with zero or reverse bias applied to the gate terminal. Modification of additional silicon parameters in the NGSPICE source code was not necessary to model experimental SiC JFET current-voltage performance across the entire temperature range from 25 to 500 C.
Vector spin modeling for magnetic tunnel junctions with voltage dependent effects
Manipatruni, Sasikanth, E-mail: sasikanth.manipatruni@intel.com; Nikonov, Dmitri E.; Young, Ian A. [Exploratory Integrated Circuits, Components Research, Intel Corp., Hillsboro, Oregon 97124 (United States)
2014-05-07
Integration and co-design of CMOS and spin transfer devices requires accurate vector spin conduction modeling of magnetic tunnel junction (MTJ) devices. A physically realistic model of the MTJ should comprehend the spin torque dynamics of nanomagnet interacting with an injected vector spin current and the voltage dependent spin torque. Vector spin modeling allows for calculation of 3 component spin currents and potentials along with the charge currents/potentials in non-collinear magnetic systems. Here, we show 4-component vector spin conduction modeling of magnetic tunnel junction devices coupled with spin transfer torque in the nanomagnet. Nanomagnet dynamics, voltage dependent spin transport, and thermal noise are comprehended in a self-consistent fashion. We show comparison of the model with experimental magnetoresistance (MR) of MTJs and voltage degradation of MR with voltage. Proposed model enables MTJ circuit design that comprehends voltage dependent spin torque effects, switching error rates, spin degradation, and back hopping effects.
S. S. Chung; D. C. Chen; C. T. Cheng; C. F. Yeh
1996-01-01
A poly-Si TFT model for circuit simulation in Spice is presented, combined with a device degradation model for the first time to evaluate the circuit reliability. Both I-V and C-V models for the whole device operating regime have been developed. In the I-V model, emphasis has been taken to derive the mobility degradation induced by the grain boundary potential barrier
Modeling and optimization of permanent magnetic motors
Pinkham, Andrew P
2008-01-01
This thesis develops analytic models for the prediction and optimization of radial-flux permanent magnet motor torque and efficiency. It also facilitates the design optimization of electromagnetically-powered rotorcraft ...
Yu Wang; Hong Luo; Ku He; Rong Luo; Huazhong Yang; Yuan Xie
2011-01-01
As technology scales, Negative Bias Temperature Instability (NBTI), which causes temporal performance degradation in digital circuits by affecting PMOS threshold voltage, is emerging as one of the major circuit reliability concerns. In this paper, we first investigate the impact of NBTI on PMOS devices and propose a temporal performance degradation model that considers the temperature variation between active and standby
Continental and oceanic crustal magnetization modelling
NASA Technical Reports Server (NTRS)
Harrison, C. G. A.; Hayling, K. L.
1984-01-01
Inversion of magnetic data from the MAGSAT satellite, to arrive at intensities of magnetization of the Earth's crust, was performed by two different methods. The first method uses a spherical harmonic model of the magnetic field. The coefficients believed to represent sources in the Earth's crust can then be inverted to arrive at vertical dipole moments per unit area at the Earth's surface. The spherical harmonic models contain coefficients of degrees of harmonics up to 23. The dipole moment per unit area for a surface element can then be determined by summing the contribution for each individual degree of harmonic. The magnetic moments were calculated for continental and oceanic areas separately as well as over certain latitudinal segments. Of primary concern was to determine whether there are any differences between continental and oceanic areas. The second analysis with magnetization intensities was made using narrower ranges of degrees of harmonics, assuming that higher degrees are present in the core field signal.
Surface-charge-based micro-models— a solid foundation for learning about direct current circuits
NASA Astrophysics Data System (ADS)
Hirvonen, P. E.
2007-05-01
This study explores how the use of a surface-charge-based instructional approach affects introductory university level students' understanding of direct current (dc) circuits. The introduced teaching intervention includes electrostatics, surface-charge-based micro-models that explain the existence of an electric field inside the current-carrying wire, and traditional Kirchhoff's laws that are based on the conservation principles of energy and charge. The study group consisted of 32 students, 5 of whom were carefully monitored during the course. The results show that students' pre-knowledge includes various naïve micro-models related to electric current. Students try to create connections between electrostatics and dc circuits by themselves without the concept of an electric field. During the intervention, the students abandoned naïve models almost completely. In the final exam, approximately 30% of the students reached the level of desired understanding and 50% of the students reached an understanding that can be considered as a good basis for further studies. Generally, the introduced instructional approach can be recommended because it explains dc circuits holistically, based on conservation principles and offers digestible micro-level models. These matters help students to abandon their naïve models.
Approaches for modeling magnetic nanoparticle dynamics.
Reeves, Daniel B; Weaver, John B
2014-01-01
Magnetic nanoparticles are useful biological probes as well as therapeutic agents. Several approaches have been used to model nanoparticle magnetization dynamics for both Brownian as well as Neel rotation. Magnetizations are often of interest and can be compared with experimental results. Here we summarize these approaches, including the Stoner-Wohlfarth approach and stochastic approaches including thermal fluctuations. Non-equilibrium-related temperature effects can be described by a distribution function approach (Fokker-Planck equation) or a stochastic differential equation (Langevin equation). Approximate models in several regimes can be derived from these general approaches to simplify implementation. PMID:25271360
The Circuit Theory Behind Coupled-Mode Magnetic Resonance-Based Wireless Power Transmission.
Kiani, Mehdi; Ghovanloo, Maysam
2012-09-01
Inductive coupling is a viable scheme to wirelessly energize devices with a wide range of power requirements from nanowatts in radio frequency identification tags to milliwatts in implantable microelectronic devices, watts in mobile electronics, and kilowatts in electric cars. Several analytical methods for estimating the power transfer efficiency (PTE) across inductive power transmission links have been devised based on circuit and electromagnetic theories by electrical engineers and physicists, respectively. However, a direct side-by-side comparison between these two approaches is lacking. Here, we have analyzed the PTE of a pair of capacitively loaded inductors via reflected load theory (RLT) and compared it with a method known as coupled-mode theory (CMT). We have also derived PTE equations for multiple capacitively loaded inductors based on both RLT and CMT. We have proven that both methods basically result in the same set of equations in steady state and either method can be applied for short- or midrange coupling conditions. We have verified the accuracy of both methods through measurements, and also analyzed the transient response of a pair of capacitively loaded inductors. Our analysis shows that the CMT is only applicable to coils with high quality factor (Q) and large coupling distance. It simplifies the analysis by reducing the order of the differential equations by half compared to the circuit theory. PMID:24683368
Two-dimensional solar cell simulations by means of circuit modeling
Kerschaver, E. van; Nijs, J.; Mertens, R. [IMEC vzw, Heverlee (Belgium); Ghannam, M. [Kuwait Univ., Safat (Kuwait)
1997-12-31
In this work, the authors present a circuit model to perform multidimensional solar cell simulations. This model allows for incorporating effects of lateral current flows in solar cells, keeping the required time and computer resources relatively low. The use and sensitivity of the model will be described based on its application towards the design of metallization patterns for locally passivated back surface structures. As a second application the authors present the usage of the model to study the influence of different cell parameters such as surface recombination velocities and cell thickness on its performance.
A phenomenological constitutive model for magnetic shape memory alloys
Kiefer, Bjoern
2007-04-25
A thermodynamics-based constitutive model is derived which predicts the nonlinear strain and magnetization response that magnetic shape memory alloys (MSMAs) exhibit when subjected to mechanical and magnetic loads. The model development is conducted...
A comparative study of equivalent circuit models of ultracapacitors for electric vehicles
NASA Astrophysics Data System (ADS)
Zhang, Lei; Wang, Zhenpo; Hu, Xiaosong; Sun, Fengchun; Dorrell, David G.
2015-01-01
This paper comparatively examines three types of equivalent circuit models for ultracapacitors. They are the classic model, the multi-stage ladder model and the dynamic model. These models are consciously selected from the state-of-the-art lumped models reported in the literature. A test rig is developed and used to load the ultracapacitor and to collect the test data. The genetic algorithm (GA) is employed to extract the optimal model parameters based on the Hybrid Pulse Power Characterization (HPPC) test. The performance of these models is evaluated and compared by measuring the model complexity, accuracy, and robustness against 'unseen' data collected in the Dynamic Stress Test (DST) and a self-designed pulse test (SDP). The validation results show that the dynamic model has the best overall performance.
NASA Astrophysics Data System (ADS)
Pinkham, Raymond; Anderson, Daniel F.
1986-08-01
The continuing advancements in integrated circuit technology have placed new burdons on the circuit design engineer, who must rely extensively upon computer simulation to correctly predict circuit behavior. One challenge is to develop better modelling techniques to more accurately deal with complex p- n junction structures often used in modern VLSI designs. This paper presents an easily implemented method for deriving parameters which accurately model the behavior of MOS VLSI structures containing complex p- n junction capacitance components. The methodology is applicable to both planar and laterally diffused junctions, whether formed by direct ion implantation or by diffusion from a finite or infinite source. The theories behind the equations used and results of the application of this new technique are discussed. A flow chart for a fitter program based on the new method is presented and described. The corresponding program written for the TI-59 scientific programmable calculator is available. Final model parameters are given and are shown to produce a numerical capacitance model which is accurate to within 2%.
Accurate Cold-Test Model of Helical TWT Slow-Wave Circuits
NASA Technical Reports Server (NTRS)
Kory, Carol L.; Dayton, James A., Jr.
1997-01-01
Recently, a method has been established to accurately calculate cold-test data for helical slow-wave structures using the three-dimensional electromagnetic computer code, MAFIA. Cold-test parameters have been calculated for several helical traveling-wave tube (TWT) slow-wave circuits possessing various support rod configurations, and results are presented here showing excellent agreement with experiment. The helical models include tape thickness, dielectric support shapes and material properties consistent with the actual circuits. The cold-test data from this helical model can be used as input into large-signal helical TWT interaction codes making it possible, for the first time, to design a complete TWT via computer simulation.
Gneiding, N., E-mail: Natalia.Gneiding@physik.uni-erlangen.de [Erlangen Graduate School in Advanced Optical Technologies (SAOT), University of Erlangen-Nuremberg, 91052 Erlangen (Germany); Zhuromskyy, O.; Peschel, U. [Institute of Optics, Information and Photonics, University of Erlangen-Nuremberg, 91058 Erlangen (Germany); Shamonina, E. [Department of Engineering Science, University of Oxford, Parks Road, OX1 3PJ Oxford (United Kingdom)
2014-10-28
Metamaterials are comprised of metallic structures with a strong response to incident electromagnetic radiation, like, for example, split ring resonators. The interaction of resonator ensembles with electromagnetic waves can be simulated with finite difference or finite elements algorithms, however, above a certain ensemble size simulations become inadmissibly time or memory consuming. Alternatively a circuit description of metamaterials, a well developed modelling tool at radio and microwave frequencies, allows to significantly increase the simulated ensemble size. This approach can be extended to the IR spectral range with an appropriate set of circuit element parameters accounting for physical effects such as electron inertia and finite conductivity. The model is verified by comparing the coupling coefficients with the ones obtained from the full wave numerical simulations, and used to optimize the nano-antenna design with improved radiation characteristics.
Modifications and Modeling of the Fission Surface Power Primary Test Circuit (FSP-PTC)
NASA Technical Reports Server (NTRS)
Garber, Anne E.
2008-01-01
An actively pumped alkali metal flow circuit, designed and fabricated at the NASA Marshall Space Flight Center, underwent a range of tests at MSFC in early 2007. During this period, system transient responses and the performance of the liquid metal pump were evaluated. In May of2007, the circuit was drained and cleaned to prepare for multiple modifications: the addition of larger upper and lower reservoirs, the installation of an annular linear induction pump (ALIP), and the inclusion of a closeable orifice in the test section. Performance of the ALIP, provided by Idaho National Laboratory (INL), will be evaluated when testing resumes. Data from the first round of testing has been used to refine the working system model, developed using the Generalized Fluid System Simulation Program (GFSSP). This paper covers the modifications of the FSP-PTC and the updated GFSSP system model.
NASA Astrophysics Data System (ADS)
Gneiding, N.; Zhuromskyy, O.; Shamonina, E.; Peschel, U.
2014-10-01
Metamaterials are comprised of metallic structures with a strong response to incident electromagnetic radiation, like, for example, split ring resonators. The interaction of resonator ensembles with electromagnetic waves can be simulated with finite difference or finite elements algorithms, however, above a certain ensemble size simulations become inadmissibly time or memory consuming. Alternatively a circuit description of metamaterials, a well developed modelling tool at radio and microwave frequencies, allows to significantly increase the simulated ensemble size. This approach can be extended to the IR spectral range with an appropriate set of circuit element parameters accounting for physical effects such as electron inertia and finite conductivity. The model is verified by comparing the coupling coefficients with the ones obtained from the full wave numerical simulations, and used to optimize the nano-antenna design with improved radiation characteristics.
Accurate Cold-Test Model of Helical TWT Slow-Wave Circuits
NASA Technical Reports Server (NTRS)
Kory, Carol L.; Dayton, James A., Jr.
1998-01-01
Recently, a method has been established to accurately calculate cold-test data for helical slow-wave structures using the three-dimensional (3-D) electromagnetic computer code, MAxwell's equations by the Finite Integration Algorithm (MAFIA). Cold-test parameters have been calculated for several helical traveLing-wave tube (TWT) slow-wave circuits possessing various support rod configurations, and results are presented here showing excellent agreement with experiment. The helical models include tape thickness, dielectric support shapes and material properties consistent with the actual circuits. The cold-test data from this helical model can be used as input into large-signal helical TWT interaction codes making It possible, for the first time, to design complete TWT via computer simulation.
Accurate Cold-Test Model of Helical TWT Slow-Wave Circuits
NASA Technical Reports Server (NTRS)
Kory, Carol L.; Dayton, J. A., Jr.
1998-01-01
Recently, a method has been established to accurately calculate cold-test data for helical slow-wave structures using the three-dimensional (3-D) electromagnetic computer code, MAFIA. Cold-test parameters have been calculated for several helical traveling-wave tube (TWT) slow-wave circuits possessing various support rod configurations, and results are presented here showing excellent agreement with experiment. The helical models include tape thickness, dielectric support shapes and material properties consistent with the actual circuits. The cold-test data from this helical model can be used as input into large-signal helical TWT interaction codes making it possible, for the first time, to design a complete TWT via computer simulation.
Reduced-order modeling of large passive linear circuits by means of the SYPVL algorithm
Roland W. Freund; Peter Feldmann
1996-01-01
. This paper discusses the analysis of large linear electrical networks consistingof passive components, resistors, capacitors, inductors, transformers, etc. Such networksresult in a symmetric formulation of circuit equations. The paper introduces SyPVL, anefficient and numerically stable algorithm for the computation of reduced-order models oflarge, linear, passive networks. SyPVL represents the specialization of the more generalPVL algorithm, to symmetric problems. Besides
A circuit-compatible model of ballistic carbon nanotube field-effect transistors
Arijit Raychowdhury; Saibal Mukhopadhyay; Kaushik Roy
2004-01-01
Carbon nanotube field-effect transistors (CNFETs) are being extensively studied as possible successors to CMOS. Novel device structures have been fabricated and device simulators have been developed to estimate their performance in a sub-10-nm transistor era. This paper presents a novel method of circuit-compatible modeling of single-walled semiconducting CNFETs in their ultimate performance limit. For the first time, both the I-V
Introduction of a Base-Model for Eddy Current Testing of Printed Circuit Boards
Hossein Bayani; Masanobu Nishino; Sotoshi Yamada; Masayoshi Iwahara
2008-01-01
In this paper we propose a model to reproduce printed circuit board (PCB) pattern eddy current testing signals based on 3D finite-element method (FEM) package and scanning simulation. In this method we consider some common PCB elements as test pieces while a simple Meander-type coil is utilized as excitation coil above the elements. Numerical solution to the above problem with
Advanced neural network model of plasma-driven integrated circuit process data
Byungwhan Kim; Changki Min; Donghwan Kim
2007-01-01
Plasma processes are key means to deposit or etch thin films during the manufacture of integrated circuits. An advanced model of plasma process data was constructed by applying genetic algorithm to the set of typical training factors combined with multi-parameterized gradients of neuron activation functions. The presented technique was evaluated with plasma etch data, collected during silica etching in CHF3-CF4
Magnetic Refrigeration Development
NASA Technical Reports Server (NTRS)
Deardoff, D. D.; Johnson, D. L.
1984-01-01
Magnetic refrigeration is being developed to determine whether it may be used as an alternative to the Joule-Thomson circuit of a closed cycle refrigerator for providing 4 K refrigeration. An engineering model 4-15 K magnetic refrigerator has been designed and is being fabricated. This article describes the overall design of the magnetic refrigerator.
The interplay of plasticity and adaptation in neural circuits: a generative model
Bernacchia, Alberto
2014-01-01
Multiple neural and synaptic phenomena take place in the brain. They operate over a broad range of timescales, and the consequences of their interplay are still unclear. In this work, I study a computational model of a recurrent neural network in which two dynamic processes take place: sensory adaptation and synaptic plasticity. Both phenomena are ubiquitous in the brain, but their dynamic interplay has not been investigated. I show that when both processes are included, the neural circuit is able to perform a specific computation: it becomes a generative model for certain distributions of input stimuli. The neural circuit is able to generate spontaneous patterns of activity that reproduce exactly the probability distribution of experienced stimuli. In particular, the landscape of the phase space includes a large number of stable states (attractors) that sample precisely this prior distribution. This work demonstrates that the interplay between distinct dynamical processes gives rise to useful computation, and proposes a framework in which neural circuit models for Bayesian inference may be developed in the future. PMID:25400577
NASA Astrophysics Data System (ADS)
Zhao, Hongliang; Liu, Xinghui; Xu, Chao
2013-11-01
A low power cryogenic readout integrated circuit (ROIC) for 512 × 512-pixel infrared focal plane array (IRFPA) image system, is presented. In order to improve the precision of the circuit simulation at cryogenic temperatures, a modified MOS device model is proposed. The model is based on BSIM3 model, and uses correction parameters to describe carrier freeze-out effect at low temperatures to improve the fitting accuracy for low temperature MOS device simulation. A capacitive trans-impedance amplifier (CTIA) with inherent correlated double sampling (CDS) configuration is employed to realize a high performance readout interfacing circuit in a pixel area of 30 × 30 ?m2. Optimized column readout timing and structure are applied to reduce the power consumption. The experimental chip fabricated by a standard 0.35 ?m 2P4M CMOS process shows more than 10 MHz readout rate with less than 70 mW power consumption under 3.3 V supply voltage at 77-150 K operated temperatures. And it occupies an area of 18 × 17 mm2.
Modeling the Sun's open magnetic flux
NASA Astrophysics Data System (ADS)
Schüssler, M.; Baumann, I.
2006-12-01
Context: .The heliospheric magnetic field can be extrapolated from the photospheric field distribution using models based upon various approximations. Such models are required for the reconstruction of the open solar magnetic flux prior to the time of direct measurements on the basis of surface flux transport simulations. Aims: .We evaluate the consistency of extrapolation models with direct measurements of the heliospheric magnetic field. Furthermore, we study whether extrapolations on the basis of a surface flux transport model for the photospheric magnetic field reproduce the temporal evolution of the measured near-Earth magnetic field. Methods: .We use the potential field source surface (PFSS) model and the current sheet source surface (CSSS) model to extrapolate the heliospheric field on the basis of the Wilcox Solar Observatory (WSO) synoptic maps of the solar surface field from 1976-2005. The results are compared with the near-Earth measurements of the radial heliospheric field and its independence of latitude found with Ulysses. Furthermore, we determine extrapolations on the basis of photospheric flux distributions computed with a surface flux transport code, using as input sunspot group areas from the SOON database. Results: .The CSSS model based upon WSO data, with a source surface located at ?10~R? and cusp surface at 1.7~R?, yields the best agreement with the measurements. The flux transport simulations reproduce the observed surface flux together with the open flux if the tilt angle of emerging bipolar magnetic regions is smaller than commonly assumed, but consistent with sunspot observations. Conclusions: .The CSSS model with a source surface in the vicinity of the Alfvénic point of the solar wind leads to a good extrapolation of the heliospheric field from solar surface data. A surface flux transport model based upon sunspot data with consistently calibrated tilt angles reproduces the observed evolution of the solar total open flux.
Reentrant excitation in an analog-digital hybrid circuit model of cardiac tissue
NASA Astrophysics Data System (ADS)
Mahmud, Farhanahani; Shiozawa, Naruhiro; Makikawa, Masaaki; Nomura, Taishin
2011-06-01
We propose an analog-digital hybrid circuit model of one-dimensional cardiac tissue with hardware implementation that allows us to perform real-time simulations of spatially conducting cardiac action potentials. Each active nodal compartment of the tissue model is designed using analog circuits and a dsPIC microcontroller, by which the time-dependent and time-independent nonlinear current-voltage relationships of six types of ion channel currents employed in the Luo-Rudy phase I (LR-I) model for a single mammalian cardiac ventricular cell can be reproduced quantitatively. Here, we perform real-time simulations of reentrant excitation conduction in a ring-shaped tissue model that includes eighty nodal compartments. In particular, we show that the hybrid tissue model can exhibit real-time dynamics for initiation of reentries induced by uni-directional block, as well as those for phase resetting that leads to annihilation of the reentry in response to impulsive current stimulations at appropriate nodes and timings. The dynamics of the hybrid model are comparable to those of a spatially distributed tissue model with LR-I compartments. Thus, it is conceivable that the hybrid model might be a useful tool for large scale simulations of cardiac tissue dynamics, as an alternative to numerical simulations, leading toward further understanding of the reentrant mechanisms.
NASA Astrophysics Data System (ADS)
Yun, J.; Shim, J.-I.; Shin, D.-S.
2013-08-01
We demonstrate a modeling method based on the three-dimensional electrical and thermal circuit analysis to extract current, voltage and temperature distributions of light-emitting diodes (LEDs). In our model, the electrical circuit analysis is performed first to extract the current and voltage distributions in the LED. Utilizing the result obtained from the electrical circuit analysis as distributed heat sources, the thermal circuit is set up by using the duality between Fourier's law and Ohm's law. From the analysis of the thermal circuit, the temperature distribution at each epitaxial film is successfully obtained. Comparisons of experimental and simulation results are made by employing an InGaN/GaN multiple-quantum-well blue LED. Validity of the electrical circuit analysis is confirmed by comparing the light distribution at the surface. Since the temperature distribution at each epitaxial film cannot be obtained experimentally, the apparent temperature distribution is compared at the surface of the LED chip. Also, experimentally obtained average junction temperature is compared with the value calculated from the modeling, yielding a very good agreement. The analysis method based on the circuit modeling has an advantage of taking distributed heat sources as inputs, which is essential for high-power devices with significant self-heating.
The slender solar tachocline: a magnetic model
G. Rudiger; L. L. Kitchatinov
1997-01-01
A model for the sharp transition from differential rotation in the solar convection zone to rigid rotation in the radiative interior is presented. Differential rotation in the radiative zone is shown to be quenched efficiently by an internal magnetic field. The poloidal field amplitude, B_0, is the input parameter for our model which determines the transition layer thickness and the
Global magnetization models with a priori information
NASA Astrophysics Data System (ADS)
Purucker, Michael E.; Langel, Robert A.; Rajaram, Mita; Raymond, Carol
1998-02-01
In an effort to explore the possible effects of change in integrated magnetization at the continent-ocean boundary and to account for such effects in modeling, an inverse technique is developed which allows for the inclusion of a priori information in models of global crustal magnetization or susceptibility. This technique accounts for processing effects such as main and external field removal. An a priori model consisting of an ocean-continent magnetic contrast, oceanic topography, and remanent magnetization in the Cretaceous quiet zones is constructed using equivalent source dipoles. Previous investigations using similar models utilize only forward modeling procedures. We show how this a priori model can be modified so that the resulting computed field, after removal of spherical harmonics below some specified degree ("main field" removal) and along track filtering ("external field" removal), matches that of the robust POGO-Magsat anomaly map in a least squares sense. The dependence of the final model on the a priori information is also investigated. Between degrees 20 and 60 the final models are found to be almost identical for reasonable a priori conditions. An example from the Gulf of Mexico and surrounding Gulf Coast region serves to illustrate the utility of the technique. High heat flow,>40° C/km, is observed in much of the Gulf Coast region. The example suggests that the elevated heat flow persists at depth and has elevated the Curie point.
Circuit modeling and performance analysis of SWCNT bundle 3D interconnects
NASA Astrophysics Data System (ADS)
Libo, Qian; Zhangming, Zhu; Ruixue, Ding; Yintang, Yang
2013-09-01
Metallic carbon nanotubes (CNTs) have been proposed as a promising alternative to Cu interconnects in future integrated circuits (ICs) for their remarkable conductive, mechanical and thermal properties. Compact equivalent circuit models for single-walled carbon nanotube (SWCNT) bundles are described, and the performance of SWCNT bundle interconnects is evaluated and compared with traditional Cu interconnects at different interconnect levels for through-silicon-via-based three dimensional (3D) ICs. It is shown that at a local level, CNT interconnects exhibit lower signal delay and smaller optimal wire size. At intermediate and global levels, the delay improvement becomes more significant with technology scaling and increasing wire lengths. For 1 mm intermediate and 10 mm global level interconnects, the delay of SWCNT bundles is only 49.49% and 52.82% that of the Cu wires, respectively.
An equivalent circuit model and power calculations for the APS SPX crab cavities.
Berenc, T. (Accelerator Systems Division (APS))
2012-03-21
An equivalent parallel resistor-inductor-capacitor (RLC) circuit with beam loading for a polarized TM110 dipole-mode cavity is developed and minimum radio-frequency (rf) generator requirements are calculated for the Advanced Photon Source (APS) short-pulse x-ray (SPX) superconducting rf (SRF) crab cavities. A beam-loaded circuit model for polarized TM110 mode crab cavities was derived. The single-cavity minimum steady-state required generator power has been determined for the APS SPX crab cavities for a storage ring current of 200mA DC current as a function of external Q for various vertical offsets including beam tilt and uncontrollable detuning. Calculations to aid machine protection considerations were given.
An Analysis on Synchronous Reluctance Motors by Use of Magnetic Circuit
NASA Astrophysics Data System (ADS)
Kondo, Minoru
The synchronous reluctance motors operated by a PWM inverter can be designed for the maximum saliency ratio (Ld/Lq). The saliency ratio is the most important parameter for achieving a high torque capability, high power factor and wide constant-power speed range. Generally, flux guides for the d-axis and flux barriers for the q-axis are provided to achieve a high Ld and low Lq, respectively, in order to maximize the saliency ratio. In this paper, the optimal shape and thickness of the flux barriers are investigated analytically. It is also demonstrated that the optimal rotor flux barrier shape can be expressed as the contour line of the function that shows the magnetic potential in a uniform material rotor. The effects of the magnetic resistance of the stator and the gap are also analyzed.
MYERS,DAVID R.; JESSING,JEFFREY R.; SPAHN,OLGA B.; SHANEYFELT,MARTY R.
2000-01-01
This project represented a coordinated LLNL-SNL collaboration to investigate the feasibility of developing radiation-hardened magnetic non-volatile memories using giant magnetoresistance (GMR) materials. The intent of this limited-duration study was to investigate whether giant magnetoresistance (GMR) materials similar to those used for magnetic tunnel junctions (MTJs) were process compatible with functioning CMOS circuits. Sandia's work on this project demonstrated that deposition of GMR materials did not affect the operation nor the radiation hardness of Sandia's rad-hard CMOS technology, nor did the integration of GMR materials and exposure to ionizing radiation affect the magnetic properties of the GMR films. Thus, following deposition of GMR films on rad-hard integrated circuits, both the circuits and the films survived ionizing radiation levels consistent with DOE mission requirements. Furthermore, Sandia developed techniques to pattern deposited GMR films without degrading the completed integrated circuits upon which they were deposited. The present feasibility study demonstrated all the necessary processing elements to allow fabrication of the non-volatile memory elements onto an existing CMOS chip, and even allow the use of embedded (on-chip) non-volatile memories for system-on-a-chip applications, even in demanding radiation environments. However, funding agencies DTRA, AIM, and DARPA did not have any funds available to support the required follow-on technology development projects that would have been required to develop functioning prototype circuits, nor were such funds available from LDRD nor from other DOE program funds.
Analytical dynamic modeling of a cantilever IPMC actuator based on a distributed electrical circuit
NASA Astrophysics Data System (ADS)
Moeinkhah, Hossein; Rezaeepazhand, Jalil; Akbarzadeh, Alireza
2013-05-01
Ionic polymer-metal composite (IPMC) has a wide range of applications in robotics, biomedical devices and artificial muscles. The modeling of the IPMC actuator is a multi-physics task as it involves electricity, chemistry, dynamics and control. Due to its complexity and its nonlinearity, IPMC modeling is difficult and its behavior is still not fully agreed upon by researchers. In this paper, a dynamic model of a cantilever IPMC actuator based on a distributed RC electrical circuit is developed. The RC transmission line theory is used to derive the simple analytical impedance and actuation model of an IPMC actuator. This method permits us to identify the current and voltage as functions of polymer length and frequency. First, an infinite-dimensional impedance model is developed and then replaced with a simple second-order electro-mechanical model using the Golubev method. The proposed modeling approach is validated using existing experimental data.
R. Grisel; L. A. Coyitangiye; A. Doukkali; F. Barbier; P. Descamps; H. Murray
2009-01-01
A new equivalent circuit suitable for transient simulation methodology of Gate-Grounded NMOS transistor (ggNMOS) used in Electrostatic Discharge (ESD) protection circuits is proposed in this paper. The target technology is a classical CMOS 0.25 ¿m. This model, contrary to classical I-V static model, is intended to cover the dynamic comportment of the ggNMOS during all the phases of the Transmission
Lei Zhu; Ke Wu
1999-01-01
Unified dynamic equivalent-circuit model for characterizing planar unbounded discontinuities is reported for use in the field-theory-based computer-aided design and optimization of high-frequency integrated circuits and structures such as monolithic and hybrid microwave integrated circuits (M(H)MIC's). The proposal of the circuit model is stemmed from a new scheme called the short-open calibration (SOC) technique. This SOC technique is directly accommodated in
A Framework for Quantitative Modeling of Neural Circuits Involved in Sleep-to-Wake Transition
Sorooshyari, Siamak; Huerta, Ramón; de Lecea, Luis
2015-01-01
Identifying the neuronal circuits and dynamics of sleep-to-wake transition is essential to understanding brain regulation of behavioral states, including sleep–wake cycles, arousal, and hyperarousal. Recent work by different laboratories has used optogenetics to determine the role of individual neuromodulators in state transitions. The optogenetically driven data do not yet provide a multi-dimensional schematic of the mechanisms underlying changes in vigilance states. This work presents a modeling framework to interpret, assist, and drive research on the sleep-regulatory network. We identify feedback, redundancy, and gating hierarchy as three fundamental aspects of this model. The presented model is expected to expand as additional data on the contribution of each transmitter to a vigilance state becomes available. Incorporation of conductance-based models of neuronal ensembles into this model and existing models of cortical excitability will provide more comprehensive insight into sleep dynamics as well as sleep and arousal-related disorders. PMID:25767461
NASA Technical Reports Server (NTRS)
Balakrishna, S.; Goglia, G. L.
1979-01-01
The details of the efforts to synthesize a control-compatible multivariable model of a liquid nitrogen cooled, gaseous nitrogen operated, closed circuit, cryogenic pressure tunnel are presented. The synthesized model was transformed into a real-time cryogenic tunnel simulator, and this model is validated by comparing the model responses to the actual tunnel responses of the 0.3 m transonic cryogenic tunnel, using the quasi-steady-state and the transient responses of the model and the tunnel. The global nature of the simple, explicit, lumped multivariable model of a closed circuit cryogenic tunnel is demonstrated.
Testing the Model of Oscillating Magnetic Traps
NASA Astrophysics Data System (ADS)
Szaforz, ?.; Tomczak, M.
2015-01-01
The aim of this paper is to test the model of oscillating magnetic traps (the OMT model), proposed by Jakimiec and Tomczak ( Solar Phys. 261, 233, 2010). This model describes the process of excitation of quasi-periodic pulsations (QPPs) observed during solar flares. In the OMT model energetic electrons are accelerated within a triangular, cusp-like structure situated between the reconnection point and the top of a flare loop as seen in soft X-rays. We analyzed QPPs in hard X-ray light curves for 23 flares as observed by Yohkoh. Three independent methods were used. We also used hard X-ray images to localize magnetic traps and soft X-ray images to diagnose thermal plasmas inside the traps. We found that the majority of the observed pulsation periods correlates with the diameters of oscillating magnetic traps, as was predicted by the OMT model. We also found that the electron number density of plasma inside the magnetic traps in the time of pulsation disappearance is strongly connected with the pulsation period. We conclude that the observations are consistent with the predictions of the OMT model for the analyzed set of flares.
NASA Astrophysics Data System (ADS)
Linaro, Daniele; Righero, Marco; Biey, Mario; Storace, Marco
This paper uses synchronization as a tool for further validating a circuit (HR-PWL circuit) recently proposed in the literature and based on a piecewise-linear (PWL) approximation of the Hindmarsh-Rose (HR) neuron model. The accuracy of the single neuron hardware implementation has been already validated through bifurcation analysis tools. Here, the synchronization behavior of networks formed by HR neurons is simulated and compared to that of companion networks of PWL neurons, with the purpose of validating the HR-PWL circuit also from a collective behavior point of view. In the considered cases, the neurons are connected either by linear diffusive or by nonlinear sigmoidal coupling, with different topologies. The analysis is based on the Master Stability Function approach and is verified by extensive numerical time-domain simulations. The synchronization properties of the PWL neuron networks turn out to be qualitatively very similar to those of the companion HR networks, confirming the validity of the proposed hardware-implemented neuron.
Transport Properties of Soils and Spectral Electrical Response: Equivalent Circuit Models
NASA Astrophysics Data System (ADS)
Boadu, F. K.
2002-05-01
Non-invasive prediction of hydraulic properties of soils (hydraulic conductivity, porosity, and degree of saturation) from surface measurement techniques as provided by geophysical methods is appealing to geoscientists involved in groundwater and pollution control problems. There is the need, however, to understand how the hydraulic properties of soil influence their spectral electrical response (SER). Laboratory measurements of the spectral electrical response of over 30 soil samples taken from different sites across North Carolina were performed within the frequency range from 0.01 Hz to 10 kHz. The hydraulic conductivity, porosity, and moisture content of each soil sample were measured. Both the moisture content and the degree of compaction were controlled for each soil sample to simulate field conditions. The SER measurements are used to estimate the hydraulic conductivity and porosity of soils. The SER of a soil is modeled as a heterogeneous multiphase system using an equivalent circuit model. The intrinsic parameters, which describe the response of the model, are retrieved by an inversion scheme and are used in empirical regression models to predict the hydraulic conductivity and porosity. Multiple regression analyses suggest that the porosity and permeability can be well predicted by the parameters of the equivalent circuit model. Such direct relationships between parameters characterizing the spectral electrical response of soils and their hydraulic properties may provide versatile non-invasive methodology of obtaining hydraulic conductivity and porosity of soils using geophysical measurements.
Sammoura, Firas; Kim, Sang-Gook
2012-05-01
An electric circuit model for a circular bimorph piezoelectric micromachined ultrasonic transducer (PMUT) was developed for the first time. The model was made up of an electric mesh, which was coupled to a mechanical mesh via a transformer element. The bimorph PMUT consisted of two piezoelectric layers of the same material, having equal thicknesses, and sandwiched between three thin electrodes. The piezoelectric layers, having the same poling axis, were biased with electric potentials of the same magnitude but opposite polarity. The strain mismatches between the two layers created by the converse piezoelectric effect caused the membrane to vibrate and, hence, transmit a pressure wave. Upon receiving the echo of the acoustic wave, the membrane deformation led to the generation of electric charges as a result of the direct piezoelectric phenomenon. The membrane angular velocity and electric current were related to the applied electric field, the impinging acoustic pressure, and the moment at the edge of the membrane using two canonical equations. The transduction coefficients from the electrical to the mechanical domain and vice-versa were shown to be bilateral and the system was shown to be reversible. The circuit parameters of the derived model were extracted, including the transformer ratio, the clamped electric impedance, the spring-softening impedance, and the open-circuit mechanical impedance. The theoretical model was fully examined by generating the electrical input impedance and average plate displacement curves versus frequency under both air and water loading conditions. A PMUT composed of piezoelectric material with a lossy dielectric was also investigated and the maximum possible electroacoustical conversion efficiency was calculated. PMID:22622984
Pe, T.; McDonald, J.; Clem, J.R.
1995-12-31
The voltage V{sub ab} measured between two voltage taps a and b during magnetic flux transport in a type-II superconductor carrying current I is the sum of two contributions, the line integral from a to b of the electric field along an arbitrary path C{sub s} through the superconductor and a term proportional to the time rate of change of magnetic flux through the area bounded by the path C{sub s} and the measuring circuit leads. When the current I(t) is oscillating with time t, the apparent ac loss (the time average of the product IV{sub ab}) depends upon the measuring circuit used. Only when the measuring-circuit leads are brought out far from the surface does the apparent power dissipation approach the real (or true) ac loss associated with the length of sample probed. Calculations showing comparisons between the apparent and real ac losses in a flat strip of rectangular cross section will be presented, showing the behavior as a function of the measuring-circuit dimensions. Corresponding calculations also are presented for a sample of elliptical cross section.
NASA Astrophysics Data System (ADS)
Clark, D.
2012-12-01
Magnetics is the most widely used geophysical method in hard rock exploration and magnetic surveys are an integral part of exploration programs for many types of mineral deposit, including porphyry Cu, intrusive-related gold, volcanic-hosted epithermal Au, IOCG, VMS, and Ni sulfide deposits. However, the magnetic signatures of ore deposits and their associated mineralized systems are extremely variable and exploration that is based simply on searching for signatures that resemble those of known deposits and systems is rarely successful. Predictive magnetic exploration models are based upon well-established geological models, combined with magnetic property measurements and geological information from well-studied deposits, and guided by magnetic petrological understanding of the processes that create, destroy and modify magnetic minerals in rocks. These models are designed to guide exploration by predicting magnetic signatures that are appropriate to specific geological settings, taking into account factors such as tectonic province; protolith composition; post-formation tilting/faulting/ burial/ exhumation and partial erosion; and metamorphism. Patterns of zoned hydrothermal alteration are important indicators of potentially mineralized systems and, if properly interpreted, can provided vectors to ore. Magnetic signatures associated with these patterns at a range of scales can provide valuable information on prospectivity and can guide drilling, provided they are correctly interpreted in geological terms. This presentation reviews effects of the important types of hydrothermal alteration on magnetic properties within mineralized systems, with particular reference to porphyry copper and IOCG deposits. For example, an unmodified gold-rich porphyry copper system, emplaced into mafic-intermediate volcanic host rocks (such as Bajo de la Alumbrera, Argentina) exhibits an inner potassic zone that is strongly mineralized and magnetite-rich, which is surrounded by an outer potassic zone that contains less abundant, but still significant, magnetite. The inner potassic zone represents relatively intense development of qtz-mt-Kfsp veins, whereas the outer potassic zone corresponds to bio-Kfsp-qtz-mt alteration. A shell of magnetite-destructive phyllic alteration with very low susceptibility envelops the potassic zones. The phyllic zone is surrounded by a zone of intense propylitic alteration, which is partially magnetite-destructive, which passes out into weak propylitic alteration and then into unaltered, moderately magnetic volcanics. For such a system, emplaced into magnetic intermediate-mafic igneous host rocks and exposed after removal by erosion of ~ 1 km of overburden, a strong central RTP high is surrounded by a relatively weak annular low over the phyllic zone, gradually returning to background levels over the propylitic zone (an "archery target" signature). For a completely buried system, however, the signature is basically an alteration low due to the large volume of magnetite-destructive alteration surrounding the deeply buried magnetic core.
Orbital magnetism in coupled-bands models
NASA Astrophysics Data System (ADS)
Raoux, Arnaud; Piéchon, Frédéric; Fuchs, Jean-Noël; Montambaux, Gilles
2015-02-01
We develop a gauge-independent perturbation theory for the grand potential of itinerant electrons in two-dimensional tight-binding models in the presence of a perpendicular magnetic field. At first order in the field, we recover the result of the so-called modern theory of orbital magnetization and, at second order, deduce a new general formula for the orbital susceptibility. In the special case of two coupled bands, we relate the susceptibility to geometrical quantities such as the Berry curvature. Our results are applied to several two-band systems—either gapless or gapped. We point out some surprising features in the orbital susceptibility—such as in-gap diamagnetism and parabolic band-edge paramagnetism—coming from interband coupling. From this we draw general conclusions on the orbital magnetism of itinerant electrons in multiband tight-binding models.
Variation of the global electric circuit and Ionospheric potential in a general circulation model
NASA Astrophysics Data System (ADS)
Mareev, E. A.; Volodin, E. M.
2014-12-01
A general circulation model of the atmosphere and ocean INMCM4.0 (Institute of Numerical Mathematics Coupled Model) is used for modeling the global electric circuit short-time variability and long-term evolution. The ionospheric potential parameterization is proposed which takes into account quasi-stationary currents of electrified clouds (including thunderstorms) as principal contributors into the DC global circuit. The diurnal, seasonal, and interannual variations of the ionospheric potential (IP) are modeled and compared with available data. Numerical simulations suggest that the IP decreases in the mean with the global warming due to increasing greenhouse gas emission (by about 10% during the 21st century if the Representative Concentration Pathway 8.5 Wm-2 scenario is assumed). At the same time the lightning flash rate increases with global warming by about 5 fl/s per degree. Interannual IP variability is low and does not exceed 1% of the mean value, being tightly correlated with the mean sea surface temperature in the Pacific Ocean (El Niño area).
Smyth, Katherine; Kim, Sang-Gook
2015-04-01
An analytical Mason equivalent circuit is derived for a circular, clamped plate piezoelectric micromachined ultrasonic transducer (pMUT) design in 31 mode, considering an arbitrary electrode configuration at any axisymmetric vibration mode. The explicit definition of lumped parameters based entirely on geometry, material properties, and defined constants enables straightforward and wide-ranging model implementation for future pMUT design and optimization. Beyond pMUTs, the acoustic impedance model is developed for universal application to any clamped, circular plate system, and operating regimes including relevant simplifications are identified via the wave number-radius product ka. For the single-electrode fundamental vibration mode case, sol-gel Pb(Zr0.52)Ti0.48O3 (PZT) pMUT cells are microfabricated with varying electrode size to confirm the derived circuit model with electrical impedance measurements. For the first time, experimental and finite element simulation results are successfully applied to validate extensive electrical, mechanical, and acoustic analytical modeling of a pMUT cell for wide-ranging applications including medical ultrasound, nondestructive testing, and range finding. PMID:25881352
Mcconaghy, Trent; Gielen, Georges
2011-01-01
This paper presents a method to automatically generate compact symbolic performance models of analog circuits with no prior specification of an equation template. The approach takes SPICE simulation data as input, which enables modeling of any nonlinear circuits and circuit characteristics. Genetic programming is applied as a means of traversing the space of possible symbolic expressions. A grammar is specially designed to constrain the search to a canonical form for functions. Novel evolutionary search operators are designed to exploit the structure of the grammar. The approach generates a set of symbolic models which collectively provide a tradeoff between error and model complexity. Experimental results show that the symbolic models generated are compact and easy to understand, making this an effective method for aiding understanding in analog design. The models also demonstrate better prediction quality than posynomials.
Coupled wave model for large magnet coils
NASA Technical Reports Server (NTRS)
Gabriel, G. J.
1980-01-01
A wave coupled model based on field theory is evolved for analysis of fast electromagnetic transients on superconducting coils. It is expected to play a useful role in the design of protection methods against damage due to high voltages or any adverse effects that might arise from unintentional transients. The significant parameters of the coil are identified to be the turn to turn wave coupling coefficients and the travel time of an electromagnetic disturbance around a single turn. Unlike circuit theoretic inductor, the coil response evolves in discrete steps having durations equal to this travel time. It is during such intervals that high voltages are likely to occur. The model also bridges the gap between the low and high ends of the frequency spectrum.
Doll, Caleb A.; Broadie, Kendal
2014-01-01
Early-use activity during circuit-specific critical periods refines brain circuitry by the coupled processes of eliminating inappropriate synapses and strengthening maintained synapses. We theorize these activity-dependent (A-D) developmental processes are specifically impaired in autism spectrum disorders (ASDs). ASD genetic models in both mouse and Drosophila have pioneered our insights into normal A-D neural circuit assembly and consolidation, and how these developmental mechanisms go awry in specific genetic conditions. The monogenic fragile X syndrome (FXS), a common cause of heritable ASD and intellectual disability, has been particularly well linked to defects in A-D critical period processes. The fragile X mental retardation protein (FMRP) is positively activity-regulated in expression and function, in turn regulates excitability and activity in a negative feedback loop, and appears to be required for the A-D remodeling of synaptic connectivity during early-use critical periods. The Drosophila FXS model has been shown to functionally conserve the roles of human FMRP in synaptogenesis, and has been centrally important in generating our current mechanistic understanding of the FXS disease state. Recent advances in Drosophila optogenetics, transgenic calcium reporters, highly-targeted transgenic drivers for individually-identified neurons, and a vastly improved connectome of the brain are now being combined to provide unparalleled opportunities to both manipulate and monitor A-D processes during critical period brain development in defined neural circuits. The field is now poised to exploit this new Drosophila transgenic toolbox for the systematic dissection of A-D mechanisms in normal versus ASD brain development, particularly utilizing the well-established Drosophila FXS disease model. PMID:24570656
NASA Astrophysics Data System (ADS)
Mertz, Benjamin E.
Single dielectric barrier discharge (SDBD) plasma actuators have been applied to a wide variety of aerodynamic flow control applications ranging from stall suppression of airfoils at high angles of attack to reducing tip leakage in jet engine turbine blades. With increased interest in applying plasma actuators to various engineering problems comes the need for an efficient model of the actuators that can be used in a CFD simulation. Prior to the current work, a model was developed that captured many of the spatial and temporal dynamics of the actuator by using circuits consisting of resistors and capacitors to model the plasma and dielectric material. In the current work, this model was refined by casting the governing equations in terms of a generalized coordinate system so that it can be applied to curved surfaces, the grid dependence of the model was eliminated, and the method of applying this model as a boundary condition to the electrostatic equations to calculate the body forces generated by the actuator was studied. This new formulation of the lumped circuit element model was then validated against various experimental observations including force vector orientation needed to produce observed induced flow, the scaling of the force with input voltage, and the directivity patterns and pressure time-series from acoustic measurements. The model was also implemented in a flow solver for the case of an impulsively started actuator on a flat plate and compared to experimental data found in literature. Finally, the utility of the model was demonstrated by simulating the use of actuators for flow control of the flow over a circular cylinder and a modified blunt trailing edge wind turbine blade.
Models: Electric and Magnetic Interactions, Teacher's Guide.
ERIC Educational Resources Information Center
Karplus, Robert
The unit presented in this teacher's guide is one of two developed for the sixth and final year in the Science Curriculum Improvement Study (SCIS) curriculum. The concept of a scientific model is introduced in this unit with activities directed toward increasing student understanding of electric and magnetic phenomena through concrete experience…
2$\\\\,\\\\times\\\\,$ 25kV 50 Hz High-Speed Traction Power System: Short-Circuit Modeling
Luigi Battistelli; Mario Pagano; Daniela Proto
2011-01-01
A2 25-kV 50 Hz traction power system was an- alyzed and modeled in the time domain in order to simulate short-circuit conditions and to attain a practical method to iden- tify the short circuit behavior of the traction system. In particular, due to the difficulty in assessing the track-line parameters which mainly depend on changing environmental conditions, the pos- sibility
Triangular Bose-Hubbard trimer as a minimal model for a superfluid circuit
NASA Astrophysics Data System (ADS)
Arwas, Geva; Vardi, Amichay; Cohen, Doron
2014-01-01
The triangular Bose-Hubbard trimer is topologically the minimal model for a BEC superfluid circuit. As a dynamical system of two coupled freedoms it has mixed phase space with chaotic dynamics. We employ a semiclassical perspective to study triangular trimer physics beyond the conventional picture of the superfluid-to-insulator transition. From the analysis of the Peierls-Nabarro energy landscape, we deduce the various regimes in the (?,u) parameter space, where u is the interaction and ? is the superfluid rotation-velocity. We thus characterize the superfluid stability and chaoticity of the many-body eigenstates throughout the Hilbert space.
Ueda, Masanori; Iwaki, Masafumi; Nishihara, Tokihiro; Satoh, Yoshio; Hashimoto, Ken-ya
2008-04-01
This paper describes a circuit model for the analysis of nonlinearity in the filters based on radiofrequency (RF) bulk acoustic wave (BAW) resonators. The nonlinear output is expressed by a current source connected parallel to the linear resonator. Amplitude of the nonlinear current source is programmed proportional to the product of linear currents flowing in the resonator. Thus, the nonlinear analysis is performed by the common linear analysis, even for complex device structures. The analysis is applied to a ladder-type RF BAW filter, and frequency dependence of the nonlinear output is discussed. Furthermore, this analysis is verified through comparison with experiments. PMID:18467229
Design and analysis of perfect terahertz metamaterial absorber by a novel dynamic circuit model.
Hokmabadi, Mohammad Parvinnezhad; Wilbert, David S; Kung, Patrick; Kim, Seongsin M
2013-07-15
Metamaterial terahertz absorbers composed of a frequency selective layer followed by a spacer and a metallic backplane have recently attracted great attention as a device to detect terahertz radiation. In this work, we present a quasistatic dynamic circuit model that can decently describe operational principle of metamaterial terahertz absorbers based on interference theory of reflected waves. The model comprises two series LC resonance components, one for resonance in frequency selective surface (FSS) and another for resonance inside the spacer. Absorption frequency is dominantly determined by the LC of FSS while the spacer LC changes slightly the magnitude and frequency of absorption. This model fits perfectly for both simulated and experimental data. By using this model, we study our designed absorber and we analyze the effect of changing in spacer thickness and metal conductivity on absorption spectrum. PMID:23938496
Model Spectrum of Magnetic Induction Caused by Ambient Internal Waves
Robert A. Petersen; Kenneth A. Poehls
1982-01-01
Internal waves propagating in electrically conductive seawater induce weak secondary magnetic fields in the presence of the earth's magnetic field. The two-dimensional (frequency and wave number) magnetic induction spectrum caused by ambient internal waves is estimated by using the Garrett and Munk model spectrum of ocean internal waves. Because it involves convolution integrals over depth, the magnetic induction model spectrum
An improved electrical and thermal model of a microbolometer for electronic circuit simulation
NASA Astrophysics Data System (ADS)
Würfel, D.; Vogt, H.
2012-09-01
The need for uncooled infrared focal plane arrays (IRFPA) for imaging systems has increased since the beginning of the nineties. Examples for the application of IRFPAs are thermography, pedestrian detection for automotives, fire fighting, and infrared spectroscopy. It is very important to have a correct electro-optical model for the simulation of the microbolometer during the development of the readout integrated circuit (ROIC) used for IRFPAs. The microbolometer as the sensing element absorbs infrared radiation which leads to a change of its temperature due to a very good thermal insulation. In conjunction with a high temperature coefficient of resistance (TCR) of the sensing material (typical vanadium oxide or amorphous silicon) this temperature change results in a change of the electrical resistance. During readout, electrical power is dissipated in the microbolometer, which increases the temperature continuously. The standard model for the electro-optical simulation of a microbolometer includes the radiation emitted by an observed blackbody, radiation emitted by the substrate, radiation emitted by the microbolometer itself to the surrounding, a heat loss through the legs which connect the microbolometer electrically and mechanically to the substrate, and the electrical power dissipation during readout of the microbolometer (Wood, 1997). The improved model presented in this paper takes a closer look on additional radiation effects in a real IR camera system, for example the radiation emitted by the casing and the lens. The proposed model will consider that some parts of the radiation that is reflected from the casing and the substrate is also absorbed by the microbolometer. Finally, the proposed model will include that some fraction of the radiation is transmitted through the microbolometer at first and then absorbed after the reflection at the surface of the substrate. Compared to the standard model temperature and resistance of the microbolometer can be modelled more realistically when these higher order effects are taken into account. A Verilog-A model for electronic circuit simulations is developed based on the improved thermal model of the microbolometer. Finally, a simulation result of a simple circuit is presented.
Chen, Chang Hao; Pun, Sio Hang; Mak, Peng Un; Vai, Mang I; Klug, Achim; Lei, Tim C.
2014-01-01
Glass micropipettes are widely used to record neural activity from single neurons or clusters of neurons extracellularly in live animals. However, to date, there has been no comprehensive study of noise in extracellular recordings with glass micropipettes. The purpose of this work was to assess various noise sources that affect extracellular recordings and to create model systems in which novel micropipette neural amplifier designs can be tested. An equivalent circuit of the glass micropipette and the noise model of this circuit, which accurately describe the various noise sources involved in extracellular recordings, have been developed. Measurement schemes using dead brain tissue as well as extracellular recordings from neurons in the inferior colliculus, an auditory brain nucleus of an anesthetized gerbil, were used to characterize noise performance and amplification efficacy of the proposed micropipette neural amplifier. According to our model, the major noise sources which influence the signal to noise ratio are the intrinsic noise of the neural amplifier and the thermal noise from distributed pipette resistance. These two types of noise were calculated and measured and were shown to be the dominating sources of background noise for in vivo experiments. PMID:25133158
The magnetic fields of Uranus and Neptune: Methods and models
Richard Holme; Jeremy Bloxham
1996-01-01
We present new models of the magnetic fields of Uranus and Neptune, based on data provided by the Voyager II magnetic field experiment. We find the simplest models that satisfy the data, and use the observed surface heat flow as a constraint on the magnetic field structure. Our models are similar to the previously described Q3 and O8 models far
Trading Speed and Accuracy by Coding Time: A Coupled-circuit Cortical Model
Standage, Dominic; You, Hongzhi; Wang, Da-Hui; Dorris, Michael C.
2013-01-01
Our actions take place in space and time, but despite the role of time in decision theory and the growing acknowledgement that the encoding of time is crucial to behaviour, few studies have considered the interactions between neural codes for objects in space and for elapsed time during perceptual decisions. The speed-accuracy trade-off (SAT) provides a window into spatiotemporal interactions. Our hypothesis is that temporal coding determines the rate at which spatial evidence is integrated, controlling the SAT by gain modulation. Here, we propose that local cortical circuits are inherently suited to the relevant spatial and temporal coding. In simulations of an interval estimation task, we use a generic local-circuit model to encode time by ‘climbing’ activity, seen in cortex during tasks with a timing requirement. The model is a network of simulated pyramidal cells and inhibitory interneurons, connected by conductance synapses. A simple learning rule enables the network to quickly produce new interval estimates, which show signature characteristics of estimates by experimental subjects. Analysis of network dynamics formally characterizes this generic, local-circuit timing mechanism. In simulations of a perceptual decision task, we couple two such networks. Network function is determined only by spatial selectivity and NMDA receptor conductance strength; all other parameters are identical. To trade speed and accuracy, the timing network simply learns longer or shorter intervals, driving the rate of downstream decision processing by spatially non-selective input, an established form of gain modulation. Like the timing network's interval estimates, decision times show signature characteristics of those by experimental subjects. Overall, we propose, demonstrate and analyse a generic mechanism for timing, a generic mechanism for modulation of decision processing by temporal codes, and we make predictions for experimental verification. PMID:23592967
Trading speed and accuracy by coding time: a coupled-circuit cortical model.
Standage, Dominic; You, Hongzhi; Wang, Da-Hui; Dorris, Michael C
2013-04-01
Our actions take place in space and time, but despite the role of time in decision theory and the growing acknowledgement that the encoding of time is crucial to behaviour, few studies have considered the interactions between neural codes for objects in space and for elapsed time during perceptual decisions. The speed-accuracy trade-off (SAT) provides a window into spatiotemporal interactions. Our hypothesis is that temporal coding determines the rate at which spatial evidence is integrated, controlling the SAT by gain modulation. Here, we propose that local cortical circuits are inherently suited to the relevant spatial and temporal coding. In simulations of an interval estimation task, we use a generic local-circuit model to encode time by 'climbing' activity, seen in cortex during tasks with a timing requirement. The model is a network of simulated pyramidal cells and inhibitory interneurons, connected by conductance synapses. A simple learning rule enables the network to quickly produce new interval estimates, which show signature characteristics of estimates by experimental subjects. Analysis of network dynamics formally characterizes this generic, local-circuit timing mechanism. In simulations of a perceptual decision task, we couple two such networks. Network function is determined only by spatial selectivity and NMDA receptor conductance strength; all other parameters are identical. To trade speed and accuracy, the timing network simply learns longer or shorter intervals, driving the rate of downstream decision processing by spatially non-selective input, an established form of gain modulation. Like the timing network's interval estimates, decision times show signature characteristics of those by experimental subjects. Overall, we propose, demonstrate and analyse a generic mechanism for timing, a generic mechanism for modulation of decision processing by temporal codes, and we make predictions for experimental verification. PMID:23592967
Multiscale Modeling of Solar Coronal Magnetic Reconnection
NASA Technical Reports Server (NTRS)
Antiochos, Spiro K.; Karpen, Judith T.; DeVore, C. Richard
2010-01-01
Magnetic reconnection is widely believed to be the primary process by which the magnetic field releases energy to plasma in the Sun's corona. For example, in the breakout model for the initiation of coronal mass ejections/eruptive flares, reconnection is responsible for the catastrophic destabilizing of magnetic force balance in the corona, leading to explosive energy release. A critical requirement for the reconnection is that it have a "switch-on' nature in that the reconnection stays off until a large store of magnetic free energy has built up, and then it turn on abruptly and stay on until most of this free energy has been released. We discuss the implications of this requirement for reconnection in the context of the breakout model for CMEs/flares. We argue that it imposes stringent constraints on the properties of the flux breaking mechanism, which is expected to operate in the corona on kinetic scales. We present numerical simulations demonstrating how the reconnection and the eruption depend on the effective resistivity, i.e., the effective Lundquist number, and propose a model for incorporating kinetic flux-breaking mechanisms into MHO calculation of CMEs/flares.
A dynamo model of Jupiter's magnetic field
NASA Astrophysics Data System (ADS)
Jones, C. A.
2014-10-01
Jupiter's dynamo is modelled using the anelastic convection-driven dynamo equations. The reference state model is taken from French et al. [2012]. Astrophys. J. Suppl. 202, 5, (11pp), which used density functional theory to compute the equation of state and the electrical conductivity in Jupiter's interior. Jupiter's magnetic field is approximately dipolar, but self-consistent dipolar dynamo models are rather rare when the large variation in density and the effective internal heating are taken into account. Jupiter-like dipolar magnetic fields were found here at small Prandtl number, Pr=0.1. Strong differential rotation in the dynamo region tends to destroy a dominant dipolar component, but when the convection is sufficiently supercritical it generates a strong magnetic field, and the differential rotation in the electrically conducting region is suppressed by the Lorentz force. This allows a magnetic field to develop which is dominated by a steady dipolar component. This suggests that the strong zonal winds seen at Jupiter's surface cannot penetrate significantly into the dynamo region, which starts approximately 7000 km below the surface.
Magnetic field and angular momentum evolution models
NASA Astrophysics Data System (ADS)
Gallet, F.
2013-11-01
The magnetic field in young stellar object is clearly the most important component when one dealing with the angular momentum evolution of solar-like stars. It controls this latter one from the pre-main sequence, during the ``disk locking'' phase where the stars magnetically interact with their surrounding disk, to the main-sequence through powerful stellar winds that remove angular momentum from the stellar surface. We present new models for the rotational evolution of solar-like stars between 1 Myr and 10 Gyr with the aim to reproduce the distributions of rotational periods observed for star forming regions and young open clusters within this age range. Our simulations are produced by a recent model dedicated to the study of the angular momentum evolution of solar-type stars. This model include a new wind braking law based on recent numerical simulations of magnetized stellar winds and a specific dynamo and mass-loss prescription are used to link the angular momentum loss-rate to angular velocity evolution. The model additionally allows for a core/envelope decoupling with an angular momentum transfer between these two regions. Since this former model didn't include any physical star/disk interaction description, two star/disk interaction processes are eventually added to it in order to reproduce the apparent small angular velocities to which the stellar surface is subject during the disk accretion phase. We have developed rotational evolution models for slow, median and fast rotators including two star/disk interaction scenarios that are the magnetospheric ejection and the accretion powered stellar winds processes. The models appear to fail at reproducing the rotational behaviour of solar-type stars except when a more intense magnetic field is used during the disk accretion phase.
Tseng, Jian-Zhi; Wu, Chyan-Chyi; Dai, Ching-Liang
2014-01-01
The modeling and fabrication of a magnetic microsensor based on a magneto-transistor were presented. The magnetic sensor is fabricated by the commercial 0.18 ?m complementary metal oxide semiconductor (CMOS) process without any post-process. The finite element method (FEM) software Sentaurus TCAD is utilized to analyze the electrical properties and carriers motion path of the magneto-transistor. A readout circuit is used to amplify the voltage difference of the bases into the output voltage. Experiments show that the sensitivity of the magnetic sensor is 354 mV/T at the supply current of 4 mA. PMID:24732100
Circuit QED scheme for realization of the Lipkin-Meshkov-Glick model
Jonas Larson
2010-06-17
We propose a scheme in which the Lipkin-Meshkov-Glick model is realized within a circuit QED system. An array of N superconducting qubits interacts with a driven cavity mode. In the dispersive regime, the cavity mode is adiabatically eliminated generating an effective model for the qubits alone. The characteristic long-range order of the Lipkin-Meshkov-Glick model is here mediated by the cavity field. For a closed qubit system, the inherent second order phase transition of the qubits is reflected in the intensity of the output cavity field. In the broken symmetry phase, the many-body ground state is highly entangled. Relaxation of the qubits is analyzed within a mean-field treatment. The second order phase transition is lost, while new bistable regimes occur.
Exact model identification for magnetic suspension system via magnetic field measurement
C. E. Lin; H. L. Jou; Y. R. Sheu
1992-01-01
In magnetic suspension analysis, a simplified model of the current-to-distance relationship is not sufficient to design an optimal controller. Due to the nonlinearity of the magnetic field, an accurate model is difficult to obtain. The authors present an improved model identification method for a magnetic suspension system so as to establish reliable and exact parameters to describe the dynamic motion
Geospace Environmental Modeling (GEM) magnetic reconnection challenge
NASA Astrophysics Data System (ADS)
Birn, J.; Drake, J. F.; Shay, M. A.; Rogers, B. N.; Denton, R. E.; Hesse, M.; Kuznetsova, M.; Ma, Z. W.; Bhattacharjee, A.; Otto, A.; Pritchett, P. L.
2001-03-01
The Geospace Environmental Modeling (GEM) Reconnection Challenge project is presented and the important results, which are presented in a series of companion papers, are summarized. Magnetic reconnection is studied in a simple Harris sheet configuration with a specified set of initial conditions, including a finite amplitude, magnetic island perturbation to trigger the dynamics. The evolution of the system is explored with a broad variety of codes, ranging from fully electromagnetic particle in cell (PIC) codes to conventional resistive magnetohydrodynamic (MHD) codes, and the results are compared. The goal is to identify the essential physics which is required to model collisionless magnetic reconnection. All models that include the Hall effect in the generalized Ohm's law produce essentially indistinguishable rates of reconnection, corresponding to nearly Alfvénic inflow velocities. Thus the rate of reconnection is insensitive to the specific mechanism which breaks the frozen-in condition, whether resistivity, electron inertia, or electron thermal motion. The reconnection rate in the conventional resistive MHD model, in contrast, is dramatically smaller unless a large localized or current dependent resistivity is used. The Hall term brings the dynamics of whistler waves into the system. The quadratic dispersion property of whistlers (higher phase speed at smaller spatial scales) is the key to understanding these results. The implications of these results for trying to model the global dynamics of the magnetosphere are discussed.
Full vector model for magnetization in sediments
NASA Astrophysics Data System (ADS)
Mitra, Ritayan; Tauxe, Lisa
2009-09-01
Sediments provide a continuous record of past geomagnetic field variations. Although it is theoretically possible to get both the direction and intensity of the geomagnetic field from sediment records, the mechanism is not fully understood. Previous workers have postulated that flocculation plays an important role in detrital remanent magnetism (DRM). Flocs are porous, loose and highly fragile aggregates of microscopic clay particles and their behavior in a viscous medium is likely to be different than single particles of magnetic minerals. In order to understand the role of flocculation in sediment magnetization, we carried out a set of redeposition experiments at different field intensities and a quasi-constant field inclination of 45°. We present here a simple numerical model of flocculation, incorporating both magnetic and hydrodynamic torques to explain the experimental data. At small floc sizes DRM acquisition is likely to be non-linear in field strengths comparable to the Earth's, but the sediments may be able to record the directions accurately. With increasing floc sizes sediments may retain a record of the intensity that is linearly related to the applied field or a direction parallel to the applied field, but are unlikely to do both at the same time. Also, the majority of the magnetic particles in the sediments may not be contributing significantly towards the net DRM and any bulk normalizing parameter may be unsuitable if the depositional environment has changed over the depositional period.
NASA Technical Reports Server (NTRS)
Rastaetter, Lutz; Kuznetsova, Maria; Hesse, Michael; Chulaki, Anna; Pulkkinen, Antti; Ridley, Aaron J.; Gombosi, Tamas; Vapirev, Alexander; Raeder, Joachim; Wiltberger, Michael James; Mays, M. L.; Fok, Mei-Ching H.; Weigel, Robert S.; Welling, Daniel T.
2010-01-01
The GEM 2008 modeling challenge efforts are expanding beyond comparing in-situ measurements in the magnetosphere and ionosphere to include the computation of indices to be compared. The Dst index measures the largest deviations of the horizontal magnetic field at 4 equatorial magnetometers from the quiet-time background field and is commonly used to track the strength of the magnetic disturbance of the magnetosphere during storms. Models can calculate a proxy Dst index in various ways, including using the Dessler-Parker Sckopke relation and the energy of the ring current and Biot-Savart integration of electric currents in the magnetosphere. The GEM modeling challenge investigates 4 space weather events and we compare models available at CCMC against each other and the observed values of Ost. Models used include SWMF/BATSRUS, OpenGGCM, LFM, GUMICS (3D magnetosphere MHD models), Fok-RC, CRCM, RAM-SCB (kinetic drift models of the ring current), WINDMI (magnetosphere-ionosphere electric circuit model), and predictions based on an impulse response function (IRF) model and analytic coupling functions with inputs of solar wind data. In addition to the analysis of model-observation comparisons we look at the way Dst is computed in global magnetosphere models. The default value of Dst computed by the SWMF model is for Bz the Earth's center. In addition to this, we present results obtained at different locations on the Earth's surface. We choose equatorial locations at local noon, dusk (18:00 hours), midnight and dawn (6:00 hours). The different virtual observatory locations reveal the variation around the earth-centered Dst value resulting from the distribution of electric currents in the magnetosphere during different phases of a storm.
Hardy, Joseph T., 1978-
2005-01-01
Polymeric self-resettable circuit protection devices have been manufactured for many years with an extrusion based process. These devices add negligible resistance to a circuit at normal power operating conditions but ...
Modeling integrated photovoltaic–electrochemical devices using steady-state equivalent circuits
Winkler, Mark T.; Cox, Casandra R.; Nocera, Daniel G.; Buonassisi, Tonio
2013-01-01
We describe a framework for efficiently coupling the power output of a series-connected string of single-band-gap solar cells to an electrochemical process that produces storable fuels. We identify the fundamental efficiency limitations that arise from using solar cells with a single band gap, an arrangement that describes the use of currently economic solar cell technologies such as Si or CdTe. Steady-state equivalent circuit analysis permits modeling of practical systems. For the water-splitting reaction, modeling defines parameters that enable a solar-to-fuels efficiency exceeding 18% using laboratory GaAs cells and 16% using all earth-abundant components, including commercial Si solar cells and Co- or Ni-based oxygen evolving catalysts. Circuit analysis also provides a predictive tool: given the performance of the separate photovoltaic and electrochemical systems, the behavior of the coupled photovoltaic–electrochemical system can be anticipated. This predictive utility is demonstrated in the case of water oxidation at the surface of a Si solar cell, using a Co–borate catalyst.
A Global Circuit Tool for Modeling Lightning Indirect Effects on Aircraft
NASA Astrophysics Data System (ADS)
Moussa, H.; Abdi, M.; Issac, F.; Prost, D.
The topic of this study is electromagnetic environment and electromagnetic interference (EMI) effects, specifically the modeling of lightning indirect effects on aircraft electrical systems present on embedded and highly exposed equipments, such as nose landing gear (NLG) and nacelles, through a circuit approach. The main goal of the presented work, funded by a French national project, PREFACE, is to propose a simple equivalent electrical circuit to represent a geometrical structure, taking into account mutual, self-inductances, and resistances, which play a fundamental role in the lightning current distribution. Then this model is intended to be coupled to a functional one, describing a power train chain composed of a converter, a shielded power harness, and a motor or a set of resistors used as a load for the converter. The novelty here is to provide a pre-sizing qualitative approach allowing playing on integration in pre-design phases. This tool intends to offer a user-friendly way for replying rapidly to calls for tender, taking into account the lightning constraints.
Model of Protein Kinase B for Cell Survival/Death and its Equivalent Bio Circuit
NASA Astrophysics Data System (ADS)
Jain, Shruti; Naik, Pradeep K.; Bhooshan, Sunil V.
2011-12-01
Signaling pathways have traditionally focused on delineating immediate upstream and down stream interactions, and then organizing these interactions into linear cascades that relay and regulate information from cell surface receptors to cellular effectors such as metabolic enzymes, channels or transcription factors. However, recent analyses of signaling pathways have revealed that cellular signals do not necessarily propagate in a linear fashion. Because of their size and complexity, these networks are often too complicated for the human mind to organize and analyze. AkT (protein kinase B) is a central signaling molecule in the phosphatidylinositol 3-kinase pathway that is frequently activated in human cancer. Here we provide an overview of recent findings, how AkT promotes cell survival by inhibiting apoptosis by phosphorylating and inactivating several targets, including forkhead transcription factors, and caspase-9. The ability of AkT to promote survival was dependent on and proportional to its kinase activity. We have made computational model for AkT, on the basis of that model we have made the truth tables, Boolean equations and than implement the equations using logic circuits and Bio-circuits showing cell survival and death.
Modifications and Modelling of the Fission Surface Power Primary Test Circuit (FSP-PTC)
NASA Technical Reports Server (NTRS)
Garber, Ann E.
2008-01-01
An actively pumped alkali metal flow circuit, designed and fabricated at the NASA Marshall Space Flight Center, underwent a range of tests at MSFC in early 2007. During this period, system transient responses and the performance of the liquid metal pump were evaluated. In May of 2007, the circuit was drained and cleaned to prepare for multiple modifications: the addition of larger upper and lower reservoirs, the installation of an annular linear induction pump (ALIP), and the inclusion of the Single Flow Cell Test Apparatus (SFCTA) in the test section. Performance of the ALIP, provided by Idaho National Laboratory (INL), will be evaluated when testing resumes. The SFCTA, which will be tested simultaneously, will provide data on alkali metal flow behavior through the simulated core channels and assist in the development of a second generation thermal simulator. Additionally, data from the first round of testing has been used to refine the working system model, developed using the Generalized Fluid System Simulation Program (GFSSP). This paper covers the modifications of the FSP-PTC and the updated GFSSP system model.
NASA Technical Reports Server (NTRS)
Guseynov, F. G.; Abbasova, E. M.
1977-01-01
The equivalent representation of brakes and coupling by lumped circuits is investigated. Analytical equations are derived for relating the indices of the transients to the parameters of the equivalent circuits for arbitrary rotor speed. A computer algorithm is given for the calculations.
Kent R. Davey
2007-01-01
The equivalent T circuit of an induction motor is found in every engineering motors book and is becoming increasingly important with the popularity of vector control. The values used in the circuit are used to dictate the necessary gating signals for the pwm inverter. It is the de facto standard bridge between the field analyst and the motor controller. These
Busby, Cathy
Magnetic field gradients from the ST-5 constellation: Improving magnetic and thermal models. Busby (2007), Magnetic field gradients from the ST-5 constellation: Improving magnetic and thermal] Satellite constellations enable the efficient collection of in situ measurements over large volumes of space
Delay fault models and test generation for random logic sequential circuits
Tapan J. Chakraborty; Vishwani D. Agrawal; Michael L. Bushnell
1992-01-01
In this paper, we study delay fault modeta and the corresponding test generation methodology for gen- eral sequential circuits. Our test generation method Is based on transzlion and hazard states of signals and is applicable to any sequential circuit irrespective of its structure, including the circuits where the flipflops can form a scan register. No hold requirement need be bnpased
Celia Lopez-Ongil; Luis Entrena-Arrontes; Teresa Riesgo-Alcaide; Javier Uceda-Antolin
2005-01-01
Functional validation plays an important role in the design cycle of digital integrated circuits. The generation of good test benches is required for checking the complete circuit behaviour. Early location of design errors could highly reduce the development time and cost for these circuits. There are several initiatives for the development of methods that enhance the functional validation of a
A kinematically distorted flux rope model for magnetic clouds
M. J. Owens; V. G. Merkin; P. Riley
2006-01-01
Constant-? force-free magnetic flux rope models have proven to be a valuable first step toward understanding the global context of in situ observations of magnetic clouds. However, cylindrical symmetry is necessarily assumed when using such models, and it is apparent from both observations and modeling that magnetic clouds have highly noncircular cross sections. A number of approaches have been adopted
Investigation of galvanic-coupled intrabody communication using the human body circuit model.
Kibret, Behailu; Seyedi, MirHojjat; Lai, Daniel T H; Faulkner, Micheal
2014-07-01
Intrabody Communication (IBC) is a technique that uses the human body as a transmission medium for electrical signals to connect wearable electronic sensors and devices. Understanding the human body as the transmission medium in IBC paves way for practical implementation of IBC in body sensor networks. In this study, we propose a model for galvanic coupling-type IBC based on a simplified equivalent circuit representation of the human upper arm. We propose a new way to calculate the electrode-skin contact impedance. Based on the model and human experimental results, we discuss important characteristics of galvanic coupling-type IBC, namely, the effect of tissues, anthropometry of subjects, and electrode configuration on signal propagation. We found that the dielectric properties of the muscle primarily characterize the received signal when receiver electrodes are located close to transmitter electrodes. When receiver and transmitter electrodes are far apart, the skin dielectric property affects the received signal. PMID:25014932
Circuit model for the inverse Z-pinch wire array switch.
Waisman, Eduardo Mario; Cuneo, Michael Edward; Harvey-Thompson, A. (The Blackett Laboratory, Imperial College, London SW7 2BW, UK); Lebedev, Sergey V. (The Blackett Laboratory, Imperial College, London SW7 2BW, UK)
2010-06-01
A 0D circuit code is introduced to study the wire array switch concept introduced in. It has been implemented and researched at Imperial College. An exploding wire array, the switch, is in parallel with the load, an imploding wire array. Most of the current flows in the exploding array until it expands and becomes highly resistive. The 0D code contains simple models of Joule energy deposition and plasma expansion for W and Al wires. The purpose of the device is to produce fast Z-pinch implosion, below 100ns on MAGPIE and the Sandia Z machine. Self and mutual inductances are taken into consideration as well as the rocket model for wire ablation. The switch characteristics of the exploding array are prescribed and tuned up to agree with MAGPIE shots. The dependence of the device on the configuration of the arrays is studied and scaling to ZR conditions is explored.
Integration of MHD load models with circuit representations the Z generator.
Jennings, Christopher A.; Ampleford, David J.; Jones, Brent Manley; McBride, Ryan D.; Bailey, James E.; Jones, Michael C.; Gomez, Matthew Robert.; Cuneo, Michael Edward; Nakhleh, Charles; Stygar, William A.; Savage, Mark Edward; Wagoner, Timothy C.; Moore, James K.
2013-03-01
MHD models of imploding loads fielded on the Z accelerator are typically driven by reduced or simplified circuit representations of the generator. The performance of many of the imploding loads is critically dependent on the current and power delivered to them, so may be strongly influenced by the generators response to their implosion. Current losses diagnosed in the transmission lines approaching the load are further known to limit the energy delivery, while exhibiting some load dependence. Through comparing the convolute performance of a wide variety of short pulse Z loads we parameterize a convolute loss resistance applicable between different experiments. We incorporate this, and other current loss terms into a transmission line representation of the Z vacuum section. We then apply this model to study the current delivery to a wide variety of wire array and MagLif style liner loads.
Modeling Skin Effect With Reduced Decoupled R-L Circuits S.Mei and Y. 1.Ismail
Ismail, Yehea
Modeling Skin Effect With Reduced Decoupled R-L Circuits S.Mei and Y. 1.Ismail Electrical-chip conductors such as clock and power distribution networks require accurately modeling skin effect. Furthermore, to incorporate skin effect in the existing generic simulation tools such as SPICE, simple frequency independent
A Versatile HSPICE Electro-Opto-Thermal Circuit Model for Vertical-Cavity Surface-Emitting Lasers
E. Sooudi; M. Soroosh
2006-01-01
In this paper, we propose a circuit model for vertical-cavity surface-emitting laser (VCSEL). The model is based on carrier, photon, and thermal rate equations, with addition of carrier leakage current as the main source for output power rollover phenomenon. Also, presumed distribution of carriers and photons are used in rate equations, and the spatially dependent equations are converted to spatially
Jie Deng; H.-S. Philip Wong
2007-01-01
This paper presents a complete circuit-compatible compact model for single-walled carbon-nanotube field-effect transistors (CNFETs) as an extension to Part 1 of this two-part paper. For the first time, a universal circuit-compatible CNFET model including the practical device nonidealities is implemented with HSPICE. In addition to the nonidealities included in the companion paper, this paper includes the elastic scattering in the
Circuit Modeling of the Electrical Impedance Part III : Disuse Following Bone Fracture
Shiffman, C A
2013-01-01
Multifrequency measurements of the electrical impedance of muscle have been extended to the study of disuse following bone fracture, and analyzed using the 5-element circuit model used earlier in the study of the effects of disease. Eighteen subjects recovering from simple fractures on upper or lower limbs were examined (10 males, 8 females, aged 18-66). Muscles on un-injured contralateral limbs were used as comparison standards, and results are presented in terms of the ratios p(injured)/p(un-injured), where p stands for the circuit parameter r1, r2, r3, 1/c1, or 1/c2. These are strikingly similar to the diseased-to-healthy ratios for patients with neuromuscular disease, reported in part I of this series. In particular r1 is virtually unaffected and the ratios for r2, r3, 1/c1, and 1/c2 can be as large as in serious disease. Furthermore the same pattern of relationships between the parameters is found, suggesting that there is a common underlying mechanism for the impedance changes. Atrophy and fibrosis are examined as candidates for that mechanism, but it is argued that their effects are too small to explain the observed changes. Fundamental considerations aside, the sensitivity, reproducibility and technical simplicity of the technique recommends its use for in-flight assessments of muscles during orbital or interplanetary missions. PMID:23587651
Highly localized Wannier functions for the efficient modeling of photonic crystal circuits
NASA Astrophysics Data System (ADS)
Schillinger, Matthias; Mingaleev, Sergei; Hermann, Daniel; Busch, Kurt
2005-04-01
We present a novel approach for the accurate and efficient modeling of photonic crystal-based integrated optical circuits. Within this approach, the electromagnetic field is expanded into an orthogonal basis of highly localized Wannier functions, which reduces Maxwell's equations to low-rank eigenvalue problems (for defect mode and waveguide dispersion calculations) or to sparse systems of linear equations (for transmission/reflection calculations through/from functional elements). We illustrate the construction of Wannier functions as well as the subsequent determination of defect modes, waveguide dispersion relations, and the characterization of functional elements for realistic two-dimensional photonic crystal structures consisting of square and triangular lattices of air pores in a high-index matrix. Moreover, on the basis of our Wannier function calculations we suggest a novel type of broad-band integrated photonic crystal circuits based on the infiltration of low-index materials such as liquid crystals or polymers into individual pores of these systems. We illustrate this concept through the design of several functional elements such as bends, beam splitters, and waveguide crossings.
Paradoxical function of orexin/hypocretin circuits in a mouse model of Huntington's disease.
Williams, Rhîannan H; Morton, A Jennifer; Burdakov, Denis
2011-06-01
Huntington's disease (HD) is a neurodegenerative disorder involving progressive motor disturbances, cognitive decline, and desynchronized sleep-wake rhythms. Recent studies revealed that restoring normal sleep-wake cycles can improve cognitive function in HD mice, suggesting that some sleep/wake systems remain operational and thus represent potential therapeutic targets for HD. Hypothalamic neurons expressing orexins/hypocretins (orexin neurons) are fundamental orchestrators of arousal in mammals, but it is unclear whether orexin circuits operate normally in HD. Here we analyzed the electrophysiology, histology, and gene expression of orexin circuits in brain slices from R6/2 mice, a transgenic model of HD with a progressive neurological phenotype. We report that in R6/2 mice, the size of an electrically distinct subpopulation of orexin neurons is reduced, as is the number of orexin-immunopositive cells in some hypothalamic regions. R6/2 orexin cells display altered glutamatergic inputs, and have an abnormal circadian profile of activity, despite normal circadian rhythmicity of the suprachiasmatic nucleus (SCN), the "master clock" of the brain. Nevertheless, even at advanced stages of HD, intrinsic firing properties of orexin cells remain normal and suppressible by serotonin, noradrenaline, and glucose. Furthermore, histaminergic neurons (key cells required for the propagation of orexin-induced arousal) also display normal responses to orexin. Together, these data suggest that the orexin system remains functional and modifiable in HD mice, although its circadian activity profile is disrupted and no longer follows that of the SCN. PMID:21324360
A novel ECMO circuit using a SYNERGY circulite pump in a swine model.
Biscotti, Mauer; Singh, Gopal; Downey, Peter; Bacchetta, Matthew
2014-01-01
Extracorporeal membrane oxygenation (ECMO) is used in the management of refractory cardiopulmonary failure. With improvements in technology, patients can be transferred between hospitals, ambulated, and supported for extended periods of time while on ECMO. The SYNERGY CircuLite micropump is a blood pump that has been used as a ventricular assist device for partial support. In this study, we assessed the blood biocompatibility of the SYNERGY blood pump in conjunction with a Quadrox D oxygenator for use in a novel ECMO circuit in a swine model. This clinical design was used to demonstrate early feasibility of this pump system. Four pigs were placed on venovenous ECMO circuit, which consisted of a SYNERGY pump, Quadrox D oxygenator, and Cobe E Pack 3/8 inch tubing. All animals survived the 6 hour ECMO run without catastrophic biocompatibility issues. There was no statistically discernible change from baseline in hematologic parameters, including hemoglobin, plasma-free hemoglobin, total bilirubin, lactate dehydrogenase, D-dimer, fibrinogen, platelets, and P-selectin. We believe that this study serves as a proof of concept and basis for further studies using the SYNERGY pump as a component of ECMO systems. PMID:25000387
Modeling of particles orientation in magnetic field in drying magnetic coatings
Andrei A. Potanin; George Reynolds; Ronald J. Hirko
2000-01-01
Filament coating is studied as a model of magnetic tape manufacturing. Freshly coated filament is driven through a solenoid magnet which orients particles. After drying the coated filament, its squareness is measured as a function of the magnet position, field and the filament speed during coating. Production and model mixes are tested, which differ in dispersion quality and drying rate.
STDP installs in Winner-Take-All circuits an online approximation to hidden Markov model learning.
Kappel, David; Nessler, Bernhard; Maass, Wolfgang
2014-03-01
In order to cross a street without being run over, we need to be able to extract very fast hidden causes of dynamically changing multi-modal sensory stimuli, and to predict their future evolution. We show here that a generic cortical microcircuit motif, pyramidal cells with lateral excitation and inhibition, provides the basis for this difficult but all-important information processing capability. This capability emerges in the presence of noise automatically through effects of STDP on connections between pyramidal cells in Winner-Take-All circuits with lateral excitation. In fact, one can show that these motifs endow cortical microcircuits with functional properties of a hidden Markov model, a generic model for solving such tasks through probabilistic inference. Whereas in engineering applications this model is adapted to specific tasks through offline learning, we show here that a major portion of the functionality of hidden Markov models arises already from online applications of STDP, without any supervision or rewards. We demonstrate the emergent computing capabilities of the model through several computer simulations. The full power of hidden Markov model learning can be attained through reward-gated STDP. This is due to the fact that these mechanisms enable a rejection sampling approximation to theoretically optimal learning. We investigate the possible performance gain that can be achieved with this more accurate learning method for an artificial grammar task. PMID:24675787
STDP Installs in Winner-Take-All Circuits an Online Approximation to Hidden Markov Model Learning
Kappel, David; Nessler, Bernhard; Maass, Wolfgang
2014-01-01
In order to cross a street without being run over, we need to be able to extract very fast hidden causes of dynamically changing multi-modal sensory stimuli, and to predict their future evolution. We show here that a generic cortical microcircuit motif, pyramidal cells with lateral excitation and inhibition, provides the basis for this difficult but all-important information processing capability. This capability emerges in the presence of noise automatically through effects of STDP on connections between pyramidal cells in Winner-Take-All circuits with lateral excitation. In fact, one can show that these motifs endow cortical microcircuits with functional properties of a hidden Markov model, a generic model for solving such tasks through probabilistic inference. Whereas in engineering applications this model is adapted to specific tasks through offline learning, we show here that a major portion of the functionality of hidden Markov models arises already from online applications of STDP, without any supervision or rewards. We demonstrate the emergent computing capabilities of the model through several computer simulations. The full power of hidden Markov model learning can be attained through reward-gated STDP. This is due to the fact that these mechanisms enable a rejection sampling approximation to theoretically optimal learning. We investigate the possible performance gain that can be achieved with this more accurate learning method for an artificial grammar task. PMID:24675787
Dynamical Casimir effect in superconducting microwave circuits
J. R. Johansson; G. Johansson; C. M. Wilson; Franco Nori
2010-01-01
We theoretically investigate the dynamical Casimir effect (DCE) in electrical circuits based on superconducting microfabricated waveguides with tunable boundary conditions. We propose implementing a rapid modulation of the boundary conditions by tuning the applied magnetic flux through superconducting quantum-interference devices that are embedded in the waveguide circuits. We consider two circuits: (i) An open waveguide circuit that corresponds to a
Modeling and Results for Creating Oblique Fields in a Magnetic Flux Leakage Survey Tool
NASA Astrophysics Data System (ADS)
Simek, James C.
2010-02-01
Integrity management programs designed to maintain safe pipeline systems quite often will use survey results from In line inspection (ILI) tools in addition to data from other sources. Commonly referred to a "smart pigs," one of the most widely used types are those based upon the magnetic flux leakage technique, typically used to detect and quantify metal loss zones. The majority of pipelines surveyed to date have used tools with the magnetic field direction axially aligned with the length of the pipeline. In order to enable detection and quantification of extremely narrow metal loss features or certain types of weld zone anomalies, tools employing magnetic circuits directing the magnetic fields around the pipe circumference have been designed and are use in segments where these feature categories are a primary concern. Modeling and laboratory test data of metal loss features will be used to demonstrate the response of extremely narrow metal loss zones as the features are rotated relative to the induced field direction. Based upon these results, the basis for developing a magnetizer capable of creating fields oblique to either pipeline axis will be presented along with the magnetic field profile models of several configurations.
NASA Astrophysics Data System (ADS)
Quan, Tingwei; Li, Jing; Zhou, Hang; Li, Shiwei; Zheng, Ting; Yang, Zhongqing; Luo, Qingming; Gong, Hui; Zeng, Shaoqun
2014-05-01
Mapping the neuronal circuits is essential to understand brain function. Recent technological advancements have made it possible to acquire the brain atlas at single cell resolution. Digital reconstruction of the neural circuits down to this level across the whole brain would significantly facilitate brain studies. However, automatic reconstruction of the dense neural connections from microscopic image still remains a challenge. Here we developed a spherical-coordinate based variational model to reconstruct the shape of the cell body i.e. soma, as one of the procedures for this purpose. When intuitively processing the volumetric images in the spherical coordinate system, the reconstruction of somas with variational model is no longer sensitive to the interference of the complicated neuronal morphology, and could automatically and robustly achieve accurate soma shape regardless of the dense spatial distribution, and diversity in cell size, and morphology. We believe this method would speed drawing the neural circuits and boost brain studies.
Quan, Tingwei; Li, Jing; Zhou, Hang; Li, Shiwei; Zheng, Ting; Yang, Zhongqing; Luo, Qingming; Gong, Hui; Zeng, Shaoqun
2014-01-01
Mapping the neuronal circuits is essential to understand brain function. Recent technological advancements have made it possible to acquire the brain atlas at single cell resolution. Digital reconstruction of the neural circuits down to this level across the whole brain would significantly facilitate brain studies. However, automatic reconstruction of the dense neural connections from microscopic image still remains a challenge. Here we developed a spherical-coordinate based variational model to reconstruct the shape of the cell body i.e. soma, as one of the procedures for this purpose. When intuitively processing the volumetric images in the spherical coordinate system, the reconstruction of somas with variational model is no longer sensitive to the interference of the complicated neuronal morphology, and could automatically and robustly achieve accurate soma shape regardless of the dense spatial distribution, and diversity in cell size, and morphology. We believe this method would speed drawing the neural circuits and boost brain studies. PMID:24829141
Highly integrated 10Gb/s optical sub-assembly and its circuit modeling
NASA Astrophysics Data System (ADS)
Shim, Jongin; Kim, Dongchurl
2006-09-01
A highly integrated 10 Gb/s transmitter optical sub-assembly was fabricated and characterized for XFP transceiver. As a light source, uncooled 1.3 ?m high-speed distributed feedback laser diode (DFB-LD) was fabricated and assembled on AlN sub-mount with a monitoring PD, a matching-resistor, and a bias-Tee with spiral-inductor. A glass sealed metallic low-loss TO-stem with in-line leads was newly presented. We developed a small-signal equivalent circuit model based on measured S-parameters in order to verify RF characteristics of LD and passive components. The eye-diagram of 10 Gb/s NRZ patterns with a PRBS 2 31 -1 was opened clearly without mask violation. At 85°C, -3-dB bandwidth was measured as high as 11 GHz and 75-km transmission was successfully achieved with very low penalty.
NASA Astrophysics Data System (ADS)
Ghosh, Saptarshi; Bhattacharyya, Somak; Kaiprath, Yadunath; Vaibhav Srivastava, Kumar
2014-03-01
In this paper, a bandwidth-enhanced polarization-insensitive ultra-thin metamaterial absorber has been presented. A simple equivalent circuit model has been proposed describing the absorption phenomenon to estimate the frequency of absorption of the proposed microwave absorber. The basic structure consists of concentric rings embedded one inside another to enhance bandwidth by incorporating the scalability property of the metamaterials. Simulation results show that the structure has enhanced bandwidth response with full width at half maxima (FWHM) of 1.15 GHz (9.40-10.55 GHz) with two absorption peaks at 9.66 and 10.26 GHz (96% and 92.5% absorptivity, respectively). The structure is symmetric in design giving rise to polarization-insensitivity and can achieve high absorption for oblique incidence up to 40°. The proposed absorber has been fabricated and measured in anechoic chamber, showing that experimental results agree well with the simulated responses.
Simulation of double layers in a model auroral circuit with nonlinear impedance
NASA Technical Reports Server (NTRS)
Smith, R. A.
1986-01-01
A reduced circuit description of the U-shaped potential structure of a discrete auroral arc, consisting of the flank transmission line plus parallel-electric-field region, is used to provide the boundary condition for one-dimensional simulations of the double-layer evolution. The model yields asymptotic scalings of the double-layer potential, as a function of an anomalous transport coefficient alpha and of the perpendicular length scale l(a) of the arc. The arc potential phi(DL) scales approximately linearly with alpha, and for alpha fixed phi (DL) about l(a) to the z power. Using parameters appropriate to the auroral zone acceleration region, potentials of phi (DPL) 10 kV scale to projected ionospheric dimensions of about 1 km, with power flows of the order of magnitude of substorm dissipation rates.
Simulation of double layers in a model auroral circuit with nonlinear impedance
NASA Astrophysics Data System (ADS)
Smith, R. A.
1986-08-01
A reduced circuit description of the U-shaped potential structure of a discrete auroral arc, consisting of the flank transmission line plus parallel-electric-field region, is used to provide the boundary condition for one-dimensional simulations of the double-layer evolution. The model yields asymptotic scalings of the double-layer potential, as a function of an anomalous transport coefficient alpha and of the perpendicular length scale l(a) of the arc. The arc potential phi(DL) scales approximately linearly with alpha, and for alpha fixed phi (DL) about l(a) to the z power. Using parameters appropriate to the auroral zone acceleration region, potentials of phi (DPL) 10 kV scale to projected ionospheric dimensions of about 1 km, with power flows of the order of magnitude of substorm dissipation rates.
Modeling of the Dielectric Breakdown Under Strong Magnetic Fields
Y. Ben-Ezra; Yu. V. Pershin; Yu. A. Kaplunovsky; I. D. Vagner; P. Wyder
2002-01-01
The formation of breakdown pattern on an insulating surface under the influence of a transverse magnetic field is theoretically investigated. We have generalized the Dielectric Breakdown Model (DBM) and random walker model for the case of external magnetic field. It is shown that fractal dimensionality of the discharge saturates with magnetic fields. It is conjectured that nonlinear current interaction is
NASA Computational Case Study: Modeling Planetary Magnetic and Gravitational Fields
NASA Technical Reports Server (NTRS)
Simpson, David G.; Vinas, Adolfo F.
2014-01-01
In this case study, we model a planet's magnetic and gravitational fields using spherical harmonic functions. As an exercise, we analyze data on the Earth's magnetic field collected by NASA's MAGSAT spacecraft, and use it to derive a simple magnetic field model based on these spherical harmonic functions.
Simulation and design of integrated magnetics for power converters
Yim-Shu Lee; Leung-Pong Wong; David Ki-Wai Cheng
2003-01-01
We introduce a method to use z parameters to model the interface between an electric circuit and a magnetic component. With this model, the electrical equivalent circuit of any complex integrated magnetic component can be developed easily. We describe the simulation and design of integrated magnetics using a z-parameter two-port network model. We use a single-switch regulator with power-factor-correction and
Josep Carmona; Jordi Cortadella; Michael Kishinevsky; Alexander Taubin
2009-01-01
Elasticity in circuits and systems provides tolerance to variations in computation and communication delays. This paper presents a comprehensive overview of elastic circuits for those designers who are mainly familiar with synchronous design. Elasticity can be implemented both synchronously and asynchronously, although it was traditionally more often associated with asynchronous circuits. This paper shows that synchronous and asynchronous elastic circuits
NSDL National Science Digital Library
Toon Van Hoecke
Circuit Builder simulates AC and DC circuits. Circuit Builder can be used in interactive mode (see above) or it can be scripted using JavaScript (see the demo pages). In order for scripting to work, Circuit Builder requires a Java 1.1 capable browser with JavaScript to Java scripting capability.
Magnetic microspheres and tissue model studies for therapeutic applications
NASA Technical Reports Server (NTRS)
Ramachandran, Narayanan; Mazuruk, Konstantin
2004-01-01
The use of magnetic fluids and magnetic particles in combinatorial hyperthermia therapy for cancer treatment is reviewed. The investigation approach adopted for producing thermoregulating particles and tissue model studies for studying particle retention and heating characteristics is discussed.
Model of magnetic compression of relativistic electron beams
T. S. T. Young; P. Spence
1976-01-01
A theoretical model for the magnetic compression of relativistic electron beams is described. Calculations of the beam fraction transmitted through the magnetic mirror are in agreement with several experiments covering a broad parameter range.
Microdosimetric study for nanosecond pulsed electric fields on a cell circuit model with nucleus.
Denzi, Agnese; Merla, Caterina; Camilleri, Paola; Paffi, Alessandra; d'Inzeo, Guglielmo; Apollonio, Francesca; Liberti, Micaela
2013-10-01
Recently, scientific interest in electric pulses, always more intense and shorter and able to induce biological effects on both plasma and nuclear membranes, has greatly increased. Hence, microdosimetric models that include internal organelles like the nucleus have assumed increasing importance. In this work, a circuit model of the cell including the nucleus is proposed, which accounts for the dielectric dispersion of all cell compartments. The setup of the dielectric model of the nucleus is of fundamental importance in determining the transmembrane potential (TMP) induced on the nuclear membrane; here, this is demonstrated by comparing results for three different sets of nuclear dielectric properties present in the literature. The results have been compared, even including or disregarding the dielectric dispersion of the nucleus. The main differences have been found when using pulses shorter than 10 ns. This is due to the fact that the high spectral components of the shortest pulses are differently taken into account by the nuclear membrane transfer functions computed with and without nuclear dielectric dispersion. The shortest pulses are also the most effective in porating the intracellular structures, as confirmed by the time courses of the TMP calculated across the plasma and nuclear membranes. We show how dispersive nucleus models are unavoidable when dealing with pulses shorter than 10 ns because of the large spectral contents arriving above 100 MHz, i.e., over the typical relaxation frequencies of the dipolar mechanism of the molecules constituting the nuclear membrane and the subcellular cell compartments. PMID:23595823
NASA Astrophysics Data System (ADS)
Baumgaertner, A. J.; Lehto, E.; Neely, R. R.; English, J. M.; Zhu, Y.; Lucas, G.; Thayer, J. P.
2013-12-01
Electrical conductivity in the troposphere and stratosphere is an important quantity that determines the distribution of currents in the GEC (Global Electric Circuit), as well as the potential difference between the Earth and the ionosphere. Recently, progress in modeling atmospheric conductivity has been achieved by integrating the conductivity calculation into an AC-GCM (atmospheric chemistry general circulation model), which provides all relevant data. In this study, WACCM (Whole Atmosphere Community Climate Model) is used for conductivity calculations and an analysis of the effects of strong disturbances on the GEC. This includes volcanic eruptions of Pinatubo in 1991 and the super volcano Toba, polar stratospheric clouds, radioactive releases, and the recent strong galactic cosmic ray maximum. In general, there is a decrease in conductivity from enhanced aerosol number densities, resulting from volcanic eruptions or polar stratospheric clouds. Conductivity is increased by additional ionization sources such as radioactive releases, or galactic cosmic ray increases such as during the last solar minimum. The effects of such events on conductivity, column and total resistance, and estimate effects on current distribution and the earth-ionosphere potential difference will be quantified. Percentage change in conductivity at 20 km altitude two months after the Toba volcanic eruption (WACCM model simulation). The enhanced aerosol concentrations lead to a "conductivity hole" between 30°S and 45° N.
Solving the quasi-static field model of the pulse-line accelerator; relationship to a circuit model
Friedman, A
2006-02-01
The Pulse-Line Ion Accelerator (PLIA) is a promising approach to high-gradient acceleration of an ion beam at high line charge density [1, 2, 3, 4, 5, 6]. A recent note by R. J. Briggs [7] suggests that a ''sheath helix'' model of such a system can be solved numerically in the quasi-static limit. Such a model captures the correct macroscopic behavior from ''first principles'' without the need to time-advance the full Maxwell equations on a grid. This note describes numerical methods that may be used to effect such a solution, and their connection to the circuit model that was described in an earlier note by the author [8]. Fine detail of the fields in the vicinity of the helix wires is not obtained by this approach, but for purposes of beam dynamics simulation such detail is not generally needed.
Spin-Based Neuron Model with Domain Wall Magnets as Synapse
Sharad, Mrigank; Panagopoulos, Georgios; Roy, Kaushik
2012-01-01
We present artificial neural network design using spin devices that achieves ultra low voltage operation, low power consumption, high speed, and high integration density. We employ spin torque switched nano-magnets for modelling neuron and domain wall magnets for compact, programmable synapses. The spin based neuron-synapse units operate locally at ultra low supply voltage of 30mV resulting in low computation power. CMOS based inter-neuron communication is employed to realize network-level functionality. We corroborate circuit operation with physics based models developed for the spin devices. Simulation results for character recognition as a benchmark application shows 95% lower power consumption as compared to 45nm CMOS design.
A physical and scalable IV model in BSIM3v3 for analog\\/digital circuit simulation
Yuhua Cheng; Min-Chie Jeng; Zhihong Liu; Jianhui Huang; Mansun Chan; Kai Chen; Ping Keung Ko; Chenming Hu
1997-01-01
A new physical and continuous BSIM (Berkeley Short-Channel IGFET Model) I-V model in BSIM3v3 is presented for circuit simulation. Including the major physical effects in state-of-the art MOS devices, the model describes current characteristics from subthreshold to strong inversion as well as from the linear to the saturation operating regions with a single I-V expression, and guarantees the continuities of
NSDL National Science Digital Library
Integrated Teaching and Learning Program,
Students build a saltwater circuit, which is an electrical circuit that uses saltwater as part of the circuit. Students investigate the conductivity of saltwater, and develop an understanding of how the amount of salt in a solution impacts how much electrical current flows through the circuit. They learn about one real-world application of a saltwater circuit — as a desalination plant tool to test for the removal of salt from ocean water.
NASA Astrophysics Data System (ADS)
Goldaev, Sergey; Khushvaktov, Alisher
2015-01-01
A quantitative analysis of the diffusion model dehumidifying air in the steam circuit of TPP, with a layer of silica gel. Showed that such an approximation, supplemented the experimental value of the coefficient of free diffusion identified by the developed method gives reliable values for the concentration of water vapor absorption over time.
John J. Vincent
1996-01-01
The delineation of analysis techniques for high power radio frequency resonators, used as a fundamental component of particle accelerators, receives little attention in the literature. This dissertation reviews, describes, and develops techniques for resolving a transmission line mode rf resonator into an approximate equivalent circuit. Specifically, it presents a toolbox of techniques used to model and represent rf structures. One
Abelardo Ruíz; Antonio Ramos; San Emeterio; José Luis; Pedro Sanz
The design of efficient ultrasonic transceivers systems for imaging and detection is having a great development at the present time. These systems have demonstrated a great utility in important tasks concerned with the medical and industrial diagnosis. In this paper we present a review and analysis of several Equivalent Circuital Models, proposed for us with the aim of simulating the
NASA Astrophysics Data System (ADS)
Seaman, Aden; Dao, Thanh-Son; McPhee, John
2014-06-01
In this paper, we survey two kinds of mathematics-based battery models intended for use in hybrid and electric vehicle simulation. The first is circuit-based, which is founded upon the electrical behaviour of the battery, and abstracts away the electrochemistry into equivalent electrical components. The second is chemistry-based, which is founded upon the electrochemical equations of the battery chemistry.
Mazumder, Pinaki
of an Equispaced Metallic Nanoparticles (MNPs) Plasmon Wire Kyungjun Song and Pinaki Mazumder, Fellow, IEEE Abstract--Based on the electric dipole moment (EDM) model of free oscillating electrons inside a single of motion of the EDM and EM near-field energy outside the MNP. Finally, equiva- lent circuit of a linearly
Kuwahara, Hiroyuki; Myers, Chris J.; Samoilov, Michael S.
2010-01-01
Uropathogenic Escherichia coli (UPEC) represent the predominant cause of urinary tract infections (UTIs). A key UPEC molecular virulence mechanism is type 1 fimbriae, whose expression is controlled by the orientation of an invertible chromosomal DNA element—the fim switch. Temperature has been shown to act as a major regulator of fim switching behavior and is overall an important indicator as well as functional feature of many urologic diseases, including UPEC host-pathogen interaction dynamics. Given this panoptic physiological role of temperature during UTI progression and notable empirical challenges to its direct in vivo studies, in silico modeling of corresponding biochemical and biophysical mechanisms essential to UPEC pathogenicity may significantly aid our understanding of the underlying disease processes. However, rigorous computational analysis of biological systems, such as fim switch temperature control circuit, has hereto presented a notoriously demanding problem due to both the substantial complexity of the gene regulatory networks involved as well as their often characteristically discrete and stochastic dynamics. To address these issues, we have developed an approach that enables automated multiscale abstraction of biological system descriptions based on reaction kinetics. Implemented as a computational tool, this method has allowed us to efficiently analyze the modular organization and behavior of the E. coli fimbriation switch circuit at different temperature settings, thus facilitating new insights into this mode of UPEC molecular virulence regulation. In particular, our results suggest that, with respect to its role in shutting down fimbriae expression, the primary function of FimB recombinase may be to effect a controlled down-regulation (rather than increase) of the ON-to-OFF fim switching rate via temperature-dependent suppression of competing dynamics mediated by recombinase FimE. Our computational analysis further implies that this down-regulation mechanism could be particularly significant inside the host environment, thus potentially contributing further understanding toward the development of novel therapeutic approaches to UPEC-caused UTIs. PMID:20361050
NASA Technical Reports Server (NTRS)
Mayhew, M. A.
1982-01-01
Long wavelength magnetic anomalies measured by the Pogo series satellites at altitudes 400-700 km over the United States and adjacent areas are inverted to an equivalent layer magnetization model based on an equal area dipole source array at the earth's surface. Minimum source spacing giving a stable solution and a physically meaningful magnetization distribution is 300 km, and a scheme is presented for effectively sampling the distribution on a grid twice as fine. The model expresses lateral variation in the vertical integral of magnetization and is a starting point for models of lateral variation in the form of the magnetization-depth curve in the magnetic crust. The magnetization model contours correlate with large-scale tectonic features, and in the western part of the country, probably reflect Curie isotherm undulations.
NASA Astrophysics Data System (ADS)
Costa Branco, P. J.; Dente, J. A.
2006-04-01
Biomedical engineering applications of ionic polymer metal composites such as motion devices for endoscopy, pumps, valves, catheter navigation mechanisms and spinal pressure sensors make it important to properly model IPMCs for engineering design. In particular, IPMC continuum models and their electric equivalent circuit representation are critical to a more efficient design of IPMC devices. In this paper, we propose a new continuum electromechanical model to understand and predict the electrical/mechanical behavior of the IPMC. An IPMC lumped-parameter circuit is derived from its continuum model to predict the relationship between its voltage and current signals. Although based on previous works of Shahinpoor and Nemat-Nasser, our model was derived on a macroscopic level, the water effects were assumed negligible when compared with the electrical effects of mobile ions for the IPMC motion, the model parameters were clearly identified in their physical meaning, and an equivalent-circuit IPMC model was determined from the established continuum electromechanical model. Experiments are done with two IPMC pieces having different dimensions, which were previously immersed in a sodium solution. The IPMCs are current driven, the transverse displacement and voltage signals being measured for different current values, avoiding the water electrolysis phenomenon. Simulations using the analytic models derived are compared with the experimental results and they are found to predict the electrical and mechanical relations very accurately.
Modeling Magnetic Fields with FEMM 3.1
NASA Astrophysics Data System (ADS)
Gumbart, James
2003-03-01
FEMM (Finite Element Method Magnetics) 3.1, a freeware program, is useful for modeling problems involving magnets, currents and magnetic fields. The applications of such a program involve both education and upper-level research. The program interface is intuitive and robust. As an educational tool, this program is useful because it handles internally the complicated equations needed to be solved when working with magnetism in matter. Since most elementary applications of magnetism involve permanent magnets, this program enables the user to calculate field energies and forces between magnets and magnetic materials, which would otherwise be impossible to obtain. An analysis of a popular physics demonstration, that of a diamagnetic-assisted levitating magnet, will be used to illustrate these concepts in more detail. The sensitivity of the equilibrium points to the spacing of the diamagnetic plates and the position of the upper attracting magnet is well-reproduced in this simulation.
Anomalous transport in discrete arcs and simulation of double layers in a model auroral circuit
NASA Technical Reports Server (NTRS)
Smith, Robert A.
1987-01-01
The evolution and long-time stability of a double layer in a discrete auroral arc requires that the parallel current in the arc, which may be considered uniform at the source, be diverted within the arc to charge the flanks of the U-shaped double-layer potential structure. A simple model is presented in which this current re-distribution is effected by anomalous transport based on electrostatic lower hybrid waves driven by the flank structure itself. This process provides the limiting constraint on the double-layer potential. The flank charging may be represented as that of a nonlinear transmission. A simplified model circuit, in which the transmission line is represented by a nonlinear impedance in parallel with a variable resistor, is incorporated in a 1-d simulation model to give the current density at the DL boundaries. Results are presented for the scaling of the DL potential as a function of the width of the arc and the saturation efficiency of the lower hybrid instability mechanism.
Anomalous transport in discrete arcs and simulation of double layers in a model auroral circuit
NASA Technical Reports Server (NTRS)
Smith, Robert A.
1987-01-01
The evolution and long-time stability of a double layer (DL) in a discrete auroral arc requires that the parallel current in the arc, which may be considered uniform at the source, be diverted within the arc to charge the flanks of the U-shaped double layer potential structure. A simple model is presented in which this current redistribution is effected by anomalous transport based on electrostatic lower hybrid waves driven by the flank structure itself. This process provides the limiting constraint on the double layer potential. The flank charging may be represented as that of a nonlinear transmission line. A simplified model circuit, in which the transmission line is represented by a nonlinear impedance in parallel with a variable resistor, is incorporated in a one-dimensional simulation model to give the current density at the DL boundaries. Results are presented for the scaling of the DL potential as a function of the width of the arc and the saturation efficiency of the lower hybrid instability mechanism.
Force model identification for magnetic suspension systems via magnetic field measurement
Chin E. Lin; Huei L. Jou
1993-01-01
In magnetic suspension analysis, a simplified model of the current-to-distance relationship is not sufficient to design an optimal control. Due to the nonlinearity of the magnetic field, an accurate model, which is a function of the suspended object, suspension distance, core material, and operation conditions, is difficult to obtain. An improved force-model-identification method for magnetic suspension systems establishes reliable parameters
D. Verdyck; R. Belmans
1994-01-01
Contents The frequency inverter current spectrum generates a complex magnetic field in the airgap producing attracting forces having a wide spectrum and leads to audible noise. A mathematical model is presented, predicting vibrations of a permanent magnet machine, based on the modal analysis technique including mechanical damping. Modal forces produced by the magnetic field, are related to the supply currents
Resonant circuit model and design for a high frequency high voltage switched-mode power supply
Gleyson L. Piazza; Ricardo L. Alves; Ivo Barbi
2009-01-01
This paper presents a practical procedure for the determination of high voltage high frequency transformer parameters. Besides, the paper also presents the design of a resonant circuit for the high voltage switched-mode power supply. The non-idealities of the transformers are part of the resonant circuit, were the leakage inductance and winding capacitances of the transformers are associated with the external
Compact Modeling of MOSFET Wearout Mechanisms for Circuit-Reliability Simulation
Xiaojun Li; Jin Qin; Joseph B. Bernstein
2008-01-01
The integration density of state-of-the-art electronic systems is limited by the reliability of the manufactured integrated circuits at a desired circuit density. Design rules, operating voltages, frequencies, and temperatures are precisely chosen to ensure correct product functional operation over its intended lifetime. Thus, in order to obtain the overall performance and functionality bounded by various design and manufacturing constraints, the
Brittle superconducting magnets: an equivilent strain model
Barzi, E.; /Fermilab; Danuso, M.
2010-08-01
To exceed fields of 10 T in accelerator magnets, brittle superconductors like A15 Nb{sub 3}Sn and Nb{sub 3}Al or ceramic High Temperature Superconductors have to be used. For such brittle superconductors it is not their maximum tensile yield stress that limits their structural resistance as much as strain values that provoke deformations in their delicate lattice, which in turn affect their superconducting properties. Work on the sensitivity of Nb{sub 3}Sn cables to strain has been conducted in a number of stress states, including uniaxial and multi-axial, producing usually different results. This has made the need of a constituent design criterion imperative for magnet builders. In conventional structural problems an equivalent stress model is typically used to verify mechanical soundness. In the superconducting community a simple scalar equivalent strain to be used in place of an equivalent stress would be an extremely useful tool. As is well known in fundamental mechanics, there is not one single way to reduce a multiaxial strain state as represented by a 2nd order tensor to a scalar. The conceptual experiment proposed here will help determine the best scalar representation to use in the identification of an equivalent strain model.
Permanent magnet modelling for dynamic applications
A. Benabou; S. Georges; S. Clénet
2008-01-01
Rare earth permanent magnets are very sensitive to temperature as an overheating can lead to a partial or a total demagnetization. It is then necessary to determine the losses in the permanent magnets to design with accuracy an electromagnetic system. In fact, if the permanent magnet experiences a high frequency magnetic field, significant losses appear. In the literature, these losses
Quasilinear transport modelling at low magnetic shear
Citrin, J.; Hogeweij, G. M. D. [FOM Institute DIFFER-Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM, Nieuwegein (Netherlands); Bourdelle, C.; Cottier, P. [CEA, IRFM, F-13108 Saint Paul Lez Durance (France); Escande, D. F. [UMR 6633 CNRS-Universite de Provence, Marseille (France); Guercan, Oe. D. [Laboratoire de Physique des Plasmas, Ecole Polytechnique, CNRS, 91128 Palaiseau Cedex (France); Hatch, D. R.; Jenko, F.; Pueschel, M. J. [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, D-85748 Garching (Germany)
2012-06-15
Accurate and computationally inexpensive transport models are vital for routine and robust predictions of tokamak turbulent transport. To this end, the QuaLiKiz [Bourdelle et al., Phys. Plasmas 14, 112501 (2007)] quasilinear gyrokinetic transport model has been recently developed. QuaLiKiz flux predictions have been validated by non-linear simulations over a wide range in parameter space. However, a discrepancy is found at low magnetic shear, where the quasilinear fluxes are significantly larger than the non-linear predictions. This discrepancy is found to stem from two distinct sources: the turbulence correlation length in the mixing length rule and an increase in the ratio between the quasilinear and non-linear transport weights, correlated with increased non-linear frequency broadening. Significantly closer agreement between the quasilinear and non-linear predictions is achieved through the development of an improved mixing length rule, whose assumptions are validated by non-linear simulations.
Exchange-coupled magnetic films as models for nonuniform soft magnetic materials
I. Bakonyi; E. Tóth-Kádár; P. Horváth; F. I. Tóth
1984-01-01
Magnetization reversal characteristics of exchange-coupled magnetic films obtained by alternately electrodepositing soft Ni-Fe and hard Ni-Co layers on a wire substrate were studied with the help of a critical switching curve tracer. It is considered that the variety of magnetic nehaviour observed in such systems may serve, in some cases, as a simple model for understanding magnetization processes in soft
New method of modeling electronic circuits coupled with 3D electromagnetic finite element models
J. R. Brauer; B. E. MacNeal; L. A. Larkin; V. D. Overbye
1991-01-01
New zero-dimensional or scalar electromagnetic finite elements, that have the time integral of electric scalar potential as their nodal variable are presented. There are three zero-dimensional element types, representing resistors, capacitors, and inductors. These elements can be easily combined with two- or three-dimensional elements, with three components of magnetic vector potential and the time integral of electric scalar potential as
New method of modeling electronic circuits coupled with 3D electromagnetic finite element models
J. R. Brauer; B. E. MacNeal; L. A. Larkin; V. D. Overbye
1991-01-01
New zero-dimensional or scalar electromagnetic finite elements taht have the time integral of electric scalar potential as their nodal variable are presented. There are three zero-dimensional element types, representing resistors, capacitors, and inductors. These elements can be easily combined with two- or three-dimensional elements, with three components of magnetic vector potential and the time integral of electric scalar potential as
Rabi model as a quantum coherent heat engine: From quantum biology to superconducting circuits
Ferdi Altintas; Ali Ü. C. Hardal; Özgür E. Müstecapl?o?lu
2015-02-18
We propose a multilevel quantum heat engine with a working medium described by a generalized Rabi model which consists of a two-level system coupled to a single mode bosonic field. The model is constructed to be a continuum limit of a quantum biological description of light harvesting complexes so that it can amplify quantum coherence by a mechanism which is a quantum analog of classical Huygen's clocks. The engine operates in quantum Otto cycle where the working medium is coupled to classical heat baths in the isochoric processes of the four stroke cycle; while either the coupling strength or the resonance frequency is changed in the adiabatic stages. We found that such an engine can produce work with an efficiency close to Carnot bound when it operates at low temperatures and in the ultrastrong coupling regime. Interplay of quantum coherence and quantum correlations on the engine performance is discussed in terms of second order coherence, quantum mutual information and logarithmic negativity of entanglement. We point out that the proposed quantum Otto engine can be implemented experimentally with the modern circuit quantum electrodynamic systems where flux qubits can be coupled ultrastrongly to superconducting transmission line resonators.
A network flow model for load balancing in circuit-switched multicomputers
NASA Technical Reports Server (NTRS)
Bokhari, Shahid H.
1990-01-01
In multicomputers that utilize circuit switching or wormhole routing, communication overhead depends largely on link contention - the variation due to distance between nodes is negligible. This has a major impact on the load balancing problem. In this case, there are some nodes with excess load (sources) and others with deficit load (sinks) and it is required to find a matching of sources to sinks that avoids contention. The problem is made complex by the hardwired routing on currently available machines: the user can control only which nodes communicate but not how the messages are routed. Network flow models of message flow in the mesh and the hypercube were developed to solve this problem. The crucial property of these models is the correspondence between minimum cost flows and correctly routed messages. To solve a given load balancing problem, a minimum cost flow algorithm is applied to the network. This permits one to determine efficiently a maximum contention free matching of sources to sinks which, in turn, tells one how much of the given imbalance can be eliminated without contention.
Rabi model as a quantum coherent heat engine: From quantum biology to superconducting circuits
NASA Astrophysics Data System (ADS)
Altintas, Ferdi; Hardal, Ali Ü. C.; Müstecapl?o?lu, Özgür E.
2015-02-01
We propose a multilevel quantum heat engine with a working medium described by a generalized Rabi model which consists of a two-level system coupled to a single-mode bosonic field. The model is constructed to be a continuum limit of a quantum biological description of light-harvesting complexes so that it can amplify quantum coherence by a mechanism which is a quantum analog of classical Huygens clocks. The engine operates in a quantum Otto cycle where the working medium is coupled to classical heat baths in the isochoric processes of the four-stroke cycle, while either the coupling strength or the resonance frequency is changed in the adiabatic stages. We found that such an engine can produce work with an efficiency close to the Carnot bound when it operates at low temperatures and in the ultrastrong-coupling regime. The interplay of the effects of quantum coherence and quantum correlations on the engine performance is discussed in terms of second-order coherence, quantum mutual information, and the logarithmic negativity of entanglement. We point out that the proposed quantum Otto engine can be implemented experimentally with modern circuit quantum electrodynamic systems where flux qubits can be coupled ultrastrongly to superconducting transmission-line resonators.
Development of models of magnetic films on a liquid substrate
Taktarov, N.G.
1985-07-01
The authors present new results of simple experiments conducted with films of magnetic surface-active materials (SAM) deposited on the surface of water. They use magnetic liquid with the following composition: kerosene, oleic acid, magnetite. They conclude that in constructing models of magnetic films it is necessary to take account of their mass exchange with volummetric masses.
A STRUCTURAL-MAGNETIC STRAIN MODEL FOR MAGNETOSTRICTIVE TRANSDUCERS
A STRUCTURAL-MAGNETIC STRAIN MODEL FOR MAGNETOSTRICTIVE TRANSDUCERS Marcelo J. Dapino Department magnetic elds. The measured strains are dependent upon both the rotation of moments within the material in response to the eld and the elastic properties of the material. The magnetic behavior is characterized
Baryon magnetic moments in colored quark cluster model
Q. W. Wang; X. G. Lee; S. Z. Hou; Y. J. Song
2006-11-02
Using the colored quark cluster model, we study magnetic moments of the octet baryons. We give the values of the magnetic moments of baryons $p$, $n$, $\\Sigma^+$, $\\Sigma^-$, $\\Xi^0$, and $\\Xi^-$. The results also show that the orbital motion has very significant effects on the spin and magnetic moments of those baryons and the strange component in the proton is very small.
Modeling the properties of ferrogels in uniform magnetic fields
Dean S. Wood; Philip J. Camp
2011-01-01
The properties of ferrogels in homogeneous magnetic fields are studied using a simple microscopic model and Monte Carlo simulations. The main phenomena of interest concern the anisotropy and enhancement of the elastic moduli that result from applying uniform magnetic fields before and after the magnetic grains are locked in to the polymer-gel matrix by cross-linking reactions. The positional organization of
Modeling and simulation of magnetic shape-memory polymer composites
Rumpf, Martin
Composites of small magnetic-shape-memory (MSM) particles em- bedded in a polymer matrix have been proposed magnetic field. For single crystals one can achieve 1 #12;strains of order of magnitude 10% [41, 39, 27, 38Modeling and simulation of magnetic shape-memory polymer composites September 6, 2006 S. Conti1 , M
Electric circuit model for MgO-doped ZrO2–TiO2 ceramic humidity sensor
M. K. Jain; M. C. Bhatnagar; G. L. Sharma
1998-01-01
The MgO-doped ZrO2–TiO2 ceramic pellets were studied for its humidity-sensitive electrical conduction. An equivalent circuit model has been proposed to define the humidity-sensitive electrical properties. This model is in agreement with the experimental findings. The electrical conduction is largely controlled by the intergranular impedance except at very high humidities. The impedance of the pellets showed inductive behavior in high-humidity region.
Electric circuit model for MgO-doped ZrO2-TiO2 ceramic humidity sensor
M. K. Jain; M. C. Bhatnagar; G. L. Sharma
1998-01-01
The MgO-doped ZrO2-TiO2 ceramic pellets were studied for its humidity-sensitive electrical conduction. An equivalent circuit model has been proposed to define the humidity-sensitive electrical properties. This model is in agreement with the experimental findings. The electrical conduction is largely controlled by the intergranular impedance except at very high humidities. The impedance of the pellets showed inductive behavior in high-humidity region.
Elio Consoli; Gianluca Giustolisi; Gaetano Palumbo
2012-01-01
In this paper, an ultra-compact model for nanometer CMOS transistors, suitable for the analysis of digital circuits, is proposed. Starting from modified and more accurate versions of classical compact models, an extremely simple one (nine parameters and piecewise linear $I_{D}$ versus $V_{{\\\\rm DS}}$ relationships in both triode and saturation) is extracted. All the main physical effects that are predominant in
Kim, Young-Do; Lee, Hyo-Chang; Chung, Chin-Wook [Department of Electrical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of)] [Department of Electrical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of)
2013-09-15
Correlations between the external discharge parameters (the driving frequency ? and the chamber dimension R) and plasma characteristics (the skin depth ? and the electron-neutral collision frequency ?{sub m}) are studied using the transformer circuit model [R. B. Piejak et al., Plasma Sources Sci. Technol. 1, 179 (1992)] when the absorbed power is maximized in an inductively coupled plasma. From the analysis of the transformer circuit model, the maximum power transfer conditions, which depend on the external discharge parameters and the internal plasma characteristics, were obtained. It was found that a maximum power transfer occurs when ??0.38R for the discharge condition at which ?{sub m}/??1, while it occurs when ???(2)?(?/?{sub m})R for the discharge condition at which ?{sub m}/??1. The results of this circuit analysis are consistent with the stable last inductive mode region of an inductive-to-capacitive mode transition [Lee and Chung, Phys. Plasmas 13, 063510 (2006)], which was theoretically derived from Maxwell's equations. Our results were also in agreement with the experimental results. From this work, we demonstrate that a simple circuit analysis can be applied to explain complex physical phenomena to a certain extent.
NASA Technical Reports Server (NTRS)
Courey, Karim J.; Asfour, Shihab S.; Onar, Arzu; Bayliss, Jon A.; Ludwig, Larry L.; Wright, Maria C.
2009-01-01
To comply with lead-free legislation, many manufacturers have converted from tin-lead to pure tin finishes of electronic components. However, pure tin finishes have a greater propensity to grow tin whiskers than tin-lead finishes. Since tin whiskers present an electrical short circuit hazard in electronic components, simulations have been developed to quantify the risk of said short circuits occurring. Existing risk simulations make the assumption that when a free tin whisker has bridged two adjacent exposed electrical conductors, the result is an electrical short circuit. This conservative assumption is made because shorting is a random event that had an unknown probability associated with it. Note however that due to contact resistance electrical shorts may not occur at lower voltage levels. In our first article we developed an empirical probability model for tin whisker shorting. In this paper, we develop a more comprehensive empirical model using a refined experiment with a larger sample size, in which we studied the effect of varying voltage on the breakdown of the contact resistance which leads to a short circuit. From the resulting data we estimated the probability distribution of an electrical short, as a function of voltage. In addition, the unexpected polycrystalline structure seen in the focused ion beam (FIB) cross section in the first experiment was confirmed in this experiment using transmission electron microscopy (TEM). The FIB was also used to cross section two card guides to facilitate the measurement of the grain size of each card guide's tin plating to determine its finish.
Hummos, Ali; Franklin, Charles C; Nair, Satish S
2014-12-01
Acetylcholine regulates memory encoding and retrieval by inducing the hippocampus to switch between pattern separation and pattern completion modes. However, both processes can introduce significant variations in the level of network activity and potentially cause a seizure-like spread of excitation. Thus, mechanisms that keep network excitation within certain bounds are necessary to prevent such instability. We developed a biologically realistic computational model of the hippocampus to investigate potential intrinsic mechanisms that might stabilize the network dynamics during encoding and retrieval. The model was developed by matching experimental data, including neuronal behavior, synaptic current dynamics, network spatial connectivity patterns, and short-term synaptic plasticity. Furthermore, it was constrained to perform pattern completion and separation under the effects of acetylcholine. The model was then used to investigate the role of short-term synaptic depression at the recurrent synapses in CA3, and inhibition by basket cell (BC) interneurons and oriens lacunosum-moleculare (OLM) interneurons in stabilizing these processes. Results showed that when CA3 was considered in isolation, inhibition solely by BCs was not sufficient to control instability. However, both inhibition by OLM cells and short-term depression at the recurrent CA3 connections stabilized the network activity. In the larger network including the dentate gyrus, the model suggested that OLM inhibition could control the network during high cholinergic levels while depressing synapses at the recurrent CA3 connections were important during low cholinergic states. Our results demonstrate that short-term plasticity is a critical property of the network that enhances its robustness. Furthermore, simulations suggested that the low and high cholinergic states can each produce runaway excitation through unique mechanisms and different pathologies. Future studies aimed at elucidating the circuit mechanisms of epilepsy could benefit from considering the two modulatory states separately. PMID:24978936
Magnet designation: a model for home healthcare practice.
Browning, Sarah Via; Clark, Rebecca Culver
2015-01-01
Nurses at 1 hospital-affiliated home healthcare agency (HHA) found that being a department of a Magnet-accredited hospital had a significant impact on the culture of their HHA. Important lessons were learned in conjunction with the Magnet designation journey. In this article, the authors describe the history of the Magnet recognition program, the components of the Magnet model, and how these are applicable to nursing practice within HHAs. PMID:25654343
Model System for a One-Dimensional Magnetic Photonic Crystal
S. Linden; M. Decker; M. Wegener
2006-01-01
We fabricate and characterize one-dimensional magnetic (rather than dielectric) photonic crystals for the first time. Our model system is a one-dimensional periodic lattice of gold-wire pairs. Each pair can be viewed as a magnetic coil with two slits and represents a ``magnetic atom.'' Strong coupling between the resulting magnetic-dipole resonance and the Bragg resonance is accomplished by an adjacent dielectric
Peter Klein
1998-01-01
An analytical model for circuit simulation to describe the thermal noise in MOSFErs -for all channel length down to deep submicron is presented. Contrary to the thermal equilibrium assumption, this model includes the influence of the increasing electrical field with downscaling on the electron (hole) equivalent noise temperature. If not taken into account simulation errors of up to one order
Fernandez, Thomas
Double-Strength CAFFEINE: Fast Template-Free Symbolic Modeling of Analog Circuits via Implicit-MICAS Kasteelpark Arenberg 10 B-3001 Leuven, Belgium Abstract CAFFEINE, introduced previously, automatically of analog circuits, CAFFEINE was shown to have the best predictive ability from among 10 regression
K. Suzuki; T. Muranoi; R. Sugita; M. Takeuchi; T. Hariu
1998-01-01
The conventional charged device model (CDM) test methods for large-scale integrated (LSI) circuits have not prescribed the device capacitance; furthermore, the CDM sensitivity has been represented by the withstand voltage. Also, a method for measuring the voltage of small objects such as LSI circuits has not been established. For these reasons, the failure voltages obtained with every kind of tester
NASA Astrophysics Data System (ADS)
Maillard, Pierre
The purpose of this PhD work has been to investigate, model, test, develop and provide hardening techniques and guidelines for the mitigation of single event transients (SETs) in analog mixed-signal (AMS) delay locked loops (DLLs) for radiation-hardened applications. Delay-locked-loops (DLLs) are circuit substructures that are present in complex ASIC and system-on-a-chip designs. These circuits are widely used in on-chip clock distribution systems to reduce clock skew, to reduce jitter noise, and to recover clock signals at regional points within a global clock distribution system. DLLs are critical to the performance of many clock distribution systems, and in turn, the overall performance of the associated integrated system; as such, complex systems often employ multiple DLLs for clock deskew and distribution tasks. In radiation environments such as on-orbit, these critical circuits represent at-risk points of malfunction for large sections of integrated circuits due to vulnerabilities to radiation-generated transients (i.e. single event transients) that fan out across the system. The analysis of single event effects in analog DLLs has shown that each DLL sub-circuit primitive is vulnerable to single event transients. However, we have identified the voltage controlled delay line (VCDL) sub-circuit as the most sensitive to radiation-induced single event effects generating missing clock pulses that increase with the operating frequency of the circuit. This vulnerability increases with multiple instantiation of DLLs as clock distribution nodes throughout an integrated system on a chip. To our knowledge, no complete work in the rad-hard community regarding the hardening of mixed-signal DLLs against single event effects (missing pulses) has been developed. Most of the work present in the literature applies the "brute force" and well-established digital technique of triple modular redundancy (TMR) to the digital subcomponents. We have developed two novel design techniques for the mitigation of DLL missing pulses that are fully implementable in modern CMOS technologies. These techniques offer to the community the choice of hardening using a restoring current technique in the VCDL sub-circuit to inhibit the creation of missing pulse errors, or using a combinational logic error monitoring technique to correct missing pulses after they occur in real time. We have implemented both of these techniques with minimal area and power penalties when compared to TMR. In addition, these hardening techniques have been extrapolated to other clock circuits, such as digital PLLs. The first hardening technique uses a hardened complementary differential pair VCDL to increase the critical charge (Qcrit) necessary for single event transient generation and thus mitigate missing pulses at the source. Our implementation of this technique at 180 nm, 90 nm and 40 nm required less than a 2% area penalty over a non-hardened design. To experimentally validate this technique, hardened VCDLs were designed and fabricated in 180-nm IBM and 40-nm UMC technologies, then tested at the Naval Research Lab in Washington D.C. The second hardening technique, based on combinational logic pulse monitoring, uses an error correction circuit to mitigate the missing pulses as they occur. This ECC technique is implemented via a "peeled" VCDL (i.e. each transistor is split in area but doubled in multiplicity). We have shown the effectiveness of this technique by implementing it in a Xilinx Virtex 5 FPGA. Furthermore, this new ECC technique is independent of technology scaling -- a highly valuable attribute for sub-50 nm design applications. In addition to the formulation, simulation, prototyping, fabrication, and testing of these new hardening solutions, we developed a unique single event analytical model to guide future hardened DLL designs at advanced technology nodes. The model was furthermore generalized to PLL and DLLs. These analytical models were then used to provide a set of equations to the designer for important insight into hardening choices an
Modeling of magnetic and crystal disorder in magnetic oxides
A Mellergård; R. L McGreevy
1997-01-01
Many crystalline materials have interesting properties, both scientifically and technologically, which are related to the detailed magnetic and crystalline structures on a local scale. Recent advances in e.g., GMR (Giant Magnetoresistance) materials, indicate an intimate coupling of the local spin structure to the conduction properties. However, almost all diffraction work on these and related materials concentrate on the long-range crystal
Modeling of magnetic and crystal disorder in magnetic oxides
A. Mellergård; R. L. McGreevy
1998-01-01
Many crystalline materials have interesting properties, both scientifically and technologically, which are related to the detailed magnetic and crystalline structures on a local scale. Recent advances in e.g., GMR (Giant Magnetoresistance) materials, indicate an intimate coupling of the local spin structure to the conduction properties. However, almost all diffraction work on these and related materials concentrate on the long-range crystal
NASA Astrophysics Data System (ADS)
Greenleaf, M.; Li, H.; Zheng, J. P.
2014-12-01
A physical electric circuit model (PECM) was used to identify several electrochemical processes occurring in two commercial Li-ion batteries of different cathode materials (LixFePO4 and LixCoO2) via electrochemical impedance spectroscopy (EIS). Through defining these electrochemical processes in these two cells, it was determined that the charge transfer resistance (or exchange current density) observed via EIS was due to the cathodic exchange current densities in both the LixFePO4 and LixCoO2 full cells. In discussing the ionic diffusion of the examined cells, the anode of one cell and the cathode of the other were primarily responsible for the observed diffusion of the full cells. Lastly, the measured double layer capacitance was determined to be represented in EIS scans by the anodes of both full cells. The diffusion coefficient was calculated using Fick's1st Law estimation, and from this coefficient, the particle size was calculated and evaluated against scanning electron microscopy (SEM).
Speckle measurements of density and temperature profiles in a model gas circuit breaker
NASA Astrophysics Data System (ADS)
Stoller, P. C.; Panousis, E.; Carstensen, J.; Doiron, C. B.; Färber, R.
2015-01-01
Speckle imaging was used to measure the density and temperature distribution in the arc zone of a model high voltage circuit breaker during the high current phase and under conditions simulating those present during current-zero crossings (current-zero-like arc); the arc was stabilized by a transonic, axial flow of synthetic air. A single probe beam was used; thus, accurate reconstruction was only possible for axially symmetric gas flows and arc channels. The displacement of speckles with respect to a reference image was converted to a line-of-sight integrated deflection angle, which was in turn converted into an axially symmetric refractive index distribution using a multistep process that made use of the inverse Radon transform. The Gladstone–Dale relation, which gives the index of refraction as a function of density, was extended to high temperatures by taking into account dissociation and ionization processes. The temperature and density were determined uniquely by assuming that the pressure distribution in the case of cold gas flow (in the absence of an arc) is not modified significantly by the arc. The electric conductivity distribution was calculated from the temperature profile and compared to measurements of the arc voltage and to previous results published in the literature for similar experimental conditions.
The Mauthner-cell circuit of fish as a model system for startle plasticity.
Medan, Violeta; Preuss, Thomas
2014-01-01
The Mauthner-cell (M-cell) system of teleost fish has a long history as an experimental model for addressing a wide range of neurobiological questions. Principles derived from studies on this system have contributed significantly to our understanding at multiple levels, from mechanisms of synaptic transmission and synaptic plasticity to the concepts of a decision neuron that initiates key aspects of the startle behavior. Here we will review recent work that focuses on the neurophysiological and neuropharmacological basis for modifications in the M-cell circuit. After summarizing the main excitatory and inhibitory inputs to the M-cell, we review experiments showing startle response modulation by temperature, social status, and sensory filtering. Although very different in nature, actions of these three sources of modulation converge in the M-cell network. Mechanisms of modulation include altering the excitability of the M-cell itself as well as changes in excitatory and inhibitor drive, highlighting the role of balanced excitation and inhibition for escape decisions. One of the most extensively studied forms of startle plasticity in vertebrates is prepulse inhibition (PPI), a sensorimotor gating phenomenon, which is impaired in several information processing disorders. Finally, we review recent work in the M-cell system which focuses on the cellular mechanisms of PPI and its modulation by serotonin and dopamine. PMID:25106811
1969-01-01
A comprehensive study of lightning protection of over- head distribution circuits has just been completed by a Task Force consisting of eight utility companies and the General Electric Company. Most overhead circuit configurations in use today-or contemplated for use in the future-were studied. This included system voltages from 4-34.5 kV. The use of an overhead ground wire, arrester on the
Device and circuit-level models for carbon nanotube and graphene nanoribbon transistors
Tan, Michael Loong Peng
2011-06-07
industry. Circuit simulation time has been substantially reduced through algorithm improvement and hardware enhancement through high performance computing (HPC) platforms. Given its ‘industry standard’ status for computer aided design and analysis... to Prof. Razali Ismail for the advice and supports. I could not complete my study without the help and discussions with Chin Shin Liang, Desmond Chek, David Chuah and Caston Urayai. Their contributions in quantum physics and circuit simulation...
2011-01-01
Thermally assisted spin transfer torque [TAS + STT] is a new switching approach for magnetic tunnel junction [MTJ] nanopillars that represents the best trade-off between data reliability, power efficiency and density. In this paper, we present a compact model for MTJ switched by this approach, which integrates a number of physical models such as temperature evaluation and STT dynamic switching models. Many experimental parameters are included directly to improve the simulation accuracy. It is programmed in the Verilog-A language and compatible with the standard IC CAD tools, providing an easy parameter configuration interface and allowing high-speed co-simulation of hybrid MTJ/CMOS circuits. PMID:21711868
Reynolds, R.L.; Webring, M.; Grauch, V.J.S.; Tuttle, M.
1990-01-01
Magnetic forward models of the Cement oil field, Oklahoma, were generated to assess the possibility that ferrimagnetic pyrrhotite related to hydrocarbon seepage in the upper 1 km of Permian strata contributes to aeromagnetic anomalies at Cement. Six bodies having different magnetizations were constructed for the magnetic models. Total magnetizations of the bodies of highest pyrrhotite content range from about 3 ?? 10-3 to 56 ?? 10-3 A/m in the present field direction and yield magnetic anomalies (at 120 m altitude) having amplitudes of less than 1 nT to ~6 to 7 nT, respectively. Numerous assumptions were made in the generation of the models, but nevertheless, the results suggest that pyrrhotite, formed via hydrocarbon reactions and within a range of concentrations estimated at Cement, is capable of causing magnetic anomalies. -from Authors
NASA Astrophysics Data System (ADS)
de Almeida, Maria José BM; Salvador, Andreia; Costa, Maria Margarida RR
2014-12-01
Aiming at a deep understanding of some basic concepts of electric circuits in lower secondary schools, this work introduces an analogy between the behavior of children playing in a school yard with a central lake, subject to different conditions, rules, and stimuli, and Drude's free electron model of metals. Using this analogy from the first school contacts with electric phenomena, one can promote students' understanding of concepts such as electric current, the role of generators, potential difference effects, energy transfer, open and closed circuits, resistances, and their combinations in series and parallel. One believes that through this analogy well-known previous misconceptions of young students about electric circuit behaviors can be overcome. Furthermore, students' understanding will enable them to predict, and justify with self-constructed arguments, the behavior of different elementary circuits. The students' predictions can be verified—as a challenge of self-produced understanding schemes—using laboratory experiments. At a preliminary stage, our previsions were confirmed through a pilot study with three classrooms of 9th level Portuguese students.
Chung, Wen Yuan; Gravante, Gianpiero; Al-Leswas, Dhya; Arshad, Ali; Sorge, Roberto; Watson, Chris C; Pollard, Cristina; Metcalfe, Matthew S; Dennison, Ashley R
2013-05-01
We already developed an ex vivo liver-kidney model perfused for 6 h in which the kidney acted as a homeostatic organ to improve the circuit milieu compared to liver alone. In the current study, we extended the multiorgan perfusions to 24 h to evaluate the results and eventual pitfalls manifesting with longer durations. Five livers and kidneys were harvested from female pigs and perfused over 24 h. The extracorporeal circuit included a centrifugal pump, heat exchanger, and oxygenator. The primary end point of the study was the evaluation of the organ functions as gathered from biochemical and acid-base parameters. In the combined liver-kidney circuit, the organs survived and maintained an acceptable homeostasis for different lengths of time, longer for the liver (up to 19-23 h of perfusions) than the kidney (9-13 h of perfusions). Furthermore, glucose and creatinine values decreased significantly over time (from the 5th and 9th hour of perfusion onward). The addition of a kidney to the perfusion circuit improved the biochemical environment by removing excess products from ongoing metabolic processes. The consequence is a more physiological milieu that could improve results from future experimental studies. However, it is likely that long perfusions require some nutritional support over the hours to maintain the organ's vitality and functionality throughout the experiments. PMID:23489088
Demonstrations with an "LCR" Circuit
ERIC Educational Resources Information Center
Kraftmakher, Yaakov
2011-01-01
The "LCR" circuit is an important topic in the course of electricity and magnetism. Papers in this field consider mainly the forced oscillations and resonance. Our aim is to show how to demonstrate the free and self-excited oscillations in an "LCR" circuit. (Contains 4 figures.)
Parallelizing Quantum Circuits
Anne Broadbent; Elham Kashefi
2007-04-13
We present a novel automated technique for parallelizing quantum circuits via forward and backward translation to measurement-based quantum computing patterns and analyze the trade off in terms of depth and space complexity. As a result we distinguish a class of polynomial depth circuits that can be parallelized to logarithmic depth while adding only polynomial many auxiliary qubits. In particular, we provide for the first time a full characterization of patterns with flow of arbitrary depth, based on the notion of influencing paths and a simple rewriting system on the angles of the measurement. Our method leads to insightful knowledge for constructing parallel circuits and as applications, we demonstrate several constant and logarithmic depth circuits. Furthermore, we prove a logarithmic separation in terms of quantum depth between the quantum circuit model and the measurement-based model.
Calculation and Analysis of magnetic gradient tensor components of global magnetic models
NASA Astrophysics Data System (ADS)
Schiffler, Markus; Queitsch, Matthias; Schneider, Michael; Stolz, Ronny; Krech, Wolfram; Meyer, Hans-Georg; Kukowski, Nina
2014-05-01
Magnetic mapping missions like SWARM and its predecessors, e.g. the CHAMP and MAGSAT programs, offer high resolution Earth's magnetic field data. These datasets are usually combined with magnetic observatory and survey data, and subject to harmonic analysis. The derived spherical harmonic coefficients enable magnetic field modelling using a potential series expansion. Recently, new instruments like the JeSSY STAR Full Tensor Magnetic Gradiometry system equipped with very high sensitive sensors can directly measure the magnetic field gradient tensor components. The full understanding of the quality of the measured data requires the extension of magnetic field models to gradient tensor components. In this study, we focus on the extension of the derivation of the magnetic field out of the potential series magnetic field gradient tensor components and apply the new theoretical framework to the International Geomagnetic Reference Field (IGRF) and the High Definition Magnetic Model (HDGM). The gradient tensor component maps for entire Earth's surface produced for the IGRF show low values and smooth variations reflecting the core and mantle contributions whereas those for the HDGM gives a novel tool to unravel crustal structure and deep-situated ore bodies. For example, the Thor Suture and the Sorgenfrei-Thornquist Zone in Europe are delineated by a strong northward gradient. Derived from Eigenvalue decomposition of the magnetic gradient tensor, the scaled magnetic moment, normalized source strength (NSS) and the bearing of the lithospheric sources are presented. The NSS serves as a tool for estimating the lithosphere-asthenosphere boundary as well as the depth of plutons and ore bodies. Furthermore changes in magnetization direction parallel to the mid-ocean ridges can be obtained from the scaled magnetic moment and the normalized source strength discriminates the boundaries between the anomalies of major continental provinces like southern Africa or the Eastern European Craton.
Golubyatnikov, Vladimir P; Bukharina, Tatyana A; Furman, Dagmara P
2015-02-01
Macrochaetes (large bristles) are sensor organs of the Drosophila peripheral nervous system with a function of mechanoreceptors. An adult mechanoreceptor comprises four specialized cells: shaft (trichogen), socket (tormogen), neuron, and glial cell (thecogen). All these cells originate from a single cell, the so-called sensor organ precursor (SOP) cell. Separation of the SOP cell from the encompassing cells of the imaginal disc initiates a multistage process of sensory organ development. A characteristic feature of the SOP cell is the highest amount of the proneural proteins AS-C as compared with the encompassing ectodermal cells. The accumulation of proneural proteins and maintenance of their amount in the SOP cell at a necessary level is provided by the gene network with the achaete-scute gene complex (AS-C) as its key component. The activity of this complex is controlled by the central regulatory circuit (CRC). The CRC comprises the genes hairy, senseless (sens), charlatan (chn), scratch (scrt), daughterless (da), extramacrochaete (emc), and groucho (gro), coding for the transcription factors involved in the system of direct links and feedbacks and implementation of activation-repression relationships between the CRC components. The gene phyllopod (phyl), involved in degradation of the AS-C proteins, is also associated with the CRC functioning. In this paper, we propose a mathematical model for the CRC functioning as a regulator of the amount of proneural AS-C proteins in the SOP cell taking into account their degradation. The modeling has demonstrated that a change in the amount of proneural proteins in the SOP cell is stepwise rather than strictly monotonic. This prediction can be tested experimentally. PMID:25666652
NASA Astrophysics Data System (ADS)
Li, Minghua; Hikihara, Takashi
The redox (Reduction-Oxidation) flow battery is one of the most promising rechargeable batteries due to its ability to average loads and output of power sources. The transient characteristics are well known as the remarkable feature of the battery. Then it can also compensate for a sudden voltage drop. The dynamics are governed by the chemical reactions, fluid flow, and electrical circuit of its structure. This causes the difficulty of the analysis at transient state. This paper discusses the transient behavior of the redox flow battery based on chemical reactions. The concentration change of vanadium ions depends on the chemical reactions and the flow of electrolysis solution. The chemical reaction rate is restricted by the attached external electric circuit. In this paper, a model of the transient behavior is introduced. The validity of the derived model is examined based on experiments for a tested micro-redox flow battery system.
AC magnetic measurements of the ALS Booster Synchrotron Dipole Magnet engineering model
Green, M.I.; Hoyer, E.; Keller, R.; Nelson, D.H.
1988-09-01
We made a minimal set of AC magnetic measurements of the engineering model of the ALS Booster Dipole Magnet as part of the process of qualifying its design for production. Magnetic induction integrals over paths approximating electron-beam trajectories were measured with long curved coils connected to an electronic integrator. Magnetic induction was measured with point coils and an integrator and independently with a Hall-effect Gaussmeter. These quantities, and magnet current, were displayed on a commercial digital storage oscilloscope as parametric functions of time. The displayed waveforms were stored, processed and redisplayed as representations of selected magnet parameters. A waveform representing the magnet's effective-length was created by dividing the integral waveform by the magnetic induction waveform. Waveforms of the transfer functions were produced by dividing both the integral waveform and the magnetic induction waveform by the current waveform. Pairs of matched coils, connected in series opposition, provided differential measurements of field uniformity. Quadrupole and sextupole coefficients were derived from the uniformity data. These magnet parameters were measured at 2 and 10 Hz frequencies. Together with measurements of the magnetic field at selected dc levels, the ac measurements demonstrated that the magnet design met specifications and qualified it for production. 7 refs., 7 figs., 3 tabs.
Qing Zhao; Haining Zhao; Chunrong Ma; Zengwei Li; Shengliang Zhang
2008-01-01
The parameters of permanent magnet synchronous motors consists of flux leakage coefficient, direct-axis synchronous reactance, quadrature-axis synchronous reactance and the ratio of two synchronous reactance. They all can influence the performance of permanent magnet synchronous motor such as pullout torque, pull in torque and starting torque. The calculated accuracy of the parameters above mentioned is a key problem for design
Juan Domingo Baena; J. Bonache; F. Martin; R. M. Sillero; F. Falcone; T. Lopetegi; M. A. G. Laso; J. Garcia-Garcia; I. Gil; M. F. Portillo; M. Sorolla
2005-01-01
In this paper, a new approach for the development of planar metamaterial structures is developed. For this purpose, split-ring resonators (SRRs) and complementary split-ring resonators (CSRRs) coupled to planar transmission lines are investigated. The electromagnetic behavior of these elements, as well as their coupling to the host transmission line, are studied, and analytical equivalent-circuit models are proposed for the isolated
A Symmetrical Model for Microwave Power AlGaAs\\/InGaAs pHEMTs for Switch Circuit Applications
Dong-Ming Lin; Chien-Chang Huang; Yi-Jen Chan
2009-01-01
In this paper, a nonlinear model of microwave power AlGaAs\\/InGaAs pseudomorphic high-electron mobility transistors (pHEMTs) for switch circuit applications is presented. The symmetrical property that allows for the interchange of the drain and the source is emphasized in the characteristic equations, preserving differentiable features to any orders for the entire bias range. Moreover, the subthreshold voltage, the gate leakage current,
Analog electronic neural network circuits
H. P. Graf; Lawrence D. Jackel
1989-01-01
It is argued that the large interconnectivity and the precision required in neural network models present novel opportunities for analog computing. Analog circuits for a wide variety of problems such as pattern matching, optimization, and learning have been proposed and a few have been built. Most of the circuits built so far are relatively small, exploratory designs. Circuits implementing several
Modeling Magnetic Tower Jets in the Laboratory
NASA Astrophysics Data System (ADS)
Ciardi, A.; Lebedev, S. V.; Chittenden, J. P.; Ampleford, D. J.; Bland, S. N.; Bott, B. S.; Rapley, J.
2005-07-01
The twisting of magnetic fields threading an accretion system can lead to the generation on axis of toroidal field loops. As the magnetic pressure increases, the toroidal field inflates, producing a flow. Collimation is due to a background corona, which radially confines this axially growing “magnetic tower”. We investigate the possibility of studying in the laboratory the dynamics, confinement and stability of magnetic tower jets. We present two-dimensional resistive magnetohydrodynamic simulations of radial arrays, which consist of two concentric electrodes connected radially by thin metallic wires. In the laboratory, a radial wire array is driven by a 1 MA current which produces a hot, low density background plasma. During the current discharge a low plasma beta (? < 1), magnetic cavity develops in the background plasma (? is the ratio of thermal to magnetic pressure). This laboratory magnetic tower is driven by the magnetic pressure of the toroidal field and it is surrounded by a shock envelope. On axis, a high density column is produced by the pinch effect. The background plasma has >rsim1, and in the radial direction the magnetic tower is confined mostly by the thermal pressure. In contrast, in the axial direction the pressure rapidly decays and an elongated, well collimated magnetic-jet develops. This is later disrupted by the development of m = 0 instabilities arising in the axial column.
Full circuit calculation for electromagnetic pulse transmission in a high current facility
NASA Astrophysics Data System (ADS)
Zou, Wenkang; Guo, Fan; Chen, Lin; Song, Shengyi; Wang, Meng; Xie, Weiping; Deng, Jianjun
2014-11-01
We describe herein for the first time a full circuit model for electromagnetic pulse transmission in the Primary Test Stand (PTS)—the first TW class pulsed power driver in China. The PTS is designed to generate 8-10 MA current into a z -pinch load in nearly 90 ns rise time for inertial confinement fusion and other high energy density physics research. The PTS facility has four conical magnetic insulation transmission lines, in which electron current loss exists during the establishment of magnetic insulation. At the same time, equivalent resistance of switches and equivalent inductance of pinch changes with time. However, none of these models are included in a commercially developed circuit code so far. Therefore, in order to characterize the electromagnetic transmission process in the PTS, a full circuit model, in which switch resistance, magnetic insulation transmission line current loss and a time-dependent load can be taken into account, was developed. Circuit topology and an equivalent circuit model of the facility were introduced. Pulse transmission calculation of shot 0057 was demonstrated with the corresponding code FAST (full-circuit analysis and simulation tool) by setting controllable parameters the same as in the experiment. Preliminary full circuit simulation results for electromagnetic pulse transmission to the load are presented. Although divergences exist between calculated and experimentally obtained waveforms before the vacuum section, consistency with load current is satisfactory, especially at the rising edge.
NASA Astrophysics Data System (ADS)
Jovanovi?, B.; Brum, R. M.; Torres, L.
2014-04-01
After decades of continued scaling to the beat of Moore's law, it now appears that conventional silicon based devices are approaching their physical limits. In today's deep-submicron nodes, a number of short-channel and quantum effects are emerging that affect the manufacturing process, as well as, the functionality of the microelectronic systems-on-chip. Spintronics devices that exploit both the intrinsic spin of the electron and its associated magnetic moment, in addition to its fundamental electronic charge, are promising solutions to circumvent these scaling threats. Being compatible with the CMOS technology, such devices offer a promising synergy of radiation immunity, infinite endurance, non-volatility, increased density, etc. In this paper, we present a hybrid (magnetic/CMOS) cell that is able to store and process data both electrically and magnetically. The cell is based on perpendicular spin-transfer torque magnetic tunnel junctions (STT-MTJs) and is suitable for use in magnetic random access memories and reprogrammable computing (non-volatile registers, processor cache memories, magnetic field-programmable gate arrays, etc). To demonstrate the potential our hybrid cell, we physically implemented a small hybrid memory block using 45 nm × 45 nm round MTJs for the magnetic part and 28 nm fully depleted silicon on insulator (FD-SOI) technology for the CMOS part. We also report the cells measured performances in terms of area, robustness, read/write speed and energy consumption.
Jovanovi?, B., E-mail: bojan.jovanovic@lirmm.fr, E-mail: lionel.torres@lirmm.fr; Brum, R. M.; Torres, L. [LIRMM—University of Montpellier 2/UMR CNRS 5506, 161 Rue Ada, 34095 Montpellier (France)
2014-04-07
After decades of continued scaling to the beat of Moore's law, it now appears that conventional silicon based devices are approaching their physical limits. In today's deep-submicron nodes, a number of short-channel and quantum effects are emerging that affect the manufacturing process, as well as, the functionality of the microelectronic systems-on-chip. Spintronics devices that exploit both the intrinsic spin of the electron and its associated magnetic moment, in addition to its fundamental electronic charge, are promising solutions to circumvent these scaling threats. Being compatible with the CMOS technology, such devices offer a promising synergy of radiation immunity, infinite endurance, non-volatility, increased density, etc. In this paper, we present a hybrid (magnetic/CMOS) cell that is able to store and process data both electrically and magnetically. The cell is based on perpendicular spin-transfer torque magnetic tunnel junctions (STT-MTJs) and is suitable for use in magnetic random access memories and reprogrammable computing (non-volatile registers, processor cache memories, magnetic field-programmable gate arrays, etc). To demonstrate the potential our hybrid cell, we physically implemented a small hybrid memory block using 45?nm × 45?nm round MTJs for the magnetic part and 28?nm fully depleted silicon on insulator (FD-SOI) technology for the CMOS part. We also report the cells measured performances in terms of area, robustness, read/write speed and energy consumption.
Talà, Adelfia; Delle Side, Domenico; Buccolieri, Giovanni; Tredici, Salvatore Maurizio; Velardi, Luciano; Paladini, Fabio; De Stefano, Mario; Nassisi, Vincenzo; Alifano, Pietro
2014-01-01
In this study, the evidence of electron-dense magnetic inclusions with polyhedral shape in the cytoplasm of Harveyi clade Vibrio strain PS1, a bioluminescent bacterium living in symbiosis with marine organisms, led us to investigate the behavior of this bacterium under exposure to static magnetic fields ranging between 20 and 2000 Gauss. When compared to sham-exposed, the light emission of magnetic field-exposed bacteria growing on solid medium at 18°C ±0.1°C was increased up to two-fold as a function of dose and growth phase. Stimulation of bioluminescence by magnetic field was more pronounced during the post-exponential growth and stationary phase, and was lost when bacteria were grown in the presence of the iron chelator deferoxamine, which caused disassembly of the magnetic inclusions suggesting their involvement in magnetic response. As in luminescent Vibrio spp. bioluminescence is regulated by quorum sensing, possible effects of magnetic field exposure on quorum sensing were investigated. Measurement of mRNA levels by reverse transcriptase real time-PCR demonstrated that luxR regulatory gene and luxCDABE operon coding for luciferase and fatty acid reductase complex were significantly up-regulated in magnetic field-exposed bacteria. In contrast, genes coding for a type III secretion system, whose expression was negatively affected by LuxR, were down-regulated. Up-regulation of luxR paralleled with down-regulation of small RNAs that mediate destabilization of luxR mRNA in quorum sensing signaling pathways. The results of experiments with the well-studied Vibrio campbellii strain BB120 (originally classified as Vibrio harveyi) and derivative mutants unable to synthesize autoinducers suggest that the effects of magnetic fields on quorum sensing may be mediated by AI-2, the interspecies quorum sensing signal molecule. PMID:24960170
Theoretical model for superconductivity in magnetic borocarbides
Amici, A.; Thalmeier, P.
1999-12-01
The interaction between magnetism and superconductivity is investigated within the theory of superconductivity for electrons in magnetic Bloch-states. The authors show that the presence of an incommensurate helical magnetic structure suppresses the superconducting order parameter only slightly, via the reduction of the effective attraction. Consequences for the upper-critical-field curve of HoNi{sub 2}B{sub 2}C and related compounds are discussed.
Synchronization of pacemaker cell firing by weak ELF fields: simulation by a circuit model.
Bruner, L J; Harvey, J R
1998-01-01
Entrainment of output action potentials from repetitively firing pacemaker cells, brought about by regularly spaced excitatory or inhibitory postsynaptic inputs, is a well-known phenomenon. Synchronization of neural firing patterns by extremely low frequency (ELF) external electric fields has also been observed. Whereas current densities of approximately 10 A-m(-2) are required for direct excitation of otherwise quiescent neural tissue, much lower peak current densities (approximately 10[-2] A-m2) have been reported to entrain spontaneously firing molluscan pacemaker cells. We have developed a neural spike generator circuit model that simulates repetitive spike generation by a space clamped patch (area approximately 10[-7] m2) of excitable membrane subjected to depolarizing current. Picoampere (pA) range variation of DC depolarizing current causes a corresponding smooth variation of neural spike frequency, producing a physiologically realistic stimulus-response (S-R) characteristic. When lower pA range 60 Hz AC current is superposed upon the DC depolarizing current, smooth variation of the S-R characteristic is distorted by subharmonic locking of the spike generator at 30, 20, 15, 12, 10 Hz, and higher order subharmonic frequencies. Although the additional superposition of a physiologically realistic level of "white" current noise, covering the bandwidth 4-200 Hz, suffices to obscure higher order subharmonic locking, locking at 30, 20, and 15 Hz is still clearly evident in the presence of noise. Subharmonic locking is observed at an root mean square AC simulated tissue current density of approximately 10(-5) A-m(-2). PMID:9492165
Parsons, W.M.
1988-01-01
A water-cooled vacuum interrupter was designed and tested for use at 25 kA and 10 kV. This device is expected to have a lifetime approximately one order of magnitude greater than commercial dc circuit breakers. Testing showed that, although the device could successfully carry and interrupt 25 kA, interruption reliabililty was only about 95% with a 10 kV recovery voltage. In addition, a structural crack developed in one electrode from either thermal or mechanical stresses or a combination thereof. 11 refs., 4 figs., 1 tab.
H. Taber; D. Schreursl; R. Gillon; E. Vestiel; A. Alabadelahl; C. van Niekerk; B. Nauwelaers
2004-01-01
3 Abstract - On a single wafer and between different wafers, there are variations in device characteristics due to processing non-uniformity and non-reproducibility. In order to capture these variations, we could extract a complete equivalent circuit model for each device. Since this is a time- consuming process, we developed an alternative approach based on an Artificial Neural Network (ANN). This
Twelve-state Potts model in a magnetic field
NASA Astrophysics Data System (ADS)
Kassan-Ogly, F. A.; Filippov, B. N.; Proshkin, A. I.; Zarubin, A. V.
2015-02-01
In this work, we have obtained an exact solution to the one-dimensional modified 12-state Potts model using the Kramers-Wannier transfer matrix with allowance for the exchange interaction between nearest neighbors in an external magnetic field. Analytical expressions have been derived for the heat capacity, magnetization, magnetic susceptibility, magnetic entropy, and magnetocaloric effect as functions of temperature, magnitude and sign of exchange interaction, and the magnitude and direction of the magnetic field. The behavior of all of these parameters has been investigated in detail using numerical methods. The possibility of applying the results obtained to explain the observed magnetic properties of real cubic magnets with a NaCl structure and easy axes oriented along the [110] crystallographic directions has been discussed.
Mysore, Omar
In this paper, we present the first validation of the virtual source (VS) charge-based compact model for standard cell libraries and large-scale digital circuits. With only a modest number of physically meaningful parameters, ...
Specification and verification of gate-level VHDL models of synchronous and asynchronous circuits
NASA Technical Reports Server (NTRS)
Russinoff, David M.
1995-01-01
We present a mathematical definition of hardware description language (HDL) that admits a semantics-preserving translation to a subset of VHDL. Our HDL includes the basic VHDL propagation delay mechanisms and gate-level circuit descriptions. We also develop formal procedures for deriving and verifying concise behavioral specifications of combinational and sequential devices. The HDL and the specification procedures have been formally encoded in the computational logic of Boyer and Moore, which provides a LISP implementation as well as a facility for mechanical proof-checking. As an application, we design, specify, and verify a circuit that achieves asynchronous communication by means of the biphase mark protocol.
Wu, Chia-Shan; Rosado, Carlos J. Ballester; Lu, Hui-Chen
2011-01-01
Sensory inputs triggered by external stimuli are projected into discrete arrays of neuronal modules in the primary sensory cortex. This whisker-to-barrel pathway has gained in popularity as a model system to study the development of cortical circuits and sensory processing because its clear patterns facilitate the identification of genetically modified mice with whisker map deficits and make possible coordinated in vitro and in vivo electrophysiological studies. Numerous whisker map determinants have been identified in the past two decades. In this review, we summarize what have we learned from the detailed studies conducted in various mutant mice with cortical whisker map deficits. We will specifically focus on the anatomical and functional establishment of the somatosensory thalamocortical circuits. PMID:22103423
NASA Astrophysics Data System (ADS)
Fedorovich, Evgeny D.; Kudriavtsev, Igor; Repnikova, Elena A.
2002-01-01
In this paper test apparatus with experimental loop, containing model of primary circuit (lithium, sodium) and secondary circuit (potassium and potassium vapor) of power system for space based on Rankine thermodynamic cycle is presented. The history and multi-years experience with these types of facilities are described for the whole system and its particular components (steam generators, vapor condensers, electromagnetic pumps, devices for potassium cleaning from impurities etc.), instrumentation and methods for measurement. Simulated nuclear heat sources in the form of a high-frequency electric heater and its operation characteristics are examined. Historical insights and lessons learned from work of several technological laboratories over a twenty year period give material and information for adequate evaluation of status in considered area. .
Magnetic and Magnetostrictive Characterization and Modeling of High Strength Steel
NASA Astrophysics Data System (ADS)
Burgy, Christopher Donald
High strength steels exhibit small amounts of magnetostriction, which is a useful property for non-destructive testing amongst other things. This property cannot currently be fully utilized due to a lack of adequate measurements and models. This thesis reports measurements of these material parameters, and derives a model using these parameters to predict magnetization changes due to the application of compressive stresses and magnetic fields. The resulting Preisach model, coupled with COMSOL MultiphysicsRTM finite element modeling, accurately predicts the magnetization change seen in a separate high strength steel sample previously measured by the National Institute of Standards and Technology. Three sets of measurements on low-carbon, low-alloy high strength steel are introduced in this research. The first experiment measured magnetostriction in steel rods under uniaxial compressive stresses and magnetic fields. The second experiment consisted of magnetostriction and magnetization measurements of the same steel rods under the influence of bi-axially applied magnetic fields. The final experiment quantified the small effect that temperature has on magnetization of steels. The experiments demonstrated that the widely used approximation of stress as an "effective field" is inadequate, and that temperatures between -50 and 100 °C cause minimal changes in magnetization. Preisach model parameters for the prediction of the magnetomechanical effect were derived from the experiments. The resulting model accurately predicts experimentally derived major and minor loops for a high strength steel sample, including the bulging and coincident points attributed to compressive stresses. A framework is presented which couples the uniaxial magnetomechanical model with a finite element package, and was used successfully to predict experimentally measured magnetization changes on a complex sample. These results show that a 1-D magnetomechanical model can be applied to predict 3-D magnetization changes due to stress, if adequately coupled.
BANDEY, HELEN L.; BROWN, MARK J.; CERNOSEK, RICHARD W.; HILLMAN, A. ROBERT; MARTIN, STEPHEN J.
1999-09-16
We derive a lumped-element, equivalent-circuit model for the thickness shear mode (TSM) resonator with a viscoelastic film. This modified Butterworth-Van Dyke model includes in the motional branch a series LCR resonator, representing the quartz resonance, and a parallel LCR resonator, representing the film resonance. This model is valid in the vicinity of film resonance, which occurs when the acoustic phase shift across the film is an odd multiple of {pi}/2 radians. This model predicts accurately the frequency changes and damping that arise at resonance and is a reasonable approximation away from resonance. The elements of the model are explicitly related to film properties and can be interpreted in terms of elastic energy storage and viscous power dissipation. The model leads to a simple graphical interpretation of the coupling between the quartz and film resonances and facilitates understanding of the resulting responses. These responses are compared with predictions from the transmission-line and the Sauerbrey models.
Equilibrium Models of Strongly Magnetized Neutron Stars
NASA Astrophysics Data System (ADS)
Hirschmann, Eric W.
2015-01-01
We consider equilibrium configurations of strongly magnetized neutron stars. Within full general relativity and assuming axisymmetry, we construct rotating stars with both poloidal and toroidal fields. Using a self-consistent field approach, we investigate the relative contributions from both magnetic components.
ADVANCED ELECTRIC AND MAGNETIC MATERIAL MODELS FOR FDTD ELECTROMAGNETIC CODES
Poole, B R; Nelson, S D; Langdon, S
2005-05-05
The modeling of dielectric and magnetic materials in the time domain is required for pulse power applications, pulsed induction accelerators, and advanced transmission lines. For example, most induction accelerator modules require the use of magnetic materials to provide adequate Volt-sec during the acceleration pulse. These models require hysteresis and saturation to simulate the saturation wavefront in a multipulse environment. In high voltage transmission line applications such as shock or soliton lines the dielectric is operating in a highly nonlinear regime, which require nonlinear models. Simple 1-D models are developed for fast parameterization of transmission line structures. In the case of nonlinear dielectrics, a simple analytic model describing the permittivity in terms of electric field is used in a 3-D finite difference time domain code (FDTD). In the case of magnetic materials, both rate independent and rate dependent Hodgdon magnetic material models have been implemented into 3-D FDTD codes and 1-D codes.
Macro model for stochastic behavior of resistance distribution of magnetic tunnel junction
NASA Astrophysics Data System (ADS)
Kil, Gyuhyun; Choi, Juntae; Song, Yunheub
2015-04-01
In this work, we fabricated MgO-based magnetic tunnel junction (MTJ) samples to observe behavior of resistance variation, and investigated a stochastic behavior model for MTJ resistance from measured real data. We found the relationship between parallel resistance (RP), anti-parallel resistance (RAP), and TMR from the measurements. The variation of barrier thickness affects not only resistance but also TMR. This means that broad RAP distribution is caused by RP distribution. In addition, RAP distribution can be reduced by increasing temperature and bias voltage. We developed a macro model that can evaluate resistance distribution based on the stochastic behavior of MTJ resistance variation from only tox varied. The amount of resistance variation, which is considered with regard to the circuit performance, can be obtained from ?tox designed by designer. In addition, the impact for operating circumstance such as bias and temperature can be considered by using fit equations.
Modelling and controller design of an isolated diesel engine permanent magnet synchronous generator
Rahman, M.A.; Osheiba, A.M.; Radwan, T.S. [Memorial Univ. of Newfoundland, St. John`s, Newfoundland (Canada). Faculty of Engineering and Applied Science] [Memorial Univ. of Newfoundland, St. John`s, Newfoundland (Canada). Faculty of Engineering and Applied Science; Abdin, E.S. [Menoufiya Univ., Shebin El-Kom (Egypt)] [Menoufiya Univ., Shebin El-Kom (Egypt)
1996-06-01
A method to analyze the steady-state performance of a stand-alone permanent magnet synchronous generator driven by a diesel engine is presented. The proposed method is based on the equivalent d-q circuits and phasor diagram of such a generator in steady-state condition. A fixed capacitor-thyristor controlled reactor scheme is used to regulate the generator terminal voltage by controlling the thyristor ignition angle. Furthermore the overall system dynamics are modelled in terms of state variables and control inputs. Based on a reduced order linearized model, digital optimal state and output feedback controllers are designed by minimizing a quadratic performance index using the dynamic programming technique. The objective of the controller is to maintain the load voltage and frequency constant under varying load conditions. The controller`s effectiveness is assessed by examining the closed-loop system response to sudden load changes.
NSDL National Science Digital Library
Mr. Syracuse
2007-11-03
Here you can learn about the major components of a circuit, as well as how different types of electricity and circuits affect the flow of electrons. electron flow The most basic type of circuit can be formed with a source of electrons and a resistance. This can be done by using two different types of metals and a lemon. The bars of metal are pushed into the lemons, and then are connected to a resistance. The two ...
Wang, Zhuo; Myers, Kalisa G.; Guo, Yumei; Ocampo, Marco A.; Pang, Raina D.; Jakowec, Michael W.; Holschneider, Daniel P.
2013-01-01
Exercise training is widely used for neurorehabilitation of Parkinson’s disease (PD). However, little is known about the functional reorganization of the injured brain after long-term aerobic exercise. We examined the effects of 4 weeks of forced running wheel exercise in a rat model of dopaminergic deafferentation (bilateral, dorsal striatal 6-hydroxydopamine lesions). One week after training, cerebral perfusion was mapped during treadmill walking or at rest using [14C]-iodoantipyrine autoradiography. Regional cerebral blood flow-related tissue radioactivity (rCBF) was analyzed in three-dimensionally reconstructed brains by statistical parametric mapping. In non-exercised rats, lesions resulted in persistent motor deficits. Compared to sham-lesioned rats, lesioned rats showed altered functional brain activation during walking, including: 1. hypoactivation of the striatum and motor cortex; 2. hyperactivation of non-lesioned areas in the basal ganglia-thalamocortical circuit; 3. functional recruitment of the red nucleus, superior colliculus and somatosensory cortex; 4. hyperactivation of the ventrolateral thalamus, cerebellar vermis and deep nuclei, suggesting recruitment of the cerebellar-thalamocortical circuit; 5. hyperactivation of limbic areas (amygdala, hippocampus, ventral striatum, septum, raphe, insula). These findings show remarkable similarities to imaging findings reported in PD patients. Exercise progressively improved motor deficits in lesioned rats, while increasing activation in dorsal striatum and rostral secondary motor cortex, attenuating a hyperemia of the zona incerta and eliciting a functional reorganization of regions participating in the cerebellar-thalamocortical circuit. Both lesions and exercise increased activation in mesolimbic areas (amygdala, hippocampus, ventral striatum, laterodorsal tegmental n., ventral pallidum), as well as in related paralimbic regions (septum, raphe, insula). Exercise, but not lesioning, resulted in decreases in rCBF in the medial prefrontal cortex (cingulate, prelimbic, infralimbic). Our results in this PD rat model uniquely highlight the breadth of functional reorganizations in motor and limbic circuits following lesion and long-term, aerobic exercise, and provide a framework for understanding the neural substrates underlying exercise-based neurorehabilitation. PMID:24278239
Wang, Zhuo; Myers, Kalisa G; Guo, Yumei; Ocampo, Marco A; Pang, Raina D; Jakowec, Michael W; Holschneider, Daniel P
2013-01-01
Exercise training is widely used for neurorehabilitation of Parkinson's disease (PD). However, little is known about the functional reorganization of the injured brain after long-term aerobic exercise. We examined the effects of 4 weeks of forced running wheel exercise in a rat model of dopaminergic deafferentation (bilateral, dorsal striatal 6-hydroxydopamine lesions). One week after training, cerebral perfusion was mapped during treadmill walking or at rest using [(14)C]-iodoantipyrine autoradiography. Regional cerebral blood flow-related tissue radioactivity (rCBF) was analyzed in three-dimensionally reconstructed brains by statistical parametric mapping. In non-exercised rats, lesions resulted in persistent motor deficits. Compared to sham-lesioned rats, lesioned rats showed altered functional brain activation during walking, including: 1. hypoactivation of the striatum and motor cortex; 2. hyperactivation of non-lesioned areas in the basal ganglia-thalamocortical circuit; 3. functional recruitment of the red nucleus, superior colliculus and somatosensory cortex; 4. hyperactivation of the ventrolateral thalamus, cerebellar vermis and deep nuclei, suggesting recruitment of the cerebellar-thalamocortical circuit; 5. hyperactivation of limbic areas (amygdala, hippocampus, ventral striatum, septum, raphe, insula). These findings show remarkable similarities to imaging findings reported in PD patients. Exercise progressively improved motor deficits in lesioned rats, while increasing activation in dorsal striatum and rostral secondary motor cortex, attenuating a hyperemia of the zona incerta and eliciting a functional reorganization of regions participating in the cerebellar-thalamocortical circuit. Both lesions and exercise increased activation in mesolimbic areas (amygdala, hippocampus, ventral striatum, laterodorsal tegmental n., ventral pallidum), as well as in related paralimbic regions (septum, raphe, insula). Exercise, but not lesioning, resulted in decreases in rCBF in the medial prefrontal cortex (cingulate, prelimbic, infralimbic). Our results in this PD rat model uniquely highlight the breadth of functional reorganizations in motor and limbic circuits following lesion and long-term, aerobic exercise, and provide a framework for understanding the neural substrates underlying exercise-based neurorehabilitation. PMID:24278239
A model of interplanetary and coronal magnetic fields
Kenneth H. Schatten; John M. Wilcox; Norman F. Ness
1969-01-01
A model of the large-scale magnetic field structure above the photosphere uses a Green's function solution to Maxwell's equations. Sources for the magnetic field are related to the observed photospheric field and to the field computed at a ‘source’ surface about 0.6 R? above the photosphere. The large-scale interplanetary magnetic field sector pattern is related to the field pattern at
Three-dimensional model of magnetized capacitively coupled plasmas
Shahid Rauf; Jason Kenney; Ken Collins
2009-01-01
A three-dimensional plasma model is used to understand the characteristics of magnetized capacitively coupled plasma discharges. The simulations consider plasmas generated using high frequency (13.5 MHz) and very high frequency (162 MHz) sources, electropositive (Ar) and electronegative (O2) gases, and spatially uniform and nonuniform magnetic fields. Application of a magnetic field parallel to the electrodes is found to enhance the
Non linear permanent magnets modelling with the finite element method
Chavanne, J.; Meunier, G.; Sabonnadiere, J.C
1989-09-01
In order to perform the calculation of permanent magnets with the finite element method, it is necessary to take into account the anisotropic behaviour of hard magnetic materials (Ferrites, NdFeB, SmCo5). In linear cases, the permeability of permanent magnets is a tensor. This one is fully described with the permeabilities parallel and perpendicular to the easy axis of the magnet. In non linear cases, the model uses a texture function which represents the distribution of the local easy axis of the cristallytes of the magnet. This function allows a good representation of the angular dependance of the coercitive field of the magnet. As a result, it is possible to express the magnetic induction B and the tensor as functions of the field and the texture parameter. This model has been implemented in the software FLUX3D where the tensor is used for the Newton-Raphson procedure. 3D demagnetization of a ferrite magnet by a NdFeB magnet is a suitable representative example. They analyze the results obtained for an ideally oriented ferrite magnet and a real one using a measured texture parameter.
NSDL National Science Digital Library
Circuit Sage aims to be "a complete source of information to help you design great circuits fast." Visitors can link on a circuit diagram or categories listed on the sidebar to learn more about various aspects of circuitry. Topics include A/D, Bandgap, Filter, Inductor, and Transceiver Design. The number of resources is a bit mind-boggling, ranging from articles, to software (for purchase), and online tools. Another section offers a "Routine of the Week" to help you mathematically size your circuit.
Field Weakening in Buried Permanent Magnet AC Motor Drives
Brigette Sneyers; Donald W. Novotny; Thomas A. Lipo
1985-01-01
The usual uncoupled d - q model of salient pole synchronous machines (Park's model) may be insufficient for accurate modeling of buried magnet permanent magnet machines. The addition of a nonbilateral coupling between the direct and quadrature axis equivalent circuits is shown to improve the steady-state model greatly. The cross coupling reactance has important implications in improving operation in the
Modeling the efficiency of a magnetic needle for collecting magnetic cells
NASA Astrophysics Data System (ADS)
Butler, Kimberly S.; Adolphi, Natalie L.; Bryant, H. C.; Lovato, Debbie M.; Larson, Richard S.; Flynn, Edward R.
2014-07-01
As new magnetic nanoparticle-based technologies are developed and new target cells are identified, there is a critical need to understand the features important for magnetic isolation of specific cells in fluids, an increasingly important tool in disease research and diagnosis. To investigate magnetic cell collection, cell-sized spherical microparticles, coated with superparamagnetic nanoparticles, were suspended in (1) glycerine-water solutions, chosen to approximate the range of viscosities of bone marrow, and (2) water in which 3, 5, 10 and 100% of the total suspended microspheres are coated with magnetic nanoparticles, to model collection of rare magnetic nanoparticle-coated cells from a mixture of cells in a fluid. The magnetic microspheres were collected on a magnetic needle, and we demonstrate that the collection efficiency versus time can be modeled using a simple, heuristically-derived function, with three physically-significant parameters. The function enables experimentally-obtained collection efficiencies to be scaled to extract the effective drag of the suspending medium. The results of this analysis demonstrate that the effective drag scales linearly with fluid viscosity, as expected. Surprisingly, increasing the number of non-magnetic microspheres in the suspending fluid results increases the collection of magnetic microspheres, corresponding to a decrease in the effective drag of the medium.
Numerical modeling of higher order magnetic moments in UXO discrimination
Sanchez, V.; Yaoguo, L.; Nabighian, M.N.; Wright, D.L.
2008-01-01
The surface magnetic anomaly observed in unexploded ordnance (UXO) clearance is mainly dipolar, and consequently, the dipole is the only magnetic moment regularly recovered in UXO discrimination. The dipole moment contains information about the intensity of magnetization but lacks information about the shape of the target. In contrast, higher order moments, such as quadrupole and octupole, encode asymmetry properties of the magnetization distribution within the buried targets. In order to improve our understanding of magnetization distribution within UXO and non-UXO objects and to show its potential utility in UXO clearance, we present a numerical modeling study of UXO and related metallic objects. The tool for the modeling is a nonlinear integral equation describing magnetization within isolated compact objects of high susceptibility. A solution for magnetization distribution then allows us to compute the magnetic multipole moments of the object, analyze their relationships, and provide a depiction of the anomaly produced by different moments within the object. Our modeling results show the presence of significant higher order moments for more asymmetric objects, and the fields of these higher order moments are well above the noise level of magnetic gradient data. The contribution from higher order moments may provide a practical tool for improved UXO discrimination. ?? 2008 IEEE.
Numerical modeling of magnetic moments for UXO applications
Sanchez, V.; Li, Y.; Nabighian, M.; Wright, D.
2006-01-01
The surface magnetic anomaly observed in UXO clearance is mainly dipolar and, consequently, the dipole is the only magnetic moment regularly recovered in UXO applications. The dipole moment contains information about intensity of magnetization but lacks information about shape. In contrast, higher-order moments, such as quadrupole and octupole, encode asymmetry properties of the magnetization distribution within the buried targets. In order to improve our understanding of magnetization distribution within UXO and non-UXO objects and its potential utility in UXO clearance, we present a 3D numerical modeling study for highly susceptible metallic objects. The basis for the modeling is the solution of a nonlinear integral equation describing magnetization within isolated objects. A solution for magnetization distribution then allows us to compute magnetic moments of the object, analyze their relationships, and provide a depiction of the surface anomaly produced by different moments within the object. Our modeling results show significant high-order moments for more asymmetric objects situated at depths typical of UXO burial, and suggest that the increased relative contribution to magnetic gradient data from these higher-order moments may provide a practical tool for improved UXO discrimination.
CS 294-2 Quantum Circuit Model, Solovay-Kitaev Theorem, BQP Fall 2004 Lecture 4
Vazirani, Umesh
i4 i5 in-1 in 0 1 ``` o1 o2 o3f om-1 om ``` where the box contains a finite number of gates from circuit is as follows: i1 i2 i3 in-1 in ``` o1 o2 o3 on-1 on ``` where the box contains a finite number
Medullary neural circuits related to the nucleus of the solitary tract in the mouse model
Cicchini, Vanessa Johanna
2012-01-01
connectome: a structural description of the human brain.Connectome Project stems from the current lack of knowledge on the specific circuits of the brain andConnectome,” an extensive project seeking to understand the vast neuronal connections composing the human brain (
FDTD modeling of digital signal propagation in 3-D circuits with passive and active loads
Melinda Piket-May; Allen Taflove; John Baron
1994-01-01
Most existing computer-aided circuit design tools are limited when digital clock speeds exceed several hundred MHz. These tools may not deal effectively with the physics of UHF and microwave electromagnetic wave energy transport along metal surfaces such as ground planes or in the air away from metal paths that are common at or above this frequency range. In this paper,