The Derived Equivalent Circuit Model for Magnetized Anisotropic Graphene
Cao, Ying S; Ruehli, Albert E
2015-01-01
Due to the static magnetic field, the conductivity for graphene becomes a dispersive and anisotropic tensor, which complicates most modeling methodologies. In this paper, a novel equivalent circuit model is proposed for graphene with the magnetostatic bias based on the electric field integral equation (EFIE). To characterize the anisotropic property of the biased graphene, the resistive part of the unit circuit is replaced by a resistor in series with current control voltage sources (CCVSs). The CCVSs account for the off-diagonal parts of the surface conductivity tensor for the magnetized graphene. Furthermore, the definitions of the absorption cross section and the scattering cross section are revisited to make them feasible for derived circuit analysis. This proposed method is benchmarked with several numerical examples. This paper also provides a new equivalent circuit model to deal with dispersive and anisotropic materials.
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.
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.
, Fundamentals of Electric Circuits, 5th Edition, 2013, ISBN 978-0-07-338057-1 Supplementary Materials mathematics software such as MATLAB. #12;ECE 321 Fall 2013 Syllabus 2 WSU Learning Outcomes Grading Policy letter grades. Composition of final grade: Your course grade maps to the WSU learning outcomes as: 30
Electrically detected magnetic resonance modeling and fitting: An equivalent circuit approach
Leite, D. M. G.; Batagin-Neto, A.; Nunes-Neto, O.; Gómez, J. A.; Graeff, C. F. O.
2014-01-21
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 Alq{sub 3} 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, Don G. (Livermore, CA); Birx, Dan (Brentwood, CA); Cook, Edward G. (Livermore, CA)
1993-01-01
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.
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…
Study on magnetic circuit of moving magnet linear compressor
NASA Astrophysics Data System (ADS)
Xia, Ming; Chen, Xiaoping; Chen, Jun
2015-05-01
The moving magnet linear compressors are very popular in the tactical miniature stirling cryocoolers. The magnetic circuit of LFC3600 moving magnet linear compressor, manufactured by Kunming institute of Physics, was studied in this study. Three methods of the analysis theory, numerical calculation and experiment study were applied in the analysis process. The calculated formula of magnetic reluctance and magnetomotive force were given in theoretical analysis model. The magnetic flux density and magnetic flux line were analyzed in numerical analysis model. A testing method was designed to test the magnetic flux density of the linear compressor. When the piston of the motor was in the equilibrium position, the value of the magnetic flux density was at the maximum of 0.27T. The results were almost equal to the ones from numerical analysis.
NASA Astrophysics Data System (ADS)
Cui, Xiao-Le; Zhou, Hao-Miao
2015-07-01
The nonlinear thermo-magneto-mechanical magnetostrictive constitutive and the linear thermo-mechanical-electric piezoelectric constitutive are adopted in this paper. The bias magnetic field and ambient temperature are equivalent to a magnetic source and a thermo source, respectively. An equivalent circuit, which contains a magnetic source and a thermo source at the input, for the thermo-magneto-electric coupling effect in magnetoelectric (ME) laminates, is established. The theoretical models of the output voltage and static ME coefficient for ME laminates can be derived from this equivalent circuit model. The predicted static ME coefficient versus temperature curves are in excellent agreement with the experimental data available both qualitatively and quantitatively. It confirms the validity of the proposed model. Then the models are adopted to predict variations in the output voltages and ME coefficients in the laminates under different ambient temperatures, bias magnetic fields, and the volume ratios of magnetostrictive phases. This shows that the output voltage increases with both increasing temperature and increasing volume ratio of magnetostrictive phases; the ME coefficient decreases with increasing temperature; the ME coefficient shows an initial sharp increase and then decreases slowly with the increase in the bias magnetic field, and there is an optimum volume ratio of magnetostrictive phases that maximize the ME coefficient. This paper can not only provide a new idea for the study of the thermo-magneto-electric coupling characteristics of ME laminates, but also provide a theoretical basis for the design and application of ME laminates, operating under different sensors. Project supported by the National Natural Science Foundation of China (Grant Nos. 11172285 and 11472259) and the Natural Science Foundation of Zhejiang Province, China (Grant No. LR13A020002).
Magnetic circuit for hall effect plasma accelerator
NASA Technical Reports Server (NTRS)
Manzella, David H. (Inventor); Jacobson, David T. (Inventor); Jankovsky, Robert S. (Inventor); Hofer, Richard (Inventor); Peterson, Peter (Inventor)
2009-01-01
A Hall effect plasma accelerator includes inner and outer electromagnets, circumferentially surrounding the inner electromagnet along a thruster centerline axis and separated therefrom, inner and outer magnetic conductors, in physical connection with their respective inner and outer electromagnets, with the inner magnetic conductor having a mostly circular shape and the outer magnetic conductor having a mostly annular shape, a discharge chamber, located between the inner and outer magnetic conductors, a magnetically conducting back plate, in magnetic contact with the inner and outer magnetic conductors, and a combined anode electrode/gaseous propellant distributor, located at a bottom portion of the discharge chamber. The inner and outer electromagnets, the inner and outer magnetic conductors and the magnetically conducting back plate form a magnetic circuit that produces a magnetic field that is largely axial and radially symmetric with respect to the thruster centerline.
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.
Local magnetic measurements in magnetic circuits with highly non-uniform electromagnetic fields
NASA Astrophysics Data System (ADS)
Abou-Elyazied Abdallh, Ahmed; Dupré, Luc
2010-04-01
In this paper, local magnetic measurements are carried out in magnetic circuits with non-uniform electromagnetic field patterns, including excitation windings and/or air gaps, as in the case of rotating electrical machines. The effects of sensor choice, sensor noise sensitivity and electromagnetic field inhomogeneity on the accuracy of the identification of the magnetic material properties are investigated. Moreover, the validity of the local magnetic measurements is confirmed by numerical models, based on the finite element method. The paper comprehensively discusses the possibilities, difficulties and limitations of local magnetic measurements in magnetic circuits with non-uniform electromagnetic fields. It is shown that higher accuracy is obtained when the measurements are performed in regions with less stray fields.
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.
Biasing and fast degaussing circuit for magnetic materials
Dress, W.B. Jr.; McNeilly, D.R.
1983-10-04
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 dc current and alternately apply a selectively damped ac 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.
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.
Analog Circuits, Graphical Models,
Reyzin, Lev
AND OR AND G1 I1 G2 I2V [ACCW '06] 4 #12;+ Motivation for The Model To model gene regulatory networks as Boolean networks to represent gene expressions and disruptions Previous gene regulatory network model be manipulated. Only the output is observable. Value Injection Query model [AACW '06] Fully controllable. Only
Design and Modeling of Pulsed Power Accelerators Via Circuit Analysis
Energy Science and Technology Software Center (ESTSC)
1996-12-05
SCREAMER simulates electrical circuits which may contain elements of variable resistance, capacitance and inductance. The user may add variable circuit elements in a simulation by choosing from a library of models or by writing a subroutine describing the element. Transmission lines, magnetically insulated transmission lines (MITLs) and arbitrary voltage and current sources may also be included. Transmission lines are modeled using pi-sections connected in series. Many models of switches and loads are included.
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.
Use of magnetic materials in excimer laser circuits
Vannini, M.; Sze, R.; Hommeau, F.
1987-01-01
The use of saturating magnetic materials in laser excitation discharge systems is presented. Particular attention is given to the most important parameters of magnetic materials and to the analysis of some circuits such as single and multi-stage pulse compressor and pre-pulse isolation systems. 25 refs.,5 figs.
Alignment of the magnetic circuit of the BIPM watt balance
NASA Astrophysics Data System (ADS)
Bielsa, F.; Lu, Y. F.; Lavergne, T.; Kiss, A.; Fang, H.; Stock, M.
2015-12-01
The International Bureau of Weights and Measures (BIPM) is developing a watt balance for the forthcoming redefinition of the kilogram. An improved version of the apparatus, based on a new closed magnetic circuit is now being assembled. The new apparatus will significantly reduce the type B uncertainty due to misalignment of the magnetic circuit as this work demonstrates. We present two techniques recently developed to accurately align the magnetic field of the circuit perpendicular to the direction defined by the local acceleration of gravity. Uncertainty below 30 ?rad was achieved for both techniques which fulfils the requirements for the BIPM watt balance to enable a Planck constant determination at the 1??×??10-8 level.
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.
Lithosphere - Atmosphere - Ionosphere Circuit Model
NASA Astrophysics Data System (ADS)
Kereselidze, Z.; Kachakhidze, N.; Kachakhidze, M.
2012-04-01
There are offered possibilities of original LAI circuit model. The problem concerns of existence of self-generated electromagnetic oscillations in the segment of LAI system, which are results of tectonic stress developing in the focus area of expected earthquake. By this model the main (lowest) frequency of these electromagnetic oscillations frequency spectrum is expressed analytically by following formula: ? = ? c l where ?(?) is the coefficient depended on the frequency and geological characteristics of the medium and approximate to one, c-is the speed of light, and l- the length of the fault in the focus of the expected earthquake. On the base of relevant diagnosis of experimental data, the model gives us possibility to discuss the problem about location, time of occurrence and intensity of an expected earthquake with certain accuracy. In addition to it, considered model does not block the fall-unstable model of earthquake preparing and electromagnetic phenomena accompanied earthquake preparing process. On the contrary, the imagination of physical picture may be simplified in the separate stage of earthquakes preparing. Namely, it is possible to reliably separate series of foreshocks and aftershocks. By this point of view, the certain optimism about using of EM emission as earthquake precursor of full value may be expressed. The base of such optimism is developing of various phenomena connected to VLF emission many times fixed in the surroundings of epicentral area and cosmic space (changing of intensity of electro-telluric current, perturbations of geomagnetic field in forms of irregular pulsations or regular short-period pulsations, perturbations of atmospheric electric field, perturbations of ionosphere critical frequency and TEC, variations of height of lower ionosphere, parameters of ionospheric medium: changing of specific dielectric conductivity and spectrum of MGD waves in it, atmospheric-ionospheric discharging and etc.).
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
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, ...
MODELING AND VISUALIZATION OF SYNTHETIC GENETIC CIRCUITS
Myers, Chris J.
1 MODELING AND VISUALIZATION OF SYNTHETIC GENETIC CIRCUITS Tyler R. Patterson Abstract The iBioSim tool is being developed to facilitate the construction and simulation of synthetic genetic circuits. INTRODUCTION In 1977 a group of researchers managed to modify the DNA of the E. coli bacteria and were able
The Short Circuit Model of Reading.
ERIC Educational Resources Information Center
Lueers, Nancy M.
The name "short circuit" has been given to this model because, in many ways, it adequately describes what happens bioelectrically in the brain. The "short-circuiting" factors include linguistic, sociocultural, attitudinal and motivational, neurological, perceptual, and cognitive factors. Research is reviewed on ways in which each one affects any…
Dong Lai
2012-06-17
The unipolar induction DC circuit model, originally developed by Goldreich & 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 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 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 ultra-compact white dwarf binaries, we find that DC circuit 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, magnetic torque and dissipation are negligible, except possibly during the early T Tauri phase, when the stellar magnetic field is stronger than 10^3G.
Generalized circuit model for coupled plasmonic systems
Benz, Felix; Tserkezis, Christos; Chikkaraddy, Rohit; Sigle, Daniel O; Pukenas, Laurynas; Evans, Stephen D; Aizpurua, Javier; Baumberg, Jeremy J
2015-01-01
We develop an analytic circuit model for coupled plasmonic dimers separated by small gaps that provides a complete account of the optical resonance wavelength. Using a suitable equivalent circuit, it shows how partially conducting links can be treated and provides quantitative agreement with both experiment and full electromagnetic simulations. The model highlights how in the conducting regime, the kinetic inductance of the linkers set the spectral blue-shifts of the coupled plasmon.
Globally Clocked Magnetic Logic Circuits Michael Hall
Chamberlain, Roger
with the Stoner-Wohlfarth switching astroids for the spin valves. The possi- ble magnetic field vectors that can leaves the net field in the left half of the astroid. A high current (D=1) makes the net field positive that each alone will not result in a field outside of the stable region in the astroid. With enable low
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.
MOS integrated circuit fault modeling
NASA Technical Reports Server (NTRS)
Sievers, M.
1985-01-01
Three digital simulation techniques for MOS integrated circuit faults were examined. These techniques embody a hierarchy of complexity bracketing the range of simulation levels. The digital approaches are: transistor-level, connector-switch-attenuator level, and gate level. The advantages and disadvantages are discussed. Failure characteristics are also described.
Stochastic Computational Models for Accurate Reliability Evaluation of Logic Circuits
Han, Jie
Stochastic Computational Models for Accurate Reliability Evaluation of Logic Circuits Hao Chen for the reliability evaluation of logic circuits. Previous accurate analytical approaches, however, have a computational complexity that generally increases exponentially with the size of a circuit, making
Monte Carlo Reliability Model for Microwave Monolithic Integrated Circuits
Rubloff, Gary W.
Monte Carlo Reliability Model for Microwave Monolithic Integrated Circuits Aris Christou Materials Carlo simulation is reported for analog integrated circuits and is based on the modification behavior of MMICs (Monolithic Microwave Integrated Circuits) from individual FET (Field Effect Transistor
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.
EE 202.3 (3L-3P alt weeks) Electric and Magnetic Fields and Circuits
Saskatchewan, University of
EE 202.3 (3L-3P alt weeks) Electric and Magnetic Fields and Circuits Department of Electrical and magnetic fields and circuits beyond the level of the prerequisite courses. Fundamental topics include. Circuit topics include Thevenin's theorem and source conversion, maximum power transfer theorem
Lai Dong
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.
New method of modeling electronic circuits coupled with 3D electromagnetic finite element models
NASA Astrophysics Data System (ADS)
Brauer, J. R.; MacNeal, B. E.; Larkin, L. A.; Overbye, V. D.
1991-09-01
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 nodal variables. Constant current sources are directly modeled by inhomogeneous Neumann excitations, and constant voltage sources are modeled by use of Norton's theorem. By the addition of dependent current and voltage sources, electronic circuits can be modeled. Example finite-element analyses include an R-L circuit, a transistor circuit driving a wire loop modeled with three-dimensional finite elements, and a circuit impedance on the secondary of a saturable three-dimensional transformer model.
Prabhu Gaunkar, N. Bouda, N. R. Y.; Nlebedim, I. C.; Hadimani, R. L.; Mina, M.; Jiles, D. C.; Bulu, I.; Ganesan, K.; Song, Y. Q.
2015-05-07
This work presents investigations and detailed analysis of ringing in a non-resonant pulsed nuclear magnetic resonance (NMR) circuit. Ringing is a commonly observed phenomenon in high power switching circuits. The oscillations described as ringing impede measurements in pulsed NMR systems. It is therefore desirable that those oscillations decay fast. It is often assumed that one of the causes behind ringing is the role of the magnetic core used in the antenna (acting as an inductive load). We will demonstrate that an LRC subcircuit is also set-up due to the inductive load and needs to be considered due to its parasitic effects. It is observed that the parasitics associated with the inductive load become important at certain frequencies. The output response can be related to the response of an under-damped circuit and to the magnetic core material. This research work demonstrates and discusses ways of controlling ringing by considering interrelationships between different contributing factors.
The development of circuit models for ZR.
Harjes, Henry Charles III; Corley, J.
2005-06-01
Summary from only given. The capabilities of the Z accelerator will be significantly enhanced by the Z Refurbishment (ZR) project [McDaniel DH, 2002]. The performance of a single ZR module is currently being characterized in the pre-production engineering evaluation test bed, Z20 [Lehr, JM, 2003]. Z20 is thoroughly diagnosed so that electrical performance of the module can be established. Circuit models of Z20 have been developed and validated in both Screamer [1985] and Bertha [1989] circuit codes. For the purposes of predicting ZR performance, a full ZR circuit model has also been developed in Bertha. The full ZR model (using operating parameters demonstrated on Z20) indicates that the required 26 MA, 100 ns implosion time, output load current pulse will be achieved on ZR. In this paper, the electrical characterization of Z20 and development of the single module circuit models will be discussed in detail. The full ZR model will also be discussed and the results of several system studies conducted to predict ZR performance will be presented.
Circuit Theory for Analysis and Design of Spintronic Integrated Circuits
Manipatruni, Sasikanth; Young, Ian A
2011-01-01
We present a theoretical and a numerical formalism for analysis and design of spintronic integrated circuits (SPINICs). The proposed formalism encompasses a generalized circuit theory for spintronic integrated circuits based on nanomagnetic dynamics and spin transport. We derive the circuit models for vector spin conduction in non-magnetic and magnetic components. We then propose an extension to the modified nodal analysis for the analysis of spin circuits. We demonstrate the applicability of the proposed theory using an example spin logic circuit.
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.
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
He, J.L.; Rote, D.M.; Coffey, H.T.
1991-01-01
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. 15 refs., 7 figs., 1 tab.
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.
Analysis of quench properties of the Q3 magnets with and without open circuit heater elements
Lackey, Sharon; Marriner, John; Pfeffer, Howie; /Fermilab
1995-11-01
The Q3 magnets have 2 independent heater elements that are energized by the quench protection system. One heater element in the Q3 magnet at A4 became an open circuit after the initial cooldown. Recently the second element became an open circuit. The Q3 magnet at A4 is powered in series with a Q3 magnet at B1. The heaters in the magnet at B1 are still intact. The purpose of this study is to determine if the magnet circuit can be operated without undue risk of damage to the magnets. The risk of damage to the magnet at A4 is less of a concern since repairing the heaters is expected to be a major effort in any event. There is one spare Q3 magnet.
Biophysical Models of Neural Computation: Max and Tuning Circuits
Poggio, Tomaso
Biophysical Models of Neural Computation: Max and Tuning Circuits Ulf Knoblich, Jake Bouvrie be implemented by plausible circuits of a few hundred neurons in cortex. We consider two different sets of circuits whose different properties may correspond to the conditions in visual and barrel cortices
Formal Verification of Digital Circuits Using Symbolic Ternary System Models
Bryant, Randal E.
state. This paper presents a formal methodology for verifying synchronous digital circuits using. For example, we can deal with circuits in which nondigital voltages are generated ¤ This research. This occurs frequently when modeling circuits at the switch-level [6], due to (generally transient) short
Equivalent circuit models for ac impedance data analysis
NASA Technical Reports Server (NTRS)
Danford, M. D.
1990-01-01
A least-squares fitting routine has been developed for the analysis of ac impedance data. It has been determined that the checking of the derived equations for a particular circuit with a commercially available electronics circuit program is essential. As a result of the investigation described, three equivalent circuit models were selected for use in the analysis of ac impedance data.
Modeling A circuit switched multiprocessor interconnect
NASA Astrophysics Data System (ADS)
Nussbaum, Daniel; Vuong-Adlerberg, Ingmar; Agarwal, Anant
1989-10-01
This study began as an attempt to understand discrepancies between Patel's classic model of a circuit-switched interconnection network and simulations as part of the MIT ALEWIFE Multiprocessor project. After a careful analysis of Patel's model, we developed a model with fewer approximations that produced results generally closer to detailed simulation. The major source of inaccuracy in Patel's model is the unit-request approximation, which treats a t-cycle request as t l-cycle requests producing significant inaccuracies for networks with many switching levels and for small packet sizes. Our model followed the behavior of the network more closely, explicitly modeling the effects of switch size, network depth, packet size and memory latency, thereby alleviating some inaccuracies in Patel's model. However, despite the slightly lower accuracy of Patel's model, we believe that its simplicity makes it the practical choice for most applications. Thus, our main contribution was to understand the causes of inaccuracies in both models, allowing us to predict the quality of the estimations they yielded. Another research result is validating a complicated simulator using relatively simple models, not a common use for a model. We found that some of the original discrepancies between Patel's model and the simulator were due to hidden inconsistancies between parameters used by the model and those used by the simulator, and that others were due to bugs in the simulator code.
ERIC Educational Resources Information Center
Fay, T. H.; Mead, L.
2006-01-01
The paper discusses an elementary spring model representing the motion of a magnet suspended from the ceiling at one end of a vertical spring which is held directly above a second magnet fixed on the floor. There are two cases depending upon the north-south pole orientation of the two magnets. The attraction or repelling force induced by the…
Yield learning model for integrated circuit package
Balasubramaniam, Gaurishankar
1996-01-01
In a semiconductor industry, packaging of integrated circuit chips, product quality control and rapid problem diagnosis are very critical to economic success. The integrated circuit package makes up a large fraction of the total production cost...
Linear circuit models for on-chip quantum electrodynamics
Alpár Mátyás; Christian Jirauschek; Federico Peretti; Paolo Lugli; György Csaba
2011-06-17
We present equivalent circuits that model the interaction of microwave resonators and quantum systems. The circuit models are derived from a general interaction Hamiltonian. Quantitative agreement between the simulated resonator transmission frequency, qubit Lamb shift and experimental data will be shown. We demonstrate that simple circuit models, using only linear passive elements, can be very useful in understanding systems where a small quantum system is coupled to a classical microwave apparatus.
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.
Numerical model for atomtronic circuit analysis
NASA Astrophysics Data System (ADS)
Chow, Weng W.; Straatsma, Cameron J. E.; Anderson, Dana Z.
2015-07-01
A model for studying atomtronic devices and circuits based on finite-temperature Bose-condensed gases is presented. The approach involves numerically solving equations of motion for atomic populations and coherences, derived using the Bose-Hubbard Hamiltonian and the Heisenberg picture. The resulting cluster expansion is truncated at a level giving balance between physics rigor and numerical demand mitigation. This approach allows parametric studies involving time scales that cover both the rapid population dynamics relevant to nonequilibrium state evolution, as well as the much longer time durations typical for reaching steady-state device operation. The model is demonstrated by studying the evolution of a Bose-condensed gas in the presence of atom injection and extraction in a double-well potential. In this configuration phase locking between condensates in each well of the potential is readily observed, and its influence on the evolution of the system is studied.
Low depth quantum circuits for Ising models
Iblisdir, S.; Cirio, M.; Boada, O.; Brennen, G.K.
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.
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.
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.
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.
High Resolution PV Power Modeling for Distribution Circuit Analysis
Norris, B. L.; Dise, J. H.
2013-09-01
NREL has contracted with Clean Power Research to provide 1-minute simulation datasets of PV systems located at three high penetration distribution feeders in the service territory of Southern California Edison (SCE): Porterville, Palmdale, and Fontana, California. The resulting PV simulations will be used to separately model the electrical circuits to determine the impacts of PV on circuit operations.
ERIC Educational Resources Information Center
Gabel, Dorothy; And Others
1992-01-01
Chemistry can be described on three levels: sensory, molecular, and symbolic. Proposes a particle approach to teaching chemistry that uses magnets to aid students construct molecular models and solve particle problems. Includes examples of Johnstone's model of chemistry phenomena, a problem worksheet, and a student concept mastery sheet. (MDH)
On the Circuit Model of Global Adiabatic Search Algorithm
NASA Astrophysics Data System (ADS)
Sun, Jie; Lu, Songfeng; Liu, Fang; Zhang, Zhigang; Zhou, Qing
2015-10-01
Local adiabatic search has been implemented on the quantum circuit model, and the time steps necessary to guarantee the approximation precision are of the same order as the time complexity of the algorithm. However, it is easy to verify that this conclusion doesn't hold for global adiabatic search. But we know that adiabatic computing is equivalent to the circuit model of quantum computation. Therefore, there must exist a corresponding quantum circuit that correctly implements such a global adiabatic search. In this Letter, we show that this indeed could be true.
A Closed Loop Prosthetic Hand as a Model Sensorimotor Circuit
Saunders, Ian; Vijayakumar, Sethu
2009-01-01
and finger positions. In order to understand this model sensorimotor circuit we first tackle two sub-problems: (Q1) Do we integrate artificial sensory feedback (vibrotactile) with our other modalities (vision, proprioception) in a statistically optimal manner...
Resistive companion battery modeling for electric circuit simulations , R. Dougalb
Resistive companion battery modeling for electric circuit simulations B. Wua , R. Dougalb , R be achieved based on RC models. In this study, the construction of RC battery models is investigated. A general battery model and a nickel±metal hydride cell model have been built. Simulations of RC battery
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
Introductory Invited Paper Electronic circuit reliability modeling
Shapira, Yoram
by the reliability of the manufactured product at a desired circuit density. Design rules, operating voltage of the product. Thus, in order to determine the ultimate performance for a given set of design constraints aggressive design rules has been a reduction in the weight of a single failure mechanism. Hence in modern
Altarawneh, Moaz M; Mielke, Charles H
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.
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
Combination of Thermal Subsystems Modelled by Rapid Circuit Transformation
Y. C. Gerstenmaier; W. Kiffe; G. Wachutka
2008-01-07
This paper will deal with the modeling-problem of combining thermal subsystems (e.g. a semiconductor module or package with a cooling radiator) making use of reduced models. The subsystem models consist of a set of Foster-type thermal equivalent circuits, which are only behavioral models. A fast al-gorithm is presented for transforming the Foster-type circuits in Cauer-circuits which have physical behavior and therefore allow for the construction of the thermal model of the complete system. Then the set of Cauer-circuits for the complete system is transformed back into Foster-circuits to give a simple mathematical representation and applicability. The transfor-mation algorithms are derived in concise form by use of recur-sive relations. The method is exemplified by modeling and measurements on a single chip IGBT package mounted on a closed water cooled radiator. The thermal impedance of the complete system is constructed from the impedances of the sub-systems, IGBT-package and radiator, and also the impedance of the package can be inferred from the measured impedance of the complete system.
NASA Astrophysics Data System (ADS)
Wiegelmann, Thomas; Petrie, Gordon J. D.; Riley, Pete
2015-07-01
Coronal magnetic field models use photospheric field measurements as boundary condition to model the solar corona. We review in this paper the most common model assumptions, starting from MHD-models, magnetohydrostatics, force-free and finally potential field models. Each model in this list is somewhat less complex than the previous one and makes more restrictive assumptions by neglecting physical effects. The magnetohydrostatic approach neglects time-dependent phenomena and plasma flows, the force-free approach neglects additionally the gradient of the plasma pressure and the gravity force. This leads to the assumption of a vanishing Lorentz force and electric currents are parallel (or anti-parallel) to the magnetic field lines. Finally, the potential field approach neglects also these currents. We outline the main assumptions, benefits and limitations of these models both from a theoretical (how realistic are the models?) and a practical viewpoint (which computer resources to we need?). Finally we address the important problem of noisy and inconsistent photospheric boundary conditions and the possibility of using chromospheric and coronal observations to improve the models.
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.
A Markovian, Variation-Aware Circuit-Level Aging Model
Cotofana, Sorin
A Markovian, Variation-Aware Circuit-Level Aging Model Nicoleta Cucu Laurenciu, and Sorin Dan.CucuLaurenciu, S.D.Cotofana}@tudelft.nl Abstract--Accurate age modeling, and fast, yet robust relia- bility sign at design-time appropriate guardbands selection and effective aging mitigation/compensation techniques
External circuit integration with electromagnetic particle in cell modeling of plasma focus devices
Seng, Y. S.; Lee, P.; Rawat, R. S.
2015-03-15
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.
BATTERIES AND BULBS, BOOK 2, CIRCUITS AND MAGNETS.
ERIC Educational Resources Information Center
1966
THIS TRIAL EDITION OF A TEACHER'S GUIDE, BOOK TWO IN A SERIES OF FOUR, IS INTENDED TO PROVIDE RESOURCE MATERIAL FOR AN INTRODUCTORY STUDY OF ELECTRICITY AND MAGNETISM. IT IS SUITABLE FOR ADAPTION TO VARIOUS LEVELS FROM GRADES 2-10. USED IN CONJUNCTION WITH THE OTHER VOLUMES, IT PROVIDES MATERIAL FOR A PROGRAM OF FROM 5 TO 40 WEEKS, DEPENDING ON…
Modeling of single-event upset in bipolar integrated circuits
NASA Technical Reports Server (NTRS)
Zoutendyk, J. A.
1983-01-01
The results of work done on the quantitative characterization of single-event upset (SEU) in bipolar random-access memories (RAMs) have been obtained through computer simulation of SEU in RAM cells that contain circuit models for bipolar transistors. The models include current generators that emulate the charge collected from ion tracks. The computer simulation results are compared with test data obtained from a RAM in a bipolar microprocessor chip. This methodology is applicable to other bipolar integrated circuit constructions in addition to RAM cells.
Thermoacoustic resonance effect and circuit modelling of biological tissue
NASA Astrophysics Data System (ADS)
Gao, Fei; Zheng, Yuanjin; Feng, Xiaohua; Ohl, Claus-Dieter
2013-02-01
In this letter, thermoacoustic resonance effect is predicted from theoretical analysis with series resistor-inductor-capacitor resonance circuit model and then observed experimentally using muscle tissue illuminated by multi-pulse microwave source. Through model fitting, the circuit parameters are extracted to characterize quantitatively the resonant response of the tissue. Coherent demodulation is applied to obtain the enhanced signal-to-noise ratio and spatial information by treating tissue as a communication channel. This physical phenomenon shows significantly higher sensitivity than conventional single microwave pulse induced thermoacoustic effect, enabling the potential design of low-power thermoacoustic imaging device for portable and on-site diagnosis.
Statistical modeling of SRAM yield performance and circuit variability
NASA Astrophysics Data System (ADS)
Cheng, Qi; Chen, Yijian
2015-03-01
In this paper, we develop statistical models to investigate SRAM yield performance and circuit variability in the presence of self-aligned multiple patterning (SAMP) process. It is assumed that SRAM fins are fabricated by a positivetone (spacer is line) self-aligned sextuple patterning (SASP) process which accommodates two types of spacers, while gates are fabricated by a more pitch-relaxed self-aligned quadruple patterning (SAQP) process which only allows one type of spacer. A number of possible inverter and SRAM structures are identified and the related circuit multi-modality is studied using the developed failure-probability and yield models. It is shown that SRAM circuit yield is significantly impacted by the multi-modality of fins' spatial variations in a SRAM cell. The sensitivity of 6-transistor SRAM read/write failure probability to SASP process variations is calculated and the specific circuit type with the highest probability to fail in the reading/writing operation is identified. Our study suggests that the 6-transistor SRAM configuration may not be scalable to 7-nm half pitch and more robust SRAM circuit design needs to be researched.
Generating Effective Models and Parameters for RNA Genetic Circuits.
Hu, Chelsea Y; Varner, Jeffrey D; Lucks, Julius B
2015-08-21
RNA genetic circuitry is emerging as a powerful tool to control gene expression. However, little work has been done to create a theoretical foundation for RNA circuit design. A prerequisite to this is a quantitative modeling framework that accurately describes the dynamics of RNA circuits. In this work, we develop an ordinary differential equation model of transcriptional RNA genetic circuitry, using an RNA cascade as a test case. We show that parameter sensitivity analysis can be used to design a set of four simple experiments that can be performed in parallel using rapid cell-free transcription-translation (TX-TL) reactions to determine the 13 parameters of the model. The resulting model accurately recapitulates the dynamic behavior of the cascade, and can be easily extended to predict the function of new cascade variants that utilize new elements with limited additional characterization experiments. Interestingly, we show that inconsistencies between model predictions and experiments led to the model-guided discovery of a previously unknown maturation step required for RNA regulator function. We also determine circuit parameters in two different batches of TX-TL, and show that batch-to-batch variation can be attributed to differences in parameters that are directly related to the concentrations of core gene expression machinery. We anticipate the RNA circuit models developed here will inform the creation of computer aided genetic circuit design tools that can incorporate the growing number of RNA regulators, and that the parametrization method will find use in determining functional parameters of a broad array of natural and synthetic regulatory systems. PMID:26046393
A neurocomputational model of the mammalian fear conditioning circuit
Anderson, Charles H.
A neurocomputational model of the mammalian fear conditioning circuit by Carter Kolbeck A thesis that reproduces the high-level behavioural results of well-known fear conditioning experiments: first these connections perform, I developed an information processing system that behaves analogously to the fear condi
Modeling an optical magnetometer with electronic circuits Analysis and optimization
Modeling an optical magnetometer with electronic circuits Analysis and optimization Przemyslaw, University of California at Berkeley Berkeley, California 94720-7300, USA ABSTRACT: Optical magnetometers are typically obtained for ultra-low-field measurements, a group of optical magnetometers allows the detection
Mapping and Cracking Sensorimotor Circuits in Genetic Model Organisms
Clark, Damon A.; Freifeld, Limor; Clandinin, Thomas R.
2013-01-01
One central goal of systems neuroscience is to understand how neural circuits implement the computations that link sensory inputs to behavior. Work combining electrophysiological and imaging-based approaches to measure neural activity with pharmacological and electrophysiological manipulations has provided fundamental insights. More recently, genetic approaches have been used to monitor and manipulate neural activity, opening up new experimental opportunities and challenges. Here, we discuss issues associated with applying genetic approaches to circuit dissection in sensorimotor transformations, outlining important considerations for experimental design and considering how modeling can complement experimental approaches. PMID:23719159
Using Hydraulic Network Models to Teach Electric Circuit Principles
NASA Astrophysics Data System (ADS)
Jones, Irvin; EERC (Engineering Education Research Center) Collaboration
2013-11-01
Unlike other engineering disciplines, teaching electric circuit principles is difficult for some students because there isn't a visual context to rely on. So concepts such as electric potential, current, resistance, capacitance, and inductance have little meaning outside of their definition and the derived mathematical relationships. As a work in progress, we are developing a tool to support teaching, learning, and research of electric circuits. The tool will allow the user to design, build, and operate electric circuits in the form of hydraulic networks. We believe that this system will promote greater learning of electric circuit principles by visually realizing the conceptual and abstract concepts of electric circuits. Furthermore, as a teaching and learning tool, the hydraulic network system can be used to teach and improve comprehension of electrical principles in K through 12 classrooms and in cross-disciplinary environments such as Bioengineering, Mechanical Engineering, Industrial Engineering, and Aeronautical Engineering. As a research tool, the hydraulic network can model and simulate micro/nano bio-electro-chemical systems. Organization within the Swanson School of Engineering at the University of Pittsburgh.
Classical and Quantum Stochastic Models of Resistive and Memristive Circuits
John E. Gough; Guofeng Zhang
2015-10-28
The purpose of this paper is to examine stochastic Markovian models for circuits in phase space for which the drift term is equivalent to the standard circuit equations. In particular we include dissipative components corresponding to both a resistor and a memristor in series. We obtain a dilation of the problem for which is canonical in the sense that the underlying Poisson Brackets structure is preserved under the stochastic flow. We do this first of all for standard Wiener noise, but also treat the problem using a new concept of symplectic noise where the Poisson structure is extended to the noise as well as the circuit variables, and in particular where we have canonically conjugate noises. Finally we construct a dilation which describes the quantum mechanical analogue.
NASA Astrophysics Data System (ADS)
Chun, Yon Do; Oh, Jae-Eung; Fujishima, Yasushi; Wakao, Shinji; Lee, Ju; Cho, Yun-Hyun
2005-05-01
In this article, in order to investigate the merits of three-dimensional (3D) equivalent magnetic circuit network (EMCN) method, a 3D standard benchmark model proposed by the Institute of Electrical Engineers of Japan is analyzed. We also examine the accuracy of analysis results, the computer storage, and the computation time through the systematical comparison between 3D EMCN method and 3D finite element method based on hexahedral edge element. The incomplete Cholesky conjugate gradient method was selected for the solver. From the results, we can confirm the usefulness of 3D EMCN method.
Measured turbulent mixing in a small-scale circuit breaker model
Basse, Nils Plesner
.2960. 1. Introduction In high voltage (HV) gas circuit breakers [1,2], short- circuit currentsMeasured turbulent mixing in a small-scale circuit breaker model N. P. T. Basse,* R. Bini, and M circuit breakers depends on the temperature distribution of hot gas or plasma from the arc zone mixed
NASA Astrophysics Data System (ADS)
Kim, Hwan-Choong; Han, Chulhee; Kim, Pyunghwa; Choi, Seung-Bok
2015-08-01
This work proposes a new approach with which to measure the magnetic flux density using the characteristics of magnetorheological fluid (MRF) that is integrated with a variable resistor. For convenience, it is called a magnetorheological fluid variable resistor (MRF-VR) system in this study. The mechanism of the MRF-VR is based on the interaction between ferromagnetic iron particles of the MRF due to an external magnetic field, which causes its electrical resistance to be field dependent. Using this salient principle, the proposed MRF-VR system is constructed with electrodes and MRF, and its performance is demonstrated by evaluating its electrical resistive characteristics such as dimensional influence, response time, hysteresis and frequency response. After evaluating the performance characteristics, a feedback control system with a proportional-integral-derivative (PID) controller is established, and resistance-trajectory control experiments are carried out. Based on this MRF-VR system, a magnetic field-sensing system is constructed using a Wheatstone bridge circuit, and a polynomial model for calculating the magnetic flux density is formulated from the measured voltage. Finally, the accuracy and effectiveness of the proposed sensing system associated with the empirical polynomial model is successfully verified by comparing the calculated values of magnetic flux density with those measured by a commercial tesla meter.
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.
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.
Development of a numerical computer code and circuit element models for simulation of firing systems
Carpenter, K.H. . Dept. of Electrical and Computer Engineering)
1990-07-02
Numerical simulation of firing systems requires both the appropriate circuit analysis framework and the special element models required by the application. We have modified the SPICE circuit analysis code (version 2G.6), developed originally at the Electronic Research Laboratory of the University of California, Berkeley, to allow it to be used on MSDOS-based, personal computers and to give it two additional circuit elements needed by firing systems--fuses and saturating inductances. An interactive editor and a batch driver have been written to ease the use of the SPICE program by system designers, and the interactive graphical post processor, NUTMEG, supplied by U. C. Berkeley with SPICE version 3B1, has been interfaced to the output from the modified SPICE. Documentation and installation aids have been provided to make the total software system accessible to PC users. Sample problems show that the resulting code is in agreement with the FIRESET code on which the fuse model was based (with some modifications to the dynamics of scaling fuse parameters). In order to allow for more complex simulations of firing systems, studies have been made of additional special circuit elements--switches and ferrite cored inductances. A simple switch model has been investigated which promises to give at least a first approximation to the physical effects of a non ideal switch, and which can be added to the existing SPICE circuits without changing the SPICE code itself. The effect of fast rise time pulses on ferrites has been studied experimentally in order to provide a base for future modeling and incorporation of the dynamic effects of changes in core magnetization into the SPICE code. This report contains detailed accounts of the work on these topics performed during the period it covers, and has appendices listing all source code written documentation produced.
CREATING DYNAMIC EQUIVALENT PV CIRCUIT MODELS WITH IMPEDANCE SPECTROSCOPY FOR ARC FAULT MODELING
National Laboratories, Albuquerque, NM, USA ABSTRACT Article 690.11 in the 2011 National Electrical Code. INTRODUCTION Sandia National Laboratories is researching the electromagnetic propagation characteristics-12] are used. One dynamic equivalent circuit model and the simplified electrical circuit model are shown
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.
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
A Corticothalamic Circuit Model for Sound Identification in Complex Scenes
Otazu, Gonzalo H.; Leibold, Christian
2011-01-01
The identification of the sound sources present in the environment is essential for the survival of many animals. However, these sounds are not presented in isolation, as natural scenes consist of a superposition of sounds originating from multiple sources. The identification of a source under these circumstances is a complex computational problem that is readily solved by most animals. We present a model of the thalamocortical circuit that performs level-invariant recognition of auditory objects in complex auditory scenes. The circuit identifies the objects present from a large dictionary of possible elements and operates reliably for real sound signals with multiple concurrently active sources. The key model assumption is that the activities of some cortical neurons encode the difference between the observed signal and an internal estimate. Reanalysis of awake auditory cortex recordings revealed neurons with patterns of activity corresponding to such an error signal. PMID:21931668
Modeling of magnetic cloud expansion
NASA Astrophysics Data System (ADS)
Vandas, M.; Romashets, E.; Geranios, A.
2015-11-01
Aims: Magnetic clouds are large interplanetary flux ropes that propagate in the solar wind from the Sun and that expand during their propagation. We check how magnetic cloud models, represented by cylindrical magnetic flux ropes, which include expansion, correspond to in situ observations. Methods: Spacecraft measurements of magnetic field and velocity components inside magnetic clouds with clearly expressed expansion are studied in detail and fit by models. The models include expanding cylindrical linear force-free flux ropes with circular or elliptic cross sections. Results: From the period of 1995-2009, 26 magnetic clouds were fit by the force-free model of an expanding circular cylindrical flux rope. Expansion velocity profiles qualitatively correspond to model ones in the majority of cases (81%) and quantitatively in more than half of them (58%). In four cases an elliptic cross section significantly improved a match between observed and modeled expansion velocity profiles. Conclusions: Analysis of velocity components tests magnetic cloud models more strictly and may reveal information on magnetic cloud shapes.
A Circuit Level Fault Model for Resistive Shorts of MOS Gate Oxide , Wangqi Qiu
Walker, Duncan M. "Hank"
A Circuit Level Fault Model for Resistive Shorts of MOS Gate Oxide Xiang Lu , Zhuo Li , Wangqi Qiu shorts to changes in the nominal circuit. Hao and McCluskey [5] studied the logic and delay behavior of resistive shorts. Their circuit level fault model is shown in Figure 1, which covers the external behaviors
DISSECTING OCD CIRCUITS: FROM ANIMAL MODELS TO TARGETED TREATMENTS.
Ahmari, Susanne E; Dougherty, Darin D
2015-08-01
Obsessive-compulsive disorder (OCD) is a chronic, severe mental illness with up to 2-3% prevalence worldwide. In fact, OCD has been classified as one of the world's 10 leading causes of illness-related disability according to the World Health Organization, largely because of the chronic nature of disabling symptoms.([1]) Despite the severity and high prevalence of this chronic and disabling disorder, there is still relatively limited understanding of its pathophysiology. However, this is now rapidly changing due to development of powerful technologies that can be used to dissect the neural circuits underlying pathologic behaviors. In this article, we describe recent technical advances that have allowed neuroscientists to start identifying the circuits underlying complex repetitive behaviors using animal model systems. In addition, we review current surgical and stimulation-based treatments for OCD that target circuit dysfunction. Finally, we discuss how findings from animal models may be applied in the clinical arena to help inform and refine targeted brain stimulation-based treatment approaches. PMID:25952989
NASA Astrophysics Data System (ADS)
Liang, Mai-Lin; Wang, Teng
2015-11-01
The magnetic field of the infinite solenoid is calculated using a new method. An infinitely long charged line moving along a closed curve on the plane perpendicular to the infinite line will generate an electric current and so the magnetic field of the infinite solenoid. Through the electric-magnetic field relation, the magnetic field of the infinite solenoid is simply obtained and the reason why the magnetic field is a constant is clearly shown. Further, Ampere’s circuital law is analyzed from the particle point of view using the electric-magnetic field relation. These discussions are helpful to the understanding of the magnetic field of the infinite solenoid and Ampere’s circuital law for students and teachers of electromagnetism.
NASA Astrophysics Data System (ADS)
Zhang, Qiu-Shi; Zhu, Feng-Jie; Zhou, Hao-Miao
2015-10-01
A lumped-equivalent circuit model of a novel magnetoelectric tunable bandpass filter, which is realized in the form of multi-stage cascading between a plurality of magnetoelectric laminates, is established in this paper for convenient analysis. The multi-stage cascaded filter is degraded to the coupling microstrip filter with only one magnetoelectric laminate and then compared with the existing experiment results. The comparison reveals that the insertion loss curves predicted by the degraded circuit model are in good agreement with the experiment results and the predicted results of the electromagnetic field simulation, thus the validity of the model is verified. The model is then degraded to the two-stage cascaded magnetoelectric filter with two magnetoelectric laminates. It is revealed that if the applied external bias magnetic or electric fields on the two magnetoelectric laminates are identical, then the passband of the filter will drift under the changed external field; that is to say, the filter has the characteristics of external magnetic field tunability and electric field tunability. If the applied external bias magnetic or electric fields on two magnetoelectric laminates are different, then the passband will disappear so that the switching characteristic is achieved. When the same magnetic fields are applied to the laminates, the passband bandwidth of the two-stage cascaded magnetoelectric filter with two magnetoelectric laminates becomes nearly doubled in comparison with the passband filter which contains only one magnetoelectric laminate. The bandpass effect is also improved obviously. This research will provide a theoretical basis for the design, preparation, and application of a new high performance magnetoelectric tunable microwave device. Project supported by the National Natural Science Foundation of China (Grant Nos. 11172285 and 11472259) and the Natural Science Foundation of Zhejiang Province, China (Grant No. LR13A020002).
Universal analytic model for tunnel FET circuit simulation
NASA Astrophysics Data System (ADS)
Lu, Hao; Esseni, David; Seabaugh, Alan
2015-06-01
A simple analytic model based on the Kane-Sze formula is used to describe the current-voltage characteristics of tunnel field-effect transistors (TFETs). This model captures the unique features of the TFET including the decrease in subthreshold swing with drain current and the superlinear onset of the output characteristic. The model also captures the ambipolar current characteristic at negative gate-source bias and the negative differential resistance for negative drain-source biases. A simple empirical capacitance model is also included to enable circuit simulation. The model has fairly general validity and is not specific to a particular TFET geometry. Good agreement is shown with published atomistic simulations of an InAs double-gate TFET with gate perpendicular to the tunnel junction and with numerical simulations of a broken-gap AlGaSb/InAs TFET with gate in parallel with the tunnel junction.
ECE 586 Fault Detection in Digital Circuits Lecture 09 Fault Modeling I
Wang, Jia
ECE 586 Fault Detection in Digital Circuits Lecture 09 Fault Modeling I Professor Jia Wang Fault Detection in Digital Circuits Spring 2015 1/24 #12;Reading Assignment This lecture: 4.1, 4.2 Next lecture: 4.2 4.4 ECE 586 Fault Detection in Digital Circuits Spring 2015 2/24 #12;Homework 2 Due: 5
ECE 586 Fault Detection in Digital Circuits Lecture 11 Fault Modeling III
Wang, Jia
ECE 586 Fault Detection in Digital Circuits Lecture 11 Fault Modeling III Professor Jia Wang Fault Detection in Digital Circuits Spring 2015 1/19 #12;Reading Assignment This lecture: 4.5, 4.6 Next lecture: 5.1, 5.2 ECE 586 Fault Detection in Digital Circuits Spring 2015 2/19 #12;Outline The Single
ECE 586 Fault Detection in Digital Circuits Lecture 10 Fault Modeling II
Wang, Jia
ECE 586 Fault Detection in Digital Circuits Lecture 10 Fault Modeling II Professor Jia Wang Fault Detection in Digital Circuits Spring 2015 1/17 #12;Literature Survey Choose one research article for details. ECE 586 Fault Detection in Digital Circuits Spring 2015 2/17 #12;Literature Survey Choose one
A Visualization Tool for CFD Models of Convectively Cooled Printed Circuit Boards
Recktenwald, Gerald
The Printed Circuit Board Convection Analysis Tools (PCBCAT) are a collection of computer programsA Visualization Tool for CFD Models of Convectively Cooled Printed Circuit Boards Gerald W of printed circuit boards (PCBs) has been developed using AVS (Application Visualization System from AVS, Inc
Modelling of bulk superconductor magnetization
NASA Astrophysics Data System (ADS)
Ainslie, M. D.; Fujishiro, H.
2015-05-01
This paper presents a topical review of the current state of the art in modelling the magnetization of bulk superconductors, including both (RE)BCO (where RE = rare earth or Y) and MgB2 materials. Such modelling is a powerful tool to understand the physical mechanisms of their magnetization, to assist in interpretation of experimental results, and to predict the performance of practical bulk superconductor-based devices, which is particularly important as many superconducting applications head towards the commercialization stage of their development in the coming years. In addition to the analytical and numerical techniques currently used by researchers for modelling such materials, the commonly used practical techniques to magnetize bulk superconductors are summarized with a particular focus on pulsed field magnetization (PFM), which is promising as a compact, mobile and relatively inexpensive magnetizing technique. A number of numerical models developed to analyse the issues related to PFM and optimise the technique are described in detail, including understanding the dynamics of the magnetic flux penetration and the influence of material inhomogeneities, thermal properties, pulse duration, magnitude and shape, and the shape of the magnetization coil(s). The effect of externally applied magnetic fields in different configurations on the attenuation of the trapped field is also discussed. A number of novel and hybrid bulk superconductor structures are described, including improved thermal conductivity structures and ferromagnet-superconductor structures, which have been designed to overcome some of the issues related to bulk superconductors and their magnetization and enhance the intrinsic properties of bulk superconductors acting as trapped field magnets. Finally, the use of hollow bulk cylinders/tubes for shielding is analysed.
Wei, Jinwu; Feng, Hongmei; Zhu, Zengtai; Liu, Qingfang; Wang, Jianbo
2015-11-01
A short-circuited coplanar waveguide jig was proposed due to its simple structure and potential applications, which was successfully used to measure the permeability spectra of magnetic thin film. The result obtained from the coplanar waveguide (CPW) jig exhibits typical ferromagnetic resonance spectra, which can be well fitted by a trade-off equation because the measured permeability spectra have a bit of asymmetry because of the special intensity distribution of the microwave magnetic field in the CPW. In order to confirm the availability of the shorted CPW jig, a previous short-circuited microstrip line jig was used to measure the permeability spectra of the same sample. The dynamic permeability results obtained by using different jigs are commendably consistent, and the accurate and valid results are also confirmed by using the vector network analyzer ferromagnetic resonance method. PMID:26628157
NASA Astrophysics Data System (ADS)
Wei, Jinwu; Feng, Hongmei; Zhu, Zengtai; Liu, Qingfang; Wang, Jianbo
2015-11-01
A short-circuited coplanar waveguide jig was proposed due to its simple structure and potential applications, which was successfully used to measure the permeability spectra of magnetic thin film. The result obtained from the coplanar waveguide (CPW) jig exhibits typical ferromagnetic resonance spectra, which can be well fitted by a trade-off equation because the measured permeability spectra have a bit of asymmetry because of the special intensity distribution of the microwave magnetic field in the CPW. In order to confirm the availability of the shorted CPW jig, a previous short-circuited microstrip line jig was used to measure the permeability spectra of the same sample. The dynamic permeability results obtained by using different jigs are commendably consistent, and the accurate and valid results are also confirmed by using the vector network analyzer ferromagnetic resonance method.
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.
D’Ostilio, Kevin; Rothwell, John C; Murphy, David L
2014-01-01
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 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 (<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 10 healthy volunteers. Significance The cTMS3 features could extend the utility of TMS as a research, diagnostic, and therapeutic tool. PMID:25242286
Digital quantum simulation of fermionic models with a superconducting circuit
Barends, R.; Lamata, L.; Kelly, J.; García-Álvarez, L.; Fowler, A. G.; Megrant, A; Jeffrey, E; White, T. C.; Sank, D.; Mutus, J. Y.; Campbell, B.; Chen, Yu; Chen, Z.; Chiaro, B.; Dunsworth, A.; Hoi, I.-C.; Neill, C.; O'Malley, P. J. J.; Quintana, C.; Roushan, P.; Vainsencher, A.; Wenner, J.; Solano, E.; Martinis, John M.
2015-01-01
One of the key applications of quantum information is simulating nature. Fermions are ubiquitous in nature, appearing in condensed matter systems, chemistry and high energy physics. However, universally simulating their interactions is arguably one of the largest challenges, because of the difficulties arising from anticommutativity. Here we use digital methods to construct the required arbitrary interactions, and perform quantum simulation of up to four fermionic modes with a superconducting quantum circuit. We employ in excess of 300 quantum logic gates, and reach fidelities that are consistent with a simple model of uncorrelated errors. The presented approach is in principle scalable to a larger number of modes, and arbitrary spatial dimensions. PMID:26153660
Digital quantum simulation of fermionic models with a superconducting circuit.
Barends, R; Lamata, L; Kelly, J; García-Álvarez, L; Fowler, A G; Megrant, A; Jeffrey, E; White, T C; Sank, D; Mutus, J Y; Campbell, B; Chen, Yu; Chen, Z; Chiaro, B; Dunsworth, A; Hoi, I-C; Neill, C; O'Malley, P J J; Quintana, C; Roushan, P; Vainsencher, A; Wenner, J; Solano, E; Martinis, John M
2015-01-01
One of the key applications of quantum information is simulating nature. Fermions are ubiquitous in nature, appearing in condensed matter systems, chemistry and high energy physics. However, universally simulating their interactions is arguably one of the largest challenges, because of the difficulties arising from anticommutativity. Here we use digital methods to construct the required arbitrary interactions, and perform quantum simulation of up to four fermionic modes with a superconducting quantum circuit. We employ in excess of 300 quantum logic gates, and reach fidelities that are consistent with a simple model of uncorrelated errors. The presented approach is in principle scalable to a larger number of modes, and arbitrary spatial dimensions. PMID:26153660
Digital quantum simulation of fermionic models with a superconducting circuit
NASA Astrophysics Data System (ADS)
Barends, R.; Lamata, L.; Kelly, J.; García-Álvarez, L.; Fowler, A. G.; Megrant, A.; Jeffrey, E.; White, T. C.; Sank, D.; Mutus, J. Y.; Campbell, B.; Chen, Yu; Chen, Z.; Chiaro, B.; Dunsworth, A.; Hoi, I.-C.; Neill, C.; O'Malley, P. J. J.; Quintana, C.; Roushan, P.; Vainsencher, A.; Wenner, J.; Solano, E.; Martinis, John M.
2015-07-01
One of the key applications of quantum information is simulating nature. Fermions are ubiquitous in nature, appearing in condensed matter systems, chemistry and high energy physics. However, universally simulating their interactions is arguably one of the largest challenges, because of the difficulties arising from anticommutativity. Here we use digital methods to construct the required arbitrary interactions, and perform quantum simulation of up to four fermionic modes with a superconducting quantum circuit. We employ in excess of 300 quantum logic gates, and reach fidelities that are consistent with a simple model of uncorrelated errors. The presented approach is in principle scalable to a larger number of modes, and arbitrary spatial dimensions.
Simulations of magnetic field gradients due to micro-magnets on a triple quantum dot circuit
Poulin-Lamarre, G.; Bureau-Oxton, C.; Kam, A.; Zawadzki, P.; Aers, G.; Studenikin, S.; Pioro-Ladrière, M.; Sachrajda, A. S.
2013-12-04
To quantify the effects of local magnetic fields on triple quantum dots, the Heisenberg Hamiltonian has been diagonalized for three electrons coupled via the exchange interaction. In particular, we have investigated different geometries of micro-magnets located on top of the triple dot in order to optimize the field gradient characteristics. In this paper, we focus on two geometries which are candidates for an addressable EDSR triple quantum dot device.
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.
Modeling the Electrical Characteristics of the Global Electric Circuit
NASA Astrophysics Data System (ADS)
Lucas, G.; Lehto, E.; Baumgaertner, A. J.; Thayer, J. P.; Forbes, J. M.; Zhang, X.
2013-12-01
Earth's global electric circuit (GEC) embodies the electrical pathways by which currents flow from electrified clouds to the ionosphere and return through fair weather regions to the earth's surface. To investigate this pathway, an analytic model based on others' previous work has been developed to produce global estimates of atmospheric currents, electric fields, and potential distributions of the GEC. The atmosphere between the ground and the ionosphere is composed of complex current sources and conductivity distributions. In the global electric circuit, lightning events act as current generators maintaining the potential difference between the earth and ionosphere. An analytic solution to Poisson's equation was applied to the GEC, allowing for a steady-state calculation of global distributions in potential, electric fields and currents for specified conductivity distributions and current sources. The global distribution of current sources provided on a monthly basis by a recently developed empirical model of Wilson currents. Analytic representations of global conductivities are implemented that include large-scale changes in the galactic cosmic ray flux. A novel numeric solver for Poisson's equation was also developed to enable analysis of more complex distributions of conductivity, i.e. cloud and aerosol effects. These models allow one to determine how different lightning and conductivity distributions impact the electrical characteristics of the GEC.
Data Mining Approaches for Modeling Complex Electronic Circuit Design Activities
Kwon, Yongjin; Omitaomu, Olufemi A; Wang, Gi-Nam
2008-01-01
A printed circuit board (PCB) is an essential part of modern electronic circuits. It is made of a flat panel of insulating materials with patterned copper foils that act as electric pathways for various components such as ICs, diodes, capacitors, resistors, and coils. The size of PCBs has been shrinking over the years, while the number of components mounted on these boards has increased considerably. This trend makes the design and fabrication of PCBs ever more difficult. At the beginning of design cycles, it is important to estimate the time to complete the steps required accurately, based on many factors such as the required parts, approximate board size and shape, and a rough sketch of schematics. Current approach uses multiple linear regression (MLR) technique for time and cost estimations. However, the need for accurate predictive models continues to grow as the technology becomes more advanced. In this paper, we analyze a large volume of historical PCB design data, extract some important variables, and develop predictive models based on the extracted variables using a data mining approach. The data mining approach uses an adaptive support vector regression (ASVR) technique; the benchmark model used is the MLR technique currently being used in the industry. The strengths of SVR for this data include its ability to represent data in high-dimensional space through kernel functions. The computational results show that a data mining approach is a better prediction technique for this data. Our approach reduces computation time and enhances the practical applications of the SVR technique.
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.
NASA Technical Reports Server (NTRS)
Wang, R.; Demerdash, N. A.
1992-01-01
The combined magnetic vector potential - magnetic scalar potential method of computation of 3D magnetic fields by finite elements, introduced in a companion paper, is used for global 3D field analysis and machine performance computations under open-circuit and short-circuit conditions for an example 14.3 kVA modified Lundell alternator, whose magnetic field is of intrinsic 3D nature. The computed voltages and currents under these machine test conditions were verified and found to be in very good agreement with corresponding test data. Results of use of this modelling and computation method in the study of a design alteration example, in which the stator stack length of the example alternator is stretched in order to increase voltage and volt-ampere rating, are given here. These results demonstrate the inadequacy of conventional 2D-based design concepts and the imperative of use of this type of 3D magnetic field modelling in the design and investigation of such machines.
Wu, Ke-Li
Physically Expressive Circuit Model for Multilayer RF Embedded Passives Jie Wang and Ke-Li Wu, Senior Member, IEEE Abstract--In this paper, a derived physically expressive circuit model is presented on the partial-element equivalent-circuit (PEEC) model and a simple circuit transformation. By defining
SPICE models for thermal and vibration analysis of printed circuit boards
NASA Astrophysics Data System (ADS)
Chen, Jesse E.; Yip, Gary
This paper describes circuit models for characterizing the thermal and dynamic behavior of printed circuit boards. The thermal model simulates the transient temperature distribution resulting from dissipative components and conductive, convective, and radiative boundaries. The dynamic model predicts the fundamental frequency for clamped edges. Both models are based on finite difference equations and confirmed by traditional methods.
Characteristics and computer model simulation of magnetic damping forces in maglev systems
NASA Astrophysics Data System (ADS)
He, J. L.; Rote, D. M.; Chen, S. S.
1994-05-01
This report discusses the magnetic damping force in electrodynamic suspension (EDS) maglev systems. The computer model simulations, which combine electrical system equations with mechanical motion equations on the basis of dynamic circuit theory, were conducted for a loop-shaped coil guideway. The intrinsic damping characteristics of the EDS-type guideway are investigated, and the negative damping phenomenon is confirmed by the computer simulations. The report also presents a simple circuit model to aid in understanding damping-force characteristics.
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.
The 4C code for the cryogenic circuit conductor and coil modeling in ITER
NASA Astrophysics Data System (ADS)
Savoldi Richard, L.; Casella, F.; Fiori, B.; Zanino, R.
2010-03-01
A new tool - the 4C code - has been developed, which allows the thermal-hydraulic simulation of the entire superconducting magnet system of the International Thermonuclear Experimental Reactor (ITER), with particular reference to: (1) the winding made of cable-in-conduit conductors (CICC), (2) the structures (the radial plates and the case of the toroidal field - TF - coils, for instance) and (3) the cooling circuits. In this paper the different components of the 4C code (1D 2-channel model of the CICC and of the structure cooling channels, 2D model of selected cross sections of the structures, 0D/1D model of the cryogenic circuit) are described in detail, together with the strategy adopted for the coupling between the different components and their integration in a single tool. The new tool is then applied to the modeling of two transients in an ITER TF coil: a simplified version of a cooldown of the coil and the response to a heat pulse applied in the winding.
An Accurate Timing Model for Nano CMOS Circuit Considering Statistical Process Variation
Ayers, Joseph
An Accurate Timing Model for Nano CMOS Circuit Considering Statistical Process Variation Ping Liu variations and global parameter variations [1]. Some researchers also define the fluctuations as systematic
Extraction of Gate Level Models from Transistor Circuits by Four-Valued Symbolic Analysis
Bryant, Randal E.
Extraction of Gate Level Models from Transistor Circuits by Four-Valued Symbolic Analysis Randal E-level representation of an MOS transistor circuit. The resulting model contains only four-valued unit and zero delay transistors, stored charge, and multiple signal strengths. It produces models with size comparable to ones
Polemi, Alessia; Shuford, Kevin L
2012-01-01
In this paper, we show how light absorption in a plasmonic grating nanosurface can be calculated by means of a simple, analytical model based on a transmission line equivalent circuit. The nanosurface is a one-dimensional grating etched into a silver metal film covered by a silicon slab. The transmission line model is specified for both transverse electric and transverse magnetic polarizations of the incident light, and it incorporates the effect of the plasmonic modes diffracted by the ridges of the grating. Under the assumption that the adjacent ridges are weakly interacting in terms of diffracted waves, we show that the approximate, closed form expression for the reflection coefficient at the air-silicon interface can be used to evaluate light absorption of the solar cell. The weak-coupling assumption is valid if the grating structure is not closely packed and the excitation direction is close to normal incidence. Also, we show the utility of the circuit theory for understanding how the peaks in the absorption coefficient are related to the resonances of the equivalent transmission model and how this can help in designing more efficient structures. PMID:22379681
Magnetic reconnection models of flares
NASA Technical Reports Server (NTRS)
Forbes, T. G.
1988-01-01
The most feasible energy source for solar and stellar flares is the energy stored in coronal magnetic fields. To convert a significant fraction of this energy into heat and kinetic energy in a short time requires rapid change in the topology of the magnetic fields, and hence, rapid reconnection of field lines. Recent numerical and analytical models of solar flares suggest that the magnetic energy released by reconnection drives chromospheric ablation in the flare ribbons. Simple theoretical arguments based on compressible reconnection theory predict that the temperature of the ablated plasma should be about 1.03 x 10 to the 6th B exp 0.62 K where B is the coronal magnetic field strength in Gauss.
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
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
A functional circuit model of interaural time difference processing
McColgan, Thomas; Shah, Sahil; Köppl, Christine; Carr, Catherine
2014-01-01
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
A two-port analogous circuit and SPICE model for Salmon's family of acoustic horns
Leach Jr.,W. Marshall
A two-port analogous circuit and SPICE model for Salmon's family of acoustic horns W. Marshall-port electroacoustic analogous circuit model for finite-length acoustic horns belonging to Salmon's family of horns the quasi-one-dimensional Webster horn equation7 and that the horn is one of Salmon's family of horns.8
Neuron Ion Channels and an Ion Channel Circuit Model version 23 September 2013
Miller, Damon A.
Neuron Ion Channels and an Ion Channel Circuit Model version 23 September 2013 ECE 5730 Foundations. Develop and simulate a circuit model of the ion channel described in the "Sodium Channel Identification statistical analyses as ion channel operation is stochastic. Some of your work will likely require a random
Circuit Model of Carbon-Nanotube Inks for Microelectronic and Microwave Tunable Devices
Tentzeris, Manos
Circuit Model of Carbon-Nanotube Inks for Microelectronic and Microwave Tunable Devices Rosa De parameters. The obtained results demonstrate that, by acting on the gap size and on the number of CNT ink the suggested equivalent circuit model, the CNT ink deposition process can be considered as a promising
A circuit model of the temporal pattern generator of Caenorhabditis egg-laying behavior
Schafer, William R.
A circuit model of the temporal pattern generator of Caenorhabditis egg-laying behavior stochastic equations can be used to simulate the time course of egg-laying according to our circuit model: p0 of egg-laying events. 1 #12;2 PARAMETERS 2 2 Parameters The constant probability p0 characterizes
Creating dynamic equivalent PV circuit models with impedance spectroscopy for arc-fault modeling.
Johnson, Jay Dean; Kuszmaul, Scott S.; Strauch, Jason E.; Schoenwald, David Alan
2011-06-01
Article 690.11 in the 2011 National Electrical Code{reg_sign} (NEC{reg_sign}) requires new photovoltaic (PV) systems on or penetrating a building to include a listed arc fault protection device. Currently there is little experimental or empirical research into the behavior of the arcing frequencies through PV components despite the potential for modules and other PV components to filter or attenuate arcing signatures that could render the arc detector ineffective. To model AC arcing signal propagation along PV strings, the well-studied DC diode models were found to inadequately capture the behavior of high frequency arcing signals. Instead dynamic equivalent circuit models of PV modules were required to describe the impedance for alternating currents in modules. The nonlinearities present in PV cells resulting from irradiance, temperature, frequency, and bias voltage variations make modeling these systems challenging. Linearized dynamic equivalent circuits were created for multiple PV module manufacturers and module technologies. The equivalent resistances and capacitances for the modules were determined using impedance spectroscopy with no bias voltage and no irradiance. The equivalent circuit model was employed to evaluate modules having irradiance conditions that could not be measured directly with the instrumentation. Although there was a wide range of circuit component values, the complex impedance model does not predict filtering of arc fault frequencies in PV strings for any irradiance level. Experimental results with no irradiance agree with the model and show nearly no attenuation for 1 Hz to 100 kHz input frequencies.
NASA Astrophysics Data System (ADS)
Mian, Muhammad Umer; Dennis, John Ojur; Khir, M. H. Md.; Riaz, Kashif; Iqbal, Abid; Bazaz, Shafaat A.; Tang, T. B.
2015-07-01
Pre-fabrication, behavioural and performance analysis with computer aided design (CAD) tools is a common and fabrication cost effective practice. In light of this we present a simulation methodology for a dual-mass oscillator based 3 Degree of Freedom (3-DoF) MEMS gyroscope. 3-DoF Gyroscope is modeled through lumped parameter models using equivalent circuit elements. These equivalent circuits consist of elementary components which are counterpart of their respective mechanical components, used to design and fabricate 3-DoF MEMS gyroscope. Complete designing of equivalent circuit model, mathematical modeling and simulation are being presented in this paper. Behaviors of the equivalent lumped models derived for the proposed device design are simulated in MEMSPRO T-SPICE software. Simulations are carried out with the design specifications following design rules of the MetalMUMPS fabrication process. Drive mass resonant frequencies simulated by this technique are 1.59 kHz and 2.05 kHz respectively, which are close to the resonant frequencies found by the analytical formulation of the gyroscope. The lumped equivalent circuit modeling technique proved to be a time efficient modeling technique for the analysis of complex MEMS devices like 3-DoF gyroscopes. The technique proves to be an alternative approach to the complex and time consuming couple field analysis Finite Element Analysis (FEA) previously used.
Modelling of bulk superconductor magnetization
Ainslie, Mark D.; Fujishiro, H.
2015-03-30
the temperature rise comes from the local dissipation due to magnetic flux motion. Figure 3. Comparison for MgB2 and (RE)BCO bulk superconductors of (a) Specific heat and (b) Thermal conductivity. Jc0(T) is the temperature dependent critical current density... the magnetizing coil itself as a separate entity in the model to investigate the influence of the coil type and shape on the trapped field, e.g., solenoid [78,98], vortex [128] and split [100] coils. The applied field can take a variety of forms – sinusoidal...
Roldán, A. Roldán, J. B.; Reig, C.; Cardoso, S.; Cardoso, F.; Ferreira, R.; Freitas, P. P.
2014-05-07
Full instrumentation bridges based on spin valve of giant magnetoresistance and magnetic tunnel junction devices have been microfabricated and experimentally characterized from the DC and noise viewpoint. A more realistic model of these devices was obtained in this work, an electrical and thermal model previously developed have been improved in such a way that noise effects are also included. We have implemented the model in a circuit simulator and reproduced the experimental measurements accurately. This provides a more realistic and complete tool for circuit design where magnetoresistive elements are combined with well-known complementary metal–oxide–semiconductor modules.
Exploring the Control Circuit of Cell Migration by Mathematical Modeling
Satulovsky, Javier; Lui, Roger; Wang, Yu-li
2008-01-01
We have developed a top-down, rule-based mathematical model to explore the basic principles that coordinate mechanochemical events during animal cell migration, particularly the local-stimulation-global-inhibition model suggested originally for chemotaxis. Cells were modeled as a shape machine that protrudes or retracts in response to a combination of local protrusion and global retraction signals. Using an optimization algorithm to identify parameters that generate specific shapes and migration patterns, we show that the mechanism of local stimulation global inhibition can readily account for the behavior of Dictyostelium under a large collection of conditions. Within this collection, some parameters showed strong correlation, indicating that a normal phenotype may be maintained by complementation among functional modules. In addition, comparison of parameters for control and nocodazole-treated Dictyostelium identified the most prominent effect of microtubules as regulating the rates of retraction and protrusion signal decay, and the extent of global inhibition. Other changes in parameters can lead to profound transformations from amoeboid cells into cells mimicking keratocytes, neurons, or fibroblasts. Thus, a simple circuit of local stimulation-global inhibition can account for a wide range of cell behaviors. A similar top-down approach may be applied to other complex problems and combined with molecular manipulations to define specific protein functions. PMID:18199677
LARGE SCALE DISTRIBUTED PARAMETER MODEL OF MAIN MAGNET SYSTEM AND FREQUENCY DECOMPOSITION ANALYSIS
ZHANG,W.; MARNERIS, I.; SANDBERG, J.
2007-06-25
Large accelerator main magnet system consists of hundreds, even thousands, of dipole magnets. They are linked together under selected configurations to provide highly uniform dipole fields when powered. Distributed capacitance, insulation resistance, coil resistance, magnet inductance, and coupling inductance of upper and lower pancakes make each magnet a complex network. When all dipole magnets are chained together in a circle, they become a coupled pair of very high order complex ladder networks. In this study, a network of more than thousand inductive, capacitive or resistive elements are used to model an actual system. The circuit is a large-scale network. Its equivalent polynomial form has several hundred degrees. Analysis of this high order circuit and simulation of the response of any or all components is often computationally infeasible. We present methods to use frequency decomposition approach to effectively simulate and analyze magnet configuration and power supply topologies.
Li, Xin
Post-Silicon Performance Modeling and Tuning of Analog/Mixed- Signal Circuits via Bayesian Model Avenue, Pittsburgh, PA 15213, USA xinli@ece.cmu.edu ABSTRACT Post-silicon tuning has recently emerged for efficient post-silicon performance modeling and tuning of analog and mixed-signal (AMS) circuits. The key
Sheikholeslami, Ali
-MRAM) and spin logic circuits such as spin flip flops. This paper reviews several static and dynamic models- toresistive random-access memory (MRAM), modeling, spin-transfer-torque (STT). I. INTRODUCTION SPINTRONICS Random Access Memory (STT-MRAM), is an example of spintronic circuit, which has made significant progress
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.
An improved lumped element nonlinear circuit model for a circular CMUT cell.
Köymen, Hayrettin; Atalar, Abdullah; Aydo?du, Elif; Kocaba?, Co?kun; O?uz, H Ka?an; Olçum, Selim; Ozgurluk, Alper; Unlügedik, Asli
2012-08-01
This paper describes a correction and an extension in the previously published large signal equivalent circuit model for a circular capacitive micromachined ultrasonic transducer (CMUT) cell. The force model is rederived so that the energy and power is preserved in the equivalent circuit model. The model is able to predict the entire behavior of CMUT until the membrane touches the substrate. Many intrinsic properties of the CMUT cell, such as the collapse condition, collapse voltage, the voltage-displacement interrelation and the force equilibrium before and after collapse voltage in the presence of external static force, are obtained as a direct consequence of the model. The small signal equivalent circuit for any bias condition is obtained from the large signal model. The model can be implemented in circuit simulation tools and model predictions are in excellent agreement with finite element method simulations. PMID:22899125
Swidzinski, Jan
1997-01-01
The objective of this thesis is to develop efficient methodologies for statistical behavioral modeling of analog integrated circuits and apply them to practical problems. Through appropriate statistical modeling, the Design for Quality (DFQ...
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 SYSTEM MODELING...
Modeling quantum noise for efficient testing of fault-tolerant circuits
Easwar Magesan; Daniel Puzzuoli; Christopher E. Granade; David G. Cory
2012-06-23
Understanding fault-tolerant properties of quantum circuits is important for the design of large-scale quantum information processors. In particular, simulating properties of encoded circuits is a crucial tool for investigating the relationships between the noise model, encoding scheme, and threshold value. For general circuits and noise models, these simulations quickly become intractable in the size of the encoded circuit. We introduce methods for approximating a noise process by one which allows for efficient Monte Carlo simulation of properties of encoded circuits. The approximations are as close to the original process as possible without overestimating their ability to preserve quantum information, a key property for obtaining more honest estimates of threshold values. We numerically illustrate the method with various physically relevant noise models.
Probabilistic model of fault detection in quantum circuits
Anindita Banerjee; Anirban Pathak
2009-05-12
It is shown that the fault testing for quantum circuits does not follow conventional classical techniques. If probabilistic gate like Hadamard gate is included in a circuit then the classical notion of test vector is shown to fail. We have reported several new and distinguishing features of quantum fault and also presented a general methodology for detection of functional faults in a quantum circuit. The technique can generate test vectors for detection of different kinds of fault. Specific examples are given and time complexity of the proposed quantum fault detection algorithm is reported.
Log-Domain Circuit Models of Chemical Reactions Soumyajit Mandal and Rahul Sarpeshkar
Sarpeshkar, Rahul
Log-Domain Circuit Models of Chemical Reactions Soumyajit Mandal and Rahul Sarpeshkar Department to networks of chemical reactions. Our circuits can be used for transient and steady-state simulations the energy barrier of a chemical reaction, exponentially changing its speed. In an analogous fashion, gate
Modeling of Large Scale RF-MEMS Circuits Using Efficient Time-Domain Techniques
Tentzeris, Manos
Modeling of Large Scale RF-MEMS Circuits Using Efficient Time-Domain Techniques N. Bushyager, E Engineering Georgia Institute of Technology Atlanta, GA 30332-0250, USA Abstract RF-MEMS design is made difficult due to the lack of tools capable of simulating both MEMS devices and their surrounding circuits
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 ...
Circuit models and SPICE macro-models for quantum Hall effect devices
NASA Astrophysics Data System (ADS)
Ortolano, Massimo; Callegaro, Luca
2015-08-01
Precise electrical measurement technology based on the quantum Hall effect is one of the pillars of modern quantum electrical metrology. Electrical networks including one or more QHE elements can be used as quantum resistance and impedance standards. The analysis of these networks allows metrologists to evaluate the effect of the inevitable parasitic parameters on their performance as standards. This paper presents a concise review of the various circuit models for QHE elements proposed in the literature, and the development of a new model. This last model is particularly suited to be employed with the analogue electronic circuit simulator SPICE. The SPICE macro-model and examples of SPICE simulations, validated by comparison with the corresponding analytical solution and/or experimental data, are provided.
Olcum, Selim; Yamaner, F Yalcin; Bozkurt, Ayhan; Köymen, Hayrettin; Atalar, Abdullah
2011-07-01
The collapse mode of operation of capacitive micromachined ultrasonic transducers (CMUTs) was shown to be a very effective way to achieve high output pressures. However, no accurate analytical or equivalent circuit model exists for understanding the mechanics and limits of the collapse mode. In this work, we develop an equivalent nonlinear electrical circuit that can accurately simulate the mechanical behavior of a CMUT with given dimensions and mechanical parameters under any large or small signal electrical excitation, including the collapse mode. The static and dynamic deflections of a plate predicted from the model are compared with finite element simulations. The equivalent circuit model can estimate the static deflection and transient behavior of a CMUT plate to within 5% accuracy. The circuit model is in good agreement with experimental results of pulse excitation applied to fabricated CMUTs. The model is suitable as a powerful design and optimization tool for collapsed and uncollapsed CMUTs. PMID:21768031
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.
Tosi, Guilherme Mohiyaddin, Fahd A.; Morello, Andrea; Huebl, Hans
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.
Int. J. Appl. Math. Comput. Sci., 2001, Vol.11, No.5, 11511171 REDUCTION OF LARGE CIRCUIT MODELS
Li, Jing-Rebecca
Int. J. Appl. Math. Comput. Sci., 2001, Vol.11, No.5, 11511171 REDUCTION OF LARGE CIRCUIT MODELS be easily adapted to allow for DC matching, as well as for passivity preservation for multi-port RLC circuit
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
A circuit model of the temporal pattern generator of Caenorhabditis egg-laying behavior
Zhang, Mi; Schafer, William R.; Breitling, Rainer
2010-06-07
for the time constant of the inactive phase. Together they form an integrated circuit that drives the clustered egg-laying pattern. Conclusions The detailed predictions derived from this model can now be tested by straightforward validation experiments....
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 ...
A computational model of gene expression in an inducible synthetic circuit.
Ceroni, Francesca; Furini, Simone; Cavalcanti, Silvio
2010-01-01
Synthetic biology aims to the rational design of gene circuits with predictable behaviours. Great efforts have been done so far to introduce in the field mathematical models that could facilitate the design of synthetic networks. Here we present a mathematical model of a synthetic gene-circuit with a negative feedback. The closed loop configuration allows the control of transcription by an inducer molecule (IPTG). Escherichia coli bacterial cells were transformed and expression of a fluorescent reporter (GFP) was measured for different inducer levels. Computer model simulations well reproduced the experimental induction data, using a single fitting parameter. Independent genetic components were used to assemble the synthetic circuit. The mathematical model here presented could be useful to predict how changes in these genetic components affect the behaviour of the synthetic circuit. PMID:19908393
Taylan, O.; Berberoglu, H.
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)
Hai, Ling; Svensson, Olle; Isberg, Jan; Leijon, Mats
2015-04-01
There is a need to have a reliable tool to quickly assess wave energy converters (WECs). This paper explores whether it is possible to apply the equivalent electric circuit theory as an evaluation tool for point absorbing WEC system modelling. The circuits were developed starting from the force analysis, in which the hydrodynamic, mechanical, and electrical parameters were expressed by electrical components. A methodology on how to determine the parameters for electrical components has been explained. It is found that by using a multimeter, forces in the connection line and the absorbed electric power can be simulated and read directly from the electric circuit model. Finally, the circuit model has been validated against the full scale offshore experiment. The results indicated that the captured power could be predicted rather accurately and the line force could be estimated accurately near the designed working condition of the WEC.
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.
Modeling and Fabrication of Micro FET Pressure Sensor with Circuits
Dai, Ching-Liang; Tai, Yao-Wei; Kao, Pin-Hsu
2007-01-01
This paper presents the simulation, fabrication and characterization of a micro FET (field effect transistor) pressure sensor with readout circuits. The pressure sensor includes 16 sensing cells in parallel. Each sensing cell that is circular shape is composed of an MOS (metal oxide semiconductor) and a suspended membrane, which the suspended membrane is the movable gate of the MOS. The CoventorWare is used to simulate the behaviors of the pressure sensor, and the HSPICE is employed to evaluate the characteristics of the circuits. The pressure sensor integrated with circuits is manufactured using the commercial 0.35 ?m CMOS (complementary metal oxide semiconductor) process and a post-process. In order to obtain the suspended membranes, the pressure sensor requires a post-CMOS process. The post-process adopts etchants to etch the sacrificial layers in the pressure sensors to release the suspended membranes, and then the etch holes in the pressure sensor are sealed by LPCVD (low pressure chemical vapor deposition) parylene. The pressure sensor produces a change in current when applying a pressure to the sensing cells. The circuits are utilized to convert the current variation of the pressure sensor into the voltage output. Experimental results show that the pressure sensor has a sensitivity of 0.032 mV/kPa in the pressure range of 0-500 kPa.
Equivalent circuit modeling of hybrid electric vehicle drive train
Routex, Jean-Yves
2001-01-01
this objective, a methodology based on electrical analogies and transducers theory is presented in this work. Using the powerful circuit theory to solve multi-disciplinary problems is not revolutionary, but applied to the design of advanced vehicles, it brings a...
Superior model for fault tolerance computation in designing nano-sized circuit systems
Singh, N. S. S. Muthuvalu, M. S.; Asirvadam, V. S.
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.
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.
SPICE equivalent circuit model of quantum-dot semiconductor optical amplifiers
NASA Astrophysics Data System (ADS)
Rostami, A.; Maram Q, R.; Baghban, H.; Rasooli S., H.; Ghorbani, R.
2009-11-01
In this paper, we derive an equivalent circuit model for quantum dot semiconductor optical amplifier (QDSOA) by employing rate equations for electronic transitions between QD's levels and also the optical power propagation. The different parts of equivalent circuits interact together to represent the gain recovery process, saturation properties and chirp behaviour in both linear and nonlinear operation regimes of QD-SOA. The equivalent circuits are then used for SPICE simulation. We have shown that SPICE simulation results agree well with the full numerically calculated results.
New equivalent-electrical circuit model and a practical measurement method for human body impedance.
Chinen, Koyu; Kinjo, Ichiko; Zamami, Aki; Irei, Kotoyo; Nagayama, Kanako
2015-01-01
Human body impedance analysis is an effective tool to extract electrical information from tissues in the human body. This paper presents a new measurement method of impedance using armpit electrode and a new equivalent circuit model for the human body. The lowest impedance was measured by using an LCR meter and six electrodes including armpit electrodes. The electrical equivalent circuit model for the cell consists of resistance R and capacitance C. The R represents electrical resistance of the liquid of the inside and outside of the cell, and the C represents high frequency conductance of the cell membrane. We propose an equivalent circuit model which consists of five parallel high frequency-passing CR circuits. The proposed equivalent circuit represents alpha distribution in the impedance measured at a lower frequency range due to ion current of the outside of the cell, and beta distribution at a high frequency range due to the cell membrane and the liquid inside cell. The calculated values by using the proposed equivalent circuit model were consistent with the measured values for the human body impedance. PMID:26406074
2.5. SUMMARY OF THE MODEL 49 Figure 2.25: Simulation of the stack circuit.
Olshausen, Bruno
2.5. SUMMARY OF THE MODEL 49 Figure 2.25: Simulation of the stack circuit. The dotted square indicates the window of attention. The circuit is shown attending to the `A' at the lowest resolution level of the stack. #12; 48 CHAPTER 2. DYNAMIC ROUTING CIRCUITS displays the state of the attended 9 ! 5 module
Modeling Quantum Noise for efficient testing of fault-tolerant circuits
NASA Astrophysics Data System (ADS)
Puzzuoli, Daniel; Magesan, Easwar; Granade, Christopher; Cory, David
2013-05-01
Experimental implementations of quantum logic gates are affected by noise. For simple noise models and encoding schemes, threshold theorems exist which place bounds on the acceptable strength of the noise. In general, finding threshold values for an encoding scheme is a difficult task. Therefore it is desirable to simulate the performance of large encoded circuits to numerically estimate threshold values. For general circuits and noise models, these simulations quickly become intractable in the size of the encoded circuit. We introduce methods for approximating a noise process by one which allows for efficient Monte Carlo simulation of properties of encoded circuits. The approximations are as close to the original process as possible without overestimating their ability to preserve quantum information, a key property for obtaining more honest estimates of threshold values.
Short-Term Plasticity in a Computational Model of the Tail-Withdrawal Circuit in Aplysia
Baxter, Douglas A.; Byrne, John H.
2007-01-01
The tail-withdrawal circuit of Aplysia provides a useful model system for investigating synaptic dynamics. Sensory neurons within the circuit manifest several forms of synaptic plasticity. Here, we developed a model of the circuit and investigated the ways in which depression (DEP) and potentiation (POT) contributed to information processing. DEP limited the amount of motor neuron activity that could be elicited by the monosynaptic pathway alone. POT within the monosynaptic pathway did not compensate for DEP. There was, however, a synergistic interaction between POT and the polysynaptic pathway. This synergism extended the dynamic range of the network, and the interplay between DEP and POT made the circuit responded preferentially to long-duration, low-frequency inputs. PMID:17957237
Short-Term Plasticity in a Computational Model of the Tail-Withdrawal Circuit in Aplysia.
Baxter, Douglas A; Byrne, John H
2007-06-01
The tail-withdrawal circuit of Aplysia provides a useful model system for investigating synaptic dynamics. Sensory neurons within the circuit manifest several forms of synaptic plasticity. Here, we developed a model of the circuit and investigated the ways in which depression (DEP) and potentiation (POT) contributed to information processing. DEP limited the amount of motor neuron activity that could be elicited by the monosynaptic pathway alone. POT within the monosynaptic pathway did not compensate for DEP. There was, however, a synergistic interaction between POT and the polysynaptic pathway. This synergism extended the dynamic range of the network, and the interplay between DEP and POT made the circuit responded preferentially to long-duration, low-frequency inputs. PMID:17957237
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.; Nebashi, R.; Sugibayashi, T.; Natsui, M.; Hanyu, T.; Ohno, H.
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.
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
Xu, Xiaolun; Li, Yongqian; Wang, Binbin; Zhou, Zili
2015-10-01
The resonance characteristics of plasmonic metamaterials absorbers (PMAs) are strongly dependent on geometric parameters. A resistor-inductor-capacitor (RLC) circuit model has been extended to predict the resonance wavelengths and the bandwidths of multiple magnetic polaritons modes in PMAs. For a typical metallic-dielectric-metallic structure absorber working in the infrared region, the developed model describes the correlation between the resonance characteristics and the dimensional sizes. In particular, the RLC model is suitable for not only the fundamental resonance mode, but also for the second- and third-order resonance modes. The prediction of the resonance characteristics agrees fairly well with those calculated by the finite-difference time-domain simulation and the experimental results. The developed RLC model enables the facilitation of designing multi-band PMAs for infrared radiation detectors and thermal emitters. PMID:26421549
Using Simple Circuits as Thermal Models for your Home
NASA Astrophysics Data System (ADS)
Poynor, Adele
2015-03-01
One of the most cost effect ways to improve the energy efficiency of your home is to increase your home's insulation. But would it be better to insulate your walls or by new windows? Not all options are equally effective, nor do they have equal costs. So how can you determine which option improves your homes insulation the most? I present an analogy to simple resistor circuits that can be used by introductory students to answer these questions.
NASA Astrophysics Data System (ADS)
Zhang, Yu; Zhao, Jiyun; Wang, Peng; Skyllas-Kazacos, Maria; Xiong, Binyu; Badrinarayanan, Rajagopalan
2015-09-01
Electrical equivalent circuit models demonstrate excellent adaptability and simplicity in predicting the electrical dynamic response of the all-vanadium redox flow battery (VRB) system. However, only a few publications that focus on this topic are available. The paper presents a comprehensive equivalent circuit model of VRB for system level analysis. The least square method is used to identify both steady-state and dynamic characteristics of VRB. The inherent features of the flow battery such as shunt current, ion diffusion and pumping energy consumption are also considered. The proposed model consists of an open-circuit voltage source, two parasitic shunt bypass circuits, a 1st order resistor-capacitor network and a hydraulic circuit model. Validated with experimental data, the proposed model demonstrates excellent accuracy. The mean-error of terminal voltage and pump consumption are 0.09 V and 0.49 W respectively. Based on the proposed model, self-discharge and system efficiency are studied. An optimal flow rate which maximizes the system efficiency is identified. Finally, the dynamic responses of the proposed VRB model under step current profiles are presented. Variables such as SOC and stack terminal voltage can be provided.
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.
NASA Astrophysics Data System (ADS)
Behr, Ernst-Karl
A model is developed for the IGBT, which can be used on components for the simulation of power electronics circuits. The use of IGBT in a typical utilization case is examined, e.g., a quick switching pulse inverter for the control of asynchronous machines. The starting point of IGBT model production is an equivalent circuit from a bipolar transistor and from a controlling field effect transistor. The stationary behavior of the bipolar transistor is described by analytically produced nonlinear equations. Available model equations are collected in a dynamic IGBT model. New and modified processes are developed, with which all relevant IGBT parameters can be obtained by electrical measurements in simple test circuits. The validity of the developed IGBT model is demonstrated, using typical load conditions, by comparison with simulation and measurement results.
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.
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.
Hosoda, M; Miyaguchi, T; Imagawa, K; Nakamura, K
2009-12-01
We investigate simple three-dimensionally crossed wires carrying electric currents which generate chaotic magnetic-field lines (CMFLs). As such wire systems, cross-ring and perturbed parallel-ring wires are studied, since topologically equivalent configurations to these systems can often be found in contemporary electric and integrated circuits. For realistic fundamental wire configurations, the conditions for wire dimensions (size) and current values to generate CMFLs are numerically explored under the presence of the weak but inevitable geomagnetic field. As a result, it is concluded that CMFLs can exist everywhere; i.e., they are ubiquitous in the modern technological world. PMID:20365304
NASA Astrophysics Data System (ADS)
Hosoda, M.; Miyaguchi, T.; Imagawa, K.; Nakamura, K.
2009-12-01
We investigate simple three-dimensionally crossed wires carrying electric currents which generate chaotic magnetic-field lines (CMFLs). As such wire systems, cross-ring and perturbed parallel-ring wires are studied, since topologically equivalent configurations to these systems can often be found in contemporary electric and integrated circuits. For realistic fundamental wire configurations, the conditions for wire dimensions (size) and current values to generate CMFLs are numerically explored under the presence of the weak but inevitable geomagnetic field. As a result, it is concluded that CMFLs can exist everywhere; i.e., they are ubiquitous in the modern technological world.
An equivalent circuit model for terahertz quantum cascade lasers: Modeling and experiments
NASA Astrophysics Data System (ADS)
Yao, Chen; Xu, Tian-Hong; Wan, Wen-Jian; Zhu, Yong-Hao; Cao, Jun-Cheng
2015-09-01
Terahertz quantum cascade lasers (THz QCLs) emitted at 4.4 THz are fabricated and characterized. An equivalent circuit model is established based on the five-level rate equations to describe their characteristics. In order to illustrate the capability of the model, the steady and dynamic performances of the fabricated THz QCLs are simulated by the model. Compared to the sophisticated numerical methods, the presented model has advantages of fast calculation and good compatibility with circuit simulation for system-level designs and optimizations. The validity of the model is verified by the experimental and numerical results. Project supported by the National Basic Research Program of China (Grant No. 2014CB339803), the National High Technology Research and Development Program of China (Grant No. 2011AA010205), the National Natural Science Foundation of China (Grant Nos. 61131006, 61321492, and 61404149), the Major National Development Project of Scientific Instrument and Equipment, China (Grant No. 2011YQ150021), the National Science and Technology Major Project, China (Grant No. 2011ZX02707), the Major Project, China (Grant No. YYYJ-1123-1), the International Collaboration and Innovation Program on High Mobility Materials Engineering of the Chinese Academy of Sciences, and the Shanghai Municipal Commission of Science and Technology, China (Grant Nos. 14530711300).
NASA Astrophysics Data System (ADS)
Maram Q, R.; Baghban, H.; Rasooli S, H.; Ghorbani, R.; Rostami, A.
2009-10-01
In this paper, we derive an equivalent circuit model for a quantum dot semiconductor optical amplifier (QD-SOA) by employing rate equations for electronic transitions between the QD's levels and also the optical power propagation. The different parts of the equivalent circuits interact together to represent the gain recovery process, saturation properties and chirp behaviour in both linear and nonlinear operation regimes of the QD-SOA. The equivalent circuits are then used for SPICE simulation. We have also applied a control pulse to decrease the gain recovery time using the cross-gain modulation (XGM) effect, and the equivalent circuit of this source has been discussed. The Tb s-1 operation capability can be illustrated using this approach. We have shown that SPICE simulation results agree well with the full numerically calculated results.
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
Subharmonic ferroresonance in an LCR circuit with hysteresis
Lamba, Harbir
Subharmonic ferroresonance in an LCR circuit with hysteresis H. LAMBA # M.GRINFELD # S.McKEE # R. SIMPSON + Abstract We use the Preisach model of magnetic hysteresis to model the inductance in a series LCR circuit. By introducing a hysteresis parameter into the Preisach functions used, we are able
Equivalent circuit-level model and improvement of terahertz quantum cascade lasers
Wei Zhou; Shaobin Liu; Jie Wu; Xiaoliu Zhang; Wu Tang
2014-04-28
An equivalent circuit-level model of terahertz (THz) quantum cascade lasers (QCLs) is developed by using rate equations. This model can be employed to investigate the characteristics of THz QCLs accurately and to improve their design. We use the circuit-level model to analyse a new active structure, which can improve the performance of THz QCLs by means of enhancing carrier injection. The simulation result shows that THz QCLs with the new active structure have a much higher performance compared with conventional THz QCLs. The high-performance THz QCLs are expected to be operated at higher temperatures. (lasers)
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.
Qiu, S. S.; Zhuang, G.; Zhang, M.; Xia, D. H.; Rao, B.; Zhang, X. Q.; Pan, Y.; Gentle, K.
2010-10-15
Four sets of magnetic diagnostic coils, which are printed on machinable ceramic printed circuit boards (PCB), are designed, fabricated, installed, and tested in the Joint Texas Experimental Tokamak (J-TEXT) vacuum vessel for detecting the plasma radial and vertical displacements relative to the geometric center of the vacuum vessel in Ohmic discharges. Each coordinate is determined by a pair of variable cross-section Rogowski and saddle coils, which measure the tangential and normal magnetic fields (relative to the coil surface). These coils are suitable for mass production and offer advantages in vacuum compatibility and temperature tolerance that are important for J-TEXT. Position measurements using PCB coils are compared with those from soft x-ray image system and match the position well.
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
NASA Technical Reports Server (NTRS)
Valentinuzzi, M.
1973-01-01
Results of a previous metric analysis and an electronic simulation of acceleratory nystagmus are given. On this basis, a tentative mathematical model for describing acceleratory nystagmus is reported. The essential content of the model is Lorente de No's neuron circuit, to which the two-factor theory of excitation has been applied.
Modeling and control of a LN2-GN2 operated closed circuit cryogenic wind tunnel
NASA Technical Reports Server (NTRS)
Balakrishna, S.; Thibodeaux, J. J.
1979-01-01
An explicit but simple lumped parameter nonlinear multivariable model of a LN2-GN2-operated closed circuit cryogenic wind tunnel has been developed and its basic features have been experimentally validated. The model describes the mass-energy interaction involved in the cryogenic tunnel process and includes the real gas properties of nitrogen gas.
Computer model for air-cooled refrigerant condensers with specified refrigerant circuiting
Ellison, R.D.; Creswick, F.A.; Fischer, S.K.; Jackson, W.L.
1981-01-01
A computer model for an air-cooled refrigerant condensor is presented; the model is intended for use in detailed design analyses or in simulation of the performance of existing heat exchangers that have complex refrigerant circuiting or unusual air-side geometries. The model relies on a tube-by-tube computational approach calculating the thermal and fluid-flow performance of each tube in the heat exchanger individually, using local temperatures and heat transfer coefficients. The refrigerant circuiting must be specified; the joining or branching of parallel circuits is accommodated using appropriate mixing expressions. Air-side heat exchange correlations may be specified so that various surface geometries can be investigated. Results of the analyses of two condensers are compared to experiment.
A circuit model for filament eruptions and two-ribbon flares
NASA Technical Reports Server (NTRS)
Martens, P. C. H.; Kuin, N. P. M.
1989-01-01
A circuit model is derived for solar filament eruptions and two-ribbon flares. In the model the filament is approximated as a line current and the current sheet as infinitely thin. The model reproduces the slow energy buildup and eruption of the filament and the energy dissipation in a current sheet at the top of postflare loops during the two-ribbon flare. The two circuits considered are that of the filament and its return current and that of the current sheet and its return current. These circuits are inductively coupled, and free energy stored in the filament in the pre-flare phase is found to be transferred to the sheet during the impulsive phase and rapidly dissipated there. In the solutions for the evolution of the filament current sheet system four phases are distinguished: (1) a slow energy buildup, (2) a 'metastable' state, (3) the eruptive phase, and (4) a postflare phase. These phases are described in detail.
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
A global magnetic topology model for magnetic clouds. III
Hidalgo, M. A.
2014-03-20
In two previous papers, we presented a global model for the analysis of magnetic clouds (MCs), where the three components of the magnetic field were fitted to the corresponding Geocentric Solar Ecliptic experimental data, obtaining reliable information, for example, about the orientation of these events in the interplanetary medium. That model, due to its non-force-free character, (?p ? 0), could be extended to determine the plasma behavior. In the present work, we develop that extension, now including the plasma behavior inside the cloud through the analysis of the plasma pressure, and define a fitting procedure where the pressure and the magnetic field components are fitted simultaneously. After deducing the magnetic field topology and the current density components of the model, we calculate the expression of the pressure tensor and, in particular, its trace. In light of the results, we conclude that incorporating the plasma behavior in the analysis of the MCs can give us a better scenario in which to understand the physical mechanisms involved in the evolution of such magnetic structures in the interplanetary medium.
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.
A GLOBAL MAGNETIC TOPOLOGY MODEL FOR MAGNETIC CLOUDS. I
Hidalgo, M. A.; Nieves-Chinchilla, T. E-mail: teresa.nieves-chinchil-1@nasa.gov
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.
Modeling spin magnetization transport in a spatially varying magnetic field
NASA Astrophysics Data System (ADS)
Picone, Rico A. R.; Garbini, Joseph L.; Sidles, John A.
2015-01-01
We present a framework for modeling the transport of any number of globally conserved quantities in any spatial configuration and apply it to obtain a model of magnetization transport for spin-systems that is valid in new regimes (including high-polarization). The framework allows an entropy function to define a model that explicitly respects the laws of thermodynamics. Three facets of the model are explored. First, it is expressed as nonlinear partial differential equations that are valid for the new regime of high dipole-energy and polarization. Second, the nonlinear model is explored in the limit of low dipole-energy (semi-linear), from which is derived a physical parameter characterizing separative magnetization transport (SMT). It is shown that the necessary and sufficient condition for SMT to occur is that the parameter is spatially inhomogeneous. Third, the high spin-temperature (linear) limit is shown to be equivalent to the model of nuclear spin transport of Genack and Redfield (1975) [1]. Differences among the three forms of the model are illustrated by numerical solution with parameters corresponding to a magnetic resonance force microscopy (MRFM) experiment (Degen et al., 2009 [2]; Kuehn et al., 2008 [3]; Sidles et al., 2003 [4]; Dougherty et al., 2000 [5]). A family of analytic, steady-state solutions to the nonlinear equation is derived and shown to be the spin-temperature analog of the Langevin paramagnetic equation and Curie's law. Finally, we analyze the separative quality of magnetization transport, and a steady-state solution for the magnetization is shown to be compatible with Fenske's separative mass transport equation (Fenske, 1932 [6]).
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
A Circuit Model for the Measurement of the Streaming Potential in a Rock Sample
NASA Astrophysics Data System (ADS)
Yin, C.; Wang, J.; Qiu, A.; Liu, X.; Hu, H.
2012-04-01
Streaming potential is usually defined under the assumption that the rock sample under consideration is not connected electrically to any external circuit. In this study we investigate experimentally the effect of the external circuit on the measurement of the streaming potential. Cations usually dominate anions in the diffuse layer in the pore canals in a fluid-saturated porous sandstone sample. When a pressure difference is applied to the sample, fluid flows in the pores and causing a convective current due to the cation-dominate motion. With the separation of opposite ions at the two ends, a streaming potential occurs, and results in a conductive current. Those two current will be opposite and equal in value so that the streaming potential does not change. But in any experimental measurement of the streaming potential, the rock sample is not isolated in the circuit. An external circuit is necessary for the measurement of the potential difference at the ends of the sample. This external circuit will divert the flow of charges. This study investigates the effect of the external circuit on the convective current and conductive current in the pores by experiments, and gives an equivalent circuit model for the two currents. We connect an external resistance Rext to the ends of the fluid-saturated rock sample, and measure the potential difference at the ends of the sample . The impedance of the fluid-saturated rock sample Zrock is definite under a given salinity and can be separately measured. The circuit is governed by the following equations, Urock = ZrockIcond, (1) Urock = RextIext, (2) Iconv + Icond +Iext = 0, (3) where Iconv is the convective current, Icond is the conductive current, Iext is the external current and Urock is the potential difference at the ends of the rock sample. From the above three equations, we get - Urock(Zrock + Rext) Iconv = ---Z--R----- . rock ext (4) We repeated the measurement under different external resistance Rext. The computed convective current changes slightly. Thus we conclude that the measurement circuit does not change the convective current, although it changes the conductive current. So the convective current behaves as a constant current source. This conclusion is in consistence with the electrokinetic model, in which the convection current is caused by the cation-dominated fluid flow under pressure difference. We notice that the measured streaming potential is smaller than that without measuring circuit connected to it, unless the external resistance Rext is orders higher than the resistance of the rock. This study is supported by project No.41174110 of the National Natural Science Foundation of China.
Information Flow through a Model of the C. elegans Klinotaxis Circuit
Izquierdo, Eduardo J.; Williams, Paul L.; Beer, Randall D.
2015-01-01
Understanding how information about external stimuli is transformed into behavior is one of the central goals of neuroscience. Here we characterize the information flow through a complete sensorimotor circuit: from stimulus, to sensory neurons, to interneurons, to motor neurons, to muscles, to motion. Specifically, we apply a recently developed framework for quantifying information flow to a previously published ensemble of models of salt klinotaxis in the nematode worm Caenorhabditis elegans. Despite large variations in the neural parameters of individual circuits, we found that the overall information flow architecture circuit is remarkably consistent across the ensemble. This suggests structural connectivity is not necessarily predictive of effective connectivity. It also suggests information flow analysis captures general principles of operation for the klinotaxis circuit. In addition, information flow analysis reveals several key principles underlying how the models operate: (1) Interneuron class AIY is responsible for integrating information about positive and negative changes in concentration, and exhibits a strong left/right information asymmetry. (2) Gap junctions play a crucial role in the transfer of information responsible for the information symmetry observed in interneuron class AIZ. (3) Neck motor neuron class SMB implements an information gating mechanism that underlies the circuit’s state-dependent response. (4) The neck carries more information about small changes in concentration than about large ones, and more information about positive changes in concentration than about negative ones. Thus, not all directions of movement are equally informative for the worm. Each of these findings corresponds to hypotheses that could potentially be tested in the worm. Knowing the results of these experiments would greatly refine our understanding of the neural circuit underlying klinotaxis. PMID:26465883
Transmission line circuit model of a PPy based trilayer mechanical sensor
NASA Astrophysics Data System (ADS)
Khalili, Nazanin; Naguib, Hani E.; Kwon, Roy H.
2015-04-01
Many efforts have been devoted to modeling the diffusive impedance of conjugated polymer (CP) based actuators using their equivalent electrical circuits. Employing the same methodology, CP based mechanical sensors can also be treated by an equivalent transmission line circuit and their overall impedance can be modeled, correspondingly. Due to the large number of resources to study the electrical circuits, this technique is a practical tool. Therefore, in this study, an equivalent RC-circuit model including electrochemical parameters is determined to obtain a better perception of the sensing mechanism of these mechanical sensors. Conjugated polymers are capable of generating an output current or voltage upon an induced mechanical deformation or force. This observed behavior in polymer based mechanical sensors is considered as the reverse actuation process. Many outstanding properties of the conjugated polymer actuators including their light weight and biocompatibility are still retained by these sensors. Sensors with a trilayer configuration are capable of operating in air in response to a mechanically induced bending deformation. However, due to their nonlinear behavior and multivariable characteristics, it is required to propose a systematic approach in order to optimize their performance and gain the optimal values of their constituent decision variable. Therefore, the proposed mathematical model is used to define the output voltage of the PPy based mechanical sensor along with the sensitivity of the model to the applied frequency of the induced deformation. Applying a multiobjective optimization algorithm, the optimization problem was solved and the tracking ability of the proposed model was then verified.
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
Superconducting solenoid model magnet test results
Carcagno, R.; Dimarco, J.; Feher, S.; Ginsburg, C.M.; Hess, C.; Kashikhin, V.V.; Orris, D.F.; Pischalnikov, Y.; Sylvester, C.; Tartaglia, M.A.; Terechkine, I.; /Fermilab
2006-08-01
Superconducting solenoid magnets suitable for the room temperature front end of the Fermilab High Intensity Neutrino Source (formerly known as Proton Driver), an 8 GeV superconducting H- linac, have been designed and fabricated at Fermilab, and tested in the Fermilab Magnet Test Facility. We report here results of studies on the first model magnets in this program, including the mechanical properties during fabrication and testing in liquid helium at 4.2 K, quench performance, and magnetic field measurements. We also describe new test facility systems and instrumentation that have been developed to accomplish these tests.
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.
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 ...
Magnetic field decay in model SSC dipoles
Gilbert, W.S.; Althaus, R.F.; Barale, P.J.; Benjegerdes, R.W.; Green, M.A.; Green, M.I.; Scanlan, R.M.
1988-08-01
We have observed that some of our model SSC dipoles have long time constant decays of the magnetic field harmonics with amplitudes large enough to result in significant beam loss, if they are not corrected. The magnets were run at constant current at the SSC injection field level of 0.3 tesla for one to three hours and changes in the magnetic field were observed. One explanation for the observed field decay is time dependent superconductor magnetization. Another explanation involves flux creep or flux flow. Data are presented on how the decay changes with previous flux history. Similar magnets with different Nb-Ti filament spacings and matrix materials have different long time field decay. A theoretical model using proximity coupling and flux creep for the observed field decay is discussed. 10 refs., 5 figs., 2 tabs.
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.
Vector spin modeling for magnetic tunnel junctions with voltage dependent effects
Manipatruni, Sasikanth Nikonov, Dmitri E.; Young, Ian A.
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.
Vector spin modeling for magnetic tunnel junctions with voltage dependent effects
NASA Astrophysics Data System (ADS)
Manipatruni, Sasikanth; Nikonov, Dmitri E.; Young, Ian A.
2014-05-01
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.
Haberl, Matthias G; Zerbi, Valerio; Veltien, Andor; Ginger, Melanie; Heerschap, Arend; Frick, Andreas
2015-11-01
Fragile X syndrome (FXS), the most common inherited form of intellectual disability disorder and a frequent cause of autism spectrum disorder (ASD), is characterized by a high prevalence of sensory symptoms. Perturbations in the anatomical connectivity of neocortical circuits resulting in their functional defects have been hypothesized to contribute to the underlying etiology of these disorders. We tested this idea by probing alterations in the functional and structural connectivity of both local and long-ranging neocortical circuits in the Fmr1 (-/y) mouse model of FXS. To achieve this, we combined in vivo ultrahigh-field diffusion tensor magnetic resonance imaging (MRI), functional MRI, and viral tracing approaches in adult mice. Our results show an anatomical hyperconnectivity phenotype for the primary visual cortex (V1), but a disproportional low connectivity of V1 with other neocortical regions. These structural data are supported by defects in the structural integrity of the subcortical white matter in the anterior and posterior forebrain. These anatomical alterations might contribute to the observed functional decoupling across neocortical regions. We therefore identify FXS as a "connectopathy," providing a translational model for understanding sensory processing defects and functional decoupling of neocortical areas in FXS and ASD. PMID:26702437
Haberl, Matthias G.; Zerbi, Valerio; Veltien, Andor; Ginger, Melanie; Heerschap, Arend; Frick, Andreas
2015-01-01
Fragile X syndrome (FXS), the most common inherited form of intellectual disability disorder and a frequent cause of autism spectrum disorder (ASD), is characterized by a high prevalence of sensory symptoms. Perturbations in the anatomical connectivity of neocortical circuits resulting in their functional defects have been hypothesized to contribute to the underlying etiology of these disorders. We tested this idea by probing alterations in the functional and structural connectivity of both local and long-ranging neocortical circuits in the Fmr1?/y mouse model of FXS. To achieve this, we combined in vivo ultrahigh-field diffusion tensor magnetic resonance imaging (MRI), functional MRI, and viral tracing approaches in adult mice. Our results show an anatomical hyperconnectivity phenotype for the primary visual cortex (V1), but a disproportional low connectivity of V1 with other neocortical regions. These structural data are supported by defects in the structural integrity of the subcortical white matter in the anterior and posterior forebrain. These anatomical alterations might contribute to the observed functional decoupling across neocortical regions. We therefore identify FXS as a “connectopathy,” providing a translational model for understanding sensory processing defects and functional decoupling of neocortical areas in FXS and ASD. PMID:26702437
Atomistic spin model simulations of magnetic nanomaterials
NASA Astrophysics Data System (ADS)
Evans, R. F. L.; Fan, W. J.; Chureemart, P.; Ostler, T. A.; Ellis, M. O. A.; Chantrell, R. W.
2014-03-01
Atomistic modelling of magnetic materials provides unprecedented detail about the underlying physical processes that govern their macroscopic properties, and allows the simulation of complex effects such as surface anisotropy, ultrafast laser-induced spin dynamics, exchange bias, and microstructural effects. Here we present the key methods used in atomistic spin models which are then applied to a range of magnetic problems. We detail the parallelization strategies used which enable the routine simulation of extended systems with full atomistic resolution.
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. There have been several approaches used to model nanoparticle magnetization dynamics for both Brownian as well as Néel rotation. The 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
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.
Surface-Charge-Based Micro-Models--A Solid Foundation for Learning about Direct Current Circuits
ERIC Educational Resources Information Center
Hirvonen, P. E.
2007-01-01
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…
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.
Mental Models of Elementary and Middle School Students in Analyzing Simple Battery and Bulb Circuits
ERIC Educational Resources Information Center
Jabot, Michael; Henry, David
2007-01-01
Written assessment items were developed to probe students' understanding of a variety of direct current (DC) resistive electric circuit concepts. The items were used to explore the mental models that grade 3-8 students use in explaining the direction of electric current and how electric current is affected by different configurations of simple…
Wood, Thomas K.
A stochastic model of Escherichia coli AI-2 quorum signal circuit reveals alternative synthesis discoveries: (1) the mRNA transcript and protein levels of AI-2 synthases, Pfs and LuxS, do not contribute accounts for this difference. We predict that `high-flux' alternative pathways or additional biological
Instituto de Sistemas e Robotica
with a visual sensory area consisting of an unknown rigid configuration of light-sensitive receptive fields that predicted sensory feedback usually integrates with effectively experienced stimuli in such a seamless manner stimuli when we move our eyes. In this work we develop an adaptive model of a corollary discharge circuit
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...
Power Magnetics Design and Measurement of Power Magnetics
. Approximate analytical models for winding loss, core loss, and thermal resistance., Co-optimize magnetics design with circuit design: Switching frequency Inductance value Magnetic component geometricPower Magnetics Design and Measurement of Power Magnetics Charles R S lli an h l lli @d t th d
Li, Dongling; Wen, Zhiyu; Wen, Zhongquan; He, Xuefeng; Yang, Yinchuan; Shang, Zhengguo
2009-01-01
A novel high-precision vacuum microelectronic accelerometer has been successfully fabricated and tested in our laboratory. This accelerometer has unique advantages of high sensitivity, fast response, and anti-radiation stability. It is a prototype intended for navigation applications and is required to feature micro-g resolution. This paper briefly describes the structure and working principle of our vacuum microelectronic accelerometer, and the mathematical model is also established. The performances of the accelerometer system are discussed after Matlab modeling. The results show that, the dynamic response of the accelerometer system is significantly improved by choosing appropriate parameters of signal detecting circuit, and the signal detecting circuit is designed. In order to attain good linearity and performance, the closed-loop control mode is adopted. Weak current detection technology is studied, and integral T-style feedback network is used in I/V conversion, which will eliminate high-frequency noise at the front of the circuit. According to the modeling parameters, the low-pass filter is designed. This circuit is simple, reliable, and has high precision. Experiments are done and the results show that the vacuum microelectronic accelerometer exhibits good linearity over -1 g to +1 g, an output sensitivity of 543 mV/g, and a nonlinearity of 0.94 %. PMID:22408515
Li, Dongling; Wen, Zhiyu; Wen, Zhongquan; He, Xuefeng; Yang, Yinchuan; Shang, Zhengguo
2009-01-01
A novel high-precision vacuum microelectronic accelerometer has been successfully fabricated and tested in our laboratory. This accelerometer has unique advantages of high sensitivity, fast response, and anti-radiation stability. It is a prototype intended for navigation applications and is required to feature micro-g resolution. This paper briefly describes the structure and working principle of our vacuum microelectronic accelerometer, and the mathematical model is also established. The performances of the accelerometer system are discussed after Matlab modeling. The results show that, the dynamic response of the accelerometer system is significantly improved by choosing appropriate parameters of signal detecting circuit, and the signal detecting circuit is designed. In order to attain good linearity and performance, the closed-loop control mode is adopted. Weak current detection technology is studied, and integral T-style feedback network is used in I/V conversion, which will eliminate high-frequency noise at the front of the circuit. According to the modeling parameters, the low-pass filter is designed. This circuit is simple, reliable, and has high precision. Experiments are done and the results show that the vacuum microelectronic accelerometer exhibits good linearity over -1 g to +1 g, an output sensitivity of 543 mV/g, and a nonlinearity of 0.94 %. PMID:22408515
An enhanced BSIM modeling framework for selfheating aware circuit design
NASA Astrophysics Data System (ADS)
Schleyer, M.; Leuschner, S.; Baumgartner, P.; Mueller, J.-E.; Klar, H.
2014-11-01
This work proposes a modeling framework to enhance the industry-standard BSIM4 MOSFET models with capabilities for coupled electro-thermal simulations. An automated simulation environment extracts thermal information from model data as provided by the semiconductor foundry. The standard BSIM4 model is enhanced with a Verilog-A based wrapper module, adding thermal nodes which can be connected to a thermal-equivalent RC network. The proposed framework allows a fully automated extraction process based on the netlist of the top-level design and the model library. A numerical analysis tool is used to control the extraction flow and to obtain all required parameters. The framework is used to model self-heating effects on a fully integrated class A/AB power amplifier (PA) designed in a standard 65 nm CMOS process. The PA is driven with +30 dBm output power, leading to an average temperature rise of approximately 40 °C over ambient temperature.
The development of a thermal analysis model builder for a printed circuit board
NASA Astrophysics Data System (ADS)
Glaser, Stephen J.
1991-09-01
The Naval Postgraduate School possesses software designed to perform thermal analysis of electronic components. At the core of this package is a model builder whose purpose is to generate a thermal model for use in steady state and transient thermal analyzers. The current version of the model builder requires excessive amounts of time for data input and model verification. This thesis describes the development of a model builder specifically designed to reduce the time required to model a printed circuit board containing up to four copper layers.
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.
Pulsed magnetic field measurement using a ferrite waveguide in a phase bridge circuit
William A Pellico and Patrick Colestock
2002-07-01
There are several standard methods used for measuring pulsed magnetic fields. However the induction or Hall probe methods have limited bandwidth and experience reflection problems. The integrated magnetic field can only be found by measuring along the entire length of the magnet. Problems with reflections, noise and bandwidth will limit the accuracy of measurement. Presented in the following paper is a method for measuring pulsed fields without the typical noise errors and bandwidth limitations. This paper will describe a phase bridge network that relies upon the permeability of a ferrite waveguide to accurately measure the integrated field of a Main Injector kicker magnet. The authors present some data taken with the system, a first pass at the analysis of this data, and discuss some possible design variations.
Yang, Zhijun; Cameron, Katherine; Lewinger, William; Webb, Barbara; Murray, Alan
2012-03-01
Animals such as stick insects can adaptively walk on complex terrains by dynamically adjusting their stepping motion patterns. Inspired by the coupled Matsuoka and resonate-and-fire neuron models, we present a nonlinear oscillation model as the neuromorphic central pattern generator (CPG) for rhythmic stepping pattern generation. This dynamic model can also be used to actuate the motoneurons on a leg joint with adjustable driving frequencies and duty cycles by changing a few of the model parameters while operating such that different stepping patterns can be generated. A novel mixed-signal integrated circuit design of this dynamic model is subsequently implemented, which, although simplified, shares the equivalent output performance in terms of the adjustable frequency and duty cycle. Three identical CPG models being used to drive three joints can make an arthropod leg of three degrees of freedom. With appropriate initial circuit parameter settings, and thus suitable phase lags among joints, the leg is expected to walk on a complex terrain with adaptive steps. The adaptation is associated with the circuit parameters mediated both by the higher level nervous system and the lower level sensory signals. The model is realized using a 0.3- complementary metal-oxide-semiconductor process and the results are reported. PMID:24808545
DC/AC unified OTFT compact modeling and circuit design for RFID applications
NASA Astrophysics Data System (ADS)
Fadlallah, M.; Billiot, G.; Eccleston, W.; Barclay, D.
2007-07-01
Organic materials and devices are gaining more and more attention in microelectronics. They are dedicated to low cost applications and easy in fabrications. Device structure and organic material characteristics are key points to achieve targeted products. Considering technology and product specifications, compact organic device modeling and circuit design are necessary to evaluate technology performance in RFID tags. This model is based on variable range hopping theory (VRH), i.e., a carrier may either hop over a small distance with a high activation energy or hop over a long distance with a low activation energy. The model has been developed using a physical basis where the model parameters can easily be extracted and it improves convergence in circuit simulations. It is also suitable for computer aided design (CAD) applications.
Circuit Models and Implementations of Electronically Tunable Reflectarray Elements
Hum, Sean Victor
the scattering response of electronically tunable re- flectarray elements. The model is used to analyze ETR- tance devices [4, 5], MEMS devices [6, 7], and exotic materials [8]. This paper presents a modeling capacitance is denoted by Cf , and the radiation resistance associated with the radiating slot by Rr. Note
Magnetic modeling of the Bushveld Igneous Complex
NASA Astrophysics Data System (ADS)
Webb, S. J.; Cole, J.; Letts, S. A.; Finn, C.; Torsvik, T. H.; Lee, M. D.
2009-12-01
Magnetic modeling of the 2.06 Ga Bushveld Complex presents special challenges due a variety of magnetic effects. These include strong remanence in the Main Zone and extremely high magnetic susceptibilities in the Upper Zone, which exhibit self-demagnetization. Recent palaeomagnetic results have resolved a long standing discrepancy between age data, which constrain the emplacement to within 1 million years, and older palaeomagnetic data which suggested ~50 million years for emplacement. The new palaeomagnetic results agree with the age data and present a single consistent pole, as opposed to a long polar wander path, for the Bushveld for all of the Zones and all of the limbs. These results also pass a fold test indicating the Bushveld Complex was emplaced horizontally lending support to arguments for connectivity. The magnetic signature of the Bushveld Complex provides an ideal mapping tool as the UZ has high susceptibility values and is well layered showing up as distinct anomalies on new high resolution magnetic data. However, this signature is similar to the highly magnetic BIFs found in the Transvaal and in the Witwatersrand Supergroups. Through careful mapping using new high resolution aeromagnetic data, we have been able to map the Bushveld UZ in complicated geological regions and identify a characteristic signature with well defined layers. The Main Zone, which has a more subdued magnetic signature, does have a strong remanent component and exhibits several magnetic reversals. The magnetic layers of the UZ contain layers of magnetitite with as much as 80-90% pure magnetite with large crystals (1-2 cm). While these layers are not strongly remanent, they have extremely high magnetic susceptibilities, and the self demagnetization effect must be taken into account when modeling these layers. Because the Bushveld Complex is so large, the geometry of the Earth’s magnetic field relative to the layers of the UZ Bushveld Complex changes orientation, creating complications in the modeling. Anisotropic magnetic susceptibility may be related to demagnetization in the Bushveld Complex due to well defined, relatively thin layers. Aeromagnetic data are useful for imaging layered intrusions because they often contain highly magnetic layers. However, care must be taken to incorporate the effects of strong susceptibilites (AMS,demagnetisation) and remanence.
NASA Astrophysics Data System (ADS)
Ito, S.; Mifune, T.; Matsuo, T.; Suzuki, M.; Kawano, K.
2014-05-01
The finite element (FE) modeling of a ferrite-core device is discussed. Measured properties of Ni-Zn ferrite ring cores show that even though the AC ferrite property is similar to that caused by the eddy-current field, the FE eddy-current analysis using an equivalent electrical conductivity cannot, in practice, represent the AC property. An equivalent-circuit model which describes AC/DC ferrite properties is applied to FE magnetic field analysis of a ferrite-core inductor. The simulated AC property with/without DC bias agrees with the measured one.
Models for Examining Impact of Cosmic Rays on Integrated Circuits
NASA Astrophysics Data System (ADS)
Atkinson, William; William J Atkinson Collaboration
2015-04-01
The Soft Error Rate (SER) produced by SEUs in microelectronic devices in near-earth orbits and in the atmosphere has been computed using a common model developed at Boeing, TSAREME. In space, TSAREME models protons, alphas, and heavy ions with atomic numbers up to 26 (iron) for GCR and peak solar flares. In the atmosphere, TSAREME computes the neutron flux fluxes produced by charged particles interacting with air molecules, accounting for magnetosphere variations with latitude. The devices include Complementary Metal on Oxide (CMOS) and Silicon on Insulator (SOI) transistors with feature sizes varying from a micron to 15 nm. Validation of model results to empirical data discussed.
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
The Circuit Theory Behind Coupled-Mode Magnetic Resonance-Based Wireless Power Transmission
Kiani, Mehdi; Ghovanloo, Maysam
2014-01-01
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
Numerical Based Linear Model for Dipole Magnets
Li,Y.; Krinsky, S.; Rehak, M.
2009-05-04
In this paper, we discuss an algorithm for constructing a numerical linear optics model for dipole magnets from a 3D field map. The difference between the numerical model and K. Brown's analytic approach is investigated and clarified. It was found that the optics distortion due to the dipoles' fringe focusing must be properly taken into account to accurately determine the chromaticities. In NSLS-II, there are normal dipoles with 35-mm gap and dipoles for infrared sources with 90-mm gap. This linear model of the dipole magnets is applied to the NSLS-II lattice design to match optics parameters between the DBA cells having dipoles with different gaps.
Modeling for infrared readout integrated circuit based on Verilog-A
NASA Astrophysics Data System (ADS)
Wang, Xiao; Shi, Zelin
2015-04-01
Infrared detectors are the core of infrared imaging systems, while readout integrated circuits are the key components of detectors. In order to grasp the performance of circuits quickly and accurately, a method of circuit modeling using Verilog-A language is proposed, which present a behavioral simulation model for the ROIC. At first, a typical capacitor trans-impedance amplifier(CTIA) ROIC unit is showed, then the two essential parts of it,operational amplifier and switch are modeled on behavioral level. The op amp model concludes these non-ideal factors, such as finite gain-bandwidth product, input and output offset, output resistance and so on. Non-deal factors that affect switches are considered in the switch behavioral model, such as rise and fall time, on-resistance and so on. At last time-domain modeling method for noise is presented, which is compared with the classical frequency domain method for difference. The analysis results shows that in the situation that noise interested bandwidth(NIBW) is more than 5MHz, the difference between the two methods leads to less than 1% if the sample rate of noise is larger 4 times of the NIBW
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.
A simple model of magnetically induced warps
E. Battaner; J. Jimenez-Vicente
1998-02-02
Assuming the magnetic hypothesis for the formation of warps, we deduce a very simple formula for the warp curve in an idealized scenario. According to this formula the warp rises as the third power of radius in the innermost warped region, reaches the maximum slope at intermediate radii and has an asymptotic slope coincident with the direction of the extragalactic magnetic field. In most cases, however, the galaxy's limited size prevents the observation of the full curve. Even though the model is highly simplified, it basically reproduces real warp curves, in particular the 21 cm warp curve of NGC 5907. If the magnetic model were considered to be correct, the fitting of warp curves could allow rough estimations of the strength and direction of the magnetic field. We also propose a magnetic field distribution for the outermost part of the galaxy, matching the boundary conditions of being azimuthal inside, and constant at infinity. We use this magnetic field distribution to show that the assumptions made to obtain the warp curve with our simple model cannot introduce important errors.
ERIC Educational Resources Information Center
Asami, Noriaki; King, Julien; Monk, Martin
2000-01-01
Focuses on the familiar problem of students' understanding of elementary electrical circuits from a much neglected point of view. Suggests that the patterning commonly found in students' ideas might have its roots in the cognitive processing with which students operate their mental models of d.c. electrical circuits. Studies Japanese 10-11 year…
Sabes, Philip
and the underlying neural circuits Philip N. Sabes Department of Physiology and Keck Center for Integrative shown how optimal integration could be instantiated in neural circuits. However, strong links have yetSensory integration for reaching: models of optimality in the context of behavior
Tentzeris, Manos
A Novel Circuit Model of Nanotechnology-Enabled Inkjet-Printed Gas Sensors Using Multi-Wall Carbon-scale nanotechnology- enabled inkjet-printed modules. Index Terms -- Gas sensing, carbon nanotube, inkjet printing, equivalent circuit, nanotechnology. I. INTRODUCTION Due to their excellent mechanical and electronic
Modeling A Grinding Circuit Using Genetic Programming Charles L. Karr
Fernandez, Thomas
60196 Abstract Accurate and efficient computer models of mineral processing systems are becoming in of grinding, one of the most prominent unit operations in the processing of minerals. 1 INTRODUCTION creasingly important as the mineral industry strives to improve the efficiency of benefici ation systems
Modeling A Grinding Circuit Using Genetic Programming Charles L. Karr
Fernandez, Thomas
60196 Abstract Accurate and e cient computer models of mineral processing systems are becoming in of grinding, one of the most prominent unit operations in the processing of minerals. 1 INTRODUCTION- creasingly important as the mineral industry strives to improve the e ciency of bene ci- ation systems
A simple model of magnetically induced warps
Battaner, E
1998-01-01
Assuming the magnetic hypothesis for the formation of warps, we deduce a very simple formula for the warp curve in an idealized scenario. According to this formula the warp rises as the third power of radius in the innermost warped region, reaches the maximum slope at intermediate radii and has an asymptotic slope coincident with the direction of the extragalactic magnetic field. In most cases, however, the galaxy's limited size prevents the observation of the full curve. Even though the model is highly simplified, it basically reproduces real warp curves, in particular the 21 cm warp curve of NGC 5907. If the magnetic model were considered to be correct, the fitting of warp curves could allow rough estimations of the strength and direction of the magnetic field. We also propose a magnetic field distribution for the outermost part of the galaxy, matching the boundary conditions of being azimuthal inside, and constant at infinity. We use this magnetic field distribution to show that the assumptions made to obt...
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.
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)
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%.
NASA Astrophysics Data System (ADS)
Zhang, Bin; Mao, Lu-hong; Li, Shanguo; Guo, Wei-lian; Zhang, Shi-lin; Liang, Hui-lai
2008-01-01
As the length scale of the devices decreases, electrons will spend increasingly more of their time in the connections between components; this interconnectivity problem could restrict further increases in computer chip processing power and speed. Considerable effort is therefore being expended on the development of efficient silicon light-emitting devices compatible with silicon based integrated circuit technology. Here, we describe the electrical and optical properties of Silicon positive intrinsic negative (pin) structure diode that operates at room temperature. The voltage-current and electroluminescence (EL) property are measured at room temperature for a silicon pin diode under forward biased current. The optical spectral response of the system at 700nm indicates that the emitting light source has low optical loss in Silicon. So the LED is suitable for Silicon optoelectronic interconnection system.[1][2] The rate-equation model for free carriers on light-emitting pin structure and the equivalent circuit model based on it have been presented. We have developed a way to calculate the model parameters by comparison with experimental results. This parameter extraction way can be fully accomplished automatically by using MATHCAD program and the equivalent circuit model is simulated by using HSPICE program respectively. The results of both experiment and simulation results are good agreement with each other.
Reconfigurable Special Test Circuit of physics-based IGBT models parameter extraction
NASA Astrophysics Data System (ADS)
Rodríguez, Marco A.; Claudio, Abraham; Cotorogea, Maria; González, Leobardo H.; Aguayo, Jesús
2010-11-01
Physics-based models of power electronic devices are the most accurate for circuit simulation purposes. However, many parameters of such models are related to device physics and structure and are not directly available for the user. The IGBT is still the most used power semiconductor device for applications at medium power and frequency ranges, due to its good compromise between on-state loss, switching loss, and ease of control. This paper presents a procedure for extracting the most important parameters of the IGBT, with physical background and electrical measurements. The goal is to develop a deeply understanding of the device-structure and to simulate correctly both steady-state and transient period with any circuit simulation software without the IGBT model provided by the manufacturer. The method consists of seven test setups and seven algorithms for extracting 13 physical and structural parameters needed in most physics-based IGBT models; by using only one Reconfigurable Special Test Circuit in order to achieve the different test setups conditions.
Dynamic instabilities in magnetically levitated models
NASA Astrophysics Data System (ADS)
Chu, Donald; Moon, Francis C.
1983-03-01
Experiments are reported demonstrating divergence and flutter instabilities in an electrodynamic maglev vehicle. The conducting guideway consists of L-shaped aluminum segments attached to a rotating wheel and qualitatively simulates the Japanese full scale guideway at Miyazaki. The model vehicle employed rare earth permanent magnets. Quantitative tests for a coupled yaw-lateral vibration show both divergence and flutter. The divergence leads to two stable equilibrium yaw positions, while the flutter instability leads to limit cycle oscillations coupling yaw and lateral motions in the neighborhood of the drag peak. A theoretical model based on actual magnetic force measurements is shown to predict this dynamic behavior as functions of vehicle speed and geometry.
Nordstrom, Eric J; Bittner, Katie C; McGrath, Michael J; Parks, Clinton R; Burton, Frank H
2015-12-10
The brain circuits underlying tics in Tourette?s syndrome (TS) are unknown but thought to involve cortico/amygdalo-striato-thalamo-cortical (CSTC) loop hyperactivity. We previously engineered a transgenic mouse "circuit model" of TS by expressing an artificial neuropotentiating transgene (encoding the cAMP-elevating, intracellular A1 subunit of cholera toxin) within a small population of dopamine D1 receptor-expressing somatosensory cortical and limbic neurons that hyperactivate cortico/amygdalostriatal glutamatergic output circuits thought to be hyperactive in TS and comorbid obsessive-compulsive (OC) disorders. As in TS, these D1CT-7 ("Ticcy") transgenic mice?s tics were alleviated by the TS drugs clonidine and dopamine D2 receptor antagonists; and their chronic glutamate-excited striatal motor output was unbalanced toward hyperactivity of the motoric direct pathway and inactivity of the cataleptic indirect pathway. Here we have examined whether these mice?s tics are countered by drugs that "break" sequential elements of their hyperactive cortical/amygdalar glutamatergic and efferent striatal circuit: anti-serotonoceptive and anti-noradrenoceptive corticostriatal glutamate output blockers (the serotonin 5-HT2a,c receptor antagonist ritanserin and the NE alpha-1 receptor antagonist prazosin); agmatinergic striatothalamic GABA output blockers (the presynaptic agmatine/imidazoline I1 receptor agonist moxonidine); and nigrostriatal dopamine output blockers (the presynaptic D2 receptor agonist bromocriptine). Each drug class alleviates tics in the Ticcy mice, suggesting a hyperglutamatergic CSTC "tic circuit" could exist in TS wherein cortical/amygdalar pyramidal projection neurons? glutamatergic overexcitation of both striatal output neurons and nigrostriatal dopaminergic modulatory neurons unbalances their circuit integration to excite striatothalamic output and create tics, and illuminating new TS drug strategies. PMID:26453289
Translating Non-Trivial Algorithms from the Circuit Model to the Measurement
Smith IV, Amos M; Alsing, Paul; Lott, Capt. Gordon; Fanto, Michael
2015-01-01
We provide a set of prescriptions for implementing a circuit model algorithm as measurement based quantum computing via a large discrete cluster state constructed sequentially, from qubits implemented as single photons. We describe a large optical discrete graph state capable of searching logical 4 and 8 element lists as an example. To do so we have developed several prescriptions based on analytic evaluation of the evolution of discrete cluster states and graph state equations. We describe the cluster state as a sequence of repeated entanglement and measurement steps using a small number of single photons for each step. These prescriptions can be generalized to implement any logical circuit model operation with appropriate single photon measurements and feed forward error corrections. Such a cluster state is not guaranteed to be optimal (i.e. minimum number of photons, measurements, run time).
Gneiding, N.; Zhuromskyy, O.; Peschel, U.; Shamonina, E.
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.
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.
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)
Rose, D. V.; Miller, C. L.; Welch, D. R.; Clark, R. E.; Madrid, E. A.; Mostrom, C. B.; Stygar, W. A.; Lechien, K. R.; Mazarakis, M. A.; Langston, W. L.; Porter, J. L.; Woodworth, J. R.
2010-09-01
A 3D fully electromagnetic (EM) model of the principal pulsed-power components of a high-current linear transformer driver (LTD) has been developed. LTD systems are a relatively new modular and compact pulsed-power technology based on high-energy density capacitors and low-inductance switches located within a linear-induction cavity. We model 1-MA, 100-kV, 100-ns rise-time LTD cavities [A. A. Kim , Phys. Rev. ST Accel. Beams 12, 050402 (2009)PRABFM1098-440210.1103/PhysRevSTAB.12.050402] which can be used to drive z-pinch and material dynamics experiments. The model simulates the generation and propagation of electromagnetic power from individual capacitors and triggered gas switches to a radially symmetric output line. Multiple cavities, combined to provide voltage addition, drive a water-filled coaxial transmission line. A 3D fully EM model of a single 1-MA 100-kV LTD cavity driving a simple resistive load is presented and compared to electrical measurements. A new model of the current loss through the ferromagnetic cores is developed for use both in circuit representations of an LTD cavity and in the 3D EM simulations. Good agreement between the measured core current, a simple circuit model, and the 3D simulation model is obtained. A 3D EM model of an idealized ten-cavity LTD accelerator is also developed. The model results demonstrate efficient voltage addition when driving a matched impedance load, in good agreement with an idealized circuit model.
MODELING OF EDDY CURRENT LOSS AND TEMPERATURE OF THE MAGNETS
Mi, Chunting "Chris"
- mium-iron-boron (NdFeB), and slot/tooth harmonics, there is eddy current loss generated inside by PWM inverter supply. Analytical methods are implemented, in conjunction with time-stepped ¯nite-element (SPMSM); interior magnet PM motors; time-stepped ¯nite-element analysis (FEA); thermal circuits
Xavier, MA; Trimboli, MS
2015-07-01
This paper introduces a novel application of model predictive control (MPC) to cell-level charging of a lithium-ion battery utilizing an equivalent circuit model of battery dynamics. The approach employs a modified form of the MPC algorithm that caters for direct feed-though signals in order to model near-instantaneous battery ohmic resistance. The implementation utilizes a 2nd-order equivalent circuit discrete-time state-space model based on actual cell parameters; the control methodology is used to compute a fast charging profile that respects input, output, and state constraints. Results show that MPC is well-suited to the dynamics of the battery control problem and further suggest significant performance improvements might be achieved by extending the result to electrochemical models. (C) 2015 Elsevier B.V. All rights reserved.
NASA Astrophysics Data System (ADS)
Xavier, Marcelo A.; Trimboli, M. Scott
2015-07-01
This paper introduces a novel application of model predictive control (MPC) to cell-level charging of a lithium-ion battery utilizing an equivalent circuit model of battery dynamics. The approach employs a modified form of the MPC algorithm that caters for direct feed-though signals in order to model near-instantaneous battery ohmic resistance. The implementation utilizes a 2nd-order equivalent circuit discrete-time state-space model based on actual cell parameters; the control methodology is used to compute a fast charging profile that respects input, output, and state constraints. Results show that MPC is well-suited to the dynamics of the battery control problem and further suggest significant performance improvements might be achieved by extending the result to electrochemical models.
Modeling Solar Magnetic Fields Using Satellite Data
NASA Astrophysics Data System (ADS)
Lee, G.; Malanushenko, A. V.; DeRosa, M. L.
2014-12-01
Previous research reconstructed a three-dimensional model of the magnetic field of an active region on the Sun from using solar coronal loops as guides for modeling(Malanushenko et al., ApJ,2009, 707:1044). In this study, we test the consistency of such reconstructions with data from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) by applying the aformentioned method to additional active regions with varying amounts of solar activity. To create an initial model of a magnetic field surrounding an active region, we first manually trace the coronal loops on the coronal images in the following wavelengths: 171Å, 193Å, 211Å, 94Å, 131Å, and 335Å. The manually traced loops are then used as a guide for a computer reconstruction of the individual three-dimensional field lines with differing heights and degrees of local twist. The reconstructed field lines are then adjusted by a partially automated algorithm, so that the constructed field line would correspond to a coronal loop on the Sun. These fitted loops serve as a skeleton to create a model of the magnetic field of the active region. We expect that our modeling can be used in future works to predict future solar events. Implications of this ability include being able to prepare a response for a solar event before it happens.
Magnetic models on various topologies
NASA Astrophysics Data System (ADS)
Lima, F. W. S.; Plascak, J. A.
2014-03-01
A brief review is given on the study of the thermodynamic properties of spin models defined on different topologies like small-world, scale-free networks, random graphs and regular and random lattices. Ising, Potts and Blume-Capel models are considered. They are defined on complex lattices comprising Appolonian, Barabási-Albert, Voronoi-Delauny and small-world networks. The main emphasis is given on the corresponding phase transitions, transition temperatures, critical exponents and universality, compared to those obtained by the same models on regular Bravais lattices.
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
An equivalent circuit model of supercapacitors for applications in wireless sensor networks
NASA Astrophysics Data System (ADS)
Yang, Hengzhao; Zhang, Ying
2011-04-01
Energy harvesting technologies have been extensively researched to develop long-lived wireless sensor networks. To better utilize the harvested energy, various energy storage systems are proposed. A simple circuit model is developed to describe supercapacitor behavior, which uses two resistor-capacitor branches with different time constants to characterize the charging and redistribution processes, and a variable leakage resistance (VLR) to characterize the self-discharge process. The voltage and temperature dependence of the VLR values is also discussed. Results show that the VLR model is more accurate than the energy recursive equation (ERE) models for short term wireless sensor network applications.
Electrical Circuit Simulation Code
Energy Science and Technology Software Center (ESTSC)
2001-08-09
Massively-Parallel Electrical Circuit Simulation Code. CHILESPICE is a massively-arallel distributed-memory electrical circuit simulation tool that contains many enhanced radiation, time-based, and thermal features and models. Large scale electronic circuit simulation. Shared memory, parallel processing, enhance convergence. Sandia specific device models.
You, Xiao-Mang; Nasrallah, Fadi; Darling, Edward; Robins, Mike; Nieman, Gary; Searles, Bruce
2005-01-01
Abstract: A clinically relevant rat cardiopulmonary bypass (CPB) model would be a valuable tool for investigating pathophysiological and therapeutic strategies on bypass. Previous rat CPB models have been described in the literature; however, they have many limitations, including large circuit surface area, the inability to achieve full bypass, and donor blood requirements for prime. Therefore, we have established a rat CPB model designed to overcome these limitations. The miniature circuit consisted of a filtered reservoir, heat exchanger, membrane oxygenator (surface area = 0.02 m2) with a static priming volume of 2.8 mL, and an inline blood gas monitor. The circuit was primed with 9.5 ± 0.5 mL of crystalloid solution and CPB was established on male Sprague–Dawley rats (430–475 g, n = 5) by cannulating the left common carotid artery and the right external jugular vein. The animals were placed on CPB at full flow (111 ± 13 mL/kg/min) for 1 hour and were monitored for and additional 2 hours after the CPB procedure. Hemodynamics, hemoglobin concentration (Hb), and blood gases were analyzed at three time intervals: before, during, and after CPB. The circuit performance was evaluated according to prime volume, compliance, hemodynamic parameters, and gas and heat exchange as described by modified AMMI standards. Data are expressed as mean ± SD and a repeated-measures analysis of variance with post-Hoc test was used for data comparison between the three time intervals. The ratio of oxygenator surface area to subject body weight for this model is comparable with that of current human adult CPB practice (0.05 m2/kg vs 0.057 m2/kg) Full CPB was achieved and we observed clinically acceptable PaO2, PaCO2, and SvO2 values (209 ± 86 mmHg, 25 ± 2 mmHg, 78 ± 8%, respectively) while on CPB. The use of asanguinous prime did produce statistically significant Hg reduction (15.7 ± 0.76 vs. 9.2 ± 0.59 g/dL) comparable with clinical practice. No statistically significant differences between pre-and post-CPB hemodynamics and blood gases were found in our study. We have established a miniature circuit consisting of asanquineous prime for a rat CPB model that maintains clinically acceptable results regarding hemodynamic parameters, blood gases, and hemodilution. This model would be valuable for further use in clinically relevant research studies. PMID:15804160
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…
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.
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.
Modeling Magnetic Structures in the Inner Heliosphere
NASA Astrophysics Data System (ADS)
Odstrcil, D.; Bourdelle, A.; Kunkel, V.; Rouillard, A. P.; Vandas, M.
2014-12-01
Currently, the WSA-ENLIL-Cone modeling system is used by various space weather agencies for operational forecasting of corotating and transient solar wind disturbances in the inner heliosphere. This modeling system provides global context and arrival times of the solar wind streams and coronal mass ejections (CMEs) to Earth, planets, and spacecraft. Such predictions are running continuously and much faster than real time. However, CME-like disturbances are generated by launching hydrodynamic transients and thus it is not possible to predict the southward magnetic field (-Bz). In this presentation, we use 3-D analytic models of spheromaks and flux ropes, launch them into the background solar wind at 0.1 AU and simulate their evolution in the inner heliosphere. We discuss differences between these two models and effects of the background magnetic field on their propagation and distortion.
DeGeorge, V; Shen, S; Ohodnicki, P; Andio, M; Mchenry, ME
2013-12-05
New power conversion systems that offer promise to transform electricity grids into unified interactive supply networks require high-resistivity soft-magnetic materials to allow for switching of magnetic materials at frequencies approaching 100 kHz for power transformation in the megawatt range. Amorphous and nanocomposite soft-magnetic materials, which represent the state of the art in terms of high power densities and low losses at high frequencies, have resistivities that depend on the structures and spatial distributions of multiple phases in thin ribbons. We present a multiphase resistivity model applicable to nanocomposite materials by considering an equivalent circuit approach considering paths through an amorphous, crystalline, and growth inhibitor shell phase. We detail: (a) identification of amorphous, crystalline, and shell phases; (b) consideration of the role of the morphology of each phase in an equivalent circuit model for the resistance; (c) a two-band model for the Fe/Co composition dependence of the resistivity in crystalline and amorphous phases; (d) a virtual bound state model for resistivity to explain increased resistivity due to early transition-metal growth inhibitors in the shell surrounding the nanocrystalline phase; and (e) disorder effects on amorphous phase resistivity. Experimental design and results for systems of interest in high-frequency power transformation are discussed in the context of our model including: (a) techniques for measurements of cross-section and density, (b) four-point probe and surface resistivity measurements, and (c) measurements in Fe- and Co-rich systems comparing amorphous and nanocomposite materials.
Weltmann, K.D.; Deutsch, H.; Unger, H.
1995-12-31
The behaviour of gas discharges can be modelled by equivalent circuits built on the basis of a theoretical description of the plasma. We report about a method which allows to develop linear and nonlinear equivalent circuits directly from the balance equations of the column plasma. All linear circuits which have been found by this algorithm are similar to derived ones of the positive column with two inertial factors (delayed effects) for a neon gas discharge. But it is the first time that nonlinear equivalent circuits could be developed directly from a set of balance equations describing the linear and nonlinear column behaviour over a wide parameter range. The investigations of the circuit behaviour lead to detailed information about the microphysical processes determining the plasma behaviour (e.g. collision rates, diffusion terms{hor_ellipsis}).
Supercapacitor equivalent electrical circuit model based on charges redistribution by diffusion
NASA Astrophysics Data System (ADS)
Sedlakova, Vlasta; Sikula, Josef; Majzner, Jiri; Sedlak, Petr; Kuparowitz, Tomas; Buergler, Brandon; Vasina, Petr
2015-07-01
A new method for the determination of parameters for an equivalent electrical circuit model of supercapacitors is proposed. The method is based on the evaluation of the time dependence of voltage measured on the supercapacitor terminals after its charging by a defined current pulse. The measured time dependence of the voltage is fitted by an exponential function, where the exponent is proportional to the square root of time. This term reflects the redistribution of charges by diffusion inside the supercapacitor structure. The equivalent electrical circuit of supercapacitors is described by five parameters - two capacitors and three resistors. One capacitor corresponds to the Helmholtz capacitance, which is charged immediately with the time constant in the order of hundreds milliseconds, while the second one represents the diffuse capacitance, which is charged with the time constant in the order of hundreds seconds. The two resistors in the equivalent circuit model represent the equivalent series resistance and the leakage resistance, respectively, while the third resistor describes the resistance for charge diffusion in the supercapacitor structure. This resistance is time dependent and a way for calculating its value is demonstrated.
An equivalent circuit model and power calculations for the APS SPX crab cavities.
Berenc, T. )
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.
Analysis and modelling of GaN Schottky-based circuits at millimeter wavelengths
NASA Astrophysics Data System (ADS)
Pardo, D.; Grajal, J.
2015-11-01
This work presents an analysis of the capabilities of GaN Schottky diodes for frequency multipliers and mixers at millimeter wavelengths. By using a Monte Carlo (MC) model of the diode coupled to a harmonic balance technique, the electrical and noise performances of these circuits are investigated. Despite the lower electron mobility of GaN compared to GaAs, multipliers based on GaN Schottky diodes can be competitive in the first stages of multiplier chains, due to the excellent power handling capabilities of this material. The performance of these circuits can be improved by taking advantage of the lateral Schottky diode structures based on AlGaN/GaN HEMT technology.
Quark matter under strong magnetic fields in chiral models
Rabhi, Aziz; Providencia, Constanca
2011-05-15
The chiral model is used to describe quark matter under strong magnetic fields and is compared to other models, the MIT bag model and the two-flavor Nambu-Jona-Lasinio model. The effect of vacuum corrections due to the magnetic field is discussed. It is shown that if the magnetic-field vacuum corrections are not taken into account explicitly, the parameters of the models should be fitted to low-density meson properties in the presence of the magnetic field.
All spin logic: Modeling multi-magnet networks interacting via spin currents
NASA Astrophysics Data System (ADS)
Srinivasan, Srikant
The increasing level of power dissipation in today's transistors, due to their continued downscaling, has led to an interest in alternatives to charge-based electronics for information processing. All-spin logic (ASL) represents one such new approach where the roles of charges and capacitors in CMOS are now played by spins and magnets. Available experiments utilizing this principle show operating voltages of the order of few tens of milli-volts, far below today's transistors. However, before an alternative logic scheme — like ASL — can be employed to build logic circuits, certain characteristics have to first be exhibited at the device level such as directionality of information transfer, implementing universal logic gates, cascading and fan-out. In order to devise and analyze ASL based strategies that can incorporate these device characteristics, this report first introduces a novel 4-component Spin-Circuit formalism, which is then coupled to an existing model for magnetization dynamics. This coupled model can simultaneously describe two distinct physical phenomena: (1) spin torque switching of magnets and (2) generation and transport of non-collinear spin currents in spin diffusive channels. The model is first benchmarked against available experimental data and is then used to provide key insights at the ASL device level, such as how to incorporate inbuilt directionality of information transfer and to propose scaling laws. Towards the end of this report, the model is extended to simulate multi-magnet ASL networks interacting via spin currents. In particular, examples of an ASL ring oscillator and a universal NAND gate are presented, which form the basis for designing large scale ASL circuits.
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.
Magnetic Testing, and Modeling, Simulation and Analysis for Space Applications
NASA Technical Reports Server (NTRS)
Boghosian, Mary; Narvaez, Pablo; Herman, Ray
2012-01-01
The Aerospace Corporation (Aerospace) and Lockheed Martin Space Systems (LMSS) participated with Jet Propulsion Laboratory (JPL) in the implementation of a magnetic cleanliness program of the NASA/JPL JUNO mission. The magnetic cleanliness program was applied from early flight system development up through system level environmental testing. The JUNO magnetic cleanliness program required setting-up a specialized magnetic test facility at Lockheed Martin Space Systems for testing the flight system and a testing program with facility for testing system parts and subsystems at JPL. The magnetic modeling, simulation and analysis capability was set up and performed by Aerospace to provide qualitative and quantitative magnetic assessments of the magnetic parts, components, and subsystems prior to or in lieu of magnetic tests. Because of the sensitive nature of the fields and particles scientific measurements being conducted by the JUNO space mission to Jupiter, the imposition of stringent magnetic control specifications required a magnetic control program to ensure that the spacecraft's science magnetometers and plasma wave search coil were not magnetically contaminated by flight system magnetic interferences. With Aerospace's magnetic modeling, simulation and analysis and JPL's system modeling and testing approach, and LMSS's test support, the project achieved a cost effective approach to achieving a magnetically clean spacecraft. This paper presents lessons learned from the JUNO magnetic testing approach and Aerospace's modeling, simulation and analysis activities used to solve problems such as remnant magnetization, performance of hard and soft magnetic materials within the targeted space system in applied external magnetic fields.
Dynamo Models for Saturn's Axisymmetric Magnetic Field
NASA Astrophysics Data System (ADS)
Stanley, S.; Tajdaran, K.
2012-12-01
Magnetic field measurements by the Cassini mission have confirmed the earlier Pioneer 11 and Voyager missions' results that Saturn's observed magnetic field is extremely axisymmetric . For example, Saturn's dipole tilt is less than 0.06 degrees (Cao et al., 2011) . The nearly-perfect axisymmetry of Saturn's dipole is troubling because of Cowling's Theorem which states that an axisymmetric magnetic field cannot be maintained by a dynamo. However, Cowling's Theorem applies to the magnetic field generated inside the dynamo source region and we can avert any contradiction with Cowling's Theorem if we can find reason for a non-axisymmetric field generated inside the dynamo region to have an axisymmetrized potential field observed at satellite altitude. Stevenson (1980) proposed a mechanism for this axisymmetrization. He suggested that differential rotation in a stably-stratified electrically conducting layer (i.e. the helium rain-out layer) surrounding the dynamo could act to shear out the non-axisymmetry and hence produce an axisymmetric observed magnetic field. In previous work, we used three-dimensional self-consistent numerical dynamo models to demonstrate that a thin helium rain-out layer can produce a more axisymmetrized field (Stanley, 2010). We also found that the direction of the zonal flows in the layer is a crucial factor for magnetic field axisymmetry. Here we investigate the influence of the thickness of the helium rain-out layer and the intensity of the thermal winds on the axisymmetrization of the field. We search for optimal regions in parameter space for producing axisymmetric magnetic fields with similar spectral properties to the observed Saturnian field.
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.
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
A model for the magnetic cores of linear induction accelerator cells
Melton, J.G.; Rose, E.A.
1995-08-01
Linear induction cells are used in the electron beam accelerator for the proposed Dual Axis Radiographic Hydrotest (DARHT) facility that would be built at Los Alamos National Laboratory. Ferrite cores are used in each cell to produce 250 kV, flat to within {plus_minus}1% for 70 ns. In the course of operating a prototype test stand for the full accelerator, circuit models have been developed for the pulsed power system and the induction cells that have been useful in achieving the {plus_minus}1% flatness requirement. The circuit models use the MicroCap IV{trademark} electronic circuit analysis program, which includes a Jiles-Atherton model for magnetic materials. In addition, the coaxial, ferrite-filled geometry of the cell is modelled by a multiple-section lumped-element transmission line. Propagation of a voltage pulse through the ferrite cores, including saturation effects, can be reproduced. The model has been compared to actual waveforms obtained from prototype operations, and good results have been obtained for a wide range of operating conditions. Interest in possible future applications have led the authors to use the model to predict the behavior of accelerator cells driven by multiple voltage pulses without an intervening magnetic reset of the ferrite cores. Results show that multiple pulses can be applied to the accelerator cells without a magnetic reset, but with some degradation of later pulses. The degradation appears as a droop on the flat portion of the second (and subsequent) pulses. The droop can be corrected by shaping the waveform of the incident pulses.
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
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.
Constraining the galactic magnetic field models
NASA Astrophysics Data System (ADS)
Keivani, Azadeh
2012-03-01
Ultra-high energy cosmic rays (UHECRs) are deflected by the Galactic magnetic field (GMF) on their way to Earth. If UHECR properties were well-understood, it would be straightforward to model the intervening GMF. However uncertainties on the composition and source distribution complicate the issue. An independent method of constraining GMF models is using Faraday rotation measurements (RMs) of Galactic and extra-Galactic radio sources. Here we investigate a new composite method for constraining GMF models using simultaneous fits of UHECR and RM simulations. A simulated universe of UHECRs and Galactic RMs are used to test this method.
Qiu, Longqing; Zhang, Yi; Krause, Hans-Joachim; Braginski, Alex I; Usoskin, Alexander
2007-05-01
Certain applications of superconducting quantum interference devices (SQUIDs) require a magnetic field measurement only in a very narrow frequency range. In order to selectively improve the alternating-current (ac) magnetic field sensitivity of a high-temperature superconductor SQUID for a distinct frequency, a single-coil LC resonant circuit has been used. Within the liquid nitrogen bath, the coil surrounds the SQUID and couples to it inductively. Copper coils with different numbers of windings were used to cover the frequency range from <1 to nearly 100 kHz. A superconducting coil made of YBa(2)Cu(3)O(7-delta) tape conductor was also tested. With the LC circuit, the signal-to-noise ratio of measurements could be improved typically by one order of magnitude or more in a narrow frequency band around the resonance frequency exceeding a few kilohertz. The best attained equivalent magnetic field resolution was 2.5 fT/radicalHz at 88 kHz. The experimental findings are in good agreement with mathematical analysis of the circuit with copper coil. PMID:17552846
NASA Astrophysics Data System (ADS)
Gao, Peng; Zhang, Cuifen; Wen, Guangwu
2015-10-01
Lithium metal electrode is pretreated with 1,3-dioxolane or 1,4-dioxane to improve its properties. The components and morphology of the surface films formed in the above two pretreatment liquids are studied using FTIR and SEM respectively. Li-LiCoO2 coin cells are then fabricated and their cycle and discharge performance are tested. It is found that the battery performance is greatly improved by such pretreatment. Interestingly, the 1,4-dioxane pretreatment is more effective than 1,3-dioxolane in improving the lithium metal electrode performance. To explore the mechanism(s) behind, the electrochemical impedance spectroscopy (EIS) is employed and an equivalent circuit model is designed for EIS analysis. The fitting curves are aligned well with the experimental curves, suggesting that the proposed equivalent circuit model is an ideal model for lithium battery. Next, the corresponding relationship between the impedance components and every individual semicircle in the Nyquist curves is inferred theoretically and the result is satisfying. Based on the analysis using this model, we conclude that the structural stability of SEI film is increased and the interfacial compatibility between the lithium substrate and the SEI film is improved by 1,3-dioxolane or 1,4-dioxane pretreatment.
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.
Landau Fluid Models for Magnetized Plasmas
Sulem, P. L.; Passot, T.; Marradi, L.
2008-10-15
A Landau fluid model for a magnetized plasma, that retains a linear description of low-frequency kinetic effects involving transverse scales significantly smaller than the ion Larmor radius, is discussed and validated in the context of nonlinear wave dynamics. Preliminary simulations of the turbulent regime are presented in one space dimension, as a first step towards more realistic three-dimensional computations, aimed to analyze the combined effect of dispersion and collisionless dissipation on the energy cascade.
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
Characterization and Modeling of 4H-SiC Lateral MOSFETs for Integrated Circuit Design
Mudholkar, M; Mantooth, HA
2013-06-01
A new process in 4H-SiC is developed that features n-type buried and inversion channel lateral MOSFETs that are fabricated with several different channel lengths (2-8 mu m) and widths (8-32 mu m) and characterized over a wide temperature range (25 degrees C-225 degrees C). It is shown that the on-resistance of enhancement-mode SiC MOSFETs reduces with temperature despite a reduction in inversion mobility because of the interaction of interface states with temperature. To enable integrated circuit development using the developed MOSFETs, their electrical characteristics are modeled over geometry and temperature using the industry standard PSP MOSFET model. A new mathematical formulation to describe the presence of the interface states is also developed and implemented in the PSP model, and excellent agreement is shown between measurement and simulation using the modified PSP model.
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
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.
Using IPS Magnetic Modeling to Determine Bz
NASA Astrophysics Data System (ADS)
Jackson, B. V.; Yu, H. S.; Hick, P. P.; Buffington, A.; Mejia-Ambriz, J. C.; Bisi, M. M.; Tokumaru, M.
2014-12-01
Interplanetary scintillation (IPS) observations enable remote determinations of velocity and density in the inner heliosphere while also providing forecasts of these quantities. Using the global velocities inferred from IPS, and through convection upward of magnetic fields perpendicular to a source surface produced by the Current-Sheet Source Surface (CSSS) modified potential model (Zhao and Hoeksema, J. Geophys. Res., 100, 19, 1995), global long-duration radial and tangential heliospheric field components can also be determined. In order to better include short-term transient effects and derive a value for the field normal to these components (Bn) during periods where CMEs, are present, we have tested an extension to our current 3D vector-field analysis. This extension adds closed fields from below the source surface to the CSSS model values, and when traced outward from the sub-Earth point, three magnetic field components are present. These are compared to in-situ magnetic fields measured near Earth for several periods throughout the current solar cycle from the minimum between Solar Cycle 23 and 24 up until the present. We find a significant positive correlation when using this extension to current analyses including that of the Bn field for the test cases analyzed thus far.
Evolutionary Models of Cold, Magnetized, Interstellar Clouds
NASA Technical Reports Server (NTRS)
Gammie, Charles F.; Ostriker, Eve; Stone, James M.
2004-01-01
We modeled the long-term and small-scale evolution of molecular clouds using direct 2D and 3D magnetohydrodynamic (MHD) simulations. This work followed up on previous research by our group under auspices of the ATP in which we studied the energetics of turbulent, magnetized clouds and their internal structure on intermediate scales. Our new work focused on both global and smallscale aspects of the evolution of turbulent, magnetized clouds, and in particular studied the response of turbulent proto-cloud material to passage through the Galactic spiral potential, and the dynamical collapse of turbulent, magnetized (supercritical) clouds into fragments to initiate the formation of a stellar cluster. Technical advances under this program include developing an adaptive-mesh MHD code as a successor to ZEUS (ATHENA) in order to follow cloud fragmentation, developing a shearing-sheet MHD code which includes self-gravity and externally-imposed gravity to follow the evolution of clouds in the Galactic potential, and developing radiative transfer models to evaluate the internal ionization of clumpy clouds exposed to external photoionizing UV and CR radiation. Gammie's work at UIUC focused on the radiative transfer aspects of this program.
MHD modeling of magnetized target fusion experiments.
Sheehey, P. T.; Faehl, Rickey J.; Kirkpatrick, R. C.; Lindemuth, I. R.
2001-01-01
Magnetized Target Fusion (MTF) is an alternate approach to controlled fusion in which a dense (0(1017-'8 cm-')), preheated (O(200 ev)), and magnetized (0( 100 kG)) target plasma is hydrodynamically compressed by an imploding liner. If electron thermal conduction losses are magnetically suppressed, relatively slow O(1 cm/microsecond) 'liner-on-plasma' compressions may be practical, using liners driven by inexpensive electrical pulsed power. Target plasmas need to remain relatively free of potentially cooling contaminants during formation and compression. Magnetohydrodynamic (MHD) calculations including detailed effects of radiation, heat conduction, and resistive field diffusion have been used to model separate target plasma (Russian MAGO, Field Reversed Configuration at Los Alamos National Laboratory) and liner implosion experiments (without plasma fill), such as recently performed at the Air Force Research Laboratory (Albuquerque). Using several different codes, proposed experiments in which such liners are used to compress such target plasmas are now being modeled in one and two dimensions. In this way, it is possible to begin to investigate important issues for the design of such proposed liner-on-plasma fusion experiments. The competing processes of implosion, heating, mixing, and cooling will determine the potential for such MTF experiments to achieve fusion conditions.
NASA Astrophysics Data System (ADS)
Lee, Hongseok; Mo, Young Kyu; Kang, Jong O.; Bang, Seungmin; Kim, Junil; Lee, Onyou; Kang, Hyoungku; Hong, Jonggi; Choi, Sukjin; Hong, In Seok; Nam, Seokho; Ahn, Min Chul
2015-10-01
A linear accelerator, called RAON, is being developed as a part of the Rare Isotope Science Project (RISP) at the Institute for Basic Science (IBS). The linear accelerator utilizes an electron cyclotron resonance (ECR) ion source for providing intense highly-charged ion beams to the linear accelerator. The 28-GHz ECR ion source can extract heavy-ion beams from protons to uranium. The superconducting magnet system for the 28-GHz ECR ion source is composed of hexapole coils and four solenoid coils made with low-Tc superconducting wires of NbTi. An electromagnetic force acts on the superconducting magnets due to the magnetic field and flowing current in the case of not only the normal state but also the quench state. In the case of quench on hexapole coils, an unbalanced flowing current among the hexapole coils is generated and causes an unbalanced electromagnetic force. Coil motions and coil strains in the quench state are larger than those in the normal state due to the unbalanced electromagnetic force among hexapole coils. Therefore, an analysis of the electromagnetic characteristics of the superconducting magnet for the 28-GHz ECR ion source on series resistance of the protection circuit in the case of quench should be conducted. In this paper, an analysis of electromagnetic characteristics of Superconducting hexapole coils for the 28-GHz ECR ion source according to the series resistance of the protection circuit in the case of quench performed by using finite-elements-method (FEM) simulations is reported.
Magnetic Reconnection Models of Prominence Formation
NASA Astrophysics Data System (ADS)
Welsch, B. T.; DeVore, C. R.; Antiochos, S. K.
2005-12-01
To investigate the hypothesis that prominences form by magnetic reconnection between initially distinct flux systems in the solar corona, we simulate coronal magnetic field evolution when two flux systems are driven together by boundary motions. In particular, we focus on configurations similar to those in the quiescent prominence formation model of Martens & Zwaan. We find that reconnection proceeds very weakly, if at all, in configurations driven with global shear flows (i.e., differential rotation); reconnection proceeds much more efficiently in similar configurations that are driven to collide directly, with converging motions along the neutral line that lead to flux cancellation; reconnected fields from this process can exhibit sheared, dipped field lines along the neutral line, consistent with prominence observations. Our field configurations do not possess the ``breakout'' topology, and eruptions are not observed, even though a substantial amount of flux is canceled in some runs.
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.
Generalized Volterra Series model for highly nonlinear optical interconnects, circuits and devices
Yücetürk, Emel
2007-01-01
AC coupled circuits that do not have usable DC response, it is Gain Low-pass system spectrum Gain Band-AC coupled front-end circuits. By introducing the concept of a virtual DC characteristic for pass-band
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 ...
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.
Charge balance and ionospheric potential dynamics in time dependent global electric circuit model
NASA Astrophysics Data System (ADS)
Jansky, J.; Pasko, V. P.
2014-12-01
We have developed a time-dependent model of global electric circuit (GEC)in spherical coordinates. The model solves time-dependent charge continuity equation coupledwith Poisson's equation. An implicit time stepping is used to avoid strict dielectricrelaxation time step condition, and boundary conditions for Poisson's equationare implemented to allow accurate description of time evolution of the ionospheric potential.The concept of impulse response of GEC is introduced that allows effective representationof complex time dynamics of various physical quantities in the circuit usingmodel results obtained for instantaneous deposition of a point charge.The more complex problems, like continuous charging of thunderstorms and different typesof lightning dischargesare then reconstructed using convolution and linearity principles.It is shown that for a thundercloud charging phase, typicallyrepresented by a current dipole, the ionospheric potential can be determined from the differenceof time integrals of two ionospheric potential impulse responsescorresponding to charge locations at the opposite ends of the current dipole.During a cloud to ground lightning discharge,the ionospheric potential changes instantaneously by a value proportionalto the charge moment change produced by lightning and then relaxes to zero.We will also discuss processes involving transient conductivity perturbations in GEC associated withextraterrestrial gamma ray bursts and sprites.
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.
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.
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.
Observations and models of magnetic reconnection
NASA Astrophysics Data System (ADS)
Barta, Miroslav
2015-08-01
Magnetic reconnection is now almost unanimously considered to be a key plasma process for energy release in solar and stellar flares. Recent decade have seen rapid development in the theory, simulations and searching for observational evidences of magnetic reconnection being in action in the core of flares. Modern modeling approach involves many realistic aspects of magnetic reconnection such as intrinsically 3D nature of the process and, namely, its highly dynamic character connected with violent formation of plasmoids at many scales. The cascade of plasmoid formation represents natural process of fast, turbulent energy transfer to the kinetic dissipation scale. This concept, revealed by numerical simulations, has found its ground in the theory of (ideal) plasmoid instability in current layers with high aspect ratio. The plasmoid dominated reconnection regime is capable to account for many puzzling dilemmas in the flare physics ranging from the observation-demanded energy release rate vs. standard reconnection-regime timescales, observed organized large-scale structures vs. signatures of fragmented energy release etc. The talk aims at reviewing recent theoretical and simulation development in this direction and observational support for the concept of plasmoid-driven reconnection cascade namely in solar flares.
A system model for closed-circuit inhalation anesthesia. I. Computer study.
Lerou, J G; Dirksen, R; Beneken Kolmer, H H; Booij, L H
1991-08-01
Developing a custom computer program to simulate the uptake, distribution, and elimination of inhalational anesthetics allows the anesthesiologist to address specific problems, but extensive skills are required to translate the involved processes first into a set of mathematical equations and then into a satisfactory computer program. The first step is often facilitated by solutions offered in the literature. The second step demands computer proficiency that is often not available, but this problem can be obviated by means of a special-purpose simulation language (SPSL). We therefore constructed a model for closed-circuit inhalation anesthesia with the aid of the block-structured SPSL TUTSIM. Noticeable differences with previous models are that the linear, 14-compartment basic model does not assume a constant alveolar concentration and mimics circulation times through the use of blood pools. Advanced features of the SPSL were used to develop variants of the basic model to simulate feedback-controlled isoflurane administration, nitrous oxide uptake, and the impact of a nonlinearity by incorporating the effect of enflurane on cardiac output. Two variants were concatenated to form a multiple model showing the concentration and second-gas effects. The model was capable of reproducing the anesthetic uptake from previous experimental studies for nitrous oxide. After its validation for other anesthetic agents, the model can be used for clinical, teaching, and research purposes. The SPSL freed the authors from the problems associated with computer programming and allowed them to concentrate on the structure of the model. PMID:1859022
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.
Partial Element Equivalent Circuit (PEEC) models for on-chip passives and interconnects
Eindhoven, Technische Universiteit
of the electric field integral equation, which can be used to construct a full-wave electromagnetic model of the different methods is given. A popular EM simulation method is the Finite-Difference Time-Domain (FDTD in the time-domain using a finite-difference scheme for the electric and magnetic fields. The disadvantage
Ferrohydrodynamic modeling of magnetic nanoparticle harmonic spectra for magnetic particle imaging
NASA Astrophysics Data System (ADS)
Dhavalikar, Rohan; Maldonado-Camargo, Lorena; Garraud, Nicolas; Rinaldi, Carlos
2015-11-01
Magnetic Particle Imaging (MPI) is an emerging imaging technique that uses magnetic nanoparticles as tracers. In order to analyze the quality of nanoparticles developed for MPI, a Magnetic Particle Spectrometer (MPS) is often employed. In this paper, we describe results for predictions of the nanoparticle harmonic spectra obtained in a MPS using three models: the first uses the Langevin function, which does not take into account finite magnetic relaxation; the second model uses the magnetization equation by Shliomis (Sh), which takes into account finite magnetic relaxation using a constant characteristic time scale; and the third model uses the magnetization equation derived by Martsenyuk, Raikher, and Shliomis (MRSh), which takes into account the effect of magnetic field magnitude on the magnetic relaxation time. We make comparisons between these models and with experiments in order to illustrate the effects of field-dependent relaxation in the MPS. The models results suggest that finite relaxation results in a significant drop in signal intensity (magnitude of individual harmonics) and in faster spectral decay. Interestingly, when field dependence of the magnetic relaxation time was taken into account, through the MRSh model, the simulations predict a significant improvement in the performance of the nanoparticles, as compared to the performance predicted by the Sh equation. The comparison between the predictions from models and experimental measurements showed excellent qualitative as well as quantitative agreement up to the 19th harmonic using the Sh and MRSh equations, highlighting the potential of ferrohydrodynamic modeling in MPI.
Magnetic field contribution to the Lorentz model.
Oughstun, Kurt E; Albanese, Richard A
2006-07-01
The classical Lorentz model of dielectric dispersion is based on the microscopic Lorentz force relation and Newton's second law of motion for an ensemble of harmonically bound electrons. The magnetic field contribution in the Lorentz force relation is neglected because it is typically small in comparison with the electric field contribution. Inclusion of this term leads to a microscopic polarization density that contains both perpendicular and parallel components relative to the plane wave propagation vector. The modified parallel and perpendicular polarizabilities are both nonlinear in the local electric field strength. PMID:16783441
Circuit model for the inverse Z-pinch wire array switch.
Waisman, Eduardo Mario; Cuneo, Michael Edward; Harvey-Thompson, A.; Lebedev, Sergey V.
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.
NASA Astrophysics Data System (ADS)
Sugioka, Hideyuki
2015-10-01
Transient space charge phenomena at high step voltages are interesting since they play a central role in many exotic nonequilibrium phenomena of ion dynamics in an electrolyte. However, the fundamental equations [i.e., the nonsteady Poisson-Nernst-Planck (PNP) equations] have not been solved analytically at high applied voltages because of their large nonlinearity. In this study, on the basis of the steady PNP solution, we propose an electrical circuit model that considers transient space charge effects and find that the dc and ac responses of the total charge of the electrical double layer are in fairly good agreement with the numerical results even at large applied voltages. Furthermore, on the basis of this model, we find approximate analytical solutions for the nonsteady PNP equations that are in good agreement with the numerical solutions of the concentration, charge density, and potential distribution at high applied voltages at each time in a surface region.
NASA Astrophysics Data System (ADS)
Qian, Li-Bo; Zhu, Zhang-Ming; Xia, Yin-Shui; Ding, Rui-Xue; Yang, Yin-Tang
2014-03-01
Through-silicon-via (TSV) to TSV crosstalk noise is one of the key factors affecting the signal integrity of three-dimensional integrated circuits (3D ICs). Based on the frequency dependent equivalent electrical parameters for the TSV channel, an analytical crosstalk noise model is established to capture the TSV induced crosstalk noise. The impact of various design parameters including insulation dielectric, via pitch, via height, silicon conductivity, and terminal impedance on the crosstalk noise is analyzed with the proposed model. Two approaches are proposed to alleviate the TSV noise, namely, driver sizing and via shielding, and the SPICE results show 241 mV and 379 mV reductions in the peak noise voltage, respectively.
Modeling electrical response of polymer-coated SAW resonators by equivalent circuit representation.
Kshetrimayum, Roshan; Yadava, R D S; Tandon, R P
2011-07-01
The paper presents an equivalent circuit model of the polymer coated surface acoustic wave (SAW) resonators by combining coupling-of-mode (COM) description of SAW resonators and perturbation calculation of SAW propagation under polymer loading. An expression for the motional load produced by polymer coating is deduced in terms of COM parameters and polymer characteristics. In addition, expressions for the shifts in resonance frequency and attenuation due to polymer loading are obtained. Simulation results are presented for one-port and two-port resonator devices coated with viscoelastic thin polymer film. The influence of polymer film on resonator response is studied with regard to variations in film thickness and shear modulus. The model simplifies understanding of polymer-coated SAW sensors. PMID:21236460
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
Terry, Bryan; Gunst, Gordy; Melchior, Richard; Wolfe, David; Feocco, Nancy; Graham, Susan; Searles, Bruce; Darling, Edward
2005-01-01
Abstract: In the United States, standardization of neonatal extracorporeal membrane oxygenation (ECMO) circuit was achieved during the 1980s. Since that time, the consoles and components of the ECMO circuit have remained fundamentally unchanged (bladder, rollerpump, silicone membrane oxygenator). Extracorporeal technology, however, has witnessed many significant advancements in components during the past two decades. These new technologies have characteristics that may improve outcomes when applied in the ECMO arena. Understanding how these technologies perform in long-term applications is necessary. Therefore, the purpose of this project is to evaluate the performance of a miniature ECMO circuit consisting of current generation technologies in an animal model. An ECMO circuit (prime volume 145 mL) was designed that included a hollow fiber oxygenator and a remote mounted centrifugal pump. All circuit tubing and components were surface coated. Three sheep (approx 13 kg) were placed on ECMO using standard neck cannulation techniques and maintained according to clinical protocols. Technical implementation, oxygenator function, and hematological parameters were accessed. Duration of ECMO was 20, 48, and 58 hours. There was no evidence of oxygenator failure, as measured by pressure drop and oxygen transfer, in any of the procedures. No plasma leak was observed in any oxygenators. Platelet count trended downward after 24 hours. Visual inspection after ECMO showed very little evidence of gross thrombosis. This ECMO circuit design departs dramatically from the typical North American systems. The use of this console and components facilitated a 70% reduction in priming volume over a traditional ECMO circuit. Further investigations should be conducted to determine if circuit miniaturization can reduce the morbidity associated with blood product consumption and the bloods contact with the artificial surfaces of the ECMO circuitry. PMID:16350388
Statistical method for estimation of the predictive power of a gene circuit model.
Myasnikova, Ekaterina; Kozlov, Konstantin N
2014-04-01
In this paper, a specific aspect of the prediction problem is considered: high predictive power is understood as a possibility to reproduce correct behavior of model solutions at predefined values of a subset of parameters. The problem is discussed in the context of a specific mathematical model, the gene circuit model for segmentation gap gene system in early Drosophila development. A shortcoming of the model is that it cannot be used for predicting the system behavior in mutants when fitted to wild type (WT) data. In order to answer a question whether experimental data contain enough information for the correct prediction we introduce two measures of predictive power. The first measure reveals the biologically substantiated low sensitivity of the model to parameters that are responsible for correct reconstruction of expression patterns in mutants, while the second one takes into account their correlation with the other parameters. It is demonstrated that the model solution, obtained by fitting to gene expression data in WT and Kr? mutants simultaneously, and exhibiting the high predictive power, is characterized by much higher values of both measures than those fitted to WT data alone. This result leads us to the conclusion that information contained in WT data is insufficient to reliably estimate the large number of model parameters and provide predictions of mutants. PMID:24712529
Effects of rest time on discharge response and equivalent circuit model for a lead-acid battery
NASA Astrophysics Data System (ADS)
Devarakonda, Lalitha; Hu, Tingshu
2015-05-01
This work carries out a detailed investigation on the effects of rest time on the discharge response and the parameters of the Thevenin's equivalent circuit model for a lead acid battery. Traditional methods for battery modeling require a long rest time before a discharging test so that a steady state is reached for the open circuit voltage. In a recent work, we developed an algebraic method for parameter identification of circuit models for batteries by applying discharging tests after variable and possibly very short rest time. This new method opens a door to the understanding of the effects of rest time on battery behavior, which may be used for better simulation, analysis and design of battery powered systems for improved battery efficiency and state of health. As we used the new method to extract circuit parameters after different rest times, we observed some unexpected results on the relationship between the rest time and circuit parameters. The initial voltages on the capacitors can be negative and becomes more negative as the rest time is increased. We also observed that the time constants increase with rest time. Relationships between rest time and other parameters are also reported in this paper.
Magnetic Actuator Modelling for Rotating Machinery Analysis
NASA Astrophysics Data System (ADS)
Mendes, Ricardo Ugliara; de Castro, Hélio Fiori; Cavalca, Kátia Lucchesi; Ferreira, Luiz Otávio Saraiva
Rotating machines have a wide range of application such as airplanes, factories, laboratories and power plants. Lately, with computer aid design, shafts finite element models including bearings, discs, seals and couplings have been developed, allowing the prediction of the machine behavior. In order to keep confidence during operation, it is necessary to monitor these systems, trying to predict future failures. One of the most applied technique for this purpose is the modal analysis. It consists of applying a perturbation force into the system and then to measure its response. However, there is a difficulty that brings limitations to the excitation of systems with rotating shafts when using impact hammers or shakers, once due to friction, undesired tangential forces and noise can be present in the measurements. Therefore, the study of a non-contact technique of external excitation becomes of high interest. In this sense, the present work deals with the study and development of a finite element model for rotating machines using a magnetic actuator as an external excitation source. This work also brings numerical simulations where the magnetic actuator was used to obtain the frequency response function of the rotating system.
Brittle superconducting magnets: an equivilent strain model
Barzi, E.; 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.
Modeling and design of a vibration energy harvester using the magnetic shape memory effect
NASA Astrophysics Data System (ADS)
Saren, A.; Musiienko, D.; Smith, A. R.; Tellinen, J.; Ullakko, K.
2015-09-01
In this study, a vibration energy harvester is investigated which uses a Ni-Mn-Ga sample that is mechanically strained between 130 and 300 Hz while in a constant biasing magnetic field. The crystallographic reorientation of the sample during mechanical actuation changes its magnetic properties due to the magnetic shape memory (MSM) effect. This leads to an oscillation of the magnetic flux in the yoke which generates electrical energy by inducing an alternating current within the pick-up coils. A power of 69.5 mW (with a corresponding power density of 1.37 mW mm-3 compared to the active volume of the MSM element) at 195 Hz was obtained by optimizing the biasing magnetic field, electrical resistance and electrical resonance. The optimization of the electrical resonance increased the energy generated by nearly a factor of four when compared to a circuit with no resonance. These results are strongly supported by a theoretical model and simulation which gives corresponding values with an error of approximately 20% of the experimental data. This model will be used in the design of future MSM energy harvesters and their optimization for specific frequencies and power outputs.
Quasilinear transport modelling at low magnetic shear
Citrin, J.; Hogeweij, G. M. D.; Bourdelle, C.; Cottier, P.; Escande, D. F.; Guercan, Oe. D.; Hatch, D. R.; Jenko, F.; Pueschel, M. J.
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.
NASA Astrophysics Data System (ADS)
Sharma, Shashi; Katiyar, V. K.; Singh, Uaday
2015-04-01
A mathematical model is developed to describe the trajectories of a cluster of magnetic nanoparticles in a blood vessel for the application of magnetic drug targeting (MDT). The magnetic nanoparticles are injected into a blood vessel upstream from a malignant tissue and are captured at the tumour site with help of an applied magnetic field. The applied field is produced by a rare earth cylindrical magnet positioned outside the body. All forces expected to significantly affect the transport of nanoparticles were incorporated, including magnetization force, drag force and buoyancy force. The results show that particles are slow down and captured under the influence of magnetic force, which is responsible to attract the magnetic particles towards the magnet. It is optimized that all particles are captured either before or at the centre of the magnet (z?0) when blood vessel is very close proximity to the magnet (d=2.5 cm). However, as the distance between blood vessel and magnet (d) increases (above 4.5 cm), the magnetic nanoparticles particles become free and they flow away down the blood vessel. Further, the present model results are validated by the simulations performed using the finite element based COMSOL software.
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
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.
Modeling of magnetization curves for computer-aided design
Abuelma'atti, M.T. )
1993-03-01
A simple algorithm is presented for obtaining the coefficients of the sine-series function for modeling the magnetization curves of magnetic materials. The algorithm, which can represent the fine details of the magnetization curve, can be easily implemented in mainframe computers and scientific programmable calculators, and can yield the coefficients of sine-series functions with any number of terms.
Implementation and Model Verification of a Magnetic Levitation System
Maggiore, Manfredi
Implementation and Model Verification of a Magnetic Levitation System Robert Brydon Owen levitation system employing one permanent magnet linear synchronous motor, and the experi- mental validation. The paper concludes with a description of future extensions to the magnetic levitation implementation. II
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.
Hippocampal circuit dysfunction in the Tc1 mouse model of Down syndrome.
Witton, Jonathan; Padmashri, Ragunathan; Zinyuk, Larissa E; Popov, Victor I; Kraev, Igor; Line, Samantha J; Jensen, Thomas P; Tedoldi, Angelo; Cummings, Damian M; Tybulewicz, Victor L J; Fisher, Elizabeth M C; Bannerman, David M; Randall, Andrew D; Brown, Jonathan T; Edwards, Frances A; Rusakov, Dmitri A; Stewart, Michael G; Jones, Matt W
2015-09-01
Hippocampal pathology is likely to contribute to cognitive disability in Down syndrome, yet the neural network basis of this pathology and its contributions to different facets of cognitive impairment remain unclear. Here we report dysfunctional connectivity between dentate gyrus and CA3 networks in the transchromosomic Tc1 mouse model of Down syndrome, demonstrating that ultrastructural abnormalities and impaired short-term plasticity at dentate gyrus-CA3 excitatory synapses culminate in impaired coding of new spatial information in CA3 and CA1 and disrupted behavior in vivo. These results highlight the vulnerability of dentate gyrus-CA3 networks to aberrant human chromosome 21 gene expression and delineate hippocampal circuit abnormalities likely to contribute to distinct cognitive phenotypes in Down syndrome. PMID:26237367
Feedback and sensitivity in an electrical circuit: An analog for climate models
Schwartz, S.E.
2010-07-27
Earth's climate sensitivity is often interpreted in terms of feedbacks that can alter the sensitivity from that of a no-feedback Stefan-Boltzmann radiator, with the feedback concept and algebra introduced by analogy to the use of this concept in the electronics literature. This analogy is quite valuable in interpreting the sensitivity of the climate system, but usage of this algebra and terminology in the climate literature is often inconsistent, with resultant potential for confusion and loss of physical insight. Here a simple and readily understood electrical resistance circuit is examined in terms of feedback theory to introduce and define the terminology that is used to quantify feedbacks. This formalism is applied to the feedbacks in an energy-balance model of Earth's climate and used to interpret the magnitude of feedback in the climate system that corresponds to present estimates of Earth's climate sensitivity.
Quasi-static Model of Magnetically Collimated Jets and Radio Lobes. II. Jet Structure and Stability
NASA Astrophysics Data System (ADS)
Colgate, Stirling A.; Fowler, T. Kenneth; Li, Hui; Bickford Hooper, E.; McClenaghan, Joseph; Lin, Zhihong
2015-11-01
This is the second in a series of companion papers showing that when an efficient dynamo can be maintained by accretion disks around supermassive black holes in active galactic nuclei, it can lead to the formation of a powerful, magnetically driven, and mediated helix that could explain both the observed radio jet/lobe structures and ultimately the enormous power inferred from the observed ultrahigh-energy cosmic rays. In the first paper, we showed self-consistently that minimizing viscous dissipation in the disk naturally leads to jets of maximum power with boundary conditions known to yield jets as a low-density, magnetically collimated tower, consistent with observational constraints of wire-like currents at distances far from the black hole. In this paper we show that these magnetic towers remain collimated as they grow in length at nonrelativistic velocities. Differences with relativistic jet models are explained by three-dimensional magnetic structures derived from a detailed examination of stability properties of the tower model, including a broad diffuse pinch with current profiles predicted by a detailed jet solution outside the collimated central column treated as an electric circuit. We justify our model in part by the derived jet dimensions in reasonable agreement with observations. Using these jet properties, we also discuss the implications for relativistic particle acceleration in nonrelativistically moving jets. The appendices justify the low jet densities yielding our results and speculate how to reconcile our nonrelativistic treatment with general relativistic MHD simulations.
Coronal magnetic field modeling using stereoscopy constraints
NASA Astrophysics Data System (ADS)
Chifu, I.; Inhester, B.; Wiegelmann, T.
2015-05-01
Aims: Nonlinear force-free field (NLFFF) extrapolation has been used extensively in the past to extrapolate solar surface magnetograms to stationary coronal field models. In theoretical tests with known boundary conditions, the nonlinear boundary value problem can be solved reliably. However, if the magnetogram is measured with errors, the extrapolation often yields field lines that disagree with the shapes of simultaneously observed and stereoscopically reconstructed coronal loops. We here propose an extension to an NLFFF extrapolation scheme that remedies this deficiency in that it incorporates the loop information in the extrapolation procedure. Methods: We extended the variational formulation of the NLFFF optimization code by an additional term that monitors and minimizes the difference of the local magnetic field direction and the orientation of 3D plasma loops. We tested the performance of the new code with a previously reported semi-analytical force-free solution. Results: We demonstrate that there is a range of force-free and divergence-free solutions that comply with the boundary measurements within some error bound. With our new approach we can obtain the solution out of this set the coronal fields which is well aligned with given loops. Conclusions: We conclude that the shape of coronal loops reconstructed by stereoscopy may lead to an important stabilization of coronal NLFFF field solutions when, as is typically the case, magnetic surface measurements with limited precision do not allow determining the solution solely from photospheric field measurements.
Vianco, P.T.; Erickson, K.L.; Hopkins, P.L.
1997-12-31
A mathematical model was developed to quantitatively describe the intermetallic compound (IMC) layer growth that takes place between a Sn-based solder and a noble metal thick film conductor material used in hybrid microcircuit (HMC) assemblies. The model combined the reaction kinetics of the solder/substrate interaction, as determined from ancillary isothermal aging experiments, with a 2-D finite element mesh that took account of the porous morphology of the thick film coating. The effect of the porous morphology on the IMC layer growth when compared to the traditional 1-D computations was significant. The previous 1-D calculations under-predicted the nominal IMC layer thickness relative to the 2-D case. The 2-D model showed greater substrate consumption by IMC growth and lesser solder consumption that was determined with the 1-D computation. The new 2-D model allows the design engineer to better predict circuit aging and hence, the reliability of HMC hardware that is placed in the field.
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.
Comments on Magnetic Reconnection Models of Canceling Magnetic Features on the Sun
NASA Astrophysics Data System (ADS)
Litvinenko, Yuri E.
2015-06-01
Data analysis and theoretical arguments support magnetic reconnection in a chromospheric current sheet as the mechanism of the observed photospheric magnetic flux cancellation on the Sun. Flux pile-up reconnection in a Sweet-Parker current sheet can explain the observed properties of canceling mag-netic features, including the speeds of canceling magnetic fragments, the magnetic uxes in the fragments, and the flux cancellation rates, inferred from the data. It is discussed how more realistic chromospheric reconnection models can be developed by relaxing the assumptions of a negligible current sheet curvature and a constant height of the reconnection site above the photosphere.
ERIC Educational Resources Information Center
Balta, Nuri
2015-01-01
Visualizing physical concepts through models is an essential method in many sciences. While students are mostly proficient in handling mathematical aspects of problems, they frequently lack the ability to visualize and interpret abstract physical concepts in a meaningful way. In this paper, initially the electric circuits and related concepts were…
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.
YI, YM; Hu, Chia-Ren.
1992-01-01
circuit we mean a circuit made of many one-dimensional superconducting wire segments, all of equal length a and cross-sectional area ?the lateral di- mensions of the wires are assumed to be small compared with the temperature-dependent Ginzburg...-Landau coherence length g(T) of the superconducting material used to make the wire segments. These wire segments should be arranged in horizontal east-west, horizontal north-south, and vertical directions ?all of which will be called links ?joined at many nodes...
NASA Technical Reports Server (NTRS)
Perez, Reinaldo J.
2011-01-01
Single Event Transients in analog and digital electronics from space generated high energetic nuclear particles can disrupt either temporarily and sometimes permanently the functionality and performance of electronics in space vehicles. This work first provides some insights into the modeling of SET in electronic circuits that can be used in SPICE-like simulators. The work is then directed to present methodologies, one of which was developed by this author, for the assessment of SET at different levels of integration in electronics, from the circuit level to the subsystem level.
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
Guo, Xinjie; Merrikh-Bayat, Farnood; Gao, Ligang; Hoskins, Brian D.; Alibart, Fabien; Linares-Barranco, Bernabe; Theogarajan, Luke; Teuscher, Christof; Strukov, Dmitri B.
2015-01-01
The purpose of this work was to demonstrate the feasibility of building recurrent artificial neural networks with hybrid complementary metal oxide semiconductor (CMOS)/memristor circuits. To do so, we modeled a Hopfield network implementing an analog-to-digital converter (ADC) with up to 8 bits of precision. Major shortcomings affecting the ADC's precision, such as the non-ideal behavior of CMOS circuitry and the specific limitations of memristors, were investigated and an effective solution was proposed, capitalizing on the in-field programmability of memristors. The theoretical work was validated experimentally by demonstrating the successful operation of a 4-bit ADC circuit implemented with discrete Pt/TiO2?x/Pt memristors and CMOS integrated circuit components.
Modeling superconductor degradation using magnetic levitation
Sriram, M.A.; Ponce, L.; Murr, L.E. . Department of Metallurgical and Materials Engineering)
1991-03-18
Corrosion of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} pellets has been studied using magnetic levitation. Pellets compressed at green compaction pressures of 120--200 MPa were exposed to water and air and the levitation heights were measured over a period of more than a month. A model based on diffusion as a rate-controlling step has been proposed. Levitation height normalized with respect to the initial levitation height was used as the modeling parameter. The experiments indicate that the normalized levitation height decreased with time up to a certain level called the saturation leviation, beyond which there is no change in the levitation height. Samples in air degraded faster than samples in water. The initial period of degradation before saturation fits the proposed model well and therefore appears to be diffusion controlled. The saturation levitation shows a dependence on the green compaction pressure. It has been proposed that corrosion (degrading reactions) is due to open porosities which are closed by the reaction products, thus causing a saturation in the levitation height dependent on the porosities.
NASA Technical Reports Server (NTRS)
Matsumoto, Raymond T. (Inventor); Higashi, Stanley T. (Inventor)
1976-01-01
A driver circuit which has low power requirements, a relatively small number of components and provides flexibility in output voltage setting. The driver circuit comprises, essentially, two portions which are selectively activated by the application of input signals. The output signal is determined by which of the two circuit portions is activated. While each of the two circuit portions operates in a manner similar to silicon controlled rectifiers (SCR), the circuit portions are on only when an input signal is supplied thereto.
Meechan, Daniel W; Maynard, Thomas M; Tucker, Eric S; Fernandez, Alejandra; Karpinski, Beverly A; Rothblat, Lawrence A; LaMantia, Anthony-S
2015-07-01
Understanding the developmental etiology of autistic spectrum disorders, attention deficit/hyperactivity disorder and schizophrenia remains a major challenge for establishing new diagnostic and therapeutic approaches to these common, difficult-to-treat diseases that compromise neural circuits in the cerebral cortex. One aspect of this challenge is the breadth and overlap of ASD, ADHD, and SCZ deficits; another is the complexity of mutations associated with each, and a third is the difficulty of analyzing disrupted development in at-risk or affected human fetuses. The identification of distinct genetic syndromes that include behavioral deficits similar to those in ASD, ADHC and SCZ provides a critical starting point for meeting this challenge. We summarize clinical and behavioral impairments in children and adults with one such genetic syndrome, the 22q11.2 Deletion Syndrome, routinely called 22q11DS, caused by micro-deletions of between 1.5 and 3.0 MB on human chromosome 22. Among many syndromic features, including cardiovascular and craniofacial anomalies, 22q11DS patients have a high incidence of brain structural, functional, and behavioral deficits that reflect cerebral cortical dysfunction and fall within the spectrum that defines ASD, ADHD, and SCZ. We show that developmental pathogenesis underlying this apparent genetic "model" syndrome in patients can be defined and analyzed mechanistically using genomically accurate mouse models of the deletion that causes 22q11DS. We conclude that "modeling a model", in this case 22q11DS as a model for idiopathic ASD, ADHD and SCZ, as well as other behavioral disorders like anxiety frequently seen in 22q11DS patients, in genetically engineered mice provides a foundation for understanding the causes and improving diagnosis and therapy for these disorders of cortical circuit development. PMID:25866365
Charge balance and ionospheric potential dynamics in time-dependent global electric circuit model
NASA Astrophysics Data System (ADS)
Jánský, Jaroslav; Pasko, Victor P.
2014-12-01
We have developed a time-dependent model of global electric circuit (GEC) in spherical coordinates. The model solves time-dependent charge continuity equation coupled with Poisson's equation. An implicit time stepping is used to avoid a strict dielectric relaxation time step condition, and boundary conditions for Poisson's equation are implemented to allow accurate description of time evolution of the ionospheric potential. The concept of impulse response of GEC is introduced that allows effective representation of complex time dynamics of various physical quantities in the circuit using model results obtained for instantaneous deposition of a point charge. The more complex problems are then reconstructed using convolution and linearity principles. For a point charge instantaneously deposited at a typical thundercloud altitude the impulse response of the charge density shows induction of the same value and polarity charge at the ionospheric boundary, while charge of the same value but opposite sign is moving down logarithmically with time and neutralizes the source point charge on time scale corresponding to the dielectric relaxation time at altitude of the source point charge. The ionospheric potential is modified immediately with input of the source point charge based on free space solution of Poisson's equation. Then the ionospheric potential relaxes. It is shown that during formation of two main charge centers of the thundercloud, typically represented by a current dipole, the ionospheric potential can be determined from the difference of time integrals of two ionospheric potential impulse responses corresponding to charge locations at the opposite ends of the current dipole. For latitude- and longitude-independent conductivity model, the total charge on the Earth is exactly zero at all times. During cloud-to-ground lightning discharge, the ionospheric potential changes instantaneously by a value proportional to the charge moment change produced by lightning and then relaxes to zero. For a typical charge moment change of 35Ckm and lightning frequency 10s-1, the ionospheric potential changes by 9.3kV; this value agrees well with the results presented by Rycroft et al. and Rycroft and Odzimek.
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.
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.
Gao, Yujie; Li, Xingang; Ding, Hui
2015-08-01
A layer model was established to elucidate the mechanism of zinc removal from the metallic mixture of waste printed circuit boards by vacuum distillation. The removal process was optimized by response surface methodology, and the optimum operating conditions were the chamber pressure of 0.1Pa, heating temperature of 923K, heating time of 60.0min, particle size of 70 mesh (0.212mm) and initial mass of 5.25g. Evaporation efficiency of zinc, the response variable, was 99.79%, which indicates that the zinc can be efficiently removed. Based on the experimental results, a mathematical model, which bears on layer structure, evaporation, mass transfer and condensation, interprets the mechanism of the variable effects. Especially, in order to reveal blocking effect on the zinc removal, the Blake-Kozeny-Burke-Plummer equation was introduced into the mass transfer process. The layer model can be applied to a wider range of metal removal by vacuum distillation. PMID:25957936
Bujdoso, Nora; Davis, Seth J.
2013-01-01
The Arabidopsis thaliana circadian clock is an interconnected network highly tractable to systems approaches. Most elements in the transcriptional–translational oscillator were identified by genetic means and the expression of clock genes in various mutants led to the founding hypothesis of a positive–negative feedback loop being the core clock. The identification of additional clock genes beyond those defined in the core led to the use of systems approaches to decipher this angiosperm oscillator circuit. Kinetic modeling was first used to explain periodicity effects of various circadian mutants. This conformed in a flexible way to experimental details. Such observations allowed a recursive use of hypothesis generating from modeling, followed by experimental corroboration. More recently, the biochemical finding of new description of a DNA-binding activity for one class of clock components directed improvements in feature generation, one of which revealed that the core of the oscillator is a negative–negative feedback loop. The recursive use of modeling and experimental validation has thus revealed many essential transcriptional components that drive negative arms in the circadian oscillator. What awaits is to more fully describe the positive arms and an understanding of how additional pathways converge on the clock. PMID:23355842
Fear signaling in the prelimbic-amygdala circuit: a computational modeling and recording study
Pendyam, Sandeep; Bravo-Rivera, Christian; Burgos-Robles, Anthony; Sotres-Bayon, Francisco; Quirk, Gregory J.
2013-01-01
The acquisition and expression of conditioned fear depends on prefrontal-amygdala circuits. Auditory fear conditioning increases the tone responses of lateral amygdala neurons, but the increase is transient, lasting only a few hundred milliseconds after tone onset. It was recently reported that that the prelimbic (PL) prefrontal cortex transforms transient lateral amygdala input into a sustained PL output, which could drive fear responses via projections to the lateral division of basal amygdala (BL). To explore the possible mechanisms involved in this transformation, we developed a large-scale biophysical model of the BL-PL network, consisting of 850 conductance-based Hodgkin-Huxley-type cells, calcium-based learning, and neuromodulator effects. The model predicts that sustained firing in PL can be derived from BL-induced release of dopamine and norepinephrine that is maintained by PL-BL interconnections. These predictions were confirmed with physiological recordings from PL neurons during fear conditioning with the selective ?-blocker propranolol and by inactivation of BL with muscimol. Our model suggests that PL has a higher bandwidth than BL, due to PL's decreased internal inhibition and lower spiking thresholds. It also suggests that variations in specific microcircuits in the PL-BL interconnection can have a significant impact on the expression of fear, possibly explaining individual variability in fear responses. The human homolog of PL could thus be an effective target for anxiety disorders. PMID:23699055
A Coupled StructuralMagnetic Strain Model for Magnetostrictive Transducers
with the elastic response of the transducer materials as they vibrate, is modeled through force balancing whichA Coupled StructuralMagnetic Strain Model for Magnetostrictive Transducers Marcelo J. Dapino the magnetic hysteresis and the strains output by a prototypical transducer. Keywords: Magnetostriction
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.
1993-01-01
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.
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.
NASA Technical Reports Server (NTRS)
Pickett, H. M.; Farhoomand, J.; Chiou, A. E.
1984-01-01
Inductive mesh transmission has been measured for the two major polarizations as a function of incidence angle. The experimental data agree well with Chen's (1970) waveguide theory in the thin mesh limit. As an aid in making more rapid predictions of mesh properties, Chen's theory is used to derive an empirical lumped circuit model. This model matches the theory and experiment to one percent over critical areas of transmission.
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.
Kim, Young-Do; Lee, Hyo-Chang; Chung, Chin-Wook
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.
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
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.
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
Magnetic field measurements of 1.5 meter model SSC collider dipole magnets at Fermilab
Lamm, M.J.; Bleadon, M.; Coulter, K.J.; Delchamps, S.; Hanft, R.; Jaffery, T.S.; Kinney, W.; Koska, W.; Ozelis, J.P.; Strait, J.; Wake, M.; DiMarco, J.
1991-09-01
Magnetic field measurements have been performed at Fermilab on 1.5 m magnetic length model dipoles for the Superconducting Supercollider. Harmonic measurements are recorded at room temperature before and after the collared coil is assembled into the yoke and at liquid helium temperature. Measurements are made as a function of longitudinal position and excitation current. High field data are compared with room temperature measurements of both the collared coil and the completed yoked magnet and with the predicted fields for both the body of the magnet and the coil ends.
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.
Kim, Sang-Gook
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 ...
Rescue of long-range circuit dysfunction in Alzheimer's disease models.
Busche, Marc Aurel; Kekuš, Maja; Adelsberger, Helmuth; Noda, Takahiro; Förstl, Hans; Nelken, Israel; Konnerth, Arthur
2015-11-01
Alzheimer's disease (AD) is associated with defects of synaptic connectivity. Such defects may not be restricted to local neuronal interactions but may extend to long-range brain activities, such as slow-wave oscillations that are particularly prominent during non-rapid eye movement (non-REM) sleep and are important for integration of information across distant brain regions involved in memory consolidation. There is increasing evidence that sleep is often impaired in AD, but it is unclear whether this impairment is directly related to amyloid-? (A?) pathology. Here we demonstrate that slow-wave activity is severely altered in the neocortex, thalamus and hippocampus in mouse models of AD amyloidosis. Most notably, our results reveal an A?-dependent impairment of slow-wave propagation, which causes a breakdown of the characteristic long-range coherence of slow-wave activity. The finding that the impairment can be rescued by enhancing GABAAergic inhibition identifies a synaptic mechanism underlying A?-dependent large-scale circuit dysfunction. PMID:26457554
Modeling the Efficiency of a Magnetic Needle for Collecting Magnetic Cells
Butler, Kimberly S; Adolphi, Natalie L.; Bryant, H C; Lovato, Debbie M; Larson, Richard S; Flynn, Edward R
2014-01-01
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 vs. 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. PMID:24874577
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.
Bulk magnetization and 1H NMR spectra of magnetically heterogeneous model systems
Levin, E. M.; Bud' ko, S. L.
2011-04-28
Bulk magnetization and {sup 1}H static and magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of two magnetically heterogeneous model systems based on laponite (LAP) layered silicate or polystyrene (PS) with low and high proton concentration, respectively, and ferrimagnetic Fe{sub 2}O{sub 3} nano- or micro-particles have been studied. In LAP+Fe{sub 2}O{sub 3}, a major contribution to the NMR signal broadening is due to the dipolar coupling between the magnetic moments of protons and magnetic particles. In PS+Fe{sub 2}O{sub 3}, due to the higher proton concentration in polystyrene and stronger proton–proton dipolar coupling, an additional broadening is observed, i.e. {sup 1}H MAS NMR spectra of magnetically heterogeneous systems are sensitive to both proton–magnetic particles and proton–proton dipolar couplings. An increase of the volume magnetization by ?1 emu/cm{sup 3} affects the {sup 1}H NMR signal width in a way that is similar to an increase of the proton concentration by ?2×10{sup 22}/cm{sup 3}. {sup 1}H MAS NMR spectra, along with bulk magnetization measurements, allow the accurate determination of the hydrogen concentration in magnetically heterogeneous systems.
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.)
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.
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.
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.
Simple model of plasma acceleration in a magnetic nozzle
NASA Technical Reports Server (NTRS)
Sercel, Joel C.
1990-01-01
A collisionless, steady-state, cold-plasma model is used to calculate the three-dimensional trajectory of a plasma as it is accelerated through a diverging magnetic field. The magnetic field is assumed to be axisymmetric with nonzero radial and axial components and zero azimuthal component. Although random thermal motion of plasma species is neglected in the cold plasma approximation, an important effect of plasma thermal energy is accounted for in the model as the kinetic energy of electrons in their Larmor motion about magnetic field lines. Calculations based on this model confirm previous studies which suggested that plasma separation from the field of a magnetic nozzle can take place even in the absence of collisional diffusion. It is shown that plasma divergence in a magnetic nozzle can be controlled by tailoring the field geometry.
Jovanovi?, B. E-mail: lionel.torres@lirmm.fr; Brum, R. M.; Torres, L.
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.
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.
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
Model for dynamic self-assembled magnetic surface structures.
Belkin, M.; Glatz, A.; Snezhko, A.; Aranson, I. S.; Materials Science Division; Northwestern Univ.
2010-07-07
We propose a first-principles model for the dynamic self-assembly of magnetic structures at a water-air interface reported in earlier experiments. The model is based on the Navier-Stokes equation for liquids in shallow water approximation coupled to Newton equations for interacting magnetic particles suspended at a water-air interface. The model reproduces most of the observed phenomenology, including spontaneous formation of magnetic snakelike structures, generation of large-scale vortex flows, complex ferromagnetic-antiferromagnetic ordering of the snake, and self-propulsion of bead-snake hybrids.
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.
Modeling and simulation of magnetic shape-memory polymer composites
Rumpf, Martin
as an energy damp- ing mechanism and as actuators. Compared to a single crystal bulk material, the productionModeling and simulation of magnetic shape-memory polymer composites September 6, 2006 S. Conti1 , M Composites of small magnetic-shape-memory (MSM) particles em- bedded in a polymer matrix have been proposed
FORWARD MODELLING AND INVERSION OF GEOPHYSICAL MAGNETIC DATA
Oldenburg, Douglas W.
FORWARD MODELLING AND INVERSION OF GEOPHYSICAL MAGNETIC DATA by PETER GEORGE LELIÃ?VRE A THESIS OF GRADUATE STUDIES (Department of Earth and Ocean Sciences, Geophysics) We accept this thesis as conforming of this research was to invert geophysical magnetic data to recover three dimensional distributions of subsurface
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)
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.
An evaluation of recent internal field models. [of earth magnetism
NASA Technical Reports Server (NTRS)
Mead, G. D.
1979-01-01
The paper reviews the current status of internal field models and evaluates several recently published models by comparing their predictions with annual means of the magnetic field measured at 140 magnetic observatories from 1973 to 1977. Three of the four models studied, viz. AWC/75, IGS/75, and Pogo 8/71, were nearly equal in their ability to predict the magnitude and direction of the current field. The fourth model, IGRF 1975, was significantly poorer in its ability to predict the current field. All models seemed to be able to extrapolate predictions quite well several years outside the data range used to construct the models.
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)
Shinnaka, Shinji
This paper proposes a new dynamic mathematical model of permanent-magnet synchronous motors (PMSMs) with magnetic cross-coupling and presents a new analysis of the torque characteristics of the motors. Generally speaking, dynamic mathematical models used for the design and analysis of PMSM control systems must consist of three basic equations that describe the main motor characteristics as an electrical circuit, torque generator, and electromechanical energy converter. In order to obtain reasonably compact models, some characteristics have to be approximated. However, in the case where the approximations used in the three basic equations are different from each other, the dynamic mathematical model often loses self-consistency and becomes self-contradictory. The proposed model, which takes the magnetic cross-coupling into account, is self-consistent and compact, and its effectiveness is validated by experimental data. Using the self-consistency and compactness, this study presents a new analysis of the torque characteristics of PMSMs, focusing on efficient torque generation.
Magnetic field models from energetic particle data at Neptune
NASA Technical Reports Server (NTRS)
Selesnick, R. S.
1992-01-01
The locations of features in the Voyager 2 energetic particle data from Neptune are combined with uncertainties in the multipole expansion of the planetary magnetic field to derive new magnetic field models that are consistent both with various interpretations of the particle features and with the magnetic field data. While assumptions as to the origin of the features must be made, they do not provide sufficient constraints to obtain significant new information on any of the unknown multipole coefficients. However, the magnetic L shell positions of the particle features, which are interpreted primarily as absorption signatures of Neptune's satellites, can, in general, be brought into agreement with expected values.
Capacitive Stress Gauges in Model Dipole Magnets
Ragland, R. Blake
2009-06-09
Capacitive transducers are used to measure mechanical stress in the windings of superconducting magnets. The transducer consists of a bonded laminate of alternating thin foils of stainless steel and high-strength polymer (polyimide). The thin...
Capacitive Stress Transducers in Model Dipole Magnets
Benson, Christopher P.
2010-07-14
Capacitive stress transducers are used to measure mechanical stresses in the windings of superconducting dipole magnets. These transducers consist of a bonded laminate composed of alternating foils of stainless steel and a high-strength polymer...
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.
Transmission Line Circuit Alexander Glasser
Anlage, Steven
Chaos in a Transmission Line Circuit Alexander Glasser Marshal Miller With... Prof. Edward Ott Prof times become shorter, circuit connections behave more and more like transmission lines. Theoretical in a computer chip #12;Picture of Circuit g Rg Vref Vinc nonlinear capacitor resistor Diode Vg(t) Model + V
Magnetization loop modelling for superconducting/ferromagnetic tube of an ac magnetic cloak
NASA Astrophysics Data System (ADS)
Gömöry, F.; Solovyov, M.; Šouc, J.
2015-04-01
From the combination of superconducting (SC) and ferromagnetic (FM) materials, one can prepare composites with unusual magnetic properties, e.g. for the cloaking of a dc or low-frequency ac magnetic field by a shell from a SC/FM composite. In the design and optimisation of such SC/FM structures, numerical modelling is essential. Non-linear magnetic permeability, as well as the hysteresis of both kinds of materials, are to be incorporated in the calculations aimed at achieving reliable estimates. We present a technique that allows the prediction of the ac magnetization loops of SC/FM composites. The critical state model-based approach is used to describe the properties of the superconducting material. The ferromagnetic part is characterized by its (non-hysteretic) nonlinear permeability. With these ingredients, the distributions of the magnetic field are calculated in subsequent instants of the ac cycle and are used to evaluate the preliminary data for the magnetization loop, which is still missing the hysteresis of the FM part. Afterward, the latter component is added to the magnetization loop by an approximation deduced from the known dependence of the hysteresis loss in the FM material on the ac magnetic field. In spite of its approximate nature, this approach demonstrated very good predictability in experimental tests.
Signal Transduction Model of Magnetic Sensing in Cryptochrome Mediated Photoreception
NASA Astrophysics Data System (ADS)
Todd, Phillise Tiffeny
While migratory birds have long been known to use the Earth's magnetic field for navigation, the precise biophysical mechanism behind this magnetic sense remains unconfirmed. A leading theory of magnetoreception suggests a chemical compass model with a yet undetermined molecular reaction site and unknown magnetically sensitive reactants. The cryptochrome photoreceptor has emerged as a promising candidate site. This investigation numerically models the first order kinetics of cryptochrome mediated photoreception, in order to evaluate its ability to function as a magnetic sensor and transduce orientation information along a neural pathway. A signal-to-noise ratio is defined to quantify the threshold for the functioning of a cryptochrome-based chemical compass. The model suggests that a flavin-superoxide radical pair in cryptochrome functions as the chemical reactants for magnetoreception. Such a cryptochrome-based signal transduction model reasonably predicts the general light intensity and wavelength effects that have been experimentally observed in migratory birds.
Electro-Magnetic Waves within a Model for Charged Solitons
Dmitry Borisyuk; Manfried Faber; Alexander Kobushkin
2007-08-23
We analyze the model of topological fermions (MTF), where charged fermions are treated as soliton solutions of the field equations. In the region far from the sources we find plane waves solutions with the properties of electro-magnetic waves.
Dipole-magnet field models based on a conformal map
NASA Astrophysics Data System (ADS)
Walstrom, P. L.
2012-10-01
In general, generation of charged-particle transfer maps for conventional iron-pole-piece dipole magnets to third and higher order requires a model for the midplane field profile and its transverse derivatives (soft-edge model) to high order and numerical integration of map coefficients. An exact treatment of the problem for a particular magnet requires use of measured magnetic data. However, in initial design of beam transport systems, users of charged-particle optics codes generally rely on magnet models built into the codes. Indeed, if maps to third order are adequate for the problem, an approximate analytic field model together with numerical map coefficient integration can capture the important features of the transfer map. The model described in this paper is based on the fact that, except at very large distances from the magnet, the magnetic field for parallel pole-face magnets with constant pole gap height and wide pole faces is basically two dimensional (2D). The field for all space outside of the pole pieces is given by a single (complex) analytic expression and includes a parameter that controls the rate of falloff of the fringe field. Since the field function is analytic in the complex plane outside of the pole pieces, it satisfies two basic requirements of a field model for higher-order map codes: it is infinitely differentiable at the midplane and also a solution of the Laplace equation. It is apparently the only simple model available that combines an exponential approach to the central field with an inverse cubic falloff of field at large distances from the magnet in a single expression. The model is not intended for detailed fitting of magnetic field data, but for use in numerical map-generating codes for studying the effect of extended fringe fields on higher-order transfer maps. It is based on conformally mapping the area between the pole pieces to the upper half plane, and placing current filaments on the pole faces. An algorithm for computing the midplane field derivatives with the model is described. The model has been incorporated in the particle beam code Marylie/Impact as a special dipole-magnet type along with a tanh model with exponential falloff of the fringe field. Comparison of maps from the tanh model and the new model shows that significant differences in 3rd-order geometric terms can occur, apparently due to the extended fringe field in the new model.
The treatment of magnetic buoyancy in flux transport dynamo models
Choudhuri, Arnab Rai
2015-01-01
One important ingredient of flux transport dynamo models is the rise of the toroidal magnetic field through the convection zone due to magnetic buoyancy to produce bipolar sunspots and then the generation of the poloidal magnetic field from these bipolar sunspots due to the Babcock-Leighton mechanism. Over the years, two methods of treating magnetic buoyancy, a local method and a non-local method have been used widely by different groups in constructing 2D kinematic models of the flux transport dynamo. We review both these methods and conclude that neither of them is fully satisfactory, presumably because magnetic buoyancy is an inherently 3D process. We also point out so far we do not have proper understanding of why sunspot emergence is restricted to rather low latitudes.
Nonlinear Models of Electric Charge and Magnetic Moment
NASA Astrophysics Data System (ADS)
Bersons, I.; Veilande, R.
2015-11-01
The models of the electric charge and magnetic moment are presented based on the nonlinear (cubic) response of a vacuum on the applied electric and magnetic fields. The model of the electric charge contains one parameter—the radius of charge—and predicts one value (both signs) of the electric charge for all elementary particles independently on the value of this radius. Different values of this parameter for the electron are discussed.
NASA Technical Reports Server (NTRS)
Oh, K. S.; Schutt-Aine, J.
1995-01-01
Modeling of interconnects and associated discontinuities with the recent advances high-speed digital circuits has gained a considerable interest over the last decade although the theoretical bases for analyzing these structures were well-established as early as the 1960s. Ongoing research at the present time is focused on devising methods which can be applied to more general geometries than the ones considered in earlier days and, at the same time, improving the computational efficiency and accuracy of these methods. In this thesis, numerically efficient methods to compute the transmission line parameters of a multiconductor system and the equivalent capacitances of various strip discontinuities are presented based on the quasi-static approximation. The presented techniques are applicable to conductors embedded in an arbitrary number of dielectric layers with two possible locations of ground planes at the top and bottom of the dielectric layers. The cross-sections of conductors can be arbitrary as long as they can be described with polygons. An integral equation approach in conjunction with the collocation method is used in the presented methods. A closed-form Green's function is derived based on weighted real images thus avoiding nested infinite summations in the exact Green's function; therefore, this closed-form Green's function is numerically more efficient than the exact Green's function. All elements associated with the moment matrix are computed using the closed-form formulas. Various numerical examples are considered to verify the presented methods, and a comparison of the computed results with other published results showed good agreement.
NASA Technical Reports Server (NTRS)
Starinshak, David P.; Smith, Nathan D.; Wilson, Jeffrey D.
2008-01-01
The electromagnetic effects of conventional dielectrics, anisotropic dielectrics, and metamaterials were modeled in a terahertz-frequency folded-waveguide slow-wave circuit. Results of attempts to utilize these materials to increase efficiency are presented.
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, ...
Cosmic Acceleration and Anisotropic models with Magnetic field
S. K. Tripathy; K. L. Mahanta
2014-12-10
Plane symmetric cosmological models are investigated with or without any dark energy components in the field equations. Keeping an eye on the recent observational constraints concerning the accelerating phase of expansion of the universe, the role of magnetic field is assessed. In the absence of dark energy components, magnetic field can favour an accelerating model even if we take a linear relationship between the directional Hubble parameters. In presence of dark energy components in the form of a time varying cosmological constant, the influence of magnetic field is found to be limited.
Numerical modeling of twisted stacked tape cables for magnet applications
NASA Astrophysics Data System (ADS)
Grilli, Francesco; Zermeño, Victor M. R.; Takayasu, Makoto
2015-11-01
In view of high-temperature superconductor (HTS) magnet applications, the concept of Twisted Stacked Tape Cable (TSTC) made of HTS coated conductors is very promising because of the easy manufacturing process and of the very high tape length usage efficiency. For the use of these cables in magnet applications, where the cables carry high current while subjected to the strong magnetic field generated by the rest of the magnet, the possibility of being able to calculate in detail current and field distributions is very welcome, particularly for evaluating the cable's performance during the charge of the magnet. The numerical modeling of this kind of cable is particularly challenging because of the twisted geometry. In this paper, we use a 3-D finite element model to compute the magnetization AC losses of a twisted superconductor and current repartition among the tapes in a cable composed of four HTS coated conductor tapes. The utilized model is able to simulate not only twisted geometries, but also the contact resistance of the electrical terminations used to inject the current. The latter can importantly influence the current repartition between the tapes, especially in short samples. The model is also able to take into account the angular dependence of the critical current on the local magnetic field, whose relative orientation with respect to the tape needs to be locally evaluated as a consequence of the twisted geometry.
Accounting for crustal magnetization in models of the core magnetic field
NASA Technical Reports Server (NTRS)
Jackson, Andrew
1990-01-01
The problem of determining the magnetic field originating in the earth's core in the presence of remanent and induced magnetization is considered. The effect of remanent magnetization in the crust on satellite measurements of the core magnetic field is investigated. The crust as a zero-mean stationary Gaussian random process is modelled using an idea proposed by Parker (1988). It is shown that the matrix of second-order statistics is proportional to the Gram matrix, which depends only on the inner-products of the appropriate Green's functions, and that at a typical satellite altitude of 400 km the data are correlated out to an angular separation of approximately 15 deg. Accurate and efficient means of calculating the matrix elements are given. It is shown that the variance of measurements of the radial component of a magnetic field due to the crust is expected to be approximately twice that in horizontal components.
NASA Astrophysics Data System (ADS)
Purucker, M.; Sabaka, T.; Le, G.; Slavin, J. A.; Strangeway, R. J.; Busby, C.
2007-12-01
We report the development of a new technique (magnetic gradiometry) for satellite-based remote sensing of the lithosphere. The measurements reported here represent the first systematic measurements of lithospheric magnetic field gradients, and were collected from a spinning spacecraft. The three-satellite ST-5 mission collected vector magnetic field observations at 300-800+ km altitudes over mid and high-northern latitudes in 2006. Away from the auroral oval, and over the continents, the gradients of the low altitude (<400 km) total anomaly field are dominated by lithospheric magnetic fields. Using a seismic starting model, and magnetic field observations from ST-5 and other recent satellite missions, we demonstrate how these techniques can be used to improve our knowledge of the processes involved in the thickened crust of the Colorado Plateau and the Sierra Madre Occidental.
Talpalar, Adolfo E.; Rybak, Ilya A.
2015-01-01
The locomotor gait in limbed animals is defined by the left-right leg coordination and locomotor speed. Coordination between left and right neural activities in the spinal cord controlling left and right legs is provided by commissural interneurons (CINs). Several CIN types have been genetically identified, including the excitatory V3 and excitatory and inhibitory V0 types. Recent studies demonstrated that genetic elimination of all V0 CINs caused switching from a normal left-right alternating activity to a left-right synchronized “hopping” pattern. Furthermore, ablation of only the inhibitory V0 CINs (V0D subtype) resulted in a lack of left-right alternation at low locomotor frequencies and retaining this alternation at high frequencies, whereas selective ablation of the excitatory V0 neurons (V0V subtype) maintained the left–right alternation at low frequencies and switched to a hopping pattern at high frequencies. To analyze these findings, we developed a simplified mathematical model of neural circuits consisting of four pacemaker neurons representing left and right, flexor and extensor rhythm-generating centers interacting via commissural pathways representing V3, V0D, and V0V CINs. The locomotor frequency was controlled by a parameter defining the excitation of neurons and commissural pathways mimicking the effects of N-methyl-D-aspartate on locomotor frequency in isolated rodent spinal cord preparations. The model demonstrated a typical left-right alternating pattern under control conditions, switching to a hopping activity at any frequency after removing both V0 connections, a synchronized pattern at low frequencies with alternation at high frequencies after removing only V0D connections, and an alternating pattern at low frequencies with hopping at high frequencies after removing only V0V connections. We used bifurcation theory and fast-slow decomposition methods to analyze network behavior in the above regimes and transitions between them. The model reproduced, and suggested explanation for, a series of experimental phenomena and generated predictions available for experimental testing. PMID:25970489
A STRUCTURAL-MAGNETIC STRAIN MODEL FOR MAGNETOSTRICTIVE TRANSDUCERS
A STRUCTURAL-MAGNETIC STRAIN MODEL FOR MAGNETOSTRICTIVE TRANSDUCERS Marcelo J. Dapino Department addresses the modeling of strains generated by magnetostrictive transducers in re- sponse to applied in combination with a quadratic moment rotation model for magnetostriction. The incorporation of elastic
Two-dimensional thermal modeling of power monolithic microwave integrated circuits (MMIC's)
NASA Technical Reports Server (NTRS)
Fan, Mark S.; Christou, Aris; Pecht, Michael G.
1992-01-01
Numerical simulations of the two-dimensional temperature distributions for a typical GaAs MMIC circuit are conducted, aiming at understanding the heat conduction process of the circuit chip and providing temperature information for device reliability analysis. The method used is to solve the two-dimensional heat conduction equation with a control-volume-based finite difference scheme. In particular, the effects of the power dissipation and the ambient temperature are examined, and the criterion for the worst operating environment is discussed in terms of the allowed highest device junction temperature.
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.
A Model for the Behavior of Magnetic Tunnel Junctions
Bryan John Baker
2003-08-05
A magnetic tunnel junction is a device that changes its electrical resistance with a change in an applied magnetic field. A typical junction consists of two magnetic electrodes separated by a nonmagnetic insulating layer. The magnetizations of the two electrodes can have two possible extreme configurations, parallel and antiparallel. The antiparallel configuration is observed to have the higher measured resistance and the parallel configuration has the lower resistance. To switch between these two configurations a magnetic field is applied to the device which is primarily used to change the orientation of the magnetization of one electrode usually called the free layer, although with sufficient high magnetic field the orientation of the magnetizations of both of the electrodes can be changed. The most commonly used models for describing and explaining the electronic behavior of tunnel junctions are the Simmons model and the Brinkman model. However, both of these models were designed for simple, spin independent tunneling. The Simmons model does not address the issue of applied magnetic fields nor does it address the form of the electronic band structure in the metallic electrodes, including the important factor of spin polarization. The Brinkman model is similar, the main difference between the two models being the shape of the tunneling barrier potential between the two electrodes. Therefore, the research conducted in this thesis has developed a new theoretical model that addresses these important issues starting from basic principles. The main features of the new model include: the development of equations for true spin dependent tunneling through the insulating barrier, the differences in the orientations of the electrode magnetizations on either side of the barrier, and the effects of the density of states function on the behavior of the junction. The present work has explored densities of states that are more realistic than the simplified free electron density of states function, and has developed an exact analytic solution for the case of an electron band of finite width. The approach taken in this thesis easily allows extension to cases where the band structure is different on either side of the barrier (known as heterojunctions) which are of greater interest in real magnetic tunnel junction devices rather than the simple, identical band structure devices.
Textural remanence - A new model of lunar rock magnetism
NASA Technical Reports Server (NTRS)
Brecher, A.
1976-01-01
In reexamining the accumulated magnetic data on lunar rocks, several common patterns of magnetic behavior are recognized. Their joint occurrence strongly suggests a new model of lunar rock magnetism, which is based on partial preferred textural alignment of the spontaneous moments of magnetic grains without requiring the existence of ancient lunar magnetic fields. This magnetic fabric, mimetic to locally oriented petrofabric, gives rise to an apparent 'textural remanent magnetization'. In order to account for the observed intensity of 'stable remanence' in lunar rocks, only a minute fraction (0.001 to 0.00001) of the single-domain iron grains present need be preferentially aligned. Several mechanisms operating on the lunar surface, including shock and diurnal thermal cycling, appear adequate for producing the required type and degree of magnetic alignment in all lunar rock classes. The model is supported by a wide variety of direct and indirect evidence, and its predictions (e.g., regarding anisotropic susceptibility and remanence acquisition) can be experimentally tested.
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
Modelling and control of a rotor supported by magnetic bearings
NASA Technical Reports Server (NTRS)
Gurumoorthy, R.; Pradeep, A. K.
1994-01-01
In this paper we develop a dynamical model of a rotor and the active magnetic bearings used to support the rotor. We use this model to develop a stable state feedback control of the magnetic bearing system. We present the development of a rigid body model of the rotor, utilizing both Rotation Matrices (Euler Angles) and Euler Parameters (Quaternions). In the latter half of the paper we develop a stable state feedback control of the actively controlled magnetic bearing to control the rotor position under inbalances. The control law developed takes into account the variation of the model with rotational speed. We show stability over the whole operating range of speeds for the magnetic bearing system. Simulation results are presented to demonstrate the closed loop system performance. We develop the model of the magnetic bearing, and present two schemes for the excitation of the poles of the actively controlled magnetic bearing. We also present a scheme for averaging multiple sensor measurements and splitting the actuation forces amongst redundant actuators.
Model of magnetic reconnection in space and astrophysical plasmas
Boozer, Allen H.
2013-03-15
Maxwell's equations imply that exponentially smaller non-ideal effects than commonly assumed can give rapid magnetic reconnection in space and astrophysical plasmas. In an ideal evolution, magnetic field lines act as stretchable strings, which can become ever more entangled but cannot be cut. High entanglement makes the lines exponentially sensitive to small non-ideal changes in the magnetic field. The cause is well known in popular culture as the butterfly effect and in the theory of deterministic dynamical systems as a sensitive dependence on initial conditions, but the importance to magnetic reconnection is not generally recognized. Two-coordinate models are too constrained geometrically for the required entanglement, but otherwise the effect is general and can be studied in simple models. A simple model is introduced, which is periodic in the x and y Cartesian coordinates and bounded by perfectly conducting planes in z. Starting from a constant magnetic field in the z direction, reconnection is driven by a spatially smooth, bounded force. The model is complete and could be used to study the impulsive transfer of energy between the magnetic field and the ions and electrons using a kinetic plasma model.
Bianchi Type I Magnetized String Cosmological Model in General Relativity
NASA Astrophysics Data System (ADS)
Bali, Raj; Anjali
2006-04-01
Bianchi Type I magnetized string cosmological model following the techniques used by Letelier and Stachel, is investigated. To get a determinate model, we assume a condition ? = ? (geometric string) where ? is the rest energy density, ? the string tension density and expansion (?) is proportional to eigen value ?1 1 of shear tensor (? j i ), which leads to A = ? ( BC) n where A, B, C are metric potentials and ? and n are constants. The behaviour of the model in presence and absence of magnetic field is discussed. The physical and geometrical aspects of the model are also discussed.
Model for temperature-dependent magnetization of nanocrystalline materials
Bian, Q.; Niewczas, M.
2015-01-07
A magnetization model of nanocrystalline materials incorporating intragrain anisotropies, intergrain interactions, and texture effects has been extended to include the thermal fluctuations. The method relies on the stochastic Landau–Lifshitz–Gilbert theory of magnetization dynamics and permits to study the magnetic properties of nanocrystalline materials at arbitrary temperature below the Currie temperature. The model has been used to determine the intergrain exchange constant and grain boundary anisotropy constant of nanocrystalline Ni at 100?K and 298?K. It is found that the thermal fluctuations suppress the strength of the intergrain exchange coupling and also reduce the grain boundary anisotropy. In comparison with its value at 2?K, the interparticle exchange constant decreases by 16% and 42% and the grain boundary anisotropy constant decreases by 28% and 40% at 100?K and 298?K, respectively. An application of the model to study the grain size-dependent magnetization indicates that when the thermal activation energy is comparable to the free energy of grains, the decrease in the grain size leads to the decrease in the magnetic permeability and saturation magnetization. The mechanism by which the grain size influences the magnetic properties of nc–Ni is discussed.
Experimental and Theoretical Studies of a Dynamic Nitrogen Arc in a Model Circuit-Breaker
NASA Astrophysics Data System (ADS)
Lau, Yuk-Chiu
Detailed measurements of dynamic arcs represent an important contribution to the understanding of the extinction processes such as occur in circuit-breaker devices. In the present work, the experi- mentally determined distributions of temperature and size of a dynamic nitrogen arc burning in a single flow model interrupter were compared with theoretical computations. The interrupter contained a converging-diverging nozzle, with a throat diameter of 10 mm, and a length- -from throat to exit--of 86 mm. Operating conditions included: stagnation pressure = 13.9 atm (14 bar); amplitude of the sinusoidal main pulse = 1.2 kA; half period of the main pulse (DBLTURN) 190 (mu)s; and dI/dt at current zero = -17 A/(mu)s (calculated). A high speed optical system was used to monitor the arc radiation. Nitrogen continuum radiation, at 432 nm, was employed to determine the arc temperature (assuming local thermo- dynamic equilibrium). Data were obtained at an axial position 3 mm downstream of the throat from about 70 (mu)s ((TURN)900 A) to about 1 (mu)s ((TURN)10 A) before current zero. The measured centerline temperature was about 16,000 K at high currents ((LESSTHEQ)900 A) decaying at a rate of -40 k/(mu)s. The measured arc diameter (defined by the 9,000K iso- therm) was about 4 mm at high currents ((LESSTHEQ)900 A). As the current was decreased (I < 400 A), the centerline temperature decayed at a much faster rate, to -400 K/(mu)s at 1 ms before current zero ((TURN)10A; at about 8,700 K). The arc diameter varied between 2.5 mm and 3 mm at time t (TURN) -10 (mu)s. Increasing turbulence levels at lower currents were sug- gested by the observed increase in fluctuations in the arc scan data. The one-dimensional arc model of Tuma 1 , has been applied to the present conditions. The analysis contained three parameters--n, (lamda) and F(,T)--which were determined from correlation with experiment (specifically the arc voltage waveshape prior to current zero). The values of n = 0.5, (lamda) = 0.022, and F(,T) = 0.06 were used to compute the timewise distributions of the centerline arc temperature and arc diameter. Good agreement (within 5% on arc temperature, and 6%. at high currents and 20% at low currents on arc diameter) was found between experiment and theory. 1. D. T. Tuma, IEEE Trans. Power App. and Syst., PAS-99, pp. 2129-2137, 1980.
NASA Astrophysics Data System (ADS)
Shen, Ji-Fu; He, Yi-Jun; Ma, Zi-Feng
2016-01-01
Accurate modeling of the charge redistribution dominated self-discharge process plays a significant role in power management systems for supercapacitors. Although equivalent circuit models (ECMs) are widely used to describe the nonlinear behaviors of the self-discharge process, they are usually separately established at different initial voltages, which might result in poor prediction performances at other unseen initial voltages. In this study, a three-branch model with a leakage resistance is used to describe the nonlinear dynamic behavior of the supercapacitor self-discharge dominated by charge redistribution and the circuit parameters in ECMs are explicitly modeled as a function of the initial voltage. Polynomial functions with different orders are systematically evaluated by means of fitting and prediction accuracy. The impacts of initial voltage and temperature on the charge redistribution dominated self-discharge process are experimentally investigated with a 3000 F commercial supercapacitor. The modeling results show that a 5th-order polynomial function is sufficient high enough to characterize the nonlinear effect of initial voltage on the charge redistribution dominated self-discharge in terms of prediction accuracy. Moreover, the prediction accuracy of polynomial function based ECMs are significantly better than that of interpolation based ECMs, which further validates the effectiveness of the proposed model.
KrylovSubspace Iterations for ReducedOrder Modeling in VLSI Circuit Simulation
@research.belllabs.com Keywords: linear system, transfer function, passivity, Lanczos process, projection Abstract In recent years namical systems. Much of the recent work in this area has been driven by the need for efficient reduced fabricated in silicon. The simulation of electronic circuits involves the nu merical solution of very large
ERIC Educational Resources Information Center
Schleyer, Michael; Saumweber, Timo; Nahrendorf, Wiebke; Fischer, Benjamin; von Alpen, Desiree; Pauls, Dennis; Thum, Andreas; Gerber, Bertram
2011-01-01
Drosophila larvae combine a numerically simple brain, a correspondingly moderate behavioral complexity, and the availability of a rich toolbox for transgenic manipulation. This makes them attractive as a study case when trying to achieve a circuit-level understanding of behavior organization. From a series of behavioral experiments, we suggest a…
Reproducibility of the coil positioning in Nb3Sn magnet models through magnetic measurements.
Borgnolutti, F.; Caspi, S.; Ferracin, P.; Kashikhin, V.V.; Sabbi, G.; Velev, G.; Todesco, E.; Zlobin, A.V.
2009-08-17
The random part of the integral field harmonics in a series of superconducting magnets has been used in the past to identify the reproducibility of the coil positioning. Using a magnetic model and a MonteCarlo approach, coil blocks are randomly moved and the amplitude that best fits the magnetic measurements is interpreted as the reproducibility of the coil position. Previous values for r.m.s. coil displacements for Nb-Ti magnets range from 0.05 to 0.01 mm. In this paper, we use this approach to estimate the reproducibility in the coil position for Nb{sub 3}Sn short models that have been built in the framework of the FNAL core program (HFDA dipoles) and of the LARP program (TQ quadrupoles). Our analysis shows that the Nb{sub 3}Sn models manufactured in the past years correspond to r.m.s. coil displacements of at least 5 times what is found for the series production of a mature Nb-Ti technology. On the other hand, the variability of the field harmonics along the magnet axis shows that Nb3Sn magnets have already reached values similar to these obtained for Nb-Ti ones.
Reproducibility of the coil positioning in Nb$_3$Sn magnet models through magnetic measurements
Borgnolutti, F; Ferracin, P; Kashikhin, V V; Sabbi, G; Velev, G; Todesco, E; Zlobin, A V; 10.1109/TASC.2009.2018530
2009-01-01
The random part of the integral field harmonics in a series of superconducting magnets has been used in the past to identify the reproducibility of the coil positioning. Using a magnetic model and a MonteCarlo approach, coil blocks are randomly moved and the amplitude that best fits the magnetic measurements is interpreted as the reproducibility of the coil position. Previous values for r.m.s. coil displacements for Nb-Ti magnets range from 0.05 to 0.01 mm. In this paper, we use this approach to estimate the reproducibility in the coil position for Nb3Sn short models that have been built in the framework of the FNAL core program (HFDA dipoles) and of the LARP program (TQ quadrupoles). Our analysis shows that the Nb3Sn models manufactured in the past years correspond to r.m.s. coil displacements of at least 5 times what is found for the series production of a mature Nb-Ti technology. On the other hand, the variability of the field harmonics along the magnet axis shows that Nb3Sn magnets have already reached va...
Ring Current Modeling in a Realistic Magnetic Field Configuration
NASA Technical Reports Server (NTRS)
Fok, M.-C.; Moore, T. E.
1997-01-01
A 3-dimensional kinetic model has been developed to study the dynamics of the storm time ring current in a dipole magnetic field. In this paper, the ring current model is extended to include a realistic, time-varying magnetic field model. The magnetic field is expressed as the cross product of the gradients of two Euler potentials and the bounce-averaged particle drifts are calculated in the Euler potential coordinates. A dipolarization event is modeled by collapsing a tail-like magnetosphere to a dipole-like configuration. Our model is able to simulate the sudden enhancements in the ring current ion fluxes and the corresponding ionospheric precipitation during the substorm expansion.
Circuits logiques. partie 2 : circuits squentiels
Louvet, Nicolas
Circuits logiques. partie 2 : circuits séquentiels 1 Circuits élémentaires de mémorisation : les. Louvet Circuits logiques, partie 1 : circuits séquentiels. 28 janvier 2015 1 / 40 #12;Introduction Dans les circuits combinatoires la notion de temps joue un rôle « mineur » : même si tout circuit
Modeling, design and control of a 30 hp permanent magnet synchronous motor
Chang, L.
1991-01-01
In this thesis, aspects of modeling, design and control of permanent magnet synchronous motors (PMSMs) are studied. An improved analytical model with stator winding space harmonics included is derived, based on generalized electrical machine theory. Neglecting the space harmonics leads to a simplified d-q equivalent circuit model. These analytical models allow the terminal quantities of a PMSM to be determined. A finite element model is established to obtain the field quantities, with detailed geometry and material characteristics taken into account. Improve post-processing algorithms are developed. Novel torque calculation methods based on Maxwell's stress tenor and coenergy concepts, and a new inductance evaluation algorithm have increased the accuracy and reduced the computing time and effort. The combination of the analytical method which is used for preliminary design, and the finite element method which is used for fine-tuning the final design, provides an effective methodology for PMSM design. The effects of a wide range of metric variables on the performance of PMSMs are investigated. A set of design criteria are proposed in addition to the design specifications. Using the proposed design methodology, a 30 hp prototype PMSM with NdFeB permanent magnets has been designed, assembled and tested. Various steady state tests of the prototype PMSM are conducted. The close agreement between the test results and those predicted from the analytical model and the finite element model has validated these models, and has confirmed the design. A microcontroller-30 hp transistor inverter system is implemented for the PMSM drive. A complete model for the drive system is established for computer simulation. A modified independent current hysteresis control has been developed and tested, resulting in an improved stator current waveform.
Modeling the (upper) solar atmosphere including the magnetic field
H. Peter
2007-03-21
The atmosphere of the Sun is highly structured and dynamic in nature. From the photosphere and chromosphere into the transition region and the corona plasma-$\\beta$ changes from above to below one, i.e. while in the lower atmosphere the energy density of the plasma dominates, in the upper atmosphere the magnetic field plays the governing role -- one might speak of a ``magnetic transition''. Therefore the dynamics of the overshooting convection in the photosphere, the granulation, is shuffling the magnetic field around in the photosphere. This leads not only to a (re-)structuring of the magnetic field in the upper atmosphere, but induces also the dynamic reaction of the coronal plasma e.g. due to reconnection events. Therefore the (complex) structure and the interaction of various magnetic patches is crucial to understand the structure, dynamics and heating of coronal plasma as well as its acceleration into the solar wind. The present article will emphasize the need for three-dimensional modeling accounting for the complexity of the solar atmosphere to understand these processes. Some advances on 3D modeling of the upper solar atmosphere in magnetically closed as well as open regions will be presented together with diagnostic tools to compare these models to observations. This highlights the recent success of these models which in many respects closely match the observations.
NASA Astrophysics Data System (ADS)
England, Troy; Curry, Matthew; Carr, Steve; Swartzentruber, Brian; Lilly, Michael; Bishop, Nathan; Carrol, Malcolm
2015-03-01
Fast, low-power quantum state readout is one of many challenges facing quantum information processing. Single electron transistors (SETs) are potentially fast, sensitive detectors for performing spin readout of electrons bound to Si:P donors. From a circuit perspective, however, their output impedance and nonlinear conductance are ill suited to drive the parasitic capacitance typical of coaxial conductors used in cryogenic environments, necessitating a cryogenic amplification stage. We will discuss calibration data, as well as modeling and simulation of cryogenic silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) circuits connected to a silicon SET and operating at 4 K. We find a continuum of solutions from simple, single-HBT amplifiers to more complex, multi-HBT circuits suitable for integration, with varying noise levels and power vs. bandwidth tradeoffs. This work was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE Office of Basic Energy Sciences user facility. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the U. S. Department of Energy under Contract No. DE-AC04-94AL85000.
Alterations in the motor neuron-Renshaw cell circuit in the Sod1G93A mouse model
Wootz, Hanna; FitzSimons-Kantamneni, Eileen; Larhammar, Martin; Rotterman, Travis M.; Enjin, Anders; Patra, Kalicharan; Andre, Elodie; van Zundert, Brigitte; Kullander, Klas; Alvarez, Francisco J.
2012-01-01
Motor neurons become hyperexcitable during progression of amyotrophic lateral sclerosis (ALS). This abnormal firing behavior has been explained by changes in their membrane properties, but more recently it has been suggested that changes in premotor circuits may also contribute to this abnormal activity. The specific circuits that may be altered during development of ALS have not been investigated. Here we examined the Renshaw cell recurrent circuit that exerts inhibitory feedback control on motor neuron firing. Using two markers for Renshaw cells (calbindin and Chrna2 , cholinergic nicotinic receptor subunit alpha2), two general markers for motor neurons (NeuN and VAChT, vesicular acethylcholine transporter ) and two markers for fast motor neurons (Chondrolectin and Calca, calcitonin-related polypeptide alpha), we analyzed the survival and connectivity of these cells during disease progression in the Sod1G93A mouse model. Most calbindin-immunoreactive (IR) Renshaw cells survive to end-stage but downregulate postsynaptic Chrna2 in presymptomatic animals. In motor neurons, some markers are downregulated early (NeuN, VAChT, Chondrolectin) and others at end-stage(Calca). Early downregulation of presynaptic VAChT and Chrna2 was correlated with disconnection from Renshaw cells as well as major structural abnormalities of motor axon synapses inside the spinal cord. Renshaw cell synapses on motor neurons underwent more complex changes, including transitional sprouting preferentially over remaining NeuN-IR motor neurons. We conclude that the loss of presynaptic motor axon input on Renshaw cells occurs at early stages of ALS and disconnects the recurrent inhibitory circuit, presumably resulting in a diminished control of motor neuron firing. PMID:23172249
Measuring and modeling the magnetic settling of superparamagnetic nanoparticle dispersions.
Prigiobbe, Valentina; Ko, Saebom; Huh, Chun; Bryant, Steven L
2015-06-01
In this paper, we present settling experiments and mathematical modeling to study the magnetic separation of superparamagnetic iron-oxide nanoparticles (SPIONs) from a brine. The experiments were performed using SPIONs suspensions of concentration between 3 and 202g/L dispersed in water and separated from the liquid under the effect of a permanent magnet. A 1D model was developed in the framework of the sedimentation theory with a conservation law for SPIONs and a mass flux function based on the Newton's law for motion in a magnetic field. The model describes both the hindering effect of suspension concentration (n) during settling due to particle collisions and the increase in settling rate due to the attraction of the SPIONs towards the magnet. The flux function was derived from the settling experiments and the numerical model validated against the analytical solution and the experimental data. Suspensions of SPIONs were of 2.8cm initial height, placed on a magnet, and monitored continuously with a digital camera. Applying a magnetic field of 0.5T of polarization, the SPION's velocity was of approximately 3·10(-5)m/s close to the magnet and decreases of two orders of magnitude across the domain. The process was characterized initially by a classical sedimentation behavior, i.e., an upper interface between the clear water and the suspension slowly moving towards the magnet and a lower interface between the sediment layer and the suspension moving away from the magnet. Subsequently, a rapid separation of nanoparticle occured suggesting a non-classical settling phenomenon induced by magnetic forces which favor particle aggregation and therefore faster settling. The rate of settling decreased with n and an optimal condition for fast separation was found for an initial n of 120g/L. The model agrees well with the measurements in the early stage of the settling, but it fails to describe the upper interface movement during the later stage, probably because of particle aggregation induced by magnetization which is not accounted for in the model. PMID:25700211
Superconductivity from spoiling magnetism in the Kondo lattice model
NASA Astrophysics Data System (ADS)
Asadzadeh, Mohammad Zhian; Fabrizio, Michele; Becca, Federico
2014-11-01
We find evidence that superconductivity intrudes into the paramagnetic-to-magnetic transition of the Kondo lattice model if magnetic frustration is added. Specifically, we study by the variational method the model on a square lattice in the presence of both nearest-neighbor (t ) and next-nearest-neighbor (t') hopping of the conduction electrons. We find that, when t'/t >0 , a d -wave superconducting dome emerges between the magnetic and paramagnetic metal phases and close to the compensated regime, i.e., the number of conduction electrons equals the number of localized spin-1/2 moments. Superconductivity is further strengthened by a direct antiferromagnetic exchange, JH, between the localized moments, to such an extent that we observe coexistence with magnetic order.
Three-dimensional magnetic optimization of accelerator magnets using an analytic strip model
Rochepault, Etienne Aubert, Guy; Vedrine, Pierre
2014-07-14
The end design is a critical step in the design of superconducting accelerator magnets. First, the strain energy of the conductors must be minimized, which can be achieved using differential geometry. The end design also requires an optimization of the magnetic field homogeneity. A mechanical and magnetic model for the conductors, using developable strips, is described in this paper. This model can be applied to superconducting Rutherford cables, and it is particularly suitable for High Temperature Superconducting tapes. The great advantage of this approach is analytic simplifications in the field computation, allowing for very fast and accurate computations, which save a considerable computational time during the optimization process. Some 3D designs for dipoles are finally proposed, and it is shown that the harmonic integrals can be easily optimized using this model.
Atomically crafted spin lattices as model systems for quantum magnetism
NASA Astrophysics Data System (ADS)
Spinelli, A.; Rebergen, M. P.; Otte, A. F.
2015-06-01
Low-dimensional quantum magnetism presents a seemingly unlimited source of rich, intriguing physics. Yet, because realistic experimental representations are difficult to come by, the field remains predominantly theoretical. In recent years, artificial spin structures built through manipulation of magnetic atoms in a scanning tunnelling microscope have developed into a promising testing ground for experimental verification of theoretical models. Here, we present an overview of available tools and discuss recent achievements as well as future avenues. Moreover, we show new observations on magnetic switching in a bistable bit that can be used to extrapolate information on the magnetisation of the microscope tip.
Modeling and Particle Tracking through Longitudinal Gradient Bending Magnets
Bittermann, Noah
2015-01-01
This report documents the development of a versatile model for longitudinal gradient bending magnets (LGB's) and its implementation in particle tracking simulations. The model presented below may be used to represent an arbitrary magnetic field profile, and was successfully implemented to represent two different LGB's. After building a symplectic integrator for our model, we were able to perform particle tracking studies. By producing phase space plots which depicted stable trajectories, we were able to demonstrate that we had in fact correctly implemented our symplectic integration scheme. In addition, we produced stack representations for the bending component of the magnetic field for each LGB and made preliminary comparisons between lattices implementing this model and our own.
GENERIC MODEL FOR MAGNETIC EXPLOSIONS APPLIED TO SOLAR FLARES
Melrose, D. B.
2012-04-10
An accepted model for magnetospheric substorms is proposed as the basis for a generic model for magnetic explosions and is applied to solar flares. The model involves widely separated energy-release and particle-acceleration regions, with energy transported Alfvenically between them. On a global scale, these regions are coupled by a large-scale current that is set up during the explosion by redirection of pre-existing current associated with the stored magnetic energy. The explosion-related current is driven by an electromotive force (EMF) due to the changing magnetic flux enclosed by this current. The current path and the EMF are identified for an idealized quadrupolar model for a flare.
Modelling of micro-Hall sensors for magnetization imaging
NASA Astrophysics Data System (ADS)
Manzin, A.; Nabaei, V.
2014-05-01
This paper presents a numerical model for the study of micro-Hall magnetometry applications, aiming at evaluating the sensitivity of semiconductor miniaturized devices to the stray field of permalloy nanostructures with ring and disk geometry. The procedure couples a micromagnetic code, for the calculation of the stray field generated by the nanomagnet, to a 2D classical transport model for the determination of the electric potential distribution inside the Hall plate. The model is applied to study the sensitivity of a micro-Hall device in the detection of magnetization switching processes characterized by vortex state, focusing on the influence of magnetic nanostructure position.
Modeling Left Ventricle Wall Motion Using Tagged Magnetic Resonance Imaging
Alenezy, Mohammed D.
2009-04-17
A two-parameter computational model is proposed for the study of the regional motion of the left ventricle (LV) wall using tagged magnetic resonance imaging (tMRI) data. In this model, the LV wall motion is mathematically decomposed into two...
Model Reference Adaptive Control of Permanent Magnet Synchronous Motor
NASA Astrophysics Data System (ADS)
Tárník, Marián; Murgaš, Ján
2011-05-01
In this paper the classical theory of the direct Model Reference Adaptive Control is used to develop a control algorithm for Permanent Magnet Synchronous Motor (PMSM). A PMSM model widely used in electric drives community is considered as base for control system development. Conventionally used controllers are replaced by adaptive ones. The resulting control system adapts to changes in any of PMSM parameters.
Finite Element Modeling of Magnetically-Damped Convection during Solidification
NASA Technical Reports Server (NTRS)
deGroh, H. C.; Li, B. Q.; Lu, X.
1998-01-01
A fully 3-D, transient finite element model is developed to represent the magnetic damping effects on complex fluid flow, heat transfer and electromagnetic field distributions in a Sn- 35.5%Pb melt undergoing unidirectional solidification. The model is developed based on our in- house finite element code for the fluid flow, heat transfer and electromagnetic field calculations. The numerical model is tested against numerical and experimental results for water as reported in literature. Various numerical simulations are carried out for the melt convection and temperature distribution with and without the presence of a transverse magnetic field. Numerical results show that magnetic damping can be effectively applied to stabilize melt flow, reduce turbulence and flow levels in the melt and over a certain threshold value a higher magnetic field resulted in a greater reduction in velocity. Also, for the study of melt flow instability, a long enough running time is needed to ensure the final fluid flow recirculation pattern. Moreover, numerical results suggest that there seems to exist a threshold value of applied magnetic field, above which magnetic damping becomes possible and below which the 0 convection in the melt is actually enhanced.
Simplified thermal model of the ITER magnet system
NASA Astrophysics Data System (ADS)
Furci, Hernán; Luongo, Cesar
2014-09-01
A simplified thermal model of the ITER magnet system has been developed to capture the essence of the magnet heat load dynamics without the need for extensive computations. Idealization of the magnets has been made using mainly two standard types of elements, solids and tubes. No Navier-Stokes equations have been solved for the hydraulics, but instead a simple transport model with approximation for pressure evolution has been used. The model was implemented in C language and used to investigate the important features needed to implement a computationally efficient and fast magnet thermal model capturing overall behavior in terms of superconductor cooling channel description (thermal coupling with jackets, presence of the conductor, importance of the central channel, etc.). Furthermore, the model was benchmarked against validated simulation tools such as SuperMagnet and Vincenta using the ITER Central Solenoid normal operation scenario for comparison. Dynamics were shown to be reproduced in good agreement with results attainable with these more detailed codes, considering the high level of uncertainty on the input parameters, namely the heat transfer coefficients and the values of heat loads.
Towards better constrained models of the solar magnetic cycle
NASA Astrophysics Data System (ADS)
Munoz-Jaramillo, Andres
2010-12-01
The best tools we have for understanding the origin of solar magnetic variability are kinematic dynamo models. During the last decade, this type of models has seen a continuous evolution and has become increasingly successful at reproducing solar cycle characteristics. The basic ingredients of these models are: the solar differential rotation -- which acts as the main source of energy for the system by shearing the magnetic field; the meridional circulation -- which plays a crucial role in magnetic field transport; the turbulent diffusivity -- which attempts to capture the effect of convective turbulence on the large scale magnetic field; and the poloidal field source -- which closes the cycle by regenerating the poloidal magnetic field. However, most of these ingredients remain poorly constrained which allows one to obtain solar-like solutions by "tuning" the input parameters, leading to controversy regarding which parameter set is more appropriate. In this thesis we revisit each of those ingredients in an attempt to constrain them better by using observational data and theoretical considerations, reducing the amount of free parameters in the model. For the meridional flow and differential rotation we use helioseismic data to constrain free parameters and find that the differential rotation is well determined, but the available data can only constrain the latitudinal dependence of the meridional flow. For the turbulent magnetic diffusivity we show that combining mixing-length theory estimates with magnetic quenching allows us to obtain viable magnetic cycles and that the commonly used diffusivity profiles can be understood as a spatiotemporal average of this process. For the poloidal source we introduce a more realistic way of modeling active region emergence and decay and find that this resolves existing discrepancies between kinematic dynamo models and surface flux transport simulations. We also study the physical mechanisms behind the unusually long minimum of cycle 23 and find it to be tied to changes in the meridional flow. Finally, by carefully constraining the system through surface magnetic field observations, we find that what is believed to be the primary source of poloidal field (also known as Babckock-Leigthon mechanism) may not be enough to sustain the solar magnetic cycle.
Residential magnetic fields predicted from wiring configurations: I. Exposure model.
Bowman, J D; Thomas, D C; Jiang, L; Jiang, F; Peters, J M
1999-10-01
A physically based model for residential magnetic fields from electric transmission and distribution wiring was developed to reanalyze the Los Angeles study of childhood leukemia by London et al. For this exposure model, magnetic field measurements were fitted to a function of wire configuration attributes that was derived from a multipole expansion of the Law of Biot and Savart. The model parameters were determined by nonlinear regression techniques, using wiring data, distances, and the geometric mean of the ELF magnetic field magnitude from 24-h bedroom measurements taken at 288 homes during the epidemiologic study. The best fit to the measurement data was obtained with separate models for the two major utilities serving Los Angeles County. This model's predictions produced a correlation of 0.40 with the measured fields, an improvement on the 0.27 correlation obtained with the Wertheimer-Leeper (WL) wire code. For the leukemia risk analysis in a companion paper, the regression model predicts exposures to the 24-h geometric mean of the ELF magnetic fields in Los Angeles homes where only wiring data and distances have been obtained. Since these input parameters for the exposure model usually do not change for many years, the predicted magnetic fields will be stable over long time periods, just like the WL code. If the geometric mean is not the exposure metric associated with cancer, this regression technique could be used to estimate long-term exposures to temporal variability metrics and other characteristics of the ELF magnetic field which may be cancer risk factors. PMID:10495305
NASA Astrophysics Data System (ADS)
Novitskii, N. N.
2013-12-01
This article is devoted to the results of the investigation into the principle of linearization of hydraulic circuits by V.Ya. Khasilev in order to use it in new avenues. The questions of applying this principle to linearize the "nodal" models of flow distribution, the provision of larger universality of the linearization procedure, and the development of new methods of flow distribution are considered for the first time. The description of a new method of secants and a new method of chords as well as the numerical examples illustrating their computational efficiency are presented.
A semi-analytic model of magnetized liner inertial fusion
NASA Astrophysics Data System (ADS)
McBride, Ryan D.; Slutz, Stephen A.
2015-05-01
Presented is a semi-analytic model of magnetized liner inertial fusion (MagLIF). This model accounts for several key aspects of MagLIF, including: (1) preheat of the fuel (optionally via laser absorption); (2) pulsed-power-driven liner implosion; (3) liner compressibility with an analytic equation of state, artificial viscosity, internal magnetic pressure, and ohmic heating; (4) adiabatic compression and heating of the fuel; (5) radiative losses and fuel opacity; (6) magnetic flux compression with Nernst thermoelectric losses; (7) magnetized electron and ion thermal conduction losses; (8) end losses; (9) enhanced losses due to prescribed dopant concentrations and contaminant mix; (10) deuterium-deuterium and deuterium-tritium primary fusion reactions for arbitrary deuterium to tritium fuel ratios; and (11) magnetized ?-particle fuel heating. We show that this simplified model, with its transparent and accessible physics, can be used to reproduce the general 1D behavior presented throughout the original MagLIF paper [S. A. Slutz et al., Phys. Plasmas 17, 056303 (2010)]. We also discuss some important physics insights gained as a result of developing this model, such as the dependence of radiative loss rates on the radial fraction of the fuel that is preheated.
A semi-analytic model of magnetized liner inertial fusion
McBride, Ryan D.; Slutz, Stephen A.
2015-05-15
Presented is a semi-analytic model of magnetized liner inertial fusion (MagLIF). This model accounts for several key aspects of MagLIF, including: (1) preheat of the fuel (optionally via laser absorption); (2) pulsed-power-driven liner implosion; (3) liner compressibility with an analytic equation of state, artificial viscosity, internal magnetic pressure, and ohmic heating; (4) adiabatic compression and heating of the fuel; (5) radiative losses and fuel opacity; (6) magnetic flux compression with Nernst thermoelectric losses; (7) magnetized electron and ion thermal conduction losses; (8) end losses; (9) enhanced losses due to prescribed dopant concentrations and contaminant mix; (10) deuterium-deuterium and deuterium-tritium primary fusion reactions for arbitrary deuterium to tritium fuel ratios; and (11) magnetized ?-particle fuel heating. We show that this simplified model, with its transparent and accessible physics, can be used to reproduce the general 1D behavior presented throughout the original MagLIF paper [S. A. Slutz et al., Phys. Plasmas 17, 056303 (2010)]. We also discuss some important physics insights gained as a result of developing this model, such as the dependence of radiative loss rates on the radial fraction of the fuel that is preheated.
Error field and magnetic diagnostic modeling for W7-X
Lazerson, Sam A.; Gates, David A.; NEILSON, GEORGE H.; OTTE, M.; Bozhenkov, S.; Pedersen, T. S.; GEIGER, J.; LORE, J.
2014-07-01
The prediction, detection, and compensation of error fields for the W7-X device will play a key role in achieving a high beta (? = 5%), steady state (30 minute pulse) operating regime utilizing the island divertor system [1]. Additionally, detection and control of the equilibrium magnetic structure in the scrape-off layer will be necessary in the long-pulse campaign as bootstrapcurrent evolution may result in poor edge magnetic structure [2]. An SVD analysis of the magnetic diagnostics set indicates an ability to measure the toroidal current and stored energy, while profile variations go undetected in the magnetic diagnostics. An additional set of magnetic diagnostics is proposed which improves the ability to constrain the equilibrium current and pressure profiles. However, even with the ability to accurately measure equilibrium parameters, the presence of error fields can modify both the plasma response and diverter magnetic field structures in unfavorable ways. Vacuum flux surface mapping experiments allow for direct measurement of these modifications to magnetic structure. The ability to conduct such an experiment is a unique feature of stellarators. The trim coils may then be used to forward model the effect of an applied n = 1 error field. This allows the determination of lower limits for the detection of error field amplitude and phase using flux surface mapping. *Research supported by the U.S. DOE under Contract No. DE-AC02-09CH11466 with Princeton University.
Magnetic properties of the ALS (Advanced Light Source) booster synchrotron engineering model magnets
Keller, R.; Green, M.I.; Hoyer, E.; Koo, Y.M.; Luchini, K.; Marks, S.; Milburn, J.; Nelson, D.H.
1989-03-01
The Advanced Light Source (ALS) at Lawrence Berkeley Laboratory is designed to be a third-generation electron storage ring producing high-brightness VUV and X-ray radiation from wiggler and undulator insertion devices. Engineering models of all lattice magnets that are to be installed in the storage ring and its booster synchrotron have been built and are being tested to verify their performance. This paper is concerned with the magnets that form the booster lattice: dipoles, quadrupoles, sextupoles, and corrector dipoles (steerers). After a brief outline of measurement techniques and equipment, the major design parameters of these magnets are listed. Measured effective lengths and multipole field errors are then given for each type. All engineering models meet the specifications, and tracking studies including the measured systematic field errors show acceptable performance of the booster synchrotron; hence the designs are qualified for production. 3 refs., 7 figs., 4 tabs.
Walker, Duncan M. "Hank"
techniques General Terms: Design, Verification Additional Key Words and Phrases: bridge faults, fault modelsA Circuit Level Fault Model for Resistive Bridges ZHUO LI, XIANG LU, WANGQI QIU, WEIPING SHI and D. Modeling bridge faults as delay faults helps delay tests to detect more bridge faults. Traditional bridge
Neutron matter under strong magnetic fields: A comparison of models
NASA Astrophysics Data System (ADS)
Aguirre, R.; Bauer, E.; Vidaña, I.
2014-03-01
The equation of state of neutron matter is affected by the presence of a magnetic field due to the intrinsic magnetic moment of the neutron. Here we study the equilibrium configuration of this system for a wide range of densities, temperatures, and magnetic fields. Special attention is paid to the behavior of the isothermal compressibility and the magnetic susceptibility. Our calculation is performed using both microscopic and phenomenological approaches of the neutron matter equation of state, namely the Brueckner-Hartree-Fock (BHF) approach using the Argonne V18 nucleon-nucleon potential supplemented with the Urbana IX three-nucleon force, the effective Skyrme model in a Hartree-Fock description, and the quantum hadrodynamic formulation with a mean-field approximation. All these approaches predict a change from completely spin polarized to partially polarized matter that leads to a continuous equation of state. The compressibility and the magnetic susceptibility show characteristic behaviors which reflect that fact. Thermal effects tend to smear out the sharpness found for these quantities at T =0. In most cases a thermal increase of ?T =10 MeV is enough to hide the signals of the change of polarization. The set of densities and magnetic field intensities for which the system changes it spin polarization is different for each model. However, we found that under the conditions examined in this work there is an overall agreement between the three theoretical descriptions.
Analytical models of finite thin disks in a magnetic field
Edinson Cardona-Rueda; Gonzalo García-Reyes
2015-09-16
Analytical models of axially symmetric thin disks of finite extension in presence of magnetic field are presented based on the well-known Morgan-Morgan solutions. The source of the magnetic field is cons\\-tructed separating the equation corresponding to the Ampere's law of electrodynamics in spheroidal oblate coordinates. This produces two asso\\-ciated Legendre equations of first order for the magnetic potential and hence that can be expressed as a series of associated Legendre functions of the same order. The discontinuity of its normal derivate across the disk allows us to interpret the source of the magnetic field as a ringlike current distribution extended on all the plane of the disk. We also study the circular speed curves or rotation curve for equatorial circular orbits of charged test particles both inside and outside the disk. The stability of the orbits is analyzed for radial perturbation using a extension of the Rayleigh criterion.
Hysteresis in Magnetic Shape Memory Composites: Modeling and Simulation
Conti, Sergio; Rumpf, Martin
2015-01-01
Magnetic shape memory alloys are characterized by the coupling between a structural phase transition and magnetic one. This permits to control the shape change via an external magnetic field, at least in single crystals. Composite materials with single-crystalline particles embedded in a softer matrix have been proposed as a way to overcome the blocking of the transformation at grain boundaries. We investigate hysteresis phenomena for small NiMnGa single crystals embedded in a polymer matrix for slowly varying magnetic fields. The evolution of the microstructure is studied within the rate-independent variational framework proposed by Mielke and Theil (1999). The underlying variational model incorporates linearized elasticity, micromagnetism, stray field and a dissipation term proportional to the volume swept by the phase boundary. The time discretization is based on an incremental minimization of the sum of energy and dissipation. A backtracking approach is employed to approximately ensure the global minimali...
A magnetospheric field model incorporating the OGO 3 and 5 magnetic field observations
NASA Technical Reports Server (NTRS)
Sugiura, M.; Poros, D. J.
1973-01-01
A magnetospheric field model is presented in which the usually assumed toroidal ring current is replaced by a circular disk current of finite thickness that extends from the tail to geocentric distances less than 3 earth radii. The drastic departure of this model from the concept of the conventional ring current lies in the fact that the current is continuous from the tail to the inner magnetosphere. This conceptual change was required to account for the recent results of analysis of the OGO 3 and 5 magnetic field observations. In the present model the cross-tail current flows along circular arcs concentric with the earth and completes circuit via surface currents on the magnetopause. Apart from these return currents in the tail magnetopause, Mead's model is used for the field from the magnetopause current. The difference scalar field, delta B, defined as the difference between the scalar field calculated from the present model and the magnitude of the dipole field is found to be in gross agreement with the observed delta B. An updated version of the delta B contours from the OGO 3 and 5 observations, which is used for the comparison, is presented.
Magnetic damping forces in figure-eight-shaped null-flux coil suspension systems
He, Jianliang; Coffey, H.
1997-08-01
This paper discusses magnetic damping forces in figure-eight-shaped null-flux coil suspension systems, focusing on the Holloman maglev rocket system. The paper also discusses simulating the damping plate, which is attached to the superconducting magnet by two short-circuited loop coils in the guideway. Closed-form formulas for the magnetic damping coefficient as functions of heave-and-sway displacements are derived by using a dynamic circuit model. These formulas are useful for dynamic stability studies.
HL Tau: 3-D Polarisation Modelling and Magnetic Field Structure
NASA Astrophysics Data System (ADS)
Lucas, P. W.; Fukagawa, M.; Tamura, M.; Chrysostomou, A.; Beckford, A. F.
2005-12-01
We describe 3-dimensional Monte Carlo modelling of HL Tau in the near infrared with aligned non-spherical grains. JHK linear polarimetry with 0.4-0.6 arcsec resolution from Subaru and UKIRT is fitted in detail, providing information about the structure of the system, the grain properties and perhaps also the magnetic field. Circular polarisation models are also presented, showing how near infrared circular polarimetry will provide the key to measuring magnetic field structure in protostars on the scale of the solar system, provided that circular polarimeters become available. This is illustrated with recently obtained circular polarimetry of the intermediate mass YSO HH135.
NASA Astrophysics Data System (ADS)
Okamoto, Yoshifumi; Tominaga, Yusuke; Sato, Shuji
The layout optimization with the ON-OFF information of magnetic material in finite elements is one of the most attractive tools in initial conceptual and practical design of electrical machinery for engineers. The heuristic algorithms based on the random search allow the engineers to define the general-purpose objects, however, there are many iterations of finite element analysis, and it is difficult to realize the practical solution without island and void distribution by using direct search method, for example, simulated annealing (SA), genetic algorithm (GA), and so on. This paper presents the layout optimization method based on GA. Proposed method can arrive at the practical solution by means of multi-step utilization of GA, and the convergence speed is considerably improved by using the combination with the reduction process of design space.
NASA Technical Reports Server (NTRS)
1986-01-01
Adflex Solutions, Inc.'s flexible circuits may be molded to the shape of a chassis for bulk reduction. Particularly valuable when circuitry must be moved. They are produced by combining a plastic film, a metallic conductor and an adhesive. One adhesive, LARC-TPI, developed by the Langley Research Center, is a thermoplastic polyimide resin used to produce laminates by Rogers Corporation. It can be processed at a lower temperature, has good moisture resistance and excellent adherence. It is used to bond film to copper foil conductor materials in flexible circuits. The circuits have both aerospace and commercial applications.
Testing the Maximum Magnetic Shear Model with THEMIS observations
NASA Astrophysics Data System (ADS)
Trattner, K. J.; Petrinec, S. M.; Fuselier, S. A.; Phan, T.
2012-12-01
Reconnection at the Earth's magnetopause is the mechanism by which magnetic fields in different regions change topology to create open magnetic field lines that allow energy and momentum to flow into the magnetosphere. One of the long standing questions about magnetic reconnection is the location of the reconnection line. There are two reconnection scenarios discussed in the literature: a) anti-parallel reconnection where shear angles between the magnetospheric field and the interplanetary magnetic field (IMF) are near 180°, and b) component reconnection where a tilted reconnection line which crosses the magnetopause in the sub-solar region at shear angles not near 180°. Early satellite observations were limited to the detection of accelerated ion beams in the magnetopause boundary layer to determine the general direction of the reconnection line location with respect to the satellite. An improved view of the reconnection location at the magnetopause was determined from ionospheric emissions observed by polar-orbiting imagers which revealed that both scenarios occur. The time-of-flight effect of precipitating ions in the cusp in connection with the low-velocity cutoff method pin-pointed reconnection locations and their dependency on IMF conditions. These results are summarized by the Maximum Magnetic Shear Model. This study uses confirmed magnetic reconnection locations from the THEMIS mission which observed accelerated ion flow reversals at the magnetopause to test the predictions of this reconnection location model. The results reveal that the Maximum Magnetic Shear model predicts the observed reconnection locations for dominant IMF BY conditions very well, but needs further improvement and modifications for dominant southward IMF conditions.
David, Allan E; Cole, Adam J; Chertok, Beata; Park, Yoon Shin; Yang, Victor C
2011-05-30
Magnetic nanoparticles (MNP) continue to draw considerable attention as potential diagnostic and therapeutic tools in the fight against cancer. Although many interacting forces present themselves during magnetic targeting of MNP to tumors, most theoretical considerations of this process ignore all except for the magnetic and drag forces. Our validation of a simple in vitro model against in vivo data, and subsequent reproduction of the in vitro results with a theoretical model indicated that these two forces do indeed dominate the magnetic capture of MNP. However, because nanoparticles can be subject to aggregation, and large MNP experience an increased magnetic force, the effects of surface forces on MNP stability cannot be ignored. We accounted for the aggregating surface forces simply by measuring the size of MNP retained from flow by magnetic fields, and utilized this size in the mathematical model. This presumably accounted for all particle-particle interactions, including those between magnetic dipoles. Thus, our "corrected" mathematical model provided a reasonable estimate of not only fractional MNP retention, but also predicted the regions of accumulation in a simulated capillary. Furthermore, the model was also utilized to calculate the effects of MNP size and spatial location, relative to the magnet, on targeting of MNPs to tumors. This combination of an in vitro model with a theoretical model could potentially assist with parametric evaluations of magnetic targeting, and enable rapid enhancement and optimization of magnetic targeting methodologies. PMID:21295085
Modelling parallel assemblies of porous materials using the equivalent circuit method.
Pieren, Reto; Heutschi, Kurt
2015-02-01
Recently, the accuracy of the parallel transfer matrix method (P-TMM) and the admittance sum method (ASM) in the prediction of the absorption properties of parallel assemblies of materials was investigated [Verdière, Panneton, Elkoun, Dupont, and Leclaire, J. Acoust. Soc. Am. 136, EL90-EL95 (2014)]. It was demonstrated that P-TMM is more versatile than ASM, as a larger variety of different backing configurations can be handled. Here it will be shown that the same universality is offered by the equivalent circuit method. PMID:25698040
Du, Ruoyang; Robertson, Paul
2014-12-18
to several kilohertz. B. Application of the Dynamic Jiles-Atherton Model to the Magnetic Loss of a PMSM (BLDC motor) According to Guo’s review paper, empirical formulae have been derived to model the magnetic properties under a rotating magnetic field... FEM [11], [26], [27] to utilize the proposed dynamic Jiles-Atherton model to estimate the magnetic power loss in a PMSM. More mathematical work needs to be done to make the dynamic Jiles-Atherton model and time stepped FEM compatible with each...
40 mm bore Nb-Ti model dipole magnet
Taylor, C.; Gilbert, W.; Hassenzahl, W.; Meuser, R.; Peters, C.; Rechen, J.; Scanlan, R.
1984-09-10
Preliminary R and D has been started on magnets for a next-generation high-energy-physics accelerator, the 20 TeV Superconducting Supercollider (SSC). One design now being developed at LBL is described in this paper. The design is based on two layers of flattened Nb-Ti cable, a 40 mm ID winding with flared ends, and an operating field of 6.5 T. Experimental results are presented on several one-meter-long models tested at both He I and He II temperature. Measurement of field, residual magnetization, quench propagation velocity, and winding prestress are presented. (A 2-in-1 magnet based on this coil design is being jointly developed by LBL and Brookhaven National Laboratory, and 15 ft. long models are being constructed at BNL).
PIG Ion Source with Permanent Magnets: Model Based Anode Current Return Circuit
NASA Astrophysics Data System (ADS)
Babapour Ghadikolaee, Mohammad Reza
2012-12-01
Ion sources are widely used in fusion technologies. A new high voltage pulsed power supply for use in penning ion gauge ion sources is proposed in this paper. To use discharge current, a diode-capacitor bank is included. The power supply is composed of 3 stages. A fast switching transistor is used as a single switch which is trigged by a pulse generator. A transformer is used to level up the voltage up to 2 kV without power loss. It is also used to isolate input and high voltage output. Also; the proposed high voltage power supply implementation uses a diode-capacitor bank whose capacitors are charged during plasma discharge. This system structure gives compactness and easiness to implement the total system which in combination with inexpensive commercially available components, makes the unit versatile and inexpensive.
Thrust and efficiency model for electron-driven magnetic nozzles
Little, Justin M.; Choueiri, Edgar Y.
2013-10-15
A performance model is presented for magnetic nozzle plasmas driven by electron thermal expansion to investigate how the thrust coefficient and beam divergence efficiency scale with the incoming plasma flow and magnetic field geometry. Using a transformation from cylindrical to magnetic coordinates, an approximate analytical solution is derived to the axisymmetric two-fluid equations for a collisionless plasma flow along an applied magnetic field. This solution yields an expression for the half-width at half-maximum of the plasma density profile in the far-downstream region, from which simple scaling relations for the thrust coefficient and beam divergence efficiency are derived. It is found that the beam divergence efficiency is most sensitive to the density profile of the flow into the nozzle throat, with the highest efficiencies occurring for plasmas concentrated along the nozzle axis. Increasing the expansion ratio of the magnetic field leads to efficiency improvements that are more pronounced for incoming plasmas that are not concentrated along the axis. This implies that the additional magnet required to increase the expansion ratio may be worth the added complexity for plasma sources that exhibit poor confinement.
Modeling and vector control of planar magnetic levitator
Kim, W.; Trumper, D.L.; Lang, J.H.
1998-11-01
The authors designed and implemented a magnetically levitated stage with large planar motion capability. This planar magnetic levitator employs four novel permanent-magnet linear motors. Each motor generates vertical force for suspension against gravity, as well as horizontal force for drive. These linear levitation motors can be used as building blocks in the general class of multi-degree-of-freedom motion stages. In this paper, the authors discuss electromechanical modeling and real-time vector control of such a permanent-magnet levitator. They describe the dynamics in a dq frame introduced to decouple the forces acting on the magnetically levitated moving part, namely, the platen. A transformation similar to the Blondel-Park transformation is derived for commutation of the stator phase currents. The authors provide test results on step responses of the magnetically levitated stage. It shows 5-nm rms positioning noise in x and y, which demonstrates the applicability of such stages in the next-generation photolithography in semiconductor manufacturing.
NASA Astrophysics Data System (ADS)
Bakkali, Hicham; Dominguez, Manuel; Batlle, Xavier; Labarta, Amílcar
2015-08-01
The ac response in the dielectric regime of thin films consisting of Pd nanoparticles embedded in a ZrO2 insulating matrix, fabricated by co-sputtering, was obtained from impedance spectroscopy measurements (11?Hz-2?MHz) in the temperature range 30-290?K. The response was fitted to an equivalent circuit model whose parameters were evaluated assuming that, as a consequence of the bimodal size distribution of the Pd particles, two mechanisms appear. At low frequencies, a first element similar to a parallel RC circuit dominates the response, due to two competing paths. One of them is associated with thermally-activated tunneling conductance among most of the smallest Pd particles (size ~ 2?nm), which make up the dc tunneling backbone of the sample. The other one is related to the conductance associated with the capacitive paths among larger Pd particles (size??>??5?nm). At low temperature and intermediate frequencies (~1?kHz), a shortcut process between the larger particles connects regions initially isolated from the backbone at low frequencies. These regions, populated by some additional smaller particles located around two bigger particles, were isolated because the bigger particles separation is too large for the tunneling current. Once connected to the backbone, current may also flow through them by means of the so-called thermally-activated assisted tunneling resistive paths, yielding the second element of the equivalent circuit (a parallel RLC element). At high temperature, the thermal energy shifts the onset of the shortcut process high frequencies and, thus, only the first element is observed. Considering these results, controlling the particle size distribution could be helpful to tune up the frequency at which tunneling conductance dominates the ac response of these granular metals.
A model of ocean basin crustal magnetization appropriate for satellite elevation anomalies
NASA Technical Reports Server (NTRS)
Thomas, Herman H.
1987-01-01
A model of ocean basin crustal magnetization measured at satellite altitudes is developed which will serve both as background to which anomalous magnetizations can be contrasted and as a beginning point for studies of tectonic modification of normal ocean crust. The model is based on published data concerned with the petrology and magnetization of the ocean crust and consists of viscous magnetization and induced magnetization estimated for individual crustal layers. Thermal remanent magnetization and chemical remanent magnetization are excluded from the model because seafloor spreading anomalies are too short in wavelength to be resolved at satellite altitudes. The exception to this generalization is found at the oceanic magnetic quiet zones where thermal remanent magnetization and chemical remanent magnetization must be considered along with viscous magnetization and induced magnetization.
ERIC Educational Resources Information Center
Ipek, Hava; Calik, Muammer
2008-01-01
Based on students' alternative conceptions of the topics "electric circuits", "electric charge flows within an electric circuit", "how the brightness of bulbs and the resistance changes in series and parallel circuits", the current study aims to present a combination of different conceptual change methods within a four-step constructivist teaching…
Thakore, Vaibhav; Molnar, Peter; Hickman, James J.
2014-01-01
Extracellular neuroelectronic interfacing is an emerging field with important applications in the fields of neural prosthetics, biological computation and biosensors. Traditionally, neuron-electrode interfaces have been modeled as linear point or area contact equivalent circuits but it is now being increasingly realized that such models cannot explain the shapes and magnitudes of the observed extracellular signals. Here, results were compared and contrasted from an unprecedented optimization based study of the point contact models for an extracellular ‘on-cell’ neuron-patch electrode and a planar neuron-microelectrode interface. Concurrent electrophysiological recordings from a single neuron simultaneously interfaced to three distinct electrodes (intracellular, ‘on-cell’ patch and planar microelectrode) allowed novel insights into the mechanism of signal transduction at the neuron-electrode interface. After a systematic isolation of the nonlinear neuronal contribution to the extracellular signal, a consistent underestimation of the simulated supra-threshold extracellular signals compared to the experimentally recorded signals was observed. This conclusively demonstrated that the dynamics of the interfacial medium contribute nonlinearly to the process of signal transduction at the neuron-electrode interface. Further, an examination of the optimized model parameters for the experimental extracellular recordings from sub- and supra-threshold stimulations of the neuron-electrode junctions revealed that ionic transport at the ‘on-cell’ neuron-patch electrode is dominated by diffusion whereas at the neuron-microelectrode interface the electric double layer (EDL) effects dominate. Based on this study, the limitations of the equivalent circuit models in their failure to account for the nonlinear EDL and ionic electrodiffusion effects occurring during signal transduction at the neuron-electrode interfaces are discussed. PMID:22695342
Circuit Complexity Circuit complexity is based on boolean circuits instead
Lyuu, Yuh-Dauh
Circuit Complexity · Circuit complexity is based on boolean circuits instead of Turing machines. · A boolean circuit with n inputs computes a boolean function of n variables. · Now, identify true/1 with "yes" and false/0 with "no." · Then a boolean circuit with n inputs accepts certain strings in { 0, 1 }n
Wind Tunnel Magnetic Suspension and Balance Systems With Transversely Magnetized Model Cores
NASA Technical Reports Server (NTRS)
Britcher, Colin P.
1998-01-01
This paper discusses the possibility of using vertically magnetized model cores for wind tunnel Magnetic Suspension and Balance Systems (MSBS) in an effort to resolve the traditional "roll control" problem. A theoretical framework is laid out, based on previous work related to generic technology development efforts at NASA Langley Research Center. The impact of the new roll control scheme on traditional wind tunnel MSBS configurations is addressed, and the possibility of demonstrating the new scheme with an existing electromagnet assembly is explored. The specific system considered is the ex- Massachusetts Institute of Technology (MIT), ex-NASA, 6-inch MSBS currently in the process of recommissioning at Old Dominion University. This system has a sufficiently versatile electromagnet configuration such that straightforward "conversion" to vertically magnetized cores appears possible.
RECONSTRUCTION OF HUMAN LUNG MORPHOLOGY MODELS FROM MAGNETIC RESONANCE IMAGES
Reconstruction of Human Lung Morphology Models from Magnetic Resonance Images
T. B. Martonen (Experimental Toxicology Division, U.S. EPA, Research Triangle Park, NC 27709) and K. K. Isaacs (School of Public Health, University of North Carolina, Chapel Hill, NC 27514)
Octet magnetic Moments and their sum rules in statistical model
M. Batra; A. Upadhyay
2013-12-18
The statistical model is implemented to find the magnetic moments of all octet baryons. The well-known sum rules like GMO and CG sum rules has been checked in order to check the consistency of our approach. The small discrepancy between the results suggests the importance of breaking in SU(3) symmetry.
Computer Aided Design and Modeling of High Frequency Magnetic Components *
Noé, Reinhold
approximately based on empirically derived core loss equations. Additionally the temperature of the transforComputer Aided Design and Modeling of High Frequency Magnetic Components * B. Becker H. Grotstollen University of Paderborn, FB 14 Power Electronics and Electrical Drives Pohlweg 47 33098 Paderborn, Germany
Testing Theoretical Models of Magnetic Damping Using an Air Track
ERIC Educational Resources Information Center
Vidaurre, Ana; Riera, Jaime; Monsoriu, Juan A.; Gimenez, Marcos H.
2008-01-01
Magnetic braking is a long-established application of Lenz's law. A rigorous analysis of the laws governing this problem involves solving Maxwell's equations in a time-dependent situation. Approximate models have been developed to describe different experimental results related to this phenomenon. In this paper we present a new method for the…
Consistent generation of magnetic fields in axion inflation models
Tomohiro Fujita; Ryo Namba; Yuichiro Tada; Naoyuki Takeda; Hiroyuki Tashiro
2015-04-15
There has been a growing evidence for the existence of magnetic fields in the extra-galactic regions, while the attempt to associate their origin with the inflationary epoch alone has been found extremely challenging. We therefore take into account the consistent post-inflationary evolution of the magnetic fields that are originated from vacuum fluctuations during inflation. In the model of our interest, the electromagnetic (EM) field is coupled to a pseudo-scalar inflaton $\\phi$ through the characteristic term $\\phi F\\tilde F$, breaking the conformal invariance. This interaction dynamically breaks the parity and enables a continuous production of only one of the polarization states of the EM field through tachyonic instability. The produced magnetic fields are thus helical. We find that the dominant contribution to the observed magnetic fields in this model comes from the modes that leave the horizon near the end of inflation, further enhanced by the tachyonic instability right after the end of inflation. The EM field is subsequently amplified by parametric resonance during the period of inflaton oscillation. Once the thermal plasma is formed (reheating), the produced helical magnetic fields undergo a turbulent process called inverse cascade, which shifts their peak correlation scales from smaller to larger scales. We consistently take all these effects into account within the regime where the perturbation of $\\phi$ is negligible and obtain $B_{\\rm eff} \\sim 10^{-19}$G, indicating the necessity of additional mechanisms to accommodate the observations.
Computational modeling of magnetically actuated propellant orientation
NASA Technical Reports Server (NTRS)
Hochstein, John I.
1996-01-01
Unlike terrestrial applications where gravity positions liquid at the 'bottom' of the tank, the location of liquid propellant in spacecraft tanks is uncertain unless specific actions are taken or special features are built into the tank. Some mission events require knowledge of liquid position prior to a particular action: liquid must be positioned over the tank outlet prior to starting the main engines and must be moved away from the tank vent before vapor can be released overboard to reduce pressure. It may also be desirable to positively position liquid to improve propulsion system performance: moving liquid away from the tank walls will dramatically decrease the rate of heat transfer to the propellant, suppressing the boil-off rate, thereby reducing overall mission propellant requirements. The process of moving propellant to a desired position is referred to as propellant orientation or reorientation. Several techniques have been developed to positively position propellant in spacecraft tanks and each technique imposes additional requirements on vehicle design. Propulsive reorientation relies on small auxiliary thrusters to accelerate the tank. The inertia of the liquid causes it to collect in the aft-end of the tank if the acceleration is forward. This technique requires that additional thrusters be added to the vehicle, that additional propellant be carried in the vehicle, and that an additional operational maneuver be executed. Another technique uses Liquid Acquisition Devices (LAD's) to positively position propellants. These devices rely on surface tension to hold the liquid within special geometries (i.e. vanes, wire-mesh channels, start-baskets). While avoiding some of the penalties of propulsive orientation, this technique requires the addition of complicated hardware inside the propellant tank and performance for long duration missions is uncertain. The subject of the present research is an alternate technique for positively positioning liquid within spacecraft propellant tanks: magnetic fields.
Leach Jr.,W. Marshall
Thévenin Emitter Circuit The Thévenin equivalent circuit seen looking into the emitter is useful. With the emitter open circuited, we denote the emitter voltage by ve(oc). The voltage source in the Thévenin emitter circuit has this value. To solve for it, we use the simplified T model in Fig. 1(b). Figure 1: (a
Ville Bergholm; Jacob D. Biamonte
2011-05-29
In this paper, we extend past work done on the application of the mathematics of category theory to quantum information science. Specifically, we present a realization of a dagger-compact category that can model finite-dimensional quantum systems and explicitly allows for the interaction of systems of arbitrary, possibly unequal, dimensions. Hence our framework can handle generic tensor network states, including matrix product states. Our categorical model subsumes the traditional quantum circuit model while remaining directly and easily applicable to problems stated in the language of quantum information science. The circuit diagrams themselves now become morphisms in a category, making quantum circuits a special case of a much more general mathematical framework. We introduce the key algebraic properties of our tensor calculus diagrammatically and show how they can be applied to solve problems in the field of quantum information.
Global Quantum Circuit Optimization
Raphael Dias da Silva; Einar Pius; Elham Kashefi
2013-01-02
One of the main goals in quantum circuit optimisation is to reduce the number of ancillary qubits and the depth of computation, to obtain robust computation. However, most of known techniques, based on local rewriting rules, for parallelising quantum circuits will require the addition of ancilla qubits, leading to an undesired space-time tradeoff. Recently several novel approaches based on measurement-based quantum computation (MBQC) techniques attempted to resolve this problem. The key element is to explore the global structure of a given circuit, defined via translation into a corresponding MBQC pattern. It is known that the parallel power of MBQC is superior to the quantum circuit model, and hence in these approaches one could apply the MBQC depth optimisation techniques to achieve a lower depth. However, currently, once the obtained parallel pattern is translated back to a quantum circuit, one should either increase the depth or add ancilla qubits. In this paper we characterise those computations where both optimisation could be achieved together. In doing so we present a new connection between two MBQC depth optimisation procedures, known as the maximally delayed generalised flow and signal shifting. This structural link will allow us to apply an MBQC qubit optimisation procedure known as compactification to a large class of pattern including all those obtained from any arbitrary quantum circuit. We also present a more efficient algorithm (compared to the existing one) for finding the maximally delayed generalised flow for graph states with flow.
Magnetic moments of heavy baryons in the bag model reexamined
Andrius Bernotas; Vytautas Šimonis
2012-09-13
Magnetic moments of J = 1/2 and J = 3/2 heavy baryons are calculated in the bag model with center-of-mass motion corrections. For the spin 1/2 baryons containing three quarks of different flavours the effect of hyperfine mixing is examined in detail. The results of the work are compared with predictions obtained in various other approaches and models.
Circuit implementation of a theoretical model of trap centres in GaAs and GaN devices
NASA Astrophysics Data System (ADS)
Rathmell, James G.; Parker, Anthony E.
2007-12-01
A novel and simple circuit implementation of trap centres in GaAs and GaN HEMTs, MESFETs and HFETs is presented. When included in transistor models it explains the potential-dependent time constants seen in the circuit manifestations of charge trapping, being gate lag and drain overshoot. The implementation is suitable for both time- and harmonic-domain simulations. The trap-centre model is based on Shockley-Read-Hall (SRH)1 statistics of the trapping process. It also accommodates carrier injection from other important device effects, such as impact ionization and light sensitivity. In the model, the ionization charge of the trap centre is represented by the charge in a capacitor. The potential across the capacitor is proportional to the potential across the region of the trap centre in the semiconductor. It is positive or negative depending on the polarity of the ionization charge - electrons or holes. When included in a transistor model, this potential is added to the gate potential that controls the drain-current description. The capacitor is charged or discharged by two opposing currents that are functions of the ionization potential and temperature: one models charge emission; and the other, which is also controlled by an external potential and injected current, models charge capture. The external potential is typically a linear function of a transistor's terminal potentials. The injection current can model charge generated by light or by holes from impact ionization. The four parameters for the model are simply the signed potential of the trap centre when fully ionized, the time constant for charge emission at a specific temperature, the injection-current sensitivity, and the activation energy of the emission process. The latter is used to predict the temperature dependence of the emission rate. The capture rate is determined within the model by an exponential function of the external potential that controls capture. Thus the model elegantly predicts asymmetry between trap charging and discharging rates. The model accounts for variation in emission and capture rates with temperature, which is shown to vary significantly over typical transistor operating ranges.
Modeling Detached Magnetic Structures in the Inner Heliosphere
NASA Astrophysics Data System (ADS)
Odstrcil, Dusan; Vandas, Marek
2015-04-01
Currently, the WSA-ENLIL-Cone modeling system is used by various space weather agencies for operational forecasting of corotating and transient solar wind disturbances in the inner heliosphere. This modeling system provides global context and arrival times of the solar wind streams and coronal mass ejections (CMEs) to Earth, planets, and spacecraft. Such predictions are running continuously and much faster than real time. However, CME-like disturbances are generated by launching hydrodynamic transients and thus it is not possible to predict the southward magnetic field (-Bz). In this presentation, we a 3-D analytic model of the magnetic spheromak, launch it into the background solar wind at 0.1 AU and simulate their evolution in the inner heliosphere as the first step in modeling more realistic transient disturbances. Main advantage above hydrodynamic ejecta is in smaller distortion/comperssion due to magnetic field tension and in more reslistic density profiles. This modeling system would enable routine operational modeling of the heliospheric space weather event-by-event and faster than real-time.
Computational modeling of ``MAGO`` and other magnetized target fusion concepts
Lindemuth, I.R.; Kirkpatrick, R.C.; Reinovsky, R.E.; Sheehey, P.T.; Thurston, R.S.; Wysocki, F.J.
1993-02-01
One possible way to obtain a preheated and magnetized plasma suitable for subsequent implosion is the ``MAGO`` concept. The unique MAGO discharge consists of a two chambers, with electrical current flowing in one chamber accelerating plasma flow into an implosion chamber. Up to 4 {times} 10{sup 13} D-T neutrons have been produced in the MAGO discharge. In this paper, we discuss our computational modeling of MAGO. Our objectives are to characterize the plasma, compare with the limited diagnostics available, and to understand the neutron production. We also discuss, briefly, some other possible means for creating a magnetized plasma.
Computational modeling of MAGO'' and other magnetized target fusion concepts
Lindemuth, I.R.; Kirkpatrick, R.C.; Reinovsky, R.E.; Sheehey, P.T.; Thurston, R.S.; Wysocki, F.J.
1993-01-01
One possible way to obtain a preheated and magnetized plasma suitable for subsequent implosion is the MAGO'' concept. The unique MAGO discharge consists of a two chambers, with electrical current flowing in one chamber accelerating plasma flow into an implosion chamber. Up to 4 [times] 10[sup 13] D-T neutrons have been produced in the MAGO discharge. In this paper, we discuss our computational modeling of MAGO. Our objectives are to characterize the plasma, compare with the limited diagnostics available, and to understand the neutron production. We also discuss, briefly, some other possible means for creating a magnetized plasma.
Numerical Modeling of a Magnetic Flux Compression Experiment
NASA Astrophysics Data System (ADS)
Makhin, Volodymyr; Bauer, Bruno S.; Awe, Thomas J.; Fuelling, Stephan; Goodrich, Tasha; Lindemuth, Irvin R.; Siemon, Richard E.; Garanin, Sergei F.
2007-06-01
A possible plasma target for Magnetized Target Fusion (MTF) is a stable diffuse z-pinch in a toroidal cavity, like that in MAGO experiments. To examine key phenomena of such MTF systems, a magnetic flux compression experiment with this geometry is under design. The experiment is modeled with 3 codes: a slug model, the 1D Lagrangian RAVEN code, and the 1D or 2D Eulerian Magneto-Hydro-Radiative-Dynamics-Research (MHRDR) MHD simulation. Even without injection of plasma, high- Z wall plasma is generated by eddy-current Ohmic heating from MG fields. A significant fraction of the available liner kinetic energy goes into Ohmic heating and compression of liner and central-core material. Despite these losses, efficiency of liner compression, expressed as compressed magnetic energy relative to liner kinetic energy, can be close to 50%. With initial fluctuations (1%) imposed on the liner and central conductor density, 2D modeling manifests liner intrusions, caused by the m = 0 Rayleigh-Taylor instability during liner deceleration, and central conductor distortions, caused by the m = 0 curvature-driven MHD instability. At many locations, these modes reduce the gap between the liner and the central core by about a factor of two, to of order 1 mm, at the time of peak magnetic field.
Bifurcation Model for the Onset of Fast Magnetic Reconnection
NASA Astrophysics Data System (ADS)
Cassak, Paul; Drake, James; Shay, Michael; Eckhardt, Bruno
2006-04-01
The mechanism triggering the onset of fast magnetic reconnection, the driver of solar eruptions and fusion device disruptions, has long been elusive. A catastrophe model for the explosive onset of fast magnetic reconnection has been proposed. The crux of the model is that both the Sweet-Parker and Hall reconnection solutions are valid when the Sweet-Parker current sheet is thicker than the ion inertial length di, but the Sweet-Parker solution disappears catastrophically when the layer thins below di. Simulations confirm that the thinning of the current sheet occurs naturally during reconnection as convection increases the magnetic field just upstream of the dissipation region, eventually leading to explosive onset. We interpret the disappearance of the Sweet-Parker solution as a saddle-node bifurcation and confirm its signatures with simulations. Earlier numerical results have been extended to include a guide field. We explore the model's potential impact on the explosive onset of magnetic reconnection in solar eruptions and sawtooth crashes.
A Spatial Computing Architecture for Implementing Computational Circuits
Lemieux, Guy
A Spatial Computing Architecture for Implementing Computational Circuits David Grant and Guy G. F- rithms, designers are implementing them as computational circuits. These algorithms are diverse and include molecular dynamics, weather simulation, video encoding, and financial modelling. Circuit designers
Dynamics of Permanent-Magnet Biased Active Magnetic Bearings
NASA Technical Reports Server (NTRS)
Fukata, Satoru; Yutani, Kazuyuki
1996-01-01
Active magnetic radial bearings are constructed with a combination of permanent magnets to provide bias forces and electromagnets to generate control forces for the reduction of cost and the operating energy consumption. Ring-shaped permanent magnets with axial magnetization are attached to a shaft and share their magnet stators with the electromagnets. The magnet cores are made of solid iron for simplicity. A simplified magnetic circuit of the combined magnet system is analyzed with linear circuit theory by approximating the characteristics of permanent magnets with a linear relation. A linearized dynamical model of the control force is presented with the first-order approximation of the effects of eddy currents. Frequency responses of the rotor motion to disturbance inputs and the motion for impulsive forces are tested in the non-rotating state. The frequency responses are compared with numerical results. The decay of rotor speed due to magnetic braking is examined. The experimental results and the presented linearized model are similar to those of the all-electromagnetic design.
Model for charged dust expansion across a magnetic field
NASA Astrophysics Data System (ADS)
Fu, H.; Scales, W. A.
2013-07-01
Plasma fluctuations arise in the boundary region between charged dust clouds and background plasmas. A self-consistent computational model is developed to study expansion of a charged dust cloud across a magnetic field, creation of the inhomogeneous boundary layer and associated processes. The charging of the dust particulates produces a boundary layer and associated ambipolar electric field. This ambipolar field provides a source for low frequency dust acoustic waves in unmagnetized plasmas. A background magnetic field if sufficiently strong, may impact the dust acoustic wave evolution and dust density structures due to E ×B and diamagnetic current generation. The dust acoustic density fluctuation generation across a strong magnetic field (?pe/?ce?1) may be suppressed as compared to an unmagnetized dusty plasma, which will be discussed. Fluctuations generated at longer timescales propagating along the dust boundary layer will also be investigated in the lower hybrid and dust lower hybrid frequency range. Applications to space and laboratory plasmas are discussed.