Finite-element analysis of magnetotransistor action

In this Letter, a novel vertical bipolar junction transistor (BJT) triggered silicon‐controlled rectifier (VBTSCR) is proposed for advanced nanoscale electrostatic discharge (ESD) protection applications. With the help of a vertical NPN transistor in floating base configuration, the new silicon‐controlled rectifier (SCR) structure achieves lower trigger voltage and better clamping capacity than the prior enhanced modified lateral SCR (EMLSCR) under the same layout footprint. The ESD characteristics are measured using the transmission line pulsing tester. Compared with that of EMLSCR, the trigger voltage of VBTSCR drops by 1 V, and the effective ESD robustness of VBTSCR has been doubled significantly. Based on these advantages, the proposed VBTSCR can provide ESD protection for the advanced 1.8/2.5 V input/output circuits more efficiently.

We have to admit that the literature concerning bioeffects of electromagnetic fields is replete with reports that cannot be reproduced in other labs. Besides the intended or sub-conscious experimenter bias, which can be avoided or much reduced by the gold standard of blinded analysis, most inconsistences in the literature were actually caused by confounding effects, different magnetic field parameters, and biological sample differences. The goal of this chapter is to summarize the factors that contribute to the differential bioeffects of static magnetic fields (SMFs), including magnetic field exposure parameters, such as magnetic field types, magnetic flux density, homogeneousness, field direction and distribution, exposure time, as well as biological sample differences, including cell type, cell density, cell status, and other factors. It is clear that all these aspects are crucial for the diverse effects of SMFs on biological samples, which also lead to the seemingly lack of consistencies in literature. Therefore, we encourage people to not only perform double blinded analysis in independent studies, but also clearly describe the experimental details, including various magnetic field exposure parameters, biological samples, and experimental procedures. This will be crucial for people to perform further subjective analysis and mechanistic investigations.KeywordsMagnetic field (MF)Static magnetic fields (SMFs)Time-varying magnetic field (TVMF)Dynamic magnetic field (DMF)Magnetic field intensityGradient magnetic fields (GMF)Differential effects of magnetic fields

To improve the value of β of a pnp-merged vertical bipolar transistor (VBT) in ‘pseudo-BiCMOS’ technology, a novel VBT design with an inversion layer-extended emitter is proposed. A high emitter injection efficiency of the forward-biased inversion layer is demonstrated in a pnp VBT fabricated in 1 µm compensated CMOS technology.

view Abstract Citations (9) References (5) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Effect of a Vertical Magnetic Field on the Propagation of Gravity Waves Along the Plane Surface of a Semi-Infinite Viscous, Electrically Conducting Fluid. Roberts, P. H. ; Boardman, A. D. Abstract The basic equations and boundary conditions governing the effect of vertical magnetic and gravitational fields on small-amplitude perturbations of the free equilibrium surface of a viscous, electrically conducting fluid are presented Normal modes are examined. A dispersion relationship is derived which relates the complex "frequency" n of the normal mode to the Allven velocity, V, the viscosity, , the magnetic diffusivity, X, and the horizontal wave number, k. This dispersion relationship is solved in nine extreme cases In six of these, the magnetic field is too weak to modify substantially the familiar gravity- wave solution holding in the absence of a magnetic field. The influence of the field is so strong in the remaining three cases that they have no parallel in the zero-field case One of these holds for any k if the magnetic field is sufficiently strong In this case n = gV-l(X/ l/2 i e, the effect of the magnetic field is so great that the disturbance is attenuated aperiodically as the Aliven waves radiate energy away from the free surface. Another interesting feature demonstrated is the existence (if V is sufficiently large) of a band of wave numbers k for which no normal-mode solution exists It is nevertheless demonstrated that the associated initial-value problem can be solved for such values of k. In addition to the nine extreme cases mentioned above, three special cases are solved for all k for particular values of V, namely, p = p = 0, and X = 0. Publication: The Astrophysical Journal Pub Date: March 1962 DOI: 10.1086/147291 Bibcode: 1962ApJ...135..552R full text sources ADS |

Time-dependent Ginzburg–Landau equations were solved by the finite difference scheme for a superconducting sample in steady and oscillating magnetic fields for 3D geometry. The dynamic behaviour of penetrating and leaving magnetic vortices in superconductor with the oscillating magnetic field was simulated. Carrier concentration density and the average magnetization of the sample were studied as a function of the external oscillating magnetic field. Anomalies in carrier concentrations at certain magnetic field values were observed and discussed. It was also observed that the area swept by magnetization versus external magnetic field is magnetic oscillation frequency dependent, which increases with increasing frequencies. It was suggested that this effect may cause instability in the superconducting characteristics of the sample over a number of cycles. Calculated energy patterns showed consistency with vortex patterns in the steady magnetic field. Magnetic oscillations initiated oscillations in energy components, ripples in superconducting energy are subjected to the entrance and leaving of vortices, while instability observed in interaction energy is referred to vortex relaxation time.

A self-aligned vertical Bipolar Charge Plasma Transistor (V-BCPT) with a buried metal layer between undoped silicon and buried oxide of the silicon-on-insulator substrate, is reported in this paper. Using two-dimensional device simulation, the electrical performance of the proposed device is evaluated in detail. Our simulation results demonstrate that the V-BCPT not only has very high current gain but also exhibits high BVCEO · fT product making it highly suitable for mixed signal high speed circuits. The proposed device structure is also suitable for realizing doping-less bipolar charge plasma transistor using compound semiconductors such as GaAs, SiC with low thermal budgets. The device is also immune to non-ideal current crowding effects cropping up at high current densities.

Effects of high magnetic field annealing on microstructure and multiferroic properties of Bi1−xLaxFeO3 ceramics

In time – distance helioseismology, wave travel times are measured from the cross-correlation between Doppler velocities recorded at any two locations on the solar surface. However, one of the main uncertainties associated with such measurements is how to interpret observations made in regions of strong magnetic field. Isolating the effects of the magnetic field from thermal or sound-speed perturbations has proved to be quite complex and has yet to yield reliable results when extracting travel times from the cross-correlation function. One possible way to decouple these effects is by using a 3D sunspot model based on observed surface magnetic-field profiles, with a surrounding stratified, quiet-Sun atmosphere to model the magneto-acoustic ray propagation, and analyse the resulting ray travel-time perturbations that will directly account for wave-speed variations produced by the magnetic field. These artificial travel-time perturbation profiles provide us with several related but distinct observations: i) that strong surface magnetic fields have a dual effect on helioseismic rays – increasing their skip distance while at the same time speeding them up considerably compared to their quiet-Sun counterparts, ii) there is a clear and significant frequency dependence of both skip-distance and travel-time perturbations across the simulated sunspot radius, iii) the negative sign and magnitude of these perturbations appears to be directly related to the sunspot magnetic-field strength and inclination, iv) by “switching off” the magnetic field inside the sunspot, we are able to completely isolate the thermal component of the travel-time perturbations observed, which is seen to be both opposite in sign and much smaller in magnitude than those measured when the magnetic field is present. These results tend to suggest that purely thermal perturbations are unlikely to be the main effect seen in travel times through sunspots, and that strong, near-surface magnetic fields may be directly and significantly altering the magnitude and lateral extent of sound-speed inversions of sunspots made by time – distance helioseismology.KeywordsHelioseismology, direct modellingSunspots, magnetic fieldsMagnetic fields, models

In this paper we describe, analyse and implement a parallel iterative method for the solution of the steady-state drift diffusion equations governing the behaviour of a semiconductor device in two space dimensions. The unknowns in our model are the electrostatic potential and the electron and hole quasi-Fermi potentials. Our discretisation consists of a finite element method with mass lumping for the electrostatic potential equation and a hybrid finite element with local current conservation properties for the continuity equations. A version of Gummel's decoupling algorithm which only requires the solution of positive definite symmetric linear systems is used to solve the resulting nonlinear equations. We show that this method has an overall rate of convergence which only degrades logarithmically as the mesh is refined. Indeed the (inner) nonlinear solves of the electrostatic potential equation converge quadratically, with a mesh independent asymptotic constant. We also describe an implementation on a MasPar MP-1 data parallel machine, where the required linear systems are solved by the preconditioned conjugate gradient method. Domain decomposition methods are used to parallelise the required matrix-vector multiplications and to build preconditioners for these very poorly-conditioned systems. Our preconditioned linear solves also have a rate of convergence which degrades logarithmically as the grid is refined relative to subdomain size, and their performance is resilient to the severe layers which arise in the coefficients of the underlying elliptic operators. Parallel experiments are given.

In this paper, both electric field and magnetic field were used to assist the hot filament chemical vapor deposition (HFCVD) and we systematically investigated the effects of which on the (1) phase composition, (2) grain size, (3) thickness and (4) preferred orientation of diamond films through SEM, Raman and XRD. The application of magnetic field in electric field, so called ‘the magnetic and electric coupling fields’, enhanced the graphitization and refinement of diamond crystals, slowed down the decrease of film thickness along with the increase of bias current, and suppressed diamond (100) orientation. During the deposition process, the electric field provided additional energy to HFCVD system and generated large number of energetic particles which might annihilate at the substrate and lose kinetic energy, while the Lorentz force, provided by magnetic field, could constrict charged particles (including electrons) to do spiral movement, which prolonged their moving path and life, thus the system energy increased. With the graphitization of diamond films intensified, the preferred orientation of diamond films completely evolved from (110) to (100), until the orientation and diamond phase disappeared, which can be attributed to (I) the distribution and concentration ratio of carbon precursors (C2H2 and CH3) and (II) graphitization sequence of diamond crystal facets. Since the electron field emission property of carbon film is sensitive to the phase composition, thickness and preferred orientation, nano- carbon cones, prepared by the negative bias current of 20 mA and magnetic field strength of 80 Gauss, exhibited the lowest turn-on field of 6.1 V −1 μm−1.

The mean-field induction equation ∂ t B ¯ − η Δ B ¯ = ∇ × F is considered in a conducting volume V , where B ¯ is the mean magnetic field, ∂ t is rate of change and η is magnetic diffusivity. Using the Green's function method and the second-order correlation approximation (SOCA), or the nearly axisymmetric methods of Braginskii [Self excitation of a magnetic field during the motion of a highly conducting fluid. Sov. Phys. JETP 1964, 20], then the electromotive force F is F = α ⋅ B ¯ . This work consists of two parts. Part I: The following antidynamo theorem (ADT) is derived: if there is no generation of azimuthal F from azimuthal B ¯ , that is 1 ϕ ⋅ α ⋅ 1 ϕ = α ϕϕ = 0 , where 1 ϕ is the unit vector in the ϕ direction, ( s , ϕ , z ) cylindrical polar coordinates, then an axisymmetric magnetic field ( B ¯ ( s , z ) ) will decay. Firstly, the magnetic field in meridional planes is shown to decay to zero. Then the azimuthal component of the magnetic field is shown to decay. As a weighted measure of the magnetic energy, ‖ b ‖ 2 = ∫ V b 2 d V , where b = B ¯ ( s , ϕ ) ⋅ 1 ϕ / s , is considered. The resulting ‖ b ‖ 2 magnetic energy analysis demonstrates that; for α = α ( s , z ) , and α ϕϕ = 0 , once the meridional field has decayed, diffusion decreases energy to more than account for the inductive contributions due to α , and, consistent with the α ϕϕ = 0 ADT, the field decays. Numerical results and field plots using the model α = s 1 z 1 ϕ , illustrate the interaction mechanisms responsible for the diffusive dominance as induction is increased. Using the SOCA and Green's function analysis, an explicit formulation for α ϕϕ is derived. Thus, physical mechanisms for the generation of α ϕϕ are established. Conditions are produced for which α ϕϕ = 0 , including a conductor filling all space with zero mean flow and co-axisymmetric perturbation flow and mean magnetic field. Part II: The Eulerian approach of Braginskii (1964), where the fields are analysed as perturbations from axisymmetry, is extended to compressible velocity fields for appropriate stellar and planetary dynamos. The hybrid Euler–Lagrange approach of Soward and Roberts [Eulerian and Lagrangian means in rotating, magnetohydrodynamic flows II. Braginsky's nearly axisymmetric dynamo. Geophys. Astrophys. Fluid Dyn. 2014, 108], following Soward [A kinematic theory of large magnetic Reynolds number dynamos. Phil. Trans. R. Soc. A 1972, 272], is continued to compressible flow and non-isochoric transformations in cylindrical polar coordinates, producing results that can be used for more general, higher-order approximations. These compressible extensions produce an α ϕϕ component and other effects for a reformulation of the problem into new effective mean, magnetic and velocity fields. Each of these approaches provides insight into mechanisms responsible for generating this critical α ϕϕ component. Common to all these approaches is the induction mechanism generated by the non-zero mean helicity of the meridional perturbation velocity field. Conclusions for non-magnetic stars are proposed and implications for hidden dynamos are drawn.

We re-examined the four-dimensional spacetime formulation of invariance of electromagnetic fields between two inertial frames under Lorentz transformation, which predicts a pure electric (magnetic) field in one inertial frame is composed the Cartesian components of a pure both electric and magnetic fields in another inertial frame. This contradicts the Lorentz invariance condition which requires that the vector quantities in one inertial frame must have the same form in another inertial frame. In this work, we introduce a three-dimensional quasi-time vector to modify the classical four-dimensional spacetime (3+1) to a new six-dimensional spacetime (3+3) and derive spacetime metric equation and relativistic velocity. We use the classical vector transformation theory to derive expressions for Cartesian components of relativistic velocity and net electromagnetic force vectors. Considering two massive inertial frames form a closed system, we integrated the transformed relativistic velocity with the law of conservation of energy to prove that contrary to the common belief, the electromagnetic field that appears as a purely electric (magnetic) field in one massive inertial frame, it also appears as a pure electric (magnetic) field in another massive inertial frame under Lorentz transformation. As an application of the proposed six-dimensional spacetime theory, we prove Lorentz invariance of Maxwell’s equations with and without charge and current source. We also prove the scalar electromagnetic wave equations with and without charge and current source and the conservation laws of the continuity equations of current and densities of electromagnetic energy and linear and angular momentums between two massive inertial frames under Lorentz transformation.

A large negative magnetoresistance (NMR) is anticipated in topological semimetals in parallel magnetic fields, demonstrating the chiral anomaly, a long-sought high-energy-physics effect, in solid-state systems. Recent experiments reveal that the Dirac semimetal Cd3As2 has the record-high mobility and positive linear magnetoresistance in perpendicular magnetic fields. However, the NMR has not yet been unveiled. Here we report the observation of NMR in Cd3As2 microribbons in parallel magnetic fields up to 66% at 50 K and visible at room temperatures. The NMR is sensitive to the angle between magnetic and electrical fields, robust against temperature and dependent on the carrier density. The large NMR results from low carrier densities in our Cd3As2 samples, ranging from 3.0 × 1017 cm−3 at 300 K to 2.2 × 1016 cm−3 below 50 K. We therefore attribute the observed NMR to the chiral anomaly. In perpendicular magnetic fields, a positive linear magnetoresistance up to 1,670% at 14 T and 2 K is also observed.

Probing into the effects of a magnetic field on the electrode processes of iron in sulphuric acid solutions with dichromate based on the fundamental electrochemistry kinetics

Introduction. When heating with high-frequency currents (HFCs) at high speeds, more significant strengthening effects can be observed compared to using machine generators. Therefore, hardening at high frequencies is more efficient. However, the increase in the generator frequency results in a decrease in the depth of penetration of eddy currents and an increased unevenness of heating across the cross-section. The application of a constant external magnetic field during HFC hardening can increase the depth of eddy current penetration and create more uniform heating. Unfortunately, there is not enough information available on the effect of the external magnetic field on HFC heating processes and phase transformations in steel. Currently, there are no quantitative estimates for the impact of an external magnetic field on changes in the kinetics of electric heating and the penetration depth of eddy currents. In connection with the above, the aim of this paper is to investigate changes in the kinetics of high-frequency heating of iron-carbon alloys when an external constant magnetic field is applied and, and, based on this, to consider the potential for technological applications. Materials and Methods. Theoretical assessment of the influence of an external magnetic field on the change in the kinetics of electric heating and the penetration depth of eddy currents is based on the general theory of induction heating kinetics. An experimental study of the influence of a magnetic field on the kinetics of high-frequency current heating was performed on samples of 45 steel, pearlitic gray (SCh30), and ferritic malleable cast iron (KCh30-6). The temperature distribution over the cross-section of ferromagnetic materials during induction heating with an external magnetic field has been studied using special samples of iron, 45 steel, and SCh30 gray pearlitic cast iron. Electric tempering processes have been investigated on samples of U8A steel using a vacuum tube generator (heating temperature — 450℃, heating rate — 750℃/s). Changes in austenite grain size after high-speed heating with external magnetization have been examined on samples of reduced-hardenability 55PP steel. To study the processes of thermal treatment in a magnetic field during experiments involving heating samples using high-frequency currents, a specially designed electromagnet was created to apply an external constant magnetic field. Results. Theoretical curves were constructed for heating conditions with and without an external constant magnetic field. Experimental data on the effect of an external constant magnetic field on induction heating in the surface layer of various materials were summarized in kinetic diagrams. Evidence that the observed changes were due to increased depth of penetration of eddy currents came from experiments on cylindrical samples of 45 steel with different wall thicknesses. Kinetic curves were provided for estimating the temperature field (at 6 points at different depths) during high-frequency current heating with and without external magnetization. The paper presents experimental data on the micro-hardness distribution across the cross-section of a U8 steel sample after quenching, quenching and electric tempering, quenching and electric tempering with external magnetization, and quenching and bulk tempering. It also includes the results of the study of the austenite grain size of 55PP steel after high-speed heating with external magnetization and conventional (slow) deep heating. Discussion. The application of a high-intensity external constant magnetic field during the first quasi-stationary process resulted in a decrease in the rate of induction heating of the ferromagnetic material and an increase in the depth of its uniform heating. However, above the Curie point, the effect of the magnetic field was negligible due to the low magnetic susceptibility of the material, and the heating rate remained unchanged as if there was no field present. In addition, due to the insignificant difference in the values of magnetic permeability below and above the Curie point during heating in the field, the thermal curve did not exhibit the characteristic inflection typical of kinetic curves observed during the transition of the surface layer to a paramagnetic state. Experiments with electric tempering have demonstrated that by applying an external field, it was possible to temper a material to the desired depth and it could be done on a single high-frequency current setup. The size of the austenite grains after high-speed heating with magnetization was reduced compared to conventional deep heating of steel with low hardenability, eliminating the issue of induction heating for low-hardenability steel. Conclusion. The results of the study demonstrated that the use of an external magnetic field enabled the achievement of strengthening effects during heating at higher frequencies, thereby eliminating the drawbacks of such heating methods.