Hasil untuk "Electricity and magnetism"

Han Lin Shang, Lin Han, Stefan Trück

Electricity demand and generation have become increasingly unpredictable with the growing share of variable renewable energy sources in the power system. Forecasting electricity supply by fuel mix is crucial for market operation, ensuring grid stability, optimizing costs, integrating renewable energy sources, and supporting sustainable energy planning. We introduce two statistical methods, centering on forecast reconciliation and compositional data analysis, to forecast short-term electricity supply by different types of fuel mix. Using data for five electricity markets in Australia, we study the forecast accuracy of these techniques. The bottom-up hierarchical forecasting method consistently outperforms the other approaches. Moreover, fuel mix forecasting is most accurate in power systems with a higher share of stable fossil fuel generation.

Haidar Al-Naseri

The interaction of strong electromagnetic fields with plasma generates radiation accompanied by a recoil force, which can significantly alter the plasma dynamics. In this work, we investigate the development of anisotropic momentum distributions induced by the combined action of electric and magnetic fields on a thermally relativistic plasma. We consider three distinct types of anisotropy. The first arises from a pure magnetic field acting on plasma with either isotropic or anisotropic initial momentum distributions, producing the characteristic ring-shaped momentum profile. The second is driven by a pure electric field, where radiation reaction generates a partial, anisotropic ring distribution in momentum space: significant modifications occur primarily in the 90$^\circ$--180$^\circ$ and 270$^\circ$--360$^\circ$ sectors of the $p_x$--$p_y$ plane, while the remaining quadrants remain largely unaffected. The third case considers the combined effect of electric and magnetic fields. When the cyclotron frequency is very close to the upper hybrid frequency, the azimuthal symmetry of the ring-momentum distribution is broken. Conversely, in the regime where the cyclotron frequency is lower than the upper hybrid frequency, the rapid oscillations of the electric field dominate and preserve the symmetry of the ring-momentum distribution.

Mahboobe Sehati, Ali Soltanmanesh, Shabnam Abutalebi et al.

Photoreduction of cryptochrome protein in the retina is a well-known mechanism of navigation of birds through the geomagnetic field, yet the biosignal nature of the mechanism remains unclear. The absorption of blue light by the flavin adenine dinucleotide (FAD) chromophore can alter the distribution of electrons in cryptochrome and create radical pairs with separated charges. In this study, the spin dynamics of electrons in the radical pair and its coupling with spatial position were investigated by computational modeling from a quantum mechanical perspective. Several interactions were considered in the presence of an external magnetic field, and the resulting electric dipole moment in cryptochrome was computed as the quantity emerging from this coupling. The computations show the induced electric dipole moment clearly depend on the characteristics of the applied magnetic field even after considering dissipative effects. In fact, our findings indicate that the radical pair in cryptochrome protein is a magnetic biosensor, in the sense that in the presence of the geomagnetic field, variations in spin states can influence its electric dipole moment, which may be interpreted via the bird as an orientation signal. The results can be used in the advancement of bio-inspired technologies which replicate animal magnetic sensitivity. On the other hand, with increasing concern about the detrimental effects of electromagnetic fields on wildlife and human health, studying the phenomenon of magnetoreception can contribute to a deeper understanding of how biological structures interact with these fields.

Xuesong Wang, Sharaf K. Magableh, Oraib Dawaghreh et al.

Virtual bidding plays an important role in two-settlement electric power markets, as it can reduce discrepancies between day-ahead and real-time markets. Renewable energy penetration increases volatility in electricity prices, making accurate forecasting critical for virtual bidders, reducing uncertainty and maximizing profits. This study presents a Transformer-based deep learning model to forecast the price spread between real-time and day-ahead electricity prices in the ERCOT (Electric Reliability Council of Texas) market. The proposed model leverages various time-series features, including load forecasts, solar and wind generation forecasts, and temporal attributes. The model is trained under realistic constraints and validated using a walk-forward approach by updating the model every week. Based on the price spread prediction results, several trading strategies are proposed and the most effective strategy for maximizing cumulative profit under realistic market conditions is identified through backtesting. The results show that the strategy of trading only at the peak hour with a precision score of over 50% produces nearly consistent profit over the test period. The proposed method underscores the importance of an accurate electricity price forecasting model and introduces a new method of evaluating the price forecast model from a virtual bidder's perspective, providing valuable insights for future research.

GF LHer, AG Osborne, AE Schweikert et al.

Lack of electricity access is widespread in the developing world and associated with increased mortality, reduced educational levels, and economic and social disadvantages, especially among women. The 2030 Agenda for Sustainable Development has emphasized securing access to affordable, reliable, and sustainable energy for all. For climatological and health reasons, particular attention has been focused on expanding the use of renewables for electricity production. In particular, photovoltaics, coupled to energy storage, is an attractive option for dispatchable electricity production, but the degree to which they can be used to address global lack of electricity access, and associated costs, merits more attention. This study presents a global geospatial analysis to identify areas suitable for production of dispatchable electricity using photovoltaics and energy storage. Analysis considers land use restrictions, 25 years of historical hourly solar irradiance, seasonal demand curves, population, and visible nighttime light (as a measure of electrification). We show that nearly all the population identified without electricity access (approx. 1.1 billion people) could get access to Tier 5 level electricity in the Sustainable Energy for All initiative framework using photovoltaics and battery storage coupled systems. Under most cost scenarios analyzed, around 90 percent of this population could be served for a lifetime cost of electricity (LCOE) of 0.20 dollars per kWhe or less at current system costs.

Daqi Yang, Wenfang Liu, Xin Wu

We consider the motion of test particles around a $Reissner-Nordström$ black hole immersed into a strong external magnetic field modifying the spacetime structure. When the particles are neutral, their dynamics are nonintegrable because the magnetic field acts as a gravitational effect, which destroys the existence of a fourth motion constant in the $Reissner-Nordström$ spacetime. A time-transformed explicit symplectic integrator is used to show that the motion of neutral particles can be chaotic under some circumstances. When test particles have electric charges, their motions are subject to an electromagnetic field surrounding the black hole as well as the gravitational forces from the black hole and the magnetic field. It is found that increasing both the magnetic field and the particle energy or decreasing the particle angular momentum can strengthen the degree of chaos regardless of whether the particles are neutral or charged. The effect of varying the black hole positive charge on the dynamical transition from order to chaos is associated with the electric charges of particles. The dynamical transition of neutral particles has no sensitive dependence on a change of the black hole charge. An increase of the black hole charge weakens the chaoticity of positive charged particles, whereas enhances the chaoticity of negative charged particles. With the magnitude of particle charge increasing, chaos always gets stronger.

Ritesh Ghosh, Manu Kurian

Electric charge transport of hadronic matter at finite temperature and magnetic field is studied within the linear sigma model. Anisotropic transport coefficients associated with the charge transport are estimated both in the weak and strong regimes of the magnetic field using the transport theory approach. In a weakly magnetized medium, the magnetic field effects are incorporated through the Lorentz force term in the Boltzmann equation. Strong magnetic field puts further constraints on the motion of charged particles through Landau quantization. Magnetic field-dependent thermal relaxation time is obtained from interaction rates of hadrons with the S-matrix approach by considering the Landau level kinematics of the charged hadrons. Mean-field effects are embedded in the analysis through the temperature-dependent hadron masses. Further, the hadronic medium response to a time-varying external electric field is studied in weak and strong magnetic field regimes. It is seen that electromagnetic responses of the hadronic matter have a strong dependence on the mean-field effects, sigma mass, the strength of the external fields, and its evolution in the medium.

Zu-Cheng Chen, Sang Pyo Kim, Lang Liu

We derive the hyperbolic orbit of binary black holes with electric and magnetic charges. In the low-velocity and weak-field regime, by using the Newtonian method, we calculate the total emission rate of energy due to gravitational and electromagnetic radiation from binary black holes with electric and magnetic charges in hyperbolic orbits. Moreover, we develop a formalism to derive the merger rate of binary black holes with electric and magnetic charges from the two-body dynamical capture. We apply the formalism to investigate the effects of the charges on the merger rate for the near-extremal case and find that the effects cannot be ignored.

Jayanta Dey, Sabyasachi Ghosh, Aritra Bandyopadhyay et al.

We have calculated electrical conductivity in the presence of a magnetic field by using the Nambu-Jona-Lasinio model.

Patrik Zielinski, Patric Rommel, Frank Schweiner et al.

The complete theoretical description of experimentally observed magnetoexcitons in cuprous oxide has been achieved by F. Schweiner et al [Phys. Rev. B 95, 035202 (2017)], using a complete basis set and taking into account the valence band structure and the cubic symmetry of the solid. Here, we extend these calculations by investigating numerically the autoionising resonances of cuprous oxide in electric fields and in parallel electric and magnetic fields oriented in [001] direction. To this aim we apply the complex-coordinate-rotation method. Complex resonance energies are computed by solving a non-Hermitian generalised eigenvalue problem, and absorption spectra are simulated by using relative oscillator strengths. The method allows us to investigate the influence of different electric and magnetic field strengths on the position, the lifetime, and the shape of resonances.

Maxim Dvornikov

We study the generation of an electric current, along the external magnetic field, of fermions, interacting by parity violating electroweak forces with background matter. First, we discuss the situation of massive particles with nonzero anomalous magnetic moments. We show that the induced current is vanishing for such particles in the state of equilibrium. Then, the case of massless fermions is studied. We demonstrate that the contribution of the electroweak interaction is washed out from the expression for the current, which turns out to coincide with the prediction of the chiral magnetic effect. Our results are compared with findings of other authors.

G. J. Iafrate, V. N. Sokolov, J. B. Krieger

The theory of Bloch electron dynamics for carriers in homogeneous electric and magnetic fields of arbitrary time dependence is developed in the framework of the Liouville equation. The Wigner distribution function (WDF) is determined from the single particle density matrix in the ballistic regime, i.e., collision effects are excluded. The single particle transport equation is established with the electric field described in the vector potential gauge, and the magnetic field is treated in the symmetric gauge. The general approach is to employ the accelerated Bloch state representation (ABR) as a basis so that the dependence upon the electric field, including multiband Zener tunneling, is treated exactly. In the formulation of the WDF, we transform to a new set of variables so that the final WDF is gauge invariant and is expressed explicitly in terms of the position, kinetic momentum, and time. The methodology for developing the WDF is illustrated by deriving the exact WDF equation for free electrons in homogeneous electric and magnetic fields. The methodology is then extended to the case of electrons described by an effective Hamiltonian corresponding to an arbitrary energy band function. In treating the problem of Bloch electrons in a periodic potential, the methodology for deriving the WDF reveals a multiband character due to the inherent nature of the Bloch states. In examining the single-band WDF, it is found that the collisionless WDF equation matches the equivalent Boltzmann transport equation to first order in the magnetic field. These results are necessarily extended to second order in the magnetic field by employing a unitary transformation that diagonalizes the Hamiltonian using the ABR to second order. The work includes a discussion of the multiband WDF transport analysis and the identification of the combined Zener-magnetic field induced tunneling.

J. Wilkes, E. A. Muljarov

We present a precise calculation of spatially-indirect exciton states in semiconductor coupled quantum wells and polaritons formed from their coupling to the optical mode of a microcavity. We include the presence of electric and magnetic fields applied perpendicular to the quantum well plane. Our model predicts the existence of polaritons which are in the strong coupling regime and at the same time possess a large static dipole moment. We demonstrate, in particular, that a magnetic field can compensate for the reduction in light-matter coupling that occurs when an electric field impresses a dipole moment on the polariton.

Abbas Ehsanfar, Babak Heydari

This paper introduces a new scheme for autonomous electricity cooperatives, called predictive cooperative (PCP), which aggregates commercial and residential electricity consumers and participates in the electricity market on behalf of its members. An axiomatic approach is proposed to calculate the day-ahead bid and to disaggregate the collective cost among participating consumers. The resulting formulation is shown to keep the members incentivized to both participate in the cooperative and remain truthful in reporting their expected loads. The scheme is implemented using PJM (world's largest wholesale electricity market) real-time and day-ahead price data for 2015 and a collection of residential and commercial load profiles. The model performance of this framework is compared to that of real-time pricing (RTP) scheme, in which wholesale market prices are directly applied to individual consumers. The results show truthful load announcement by consumers, reduction in electricity price variation for all consumers, and comparative benefits for participants.

Ladislav Kristoufek, Petra Lunackova

We analyze long-term memory properties of hourly prices of electricity in the Czech Republic between 2009 and 2012. As the dynamics of the electricity prices is dominated by cycles -- mainly intraday and daily -- we opt for the detrended fluctuation analysis, which is well suited for such specific series. We find that the electricity prices are non-stationary but strongly mean-reverting which distinguishes them from other financial assets which are usually characterized as unit root series. Such description is attributed to specific features of electricity prices, mainly to non-storability. Additionally, we argue that the rapid mean-reversion is due to the principles of electricity spot prices. These properties are shown to be stable across all studied years.

Jinsheng Wen, Guangyong Xu, Genda Gu et al.

We performed elastic neutron scattering measurements on the charge- and magnetically-ordered multiferroic material LuFe(2)O(4). An external electric field along the [001] direction with strength up to 20 kV/cm applied at low temperature (~100 K) does not affect either the charge or magnetic structure. At higher temperatures (~360 K), before the transition to three-dimensional charge-ordered state, the resistivity of the sample is low, and an electric current was applied instead. A reduction of the charge and magnetic peak intensities occurs when the sample is cooled under a constant electric current. However, after calibrating the real sample temperature using its own resistance-temperature curve, we show that the actual sample temperature is higher than the thermometer readings, and the "intensity reduction" is entirely due to internal sample heating by the applied current. Our results suggest that the charge and magnetic orders in LuFe(2)O(4) are unaffected by the application of external electric field/current, and previously observed electric field/current effects can be naturally explained by internal sample heating.

M. Hruska, S. Kos, S. A. Crooker et al.

We construct a spin-drift-diffusion model to describe spin-polarized electron transport in zincblende semiconductors in the presence of magnetic fields, electric fields, and off-diagonal strain. We present predictions of the model for geometries that correspond to optical spin injection from the absorption of circularly polarized light, and for geometries that correspond to electrical spin injection from ferromagnetic contacts. Starting with the Keldysh Green's function description for a system driven out of equilibrium, we construct a semiclassical kinetic theory of electron spin transport in strained semiconductors in the presence of electric and magnetic fields. From this kinetic theory we derive spin-drift-diffusion equations for the components of the spin density matrix for the specific case of spatially uniform fields and uniform electron density. We solve the spin-drift-diffusion equations numerically and compare the resulting images with scanning Kerr microscopy data of spin-polarized conduction electrons flowing laterally in bulk epilayers of n-type GaAs. The spin-drift-diffusion model accurately describes the experimental observations. We contrast the properties of electron spin precession resulting from magnetic and strain fields. Spin-strain coupling depends linearly on electron wave vector and spin-magnetic field coupling is independent of electron wave vector. As a result, spatial coherence of precessing spin flows is better maintained with strain than with magnetic fields, and the spatial period of spin precession is independent of the applied electrical bias in strained structures whereas it is strongly bias dependent for the case of applied magnetic fields.

Soo-Jong Rey, Shigeki Sugimoto

We study the decay of unstable D$p$-branes when the world-volume gauge field is turned on. We obtain the relevant Dp-brane boundary state with electric and magnetic fields by boosting and rotating the rolling tachyon boundary state of a D(p-1)-brane and then T-dualizing along one of the transverse directions. A simple recipe to turn on the gauge fields in the boundary state is given. We find that the effect of the electric field is to parametrically enhance coupling of closed string oscillation modes along the electric field direction and provide an intuitive understanding of the result in the T-dualized picture. We also analyze the system by using the effective field theory and compare the result with the boundary state approach.

S. S. Banerjee

The phenomenon of superconductivity was discovered in 1911, however, the methodology to classify and distinguish type-II superconductivity was established only in late fifties after Abrikosov's prediction of a flux line lattice in 1957. The advent of high temperature superconductors (HTSC) in 1986 focused attention onto identifying and classifying other possible phases of vortex matter in all classes of superconductors by a variety of techniques. We have collated evidences in support of a proposal to construct a generic phase diagram for weakly pinned superconducting systems, based on their responses to ac and dc magnetic fields. The phase diagram comprises quasi-glassy phases, like, the Bragg glass, a vortex glass and a reentrant glass in addition to the (completely) amorphous phases of pinned and unpinned variety. The characteristic metastability and thermomagnetic history dependent features recognized amongst various glassy vortex phases suggest close connections between vortex matter and other disordered condensed matter systems, like, spin glasses, super cooled liquids/ structural glasses, etc. A novel quenched random disorder driven fracturing transition stands out amongst other noteworthy facets of weakly vortex pinned vortex matter.

Hans-Andreas Engel, Emmanuel I. Rashba, Bertrand I. Halperin

Spin Hall effects are a collection of phenomena, resulting from spin-orbit coupling, in which an electrical current flowing through a sample can lead to spin transport in a perpendicular direction and spin accumulation at lateral boundaries. These effects, which do not require an applied magnetic field, can originate in a variety of intrinsic and extrinsic spin-orbit coupling mechanisms and depend on geometry, dimension, impurity scattering, and carrier density of the system--making the analysis of these effects a diverse field of research. In this article, we give an overview of the theoretical background of the spin Hall effects and summarize some of the most important results. First, we explain effective spin-orbit Hamiltonians, how they arise from band structure, and how they can be understood from symmetry considerations; including intrinsic coupling due to bulk inversion or structure asymmetry or due to strain, and extrinsic coupling due to impurities. This leads to different mechanisms of spin transport: spin precession, skew scattering, and side jump. Then we present the kinetic (Boltzmann) equations, which describe the spin-dependent distribution function of charge carriers, and the diffusion equation for spin polarization density. Next, we define the notion of spin currents and discuss their relation to spin polarization. Finally, we explain the electrically induced spin effects; namely, spin polarization and currents in bulk and near boundaries (the focus of most current theoretical research efforts), and spin injection, as well as effects in mesoscopic systems and in edge states.