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Driven conductance of an irradiated semi-Dirac material
摘要： We theoretically investigate the electronic and transport properties of a semi-Dirac material under the influence of an external time-dependent periodic driving field (irradiation) by means of Floquet theory. We explore the inelastic scattering mechanism between different sidebands, induced by irradiation, by using the Floquet scattering matrix approach. The scattering probabilities between the two nearest sidebands depend monotonically on the strength of the amplitude of the irradiation. The external irradiation induces a gap in the band dispersion which is strongly dependent on the angular orientation of momentum. Although the high-frequency limit indicates that the gap opening does not occur in an irradiated semi-Dirac material, a careful analysis of the full band structure beyond this limit reveals that a gap opening indeed appears for higher values of momentum (away from the Dirac point). Furthermore, the angular-dependent dynamical gap is also present and cannot be captured within the high-frequency approximation. The contrasting features of an irradiated semi-Dirac material, in comparison with irradiated graphene, can be probed via the behavior of conductance. The latter exhibits the appearance of nonzero conductance dips due to the gap opening in the Floquet band spectrum. Moreover, by considering a nanoribbon geometry of such a material, we also show that it can host a pair of edge modes which are fully decoupled from the bulk, which is in contrast to the case of a graphene nanoribbon where the edge modes are coupled to the bulk. We also investigate whether, if the nanoribbon of this material is exposed to the external irradiation, decoupled edge modes penetrate into the bulk.
关键词： Floquet theory,edge modes,semi-Dirac material,conductance,irradiation
更新于2025-09-04 15:30:14
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Unruh-DeWitt detectors as mirrors: Dynamical reflectivity and Casimir effect
摘要： We demonstrate that the Unruh-DeWitt harmonic-oscillator detectors in (1 t 1) dimensions derivative-coupled with a massless scalar field can mimic the atom mirrors in free space. Without introducing the Dirichlet boundary condition to the field, the reflectivity of our detector or atom mirror is dynamically determined by the interaction of the detector’s internal oscillator and the field. When the oscillator-field coupling is strong, a broad frequency range of the quantum field can be mostly reflected by the detector mirror at late times. Constructing a cavity model with two such detector mirrors, we can see how the quantum field inside the cavity evolves from a continuous to a quasidiscrete spectrum which gives a negative Casimir energy density at late times. In our numerical calculations, the Casimir energy density in the cavity does not converge until the UV cutoff is sufficiently large, with which the two internal oscillators are always separable.
关键词： Unruh-DeWitt detectors,atom mirrors,Casimir effect,reflectivity,quantum field theory
更新于2025-09-04 15:30:14
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[IEEE 2018 24th International Conference on Pattern Recognition (ICPR) - Beijing, China (2018.8.20-2018.8.24)] 2018 24th International Conference on Pattern Recognition (ICPR) - Image Exploration Procedure Classification with Spike-timing Neural Network for the Blind
摘要： Individuals who are blind use exploration procedures (EPs) to navigate and understand digital images. The ability to model and detect these EPs can help the assistive technologies’ community build efficient and accessible interfaces for the blind and overall enhance human-machine interaction. In this paper, we propose a framework to classify various EPs using spike-timing neural networks (SNNs). While users interact with a digital image using a haptic device, rotation and translation-invariant features are computed directly from exploration trajectories acquired from the haptic control. These features are further encoded as model strings through trained SNNs. A classification scheme is then proposed to distinguish these model strings to identify the EPs. The framework adapted a modified Dynamic Time Wrapping (DTW) for spatial-temporal matching with Dempster-Shafer Theory (DST) for multimodal fusion. Experimental results (87.05% as EPs’ detection accuracy) indicate the effectiveness of the proposed framework and its potential application in human-machine interfaces.
关键词： Dempster-Shafer Theory,Spike-timing Neural Network,Spatio-temporal Pattern,Exploration Procedures,Haptic-based Interface,Blind Community
更新于2025-09-04 15:30:14
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Optimization of Far-field Radiation from Impedance-Loaded Nanoloops Accelerated by an Exact Analytical Formulation
摘要： Impedance loading is a common technique traditionally used in the RF to enhance the performance of an antenna, but its application in the optical regime is not as rigorously studied. This is mainly due to a lack of exact analytical expressions that can be used to rapidly predict the radiation properties of loaded nanoantennas. This paper will derive a set of useful analytical expressions for the far-field radiation properties of loop antennas loaded with an arbitrary number of lumped impedances that are valid from the RF to optical regimes. The analytical expressions will be validated with full-wave solvers and can be evaluated more than 100x faster. The ability to perform such rapid evaluations enables, for the first time, large-scale single- and multi-objective optimizations. A series of optimizations reveal that electrically small super-directive antennas can be achieved at a variety of far field angles through capacitive loading, paving the way for a pattern reconfigurable antenna. In addition, gains of greater than 3 dB can be achieved for electrically small antennas over a fractional bandwidth of 28%. Finally, it is shown that impedance loading can be used to achieve circularly polarized radiation from a single loop.
关键词： Loop antennas,Antenna theory,Optimization,Nanotechnology,Submillimeter wave technology
更新于2025-09-04 15:30:14
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Multi-resolution Image Fusion in Remote Sensing () || Use of Self-similarity and Gabor Prior
摘要： In this chapter, we introduce a concept called self-similarity and use the same for obtaining the initial fused image. We also use a new prior called Gabor prior for regularizing the solution. In Chapter 4, degradation matrix entries were estimated by modelling the relationship between the Pan-derived initial estimate of the fused MS image and the LR MS image. This may lead to inaccurate estimate of the final fused image since we make use of the Pan data suffering from low spectral resolution in getting the initial estimate. However, if we derive the initial fused image using the available LR MS image, which has high spectral resolution, mapping between LR and HR would be better and the derived degradation matrix entries are more accurate. This makes the estimated degradation matrix better represent the aliasing since we now have an initial estimate that has both high spatial and spectral resolutions. To do this, we need to obtain the initial estimate using only the available LR MS image since the true fused image is not available. We perform this by using the property of natural images that the probability of the availability of redundant information in the image and its downsampled versions is high [89]. We exploit this self-similarity in the LR observation and the sparse representation theory in order to obtain the initial estimate of the fused image. Finally, we solve the Pan-sharpening or multi-resolution image fusion problem by using a model based approach in which we regularize the solution by proposing a new prior called the Gabor prior.
关键词： sparse representation theory,multi-resolution image fusion,Gabor prior,self-similarity,Pan-sharpening
更新于2025-09-04 15:30:14
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Valence ππ* Excitations in Benzene Studied by Multiconfiguration Pair-Density Functional Theory
摘要： We explore the valence singlet and triplet ππ* excitations of benzene with complete active space self-consistent field (CASSCF) theory, complete active space perturbation theory (CASPT2), and multiconfiguration pair-density functional theory (MC-PDFT) for four different choices of active space. We propose a new way to quantify the covalent and ionic character of the electronic states in terms of the components of the total electronic energy. We also explore the effect of scaling the exchange and correlation components of the on-top density functional used in MC-PDFT; we observe that increasing the exchange contribution improves the MC-PDFT excitation energies for benzene.
关键词： CASSCF,MC-PDFT,benzene,CASPT2,valence excitations,multiconfiguration pair-density functional theory
更新于2025-09-04 15:30:14