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An on-Line Extraction Method for the Parasitic Capacitance of the Photovoltaic Panel
摘要： Mobile crowdsensing has shown elegant capacity in data collection and has given rise to numerous applications. In the sense of coverage quality, marginal works have considered the efficient (less cost) and effective (considerable coverage) design for mobile crowdsensing networks. We investigate the optimal quality-aware coverage in mobile crowdsensing networks. The difference between ours and the conventional coverage problem is that we only select a subset of mobile users so that the coverage quality is maximized with constrained budget. To address this new problem, which is proved to be NP-hard, we first prove that the set function of coverage quality is nondecreasing submodular. By leveraging the favorable property in submodular optimization, we then propose an (1 ? (1/e)) approximation algorithm with O(nk+2) time complexity, where k is an integer that is greater than or equal to 3. Finally, we conduct extensive simulations for the proposed scheme, and the results demonstrate that ours outperforms the random selection scheme and one of the state of the art in terms of total coverage quality by, at most, 2.4× and 1.5× and by, on average, 1.4× and 1.3×, respectively. Additionally, ours achieves a near-optimal solution, compared with the brute-force search results.
关键词： Approximation algorithm,mobile crowdsensing networks,quality-aware sensing,coverage
更新于2025-09-16 10:30:52
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Non-equilibrium electronic transport through a quantum dot with strong Coulomb repulsion in the presence of a magnetic field
摘要： The non-equilibrium electronic transport through a nanoscale device composed of a single quantum dot between two metallic contacts is studied theoretically within the framework of the Keldysh formalism. The quantum dot consists of a single energy level subject to an applied magnetic field. Correlations due to the Coulomb repulsion between electrons on the dot are treated with a Green’s function decoupling scheme which, although similar to the Hubbard-I approximation, captures some of the dynamics beyond. The scheme is exact in the so-called atomic limit, defined by vanishing tunneling between contacts and dot, and in the non-interacting limit, where the on-dot Coulomb repulsion is zero. Explicit analytic solutions, valid for arbitrary magnetic fields, are obtained for two important setups: (i) the stationary regime, with constant voltage bias between the leads, and (ii) the time-dependent regime for metallic leads with constant density of states of infinite width. In these regimes, the current through the dot is evaluated numerically for various parameter sets and its main features interpreted in terms of the underlying physical processes. The results are compared to the non-crossing approximation (NCA) and diagrammatic non-equilibrium quantum Monte-Carlo (QMC) where available.
关键词： Coulomb repulsion,magnetic field,non-equilibrium electronic transport,Hubbard-I approximation,non-crossing approximation,quantum dot,quantum Monte-Carlo,Keldysh formalism
更新于2025-09-12 10:27:22
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High-energy bremsstrahlung on atoms in a laser field
摘要： The impact of a laser field on the process of photon radiation by an ultra-relativistic electron in an atomic field is investigated. The angular distribution and the spectrum of the radiated photon are derived. By means of the quasiclassical approximation, the obtained results are exact in the parameters of the laser field and the atomic field. It is shown that the impact of the laser field is significant even for fairly average values of the laser field parameters routinely achievable nowadays. Therefore, an experimental observation of the influence of the laser field on bremsstrahlung in the atomic field is a very feasible task.
关键词： quasiclassical approximation,photon radiation,bremsstrahlung,atomic field,laser field
更新于2025-09-12 10:27:22
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An approach for correcting optical paths of different wavelength lasers in diffusive medium based on Monte Carlo simulation
摘要： Near-infrared spectroscopy (NIRS) generally uses multiple wavelengths of light to obtain functional information. When different wavelengths are employed together, their optical paths are different in the medium and it can potentially cause errors. In this study, we introduced an approach of correcting optical paths when laser sources are used. Laser can be approximated by a point source in a diffusive medium and its depth depends on the wavelength. By multiplying the ratio of detected weights emitted from different point sources, they are conceptually moved to the same position. Monte Carlo simulation was implemented to accumulate required data. As an example for verifying this method, optical properties of the white matter of the brain was used. All combinations of four wavelengths (400, 550, 700, and 850 nm) and six source-detector distances (0.5 mm to 3.0 mm at intervals of 0.5 mm) were simulated. Under the same example conditions, the difference between the simulation results and this method was about ‘1.28%’. The results showed that this approach is applicable to short source-detector distance conditions.
关键词： Monte Carlo simulation,Point source approximation,Near infrared spectroscopy,Light diffusion,Optical path,Penetration depth
更新于2025-09-12 10:27:22
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Dielectric environment effect on linear and nonlinear optical properties for CdS/ZnS core/shell quantum dots
摘要： The eigenvalues, transition energy, the linear and nonlinear dielectric functions have been numerically investigated for CdS/ZnS spherical core/shell quantum dots embedded in various dielectric matrices. The evaluation was carried out for three commonly used matrices, such as PVA, PMMA and SiO2. Calculations were done under the effective mass approximation and compact density matrix approach. Results revealed that the nonlinear optical property is strongly affected by the nature of the matrix material. By increasing core/shell radii ratio the energy states as well as the transition energy are decreasing. It is also indicated that the presence of the dielectric mismatch in the QD-matrix system can cause significant enhancement on the linear and third order nonlinear dielectric function.
关键词： Complex dielectric function,Core/shell,Density matrix approach,Effective mass approximation,Nonlinear optic
更新于2025-09-12 10:27:22
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Ionization-field instability in the laser-induced breakdown of nanoporous dielectric
摘要： The theory of ionization-?eld instability in a continuous homogeneous medium is generalized to the heterogeneous nanoporous one with the purpose to clear and analyze the mechanism of nanograting formation during the optical breakdown process in a transparent dielectric (fused silica) containing multiple small inclusions (nanobubbles) with a lowered ionization threshold. Based on the Maxwell Garnett approximation extended to include the size effect caused by the ?nite ratio of the bubble sizes to the scale of unstable perturbations, we have obtained the equation system describing the spatiotemporal evolution of the plasma density, average ?eld, and effective dielectric permittivity and have derived the characteristic equation connecting the temporal growth rate of these perturbations with their spatial period. Analysis of the roots of this equation shows that the unstable periodic perturbation structure having the maximal growth rate is close in character to the nanogratings observed experimentally (modulation in the direction of the pump wave polarization with the period approximately equal to the half-wavelength in the host material).
关键词： laser-induced breakdown,nanograting formation,nanoporous dielectric,Maxwell Garnett approximation,ionization-field instability
更新于2025-09-12 10:27:22
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Odd–even harmonic generation from oriented CO molecules in linearly polarized laser fields and the influence of the dynamic core-electron polarization
摘要： We present a detailed theoretical study of the odd–even harmonics generated from the polar molecule CO by the method based on numerically solving the time-dependent Schro¨dinger equation within the single-active-electron approximation. First, we reproduce the pure even harmonic generation of CO predicted theoretically by Hu et al. using the time-dependent density functional theory [H. Hu et al., Phys. Rev. Lett., 2017, 119, 173201]. Then, based on the Floquet approach, we are able to attribute this behavior to the half-cycle mirror symmetry of the molecule–field system when the polar molecule is perpendicular to the laser polarization. By numerical simulations, we show that this symmetry is broken at orientation angles other than 901 resulting in the odd–even harmonic generation and a non-trivial even-to-odd harmonics ratio strongly dependent on the molecular orientation. Furthermore, we investigate the influence of the dynamic core-electron polarization (DCeP) on the odd–even behavior near the cutoff of the high-order harmonic spectra. We emphasize that the DCeP effect is noticeable for the odd harmonics only.
关键词： time-dependent Schro¨dinger equation,high-order harmonic generation,polar molecule CO,Floquet approach,dynamic core-electron polarization,single-active-electron approximation
更新于2025-09-12 10:27:22
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Entanglement of bright and dark modes in parity-time-symmetric plasmonic nanoantennas
摘要： The generic model of two coupled multimode plasmonic nanospheres with gain and loss forming a parity-time (PT ) symmetric dimer is considered. Analytical solutions based on a quasistatic approximation are used to explore the behavior of the eigenmodes in such a coupled nanoantenna system as a function of their separation distances and their gain-loss level. It is shown that the introduction of the same amount of gain and loss modi?es the composition of eigenmodes and breaks their orthogonality. The resulting entanglement of different spatial order and symmetry modes can be advantageously exploited to actively control the scattering properties of such multimode PT -symmetric nanoantennas.
关键词： eigenmodes,gain and loss,plasmonic nanoantennas,quasistatic approximation,parity-time symmetry
更新于2025-09-12 10:27:22
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Ultrahighly Enhanced Performance of Single Cadmium Selenide Nanobelt by Plasmonic Gold Particles
摘要： Noble metal nanoparticles have been demonstrated by a huge application prospect for photodetector (PD) due to their unique and tunable optical properties. Herein, a simple strategy is presented by a combination of gold nanoparticles (Au NPs) and broadband photoresponse cadmium selenide nanobelts (CdSe NBs) to get ultrasensitive, broadband photoresponse (300–720 nm) and tunable photoresponse PD. Concretely, the Au NPs are fabricated on CdSe NBs via ion sputtering and annealing, and the morphology of Au NPs is systematically adjusted by simply tuning the sputter time from 60 to 140 s. Compared with the pure CdSe NB PD, the Au NPs hybrid CdSe NB PD exhibits a high responsivity, especially in the range of 525–575 nm with low light intensity (enhancement of (cid:3)2). The response time of the hybrid PD is (cid:1)2894% at 550 nm with 79.6 μW cm decreased substantially from 0.8 to 0.2 ms. More importantly, the hybrid PD possesses a tunable absorption in the range of 538–580 nm, which is bene?ted from tunable plasmon resonance of Au NPs. These results are con?rmed by the theoretical simulation. It is believed that this strategy offers new opportunities to design ultrasensitive, broadband spectra, and tunable wavelength PD.
关键词： cadmium selenide nanobelts,photodetectors,the discrete dipole approximation,surface plasmon resonances
更新于2025-09-11 14:15:04
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Entanglement via entangled-boundary-condition trajectories: Long-time accuracy
摘要： Entanglement is considered as a purely quantum effect. The present paper, however, joins many other works that pursue the idea of describing it using classical quantities. In particular, we are interested in the entanglement dynamics of a pure state composed of two parts, initially prepared in a product of coherent states and governed by a generic Hamiltonian. In this scenario, the linear entropy of the reduced state, our entanglement quanti?er, was shown to be written, in the short-time regime, in terms of a real trajectory of the underlying classical dynamics. We extend this semiclassical result by demonstrating that it is possible to include complex trajectories in the calculation. This strategy contributes to improving the previous approximation, extending its accuracy for longer values of time. We also show, for a particular Hamiltonian, a ?rst application of the achieved formula, attesting to its ef?ciency.
关键词： semiclassical approximation,entanglement,quantum dynamics,linear entropy,complex trajectories
更新于2025-09-11 14:15:04