- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Direct Imaging of Isofrequency Contours of Guided Modes in Extremely Anisotropic All-Dielectric Metasurface
摘要： In this work, we investigate an all-dielectric metasurface based on the silicon on insulator platform for manipulating of guided modes in the visible and near-infrared spectral ranges. We use the Fourier modal method to demonstrate numerically, that guided modes excited in the metasurface support both hyperbolic-like and elliptic dispersion regimes. We implement a back focal plane microscope combined with a high refractive index solid immersion lens to directly image the isofrequency contours of the guided modes (surface waves). Reconstruction of dispersion unambiguously reveals the transition between different dispersion regimes.
关键词： Fourier microscopy,All-dielectric metasurface,isofrequency contours,Fourier modal method,dispersion reconstruction,surface waves
更新于2025-09-23 15:23:52
-
Synthesis and formation mechanism of amorphous silica particles via sol–gel process with tetraethylorthosilicate
摘要： Silica microspheres with narrow particle size distribution and average diameter of 80-200 nm were prepared by hydrolysis and condensation of tetraethylorthosilicate (TEOS) in ethanol solution. Effects of TEOS, ammonia, water concentration, and temperature on particle size and morphology were investigated by laser particle size analysis and field emission scanning electron microscopy (FESEM), in conjunction with energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) spectroscopy. Monomer addition model was employed to analyze the stability of intermediate, as well as the direction in which the reaction of silica particles proceeds. The analysis was carried out by Materials Studio. Results demonstrated that particle size of Nano-silica increases with increasing concentrations of H2O, NH3.H2O, and TEOS in ethanol, whereas the size decreases with increasing temperature. In addition, when proper amount of H2O was added into NH3.H2O at suitable temperature, silicic acid can act as a nucleus for amorphous Nano-silica particles, forming microspheres with round and smooth surfaces. By contrast, when TEOS was used, resultant nanoparticles have poor surfaces. During nucleation process of Nano-silica, silicic acid can also acts as nucleating agent providing a platform for the growth of nanoparticles with symmetric structure. Findings further indicated that the reaction proceeds by first silicic acid participates in the reaction, and the dimer and trimer molecules then react with the surface of silicic acid molecules; the same products could be produced by different reactions.
关键词： Amorphous,St?ber Method,TEOS,Nano-silica,Monomer addition mode
更新于2025-09-23 15:23:52
-
Multi-mode optimal fuzzy active vibration control of composite beams laminated with photostrictive actuators
摘要： Firstly, a multi-field coupling finite element formulation of composited beam laminated with the photostrictive actuators is developed in this paper. Moreover, an optimal fuzzy active control algorithm is also proposed on the basis of the combination of optimal control and fuzzy one. This method opens a new avenue to resolve the contradiction between the linear system control method and nonlinear actuating characteristics of photostrictive actuators. The desired control for suppressing multi-modal vibration of photoelectric laminated beam is firstly obtained through optimal control and then the fuzzy control is used to approach the desired mechanical strain induced by photostrictive actuators. Thus, the multi-mode vibration control of beam is realized. In the design process of optimal fuzzy controller, the design of fuzzy control is independent of optimal control. The simulation results demonstrate that the proposed control method can effectively realize multi-modal vibration control of photoelectric laminated beams, and the control effect of optimal fuzzy control is better than that of optimal state feedback control.
关键词： Multiple modes,Photostrictive actuators,Active control,Optimal fuzzy control algorithm,Finite element method
更新于2025-09-23 15:23:52
-
Exploring approximate geometries of minimum energy conical intersections by TDDFT calculations
摘要： An approach is proposed to obtain approximate geometries for minimum energy conical intersections between the ground and first excited singlet electronic states (S0/S1-MECIs) using the time-dependent density functional theory (TDDFT). This approach uses the energy shift method to avoid discontinuities on TDDFT potential energy surfaces around conical intersections. It is shown numerically that the approximate S0/S1-MECIs of benzene and naphthalene obtained by this approach qualitatively reproduce the geometries and energies of the S0/S1-MECIs obtained by multireference theories. Moreover, the performance of the present approach when combined with an automated MECI searching method is examined through applications to benzene and naphthalene.
关键词： energy shift method,time dependent density functional theory,gradient projection,single component artificial force induced reaction,conical intersection,global reaction route mapping
更新于2025-09-23 15:23:52
-
Effects of raw materials on NaNbO <sub/>3</sub> nanocube synthesis via the solvothermal method
摘要： A nanocube is a single nanoscale crystal with a cubic shape. Raw materials are an important factor in determining the synthesis of nanocubes. In this study, we investigated various niobium compounds that serve as raw materials, each inducing different effects during nanocube synthesis. NaNbO3 nanocubes were synthesized using a two-step process. The first step in this process, synthesis of the raw materials, was followed by solvothermal synthesis of NaNbO3 nanocubes. The raw material for the first step was obtained by applying heat treatment to a precursor following Nb hydrolysis. The heat treatment was performed at temperatures of 300°C to 1000°C. Nb2O5 was obtained after heat treatment of its precursor, during which its crystalline system morphed into hexagonal, orthorhombic, and monoclinic systems with respective increases in temperature. For the second step, we obtained various NaNbO3 morphologies via the solvothermal method using water, methanol, or ethanol as a reaction medium. NaNbO3 nanocubes were formed by applying the solvothermal method to the synthesized precursor during heat treatment at 800°C. Solvothermal synthesis was performed with methanol as the reaction medium at 200°C, which resulted in the formation of NaNbO3 nanocubes.
关键词： Raw material,Solvothermal method,Nanocube,NaNbO3
更新于2025-09-23 15:23:52
-
Photoinduced collective mode, inhomogeneity, and melting in a charge-order system
摘要： We theoretically investigate photoresponses of a correlated electron system upon stimuli of a pulsed laser light. Real-time dynamics of an interacting spinless fermion model on a one-dimensional chain, as a model of charge order (CO), are numerically simulated using the time-dependent Hartree-Fock method. In particular, we discuss the differences between two situations as the initial state: the homogeneous order and the presence of a domain wall, i.e., a kink structure embedded in the CO bulk. Coherent dynamics are seen in the former case: When the frequency of the pump light ωp is varied, along with single particle excitations across the CO gap (ΔCO), the resonantly-excited collective phase mode near ωp ≈ ΔCO/2 efficiently destabilizes CO. In clear contrast, in the latter case, when ωp is tuned at such in-gap frequencies and the intensity of light is sufficiently large, inhomogeneity spreads out from the kink to the bulk region through kink creations. Moreover, even stronger intensity induces the inhomogeneous melting of CO where the CO gap is destroyed.
关键词： photoinduced phase transition,charge order,collective mode,inhomogeneity,time-dependent Hartree-Fock method
更新于2025-09-23 15:23:52
-
Intrinsic method for the evaluation of beam shape coefficients in spheroidal coordinates for oblique illumination
摘要： When dealing with T-matrix scattering, e.g. in the framework of Generalized Lorenz-Mie Theory (GLMT) or of Extended Boundary Condition Method (EBCM), the incident electromagnetic fields are expanded over a set of vectorial wave functions, with expansion coefficients expressed in terms of beam shape coefficients (BSCs). In the case of structured beams, the evaluation of these BSCs may constitute a challenging issue, particularly in the case of spheroidal coordinates. BSCs in spheroidal coordinates have been originally evaluated using an extrinsic method, i.e. they have been expressed in terms of more conventional BSCs in spherical coordinates. Later on, it has been possible to provide expressions to evaluate spheroidal BSCs using an intrinsic approach, i.e. by working only inside the spheroidal coordinate system used to deal with the scattering problem. Fairly recently, the intrinsic method for the evaluation of BSCs in spheroidal coordinates for on-axis standard configuration has been released in the archival literature. The present paper extends the intrinsic method to the case of oblique illumination. It also serves as a review devoted to GLMTs in spheroidal coordinates.
关键词： Spheroidal coordinates,Intrinsic method,Generalized Lorenz-Mie theories,Beam shape coefficients
更新于2025-09-23 15:23:52
-
Scattering of an Airy light-sheet by a non-spherical particle using discrete dipole approximation
摘要： The scattering of an Airy light-sheet by a non-spherical particle is investigated using the discrete dipole approximation (DDA). The internal and near-surface fields of the cube placed in an Airy light-sheet are calculated, and the effects of the transverse dimension factor w0, the attenuation factor a, and beam center z0 are mainly discussed. w0 can increase the number of side lobes incident on the target, thereby increase the wave jet energy. Increasing the attenuation coefficient a leads to less wave jet energy. By moving the light-sheet, the side lobe of the incident light-sheet increases, and the wave jet energy increases. Potential applications include optical manipulation of particles, particle sizing, optical imaging, etc.
关键词： Scattering,Airy light-sheet,Angular spectrum decomposition method,Discrete dipole approximation (DDA)
更新于2025-09-23 15:23:52
-
[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Sea Ice Change Detection in SAR Images Based on Collaborative Representation
摘要： Sea ice change detection from synthetic aperture radar (SAR) images is important for navigation safety and natural resource extraction. This paper proposed a sea ice change detection method from SAR images based on collaborative representation. First, neighborhood-based ratio is used to generate a difference image (DI). Then, some reliable samples are selected from the DI by hierarchical fuzzy C-means (FCM) clustering. Finally, based upon these samples, collaborative representation method is utilized to classify pixels from the original SAR images into unchanged and changed class. From there, the final change map can be obtained. Experimental results on two real sea ice datasets demonstrate the superiority of the proposed method over two closely related methods.
关键词： sea ice change detection,synthetic aperture radar,clustering method,collaborative representation
更新于2025-09-23 15:23:52
-
Surface plasmon resonance on blue GaN-based VCSEL with Al-grating
摘要： Based on the research of surface plasmon (SP) applied to Vertical-Cavity Surface-Emitting Lasers (VCSEL), we proposed a new 465 nm GaN-based VCSEL to enhance illumination by deposit Al rectangular grating onto p-i-n layer. Meanwhile, an increase in the e?ective radiated power was obtained by the control of a surface plasmon mode, which depends strongly on the structural parameters such as material, period, depth and dipole location. Compared to conventional structure, we have a 30% improvement in e?ective radiated power. Such advantages make surface Al-grating be an alternative low-cost and simple technique used in SP-coupled VCSEL for the blue range.
关键词： Finite-di?erence time-domain method,Metal grating,Surface plasmon,Vertical-cavity surface-emitting laser (VCSEL)
更新于2025-09-23 15:23:52