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Nature-Inspired Quasicrystal SRG Using Fibonacci Sequences in Photo-Reconfiguration on Azo Polymer Films
摘要： In this study, we present the fabrication route of quasicrystal surface relief grating (SRG) of azopolymer. Based on photo-reconfigurable azobenzene property, various morphologies of grating patterns were inscribed on azopolymer thin-films by two-beam coupling light interference lithography (LIL) process. Multiplexing the LIL with different rotation sequence on azopolymers resulted in unusual surface structures including quasicrystal-like SRGs with Fibonacci sequences in rotational LIL. We investigated the effect of rotation sequence on the grating patterns by atomic force microscope, revealing that rotation sequence is a critical parameter determining surface structures of azopolymer films.
关键词： holographic optical elements,diffraction gratings,optical fabrication
更新于2025-09-23 15:21:21
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Structural, Electrical and Morphological Properties of Materials Type Sillenite Phase Bi12TiO20
摘要： This work reports the investigation of the ternary system Bi2O3–TiO2–MgO. Some compositions have been synthesized by solid state reaction at 800?°C and characterized by powder X-ray diffraction. The doping of (α-Bi2O3) allowed us to stabilize three compositions isotype of sillenite structure phase with formulas Bi0.9 Ti0.1 O1.55, Bi0,9 Ti0,05Mg0,05 O1,5, and Bi0.8 Mg0.1 Ti0.1 O1.5. The structural resolution of the synthesized materials was performed using Rietveld method by means of FullProf program. It crystallizes in the cubic system. The space group I23 and lattice parameter a = 10.1723(2) ?. The morphological proprieties of the synthesized compositions have been investigated by means of scanning electron microscopy (SEM). Sintered samples showed a dense and uniform microstructure. The density of sintered samples obtained is nearly 92% of the theoretical density. Various impedance model including capacity and Warburg impedances have been used to interpret the Nyquist representations of electrical analyses. The highest conductivity is observed for Bi0.9 Ti0.1 O1.55 (σ = 1.39E?07 at 600?°C).
关键词： Electrical Impedance,SEM,Spectroscopy,X-ray diffraction,Sillenite
更新于2025-09-23 15:21:21
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Ear-to-Ear Propagation Model based on Geometrical Theory of Diffraction
摘要： An ear-to-ear propagation model based on geometrical theory of diffraction is presented. The model uses the creeping wave loss along the geodesic paths that connect the ears. It is the ?rst model to investigate which geodesic paths that link the ears. The model uses geometrical theory of diffraction expressions for a lossy dielectric material, which is a much better approximation of the human body than the perfect electric conductor approximation often used. The model is validated for the industrial, scienti?c and medical band at 2.45 GHz. The model is valid at any frequency range as long as the propagation loss through the head is signi?cantly higher than the propagation loss around the head. Likewise, the model could be used for other areas of the body. The comparison with simulations show strong correlation. The antenna orientation and frequency sweeps were preformed to further investigate the model. The sweeps change the radiation pattern of the antenna to utilize different paths around the head, but the model still correlates with the simulation. This validates the models division of the ear-to-ear propagation into different geodesic paths around the head.
关键词： Hearing Instruments,WBAN,Ear-to-Ear,Geometrical Theory of Diffraction,Off-Body,On-Body,Creeping Wave
更新于2025-09-23 15:21:21
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Geometrical Theory of Diffraction Formulation for On-Body Propagation
摘要： A Geometrical Theory of Diffraction model for on-body propagation is developed in the article. The exact solution to the canonical problem of a plane wave incident on an in?nitely long cylinder, with arbitrary constitutive parameters, is found. The same is done for a magnetic and an electric in?nitesimal dipole source of any orientation, located on the surface of the cylinder. The exact solutions are transformed with the Watson transformation to yield asymptotic expressions that are valid in the deep shadow region. These asymptotic expressions are validated by comparison to the numerically evaluated exact solution. It is found that the expressions are valid as long as the object is opaque, with a geometry down to the size κ2+τ 2 > λ0/2, and the rays not too torsional τ /κ < 2, where κ and τ are the curvature and torsion of the local geometry, respectively. The asymptotic expressions are found to approximate the exact solution signi?cantly better than the asymptotic expression of an equivalent perfect electric conductor geometry. The same is the case for the impedance boundary condition asymptotic approximation for low dielectric constant materials. Finally, the asymptotic expressions are generalized so they can be applied to any convex geometry of the human body or an opaque lossy dielectric of electrically large size.
关键词： asymptotic approximation,WBAN,lossy dielectric cylinder,Geometrical Theory of Diffraction,on-body communication
更新于2025-09-23 15:21:21
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Magnetic and optical behaviors of SnO2-x thin films with oxygen vacancies prepared by atomic layer deposition
摘要： SnO2-x thin films with different concentration oxygen vacancies were prepared by Atomic Layer Deposition (ALD). Specifically, the oxygen vacancy concentration was controlled by the oxidation pulse time during the ALD process. The crystal structure of the as-prepared thin films was determined by XRD, and the magnetic properties were measured by VSM, while the optical properties were measured by optical transmittance spectrum. The results showed that the oxygen vacancy concentration of the SnO2-x could be controlled by the oxidation pulse time, and the crystal structures, magnetic properties, and optical properties were largely impacted by the concentration of oxygen vacancy.
关键词： microstructure,thin film,magnetic,diffraction,nanocrystal,oxygen vacancy
更新于2025-09-23 15:21:21
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[IEEE 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Odessa, Ukraine (2018.9.4-2018.9.7)] 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Time Domain Modelling of Pulse Wave Scattering on Small Metal Spheres
摘要： We consider a short pulse plane wave incident on a small metal sphere. The scattered field from the sphere can be presented as a multipole expansion over spherical harmonics. For small spheres (compared to the signal duration) the scattered field will be mainly presented by the dipole component. So we find in a closed form and analyze the convolution operator that relates the induced dipole moment (both electric and magnetic dipoles are considered) to the incident electric field waveform. The numerical approach to calculate scattering from several such spheres is described.
关键词： transient electric dipole,discrete dipole approximation,induced dipole moment,closed-form solution,transient diffraction
更新于2025-09-23 15:21:21
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[IEEE 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Odessa, Ukraine (2018.9.4-2018.9.7)] 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Effective Microwave Electromagnetic Response of the Infinite Chain of Dielectric Coated Circular Metal Cylinders
摘要： Microwave approximations for effective electric and magnetic responses of the infinite chain have been obtained in this study. This infinite chain is comprised of long dielectric coated circular metal cylinders infinitely periodically space. The obtained approximations have been derived on the basis of the long wave approximation for the diffraction problem of a plane electromagnetic wave on the cylindrical chain using the Effective Medium Theory. Comparisons of the analytically obtained results with the numerically calculated ones have made in the study.
关键词： Artificial Dielectrics,Effective Medium Theory,Plane Wave Diffraction,Infinite Grating
更新于2025-09-23 15:21:21
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A noticeable effect of thickness on third order nonlinear properties of CBD grown CdS thin films investigated by Z-scan measurements
摘要： In current work, thin films of CdS with alike thickness were fabricated by chemical bath deposition by varying the deposition time. Thickness of films was measured to be ~ 200, 250 and 300 nm using Alfa step stylus profilometer. As thickness play significant role hence thickness dependent structural, vibrational, morphological, optical and third order nonlinear optical (TONLO) studies are exclusively explored. The XRD and FT-Raman studies revealed an enhancement in crystallinity with increasing thickness of films and also confirmed non existence of any impurity peak. Crystallite size evaluated from Scherrer's rule is found to be increased from 21 to 30 nm with increasing the thickness of films. Scanning electron microscopy images demonstrates the modification of spherical nanoparticles to nano needles with increase of thickness of films. Average size of grains are intuited to be in 30 to 65 nm range. Transmission spectra showed high transparency for films of 200 nm thickness and later reduced with increase of thickness. Direct energy gap was attained in range of 2.2 to 2.3 eV. Stable values of k and n indicates defect free films. The n2 and χ3 values are found to very high which are in range of 3.15 to 8.67 (×10-6) and 1.11 to 1.47 (×10-1), respectively. Such transparent films with higher TONLO susceptibility values are potential candidates for optoelectronic device applications.
关键词： CdS films,FT-Raman spectroscopy,Optical properties,X-ray diffraction,third order nonlinear properties
更新于2025-09-23 15:21:21
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Study of materials structure physics of isomorphic LiNbO <sub/>3</sub> and LiTaO <sub/>3</sub> ferroelectrics by synchrotron radiation X-ray diffraction
摘要： Electron charge density studies of stoichiometric LiNbO3 and LiTaO3 ferroelectrics have been carried out by analyzing the synchrotron radiation X-ray powder di?raction data using a combination of the Rietveld and maximum entropy methods. The clear relationships between the Nb(Ta)–O bond length, the electron charge density on the Nb(Ta)–O bond, and the phase transition temperature TC are revealed for isomorphic structures. Nb(Ta)–O bonding plays an important role in the elevation of TC. The TC in LiNbO3 being higher than that in LiTaO3 is attributed to the larger lattice distortion of the Nb–O oxygen octahedron in LiNbO3. The validity of estimating TC for LiNbO3 family crystals from the degree of lattice distortion in the ferroelectric structure is discussed.
关键词： ferroelectric,LiTaO3,X-ray diffraction,synchrotron radiation,LiNbO3,phase transition temperature,electron charge density
更新于2025-09-23 15:21:21
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Scattering of light from disordered photonic structures
摘要： We study theoretically and experimentally the scattering of light from ordered and disordered photonic structures. As an example, we consider a thin slab of a woodpile-type photonic crystal and introduce random fluctuations in the rod orientation, revealing a crossover from the Laue diffraction to the formation of speckle patterns. We observe a nontrivial interplay between order and disorder when the orientational disorder is added only in one direction of the square woodpile structure. Namely, ordered sets of rods produce disordered patterns and, vice versa, disordered sets of rods produce ordered patterns. We explain this effect theoretically and experimentally by the fact that light scatters only from the intersection points of different rods.
关键词： light scattering,Laue diffraction,speckle patterns,photonic structures,disorder
更新于2025-09-23 15:21:21