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A symmetrical dual-beam bowtie antenna with gain enhancement using metamaterial for 5G MIMO applications
摘要： A symmertrical dual-beam end-?re bowtie antenna with gain enhancement is achieved by intergating three pairs of metamaterial (MTM) arrays for 5G MIMO applications. The ?rst pair of MTM array with high refractive index (HRI) are deployed to form a wide beam antenna. The second pair of HRI MTM array are arranged along the end-?re direction (x-direction) in front of the radiators in order to split the single wide beam into dual beam. Besides, the third pair of anisotropic MTM array with HRI along x-direction and near zero refractive along y-direction are incorporated in front of the second pair of MTM array to improve the gain performance. The proposed technique is veri?ed by both the full-wave electromagnetic simulation and experiment, and the simulated and measured results agree very well with each other. Moreover, the measured results reveal that the main beam directions of the proposed antenna point to ±30? with respect to the end-?re direction (0?) over 24.25-27.5 GHz, with a maximum gain of 7.4 dBi at 26GHz and a 4.2 dB gain improvement compared to the wide beam antenna.
关键词： zero index metamaterial,high refractive index,Metamaterial,5G MIMO communications,dual beam
更新于2025-09-23 15:23:52
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On investigations of refractive indices and birefringence of fiber using duplicate and non-duplicate micro-interferograms of double refracting interferometer
摘要： The formula of refractive index of fiber considering the refraction has been reviewed. This formula is used to investigate the effect of refraction on the accuracy of refractive index calculations with different simulated micro-interferograms of duplicate interference fringes with different fringe shifts order. Also a more accurate formula to calculate the birefringence from the non-duplicate interference fringes has been derived and tested to calculate the birefringence of simulated and experiment micro-interferogram. The presented micro-interferograms were automatically analyzed and the contour lines of the bright fringes were determined using Fourier transform technique. A prepared software program takes the contour line of the fringes and automatically calculate the refractive index, the radius, and the birefringence of fiber. A good result was obtained in case of using immersion liquid matches between the parallel and perpendicular refractive indices of fiber.
关键词： image analysis,refractive index profile,interferometry,birefringence of fiber
更新于2025-09-23 15:23:52
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Synthesis of Eu2O3 doped BaO-TiO2-GeO2 based glass-ceramics: Crystallization kinetics, optical and electrical properties
摘要： Eu3+ doped transparent glass-ceramics (GCs) containing non-centrosymmetric ferroelastic Ba2TiGe2O8 (BTG) crystals as the major crystalline phase have been synthesized. BTG crystal phase was generated in the glass matrix with mole percent composition 30BaO-15TiO2-55GeO2 synthesized by melt quenching technique followed by controlled crystallization through ceramming heat-treatment. A di?usion controlled surface crystallization event with zero and constant nucleation rates was determined through a comparative study of some linear and nonlinear solid state reaction models. Nonlinear crystallization kinetics studies facilitated determination of the experimental ceramization temperature and time for fabrication of transparent glass-ceramics containing BTG nanocrystals. XRD, FTIR, TEM and FESEM measurements con?rmed the dispersion of BTG nanocrystals of size 20–100 nm in the glass matrix. Local crystal environment around Eu3+ ions facilitated the enhancement of photoluminescence of glass-ceramics with respect to the precursor glass. High dielectric constant, low loss and dissipation factors were observed for the GCs.
关键词： Refractive index,Glass-ceramics,Photoluminescence,Dielectric properties,Crystallization kinetics,Hysteresis loop
更新于2025-09-23 15:23:52
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Non-destructive inspection of food and technical oils by terahertz spectroscopy
摘要： Quality control and non-destructive monitoring are of notable interest of food and pharmaceutical industries. It relies on the ability of non-invasive inspection which can be employed for manufacturing process control. We hereby apply terahertz (THz) time-domain spectroscopy as non-destructive technique to monitor pure and degraded oils as well as hydrocarbon chemicals. Significant differences in the spectra of refractive index (RI) and absorption coefficient arising from the presence of ester linkages in the edible and technical oils were obtained. Explicit increase from 1.38 to 1.5 of the RI in all THz spectrum range was observed in hydrocarbons and mono-functional esters with the increase of molar mass. This fact is in contrast of RI dependence on molar mass in multi-functional esters, such as Adipate or vegetable oils, where it is around 1.54. Degradation products, Oleic Acid (OA) and water in particular, lead only to some changes in absorption coefficient and RI spectra of vegetable oils. We demonstrate that complex colloidal and supramolecular processes, such as dynamics of inverse micelles and oil hydrolysis, take part during oil degradation and are responsible for non-uniform dependence of optical properties on extent of degradation.
关键词： absorption coefficient,terahertz spectroscopy,oils,degradation,non-destructive inspection,refractive index
更新于2025-09-23 15:23:52
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Luminescent, optical, magnetic and metamaterial behavior of cerium complexes
摘要： The complexes of cerium with nitrogen, oxygen and sulfur donor ligands were prepared by conventional method. These newly synthesized complexes were characterized by FTIR, UV-Vis, DART Mass, TGA, PXRD, SEM and TEM techniques. The magnetic studies were carried out by the vibrating sample magnetometer. The optical constants were measured by absorption and reflection spectra as a function of wavelength. The concentration dependence of refractive index and absorption were observed by the experimental method, which reveals that these parameters are affected by change in concentration. The optical band gap obtained from Tauc-plot indicates its probability to be a good semiconductor. The luminescence behavior of these cerium complexes were observed by the absorption and emission spectra and the emission life time were calculated by their life time spectra.
关键词： Optical band gap,Luminescence,Refractive index,Magnetic studies
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Saint Petersburg, Russia (2018.10.22-2018.10.23)] 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Monitoring of Flowing Media State by Refraction Phenomenon
摘要： A paper the refraction phenomenon for condition control of flowing media is considered. The peculiarity of flowing liquid condition control by displacement of the light-shadow boundary are determined. The results of experimental investigations are presented.
关键词： refraction,refractive index,full internal reflection,stream of fluid flow
更新于2025-09-23 15:23:52
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Thin Films of Barium Strontium Titanate from the Viewpoint of Light-Based Applications
摘要： In this paper we report results from optical transmittance spectroscopy complemented with data on structure from XRD measurements to determine optical properties of a series of as-deposited and annealed (at 900 °C) BaSrTiO3 (BST) thin films deposited by RF magnetron sputtering. The members of the series differ by the substrate temperature and additional oxygen to accompany argon in the deposition chamber. The perovskite structure with weak preferred (110) orientation was detected for annealed BST thin films whilst the as-deposited films were amorphous. Dispersive optical properties – refractive indices, absorption coefficients and optical band gaps were determined from transmittance spectra. After annealing refractive indices increase to prove the densification of material accompanied by the thickness shrinkage. Optical band gaps calculated either by Tauc procedure or determined as iso-absorption levels are also found to be deposition dependent.
关键词： absorption coefficient,thin films,barium strontium titanate,refractive index,optical band gap
更新于2025-09-23 15:23:52
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Proposal of Novel Optical Model for Light-Diffusing Film Having Alternating Polymer Layers with Different Refractive Indices
摘要： We have proposed the novel optical model for layer structure film to precisely control light diffusion angle range. By introducing structure characteristics to the phase grating model, we successfully constructed the novel optical model. In addition, we clarified that difference of refractive indices of layer structure and layer width are important factors for precisely control of light diffusion angle range.
关键词： diffraction,light-diffusing film,optical model,refractive index,layer structure
更新于2025-09-23 15:23:52
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Silicon-Based Embedded Trenches of Active Antennas for High-Responsivity Omnidirectional Photodetection at Telecommunication Wavelengths
摘要： Although the use of plasmonic nanostructures for photodetection below the band gap energy of the semiconductor has been intensively investigated recently, efficiencies of such hot electron-based devices have, unfortunately, remained low because of the inevitable energy loss of the hot electrons as they move and transfer in active antennas based on metallic nanostructures. In this work, we demonstrate the concept of high-refractive-index material-embedded trench-like (ETL) active antennas that could be used to achieve almost 100% absorbance within the ultrashallow region (approximately 10 nm) beneath the metal?semiconductor interface, which is a much smaller distance compared with the hot electrons’ mean free path in the noble metal layer. Taking advantage of these ETL-based active antennas, we obtained photoresponsivities under zero bias at wavelengths of 1310 and 1550 nm of 5854 and 693 nA mW?1, respectively—values higher than most those previously reported for active antenna-based silicon (Si) photodetectors that operate at optical telecommunication wavelengths. Furthermore, the ETL antenna strategy allowed us to preserve an omnidirectional and broadband photoresponse, with a superior degree of detection linearity of R2 = 0.98889 under the light of low power density (down to 11.1 μW cm?2). The photoresponses of the ETL antenna-based device varied by less than 10% upon changing the incident angle from normal incidence to 60°. Because these ETL-based devices provide high responsivity and omnidirectional detection over a broad bandwidth, they show promising potentials for use in hot electron-based optoelectronics for many applications (e.g., Si photonics, energy harvesting, photocatalysis, and sensing devices).
关键词： hot electron,embedded,plasmon,Schottky,high-refractive-index material
更新于2025-09-23 15:23:52
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Modeling of Radiative Properties of Polystyrene Foams Containing IR-Opacifiers
摘要： The addition of opacifiers in foams considerably reduces the radiative thermal conductivity and consequently enhances the insulation performance of the foams. In this work two different methods were developed to calculate the spectral specific extinction coefficient of opacified extruded polystyrene (XPS) foam material. Cell morphology and thermal conductivity of two identical XPS-foams, one opacified with 3 wt% carbon black as opacifier and one without opacifier, were thoroughly characterized. The experimental results were in a good agreement with the theoretical results obtained from two different computing techniques. These methods allow a good prediction of the specific extinction coefficient of arbitrary opacified foam material.
关键词： Radiative transfer,Radiative thermal conductivity,Complex refractive index,Extinction coefficient,Porous materials,Opacifiers
更新于2025-09-23 15:23:52