查看更多>>摘要：Switchable multi-function metasurfaces have received much attention due to their excellent performance of manipulating electromagnetic waves. In this paper, we present a novel design that can realize a high-efficiency absorber and an ultra-wideband circular polarization converter based on an anisotropic metasurface through the phase transition of vanadium dioxide (VO2). At room temperature, the metasurface acts an ultra-wideband circular polarization converter with the VO2 film maintains an insulating state, the theoretical analysis and numerical simulation show that the polarization conversion ratio reaches more than 90% in an ultra-wide band (6.3-15.0 THz) and even reaches almost 100% at two peaks, the relative bandwidth is 82%. When the temperature increases to 68 degrees, the metasurface becomes a high-efficiency absorber with VO2 film in metallic state. Numerical calculations show that the absorber has over 90% high-efficiency absorption of X-linearly polarized wave in the 10.8-13.2 THz frequency range and over 90% highe-fficiency absorption of left-handed circular polarization wave in the 10.8-14.4 THz frequency range, both are angle insensitivity for small incident angles from 0 degrees to 20 degrees. The physical mechanisms of the two functions based on our structure are discussed. Our novel design has potential significance in future terahertz medical imaging, non-destructive detectors, polarization converters, and THz communication system.
Alrowaili, Z. A.Alomairy, SultanOlarinoye, I. O.Mutuwong, Chalermpon...
10页
查看更多>>摘要：In this study we present the optical features including several parameters, gamma-ray photon and fast neutron absorption parameters of quaternary glasses with the chemical structure: xBi(2)O(3) + (80-x)TeO2 + 10B(2)O(3) + 10GeO(2) for x = 40, 50, and 60 mol% and coded as Bi/Te-BGe1, Bi/TeBGe2, and Bi/Te-BGe3 respectively. The FLUKA Monte Carlo and XCOM code were used to evaluate the photon shielding parameters of the glasses for energies between 0.284 and 2.506 MeV. The optical quantities such as the molar refractivity R-m, molar polarizability alpha(mol), reflectance loss (R-loss), optical transmission (T-opt), metallization criterion (M) and the static dielectric constant epsilon(sta)of the glasses were estimated to understand their optical characteristic. Mass attenuation coefficient of 0.345, 0.368, and 0.386 cm(2)/g was obtained for Bi/Te-BGe1-3 respectively at 0.284 MeV. Evaluated Z(eff) ranged from 30.94 to 53.22, 32.73 - 56.29, 34.52 - 58.75 for the Bi/ Te-BGe1-3 glasses respectively. The HVL within the investigated energy similar to other estimated photon shielding parameters showed great enhancement as the density and Bi2O3 content of the glasses improved. Similar improvement on the fast neutron removal cross section also increased from 0.1141 to 0.1178 cm(-1) as bismuth oxide increases in the glass system. The estimated optical parameters also showed great dependence on the chemical structure of the glasses. The present Bi/Te-BGe1-3 glasses showed excellent fast neutron and photon absorption capacity compared to some common shields; this makes them potentially useful for radiation protection applications.
查看更多>>摘要：This study investigates a pyridinium-based NLO crystal 4-N, N-dimethylamino-4'-N'-methyl-stil-bazolium 3,4-dimethoxysulfonate (DOST) containing the strong electron donor, which act the electron and hydrogen bond donors. A DOST signal crystal with a size of 2 x 5 x 1 mm(3) has been grown in methanol solution by the slow cooling growth method. Physical property measurements indicate DOST crystal possesses a strong second harmonic generation response that is 8 times that of KH2PO4 (KDP) crystal and a bandgap of 2.90 eV, making it very promising for nonlinear optical applications. The NLO properties as dipole moment, polarizability, first order hyperpolarizability are performed using density functional theory (DFT) method. Benefiting for the near-perfect alignment of DOS cations, DOST crystal exhibits a large diagonal component of the effective hyperpolarization, about 105.21 x 10(-30) esu. Furthermore, information about the sites of intermolecular interaction has been obtained by molecular electrostatic potential (MEP) surface and Hirshfeld Surface. In order to understand the electronic properties, the absorption wavelengths, excitation energies, oscillator strength, the frontier molecular orbitals and global reactivity descriptors are also calculated.
查看更多>>摘要：One of the most promising methods for early detection of certain cancers, infections, metabolic disorders, and some other diseases is the analysis of specified volatile organic compounds (VOC) biomarkers present in patients' bio-fluids and exhaled breath. Biosensors based on Localized surface plasmon resonance (LSPR) have the potential of real time detection of a monolayer of diagnostic biomarkers. This paper presents a wavelength-interrogated plasmonic biosensor with tunable sensitivity and selectivity performance toward VOC biomarkers detection. With the purpose of improving the dynamic detection range of the biomarker refractive indices (RI) in visible wavelengths, the effect of the thickness and configuration of the gold layer is studied. The performance of the designed biosensor is investigated by finite element method via COMSOL Multiphysics for various biomarkers. The numerical results show that the sensor based on the continuous metallic thin films patterned with periodic shallow cavities could be calibrated for several biomarkers with RI ranging from 1.329 to 1.436 in visible spectrum.
查看更多>>摘要：Adaptive digital fringe projection (AFP) technique is a traditional approach to measure the high dynamic range (HDR) surface. However, the projected light intensities are difficult to determine. And there are some discrepancies occurred in the location of detected strip-edge. In this paper, a projection intensities determination strategy was proposed to minimize the influence of camera response nonlinear distortion and improve the robustness of strip-edges detection. To determine the relationship between the projected gray level and the captured gray level, the mapping function between the projector and the camera is established. To evaluate the distortion degree of the captured image, the camera response nonlinear distortion model is proposed. Compared with the traditional AFP method, the proposed method is relatively simple and flexible. And the proposed method could be satisfying the different user demands. The experiment shows that the influence of nonlinearity of camera response was reduced and the robustness of strip-edge detection is improved.
Kavas, TanerAlsufyani, Sultan J.Alrowaili, Z. A.Tamam, Nissren...
12页
查看更多>>摘要：The physical, optical, mechanical, and radiation absorption features of a Sodium-bariumvanadate glass system containing iron (III) oxide were obtained by direct calculations and Monte Carlo simulations in this study. The investigated glasses have a chemical definition given as (20 - x)Na2O + 25BaO + 55V(2)O(5) + xFe(2)O(3) (where x = 0, 5 10, 20 mol% represents SBVFe0-3). The mass density from 3.732 to 4.326 g cm(-3) while molar volume decreased from 40.40 to 39.37 cm(3) mol(-1) as the Fe2O3 insertion ratio rose in the glasses. Replacing Na2O with Fe2O3 in the glasses led to a decrease in the refraction index, reflectance loss, and metalization criterion of the glasses, while on the other hand the optical transmittance increased. The Young's, longitudinal, bulk, and shear moduli all increased as the glass density improved. The gamma radiation shielding competence evaluated from FLUKA simulations and confirmed by XCOM calculations revealed that the incident photon energy and the chemical structure of the glasses influenced the photon absorbing capacity of the glasses. The linear attenuation coefficient decayed from 0.4852 to 0.1409 cm(- 1) for SBV-Fe0 while that of SBV-Fe1, SBV-Fe2, and SBV-Fe3 decayed from 0.5021 to 0.1479 cm (-1), 0.5203 to 0.1544 cm (-1), and 0.5573 to 0.1656 cm(- 1) accordingly as energy increases from 0.284 to 2.506 MeV. Similarly, the mass attenuation coefficient, effective atomic number and other estimated photon absorption quantities all point to an improved absorption capacity with the trend SBV-Fe0 < SBV-Fe1 < SBV-Fe2 < SBV-Fe3. Further, the sigma(R) of the glasses have values of 1.2162, 1.1977, 1.1919, and 1.213 cm(- 1) for the SBV-Fe0-3 respectively. Analysis of the thermal neutron cross section of the glasses reveals that the inclusion and subsequent increase of the Fe2O3 content of the SBV-Fe glasses has a positive impact on the thermal neutron interaction parameters. SBV-Fe glasses are valuable materials for radiation absorption functions when compared with common shields.
查看更多>>摘要：Spectral efficiency is an important parameter to characterize the optical performance of optical filters in thermophotovoltaic systems. The multilayer filters are normally designed by assuming ideally flat interfaces, but realistic structures have a degree of interface roughness present. This work explores the influence of interface roughness on the spectral efficiency, with examples including structures with different materials or number of layers.
查看更多>>摘要：Partial Shading Conditions (PSCs) significantly impact the output power performance of a Photovoltaic (PV) solar array. Such an issue can be addressed by partly or wholly cross-tying the modules in the array rows and reconfiguring the positions of these modules within it. This paper proposes a novel Magic Square-Enhanced Configuration (MS-EC) algorithm to overcome the partial shading issues. Hence, the proposed algorithm disperses the shading effects more evenly over the entire array surface, reducing the conductions losses due to the bypass diode operation. When using the MS-EC scheme, PV modules are physically re-wired and moved into other locations in the array structure without altering their electrical connections. The key advantage of the MS-EC reconfiguration over the existing techniques is that it requires fewer iterations, easing the Maximum Power Point Tracking of the array. The performance of the proposed algorithm is assessed using several indicators, such as maximum power generation, number of iterations required, complexity and mismatched power losses. MATLAB-SIMULINK software environment is used to simulate the MS-EC scheme. Hence, the former method compares favourably with the existing techniques and a traditional Tied-Cross-Ties (TCT) configuration, giving average power improvements of 16-43% under most of the realistic weather conditions.
Kumari, NeelamKumar, MukeshDalal, HinaMalik, R. K....
15页
查看更多>>摘要：An orthorhombic symmetry type BaGd2ZnO5:Dy3+ nanocrystals with luminance of cool white-color light have been fabricated via urea assisted combustion methodology. Morphological analysis revealed the agglomerated particles with non-uniform shape having crystal-size of 30-40 nm. Optimized amount of dopant (Dy3+) was examined to be x = 3 mol%, after the occurrence of quenching phenomenon. The logical pathways for quenching mechanism has been determined as non-radiative (NR) relaxations of energy via exchange-type interrelations as validated by Inokuti-Hirayama (I-H) and Dexter's theory. Fabricated nano-powders represents two band located at 492 nm (bluish) and at 581 nm (yellowish). Band gap, decay life time and quantum efficiency of optimal powder were found as 4.71 eV, 0.7049 ms and 93.9% respectively. White-light emanation is reflected in terms of CIE color-parameters like color-coordinates of white regions (0.2869, 0.3876), color purity of 30 x 10(-2) and CCT values as 7206.2 K, which have been in congruence with standard coordinates of commercial LEDs and NTSE and thus, authenticate their optimistic applicability for advanced illuminating devices.
查看更多>>摘要：We compared the morphology and Raman response of nanoscale shaped surfaces of Si substrates versus monocrystalline Si. Samples were structured by reactive ion etching, and four of them were covered by a RuO2-IrO2 layer. Raman bands, centred at approx. 520 cm(-1), belonging to samples processed by etching the Si surface have intensities higher by approximately one order of magnitude than those of reference non-etched samples. For nanostructured samples, the rise in the Raman signal was 12-14 x, which is in agreement with the model of the electric field at the tips of Si due to their geometry. This phenomenon is related to the high absorption of excitation radiation. Nanostructured surfaces of samples containing a layer of RuO2-IrO2 give rise to the phenomenon of surface enhancement of the Raman response most likely due to the charge transfer at the interface between silicon and conductive oxides. The nanostructured surface of Si without a metal layer behaves as a SERS substrate and detects the analytes at a low concentration.
NSTL
Elsevier