- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Efficient three-dimensional atom localization using probe absorption in a diamond-configuration atomic system
摘要： A new scheme for three-dimensional (3D) atom localization is proposed based on measuring the probe absorption spectra in a four-level diamond-configuration atomic system, in which the atom interacts with three orthogonal standing-wave laser fields. Due to spatial-dependent interaction between atom and fields, position information of the atom can be obtained by measuring the absorption spectra of the weak probe field. The results show that atom localization properties can be significantly improved and some interesting spatial localization structures such as double-layer lantern-like, single-layer lantern-like, gourd-like, cylinder-like, and ellipsoid-like patterns can be achieved when we adjust system parameters properly. Most importantly, we can find the atom at a particular position in 3D space with 100% probability under appropriate conditions.
关键词： probe absorption,3D atom localization,standing wave
更新于2025-09-23 15:22:29
-
Fabrication and electromagnetic wave absorption property of quartz ceramics with a gradient distribution of BaTiO3
摘要： Quartz ceramics with a uniform/gradient distribution of BaTiO3 (U/G–SO–BTO) are fabricated by cold pressing a powder blend with BTO followed by sintering and using a combined technique of spreading the powder blends with gradually increased BTO layer–by–layer and sintering. The electromagnetic wave absorption properties of these two ceramics are studied in detail. For U–SO–BTO samples, the primary electromagnetic re?ection is strong due to the aggravated impedance mismatch at their surfaces. The electromagnetic wave re?ectivity of U–SO–BTO could only reach ?7.0 dB when the sample thickness is 6 mm and the BTO content is 8.0 wt%, and it decreases slightly to ?8.1 dB when the sample thickness is increased to 10.0 mm and the BTO content is decreased to 5.0 wt% simultaneously. For G–SO–BTO samples, electromagnetic waves could enter with little re?ection due to the weak surface impedance mismatch, and the electromagnetic waves entering these samples could propagate forward while being absorbed gradually with little re?ection because of the weak impedance mismatch at the interfaces. The G–SO–BTO samples are promising excellent electromagnetic absorbing materials because their electromagnetic wave re?ectivity could reach a level lower than ?12.0 dB and could decrease further from –12.2 to ?13.1 dB as the layer thickness increases from 1.0 to 2.0 mm.
关键词： Impedance mismatch,Electromagnetic wave absorption,Quartz ceramics,Electromagnetic re?ection,Gradient distribution,BaTiO3
更新于2025-09-23 15:22:29
-
Defects anomaly in cobalt-doped ZnO nanostructures using optical and charge transient analysis
摘要： The significant effect of electrically active defects present in the device, which limits the carrier mobility, generated due to cobalt doping via the co-precipitation technique in a ZnO matrix, has been investigated on the basis of its structural, optical and charge transient behaviours. The variations observed in the absorbance and extinction coefficients as a function of wave length reveal the presence of defect states, a range of localized states and structural disorder. The presence of a non-uniform trap centre density in the material has been measured on the basis of different operational modes in charge-deep level transient spectroscopic analysis. A disparity of such a kind in the structures at the nanoscale will provide for a remarkable approach to improve the performance and reliability of the smart electronic, optoelectronics, photonics and sensing devices.
关键词： absorption coefficient,ZnO,Defect density,Q-DLTS,Nano structures,extinction coefficient
更新于2025-09-23 15:22:29
-
Validation of MODIS-Aqua bio-optical algorithms for phytoplankton absorption coefficient measurement in optically complex waters of El Rincón (Argentina)
摘要： El Rincón is a highly productive area in the inner-shelf of the Argentine Sea, southern Buenos Aires Province (39°S–62.5°W; 41.5°S–60°W), regarded as the habitat for commercially valuable ?sh species and important for local artisanal ?sheries. The aims of this work were to characterize for the ?rst time the in situ absorption coe?cient of phytoplankton (aph(λ)) in relation to phytoplankton composition and chlorophyll-a (Chl-a) concentration, and to evaluate the satellite retrieval of aph(443) using two atmospheric correction algorithms and three bio-optical semi-analytical algorithms in order to de?ne which is more suitable for the study area. A total of 28 oceanographic cruises were performed between November 2013 and March 2017 and the sampling included physical variables (temperature, salinity, suspended particulate matter, SPM), Chl-a, phytoplankton absorption and composition. The phytoplankton community was mainly dominated by chain-forming diatoms from the microplankton size class (40–80%), while a single coccolithophore, Gephyrocapsa oceanica (cell diameter < 10 μm) was a key component (up to 40%) of the nanoplankon. In situ Chl-a (mean 1.8 mg m?3) and aph(443) (mean 0.052 m?1) generally covariated with no clear seasonality. Their correlation was rather low (R2 = 0.52) and with high scattering, in agreement with the high interannual variability of phytoplankton composition. Further, the relative low mean speci?c absorption coe?cient of phytoplankton (aph*(443), 0.032 m2 (mg Chl-a)?1) and (aph*(676), 0.014 m2 (mg Chl-a)?1) denoted the presence of big cells and pigment packaging e?ect. Aside from the optical complexity of these waters, reasonable results were found using the Quasi Analytical Algorithm in retrieving aph coe?cient (R2 = 0.55, Bias = 19%) and switching the atmospheric correction algorithm depending on the distance to the coast, the depth and turbidity. The results found in this paper present for the ?rst time the phytoplankton composition and absorption of algal material characteristics and the derived implication on the performance of bio-optical algorithms in the optically complex waters of El Rincon.
关键词： Absorption by phytoplankton,Bio-optical algorithms,Turbid coastal waters,Phytoplankton composition,Validation,MODIS-Aqua
更新于2025-09-23 15:22:29
-
[IEEE 2018 Cross Strait Quad-Regional Radio Science and Wireless Technology Conference (CSQRWC) - Xuzhou (2018.7.21-2018.7.24)] 2018 Cross Strait Quad-Regional Radio Science and Wireless Technology Conference (CSQRWC) - The Design and Experimental Verification of Broadband Absorbing Structure Combined by A1<inf>2</inf>O<inf>3f</inf>/ Al<inf>2</inf>O<inf>3</inf>Compositesand Metamaterials
摘要： With the aim to design a particular electromagnetic (EM) wave absorbing structure for broadband frequency used at high temperature, a multi-layer structure was proposed by combing the dielectric materials and square patch metamaterial. The absorbing structure was fabricated by precursor infiltration and pyrolysis technique and screen printing process. The computational and experimental results showed that a maximum reflection loss could be lower than ?7dB at 2-18GHz with a total thickness of 9mm. This effective enhancement on EM wave absorption property was believed to be a consequence of multi-layer and resonance effect induced by combining the traditional EM absorbing materials with metamaterial structure.
关键词： Electromagnetic wave absorption properties,Computation,Ceramic matrix composites
更新于2025-09-23 15:22:29
-
Performance Analysis of a Solar-Powered Multi-Effect Refrigeration System
摘要： The main objective of the current work is to investigate the thermodynamic performance of a novel solar powered multi-effect refrigeration system. The proposed cycle consists of a solar tower system with a heliostat field and central receiver (CR) that has molten salt as the heat transfer fluid, an absorption refrigeration cycle (ARC), an ejector refrigeration cycle (ERC), and a cascade refrigeration cycle (CRC). Energy and exergy analyses were carried out to measure the thermodynamic performance of the proposed cycle, using Dhahran weather data and operating conditions. The largest contribution to cycle irreversibility was found to be from the CR system (52.5%), followed by the heliostat field (25%). The first and second-law efficiencies improved due to the increase in the following parameters: ejector evaporator temperature, turbine inlet and exit pressures, and cascade evaporator temperature. Parametric analysis showed that the compressor delivery pressure, turbine inlet and exit pressures, hot molten salt outlet temperature, and ejector evaporator temperature significantly affect the refrigeration output.
关键词： triple effect,refrigeration,ejector,cascade,solar energy,absorption
更新于2025-09-23 15:22:29
-
Generation of optical signal and terahertz idler photons by spontaneous parametric down-conversion
摘要： Frequency-angular characteristics of signal and idler photons generated under spontaneous parametric down-conversion are studied in a strongly frequency nondegenerate regime, without paraxial approximation, accounting for possible inherent absorption of idler waves in a nonlinear crystal, classical thermal field fluctuations, and the multimode character of parametric interaction induced by transverse spatial limitation of the pump beam. Spatial limitation is shown to lead to a huge increase in angular divergence of the idler photons generated at terahertz frequencies. General expressions are obtained for the frequency-angular sensitivity function of the nonlinear-optical terahertz wave detector and for power densities of the signal and idler photon fluxes. The absorption-induced difference in the parametric conversion coefficients for the noise and externally incident radiation of the idler frequency is shown to be described by approximately the same loss factor for all active spatial idler modes. Two different parametric contributions of the internal thermal noise to the number of output idler photons were revealed with different dependence on the idler-wave absorption. Expressions for the loss factors, which describe absorption-induced effects in signal and idler channels, are obtained and shown to be turning into one another by changing the sign of the absorption coefficient. Relative contribution of thermal and quantum field fluctuations into the intrinsic radiation of a nonlinear crystal at signal and idler frequencies is analyzed accounting for the crystal absorption properties.
关键词： nonlinear optics,thermal fluctuations,terahertz,quantum fluctuations,absorption,spontaneous parametric down-conversion
更新于2025-09-23 15:22:29
-
[IEEE 2018 IEEE 38th International Conference on Electronics and Nanotechnology (ELNANO) - Kiev (2018.4.24-2018.4.26)] 2018 IEEE 38th International Conference on Electronics and Nanotechnology (ELNANO) - Influence of Spin-Orbit Interaction on the Magneto-Optical Spectra of InSb Quantum Rings
摘要： The theoretical calculations of dependences of energy levels and absorption spectra of electrons in the quantum ring by a quasi-parabolic shape on the applied external magnetic field were carried out. The influence of spin-orbit interaction was taken into account in these calculations. Spin-orbit interaction leads to appearance of change in the dependence of absorption frequency of quantum rings on applied magnetic field.
关键词： spin-orbit interaction,absorption spectrum,quantum ring
更新于2025-09-23 15:22:29
-
Evaluating impact damage to fabric-based personal armor by infrared NDT
摘要： The paper considers the thermo-mechanical mechanism of interaction between the damage agents and armor protection made of polymer fabrics. A simplified mathematical model is proposed to describe the deceleration of a damage agent within an armor fabric due to the dissipation of energy expended on irreversible stretching deformations of fabric fibers, as well as fiber slipping friction and material heating. Woven fabric layers are replaced by solid layers characterized by averaged stiffness and viscosity. A discrete numerical model of a solid material is proposed to reduce a problem with a finite number of degrees of freedom; motion equations are obtained on the basis of the Lagrange equations of the second kind, and for their integration, a stable non-conservative difference scheme is used. The software implementation is based on a functional-object paradigm which allows the modeling of conjugated processes. The parameters of governing equations are identified by using the experimental data. Some illustrative examples of interaction between damage agents and armor barriers with different arrangement of fibers are presented. The proposed model can be used to predict the quality of armor protection with the changing number and location of fibers, as well as to test the armor protection by applying the technique of infrared thermography.
关键词： Armor protection,mathematical model,irreversible deformation,infrared thermography,energy absorption,numerical scheme,composite material,fiber friction
更新于2025-09-23 15:22:29
-
Optical diffraction radiation from a dielectric and a metal nanowire excited by a modulated electron beam
摘要： The optical diffraction radiation that accompanies the motion of a modulated beam of electrons near a dielectric and silver nanowire scatterers is investigated in the two-dimensional formulation. Our goal is to compute the field in the near and far zones and analyze how it depends on electron beam parameters. We demonstrate the excitation of internal resonances of such a scatterer that can be useful in the design of nanoscale non-invasive beam position monitors.
关键词： Plasmon resonance,Diffraction radiation,Nanowire scatterers,Total scattering cross-section,Absorption cross-section,Smith–Purcell effect,Surface wave
更新于2025-09-23 15:22:29