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The characteristics of laser scattered by droplets
摘要： Droplets are the primary factors which in?uence laser transmitting in bad weather. This paper researches the analytic expression of droplets in?uencing the laser, which is based on the geometric optic theory and distribution of raindrop size and shape. In this paper, the relationship between the incidence and emergence angle of droplets is discussed. The e?ects of an individual raindrop on Ladar divergence angle, illuminance and optical path di?erence are investigated, and then the cumulated in?uence of a large quantity of raindrops is analyzed. The illuminance of scanning the targets and laser radar received by the detector is presented.
关键词： illuminance,re?ectivity,incidence angle,divergence angle,Laser ladar
更新于2025-09-11 14:15:04
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Markedly different molecular formation in DPP-based small-molecule solar cells probed by grazing-incidence wide-angle X-ray scattering
摘要： This study comprehensively explores the nanostructural properties of two diketopyrrolo[3,4-c]pyrrole-1,4-dione (DPP)-based small molecules with different alkyl side groups and their blends with the fullerene derivative PC71BM, using grazing-incidence wide-angle X-ray scattering synchrotron techniques. Preferentially relative face-on orientation within the larger and more ordered stacking phase of SM1 with its shorter side group (ethylhexyl) was observed in the majority of both pristine and blend thin films, whereas SM2 crystals showed strictly perpendicular orientation. These contrasting crystalline characteristics led to significant differences in the results, from which crystalline structure–performance property correlations are proposed. Thus, the results not only demonstrate important scientific insights into the relationship between molecular structure and crystalline formation but also provide molecular design directions that will facilitate further improvement to the morphology and performance of DPP-based small-molecule solar cells.
关键词： small-molecule donors,diketopyrrolopyrrole,grazing-incidence wide-angle X-ray scattering,molecular packing structure,small-molecule solar cells
更新于2025-09-11 14:15:04
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[IEEE 2018 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium) - Boston, MA (2018.7.8-2018.7.13)] 2018 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium) - Robust Multi-Layer Graphene-Based Plasmonic Cloaking
摘要： In this paper, a plasmonic cloak is designed at 1.55 μm in an epsilon-near-zero (ENZ) comprised of alternating layers of a graphene-silica stack. Because the inclusion is covered by Au and moreover, the ENZ’s boundaries are sealed by this material with optimized thicknesses, such a cloak can only work for TM incidence. This cloak is robust against the inclusion shape which is capable of working in an exceedingly large bandwidth.
关键词： TM incidence,graphene-silica stack,epsilon-near-zero,plasmonic cloak,robust,large bandwidth
更新于2025-09-11 14:15:04
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Energy losses and transition radiation in graphene traversed by a fast charged particle under oblique incidence
摘要： We perform fully relativistic calculations of the energy loss channels for a charged particle traversing a single layer of graphene under oblique incidence in a setting pertinent to a scanning transmission electron microscope (STEM), where we distinguish between the energy deposited in graphene in the form of electronic excitations (Ohmic loss) and the energy emitted in the far field in the form of transition radiation (TR). Our formulation of the problem uses a definition of two in-plane, dielectric functions of graphene, which describe the longitudinal and transverse excitation processes that contribute separately to those two energy loss channels. Using several models for the electric conductivity of graphene as the input in those dielectric functions enables us to discuss the effects of oblique incidence on several processes in a broad range of frequencies, from the terahertz (THz) to the ultraviolet (UV). In particular, at the THz frequencies, we demonstrate that the nonlocal effect in the graphene’s conductivity is not important in the retarded regime, and we show that the longitudinal and transverse contributions to the emitted TR spectra exhibit strongly anisotropic angular patterns that are readily distinguishable in a cathodoluminescence measurement in a STEM. Moreover, we explore the possibility of exciting the so-called transverse mode in the optical response of graphene at the mid-infrared (MIR) range of frequencies by means of a fast charged particle under oblique incidence. Finally, we demonstrate that, aside from the usual high-energy peaks in the longitudinal contribution to the Ohmic energy loss in the MIR to the UV frequency range, there may arise strongly directional features in the in-plane distribution of the transverse contribution to the Ohmic energy loss for an oblique trajectory, which could be possibly observed via momentum- and angle-resolved electron energy loss spectroscopy of graphene in STEM.
关键词： MIR,energy loss,STEM,THz,transition radiation,UV,graphene,cathodoluminescence,oblique incidence,Ohmic loss
更新于2025-09-11 14:15:04
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Influence of a Surface Finishing Method on Light Collection Behaviour of PWO Scintillator Crystals
摘要： In the ?eld of scintillators, high scintillation and light production performance require high-quality crystals. Although the composition and structure of crystals are fundamental in this direction, their ultimate optical performance is strongly dependent on the surface ?nishing treatment. This paper compares two surface ?nishing methods in terms of the ?nal structural condition of the surface and the relative light yield performances. The ?rst polishing method is the conventional “Mechanical Diamond Polishing” (MDP) technique. The second polishing technique is a method applied in the electronics industry which is envisaged for ?nishing the surface treatment of scintillator crystals. This method, named “Chemical Mechanical Polishing” (CMP), is ef?cient in terms of the cost and material removal rate and is expected to produce low perturbed surface layers, with a possible improvement of the internal re?ectivity and, in turn, the light collection ef?ciency. The two methods have been applied to a lead tungstate PbWO4 (PWO) single crystal due to the wide diffusion of this material in high energy physics (CERN, PANDA project) and diagnostic medical applications. The light yield (LY) values of both the MDP and CMP treated crystals were measured by using the facilities at CERN while their surface structure was investigated by Scanning Electron Microscopy (SEM) and Grazing Incidence X-ray Diffraction (GID). We present here the corresponding optical results and their relationship with the processing conditions and subsurface structure.
关键词： light yield,scintillator crystals,polishing techniques,scanning electron microscopy,grazing incidence X-ray diffraction
更新于2025-09-10 09:29:36
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Reference Module in Chemistry, Molecular Sciences and Chemical Engineering || Synchrotron-based Spectroscopy In On-Surface Polymerization of Covalent Networks
摘要： Synchrotron radiation is a powerful tool to probe physical properties of materials on the nanoscopic scale. It can provide a chemical fingerprint of a nanomaterial with unrivalled resolution, it can measure the geometric structure down to thousands of a nanometer with not only elemental sensitivity but also chemical sensitivity, and it can study charge transfer dynamics in the sub-nanosecond regime. Within this article the application of synchrotron radiation to studying on-surface catalysis, to the view of forming two-dimensional covalent networks, will be explored.
关键词： covalent networks,on-surface polymerization,Normal Incidence X-ray Standing Waves,Synchrotron radiation,X-ray Photoemission Spectroscopy,Near Edge X-ray Absorption Fine Structure
更新于2025-09-10 09:29:36
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Rectangular cavity-based perfect dual-band absorber with wide incidence angle in terahertz region
摘要： In this paper, a dual-band perfect metamaterial absorber(MA) based on rectangular cavity with wide incidence angle is proposed in the terahertz region. The unit of the absorber is composed of three different size rectangular cavities which are placed vertically on a metal plate. The numerical results show that the MA has two distinctive absorption bandwidths from 3.7586 to 4.0977 THz and 5.7635 to 6.0746 THz, respectively, with both absorption rates larger than 90%. Besides, the resonant frequency can be calculated based on rectangular cavity theory, which provides a design guideline for MA of such type. The theoretical predictions of the resonance frequencies have excellent agreements with the simulation ones. What’s more, the physical mechanism of the perfect absorption can be explained based on the distribution of E-field in the absorber and the standing wave theory. Our results provide a new way on realizing perfect absorption based on rectangular cavity.
关键词： terahertz,wide incidence angle,dual-band,metamaterial absorber,rectangular cavity
更新于2025-09-10 09:29:36
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Comparison of UV-Irradiation and Sintering on Mesoporous Sponge-like ZnO Films Prepared from PS-b-P4VP Templated Sol-Gel Synthesis
摘要： Mesoporous ZnO films with large surface-area-to-volume-ratio show great promise in multiple applications, among which solid-state dye-sensitized solar cells (ssDSSCs) have attracted great attention in the field of photovoltaics. An appropriate mesopore size in the nanostructured ZnO films significantly plays an indispensable role in improving the device efficiency resulted from an efficient penetration of dye molecules and solid hole transport material. In the present work, mesoporous sponge-like ZnO films are prepared using sol-gel synthesis templated by a diblock copolymer polystyrene-block-poly(4-vinylpyridine). Two different template removal techniques, UV-irradiation and high temperature sintering, are used to compare their respective impact on the pore sizes of the final ZnO thin films. Both, the surface morphology and the inner morphology show that mesopores obtained via UV-irradiation are smaller as compared to their sintered counterparts. Moreover, increasing the template-to-ZnO precursor ratio is found to further enlarge present mesopores. Accordingly, a strong correlation between the pore sizes of sol-gel synthesized ZnO films and photovoltaic performance of fabricated ssDSSCs is demonstrated. In contrast with the devices fabricated from the UV-irradiated ZnO films, those obtained from sintered samples show more than two times higher efficiency.
关键词： sintering,mesopores,grazing-incidence small-angle X-ray scattering,UV-irradiation,solid-state DSSCs
更新于2025-09-10 09:29:36
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Nanometer-Sized Crystalline Clusters of IGZO Films Determined from the Grazing Incidence X-ray Scattering and Anomalous X-ray Scattering Data Combined with Reverse Monte Carlo Simulations
摘要： Grazing incidence X-ray scattering measurements have been carried out on c-axis aligned crystalline-indium gallium zinc oxide (CAAC-IGZO) ?lm and nanocrystalline category-indium gallium zinc oxide (NC-IGZO) ?lm and the following results were obtained: (1) the characteristic layered structure of the IGZO crystal did not hold its shape and the X-ray scattering pro?le showed only a relatively sharp ?rst peak at the wave vector (Q) = 21.8 for CAAC ?lm and 23.1 nm11 for NC ?lm, respectively, and additional weak broad peaks were observed at a higher angle. (2) In the case of the CAAC ?lm, tiny peaks were observed at Q = 7 and 14 nm11, corresponding to the positions of the 003 and 006 re?ections, respectively, of the IGZO crystal. Such tiny peaks were not detected in the case of NC ?lm but the asymmetry of the ?rst peak at the low angle side was clearly observed. (3) These structural features implied that more than three polyhedral units, such as InOx (x = 4-6), GaOy (y = 4-6), and ZnOz (z = 4-6), were likely to coexist. It is appropriate to call this structural feature as cluster-1. (4) A composite-type structure formed by combining these polyhedral units is also likely to exist and leads to middle-range ordering. This structure is called cluster-2. The size of such cluster-2 has been estimated to be 2.2 nm for CAAC ?lm and 1.8 nm for NC ?lm using the measured pair distribution function. To gain insights into the structural features of IGZO ?lms, realistic atomic-scale models were obtained to ?t not only the ordinary interference function of grazing incidence X-ray scattering but also the environmental interference function of the anomalous X-ray scattering (AXS) with Zn-absorption edge using reverse Monte Carlo (RMC) simulation. (5) The resultant models indicated the complex and irregular atomic arrangements of two types of IGZO ?lms, which are well characterized by nanometer-sized crystalline clusters. This characteristic feature may be referred to as crystalline-cluster-composite (triple C) structure.
关键词： anomalous X-ray scattering,nanometer-sized crystalline clusters,IGZO ?lm,grazing incidence X-ray scattering,reverse Monte Carlo (RMC) simulation
更新于2025-09-09 09:28:46
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[IEEE 2018 International Conference on Advances in Computing, Communications and Informatics (ICACCI) - Bangalore, India (2018.9.19-2018.9.22)] 2018 International Conference on Advances in Computing, Communications and Informatics (ICACCI) - A Modified Frequency Selective Surface Band-stop Filter for Ultra-wideband Applications
摘要： A modi?ed design of a single-layer ultra-wideband (UWB) Frequency Selective Surface (FSS) re?ector is presented for microwave applications. The proposed FSS unit cell consists of a square-loop and a ring printed on opposite sides of a low-cost FR-4 substrate. With the optimized dimensions of the elements, the proposed FSS design provides a stop-bandwidth of 11.94 GHz (5.24-17.18 GHz). It is observed from simulation results that the proposed FSS design has a linear decreasing phase response in the desired band. Furthermore, the presented design provides a stable frequency response up to 450 oblique angle of incidence for both perpendicular (TE) and parallel (TM) polarizations.
关键词： Oblique incidence,Single-layer,FSS re?ector,Ultra-wideband
更新于2025-09-09 09:28:46