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- 2019
- Distributed optical fiber sensing
- Optical frequency domain reflection
- Polynomial regression algorithm
- Nonlinear tuning compensation
- Optoelectronic Information Science and Engineering
- Hebei University of Technology
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Anisotropic infrared light emission from quasi-one-dimensional layered TiS<sub>3</sub>
摘要： Atomically thin semiconductors hold great potential for nanoscale photonic and optoelectronic devices because of their strong light absorption and emission. Despite progress, their application in integrated photonics is hindered particularly by a lack of stable layered semiconductors emitting in the infrared part of the electromagnetic spectrum. Here we show that titanium trisulfide (TiS3), a layered van der Waals material consisting of quasi-one-dimensional chains, emits near infrared light centered around 0.91 eV (1360 nm). Its photoluminescence exhibits linear polarization anisotropy and an emission lifetime of 210 ps. At low temperature, we distinguish two spectral contributions with opposite linear polarizations attributed to excitons and defects. Moreover, the dependence on excitation power and temperature suggests that free and bound excitons dominate the excitonic emission at high and low temperatures, respectively. Our results demonstrate the promising properties of TiS3 as a stable semiconductor for optoelectronic and nanophotonic devices operating at telecommunication wavelengths.
关键词： infrared luminescence,transition metal trichalcogenides,titanium trisulfide,linear polarization anisotropy,layered semiconductors
更新于2025-11-14 14:32:36
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A Reciprocal Formulation of Nonexponential Radiative Transfer. 1: Sketch and Motivation
摘要： Previous proposals to permit nonexponential free-path statistics in radiative transfer have not included support for volume and boundary sources that are spatially uncorrelated from the scattering events in the medium. Birth-collision free paths are treated identically to collision–collision free paths and application of this to general, bounded scenes with inclusions leads to nonreciprocal transport. Beginning with reciprocity as a desired property, we propose a new way to integrate nonexponential transport theory into general scenes. We distinguish between the free-path-length statistics between correlated medium particles and the free-path-length statistics beginning locations not correlated to medium particles, such as at boundary surfaces, inclusions, and uncorrelated sources. Reciprocity requires that the uncorrelated free-path distributions are simply the normalized transmittance of the correlated free-path distributions. The combination leads to an equilibrium imbedding of a previously derived generalized transport equation into bounded domains. We compare predictions of this approach to Monte Carlo simulation of multiple scattering from negatively correlated suspensions of monodispersive hard spheres in bounded two-dimensional domains and demonstrate improved performance relative to previous work. We also derive new, exact, reciprocal, single-scattering solutions for plane-parallel half-spaces over a variety of nonexponential media types.
关键词： Linear transport theory,generalized linear Boltzmann equation,reciprocity,kinetic theory,stochastic media
更新于2025-09-23 15:23:52
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A Runtime-Scalable and Hardware-Accelerated Approach to On-Board Linear Unmixing of Hyperspectral Images
摘要： Space missions are facing disruptive innovation since the appearance of small, lightweight, and low-cost satellites (e.g., CubeSats). The use of commercial devices and their limitations in cost usually entail a decrease in available on-board computing power. To face this change, the on-board processing paradigm is advancing towards the clustering of satellites, and moving to distributed and collaborative schemes in order to maintain acceptable performance levels in complex applications such as hyperspectral image processing. In this scenario, hybrid hardware/software and reconfigurable computing have appeared as key enabling technologies, even though they increase complexity in both design and run time. In this paper, the ARTICo3 framework, which abstracts and eases the design and run-time management of hardware-accelerated systems, has been used to deploy a networked implementation of the Fast UNmixing (FUN) algorithm, which performs linear unmixing of hyperspectral images in a small cluster of reconfigurable computing devices that emulates a distributed on-board processing scenario. Algorithmic modifications have been proposed to enable data-level parallelism and foster scalability in two ways: on the one hand, in the number of accelerators per reconfigurable device; on the other hand, in the number of network nodes. Experimental results motivate the use of ARTICo3-enabled systems for on-board processing in applications traditionally addressed by high-performance on-Earth computation. Results also show that the proposed implementation may be better, for certain configurations, than an equivalent software-based solution in both performance and energy efficiency, achieving great scalability that is only limited by communication bandwidth.
关键词： FPGAs,hyperspectral imaging,on-board processing,ARTICo3,linear unmixing
更新于2025-09-23 15:23:52
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Linear complex susceptibility of long-range interacting dipoles with thermal agitation and weak external ac fields
摘要： An analytical formula for the linear complex susceptibility of dipolar assemblies subjected to thermal agitation, long-range interactions, and an externally applied uniform sinusoidal field of weak amplitude is derived using the forced rotational diffusion equation of Cugliandolo et al. [Phys. Rev. E 91, 032139 (2015)] in the virial approximation. If the Kirkwood correlation factor of the dipolar assembly gK exceeds unity, a thermally activated process arising from the interaction-specific component arises, while for gK < 1 the susceptibility spectrum normalized by its static value is practically unaltered with respect to that of the ideal gas phase.
关键词： long-range interactions,thermally activated process,dipolar assemblies,thermal agitation,Kirkwood correlation factor,linear complex susceptibility
更新于2025-09-23 15:23:52
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[IEEE 2018 48th European Microwave Conference (EuMC) - Madrid, Spain (2018.9.23-2018.9.27)] 2018 48th European Microwave Conference (EuMC) - Low-loss Loaded Line Phase Shifter for Radar Application in X Band
摘要： Losses in the phase shifters of phased arrays are one of the main limitations of these reconfigurable antennas. This contribution presents the design and measured results of variable phase shifters on triplicate suspended transmission lines in the microwave X-band for variable pointing radar applications. The antenna assembly remains passive and with a very low level of losses in the power distribution network and the phase shifters. PIN or varactor diodes are used to control the load on the transmission line. Each of these components has advantages and disadvantages that are discussed in the communication.
关键词： linear array,phase shifter,Pin diode,varactor,suspended strip
更新于2025-09-23 15:23:52
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Multi-point Gaussian States, Quadratic–Exponential Cost Functionals, and Large Deviations Estimates for Linear Quantum Stochastic Systems
摘要： This paper is concerned with risk-sensitive performance analysis for linear quantum stochastic systems interacting with external bosonic fields. We consider a cost functional in the form of the exponential moment of the integral of a quadratic polynomial of the system variables over a bounded time interval. Such functionals are related to more conservative behaviour and robustness of systems with respect to statistical uncertainty, which makes the challenging problems of their computation and minimization practically important. To this end, we obtain an integro-differential equation for the time evolution of the quadratic–exponential functional, which is different from the original quantum risk-sensitive performance criterion employed previously for measurement-based quantum control and filtering problems. Using multi-point Gaussian quantum states for the past history of the system variables and their first four moments, we discuss a quartic approximation of the cost functional and its infinite-horizon asymptotic behaviour. The computation of the asymptotic growth rate of this approximation is reduced to solving two algebraic Lyapunov equations. Further approximations of the cost functional, based on higher-order cumulants and their growth rates, are applied to large deviations estimates in the form of upper bounds for tail distributions. We discuss an auxiliary classical Gaussian–Markov diffusion process in a complex Euclidean space which reproduces the quantum system variables at the level of covariances but has different fourth-order cumulants, thus showing that the risk-sensitive criteria are not reducible to quadratic–exponential moments of classical Gaussian processes. The results of the paper are illustrated by a numerical example and may find applications to coherent quantum risk-sensitive control problems, where the plant and controller form a fully quantum closed-loop system, and other settings with nonquadratic cost functionals.
关键词： Linear quantum stochastic system,Gaussian quantum state,Risk-sensitive quantum control
更新于2025-09-23 15:23:52
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Quantification of collagen fiber structure using second harmonic generation imaging and two-dimensional discrete Fourier transform analysis: Application to the human optic nerve head
摘要： Second Harmonic Generation (SHG) microscopy is widely used to image collagen fiber microarchitecture due to its high spatial resolution, optical sectioning capabilities and relatively non-destructive sample preparation. Quantification of SHG images requires sensitive methods to capture fiber alignment. This paper presents a 2D Discrete Fourier Transform (DFT) based method for collagen fiber structure analysis from SHG images. The method includes integrated Periodicity Plus Smooth Image Decomposition (PPSID) for correction of DFT edge discontinuity artefact, avoiding the loss of peripheral image data encountered with more commonly used windowing methods. Outputted parameters are: the collagen fiber orientation distribution, aligned collagen content and the degree of collagen fiber dispersion along the principal orientation. We demonstrate its application to determine collagen microstructure in the human optic nerve head, showing its capability to accurately capture characteristic structural features including radial fiber alignment in the innermost layers of the bounding sclera and a circumferential collagen ring in the mid-stromal tissue. Higher spatial resolution rendering of individual lamina cribrosa beams within the nerve head is also demonstrated. Validation of the method is provided in the form of correlative results from wide-angle X-ray scattering (WAXS) and application of the presented method to other fibrous tissues.
关键词： Second Harmonic Generation,edge effect artefact correction,Discrete Fourier Transform,optic nerve head,collagen fiber structure,Non-linear microscopy
更新于2025-09-23 15:23:52
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Sparsifying preconditioner for the time-harmonic Maxwell's equations
摘要： This paper presents the sparsifying preconditioner for the time-harmonic Maxwell’s equations in the integral formulation. Following the work on sparsifying preconditioner for the Lippmann–Schwinger equation, this paper generalizes that approach from the scalar wave case to the vector case. The key idea is to construct a sparse approximation to the dense system by minimizing the non-local interactions in the integral equation, which allows for applying sparse linear solvers to reduce the computational cost. When combined with the standard GMRES solver, the number of preconditioned iterations remains small and essentially independent of the frequency. This suggests that, when the sparsifying preconditioner is adopted, solving the dense integral system can be done as efficiently as solving the sparse system from PDE discretization.
关键词： Electromagnetic scattering,Preconditioner,Maxwell’s equations,Sparse linear algebra
更新于2025-09-23 15:23:52
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Do the representative beam data for TrueBeam <sup>?</sup> linear accelerators represent average data?
摘要： If the vendor's representative beam data (RBD) for TrueBeam linear accelerators are to be valid for use in clinical practice, the variations in the beam data used for beam modeling must be small. Although a few studies have reported the variation of the beam data of the TrueBeam machines, the numbers of machines analyzed in those studies were small. In this study, we investigated the variation in the beam data for 21 TrueBeam machines collected from 17 institutions with their agreement. In the exponential regions, the percent depth dose (PDD) values showed very small variation, <1% for all the photon energies analyzed. Similarly, the off‐center ratio (OCR) values also showed small variation for all energies. In the ?eld regions, the standard deviations of the values of dose difference (DD) between the data for each machine and the study average were <1% for ?eld sizes ≥100 × 100 mm2. The maximum distance‐to‐agreement from the average data was <0.5 mm in the penumbra regions. The output factor (OPF) values also showed very small variation (<1%) for all energies and ?eld sizes. Both the PDD and OCR of the average study data showed good agreement with the vendor's RBD for ?eld sizes ≥100 × 100 mm2. The OPF of the average study data also showed good agreement with the vendor's RBD for all ?eld sizes. However, although all the institutions used ionization chambers with similar cavity volumes, the 30 × 30 mm2 ?eld size showed large DD variations (≥2%) in OCR in the ?eld regions. We conclude that the intermachine variability of TrueBeam linear accelerators was very small except for small ?eld dosimetry, supporting the validity of the use of the RBD for clinical applications. The use of the vendor's RBD might greatly facilitate the quick installation of a new linear accelerator.
关键词： commissioning,linear accelerator,representative beam data
更新于2025-09-23 15:23:52
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Investigations on the quantum chemical studies and physico-chemical properties of an opto-electronic material 1-Allyl-2-Aminopyridine-1-ium bromide
摘要： In the present work, the dual approach of quantum chemical studies and experimental characterizations of the title compound 1-Allyl-2-Aminopyridine-1-ium bromide (1A2APB) were carried out for the first time. The molecular geometry of 1A2APB was optimized by density functional theory (DFT) using B3LYP/6-311++G (d,p) basis set. The optimized geometric structural parameters were compared with the experimental findings and discussed. The dipole moment (μ) and first hyperpolarizability (β) were calculated to predict the NLO behavior. The frontier molecular orbital (FMO), molecular electrostatic potential (MESP), Mulliken atomic charge and thermodynamic properties were investigated to get a better insight of the molecular properties. Stability of the compound arising from hyper-conjugative interactions, intra-molecule re-hybridization and charge delocalization within the molecule were analyzed using NBO analysis. Further, 1A2APB was synthesized and good quality single crystals were grown by slow evaporation technique. Studies such as microanalysis and powder XRD were performed to ascertain material composition and phase respectively. The various characteristic functional groups were identified through FT-IR spectroscopic analyses. The NLO efficiency was measured to be about greater than 5 times that of standard KDP. Thermal behaviors were explored by the simultaneous TG/DTA-DSC thermograms. The UV–Vis–NIR spectral data and fluorescence spectrum were recorded to explore the optical transmission and emission properties respectively. The dielectric properties were evaluated as a function of frequency at various temperatures. The photoconducting nature was analyzed through photoconductivity measurement. The Vicker’s microhardness test was performed at room temperature from which the mechanical stability was analyzed through the classical Meyer’s relation.
关键词： Photoconductivity,Powder XRD analysis,DFT calculations,Organic materials,Non-linear optics,Crystal growth
更新于2025-09-23 15:23:52