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Recent Advances in Brillouin Optical Correlation-Domain Reflectometry
摘要： Distributed ?ber-optic sensing based on Brillouin scattering has been extensively studied and many con?gurations have been developed so far. In this paper, we review the recent advances in Brillouin optical correlation-domain re?ectometry (BOCDR), which is known as a unique technique with intrinsic single-end accessibility, high spatial resolution, and cost ef?ciency. We brie?y discuss the advantages and disadvantages of BOCDR over other Brillouin-based distributed sensing techniques, and present the fundamental principle and properties of BOCDR with some special schemes for enhancing the performance. We also describe the recent development of a high-speed con?guration of BOCDR (slope-assisted BOCDR), which offers a beyond-nominal-resolution detectability. The paper is summarized with some future prospects.
关键词： Brillouin scattering,optical fiber sensing,temperature sensing,distributed sensing,structural health monitoring,optical correlation-domain reflectometry,strain sensing,nonlinear optics
更新于2025-09-23 15:21:21
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Application and Extension of Vertical Intensity Lower-Mode in Methods for Target Depth-Resolution with a Single-Vector Sensor
摘要： In this paper, based on the reactive component of the vertical intensity, the method for target depth resolution has been improved. In the previous existing research results, using the reactive component of vertical intensity, the research objects for target depth resolution in shallow water, can only be the targets whose frequencies can only excite the ?rst two normal modes, and the depth of targets whose frequencies excite more than two normal modes cannot be correctly identi?ed. The basic idea of the improved method is to classify targets on the foundation of the lower-mode correlation quantity of the vertical intensity. Based on the improved method, we can realize depth resolution of the targets whose frequency can excite the ?rst three normal modes so as to effectively expand the working band useful for target depth resolution. Finally, we can realize the three-dimensional target depth resolution so as to distinguish the aerial, surface and underwater targets. The feasibility of the algorithm is veri?ed by simulation and experimental data processing.
关键词： ?rst three normal modes,improved method,lower-mode correlation quantity,Monte Carlo,depth resolution
更新于2025-09-23 15:21:21
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[Advances in Intelligent Systems and Computing] Soft Computing for Problem Solving Volume 817 (SocProS 2017, Volume 2) || Temperature Resolution and Spatial Resolution Improvement of BOCDR-Based DTS System Using Particle Swarm Optimization Algorithm
摘要： Temperature resolution and spatial resolution are major performance metrics in any distributed temperature sensing (DTS) system. In this paper, we have presented a detailed analysis on the performance of a Brillouin optical correlation domain reflectometry (BOCDR)-based DTS (BOCDR-DTS) system. Particle swarm optimization (PSO) evolutionary algorithm is being used in this paper to improve the performance of the proposed BOCDR-DTS system. Using this optimization algorithm, we minimized the Brillouin frequency shift (BFS) error in sensing system. As a consequence of this, the achieved temperature and spatial resolution are ~0.839 °C and ~43 cm, respectively. The results were simulated using MATLAB version 15.0.
关键词： Spontaneous Brillouin scattering,Distributed temperature sensing,Particle swarm optimization (PSO),Temperature resolution and spatial resolution,Brillouin frequency shift,Optical correlation domain reflectometry (OCDR)
更新于2025-09-23 15:21:21
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[IEEE 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Odessa, Ukraine (2018.9.4-2018.9.7)] 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Correlation Properties of Additive Linear High-Order Markov Chains
摘要： The aim of this paper is to study the statistical properties of the Nth order correlated Markov chains, which have a large application area in the UWB signal generation, transmission and processing. The state space of the chain under consideration is supposed to be a finite set of real numbers. The transition probability function is assumed to be homogeneous, additive and linear with respect to the values of random variable. The equations relating the correlation functions of the sequence to the memory function, which determined by the transition probability function, are derived and solved. The obtained analytical solutions for the correlation functions are compared with the results of numerical simulations. Examples of possible correlation scenarios in additive linear chains of higher orders are given. The obtained results can be useful both in analytical and simulative context, for example, for the modeling of the UWB transmission channels, for the refinement of transmitter and receiver design, for the enhancement of coding methods suitable for the UWB communication systems.
关键词： UWB channels,higher order Markov chain,memory function,linear additive high-order Markov chain,correlation function
更新于2025-09-23 15:21:21
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Generalized gradient approximation exchange energy functional with near-best semilocal performance
摘要： We develop and validate a non-empirical generalized gradient approximation (GGA) exchange (X) density functional which performs as well as the SCAN meta-GGA on standard thermochemistry tests. Additionally, the new functional (“NCAP”) yields Kohn-Sham eigenvalues that are useful approximations of the density functional theory (DFT) ionization potential theorem values by inclusion of a systematic derivative discontinuity shift of the X potential. NCAP also enables time-dependent DFT (TD-DFT) calculations of good quality polarizabilities, hyper-polarizabilities, and one-fermion excited states without modification (calculated or ad hoc) of the long-range behavior of the exchange potential or other patches. NCAP is constructed by reconsidering the imposition of the asymptotic correctness of the X potential (-1/r) as a constraint. Inclusion of derivative discontinuity and approximate integer self-interaction correction treatments along with first-principles determination of the effective second-order gradient expansion coefficient yields a major advance over our earlier correct asymptotic potential functional [“CAP”; J. Chem. Phys. 142, 054105 (2015)]. The new functional reduces a spurious bump in the CAP atomic exchange potential and moves it to distances irrelevantly far from the nucleus (outside the tail of essentially all practical basis functions). It therefore has nearly correct atomic exchange-potential behavior out to rather large finite distances r from the nucleus but eventually goes as ? c / r with an estimated value for the constant c of around 0.3, so as to achieve other important properties of exact DFT exchange within the restrictions of the GGA form. We illustrate the results with the Ne atom optimized effective potentials and with standard molecular benchmark test data sets for thermochemical, structural and response properties.
关键词： hyperpolarizabilities,excitation energies,Density functional theory,exchange potential asymptotic behavior,polarizabilities,exchange-correlation functional
更新于2025-09-23 15:21:21
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A general approach to evaluate the ensemble cross-correlation response for PIV using Kernel density estimation
摘要： Cross-correlation in particle image velocimetry is well known to behave as a non-linear operator, depending heavily on the distribution of tracer images and image quality. While analytical descriptors of the correlation response have so far been dealt with for simplistic flow cases, in this work a methodology is presented based on Kernel density estimation to retrieve the inherent correlation response to any deterministic flow field. The new approach bypasses the need for Monte-Carlo simulations and its inherent sensitivity to parameter settings make it a more efficient alternative to analyse filtering of the underlying velocity field due to image cross-correlation. The derivation of the underlying equations is presented and a numerical assessment corroborates the suitability of the approach to mimic ensemble correlation.
关键词： Ensemble correlation,Particle image velocimetry,Flow field filtering,Kernel density estimation,Cross-correlation
更新于2025-09-23 15:21:01
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Measurement of Weld Zone Properties of Laser-Welded Tailor-Welded Blanks and Its Application to Deep Drawing
摘要： Weld zones in tailor welded blanks have different mechanical properties than the base metals and thus have significant effects on formability. In this work, flow stresses of weld zones in laser-welded dissimilar dual-phase steels were measured. Strains at the weld zones of notched specimens were measured using the digital image correlation method and the flow stress data were corrected considering the anisotropy. For validation, finite element simulations were performed for the cup drawing process by considering the measured weld zone properties, and the weld line movements were compared with the measurements.
关键词： Laser welding,Formability,Digital image correlation,Dual-phase steel,Flow stress
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE Sustainable Power and Energy Conference (iSPEC) - Beijing, China (2019.11.21-2019.11.23)] 2019 IEEE Sustainable Power and Energy Conference (iSPEC) - Analysis on photovoltaic penetration in gridding distribution network considering the timing correlation between source and load
摘要： The increased photovoltaic penetration has brought severe problems to the power grid. The penetration capacity of solar power should be calculated accurately so as to arrange the construction of power grid in a reasonable way. An improved clustering method considering the timing correlation between source and load is proposed to distinguish typical photovoltaic output scenes in this paper. A risk rating method based on SA-PSO algorithm is also designed to evaluate the risk level for the photovoltaic penetration of the whole region. Results from an actual gridding distribution network demonstrate the accuracy of the method.
关键词： slope distance,gridding operation,SA-PSO algorithm,photovoltaic penetration,timing correlation
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Revision of GUM: the suggested alhorythm for processing measurment results
摘要： The main requirements for the revised GUM are considered. The proposed algorithm for processing measurement results is given. Criteria for compliance with the listed requirements are described. Methods for processing the measurement results with a nonlinear model are proposed.
关键词： estimate and standard uncertainty of the measurand,estimates and standard uncertainties of input quantities,correlation,expanded uncertainty,GUM revision
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Evaluation of ultrasound reflection coefficient measurement result and its uncertainty by the method of linearization
摘要： It is shown that, if the ultrasound amplitudes before (A0) and after(A) application of the test liquid (soybean oil) to the working surface of the acoustic cell are measured using only one (working) channel of the installation, the measurement results become mutually correlated. And if A0 is measured on the reference installation channel and the amplitude A is measured on the working channel of the installation, the measurement results are not mutually correlated. And thus, it becomes possible to use the method of linearization to evaluate the measurement result and its accuracy characteristics (error and / or uncertainty).
关键词： error,uncertainty,ultrasound,acoustic cell,method of linearization,reference,liquid,measurement,working,correlation,reflection coefficient,soybean oil
更新于2025-09-23 15:21:01