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Development of two new semi-empirical formulas for estimation of solar absorptance in circular cavity receivers
摘要： In this paper two new semi-empirical formulas for calculating the equivalent absorptance of solar irradiation at the inner surface of cylindrical cavities is proposed. The multiple re?ections that occur at the interior of the cavity were ?rst analyzed considering a two-dimensional geometrical approach and thus the ?rst analytical relationship for the equivalent solar absorptance was revealed. In addition, a three-dimensional ray tracing analysis was conducted through Solidworks Flow Simulation. Several di?erent cavity aperture’s widths as well as solar absorptance coe?cients (α = 0.5–0.9 per 0.1) were examined in both analyses and it was found that the two dimensional analytical approach exceeds the simulation by 1.50–6.83% on average going from the highest to the lowest solar absorptance value. Finally, two new correlations were developed for correcting the analytical approach according to the 3D ray tracing with the optimum between them to provide a mean error at the equivalent solar absorptance calculation of about 0.78%, 0.55%, 0.40%, 0.21% and 0.18% for the ?ve di?erent absorptance coe?cients were examined.
关键词： Solidworks Flow Simulation,Solar absorptance,Cavity receiver,Optical analysis,New correlation
更新于2025-09-19 17:15:36
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Electron correlation effects in the photoionization of CO and isoelectronic diatomic molecules
摘要： This paper investigates the first sigma satellite band, which is by far the most prominent, in the valence photoelectron spectra for a set of isoelectronic diatomic molecules: carbon monoxide, carbon monosulfide, carbon monoselenide, silicon monoxide and boron monofluoride. In particular, we analyze the effect of the electronic structure, with the change of the atomic pair along the row and column of the periodic table on the position of the satellite peak as well as on the related dynamical observables profiles. For this investigation, highly correlated calculations have been performed on the primary ionic states and the satellite band for all the molecules considered. Cross sections for the primary ionic states, calculated using Dyson orbitals, have been compared with those obtained with Hartree–Fock and Density Functional Theory to probe the impact of the correlation in the bound states on the photoionization observables. Limitations of a simple intensity borrowing mechanism clearly result from the analysis of the satellite state, characterized by different features with respect to the relevant primary states.
关键词： isoelectronic molecules,photoelectron spectra,photoionization,electron correlation,Dyson orbitals
更新于2025-09-19 17:15:36
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Theory of two atoms in a chiral waveguide
摘要： A theory is presented that describes the atom and field dynamics for two atoms in a chiral waveguide. A source-field approach is used that enables one to identify the various physical processes contributing to these dynamics. Each atom is prepared in an arbitrary state at t = 0 and the field intensity and correlation functions are calculated, fully accounting for retardation. When the atoms are prepared in identical superposition states, the effects of constructive and destructive interference play a significant role on both the field intensity and second-order correlation function. It is also shown that the results can be taken over to provide a solution for the related problem of a single-photon pulse incident on an atom prepared in an arbitrary initial state.
关键词： chiral waveguide,second-order correlation function,source-field approach,atom-field dynamics,interference,retardation
更新于2025-09-19 17:13:59
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Development of a non-contact and non-destructive laser speckle imaging system for remote sensing of anisotropic deformation around fastener holes
摘要： Strain sensing around the fastener holes is fundamentally significant in structural health monitoring and failure detections. Conventional non-destructive testing (NDT) techniques typically have limitations in performing reliable and efficient inspections. Here, a laser speckle imaging system (LSIS) has been developed to achieve non-contact, non-destructive and remote strain sensing. Methods for determining optimal laser speckle patterns have been investigated to achieve remote sensing of strain up to a working distance of 5 m. This LSIS was applied to study the anisotropic properties of un-notched and circular notched specimens in cold-rolled aluminium sheet, an important material for the construction of lightweight aircraft structures. The results showed that strain distributions determined by LSIS are consistent with finite element (FE) predictions in which the evolution of strain concentrations not only depends on the notch size but also on material anisotropy. This study demonstrates the potential application of LSIS as an effective NDT technique for full-field, non-contact and remote sensing of anisotropic deformation around fastener holes.
关键词： Non-destructive testing,Digital image correlation,Laser speckle imaging,Remote strain sensing
更新于2025-09-19 17:13:59
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[Institution of Engineering and Technology 7th Brunei International Conference on Engineering and Technology 2018 (BICET 2018) - Bandar Seri Begawan, Brunei (12-14 Nov. 2018)] 7th Brunei International Conference on Engineering and Technology 2018 (BICET 2018) - Impact of RF and leds on plants growth
摘要： In this paper, we present a concept for a compact ultra-wideband multielement antenna (MEA) for massive MIMO indoor base stations. The antenna concept is based on the simultaneous excitation of different characteristic modes on each element of the MEA. This enables an effective 484 port antenna using only 121 physical antenna elements. Thereby, a size reduction of 54% compared to a generic MEA based on crossed dipoles is achieved. The antenna operates in the ultra-wide frequency band of 6–8.5 GHz with a re?ection coef?cient of sii < ?10 dB and the interelement and intraelement mutual coupling of the antenna ports is sji ≤ ?20 dB.
关键词： multielement antenna (MEA),massive multiple-input multiple-output (MIMO),correlation,Characteristic modes
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Compact Single-Shot D-Scan Setup for the Characterization of Few-Cycle Laser Pulses
摘要： The power generator is typically maintained with a time- or usage-based strategy, which could result in a substantial waste of remaining useful life, high maintenance cost, and low plant availability. Recently, the field of prognostics and health management offers diagnostic and prognostic techniques to precisely assess the health condition and robustly predict the remaining useful life (RUL) of an engineered system, with an aim to address the aforementioned deficiencies. This paper explores a smart health reasoning system to assess the health condition of power generator stator bars against moisture absorption based on the statistical analysis of the capacitance measurements on bar insulators. In particular, a relative health measure, namely the directional Mahalanobis distance, is proposed to quantify the health condition of a stator bar. The smart health reasoning system is validated using five years’ field data from seven generators, each of which contains 42 turns.
关键词： health diagnostics,statistical correlation,moisture absorption,Directional Mahalanobis distance (DMD),power generator stator bar
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Two-Color Mid-Infrared Laser Filaments Produce Terahertz Pulses with Extreme Efficiency
摘要： A novel quantization watermarking method is presented in this paper, which is developed following the established feature modulation watermarking model. In this method, a feature signal is obtained by computing the normalized correlation (NC) between the host signal and a random signal. Information modulation is carried out on the generated NC by selecting a codeword from the codebook associated with the embedded information. In a simple case, the structured codebooks are designed using uniform quantizers for modulation. The watermarked signal is produced to provide the modulated NC in the sense of minimizing the embedding distortion. The performance of the NC-based quantization modulation (NCQM) is analytically investigated, in terms of the embedding distortion and the decoding error probability in the presence of valumetric scaling and additive noise attacks. Numerical simulations on artificial signals confirm the validity of our analyses and exhibit the performance advantage of NCQM over other modulation techniques. The proposed method is also simulated on real images by using the wavelet-based implementations, where the host signal is constructed by the detail coefficients of wavelet decomposition at the third level and transformed into the NC feature signal for the information modulation. Experimental results show that the proposed NCQM not only achieves the improved watermark imperceptibility and a higher embedding capacity in high-noise regimes, but also is more robust to a wide range of attacks, e.g., valumetric scaling, Gaussian filtering, additive noise, Gamma correction, and Gray-level transformations, as compared with the state-of-the-art watermarking methods.
关键词： Decoding error probability,valumetric scaling,normalized correlation,spread transform,quantization watermarking
更新于2025-09-19 17:13:59
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[IEEE 2019 Days on Diffraction (DD) - St. Petersburg, Russia (2019.6.3-2019.6.7)] 2019 Days on Diffraction (DD) - Normal mode coupling in a waveguide with a range-dependent sound speed profile in the bottom
摘要： In this paper, a novel graphene-based multiple-input multiple-output (MIMO) concept is proposed for high-rate nanoscale wireless communications between transceivers, which are nano/micrometers apart from each other. In particular, the proposed MIMO architecture considers exploiting a deep-subwavelength propagation channel made of graphene. This allows us to increase the number of transmitted symbol streams, while using a deep-subwavelength arrangement of individual plasmonic nanotransmit/receive elements in which the spacing between the transmitters and/or the receivers is tens of times smaller than the wavelength. This exclusive benefit is achieved with the aid of the phenomenon of graphene plasmons, where graphene offers the extremely confined and low-loss plasmon propagation. Hence, the proposed graphene-based MIMO system is capable of combating the fundamental limitations imposed on the classic MIMO configuration. We also present a novel graphene-specific channel adaptation technique, where the chemical potential of the graphene channel is varied to improve the power of the received signals.
关键词： MIMO,surface plasmon polariton,nanoscale communication,chemical potential,graphene,Correlation,diffraction limit,deep subwavelength
更新于2025-09-19 17:13:59
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Ratiometric Detection of Rifampin by Using Selfa??Assembled Nanocomposites with Dual Fluorescence Emissions and Analysis of Twoa??Dimensional Correlation Spectroscopy
摘要： A new ratiometric ?uorescence probe is constructed for the detection of rifampin (RIF). Amino-modi?ed silicon nanoparticles (SiNPs) and mercaptoundecanoic acid capped gold nanoclusters (MUA-AuNCs) are self-assembled into nanocomposites, showing dual ?uorescence emissions, respectively, at 440 and 615 nm under a single excitation of 300 nm. The morphology, surface chemistry and optical properties of the nanocomposites are ?nely investigated through transmission electron microscopy (TEM), Fourier transforms infrared spectroscopy (FT-IR), UV–vis absorbance, dynamic and steady state ?uorescence spectroscopy. Owning to rich hydroxyl groups, RIF can bind with MUA-AuNCs though hydrogen bonds resulting in the red ?uorescence quenching. But the SiNPs keep their own blue ?uorescence stable, which can act as an internal reference for ratiometric detection. By means of the ratio I615/I440, the linear relationship is established in the range from 0.1 to 5 μM with the detection limit of 0.04 μM. In addition, the synchronous and asynchronous ?uorescence 2D correlation maps have been created to in-depth study the relative detecting mechanism.
关键词： Rifampin,Self-assembly,Ratiometric ?uorescence probe,2D correlation spectroscopy
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - An Insight into Pure Ge Based Kesterite Synthesis
摘要： The distributed Brillouin analysis of an 8.8-km-long ?ber with a spatial resolution of 2 cm is presented. All 440 000 potential resolution points are addressed in the measurement. A 7-cm-long hot-spot, located toward the output end of the pump wave, is properly identi?ed in the experiment. The experimental error in the estimate of the local values of the Brillouin frequency shift is ±3.5 MHz. The analysis is based on the simultaneous generation and analysis of Brillouin interaction in more than 2000 correlation peaks, induced by periodic phase modulation of the pump and signal waves. The Brillouin ampli?cations at individual peaks are resolved using radar-like coding of pump wave magnitude by a 10000 bit-long aperiodic sequence, and postdetection compression at the receiver end. Extensive numerical simulations of the Brillouin interactions over kilometers of ?ber with centimeter resolution are reported as well. The results are at the state of the art for high-resolution distributed Brillouin sensors.
关键词： sequence compression,All-optical signal processing,stimulated Brillouin scattering,?ber-optic sensors,distributed ?ber sensors,correlation-domain analysis
更新于2025-09-19 17:13:59