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- 摘要
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Enhancing defects characterization in pulsed thermography by noise reduction
摘要： In the field of NDT techniques for aeronautic components of composite materials, the development of automatic and robust approaches for defect detection is largely desirable for both safety and economic reasons. This paper introduces a novel methodology for the automatic analysis of thermal signals resulting from the application of pulsed thermography. Input thermal decays are processed by a proper FIR filter designed to reduce the measurement noise, and then modeled to represent both sound regions and defective ones. Output signals are thus fitted on an exponential model, which approximates thermal contrasts with three robust parameters. These features feed a decision forest, trained to detect discontinuities and characterize their depths. Several experiments on actual sample laminates have proven the increase of the classification performance of the proposed approach with respect to related ones in terms of the reduction of missing predictions of defective classes.
关键词： FIR filter,Decision forest,Pulsed thermography,Model approximation
更新于2025-09-23 15:23:52
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Femtosecond Electron Dynamics in Graphene Nanoribbons - A Nonequilibrium Green Functions Approach Within an Extended Hubbard Model
摘要： A new approach to study the correlated femtosecond electron dynamics in finite graphene clusters, such as nanoribbons, is presented here. The systems are described by an extended Hubbard model that takes into account the overlap of adjacent orbitals and hopping between up to third-nearest neighbors. The model is solved by the nonequilibrium Green functions approach combined with different self-energy approximations, including the second-Born and GW self-energy, to take into account electronic correlations. The description allows us to predict the correlated nonequilibrium dynamics of excited graphene nanostructures of arbitrary geometry containing up to 100 carbon atoms for up to 25 fs.
关键词： correlated dynamics,nonequilibrium Green functions,Hubbard model,graphene nanoribbons
更新于2025-09-23 15:23:52
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An image thresholding approach based on Gaussian mixture model
摘要： Image thresholding is an important technique for partitioning the image into foreground and background in image processing and analysis. It is difficult for traditional thresholding methods to get satisfactory performance on the noisy and uneven grayscale images. In this paper, we propose an image thresholding approach based on Gaussian mixture model (GMM) to solve this problem. GMM assumes that image is a mixture of two unknown parameters’ Gaussian distributions, which corresponds to foreground and background, respectively. Based on this assumption, we adopt expectation maximization algorithm with a simple initialization strategy to estimate the statistical parameters and utilize Bayesian criteria to generate the binary map. Furthermore, we calculate the posterior probabilities in consideration of neighborhood effect to achieve good performance on noisy and uneven grayscale images. Experimental results conducted on the synthetic and real images demonstrate the effectiveness of the proposed method.
关键词： Image thresholding,Gaussian mixture model,EM algorithm,Neighborhood information
更新于2025-09-23 15:23:52
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Anisotropic Circular Dichroism of Light-Harvesting Complex II in Oriented Lipid Bilayers: Theory Meets Experiment
摘要： Anisotropic circular dichroism (ACD) spectroscopy of macroscopically aligned molecules reveals additional information about their excited states that is lost in the CD of randomly-oriented solutions. ACD spectra of light-harvesting complex II (LHCII)—the main peripheral antenna of photosystem II in plants—in oriented lipid bilayers, were recorded from the far-UV to the visible wavelength region. The ACD spectra show a drastically enhanced magnitude and level of detail compared to the isotropic CD spectra, resolving a greater number of bands and weak optical transitions. Exciton calculations show that the spectral features in the chlorophyll Qy region are well reproduced by an existing Hamiltonian for LHCII, providing further evidence for the identity of energy sinks at chlorophylls a603 and a610 in the stromal layer and chlorophylls a604 and a613 in the luminal layer. We propose ACD spectroscopy to be a valuable tool linking the three-dimensional structure and the photophysical properties of pigment–protein complexes.
关键词： optical spectroscopy,photosynthetic complexes,model membranes,oriented CD,excitonic CD,exciton theory
更新于2025-09-23 15:23:52
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DeepSpectra: An end-to-end deep learning approach for quantitative spectral analysis
摘要： Learning patterns from spectra is critical for the development of chemometric analysis of spectroscopic data. Conventional two-stage calibration approaches consist of data preprocessing and modeling analysis. Misuse of preprocessing may introduce artifacts or remove useful patterns and result in worse model performance. An end-to-end deep learning approach incorporated Inception module, named DeepSpectra, is presented to learn patterns from raw data to improve the model performance. DeepSpectra model is compared to three CNN models on the raw data, and 16 preprocessing approaches are included to evaluate the preprocessing impact by testing four open accessed visible and near infrared spectroscopic datasets (corn, tablets, wheat, and soil). DeepSpectra model outperforms the other three convolutional neural network models on four datasets and obtains better results on raw data than in preprocessed data for most scenarios. The model is compared with linear partial least square (PLS) and nonlinear artificial neural network (ANN) methods and support vector machine (SVR) on raw and preprocessed data. The results show that DeepSpectra approach provides improved results than conventional linear and nonlinear calibration approaches in most scenarios. The increased training samples can improve the model repeatability and accuracy.
关键词： model accuracy,Inception,convolutional neural network,chemometrics,repeatability
更新于2025-09-23 15:23:52
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A dynamic model based on response factor method and seasonal performance analysis for integration of flat plate solar collector with building envelope
摘要： Integrating solar thermal collectors into building envelopes (e.g. walls or roofs) is very promising due to no need of additional site to place solar collectors. When a solar collector is integrated with a building, the working conditions for both the solar collector and the building envelope are changed. This paper proposed a new dynamic thermal model based on the response factor method. The new model combines the conventional analysis method for solar collectors with building envelopes, therefore it is easy to be understood and is more convenient to be realized by programming in a computer than state space model. The calculated results by the dynamic model agreed well with those calculated by the state space model and the measured experimental data, suggesting a satisfying validity of the model proposed. The seasonal performance of a solar wall (integrating of solar collectors and walls) in Beijing was studied by the new model. The results showed that: (1) In winter, the useful heat gain by the solar wall was always a little higher than the separate wall by about 6.7–8.8%, and the heat loss through solar wall is reduced by 90% or more, this is very favorable to reduce space heating load. (2) In summer, the useful heat gain of solar wall was higher than the separate collector by about 2.1–10.2%, the heat transferred through walls was less or higher than the separate wall depending on the inlet water temperature.
关键词： Dynamic model,Building heat transfer,Response factor method,Integration of solar collector with building,Useful heat gains
更新于2025-09-23 15:23:52
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Closed-loop functional optogenetic stimulation
摘要： Optogenetics has been used to orchestrate temporal- and tissue-specific control of neural tissues and offers a wealth of unique advantages for neuromuscular control. Here, we establish a closed-loop functional optogenetic stimulation (CL-FOS) system to control ankle joint position in murine models. Using the measurement of either joint angle or fascicle length as a feedback signal, we compare the controllability of CL-FOS to closed-loop functional electrical stimulation (CL-FES) and demonstrate significantly greater accuracy, lower rise times and lower overshoot percentages. We demonstrate orderly recruitment of motor units and reduced fatigue when performing cyclical movements with CL-FOS compared with CL-FES. We develop and investigate a 3-phase, photo-kinetic model to elucidate the underlying mechanisms for temporal variations in optogenetically activated neuromusculature during closed-loop control experiments. Methods and insights from this study lay the groundwork for the development of closed-loop optogenetic neuromuscular stimulation therapies and devices for peripheral limb control.
关键词： Functional stimulation,Photo-kinetic model,Motor units,Optogenetics,Neuromuscular control,Fatigue,Closed-loop control
更新于2025-09-23 15:23:52
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Comparison of UV-AOPs (UV/H2O2, UV/PDS and UV/Chlorine) for TOrC removal from municipal wastewater effluent and optical surrogate model evaluation
摘要： UV-based advanced oxidation processes (AOPs) have been widely explored to remove organic contaminants from water streams. In this lab-scale study, the removal of 17 trace organic chemicals (TOrCs) by UV/H2O2, UV/PDS and UV/Chlorine was investigated at equimolar radical promoter concentrations in municipal wastewater. Direct comparison of the UV-AOPs was conducted with eight TOrCs being resistant to direct oxidation by H2O2, PDS and chlorine and revealed a general oxidation performance following the order of UV/Chlorine > UV/H2O2 ≈ UV/PDS while UV/PDS and UV/Chlorine exhibited higher compound selectivity than UV/H2O2. However, although oxidation performance of UV/Chlorine is outstanding in comparison of the three UV-AOPs, it has to be noted that oxidation byproduct (OBP) formation potential might be substantially higher during both UV/PDS and UV/Chlorine compared to UV/H2O2 which was not investigated in this study. Evaluating potential optical surrogates to predict trace organic chemical (TOrCs) removal in UV-AOPs, nine parameters were selected representing chromophore and fluorophore features of DOM including components derived by parallel factor analysis (PARAFAC) of excitation-emission matrices. UV absorbance (UVA), total fluorescence (TF) and the selected fluorescence peak P_IV revealed highest linear correlation coefficients and were therefore identified as surrogates representing underlying mechanistic reactions of each UV-AOP. As none of the surrogates directly reacted with UV irradiation, slopes of surrogate-indicator correlations for photo-susceptible TOrCs decreased towards higher oxidant dosages. Correlations for these compounds should therefore only be determined for a limited range of oxidant dosage.
关键词： UV/HOCl,surrogate model.,UV/H2O2,wastewater,UV/PDS,trace organic chemicals
更新于2025-09-23 15:23:52
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Reduced order derivation of the two-dimensional band structure of a mixed-mode resonator array
摘要： In this paper, the 2D band structure of a mixed-mode metamaterial resonator array for in-plane waves is investigated. The band structure in the interior and on the boundary of the irreducible Brillouin zone and 1D dispersion diagrams for different propagation angles are calculated numerically and presented. Additionally, a reduced order analytical method is established to compare and approximate the band structure. The studied metamaterial, with a T-shaped cantilever beam as the resonator in its square array repeating unit cells, exhibits branches with mixed P and SV waves except at exactly one angle of propagation. This paper also reports on the occurrence of avoided level crossings, which are related to the existence of exceptional points in the complex domain. A reduced order analytical approach is used that can generate partial (low branches) band structure with relatively little computational effort. The reduced order model agrees well with the numerical results for these low branches and can provide support in mode identification and band sorting. With proper adjustments in parameters, this analytical method will be applicable to other metamaterials that have a similar unit cell structure.
关键词： band structure,reduced order model,resonator array,metamaterial,avoided level crossings,mixed-mode waves
更新于2025-09-23 15:23:52
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Rapid mapping application of vegetated terraces based on high resolution airborne LiDAR
摘要： The aim of this work is to define a methodology for terraced areas survey and rapid mapping in a complex environment, like Ligurian (Northwestern Italy) one, where a remarkable percentage of its surface is estimated as terraced and where the canopy coverage makes their recognition very hard. Methodology steps are the definition of LiDAR survey parameters, morphometric filtering and GIS processing for final mapping. Each phase is oriented to provide a reliable terrace mapping, also practicable in canopy-covered areas due to a particular attention to land cover influence. The work considers a case study (Rupinaro basin) close to Cinque Terre, with a mixed land cover (terraces, forest and urbanized areas). The methodology provided encouraging results detecting 448 ha of terraces, 95% of them located under canopy cover. This finding pointed out that terraces mapping cannot rely only on photo-interpretation, as canopies will hamper their detection. Mapping of these areas, frequently characterized by abandonment, is crucial while identifying potential trigger factors for slope instabilities. This case study highlighted the importance of a carefully planned production chain, that should start from LiDAR survey parameter choice, providing the best input for analysis algorithm and providing the correct identification of terraces.
关键词： land abandonment,high resolution Digital Terrain Model,rapid mapping,Anthropic landscape,morphometric filtering
更新于2025-09-23 15:23:52