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FibAR: Embedding Optical Fibers in 3D Printed Objects for Active Markers in Dynamic Projection Mapping
摘要： We experimentally investigate mutual information and generalized mutual information for coherent optical transmission systems. The impact of the assumed channel distribution on the achievable rate is investigated for distributions in up to four dimensions. Single channel and wavelength-division multiplexing (WDM) transmission over transmission links with and without inline dispersion compensation are studied. We show that for conventional WDM systems without inline dispersion compensation, a circularly symmetric complex Gaussian distribution is a good approximation of the channel. For other channels, such as with inline dispersion compensation, this is no longer true and gains in the achievable information rate are obtained by considering more sophisticated four-dimensional (4D) distributions. We also show that for nonlinear channels, gains in the achievable information rate can also be achieved by estimating the mean values of the received constellation in four dimensions. The highest gain for such channels is seen for a 4D correlated Gaussian distribution.
关键词： mutual Information,digital communication,fiber nonlinear optics,optical fiber communication,Channel models
更新于2025-09-23 15:19:57
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Recent Problems of Heat-Transfer Simulation in Technological Processes of Selective Laser Melting and Fusion
摘要： The thermal processes arising upon the implementation of the additive technologies of selective laser melting and the fusion of metals and alloys are analyzed. An adequate description of the heat transfer upon the implementation of additive technological processes associated with high-intensity local heating by a moving laser beam and the phase transitions generated by a semifinished powder product, crystallization, and the concomitant effects in the growing element is the key to gaining insight into the microstructure and the efficient properties of the obtained material and the prevention of residual deformation (shrinkage) of the item. Currently, the main causes of unpredictable production defects are deviations of the shape of the final item from the preset geometry and high-amplitude residual stresses, which can initiate destruction of the item under loads significantly lower than those calculated, as well as the occurrence of the microscopic defects (pores, layer interfaces, etc.) are. The development of mathematical models that, on the one hand, are sufficiently accurate to predict the listed phenomena and, on the other hand, allow practical implementation in engineering calculations is the basis for the further development of the laser-melting and fusion of metal materials. At the same time, analysis of the current state of the problem shows that development of efficient numerical methods providing acceptable computational costs while maintaining accuracy is the key element in the practical implementation of the models. A method based on multiscale, interconnected modeling of the mechanical and the thermal state of the growing body—at the local level in the melt pool domain, at the intermediate level in the vicinity of the melt pool and the adjacent layers, and at the level of the entire product as a whole—seems to be efficient; here, the computing process at the global level can be based on a combination of the finite-element method (indisputable in practice) and analytical calculations providing local refinement of the solution.
关键词： numerical methods,heat-transfer simulation,microstructure,residual deformation,mathematical models,fusion,thermal processes,selective laser melting,additive technologies
更新于2025-09-23 15:19:57
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Efficient predictive models for characterization of photovoltaic module performance
摘要： This paper presents simple, e?cient and general mathematical models for predicting the I-V characteristics of any Photovoltaic (PV) module at any irradiance and temperature values without any need to estimate the parameters of the PV circuit model. The prediction of the I-V characteristics in this paper is mainly dependent on building general mathematical models for ten key points selected from the I-V characteristics. To generalize these models and make them applicable for any PV module, twenty di?erent PV modules covering a wide range of PV modules with di?erent temperature and irradiance values are selected for training data generation. All simulations are performed in MATLAB/SIMULINK. The training process and models development are built using EUREQA software. The performance of the developed models is tested by comparison with simulation data, experimental data, and di?erent recent research articles. The assessments have shown e?cient prediction capability of all models to predict the I-V curves for any PV module, at any weather condition, without evaluating the PV circuit model parameters. The models have also exceeded various algorithms used in the literature in terms of accuracy of I-V characteristics estimation with less execution time.
关键词： MPP,I-V curve,Mathematical models,PV,EUREQA
更新于2025-09-23 15:19:57
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Laser-induced breakdown spectroscopy (LIBS) spectra interpretation and characterization using parallel factor analysis (PARAFAC): a new procedure for data and spectral interference processing fostering the waste electrical and electronic equipment (WEEE) recycling process
摘要： Laser-induced breakdown spectroscopy (LIBS) was used to characterize base (Al and Cu) and noble (Au and Ag) elements on a printed circuit board (PCB) from hard disk (HD). A PCB was cut in 77 fragments and, a matrix of 4 rows and 4 columns with 10 laser pulses in each point of the matrix was acquired in each fragment by LIBS. For each element, a spectral range was selected with its respective emission lines and, Parallel Factor Analysis (PARAFAC) was used to model the data. LIBS spectra are two-way data, but in this case, the depths were used as a third mode being the data set: samples × variables (emission lines) × depths (laser pulses from 1 to 10). PARAFAC was able to model spectral interference and analyte emission line in separate components, which allows to remove the contribution of the concomitants from the measured data. The scores (relative concentrations, mode 1) of the component of interest was used to create a map of the PCB colored by concentration, and it was possible visualize where the element is predominantly located on the PCB. In addition, classification models were performed for Au and Ag using Partial least squares discriminant analysis (PLSDA) after removal of the interferents using the PARAFAC result. Good figures of merit were obtained for calibration, cross-validation and validation data set with accuracy ranging from 0.94 to 0.98. Therefore, the use of PARAFAC and LIBS spectra were very useful, being a great contribution to LIBS community and for urban mining.
关键词： multi-way analysis,printed circuit board,Urban mining,noble elements,classification models
更新于2025-09-23 15:19:57
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Heating up holography for single-trace JT?ˉ$$ J\overline{T} $$ deformations
摘要： We study thermodynamic aspects of a tractable toy model of holography for extremal Kerr black holes proposed in [1]. On the gravity side, the theory can be described by the worldsheet action of string theory on a warped AdS3 background supported by NS-NS flux. Once we turn on temperature, the deformed background is described by a black string solution of type IIB supergravity that features a locally warped AdS3 factor. The dual field theory is conjectured to be a single-trace version of a J T -deformed CFT at finite temperature. As evidence for the correspondence we show that the spectrum of strings winding on the deformed background agrees with the spectrum of J T -deformed CFTs. Furthermore, we show that the gravitational charges of the black string match the averaged charges of a thermal ensemble in the dual field theory. Finally, we reproduce the Bekenstein-Hawking entropy of the black string from the microscopic density of states of J T -deformed CFTs.
关键词： Conformal Field Models in String Theory,Integrable Field Theories,AdS-CFT Correspondence
更新于2025-09-23 15:19:57
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Effects of variation in background mixing ratios of N<sub>2</sub>, O<sub>2</sub>, and Ar on the measurement of <i>δ</i><sup>18</sup>O–H<sub>2</sub>O and <i>δ</i><sup>2</sup>H–H<sub>2</sub>O values by cavity ring-down spectroscopy
摘要： Cavity ring-down spectrometers have generally been designed to operate under conditions in which the background gas has a constant composition. However, there are a number of observational and experimental situations of interest in which the background gas has a variable composition. In this study, we examine the effect of background gas composition on a cavity ring-down spectrometer that measures δ18O–H2O and δ2H–H2O values based on the amplitude of water isotopologue absorption features around 7184 cm?1 (L2120-i, Picarro, Inc.). For background mixtures balanced with N2, the apparent δ18O values deviate from true values by ?0.50 ± 0.001 ‰ O2 %?1 and ?0.57 ± 0.001 ‰ Ar %?1, and apparent δ2H values deviate from true values by 0.26 ± 0.004 ‰ O2 %?1 and 0.42 ± 0.004 ‰ Ar %?1. The artifacts are the result of broadening, narrowing, and shifting of both the target absorption lines and strong neighboring lines. While the background-induced isotopic artifacts can largely be corrected with simple empirical or semi-mechanistic models, neither type of model is capable of completely correcting the isotopic artifacts to within the inherent instrument precision. The development of strategies for dynamically detecting and accommodating background variation in N2, O2, and/or Ar would facilitate the application of cavity ring-down spectrometers to a new class of observations and experiments.
关键词： background gas composition,correction models,Cavity ring-down spectroscopy,water isotopologues,isotopic artifacts
更新于2025-09-23 15:19:57
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Detection of collapsed buildings due to the 2016 Kumamoto, Japan, earthquake from Lidar data
摘要： The 2016 Kumamoto earthquake sequence was triggered by an Mw 6.2 event at 21:26 on April 14. Approximately 28 hours later, at 1:25 on April 16, an Mw 7.0 event (the mainshock) followed. The epicenters of both events were located near the residential area of Mashiki town and the region nearby. Due to very strong seismic ground motion, the earthquake produced extensive damage to buildings and infrastructure. In this paper, collapsed buildings were detected using a pair of digital surface models (DSMs), taken before and after the April 16 mainshock by airborne light detection and ranging (Lidar) flights. Different methods for extracting the collapsed buildings from the data were evaluated, and the change of average elevations within a building footprint was found to be the most important feature. Finally, the distribution of collapsed buildings in the study area was presented, and the result was consistent with that of a building damage survey performed after the earthquake.
关键词： 2016 Kumamoto earthquake,Lidar,digital surface models,collapsed buildings,damage detection
更新于2025-09-23 15:19:57
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[Springer Series on Atomic, Optical, and Plasma Physics] Gaseous Ion Mobility, Diffusion, and Reaction Volume 105 || Ab Initio Calculations of Transport Coefficients
摘要： There are two main philosophies behind theoretical calculations. The one illustrated in Chap. 9 is to use models of physical phenomenon, specifically mathematical models, that can be solved exactly, either analytically or by numerical methods. Such models often involve adjustable parameters whose values are fit by comparing model results to experimental values; once the parameters are determined, the models are then used to make similar calculations for other situations, ones that were not part of the set used to determine the parameters. The philosophy illustrated in this chapter is to start from our best theories and, as necessary, make approximations to reduce the equations to forms that are practical to solve, again either analytically or numerically. The hope is that, with time, the approximations will improve such that the calculated values match experimental results without using adjustable parameters. In short, the first philosophy is to make exact calculations with approximate theories, while the second is to make approximate calculations with theories that one believes to be exact.
关键词： experimental results,approximations,mathematical models,adjustable parameters,theoretical calculations
更新于2025-09-23 15:19:57
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IPR 1.0: an efficient method for calculating solar radiation absorbed by individual plants in sparse heterogeneous woody plant communities
摘要： Climate change may alter the spatial distribution, composition, structure and functions of plant communities. Transitional zones between biomes, or ecotones, are particularly sensitive to climate change. Ecotones are usually heterogeneous with sparse trees. The dynamics of ecotones are mainly determined by the growth and competition of individual plants in the communities. Therefore it is necessary to calculate the solar radiation absorbed by individual plants in order to understand and predict their responses to climate change. In this study, we developed an individual plant radiation model, IPR (version 1.0), to calculate solar radiation absorbed by individual plants in sparse heterogeneous woody plant communities. The model is developed based on geometrical optical relationships assuming that crowns of woody plants are rectangular boxes with uniform leaf area density. The model calculates the fractions of sunlit and shaded leaf classes and the solar radiation absorbed by each class, including direct radiation from the sun, diffuse radiation from the sky, and scattered radiation from the plant community. The solar radiation received on the ground is also calculated. We tested the model by comparing with the results of random distribution of plants. The tests show that the model results are very close to the averages of the random distributions. This model is ef?cient in computation, and can be included in vegetation models to simulate long-term transient responses of plant communities to climate change. The code and a user’s manual are provided as Supplement of the paper.
关键词： climate change,individual plant radiation model,solar radiation,ecotones,vegetation models,IPR
更新于2025-09-23 15:19:57
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Geospatial Target Detection from High-Resolution Remote-Sensing Images Based on PIIFD Descriptor and Salient Regions
摘要： Geospatial target detection from visible remote-sensing images is considered as one of the most important issues in the analysis of aerial and satellite imagery. Development of remote-sensing techniques and enhancing resolution of images provide an opportunity to advance automatic analysis. The proposed methods of geospatial target detection have faced to a variety of challenges. Recently, local features are extensively used which play a very effective role in dealing with these issues. High intensity variations between targets and backgrounds in different images are the most critical challenges. Most proposed local feature descriptors are not able to deal with this amount of intensity variations and are accompanied with errors when facing them. In this paper, PIIFD descriptor has been applied to cope with intense intensity variations, as this descriptor is symmetrical against contrast. The proposed framework to automatically detect geospatial targets includes a supervised approach based on local features extraction and description and consists of three main steps including training, image searching, and geospatial target detection. In the training step, local features are extracted by UR-SIFT algorithm that properly matches with remote-sensing images and are described by the PIIFD descriptor. Due to the large dimensions of the extracted features, the SABOVW model has been used for quantization purpose. This model uses soft assignment of features to codebook, and the presentation provided by this model is used to train SVM classi?er. In the second step, for the sake of computational ef?ciency, the salient regions of the image are detected by combining the saliency models, which reduces the image space to search the geospatial targets. In the third step, the salient regions are scanned by the sliding window approach and a descriptor of each position is generated. Eventually, the process of detection of geospatial targets will be carried out by applying the trained SVM model to each window. In order to evaluate the ef?ciency of the PIIFD descriptor, its performance is compared with descriptors such as SIFT, DAISY, LSS, and LBP. The results showed better performance of the PIIFD descriptor in detection of geospatial targets.
关键词： Saliency models,Local features,Airplane targets,Detector,Descriptor,SABOVW model
更新于2025-09-19 17:15:36