- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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[IEEE 2018 China International SAR Symposium (CISS) - Shanghai (2018.10.10-2018.10.12)] 2018 China International SAR Symposium (CISS) - On the Ship Wake Simulation for Multi-Frequncy and Mutli-Polarization SAR Imaging
摘要： In this paper, computer simulation of SAR (Synthetic Aperture Radar) image of surface-ship wakes is studied. Furthermore, the simulation results of the ship wake are compared at different frequencies and polarizations. The model adopted in the simulation accounts for not only the Kelvin wake produced in the water by the moving ship, but also the influence of the sea surface. The radar back-scatter coefficients of the wake is calculated using the Bragg mechanism. Based on the combination of hydrodynamic and radar scatter calculations, the simulation can provide the backscattering coefficients of the ship wake. Simulation results show that, in general, the back-scattering coefficient of ship wake has little dependence on the radar frequency, however, significantly on the polarization.
关键词： simulation,sea surface model,ship wake,SAR,Radar scattering model,Ship wake model
更新于2025-09-23 15:22:29
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Potential Investigation of Linking PROSAIL with the Ross-Li BRDF Model for Vegetation Characterization
摘要： Methods that link different models for investigating the retrieval of canopy biophysical/structural variables have been substantially adopted in the remote sensing community. To retrieve global biophysical parameters from multiangle data, the kernel-driven bidirectional reflectance distribution function (BRDF) model has been widely applied to satellite multiangle observations to model (interpolate/extrapolate) the bidirectional reflectance factor (BRF) in an arbitrary direction of viewing and solar geometries. Such modeled BRFs, as an essential information source, are then input into an inversion procedure that is devised through a large number of simulation analyses from some widely used physical models that can generalize such an inversion relationship between the BRFs (or their simple algebraic composite) and the biophysical/structural parameter. Therefore, evaluation of such a link between physical models and kernel-driven models contributes to the development of such inversion procedures to accurately retrieve vegetation properties, particularly based on the operational global BRDF parameters derived from satellite multiangle observations (e.g., MODIS). In this study, the main objective is to investigate the potential for linking a popular physical model (PROSAIL) with the widely used kernel-driven Ross-Li models. To do this, the BRFs and albedo are generated by the physical PROSAIL in a forward model, and then the simulated BRFs are input into the kernel-driven BRDF model for retrieval of the BRFs and albedo in the same viewing and solar geometries. To further strengthen such an investigation, a variety of field-measured multiangle reflectances have also been used to investigate the potential for linking these two models. For simulated BRFs generated by the PROSAIL model at 659 and 865 nm, the two models are generally comparable to each other, and the resultant root mean square errors (RMSEs) are 0.0092 and 0.0355, respectively, although some discrepancy in the simulated BRFs can be found at large average leaf angle (ALA) values. Unsurprisingly, albedos generated by the method are quite consistent, and 99.98% and 97.99% of the simulated white sky albedo (WSA) has a divergence less than 0.02. For the field measurements, the kernel-driven model presents somewhat better model-observation congruence than the PROSAIL model. The results show that these models have an overall good consistency for both field-measured and model-simulated BRFs. Therefore, there is potential for linking these two models for looking into the retrieval of canopy biophysical/structural variables through a simulation method, particularly from the current archive of the global routine MODIS BRDF parameters that were produced by the kernel-driven BRDF model; however, erectophile vegetation must be further examined.
关键词： PROSAIL model,the kernel-driven Ross-Li model,BRDF,model linking,Anisotropy Flat Index (AFX),albedo
更新于2025-09-23 15:22:29
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Single-Scatter Model for Short-Range Ultraviolet Communication in a Narrow Beam Case
摘要： The single scattering model for short-range ultraviolet (UV) communication is often replaced by an approximate model due to its simplified calculation. However, there are certain errors associated with the existing approximate models. To reduce the errors, a spherical crown (SC) model in a narrow beam case is derived in this letter, where we assume that the differential volume is a thin layer of SC. Meanwhile, the applicable conditions and error range of SC model are provided. The calculation results indicate that the errors of existing approximate models range from ?1.4 dB to 6.0 dB while that of SC model range from ?0.2 dB to 0.4 dB for the considered transceiver geometries, which means that SC model has a higher accuracy than the existing approximate models. In addition, the bit-error rate performance of UV communication system under SC model is also presented. This work greatly improves the accuracy of single scattering approximate model and provides a new method to estimate the path loss of short-range UV communication.
关键词： SC model,UV communication,approximate model,Single scattering
更新于2025-09-23 15:22:29
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Hierarchical Bayesian Inverse Lighting of Portraits with a Virtual Light Stage
摘要： From a single RGB image of an unknown face, taken under unknown conditions, we estimate a physically plausible lighting model. First, the 3D geometry and texture of the face are estimated by fitting a 3D Morphable Model to the 2D input. With this estimated 3D model and a Virtual Light Stage (VLS), we generate a gallery of images of the face with all the same conditions, but different lighting. We consider non-lambertian reflectance and non-convex geometry to handle more realistic illumination effects in complex lighting conditions. Our hierarchical Bayesian approach automatically suppresses inconsistencies between the model and the input. It estimates the RGB values for the light sources of a VLS to reconstruct the input face with the estimated 3D face model. We discuss the relevance of the hierarchical approach to this minimally constrained inverse rendering problem and show how the hyperparameters can be controlled to improve the results of the algorithm for complex effects, such as cast shadows. Our algorithm is a contribution to single image face modeling and analysis, provides information about the imaging condition and facilitates realistic reconstruction of the input image, relighting, lighting transfer and lighting design.
关键词： 3D Morphable Model,Hyperparameters,Generative Model,Hierarchical Bayesian Optimization,Inverse Lighting,Virtual Light Stage,Single Face Image
更新于2025-09-23 15:22:29
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Unsupervised Segmentation of Spectral Images with a Spatialized Gaussian Mixture Model and Model Selection
摘要： In this article, we describe a novel unsupervised spectral image segmentation algorithm. This algorithm extends the classical Gaussian Mixture Model-based unsupervised classification technique by incorporating a spatial flavor into the model: the spectra are modelized by a mixture of K classes, each with a Gaussian distribution, whose mixing proportions depend on the position. Using a piecewise constant structure for those mixing proportions, we are able to construct a penalized maximum likelihood procedure that estimates the optimal partition as well as all the other parameters, including the number of classes. We provide a theoretical guarantee for this estimation, even when the generating model is not within the tested set, and describe an efficient implementation. Finally, we conduct some numerical experiments of unsupervised segmentation from a real dataset.
关键词： Spectral images,Gaussian Mixture Model,Model selection,Spatial information,Unsupervised segmentation
更新于2025-09-23 15:22:29
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[IEEE 2018 Dynamics of Systems, Mechanisms and Machines (Dynamics) - Omsk, Russia (2018.11.13-2018.11.15)] 2018 Dynamics of Systems, Mechanisms and Machines (Dynamics) - Automatic Nonlinear Modeling Technique for Gaas HEMT
摘要： A new technique for nonlinear transistor modeling is suggested. The technique includes an analytical extraction and a multistage optimization, providing fully automated modeling. An extraction algorithm for the parameters of an internal voltage-controlled current source Ids is shown. A fully automated workflow of small-signal model extraction is presented. An approach for obtaining parameters of nonlinear capacitances is described. A 0.15um GaAs pHEMT nonlinear model was built and verified with measured IV-curve, multi-bias S-parameters and power characteristics.
关键词： compact nonlinear model,microwave transistor,large-signal model,GaAs HEMT
更新于2025-09-23 15:22:29
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[IEEE 2018 16th International Conference on Frontiers in Handwriting Recognition (ICFHR) - Niagara Falls, NY, USA (2018.8.5-2018.8.8)] 2018 16th International Conference on Frontiers in Handwriting Recognition (ICFHR) - Separating Optical and Language Models Through Encoder-Decoder Strategy for Transferable Handwriting Recognition
摘要： Lack of data can be an issue when beginning a new study on historical handwritten documents. To deal with this, we propose a deep-learning based recognizer which separates the optical and the language models in order to train them separately using different resources. In this work, we present the optical encoder part of a multilingual transductive transfer learning applied to historical handwriting recognition. The optical encoder transforms the input word image into a non-latent space that depends only on the letter-n-grams: it enables it to be independent of the language. This transformation avoids embedding a language model and operating the transfer learning across languages using the same alphabet. The language decoder creates from a vector of letter-n-grams a word as a sequence of characters. Experiments show that separating optical and language model can be a solution for multilingual transfer learning.
关键词： Optical model,Language model,knowledge transfer,Handwriting recognition
更新于2025-09-23 15:22:29
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Estimation of Uncertainty in the Lateral Vibration Attenuation of a Beam with Piezo-Elastic Supports by Neural Networks
摘要： Quantification of uncertainty in technical systems is often based on surrogate models of corresponding simulation models. Usually, the underlying simulation model does not describe the reality perfectly, and consequently the surrogate model will be imperfect. In this article we propose an improved surrogate model of the vibration attenuation of a beam with shunted piezoelectric transducers. Therefore, experimentally observed and simulated variations in the vibration attenuation are combined in the model estimation process, by using multi–layer feedforward neural networks. Based on this improved surrogate model, we construct a density estimate of the maximal amplitude in the vibration attenuation. The density estimate is used to analyze the uncertainty in the vibration attenuation, resulting from manufacturing variations.
关键词： Density estimation,neural network,uncertainty quantification,imperfect model,surrogate model
更新于2025-09-23 15:22:29
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[IEEE 2018 25th IEEE International Conference on Image Processing (ICIP) - Athens, Greece (2018.10.7-2018.10.10)] 2018 25th IEEE International Conference on Image Processing (ICIP) - A Retina-Inspired Encoder: An Innovative Step on Image Coding Using Leaky Integrate-and-Fire Neurons
摘要： This paper aims to build an image coding system based on a model of the mammalian retina. The retina is the light-sensitive layer of tissue located on the inner coat of the eye and it is responsible for vision. Inspired by the way the retina handles and compresses visual information and based on previous studies we aim to build and analytically study a retinal-inspired image quantizer, based on the Leaky Integrate-and-Fire (LIF) model, a neural model approximating the behavior of the ganglion cells of the Ganglionic retinal layer that is responsible for visual data compression. In order to have a more concrete view of the encoder's behavior, in our experiments, we make use of the spatiotemporal decomposition layers provided by extensive studies on a previous retinal layer, the Outer Plexiform Layer (OPL). The decomposition layers produced by the OPL, are being encoded using our LIF image encoder and then, they are reconstructed to observe the encoder's efficiency.
关键词： weighted difference of Gaussians,neural coding,Leaky Integrate-and-Fire (LIF) model,Ganglion cells,image coding,Retina
更新于2025-09-23 15:22:29
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Design of a distributed compliant mechanism using spring-lever model and topology optimization for piezoelectrically actuated flapping wings
摘要： We present a distributed compliant mechanism, which acts like a transmission between a flapping wing of a micro air vehicle and a laminated piezoelectric actuator. The piezoelectric bimorph actuator is connected in cantilever configuration with the compliant mechanism at its free end. The mechanism takes translational deflection at its input from the piezoelectric actuator to provide angular deflection at its output, which causes flapping. We used spring-lever model and topology optimization to obtain the design of the mechanism. The design of the mechanism has been finalized by analyzing the design considering beam model with geometric nonlinearity. The final mechanism is a planar structure of 1 mm thickness and 40 mm × 24 mm in-plane footprint. The input stiffness of the compliant mechanism is 711 N/m and the output torsional stiffness is 0.014 Nm/rad. The compliant mechanism is tested with a piezoelectric bimorph actuator. The mechanism takes ±1 mm deflection with ±0.2 N block force at 30 Hz as an input and produces ±6° flap angle at 30 Hz as an output. The first fundamental frequency of the mechanism is 391 Hz, which is almost 13 times greater than our assumed wing flapping frequency 30 Hz. The final mechanism is prototyped with a 3D printer using VeroWhitePlus RGD835 material and tested with a piezoelectric bimorph actuator using a bench-top experimental set-up.
关键词： Mechanism,flapping,piezo-actuated flapping mechanism,flapping wing micro air vehicle,spring-lever model,distributed compliant mechanism,topology optimization
更新于2025-09-23 15:22:29