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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Analysis of Marlene Radar Data: Focus on Doppler Spectra and Group Lines
摘要： This paper deals with some results of the campaign called MARLENE (for MediterraneAn RFC and cLutter Environmental Experiment), already presented in [1]. During the campaign, radar data were acquired at C, X, Ku, Ka and W bands leading to a large amount of results at low grazing angle with a very high spatial resolution. Doppler spectra in VV polarization with large Doppler shifts are presented here. Then, a focus on the dispersion diagram (2D Fourier transform of the RCS in space and time) is carried out. Finally, a study of the low-frequency pattern observed in the dispersion diagram, called group line, is introduced.
关键词： dispersion diagram,Low-grazing measurements,sea surface radar scattering,Doppler spectrum
更新于2025-09-09 09:28:46
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Feature Enhanced Sar Tomography Reconstruction Through Adaptive Nonparametric Array Processing
摘要： Synthetic aperture radar (SAR) tomography (TomoSAR) employs array signal processing techniques, in order to estimate the location of the vertical structures that compose the backscattering field, in the direction perpendicular to the line-of-sight (PLOS). Due to the limited number of tracks for practical TomoSAR sensing scenarios, it becomes challenging to accurately estimate the source parameters. Additionally, irregular sampling and non-uniform acquisition constellations introduce artifacts and increase ambiguity. The usage of super-resolved parametric methods and compressed sensing (CS) based approaches, improve the vertical resolution and mitigate the effect of sidelobes. However, parametric approaches have the main drawback related to the assumption that the scene is composed by a known finite number of point-type backscattering sources. Also, the CS-based techniques regularly imply a considerable computational burden. Overcoming the disadvantages of the above mentioned TomoSAR-adapted methods, this paper presents a novel non-parametric iterative approach for feature enhanced SAR tomography, in the context of maximum likelihood (ML) estimation theory. The feature enhancing capabilities of the proposed technique are corroborated via processing L-band airborne TomoSAR data of the German Aerospace Center (DLR), acquired by the F-SAR system over the forested test site of Froschham, Germany, in 2017.
关键词： power spectrum pattern (PSP),spectral analysis (SA),synthetic aperture radar (SAR) tomography (TomoSAR),Maximum likelihood (ML)
更新于2025-09-09 09:28:46
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Histogram-Based Autoadaptive Filter for Destriping NDVI Imagery Acquired by UAV-Loaded Multispectral Camera
摘要： Combinations of unmanned aerial vehicles (UAVs) and multispectral sensors provide low-cost approaches for detailed spatiotemporal vegetation studies. However, the resulting vegetation index images such as normalized difference vegetation index (NDVI) have unignorable stripe noise and seriously disturb the extraction of vegetation information. In this letter, the similar frequency phenomena caused by stripe noise were observed in the gray-scale histogram and the Fourier spectrum of a striped NDVI image. Thus, we tried establishing the empirical quantitative relationship between them, and then designed an autoadaptive ?lter for stripe noise removal in Fourier spectrum according to the characteristics including the dominant peak and troughs of the histogram curve of the raw NDVI image. Applying this autoadaptive ?lter to the corresponding Fourier spectrum image, we achieved automatic and effective stripe noise removal without any manual interference. Based on visual judgment and quantitative evaluation, the proposed autoadaptive ?lter demonstrated by far the better performance in retaining image ?delity and intelligibility than the improved high-pass ?lter and 2-D Weiner ?lter.
关键词： Agricultural multispectral camera (ADC) lite,auto-adaptive ?lter,stripe noise,image histogram,unmanned aerial vehicles (UAV),Fourier spectrum,normalized difference vegetation index (NDVI)
更新于2025-09-09 09:28:46
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A Stochastic Gradient Approach for Robust Heartbeat Detection with Doppler Radar Using Time-Window-Variation Technique
摘要： Heart rate variability (HRV) indicates health condition and mental stress. The development of non-contact heart rate (HR) monitoring technique with Doppler radar is attracting great attentions. However, the performance of heartbeat detection via radar signal easily degrades, due to respiration and body motion. In this paper, first, a stochastic gradient approach is applied to reconstruct high-resolution spectrum of heartbeat, by proposing the zero-attracting sign least-mean-square (ZA-SLMS) algorithm. To correct the quantized gradient of cost function, and penalize the sparse constraint on the updating spectrum, more accurate heartbeat spectrum is reconstructed. Then, to better adapt to the noises with different strengths caused by subjects’ movements, an adaptive regularization parameter (AREPA) is introduced in the ZA-SLMS algorithm as an improved variant, which can adaptively regulate the proportion between gradient correction and sparse penalty. Moreover, in view of the stability of location of spectral peak associated with HR when the size of time window slightly changes, a time-window-variation (TWV) technique is further incorporated in the improved ZA-SLMS (IZA-SLMS) algorithm, for more stable HR estimation. Through the experiments on five subjects, our proposal is demonstrated to bring a significant improvement of accuracy against existing detection methods. Specifically, the IZA-SLMS algorithm with TWV achieves the smallest average error of 3.79 beats per minute (BPM), when subjects type with a laptop.
关键词： Doppler radar,Non-contact heartbeat detection,sparse spectrum reconstruction (SSR),adaptive filter,time-window-variation (TWV),heart rate (HR)
更新于2025-09-09 09:28:46
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Crosstalk-Aware Core and Spectrum Assignment in a Multicore Optical Link with Flexible Grid
摘要： Multicore Fibers (MCFs) are one of the main technological enablers for Space Division Multiplexing. In principle, MCFs could scale the fiber capacity by a factor equal to the number of cores, but in practice such increase is hindered by transmission impairments due to the inter-core crosstalk between adjacent lit cores. The entity of such crosstalk depends on the number of cores and on their disposition within the fiber cladding, but also on the baud rate and modulation format used for transmission. As first MCF applications are expected over point-to-point systems, in this study we concentrate on the resource allocation over a single link. Specifically, we study the Baud rate, Modulation format, Core and Spectrum Assignment (BMCSA) problem in a multicore flexi-grid link, considering distance-adaptive reaches for different baud rates, modulation formats and crosstalk impairments. We show that the problem is NP-hard and provide two integer linear programs, as well as heuristic approaches to solve it over large/practical traffic instances. Our problem formulations incorporate modelling of the exact inter-core crosstalk contributions depending on the number of lit neighbor cores. Numerical results are provided in a high-spatial-efficiency 19-core fiber considering different transmission impairment conditions.
关键词： Multi-core optical fibers,Inter-core crosstalk,Core and Spectrum Assignment
更新于2025-09-09 09:28:46
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Effect of deposition rate on the growth mechanism of microcrystalline silicon thin films using very high frequency PECVD
摘要： The intrinsic microcrystalline silicon thin films were deposited by very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD). Two series of films with different deposition rate 0.30 nm/s and 1.94 nm/s were prepared. The film surface and gas phase reaction growth processes were monitored with real-time spectroscopic ellipsometry and optical emission spectroscopy. The effect of deposition rate on the microcrystalline silicon thin film growth mechanism has been studied. The microcrystalline silicon surface growth was analyzed with KPZ model. The results show that the growth exponent of β is 0.448 for the films with low deposition rate, and the growth exponent of β is 0.302 for the films with high deposition rate. The growth exponent does not increase with deposition rate, but declines. And the reasons for this phenomenon were explained.
关键词： Real time spectroscopic ellipsometry,Microcrystalline silicon,High rate deposition,Optical emission spectrum,Growth mechanism
更新于2025-09-09 09:28:46
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Ultrafast nuclear dynamics in the doubly-core-ionized water molecule observed via Auger spectroscopy
摘要： We present a combined experimental and theoretical study of the Auger-emission spectrum following double core ionization and excitation of gas-phase water molecules with hard-x-ray synchrotron radiation above the O K ?2 threshold. We observe an indication of ultrafast proton motion occurring within the 1.5 fs lifetime of the double-core-hole (DCH) states in water. Furthermore, we have identi?ed symmetric and antisymmetric dissociation modes characteristic for particular DCH states. Our results serve as a fundamental reference for state-of-the-art studies of DCH dynamic processes in liquid water both at synchrotron and free-electron-laser facilities.
关键词： double core ionization,Auger-emission spectrum,synchrotron radiation,ultrafast proton motion,DCH states
更新于2025-09-09 09:28:46
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Design of a frequency spectrum-based versatile two-dimensional arbitrary shape filter bank: application to contact lens detection
摘要： A filter bank (FB) is an integral part of any image processing system. The designing of a FB generally involves modifying an existing FB or focusing on a particular property of the filter bank. Such FBs limit their use to a particular image. Through our work, we have devised a unique and novel approach for designing a two-dimensional arbitrary shape filter bank (2-D ASFB). This FB is inherently 2-D and eliminates the need for transforming a one-dimensional FB into 2-D. Its arbitrary nature expands its application to any image as compared to regular-shaped FBs currently in use. The novelty of the design lies in the fact that the designed FB can match the frequency spectrum of any image by reducing the error function between the frequency spectrum and the desired filter response of the FB. The error function has been minimized using the eigenfilter approach. After designing the low-pass analysis filter, perfect reconstruction constraint has been used to get a low-pass synthesis filter. In this paper, we have demonstrated the use of the 2-D ASFB specifically for contact lens detection (CLD). The proposed CLD system focuses on feature extraction using the 2-D ASFB. The support vector machine classifier is the same as in the existing systems. The results show improved correct classification rate as compared to the existing systems for IIITD and ND2013 contact lens database. This 2-D ASFB overcomes limitations posed by the existing filter banks with respect to separability, directionality, orthogonality, and shape. This FB can be effectively applied to any feature extraction application such as pattern recognition, biometrics, medical image processing.
关键词： Eigenfilter,Contact lens detection,Feature extraction,Filter bank,Frequency spectrum
更新于2025-09-09 09:28:46
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Normal mode splitting in quantum degenerate Fermi gas in nano-cavity
摘要： We report the normal mode splitting in the fermionic displacement spectrum as a single mode light field interacts with a mechanical mode of ultra-cold quantum degenerate Fermi gas trapped inside a Fabry–Pérot cavity in the strong coupling regime. We explain the normal mode splitting in the outgoing field of the cavity field and in the field quadratures as well. As a function of system parameters, such as coupling strength between fermionic mode and field mode, number of fermionic atoms, cavity decay rate and fluctuations associated with the fermionic mode we explain the phenomenon of normal mode splitting. The low-lying fermions ensemble displays a collective density oscillation associated with particle-hole excitations, which interacts with cavity light field and lead to the observation of NMS in the fermion quadratures and light modes. The numerical results based on the present day laboratory experiments agree with the obtained analytical results.
关键词： Fabry–Pérot cavity,quantum degenerate Fermi gas,Normal mode splitting,fermionic displacement spectrum,strong coupling regime
更新于2025-09-09 09:28:46
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Arbitrary amplitude femtosecond pulse shaping via a digital micromirror device
摘要： An ultrafast spectrum programmable femtosecond laser may enhance the performance of a wide variety of scientific applications, e.g., multi-photon imaging. In this paper, we report a digital micromirror device (DMD)-based ultrafast pulse shaper, i.e., DUPS, for femtosecond laser arbitrary amplitude shaping — the first time a programmable binary device reported to shape the amplitudes of ultrafast pulses spectrum at up to 32 kHz rate over a broad wavelength range. The DUPS is highly efficient, compact, and low cost based on the use of a DMD in combination with a transmission grating. Spatial and temporal dispersion introduced by the DUPS is compensated by a quasi-4-f setup and a grating pair, respectively. Femtosecond pulses with arbitrary spectrum shapes, including rectangular, sawtooth, triangular, double-pulse, and exponential profile, have been demonstrated in our experiments. A feedback operation process is implemented in the DUPS to ensure a robust and repeatable shaping process. The total efficiency of the DUPS for amplitude shaping is measured to be 27%.
关键词： digital micromirror device,Spectrum shaping,ultrafast laser
更新于2025-09-09 09:28:46