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Experimental verification of turbidity tolerance of stereo-vision-based 3D pose estimation system
摘要： This paper presents the verification of the turbidity tolerance of a stereo-vision-based 3D pose estimation system for underwater docking applications. To the best of the authors’ knowledge, no studies have yet been conducted on 3D pose (position and orientation) estimation against turbidity for underwater vehicles. Therefore, the effect of turbidity on the 3D pose estimation performance of underwater vehicles and a method of operating under turbid conditions were studied in this work. A 3D pose estimation method using the real-time multi-step genetic algorithm (RM-GA) proposed by the authors in the previous works shows robust pose estimation performance against changing environmental conditions. This paper discusses how and why the RM-GA is well suited to effective 3D pose estimation, even when turbid conditions disturb visual servoing. The experimental results confirm the performance of the proposed 3D pose estimation system under different levels of turbidity. To demonstrate the practical usefulness of the RM-GA, docking experiments were conducted in a turbid pool and a real sea environment to verify the performance and tolerance of the proposed system under turbid conditions. The experimental results verify the robustness of the system against turbidity, presenting a possible solution to a major problem in the field of robotics.
关键词： Robustness against turbidity,Real-time multi-step genetic algorithm,Sea docking,3D pose estimation,Stereo-vision,Visual servoing
更新于2025-09-23 15:23:52
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Flow cytometry and micro-Raman spectroscopy: Identification of hemocyte populations in the mussel Mytilus galloprovincialis (Bivalvia: Mytilidae) from Faro Lake and Tyrrhenian Sea (Sicily, Italy)
摘要： Immunological and structural characteristics of hemocyte populations in the mussel Mytilus galloprovincialis (Bivalvia: Mytilidae), going from two different Sicilian habitats (Faro Lake and Tyrrhenian sea), was investigated by means of two different techniques (flow cytometric and micro-Raman spectroscopy analyses). For this purpose, three hundred and sixty mussels Mytilus galloprovincialis were analyzed during November 2017. They were divided into two equal groups (triplicate sample) on the basis of the site of collection (n = 60 caught in Faro Lake - group A, and n = 60 caught in Tyrrhenian Sea - group B). Some several differences between the species of Faro Lake and Tyrrhenian Sea are observed and ascribed to the disruption of immune parameters induced by the variations of some qualitative water parameters (temperature, salinity, dissolved oxygen, pH, ammonium 10, free chlorine, total chlorine, total phosphate, orthofhosphate) recorded in the two habitats. This study is relevant for monitoring the conditions of the sea and Faro Lake, which is strongly influenced by the currents of the Tyrrhenian Sea. Faro lake is well known for the cultivation of mussels and this is part of a coastal habitat of particular interest, consisted of a peculiar biocenotic complex. Further, for the first time, significant different arrangement in the mussels cell structural organization was evidenced by simply following their highly reproducible Raman biomolecular signatures.
关键词： Hemocyte,Bivalve immunology,Deep-sea,Mussel Mytilus galloprovincialis,Flow cytometry,Raman spectroscopy
更新于2025-09-23 15:23:52
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-doped two-dimensional semiconductor quantum wells
摘要： We present a theoretical study of photoabsorption in n-doped two-dimensional (2D) and quasi-2D semiconductors that takes into account the interaction of the photocreated exciton with Fermi-sea (FS) electrons through (i) Pauli blocking, (ii) Coulomb screening, and (iii) excitation of FS electron-hole pairs—that we here restrict to one. The system we tackle is thus made of one exciton plus zero or one FS electron-hole pair. At low doping, the system ground state is predominantly made of a 'trion-hole'—a trion (two opposite-spin electrons plus a valence hole) weakly bound to a FS hole—with a small exciton component. As the trion is poorly coupled to photon, the intensity of the lowest absorption peak is weak; it increases with doping, thanks to the growing exciton component, due to a larger coupling between two-particle and four-particle states. Under a further doping increase, the trion-hole complex is less bound because of Pauli blocking by FS electrons, and its energy increases. The lower peak then becomes predominantly due to an exciton dressed by FS electron-hole pairs, that is, an exciton-polaron. As a result, the absorption spectra of n-doped semiconductor quantum wells show two prominent peaks, the nature of the lowest peak turning from trion-hole to exciton-polaron under a doping increase. Our work also nails down the physical mechanism behind the increase with doping of the energy separation between the trion-hole peak and the exciton-polaron peak, even before the anticrossing, as experimentally observed.
关键词： Fermi sea,trion-hole complex,exciton-polaron,photoabsorption,Pauli blocking,n-doped semiconductors,Coulomb screening
更新于2025-09-23 15:23:52
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Oil Slick Detection in the Offshore Domain: Evaluation of Polarization-Dependent Sar Parameters
摘要： Remote sensing technology is an essential link in the global monitoring of the ocean surface and radars are efficient sensors for detecting marine pollution. When used operationally, a tradeoff must usually be made between the covered area and the quantity of information collected by the radar. To identify the most appropriate imaging mode, a methodology based on Receiver Operating Characteristic (ROC) curve analysis has been applied to an original dataset collected by an airborne system, SETHI, characterized by a very low instrument noise floor. The dataset was acquired during an oil spill clean-up exercise carried out in 2015 in the North Sea. Various polarization-dependent quantities are investigated and a relative ordering of the main polarimetric parameters is reported. VV offers the best tradeoff between the benefit of detection performance and the instrument and data requirements. When the sensor has a sufficiently low noise floor, HV is also recommended because it provides strong slick-sea contrast. Among all the investigated quad-polarimetric settings, no significant added value compared to single-polarized data was found.
关键词： NESZ,noise floor,sea,spill,detection,SAR,noise,slick,radar,marine pollution,probability of detection,oil,ROC curves,probability of false alarm,ocean,polarization
更新于2025-09-23 15:23:52
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Sea Ice Change Detection in SAR Images Based on Collaborative Representation
摘要： Sea ice change detection from synthetic aperture radar (SAR) images is important for navigation safety and natural resource extraction. This paper proposed a sea ice change detection method from SAR images based on collaborative representation. First, neighborhood-based ratio is used to generate a difference image (DI). Then, some reliable samples are selected from the DI by hierarchical fuzzy C-means (FCM) clustering. Finally, based upon these samples, collaborative representation method is utilized to classify pixels from the original SAR images into unchanged and changed class. From there, the final change map can be obtained. Experimental results on two real sea ice datasets demonstrate the superiority of the proposed method over two closely related methods.
关键词： sea ice change detection,synthetic aperture radar,clustering method,collaborative representation
更新于2025-09-23 15:23:52
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Dust Detection and Aerosol Properties Over Arabian Sea Using MODIS Data
摘要： The present study deals with the use of Moderate Resolution Imaging Spectroradiometer (MODIS) thermal infrared bands in the dust detection. Eight dust storm cases over the Arabian Sea have been selected (four TERRA and four AQUA) during the year 2002–2008. The brightness temperature (BT) difference method has been applied on MODIS thermal bands 29 (8 μm), 31 (11 μm) and 32 (12 μm) to detect dust storms over the Arabian Sea. The performance assessment of BT differences (BT29–BT31 and BT31–BT32) has shown that BT31–BT32 has performed better to BT29–BT31. We suggest that BT31–BT32 is an effective combination of MODIS bands for dust detection over oceans and sea. The maximum (Dmax) and minimum dust (Dmin) intensity locations have also been identified in all the eight dust storm cases. The aerosol properties (aerosol optical thickness, τ; asymmetry factor g and Angstrom exponent α) over Dmax and Dmin have been studied using MODIS Level 2 data. In AQUA dust storms cases τ values (Dmax) were higher than TERRA dust cases, whereas g values were nearly same. The α was always positive in case of TERRA dust cases; however in AQUA negative α was also reported. Afternoon dust storms are more intense compared to forenoon dust storms and dust particles are also coarser.
关键词： BT difference,Arabian Sea,Dust detection,MODIS,Dust aerosol properties
更新于2025-09-23 15:23:52
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Validation of Wave and Wind Product of the New Phase Saral Using Buoys Data
摘要： Since July 4th 2016, the SARAL/Altika has been moved in a new orbit, and it has continuously provided wave height measurements for more than 1 year. Before using these data, the measurements need to be validated. Based on the in-situ buoys from the National Data Buoy Center (NDBC), the SARAL Ka-band significant wave height (SWH) and Sea Surface Wind (SSW) measurements were validated and have been corrected using a linear regression with in-situ measurements. Compared with NDBC data, the validation results of SARAL show a RMS (Root Mean Square) of 0.28 m for SARAL SWH measurements and RMS of 1.30m/s for SARAL SSW speed indicating capability of AltiKa providing SWH and wind speed products with reliable accuracy. Therefore the accuracy of SARAL SWH products is higher than that of Jason-1/2 SWH data, and does not require any correction.
关键词： Sea Surface Wind,SARAL/AltiKa,Validation,Root Mean Square,Significant Wave Height
更新于2025-09-23 15:22:29
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Sea Clutter Cancellation for Passive Radar Sensor Exploiting Multi-Channel Adaptive Filters
摘要： Sea clutter suppression in passive radar sensor is a challenging problem because the Doppler frequencies of low-velocity sea-surface targets are typically close to the spectrum of the sea clutter. Conventional approaches based on single-channel high-pass filters are effective for clutter suppression only when the clutter is concentrated in low Doppler region. For sea clutter that has a spread spectrum, however, these approaches have to compromise target signal reception. That is, they either form a narrow notch which does not effectively suppress clutter, or generate a broadened null that simultaneously mitigates low-velocity target signals. Therefore, it is desirable to design a filter that forms a notch broad enough to cover the entire clutter spectrum, with the frequency response rising sharply to a high gain outside the clutter band. Toward this end, in this paper, we develop a generalized multi-channel adaptive filter which, by forming multiple sharp notches over a set of discrete frequencies within the clutter spectrum, achieves effective clutter suppression and target signal preservation. We focus on the fast frequency-domain implementation, and the performance analysis in terms of the frequency response, signal energy loss, and computational complexities is also presented. The effectiveness of the proposed approaches is verified using real-data results.
关键词： interference cancellation,sea clutter,multi-channel adaptive filter,Passive radar sensor,normalized least mean square (NLMS)
更新于2025-09-23 15:22:29
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[IEEE 2018 OCEANS - MTS/IEEE Kobe Techno-Ocean (OTO) - Kobe, Japan (2018.5.28-2018.5.31)] 2018 OCEANS - MTS/IEEE Kobe Techno-Oceans (OTO) - Monitoring and Communication System Design for A Deep-Sea Unmanned Submersible
摘要： Underwater vehicle is an important equipment for ocean monitoring and exploitation, and has been attracting more researchers and practitioners. Deep-sea unmanned submersible is a special type of underwater vehicle. This paper designs the monitoring and communication system for a deep-sea unmanned submersible using LABVIEW. The monitoring system includes initialization interface module, state display module and remote intervene module. The communication system consists of WIFI communication module, iridium communication module, underwater acoustic communication, and communication protocol between the monitoring computer on the surface ship and the submersible. The designed monitoring and communication system will be very helpful for operating the submersible in a safe and efficient way.
关键词： monitoring,LABVIEW,underwater acoustic communication,deep-sea unmanned submersible
更新于2025-09-23 15:22:29
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[IEEE 2018 OCEANS - MTS/IEEE Kobe Techno-Ocean (OTO) - Kobe, Japan (2018.5.28-2018.5.31)] 2018 OCEANS - MTS/IEEE Kobe Techno-Oceans (OTO) - A Dimension-Reduced Modal Space Detector in Deep-Sea Environment
摘要： The matched correlation detector (MCD), combining the received data with the sound transfer function (namely the replica field) is theoretically optimal for underwater passive detection. However, it suffers from the model mismatch problem caused by environmental uncertainties. And furthermore, when applied to the deep-sea environment, it encounters the large search range problem. In this paper, we focus on the source detection problem in deep-sea environment. To overcome the disadvantages of MCD, we choose the modal space detector (MSD) which uses a vertical linear array (VLA). We derive the expression of the deep-sea MSD and further, to improve the signal-to-noise ratio (SNR) of the test statistic, we propose a dimension-reduced form of MSD, which is termed as DR-MSD for short. By numerical simulation, we discuss that how source frequency, array depth and array aperture influence the dimension reduction. And we point out that the dimension-reduced number in DR-MSD decreases when the source frequency and the VLA aperture increase. The numerical results also indicate that DR-MSD can alleviate the search burden and obtain a better detection performance when compared to traditional MSD.
关键词： underwater acoustic,passive source detection,Deep-sea environment,dimension reduction,MSD
更新于2025-09-23 15:22:29