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- 摘要
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[IEEE 2019 IEEE 30th Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC) - Istanbul, Turkey (2019.9.8-2019.9.11)] 2019 IEEE 30th Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC) - Transmit Laser Selection for Underwater Visible Light Communication Systems
摘要： Visible light communication (VLC) has the potential to serve as a high-speed underwater wireless connectivity solution to support real-time image and video transmission. Underwater propagation medium imposes additional challenges on the design of VLC systems which were originally proposed for indoor applications. Temperature and salinity fluctuations result in fluctuations of the refractive index of seawater and eventually introduce turbulence-induced fading. In this paper, to mitigate the effects of fading, we propose transmit laser selection for a diver-to-diver underwater VLC link where the transmitter has multiple laser sources and the receiver has one photodetector. The source with the highest received instantaneous signal-to-noise ratio is selected for transmission while the remaining sources remain idle. We derive a closed-form expression for asymptotical bit error rate over log-normal distributed underwater turbulence channels and derive the achievable diversity order. We further present simulation results to confirm our derivations and diversity gain analysis.
关键词： bit error rate performance,underwater optical turbulence,transmit laser selection,diversity order,Underwater visible light communication
更新于2025-09-16 10:30:52
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[IEEE OCEANS 2019 - Marseille - Marseille, France (2019.6.17-2019.6.20)] OCEANS 2019 - Marseille - Laser Stripe Bathymetry using Particle Filter SLAM
摘要： This paper presents a novel application of BPSLAM from Barkby et al [1], onto underwater laser mapping. BP-SLAM is a featureless bathymetry mapping algorithm that uses Distributed Particle Mapping and a Rao-Backwelized Particle Filter (RBPF) to handle both navigational estimates and seafloor bathymetry estimates. By weighting the particles in the RBPF with the most self-consistent map, the bathymetric maps and the robot navigation are corrected.
关键词： Underwater robots,Underwater reconstruction,Bathymetric SLAM
更新于2025-09-16 10:30:52
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A Review on Practical Considerations and Solutions in Underwater Wireless Optical Communication
摘要： Underwater wireless optical communication (UWOC) has attracted increasing interest in various underwater activities because of its order-of-magnitude higher bandwidth compared to acoustic and radio-frequency technologies. Testbeds and pre-aligned UWOC links were constructed for physical layer evaluation, which verified that UWOC systems can operate at tens of gigabits per second or close to a hundred meters of distance. This holds promise for realizing a globally connected Internet of Underwater Things (IoUT). However, due to the fundamental complexity of the ocean water environment, there are considerable practical challenges in establishing reliable UWOC links. Thus, in addition to providing an exhaustive overview of recent advances in UWOC, this paper addresses various underwater challenges and offers insights into the solutions for these challenges. In particular, oceanic turbulence, which induces scintillation and misalignment in underwater links, is one key factor in degrading UWOC performance. Novel solutions are proposed to ease the requirements on pointing, acquisition, and tracking (PAT) for establishing robustness in UWOC links. The solutions include light-scattering-based non-line-of-sight (NLOS) PAT-relieving communication modality as well as scintillating-fiber-based photoreceiver and large-photovoltaic cells as the optical signal detectors. Naturally, the dual-function photovoltaic–photodetector device readily offers a means of energy harvesting for powering up future IoUT sensors.
关键词： non-line-of-sight,Underwater wireless optical communication,energy harvesting,turbulence,fiber detector
更新于2025-09-16 10:30:52
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Performance Analysis of Submerged Polycrystalline Photovoltaic Cell in Varying Water Conditions
摘要： Exploring the underwater solar energy by solar photovoltaic (PV) cells leads to a huge advantage by utilizing the humongous space of water covered by the earth’s surface. Even though the amount of solar radiation decreases with the depth of the water, water provides sustainable cooling and cleaning for solar PV cells underwater. There are many challenges and constraints to develop solar PV cells underwater because they are mostly calibrated and amenable to space, dryland, terrestrial, etc., and the solar spectrum is prone to get narrower with the depth of the water. The implementation of solar PV cells underwater is pliable in various commercial and defense applications, such as sensors, water monitoring systems, autonomous vehicles, underwater gliders, etc. In this article, first, a mathematical model has been developed for the solar cell spectrum to incorporate the changes in the solar irradiance with the depth of the water. Furthermore, an experimental setup was designed and implemented to mimic an underwater environment. The performance of the polycrystalline encapsulated solar cell was studied based on the different types of water and the depth of the solar cell underwater. This article manifests that there is a sufficient amount of underwater solar power that can be utilized using PV cells to operate various devices and systems.
关键词： polydimethylsiloxane (PDMS),Photovoltaic (PV) cells,underwater solar power,polycrystalline solar cell,solar spectrum,water salinity,solar irradiance
更新于2025-09-16 10:30:52
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A Mathematical Model of Laser Radiation Propagation in Seawater
摘要： Based on the well-known models of optical properties of a seawater layer in the spectral range of 530–550 nm, a mathematical model of the propagation of laser radiation is proposed. The mathematical model is obtained by solving radiative transfer equation for a narrow beam using a few-parameter approximation of the scattering indicatrix of the seawater layer. The model makes it possible to determine the spatial distribution of irradiance at a given distance from the laser radiation source by the known Secchi disk depth. The results of numerical experiments for water areas with known optical properties are given.
关键词： water inherent optical properties,turbid medium,optical radiation transfer,underwater vision system
更新于2025-09-16 10:30:52
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[IEEE 2019 16th Canadian Workshop on Information Theory (CWIT) - Hamilton, ON, Canada (2019.6.2-2019.6.5)] 2019 16th Canadian Workshop on Information Theory (CWIT) - Angular MIMO for Underwater Wireless Optical Communications: Channel Modelling and Capacity
摘要： An alternative architecture for imaging multiple-input/multiple-output (MIMO) underwater wireless optical communications (UWOCs) is proposed which relies on the transmission in angle rather than directly in space. The angular MIMO (A-MIMO) system has advantages over conventional underwater MIMO systems (C-MIMO) in that the image magni?cation is invariant to link range, and angular transmission greatly relaxes the alignment requirements of such links. These features are especially important for underwater wireless sensor networks (UWSNs), where the maintaining alignment between underwater vehicles and ?oating sensors nodes may be dif?cult in such dynamic environments. In this paper, we describe the architecture of A-MIMO for underwater channels and numerically characterize it in clear and coastal seawater conditions. For comparison a C-MIMO underwater system with similar parameters is also characterized and the channel capacities for A-MIMO and a C-MIMO are contrasted against link distances and misalignment errors. The numerical results show that A-MIMO maintains the link capacity against the misalignment conditions far better than C-MIMO while using a smaller size transceiver.
关键词： angular MIMO,link capacity,underwater optical wireless communication,misalignment,angle of arrival
更新于2025-09-16 10:30:52
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Post Equalization Scheme Based on Deep Neural Network for a Probabilistic Shaping 128 QAM DFT-S OFDM Signal in Underwater Visible Light Communication System
摘要： We have presented a post equalization scheme based on Deep Neural Network (DNN) for DFT-S OFDM modulation using (PS) technique in underwater visible light communication (VLC) system. By this method, we successfully demonstrated a data rate of 1.74Gbit/s PS128QAM DFT-S OFDM modulation over 1.2meter underwater optical transmission with bit error rate (BER) below 7% FEC threshold of 3.8×10-3. Compared to the typical PS128QAM DFT-S OFDM modulation without DNN, the proposed method would lead to an improvement of system capacity of 5.4% by increasing the data rate by 90 Mbps. The experimental results validate that the proposed DNN-based post equalization scheme for odd order QAM PS technique can be a promising solution for future high speed underwater VLC system.
关键词： Probabilistic Shaping (PS),odd order QAM,Deep Neural Network (DNN),Underwater VLC,Discrete Fourier Transform-Spread (DFT-S) OFDM
更新于2025-09-16 10:30:52
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Analysis of the Application of Laser Welding Technology on Maintenance of the Underwater Components of Nuclear Power Station
摘要： This paper put its eyes on the PWR’s underwater components which have the risk of early failure after long-term inservice because the material tends to deteriorate and embrittle due to irradiation and other factors, and should be maintenanced. In this paper, we contrastively analyse two main technologies used as underwater welding, named underwater wet laser welding and underwater local dry laser welding. It is difficult to obtain high quality weld seam by underwater wet laser welding for the reason of some disadvantages on laser beam underwater, such as water attenuation, bubble reflection and so on. On constract, underwater local dry laser-welding can obtain high quality weld-joints, and becomes the current hotshot. But, there are still some problems to be settled, such as the way to obtain stable underwater chamber and the protection of back of full penetration weld. Analysis of the retrieva of underwater laser welding on Web Science, we can find that underwater laser welding technology has step out laboratory to engineering application and the in-depth theoretical research is also actively carried out on the fields of picosecond, femtosecond laser.
关键词： local dry laser welding,PWR,underwater laser welding,maintenance,wet laser welding
更新于2025-09-16 10:30:52
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Spectral characteristics of underwater laser-induced breakdown spectroscopy at high pressure conditions
摘要： Laser-induced breakdown spectroscopy (LIBS) has been proven to be an attractive technique for the in-situ oceanic applications. However, when applying LIBS into deep-sea, the pressure effect caused by different ocean depth is inescapable and could have great influence on the LIBS signals. In this work, spectral characteristics of underwater LIBS were investigated as a function of pressure in the range of 0.1–45 MPa. A high-pressure chamber built in the laboratory was used to simulate the high-pressure environment of deep-sea. Optimal laser energy and detection delay were first determined under different pressure conditions and were shown to be independent on the external pressure. The increase in pressure has a significant impact both on the peak intensity and line broadening of the observed spectra. The peak intensity of Na, Li and K lines increases with the increasing pressure until a maximum intensity reached at 12.5 MPa. Above this value, the peak intensity decreases gradually up to 45 MPa. For Ca line, the maximum intensity was observed at 30 MPa. The line broadening keeps constant at low pressures from 0.1 to 10 MPa while it increases linearly at higher pressures, indicating a higher electron density caused by the compression effect of the high external pressure. We also compared the spectral data obtained from the high-pressure chamber and from the field sea trials, and the good consistency between the laboratory data and sea-trial data suggested the key role of pressure effect on underwater LIBS signals for the practical deep-sea applications.
关键词： high-pressure chamber,underwater laser-induced breakdown spectroscopy,deep-sea application,pressure effect,spectral characteristics
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Electrical Signatures of Contact Degradation for c-Si Solar Cells
摘要： Time synchronization is an important, yet challenging, problem in underwater sensor networks (UWSNs). This challenge can be attributed to: 1) messaging timestamping; 2) node mobility; and 3) Doppler scale effect. To mitigate these problems, we present an acoustic-based time-synchronization algorithm for UWSN, where we compare several message time-stamping algorithms in addition to different Doppler scale estimators. A synchronization system is based on a bidirectional message exchange between a reference node and a slave one, which has to be synchronized. Therefore, we take as reference the DA-Sync-like protocol (Liu et al., 2014), which takes into account node’s movement by using first-order kinematic equations, which refine Doppler scale factor estimation accuracy, and result in better synchronization performance. In our study, we propose to modify both time-stamping and Doppler scale estimation procedures. Besides simulation, we also perform real tests in controlled underwater communication in a water test tank and a shallow-water test in the Mediterranean Sea.
关键词： timestamp,skew,Doppler scale,orthogonal frequency-division multiplexing (OFDM),time synchronization,underwater sensor network (UWSN),Acoustic communication
更新于2025-09-16 10:30:52