- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Parametric Study of Underwater Laser Welding on 304 Austenite Stainless Steel
摘要： The underwater laser welding assisted by a single-layer gas torch was carried out on the austenite stainless steel based on the underwater laser welding experimental platform. Butt welding experiments under shallow water were performed to investigate the effects of laser power, welding speed and defocusing distance on the underwater laser welding quality and optimized the process parameters. It was found that the ideal underwater laser weld can be obtained with the laser power of 2.0 kW, the welding speed of 2.0 m/min and the defocusing distance of 1 mm, demonstrating the self-developed single-layer gas-assisted drainage device could create working environment similar to onshore laser welding, by analyzing the metallographic structure and mechanical properties of underwater laser weld and in-air laser weld.
关键词： austenite stainless steel.,Underwater welding,laser welding
更新于2025-09-11 14:15:04
-
[IEEE 2019 14th IEEE Conference on Industrial Electronics and Applications (ICIEA) - Xi'an, China (2019.6.19-2019.6.21)] 2019 14th IEEE Conference on Industrial Electronics and Applications (ICIEA) - Signature-Based Morse Code Encoding for a LED-Based optical Layer 2 data communication
摘要： With the rapid improvements in engineering technology, underwater communications have gained major interests from researchers with application areas from commercial to military water based communication systems. However, underwater wireless communication is challenging and difficult compared to wireless terrestrial as it can be easily interrupted due to interference from harsh underwater operation conditions, noise, limited bandwidth and power resources. Various researches in underwater acoustic, optical, and RF communications for secured and reliable underwater wireless network have been carried out. In this paper, an LED based optical wireless communications is proposed using a layered 2 Morse-code based encoding protocol for short distance underwater communication. The proposed system converts the data into a serial of dots and spaces before it is transmitted using the LED as a light source. At the receiver end, the system decodes sequences of on-off light sensed by the photo-diode into the data. The main contribution of this work is the design of a layer 2 signature-based encoding and decoding systems for short range wireless underwater optical communication protocol that can provide a higher data rates compared to traditional acoustic systems with significant lower power consumption and simpler computational complexity. The transmission protocol is evaluated in a dark room and in a water medium. The results have shown above 90% transmission success rate. The result also showed that different colors of the LED emission can affect the reliability of data transmission.
关键词： LED,Transmission Protocol,Optical Communication,Morse Code,Underwater Communication
更新于2025-09-11 14:15:04
-
Laser-based imaging applications in turbid waters
摘要： Underwater laser-based imaging systems and data-processing techniques matured during the past decade. Active imaging systems can, nowadays, be integrated into platforms like remote-operated vehicles (ROV) or autonomous underwater vehicles (AUV). This article gives an overview of different civil and naval applications in underwater imaging with respect to underwater laser scanning (ULS) and laser gated viewing (LGV). Special emphasis has to be given to the environmental conditions, for example, the influence of the local and seasonal dependence of the turbidity with regard to the optical underwater channel. On the basis of tank and sea experiments, advanced techniques for 3D laser oblique scanning (LOS) and possibilities of contrast enhancements for gated viewing are presented.
关键词： laser scanner,laser gated viewing,underwater laser imaging,post-processing
更新于2025-09-11 14:15:04
-
The Encyclopedia of Archaeological Sciences || Underwater Three-Dimensional Laser Imaging
摘要： Three-dimensional (3D) laser imaging systems are devices that emit a laser beam which shines on an object located at meters of distance and that record a portion of the laser light reflected back by the object’s surface. The device processes the received signal and generates a 3D digital model of the object for visualization on a display, where each point of the object’s surface is assigned a set of spatial coordinates in a relative reference frame. The application of 3D laser imaging systems in archaeology and heritage on emerged land has been steadily growing since the 2000s, mainly in view of the considerable progress in opto-electronic technology. Successful applications have been demonstrated for operations at tens of meters of distance from the targeted object (range) and with submillimeter spatial resolution (accuracy).
关键词： heritage,underwater,archaeology,3D laser imaging,opto-electronic technology
更新于2025-09-11 14:15:04
-
Scale Accuracy Evaluation of Image-Based 3D Reconstruction Strategies Using Laser Photogrammetry
摘要： Rapid developments in the field of underwater photogrammetry have given scientists the ability to produce accurate 3-dimensional (3D) models which are now increasingly used in the representation and study of local areas of interest. This paper addresses the lack of systematic analysis of 3D reconstruction and navigation fusion strategies, as well as associated error evaluation of models produced at larger scales in GPS-denied environments using a monocular camera (often in deep sea scenarios). Based on our prior work on automatic scale estimation of Structure from Motion (SfM)-based 3D models using laser scalers, an automatic scale accuracy framework is presented. The confidence level for each of the scale error estimates is independently assessed through the propagation of the uncertainties associated with image features and laser spot detections using a Monte Carlo simulation. The number of iterations used in the simulation was validated through the analysis of the final estimate behavior. To facilitate the detection and uncertainty estimation of even greatly attenuated laser beams, an automatic laser spot detection method was developed, with the main novelty of estimating the uncertainties based on the recovered characteristic shapes of laser spots with radially decreasing intensities. The effects of four different reconstruction strategies resulting from the combinations of Incremental/Global SfM, and the a priori and a posteriori use of navigation data were analyzed using two distinct survey scenarios captured during the SUBSAINTES 2017 cruise (doi: 10.17600/17001000). The study demonstrates that surveys with multiple overlaps of nonsequential images result in a nearly identical solution regardless of the strategy (SfM or navigation fusion), while surveys with weakly connected sequentially acquired images are prone to produce broad-scale deformation (doming effect) when navigation is not included in the optimization. Thus the scenarios with complex survey patterns substantially benefit from using multiobjective BA navigation fusion. The errors in models, produced by the most appropriate strategy, were estimated at around 1% in the central parts and always inferior to 5% on the extremities. The effects of combining data from multiple surveys were also evaluated. The introduction of additional vectors in the optimization of multisurvey problems successfully accounted for offset changes present in the underwater USBL-based navigation data, and thus minimize the effect of contradicting navigation priors. Our results also illustrate the importance of collecting a multitude of evaluation data at different locations and moments during the survey.
关键词： navigation fusion,laser scalers,uncertainty estimation,structure-from-motion,Monte Carlo simulation,laser spot detection,metrology,underwater 3D reconstruction,multiobjective BA,scale drift evaluation,photogrammetry
更新于2025-09-11 14:15:04
-
[IEEE 2019 7th International Conference on Information, Communication and Networks (ICICN) - Macao, Macao (2019.4.24-2019.4.26)] 2019 7th International Conference on Information, Communication and Networks (ICICN) - A Photon Counting Underwater NOMA Wireless Optical Communication System
摘要： In recent years, Underwater wireless optical communication (UWOC) has become one of hot spots of human exploration of the unknown deep-sea space. In this paper, a shot noise limited interleaver iterative non-orthogonal multiple access (NOMA) UWOC system with photon counting is proposed. The characteristics of underwater receiver wireless optical channel are studied. In addition to single receiver scheme, a diversity receiving scheme is also considered. According to the result of simulation, the proposed multi-user system can perform well in very low receiving signal energy, which achieves the bit error rate (BER) performance of 2*10e-5 at 40 photon number per bit for 4-user scenario with 1/10 repetition coding rate. Moreover, this system also has the rapid convergence and good receiving diversity property.
关键词： underwater optical wireless communication,NOMA,photon counting
更新于2025-09-11 14:15:04
-
Effect of light-emitting diodes (LEDs) on snow crab catch rates in the Barents Sea pot fishery
摘要： Snow crab (Chionoecetes opilio) has become an important species for the Norwegian seafood industry since its first commercial harvest in 2012. However, periodically catch rates can be low, causing a financial strain on the fishery. Thus, improving the catch rate of existing pot designs has the potential to significantly improve the profitability of fishing enterprises. In this study, we investigated whether the addition of low-powered purple and white light-emitting diode (LED) fishing lights inside the pots could improve catch rates of snow crab in the Barents Sea. Results showed that pots with purple lights harvested a 12.8% higher catch per unit effort (CPUE; number of crab per pot) of legal-sized crab, which was significantly more than the control pots (p ? 0.035); pots with white lights did not catch significantly more crab (p > 0.05). Pots equipped with only light (no bait) caught very few crabs and were not considered a viable alternative. Although purple LEDs increased snow crab capture, the economic benefits of using underwater lights in pots remains unclear given the high capital investment required.
关键词： underwater fishing light,Barents Sea snow crab fishery,catchability,invasive species,LEDs
更新于2025-09-11 14:15:04
-
Visual Docking Against Bubble Noise With 3-D Perception Using Dual-Eye Cameras
摘要： Recently, many studies have been performed worldwide to extend the persistence of underwater operations by autonomous underwater vehicles. Underwater battery recharging technology is one of the solutions even though challenges still remain. The docking function plays an important role not only in battery recharging but also in other advanced applications, such as intervention. Visual servoing in undersea environments inevitably encounters difficulties in recognizing the environment when captured images are disturbed by noise. This study describes the effective recognition performance and robustness against air bubble disturbances in images captured by a real-time position and orientation (pose) tracking and servoing system using stereo vision for a visual-servoing-type underwater vehicle. The recognition of the vehicle pose based on dynamic images captured by dual video cameras was performed by a real-time multistep genetic algorithm (RM-GA). In previous studies, the docking performance was investigated under the condition that there were no disturbances in the captured images that address image degradation. In this paper, the robustness of the RM-GA against air bubble disturbances was verified through visual servoing and docking experiments in a pool test to confirm that the system can continue to recognize the pose of the 3-D marker and can maintain the desired pose by visual servoing. Then, the effectiveness of the proposed system against real disturbances such as turbidity that may degrade the visibility of the system in the sea was confirmed by conducting the docking experiment in a real sea, having verified the practicality of the proposed method.
关键词： genetic algorithm (GA),Air bubble noises,visual servoing,dual-eye cameras,underwater vehicle
更新于2025-09-11 14:15:04
-
Reducing Adhesion for Dispensing Tiny Water/Oil Droplet and Gas Bubble by Femtosecond Laser-Treated Needle Nozzles: Superhydrophobicity, Superoleophobicity, and Superaerophobicity
摘要： Three-level microstructures were formed on the stainless steel surfaces by simple femtosecond laser ablation. The structured surfaces exhibit superhydrophilicity in air and superoleophobicity/superaerophobicity in water. After further stearic acid modification, the surfaces turned to superhydrophobicity and underwater superoleophilicity/superaerophilicity. Through this technique, the nozzle of a needle is transformed to possess superwettabilities. When the nozzles were used to release liquid and gas, the sizes of the dispensed water and oil droplets and air bubbles were dramatically reduced. Particularly, we demonstrate that the underwater superaerophobic nozzle could dispense air bubbles in nanoliter volume without the need of reducing the nozzle diameter. The liquid retention at the opening of the needle was also effectively prevented. Therefore, the reduced droplet/bubble size and retention allow us to achieve a dramatically enhanced volume accuracy and resolution when manipulation and transport of aqueous solutions and gases. The femtosecond laser-induced superwetting nozzles can be used in high-resolution liquid transport, inkjet printing, 3D printing, pipettes, medical devices, cell engineering, biological detection, microchemical reactor, and the cleaner of industrial gas emission.
关键词： underwater superoleophobicity,underwater superaerophobicity,superhydrophobicity,femtosecond laser,needle nozzle
更新于2025-09-10 09:29:36
-
In-water visual ship hull inspection using a hover-capable underwater vehicle with stereo vision
摘要： Underwater visual inspection is an important task for checking the structural integrity and biofouling of the ship hull surface to improve the operational safety and efficiency of ships and floating vessels. This paper describes the development of an autonomous in‐water visual inspection system and its application to visual hull inspection of a full‐scale ship. The developed system includes a hardware vehicle platform and software algorithms for autonomous operation of the vehicle. The algorithms for vehicle autonomy consist of the guidance, navigation, and control algorithms for real‐time and onboard operation of the vehicle around the hull surface. The environmental perception of the developed system is mainly based on optical camera images, and various computer vision and optimization algorithms are used for vision‐based navigation and visual mapping. In particular, a stereo camera is installed on the underwater vehicle to estimate instantaneous surface normal vectors, which enables high‐precision navigation and robust visual mapping, not only on flat areas but also over moderately curved hull surface areas. The development process of the vehicle platform and the implemented algorithms are described. The results of the field experiment with a full‐scale ship in a real sea environment are presented to demonstrate the feasibility and practical performance of the developed system.
关键词： computer vision,underwater robotics,autonomous underwater vehicles,underwater navigation,visual inspection
更新于2025-09-09 09:28:46