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  • A Hybrid Method for Inland Ship Recognition Using Marine Radar and Closed-Circuit Television

    分类: 交通运输工程 >> 水路运输 提交时间: 2024-03-28

    摘要: Vessel recognition plays important role in ensuring navigation safety. However, existing methods are mainly based on a single sensor, such as automatic identification system (AIS), marine radar, closed-circuit television (CCTV), etc. To this end, this paper proposes a coarse-to-fine recognition method by fusing CCTV and marine radar, called multi-scale matching vessel recognition (MSM-VR). This method first proposes a novel calibration method that does not use any additional calibration target. The calibration is transformed to solve an N point registration model. Furthermore, marine radar image is used for coarse detection. A region of interest (ROI) area is computed for coarse detection results. Lastly, we design a novel convolutional neural network (CNN) called VesNet and transform the recognition into feature extraction. The VesNet is used to extract the vessel features. As a result, the MVM-VR method has been validated by using actual datasets collected along different waterways such as Nanjing waterway and Wuhan waterway, China, covering different times and weather conditions. Experimental results show that the MSM-VR method can adapt to different times, different weather conditions, and different waterways with good detection stability. The recognition accuracy is no less than 96%. Compared to other methods, the proposed method has high accuracy and great robustness.

  • Systematic evaluation of pulsed laser parameters effect on temperature distribution in dissimilar laser welding: A numerical simulation and artificial neural network

    分类: 机械工程 >> 机械制造工艺与设备 提交时间: 2024-03-28

    摘要: The heat transfer mechanism andtemperature distributioninlaser weldingapplications have a great impact on the quality of the weld bead geometry, mechanical properties and the resultant microstructure characterizations of the welding process. In this study, the effects of pulsedlaser weldingparameters including the frequency and pulse width on the melt velocity field andtemperature distributionin dissimilarlaser weldingof stainless steel 420 (S.S 420) and stainless steel 304 (S.S 304) was investigated. A comprehensive comparison was conducted through the numerical simulation and artificial neural network (ANN). The results of numerical simulation indicated thatbuoyancy forceandMarangonistress are the most important factors in the formation of the flow of liquid metal. Also, increasing the pulse width from 8 to 12ms due to increasing the pulse energy, the temperature in the center of the melt pool increased about 250°C. This leads to increasing the convective heat transfer in the molten pool and heat affected zone (HAZ). The temperature difference at a distance of 1mm from the beam center at both metals at a frequency of 15 and 20Hz is bout 58 and 75°C, respectively. Furthermore, reducing the frequency to 5Hz, due to diminishment of thermal energy absorption time, has clearly decreased the weld penetration depth in the workpiece. According to the ANN results, increasing both pulse duration and frequency has the significant effect on increasing melting ratio from 0.4 to 0.8 compared to the other input parameters. The ANN results confirmed that under the same input conditions, because of the differences in thermal conductivity coefficient, absorption coefficient and melting point of the two pieces, S.S 304 has experienced higher temperatures about 10% more than S.S 420. Also, among the 13 back propagation learning algorithms, the Bayesian regularization algorithm had the best performance. Among the number of different neurons in the hidden layer, comparison was performed to prevent network overfitting. The maximum relative error of network output data and target data for S.S 304 and S.S 420 temperatures and melting ratio were 7.297, 10.16 and 11.33%, respectively.

  • Renewable Energy Storage and Sustainable Design of Hybrid Energy Powered Ships: A Case Study

    分类: 能源科学 >> 能源(综合) 提交时间: 2024-03-28

    摘要: With rapidly increasing consumption of energy, shipping industry has imposed a huge burden on the marine environment. It is a general trend to increase the use of renewable energy on ships to improve the ship sustainability. This article summarized the current development and application of solar energy, wind energy and fuel cell in ship power systems. Furthermore, in order to investigate the advantages of sustainable design for the ships, for the first time, a hybrid PV, wind and fuel cell energy system was established for an oil tanker, and the economic and environmental analyses of the hybrid system were performed. The analysis results demonstrate that the optimal hybrid energy system can reduce 151,467kg emission of CO2 and provide 2.92% electricity for the ship gird per year.

  • A new multi-sensor fusion approach for integrated ship motion perception in inland waterways

    分类: 交通运输工程 >> 水路运输 提交时间: 2024-03-31

    摘要: The ship motion perception approaches mainly use maritime radar, Automatic Identification System (AIS) and cameras. However, using either of these approaches alone may result in information inconsistency and insufficient data accuracy. Therefore, a multi-sensor fusion perception system is proposed in this study to monitor ship motion in inland waterways. Firstly, a hardware platform of multi-sensor fusion ship motion perception system composed of maritime radar, AIS, cameras and other accessories is constructed. Secondly, by utilizing the target detection and tracking algorithms, track association algorithms, the ship motion data collected from the three sensors are integrated. Finally, the performance of the ship motion perception system is verified by field experiments in day and night. The experimental results indicate that the integrated ship motion perception system with multiple sensors is able to improve the information consistency and data accuracy of ship motion apparently in inland waterway compared to other perception systems.

  • Machine learning calculation model for hydrodynamic lubrication characteristics of a miter gate bottom pivot

    分类: 机械工程 >> 机械设计 提交时间: 2024-03-31

    摘要: The bottom pivot is a vital support device in the miter gate but often subject to poor lubrication and wear failures. Calculating thehydrodynamic lubricationcharacteristics of the bottom pivot is a complex three-dimensional (3D) problem, and most of existing models adopt simplified assumptions to reduce the calculation difficulty. To solve this issue, this work develops a 3D model to calculate thehydrodynamic lubricationcharacteristics of the miter gate bottom pivot. Thefinite difference methodis used to solve theoil film thicknessand pressure distribution based on the spherical coordinatesReynolds equation. The component forces in three directions are calculated from the pressure distribution and compared with the theoretical values to generate the calculation difference. Then, thegenetic algorithm(GA) is used to minimize the difference to determine the optimal initial parameters for the 3D model. The analysis results show that the calculation accuracy can be significantly improved by using the optimal initial model parameters. When our initial pressure is 5.64MPa, the results meet the engineering accuracy requirements.

  • A nonlinear African vulture optimization algorithm combining Henon chaotic mapping theory and reverse learning competition strategy

    分类: 工程与技术科学 >> 工程通用技术 提交时间: 2024-03-28

    摘要: As a new intelligentoptimization algorithm, the African vulturesoptimization algorithm(AVOA) has been widely used in various fields today. However, when solving complex multimodal problems, the AVOA still has some shortcomings, such as low searching accuracy, deficiency on the search capability and tendency to fall into local optimum. In order to alleviate the main shortcomings of the AVOA, a nonlinear African vulture optimization algorithm combining Henon chaotic mapping theory and reverse learning competition strategy (HWEAVOA) is proposed. Firstly, the Henon chaotic mapping theory and elite population strategy are proposed to improve the randomness and diversity of the vulture’s initial population; Furthermore, the nonlinear adaptive incremental inertial weight factor is introduced in the location update phase to rationally balance the exploration and exploitation abilities, and avoid individual falling into a local optimum; The reverse learning competition strategy is designed to expand the discovery fields for the optimal solution and strengthen the ability to jump out of thelocal optimal solution. HWEAVOA and other advanced comparison algorithms are used to solve classical and CEC2022 test functions. Compared with other algorithms, the convergence curves of the HWEAVOA drop faster and the line bodies are smoother. These experimental results show the proposed HWEAVOA is ranked first in all test functions, which is superior to the comparison algorithms in convergence speed, optimization ability, and solution stability. Meanwhile, HWEAVOA has reached the general level in thealgorithm complexity, and its overall performance is competitive in theswarm intelligence algorithms.

  • Effect of microchannel wall dimensions and temperature on ethylene glycol fluid’s thermal performance in two-dimensional microchannels using molecular dynamics simulation

    分类: 机械工程 >> 机械工程其他学科 提交时间: 2024-03-28

    摘要: Increasing the transfer (HT) coefficient used in thermal industries is very important. Various methods are used to improve the efficiency of thermal heat HT so that maximum HT takes place in a smaller space. Ethylene glycol (EG) is generally used as an agent for convective HT. EG obtains energy from a hot source and discharges it to the required location. At present, the most consumption of EG is to produce engine cooling fluid. In the upcoming research, the TB of EG fluid in two-dimensional microchannels (MCs) has been investigated using molecular dynamics (MD) simulations, and the effect of variables such as MC dimensions and MC wall temperature (Temp) on the TB of the simulated fluid has been investigated. The results revealed that by increasing the Temp difference of the MC wall from 10 to 50 K, the maximum temperature (Max-Temp) and velocity (Max-Vel) of the target sample increased to 640.94 K and 0.024 Å/ps. It can be concluded that the increase in the cross-sectional area and the wall Temp difference leads to an increase in the HT rate in the MC.