Autonomous planning of navigation trajectory is a key research element of USV and a basic condition for safe and autonomous navigation. In this paper, an autonomous planning collision avoidance control algorithm for USV is introduced. TFMS is used to trajectory planning and dynamic window method for real-time collision avoidance, a hybrid planning algorithm of dynamic path planning algorithm and parallel planning of autonomous collision avoidance control algorithm is built to achieve autonomous navigation control of USV. The setting method of local target points has been improved to shorten the running time of the control system. The validation was carried out in different static and dynamic environments. A realistic collision avoidance environment model is established by extracting the environmental data from the port map of Dalian port. The result demonstrates that the method is effective in controlling the USV to sail safely and quickly in complex real scenarios with various dynamic impediments.
Support vector machine (SVM) has been widely applied in the classification of remotely sensed image. How to reduce support vector number in SVM classifier so as to reduce classification time still an important open problem, especially in the case of mass data. To obtain fast classifier with high accuracy, an active learning schema is proposed in the SVM based image classification. Experimental results with synthetic data and multispectral remotely sensed images show that, compare with the SVM classifiers trained with whole training sample set in a time, the SVM classifiers obtained by active selection of training instances have much fewer support vector and can always achieve relatively higher accuracy.
Natural killer (NK) cells directly lysis the virus-infected cells through rapidly releasing cytotoxic mediators and cytokines. The balance between inhibitory and activated receptors on the surface of NK cells, as well as the corresponding ligands expressed on target cells are involved in the regulation of the cytotoxic function of NK cells. NKG2A is one of the highly anticipated inhibitory receptors expressed on NK cells, which can inhibit the cytotoxicity of NK cells to autologous normal tissue cells through interacting with the ligand HLA-E. The studies have shown that HLA-E is overexpressed on virus-infected cells and forms a complex with peptides derived from viral proteins. The interaction of HLA-E and NKG2A can regulate the functions of NK cells, participateing the pathogenesis process of virus infectious diseases. This review outlines the characteristics of the molecular interaction between NKG2A and HLA-E, as well as the mechanisms of NKG2A-HLA-E axis in regulating NK cell responses.
Based on the theory of multi-body dynamic, a front Macpherson s us pension multibody model is established in this paper. Using design of experiment s, a sensitivity analysis method of the kinematic response of Macpherson Suspens ion is developed. The experimental design techniques enable us to gain an unders tanding of the relationships between a set of system responses and a set of fact ors and to isolate those factors which are highly important from those which are negligible. Through the optimum design, the optimized suspension is obtained.
Global navigation satellite system reflectometry technology (GNSS-R) is rarely used for river flow velocity inversion, and in particular, there is currently no research using the BeiDou Navigation Satellite System reflectometry technology (BDS-R) for river flow velocity inversion. In this paper, a carrier phase observation of river flow velocity inversion model is proposed. The interference phase is the integral of the Doppler frequency. The raw intermediate frequency (IF) data sets are processed through an open-loop method to obtain the Doppler frequency observation generated by river flow and then realize velocity inversion. The shore-based river current measurement was conducted on the south bank of Dashengguan Yangtze River in Nanjing city, Jiangsu Province, for nearly two hours on 22 April 2021. After realizing the inversion of river flow velocity in GPS L1, the combined inversion of BDS B1I GEO satellite and IGSO satellite is realized for the first time, which demonstrates the feasibility of river flow velocity inversion using BDS reflected signals. Compared with the real river flow velocity, the GPS L1 PRN 4 (1st period) inversion precision reaches up to 0.028 m/s (mean absolute error, MAE) and 0.036 m/s (root mean square error, RMSE). In parallel, BDS GEO 2 inversion precision can reach 0.048 m/s (MAE) and 0.063 m/s (RMSE), and BDS IGSO 10 inversion precision is 0.061 m/s (MAE) and 0.073 m/s (RMSE). These results illustrate that satellite elevation change rate and distance between specular points and current meter may have a negative effect on the accuracy of river flow velocity inversion. Specular points obstructed by obstacles or too far from the velocity meter may introduce uncertain error in both MAE and RMSE. Neither the satellite elevation nor the signal strength has an obvious correlation with inversion precision, which is consistent with the theoretical principle.
We propose "StereoPasting," an efficient method for depth-consistent stereoscopic composition, in which a source 2D image is interactively blended into a target stereoscopic image. As we paint "disparity" on a 2D image, the disparity map of the selected region is gradually produced by edge-aware diffusion, and then blended with that of the target stereoscopic image. By considering constraints of the expected disparities and perspective scaling, the 2D object is warped to generate an image pair, which is then blended into the target image pair to get the composition result. The warping is formulated as an energy minimization, which could be solved in real time. We also present an interactive composition system, in which users can edit the disparity maps of 2D images by strokes, while viewing the composition results instantly. Experiments show that our method is intuitive and efficient for interactive stereoscopic composition. A lot of applications demonstrate the versatility of our method.
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