Temporally Deconflicted Path Planning for Multiple Marine Vehicles

Over the past few years, growing interests and demands have been witnessed in the development of Automatic Surface Vehicle(ASV) operation, especially in controlling fleet of vehicles to perform complex missions. Basing on the path planning algorithm which generates single path between two points, guiding multiple vehicles to their own ends while avoiding possible inter-vehicle collisions brings more challenges and thus requires more versatility. These kind of algorithms need to first consider goal related influencing factors like environmental constraints and vehicle dynamics. In multiple vessels scenario there would also be some specific requirements like path deconfliction in time or space, final arrival synchronizing or avoiding inter-vehicle communication constraints. Further, measurements and optimized solutions will also be needed, such as energy and length minimized path. The multiple path planning algorithm is developed basing on single path generation optimization algorithm using Bézier curves. For arbitrary number of vehicles, path planning algorithm capable of leading each vehicle to its assigned target is proposed. For vehicle motion at the intersection points, temporal deconfliction is an important issue to be taken care of. To avoid inter-vehicle collisions, first the motion along the whole path and its corresponding speed need to be defined. After assigning the speed, time profile of each point could be obtained, as well as the distance between two vehicles at a certain time instant. Further, for the crossing point which would be shown geometrically on the path, temporal deconfliction are formulated as constraints in the framework of optimization problem, as well as vehicle dynamic like velocity and acceleration restrictions, in order to satisfy the physical limitations and avoid problems in path following. Cost function is chosen to penalize the exceeding operation time, thus a feasible solution with shortest time and smooth speeding process could be obtained. And despite of the different length of path, they would finally arrive simultaneously. Finally, a series of simulation results are presented in the last chapter, showing the feasibility and efficiency of the algorithm in multiple path planning. By presenting simulation scenarios with different conditions like path number, random obstacles and velocity limitations, the versatility of the proposed algorithm could be shown as well. By this end, the conclusion could be made that paths for arbitrary number of vessels are temporally deconflicted with simultaneous arriving time. Some challenges so far still existing would be revealed through discussion, and indicate some crucial points for the future work

Measuring the Optical Absorption Cross Sections of Au−Ag Nanocages and Au Nanorods by Photoacoustic Imaging

This paper presents a method for measuring the optical absorption cross sections (σ_a) of Au−Ag nanocages and Au nanorods. The method is based on photoacoustic (PA) imaging, where the detected signal is directly proportional to the absorption coefficient (μ_a) of the nanostructure. For each type of nanostructure, we first obtained μ_a from the PA signal by benchmarking against a linear calibration curve (PA signal versus μ_a) derived from a set of methylene blue solutions with different concentrations. We then calculated σ_a by dividing the μ_a by the corresponding concentration of the Au nanostructure. Additionally, we obtained the extinction cross section (σ_e, sum of absorption and scattering) from the extinction spectrum recorded using a conventional UV−vis−NIR spectrometer. From the measurements of σ_a and σ_e, we were able to easily derive both the absorption and scattering cross sections for each type of gold nanostructure. The ratios of absorption to extinction obtained from experimental and theoretical approaches agreed well, demonstrating the potential use of this method in determining the optical absorption and scattering properties of gold nanostructures and other types of nanomaterials

Photoacoustic quantification of the optical absorption cross-sections of gold nanostructures

This study demonstrates a method for measuring the optical absorption cross-sections (σ_a) of Au-Ag nanocages and Au nanorods using photoacoustic (PA) sensing. PA signals are directly proportional to the absorption coefficient (μ_a) of the nanostructure. For each type of nanostructure, we first obtained μa from the PA signal by benchmarking against a linear calibration curve (PA signal vs. μ_a) derived from a set of methylene blue solutions with different concentrations. We then calculated σ_a by dividing the μ_a by the corresponding concentration of the Au nanostructure. Additionally, we obtained the extinction cross-section (σ_e, sum of absorption and scattering cross-sections) from the extinction spectrum recorded using a conventional UV-vis-NIR spectrometer. From the measurements of σ_a and σ_e, we were able to easily derive both the absorption and scattering cross-sections for each type of gold nanostructure. This method can potentially provide the optical absorption and scattering properties of gold nanostructures and other types of nanomaterials

Correlation Analysis of Road Freight Transport and Economic Development in Shaanxi Province

Based on the data from 1987-2017 of the Statistical Yearbook of Shaanxi Province, this paper selects Shaanxi Road freight transportation evaluation indicators and economic development evaluation indicators, and uses the method of co-integration test and ADF unit root test to determine whether there is a long-term equilibrium relationship between the indicators. Through the establishment of VAR model and analysis, it demonstrates the impact of road freight transportation on economic development in Shaanxi Province. Based on the impulse impact between the road freight transportation and economic development in Shaanxi Province, the correlation between road freight transportation and economic development in Shaanxi Province is analyzed and studied to provide suggestions for the coordinated development of road freight transportation and economy in Shaanxi Province

Confucius’ Thoughts on Moral Education in China

Confucius was the greatest philosopher and educator in Chinese history. His words and thoughts were recorded in the book The Analects of Confucius by his disciples. This paper mainly introduces Confucius’ thoughts on moral education from three aspects: goal, main contents, and teaching methods. According to Confucius, cultivating a completely virtuous person (‘Junzi’) is the goal of moral education. The idea of benevolence (‘Ren’) is regarded as the core of Confucius’ moral thoughts and the idea of etiquette (‘Li’) is the external form of ‘Ren’. Both of them are main contents of Confucius’ moral education. There are several teaching methods in Confucius’ moral education, such as self-cultivating, individual instruction, enlightening and practice, which are described in this paper. Furthermore, some inspirations which are obtained from Confucius’ moral educational thoughts provide significant reference for contemporary education in China.

USP21 deubiquitylates Nanog to regulate protein stability and stem cell pluripotency

The homeobox transcription factor Nanog has a vital role in maintaining pluripotency and self-renewal of embryonic stem cells (ESCs). Stabilization of Nanog proteins is essential for ESCs. The ubiquitin–proteasome pathway mediated by E3 ubiquitin ligases and deubiquitylases is one of the key ways to regulate protein levels and functions. Although ubiquitylation of Nanog catalyzed by the ligase FBXW8 has been demonstrated, the deubiquitylase that maintains the protein levels of Nanog in ESCs yet to be defined. In this study, we identify the ubiquitin-specific peptidase 21 (USP21) as a deubiquitylase for Nanog, but not for Oct4 or Sox2. USP21 interacts with Nanog protein in ESCs in vivo and in vitro. The C-terminal USP domain of USP21 and the C-domain of Nanog are responsible for this interaction. USP21 deubiquitylates the K48-type linkage of the ubiquitin chain of Nanog, stabilizing Nanog. USP21-mediated Nanog stabilization is enhanced in mouse ESCs and this stabilization is required to maintain the pluripotential state of the ESCs. Depletion of USP21 in mouse ESCs leads to Nanog degradation and ESC differentiation. Overall, our results demonstrate that USP21 maintains the stemness of mouse ESCs through deubiquitylating and stabilizing Nanog