Navigation technology is one of the most important challenges in the applications of autonomous underwater vehicles (AUVs) which navigate in the complex undersea environment. The ability of localizing a robot and accurately mapping its surroundings simultaneously, namely the simultaneous localization and mapping (SLAM) problem, is a key prerequisite of truly autonomous robots. In this paper, a modified-FastSLAM algorithm is proposed and used in the navigation for our C-Ranger research platform, an open-frame AUV. A mechanical scanning imaging sonar is chosen as the active sensor for the AUV. The modified-FastSLAM implements the update relying on the on-board sensors of C-Ranger. On the other hand, the algorithm employs the data association which combines the single particle maximum likelihood method with modified negative evidence method, and uses the rank-based resampling to overcome the particle depletion problem. In order to verify the feasibility of the proposed methods, both simulation experiments and sea trials for C-Ranger are conducted. The experimental results show the modified-FastSLAM employed for the navigation of the C-Ranger AUV is much more effective and accurate compared with the traditional methods.

Different types of soil samples from a typical farmland in northern China were collected and evaluated for the presence of the pesticides and antibiotics.

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The negative photoconductivity (NPC) effect originating from the surface shell layer has been considered as an efficient approach to improve the performance of optoelectronic nanodevices. However, a scientific design and precise growth of NPC-effect-caused shell during nanowire (NW) growth process for achieving high-performance photodetectors are still lacking. In this work, GeS NWs with a controlled sulfur-rich shell, diameter, and length are successfully prepared by a simple chemical vapor deposition method. As checked by transmission electron microscopy, the thickness of the sulfur-rich shell ranges from 10.5 ± 1.5 to 13.4 ± 2.5 nm by controlling the NW growth time. The composition of the sulfur-rich shell is studied by X-ray photoelectron spectroscopy, showing the decrease of S in the GeS x shell from the surface to core. When configured into the well-known phototransistor, a featured NPC effect is observed, benefiting the high-performance photodetector with high responsivity of 105 A·W–1 and detectivity of 1012 Jones for λ = 405 nm with ultralow intensity of 0.04 mW·cm–2. However, the thicker-shell NW phototransistor shows an unstable photodetector behavior with smaller negative photocurrent because of more hole-trapping states in the thicker shell. All results suggest a careful design and controlled growth of an NPC-effect-caused shell for future optoelectronic applications.