The obstacle avoidance in path planning, a hot topic in mobile robot control, has been extensively investigated. The existing ant colony algorithms, however, remain as drawbacks including failing to cope with narrow aisles in working areas, large amount of calculation, etc. To address above technical issues, an improved ant colony algorithm is proposed for path planning. In this paper, a new weighted adjacency matrix is presented to determine the walking direction and the narrow aisles therefore are avoided by redesigning the walking rules. Also, the best ant and the worst ant are introduced for the adjustment of pheromone to facilitate the searching process. The proposed algorithm guarantees that robots are able to find a satisfying path in the presence of narrow aisles. The simulation results show the effectiveness of the proposed algorithm.
Graphene oxide (GO) was modified by polyphenylvinylsiloxane (PPVS) through π-π conjugation interaction. The modified GO/PMMA nanocomposites were prepared via in situ bulk polymerization. The modification of GO was characterized by using Fourier transformed infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Thermal conductivity, thermal stability and mechanical properties of PMMA and its composites were investigated by using TG, heat conduction analysis, and three-point bending strength test, respectively. The results showed that PPVS modified GO was prepared through non-covalent interaction, and composites with non-convalent phase interfaces were also obtained. With the addition of GO-PPVS, the three-point bending strength of GO-PPVS/PMMA increased to about 68 MPa. GO wrapped by PPVS could not form thermal conducting networks at the percolation thresholds. The increasing amount of PPVS prevented the formation of thermal conduction network, and decreased the thermal conductivity of the composites. The thermal stability of the composites was influenced by three main factors, and the total effect of the three factors on thermal stability illustrated a negative trend.
Sr, Ca and Fe doped cathode materials Ln0.7Sr0.2Ca0.1Co0.7Fe0.3O2.85 (LnSCCF, Ln=La, Pr and Nd; abbreviated as L-72173, P-72173 and N-72173) were synthesized by microwave sintering (MWS) techniques. The formation process, phase structure and composition were characterized using TG/DTA, XRD and EDS. The thermal expansion behavior of the samples was analyzed in the range of 20-950 °C by thermal dilatometer. The electrical conductivity of the samples was measured with DC four-terminal method from 25 to 900 °C. The X-ray diffraction shows that the samples exhibit a single phase with rhombohedral or cubic perovskite structure after sintered at 1200 °C for 20 min. The electrical conductivity of the samples increases with temperature up to a maximum, and then decreases gradually at higher temperature owing to the creation of oxygen vacancies. The small polaron hopping is regarded as the conducting mechanism (T 550 °C). L-72173 has higher mixed conductivity ( >300 S·cm-1) in 550-800 °C. The average TECs of L-72173, P-72173 and N-72173 are 1.389× 10-5 K-1, 1.417 × 10-5 K-1 and 1.416 × 10-5 K-1 in the range of 25-800 °C, respectively. They are thermally matched to the GDC better than the YSZ and SDC.
The conventional method to measure the tracking accuracy of antenna is based on the boresight tower. But the accuracy of this method is not very high because the result is easy to be disturbed by reflecting electromagnetic wave from ground, surrounding buildings and terrains under low elevation in measuring. And a boresight tower and a lot of corresponding equipments are needed in this method. It costs both time and money. This paper presents a new method of using precise geostationary satellite orbit to measure the tracking accuracy. It is easy to operate. Moreover, the accuracy of this method is higher than the conventional one. The feasibility of the new method is validated in comparison with the conventional one, so it can be used in the construction and maintenance of ground stations.
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