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In order to solve the problem of efficient trajectory control of centimeter-scale robots with small size, a small jellyfish robot (JRT) is designed and developed, which is composed of an air chamber, a center of gravity adjustment device and a jellyfish-inspired thruster with a size of only ⌀6.8 cm × 5.3 cm. Its trajectory can be effectively controlled underwater through the coordination of the center of gravity adjustment device and jellyfish-inspired thruster. Underwater experiments verify the function of JRT swimming and hovering in the vertical direction, horizontal directional swimming, and horizontal ejection. By analyzing the force balance relationship and motion state data of JRT swimming in the vertical and horizontal directions, a trajectory control scheme is proposed. The speed of horizontal directional swimming can reach 1.7 cm/s, and the trajectory deviation is 0—3.4 cm, which shows that the JRT has a good trajectory control ability and is expected to be applied in underwater resource exploration, environmental monitoring, and other fields.

The muroidCricetopsMatthew and Granger, 1923 commonly occurred in the Oligocene terrestrial deposits in central and northern Asia. Here we report the first record ofCricetopsin the southern part of Asia. Isolated rodent molars named as a new species,Cricetops austersp. nov., were discovered from the early Oligocene sediments at the Lijiawa locality in Yunnan Province in southwestern China. Compared to previously knownCricetops,C. austeris smaller thanCricetops dormitorMatthew and Granger, 1923 andCricetops aeneusShevyreva, 1965, but larger thanCricetops minorWang, 1987. The cusps ofC. austerare less conical. The ridges and crests are longer, higher and thicker. Relatively long and high crests, ridges and arms extending from the main cusps in the new species make those cusps more crescent in appearance than inC. dormitor,C. aeneusandC. minor.C. austeris a rare species in the Lijiawa mammalian fauna. Well-developed shearing tooth crests and ridges ofC. austerprobably suggest a different diet from theCricetopsfrom the northern part of Asia. [ABSTRACT FROM PUBLISHER]