Kinematic Features of a Bow Echo in Southern China Observed with Doppler Radar

A bow echo is a type of mesoscale convective phenomenon that often induces extreme weather and appears with strong reflectivity on radar images. A strong bow echo that developed from a supercell was observed over Foshan City in southern China on 17 April 2011. The intense gusty winds and showers caused huge losses of property and severely affected human lives. This paper presents an analysis of this strong meso- n-scale convective system based on Doppler radar observations. The isolated bow echo exhibited a horizontal scale of about 80 km in terms of reflectivity above 40 dBZ, and a life span of 8 hours. The system originated from the merging of a couple of weakly organized cells in a shear line, and developed into an arch shape as it moved through the shear zone. Sufficient surface moisture supply ensured the convective instability and development of the bow echo. The low-altitude winds retrieved from single Doppler radar observations showed an obvious rear-inflow jet along the notch area. Different from the conventional definition, no book- end anticyclone was observed throughout the life cycle. Very strong slantwise updrafts and downdrafts were recognizable from the retrieved winds, even though the spatial scale of the bow echo was small. Strong winds and induced damage on the surface are considered to have been caused by the mid-level rear-inflow jet and intense convective downdrafts.

Hydrographic features of the plume front in the Hangzhou Bay

A description is given of the distribution , spacial and temporal variation , mixing and transportation processes about the plume front in the Hangzhou Bay. This front is performed as a group of interfaces among, the water masses situated in the bay. A discussion is also given of the circulation feature in the frontal zone ence of the front.

Research on Piezoelectric Driving Microminiature Three-Legged Crawling Robot

Micro-robots have the characteristics of small size,light weight and flexible movement.To design a micro three-legged crawling robot with multiple motion directions,a novel driving scheme based on the inverse piezoelectric effect of piezoelectric ceramics was proposed.The three legs of the robot were equipped with piezoelectric bimorphs as drivers,respectively.The motion principles were analyzed and the overall force analysis was carried out with the theoretical mechanics method.The natural frequency,mode shape and amplitude were analyzed with simulation software COMSOL Multiphysics,the optimal size was determined through parametric analysis,and then the micro three-legged crawling robot was manufactured.The effects of different driving voltages,different driving frequencies,different motion bases and different loads on the motion speed of the robot were tested.It is shown that the maximum speed of single-leg driving was 35.41 cm/s,the switching ability between different motion directions was measured,and the movements in six different directions were achieved.It is demonstrated the feasibility of multi-directional motion of the structure.The research may provide a reference for the design and development of miniature piezoelectric three-legged crawling robots.