Abstract: A piezoelectric sensor is provided. The piezoelectric sensor comprises a first base, a first conductive layer adjacent to the first base, a second base, a second conductive layer adjacent to the second base; and a first structure between the first conductive layer and the second conductive layer. The first structure comprises a first layer with a first carbon-based material and a plurality of second structures with piezoelectricity. Each of the plurality of second structures comprises a second layer with a second carbon-based material and a third layer adjacent to the second layer. The third layer comprises a material of two-dimensional crystals of unconventional stoichiometries such as Na2Cl crystals.

Abstract: Disclosed is a method for monitoring vehicle overload based on gravity anomaly, which includes the following steps of: setting a plurality of measuring positions on a single lane, arranging a gravimeter to acquire gravity anomaly values caused by a vehicle when the middle position along the length direction of the vehicle reaching each measuring position, using a monitoring camera to judge the category of the vehicle, acquire three geometric dimensions of the vehicle, and determine the position of the vehicle. The vehicle is simplified as a cuboid, and the mass density distribution is simplified as a piecewise constant function along the length direction of the vehicle. Calculating values of the piecewise constant function according to the gravity anomaly values, calculating a total weight of the vehicle according to the mass density distribution, comparing the total weight with the weight limit of the vehicle to judge whether the vehicle is overloaded. (FIG.