Gabor transform is very suitable for time-frequency analysis and good for filtering non-stationary signals. The threshold of the Gabor transform filter is a key factor for the filter’s effectiveness. A novel threshold based on initial highest inter-cluster distance probability (IH-ICDP) is described in this paper and it can make the filter more efficient. Some experiments have been carried out under several conditions to evaluate the new threshold’s characteristics. The experimental results show that Gabor transform filter with this proposed threshold works better than wavelet transform filter, especially when the signal’s SNR is very low. From the evaluation results, it is possible to consider that the threshold presented is optimal or nearly optimal.

With the development of production and technology, the devices of oil refining, chemical, fertilizer and others are progressing to the direction of high parameters (high pressure, high temperature). Pressure vessels must be open, which will made the stress concentration problems more serious, and traditional design methods derived from empirically formula fails to meet the actual demand. In this paper, a theoretical result is calculated with a simplified model of the opening holes in cylindrical shell, verified by a group of solutions got by the ANSYS simulation. And it turns out that the result is rather satisfactory.

Sediment on the bottom of borehole forms a major part which is often responsible for reducing the bearing capacity of pile. The normal method of measuring sediment thickness by ultrasonic signal is to measure the sound time and intensity of echo signal. This paper presents a novel measurement method by estimating the ultrasonic channel. Wiener filter is applied to estimate the ultrasonic optimal channel under minimum mean square error criteria. Experiments of estimating channel based on Wiener filter have been conducted with given signals and actual ultrasonic detection echo. The influence of noise in the signal has been discussed. The results show that, during signals high SNR, the estimated channel is corresponding to the sharp changes in the actual signal and can be used to determine the sediment thickness.

In the paper, the three-phase ac motor is used as the controlled station and the FPGA device EP1C3T144C8 is adopted as the control core. Aiming at the flexibility of the variable frequency system based on SPWM, the DDS technique is introduced. The process of speed adjustment is conducted by AC motor by the three-phase supply with tunable frequency generated by inverter switch device based on SPWM signal. With rational structure and simplified design, this project can generate stable SPWM signal, high frequency resolution and fast switching speed.

As a new type of vertical take-off and landing unmanned aerial vehicles, four-rotor unmanned aircraft has strong load capacity, simple structure, flexible operation Characteristics, so it is the preferred method of execution the air, and is widely used in military and civil field. Based on four-rotor aircraft structure and movement theory, this paper designs the aircaft control system based on ARM. Based on upper machine, the design of PID control algorithm was tested in this paper. From the results, the stability of the controller is good, and its speed control is superior to the single closed-loop.