KEYWORDS: Clocks, Global Positioning System, Data acquisition, Calibration, Crystals, Control systems, Complex systems, Data processing, Imaging systems, Temperature metrology
When a large-scale seismic data acquisition and recording system is applied for long-term continuous data acquisition, it is often affected by factors such as temperature, excitation level and acceleration changes perceived by the crystal unit. Since there is no accumulative error for GPS time and the short-term stability of GPS local clock is outstanding, this paper designs a scheme that uses GPS clock as standard clock to time FCU(Field Control Unit), then uses GPS highprecision second pulse, and uses least square method and bisection method to calibrate local clock frequency. The test results show that the clock synchronization error of this scheme is less than 800ns, which has the advantages of low cost and good reliability, and can meet the needs of clock synchronization for long-time continuous data acquisition of largescale seismic acquisition and recording system.
In order to fuse highly conflicting evidence effectively, a novel combination method based on weighted distance of
evidence is proposed by taking the ideas of Murphy’s averaging method and Deng’s weighted averaging method. Firstly,
the essentiality of each element in the frame of discernment is given by Murphy’s idea. Secondly, the weighted
averaging distance between any two bodies of evidence(BOEs) is calculated under the modified City Block distance
norm, further the support degree of each evidence supported by other evidences can be obtained. Thirdly, the normalized
total support degree of each evidence is considered as the weights of BOEs, and a new weighted averaging BOE will be
gained. Finally, the information fusion process can be realized by using the Dempster’s rule of combination. Simulation
results show that the proposed method can deal with the highly conflicting evidence with better performance of
convergence, and it also can recognize the target more effectively and fleetly.
Ship detection based on video is important in the application of surveillance and marine safety, the detection results
of tradition methods, such as background subtraction, have much noise because of background noise such as ocean
wave. In this paper we present a simple but efficient method for ship detection, It is based on the edge information of
single image and movement information of multi images. Firstly, detect those movement pixels used the background
subtraction to the video image, and the distance transformation is operation on the difference images; Secondly, we
detect the edge of video image used Canny detector , and morphological operation on the edge image, lastly,
eliminate the movement pixels if their distance transformation value is bigger than the threshold. The experimental
results demonstrate that is efficient to eliminate the background noise and detect the real target.
Aiming at the deficiency of gray relational analysis method in radar emitter recognition, an improved gray relational
analysis method is proposed in this paper. The new method can deal with the situation that the descriptions of some
characteristic parameters in database are intervals by improving the calculation process of D-value sequence. At the
same time, in order to confirm the weight coefficients of characteristic parameters more effectively, the entropy value
analysis method is improved. Simulation results show that the new method has a better recognition rate; moreover, it has
a stronger processing ability when some reconnaissance characteristic parameters are default.
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