This paper presents beat and random equivalent sampling techniques to solve the data acquisition of high frequency wideband period signal.

The design of the digital correlation algorithm can reduce the effect of beat-frequency device noise floor in this system on measurement accuracy.

A frequency standard comparison platform based on beat-frequency technique has been designed to evaluate the difference of performance between the periodic frequency measurement with counter and the digital beat-frequency signals processing with computer, the fundamental of measurement and realization of the two sets of systems are analyzed.

Analysis of the guarantee degree of irrigation water resources and its spatial difference in Northeast China;

Quantitative analysis on the spatial difference of agricultural development level in Gansu province;

Study on the spatial difference of soil characteristic and the method of its spatial interpolation;

Assessment on ecological security of spatial differences of east areas of Liaohe River based on GIS;

Analysis of the characteristics and spatial differences of urbanization quality of cities at prefecture level and above in China

Taking the point of view of per unit area yield of grain,per-capita share of grain and contribution degree of grain as breakthrough point,this paper researched the spatial differences of grain production.