The finite-difference time-domain （FDTD） method is proposed for analyzing the surface acoustic wave （SAW） propagation in two-dimensional （2D） piezoelectric phononic crystals （PCs） at radio frequency （RF）, an...The finite-difference time-domain （FDTD） method is proposed for analyzing the surface acoustic wave （SAW） propagation in two-dimensional （2D） piezoelectric phononic crystals （PCs） at radio frequency （RF）, and also experiments are established to demonstrate its analysis result of the PCs＇ band gaps. The FDTD method takes the piezoelectric effect of PCs into account, in which periodic boundary conditions are used to decrease memory/time consumption and the perfectly matched layer boundary conditions are adopted as the SAW absorbers to attenuate artificial reflections. Two SAW delay lines are established with/without piezoelectric PCs located between interdigital transducers. By removing several echoes with window gating function in time domain, delay lines transmission function is achieved. The PCs＇ transmission functions and band gaps are obtained by comparing them in these two delay lines. When Aluminum/128°YX-LiNbO3 is adopted as scatter and substrate material, the PCs＇ band gap is calculated by this FDTD method and COMSOL respectively. Results show that computational results of FDTD agree well with experimental results and are better than that of COMSOL.展开更多
Taking a block of an oilfield as the engineering background, by analyzing the relationship between lithology and electrical properties, physical properties and electrical properties, as well as the relationship betwee...Taking a block of an oilfield as the engineering background, by analyzing the relationship between lithology and electrical properties, physical properties and electrical properties, as well as the relationship between oil-producing properties and electrical properties, four diagrams, namely, well right diagram, spontaneous potential curve, natural gamma curve, microelectrode curve, acoustic time difference curve, 4.0 m apparent resistance curve (2.5 m) and induction curve, were obtained, and porosity data (acoustic time difference) and induction curve were determined. It is suggested to establish an empirical formula by using acoustic time difference curve and tank porosity analysis, and further determine the limit thickness as fine sandstone. Through comprehensive analysis of the lower limit thickness of effective lithology and the lower limit electrical property of oil-bearing category, it is concluded that the oil-bearing category is oil-bearing category. The effective thickness is determined by using geological records of adjacent wells, laboratory analysis and oil testing (production) data and interlayer is subtracted, which provides an important reference link for determining the thickness of such tanks.展开更多
基金supported by the National Natural Science Foundation of China(11174318,11304346,61106081)Chinese Postdoctoral Science Foundation(2011M501204,2013T60718)+2 种基金National High Technology Research and Development Program(863 Program)(SS2013AA041103)Beijing Municipal Science and Technology Commission Project(Z141100003814016)the Fundamental Research Funds for the Central Universities(HUST:2013QN038)
文摘The finite-difference time-domain （FDTD） method is proposed for analyzing the surface acoustic wave （SAW） propagation in two-dimensional （2D） piezoelectric phononic crystals （PCs） at radio frequency （RF）, and also experiments are established to demonstrate its analysis result of the PCs＇ band gaps. The FDTD method takes the piezoelectric effect of PCs into account, in which periodic boundary conditions are used to decrease memory/time consumption and the perfectly matched layer boundary conditions are adopted as the SAW absorbers to attenuate artificial reflections. Two SAW delay lines are established with/without piezoelectric PCs located between interdigital transducers. By removing several echoes with window gating function in time domain, delay lines transmission function is achieved. The PCs＇ transmission functions and band gaps are obtained by comparing them in these two delay lines. When Aluminum/128°YX-LiNbO3 is adopted as scatter and substrate material, the PCs＇ band gap is calculated by this FDTD method and COMSOL respectively. Results show that computational results of FDTD agree well with experimental results and are better than that of COMSOL.
文摘Taking a block of an oilfield as the engineering background, by analyzing the relationship between lithology and electrical properties, physical properties and electrical properties, as well as the relationship between oil-producing properties and electrical properties, four diagrams, namely, well right diagram, spontaneous potential curve, natural gamma curve, microelectrode curve, acoustic time difference curve, 4.0 m apparent resistance curve (2.5 m) and induction curve, were obtained, and porosity data (acoustic time difference) and induction curve were determined. It is suggested to establish an empirical formula by using acoustic time difference curve and tank porosity analysis, and further determine the limit thickness as fine sandstone. Through comprehensive analysis of the lower limit thickness of effective lithology and the lower limit electrical property of oil-bearing category, it is concluded that the oil-bearing category is oil-bearing category. The effective thickness is determined by using geological records of adjacent wells, laboratory analysis and oil testing (production) data and interlayer is subtracted, which provides an important reference link for determining the thickness of such tanks.
