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A Simple Calculation Approach for the Second-Harmonic Sound Beam Generated by an Arbitrary Distribution Source 下载免费PDF全文
We present a simple calculation approach for the fundamental and second-harmonic sound beams with an arbitrary distribution source in the quasilinear approximation. The analysis is based on the assumption that the source function with an arbitrary geometry and distribution is expanded into the sum of a set of two-dimensional Gaussian functions. The two- and five-dimensional integral solutions for the fundamental and second-harmonic fields are, respectively, reduced in terms of Gaussian functions and simple one-dimensional integrals. The numerical evaluation of field distributions is then greatly simplified. 相似文献
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锥形声源的二次谐波声场分布 总被引:1,自引:0,他引:1
本文推导了锥形声源的非线性二次谐波声场分布。理论表明锥形源二次谐波声场沿径向呈Bessel函数分布,且与传播距离无关。另一个重要结论是这种声场的二次谐波束宽刚好为基波的1/2,而非一般情况下的$1 / \\sqrt{2}$倍,此外,我们指出了这种声束在非线性参量B/A成象或测量中潜在的应用价值. 相似文献
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用原子力显微镜研究了二棕榈酰磷脂酸(DPPA)双层LB膜的分子排列结构,发现DPPA双层膜的分子排列具有长程的位置和取向有序,为有序大方结构,同时,在DPPA双层膜的极性区磷酸基团间存在局域超分子结构。 相似文献
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Stable monolayers of electropolymerized poly-N-vinylcarbazole (EPVK) and arachidic acid(AA) are obtained on a subphase of alkaline Tl2O3 colloidal solutions. As revealed by the atomic force microscope, there is phase separation in the mixed LB monolayers. Transmission electron microscopic observations reveal that ordered arrays of composite Tl2O3/Epvk nanowires are formed in the mixed monolayers. Formation of the composite nanowire arrays is attributed to the ordered adsorption of Tl2O3 colloidal particles along the polycationic EPVK chains. The composite nanowire array is 3.2nm wide with a spacing of 2.7nm.The composite nanowire arrays can also be formed when pure EPVK is used. Composite LB multilayers of Tl2O3/EPVK nanowire arrays are prepared. The bilayer spacing is 5.54nm.The present study is of importance to the fabrication of inorganic semiconductor/functional polymer composite nanowires. 相似文献
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依托实体医院线下资源,基于运营商行业云平台和视频平台基础能力,构建平台资源弹性配置、按需扩容,应用功能按需扩充、快速迭代的新一代互联网医院平台.通过线上线下系统联动,实现诊前智能导诊与精准预约、诊中在线咨询与实时问诊、诊后智能慢病管理与院后随访的全流程在线医疗服务,最终优化医院服务流程和品质,提升优质医疗资源服务范围和... 相似文献
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We present a further analysis for the second-harmonic generation of Bessel beams in lossy media.The emphasis is put on the effect of absorption to the radial pattern of the second-harmonic beam.It is shown that within the absorption length of the second harmonic,the Bessel second-harmonic beam approaches limited diffraction in the radial direction and behaves as in the case of lossless media. 相似文献
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研制了一种结构简单、拆装方便的自积分电容分压器,用于测量强流电子加速器二极管输出电压。介绍了电容分压器的结构,计算了其电容量,并通过仿真的方法分析了前端电阻及其杂散参数对测量波形的影响,结果表明:当前端电阻杂散电容较大时,测量波形出现过冲现象;而前端电阻对地电容较大时,会影响测量波形的前沿。将电容分压器用于测量强流电子加速器二极管输出电压,并运用水电阻分压器对其进行了标定,所测得波形与电阻分压器基本一致,分压比为563 007,可以用于测量半高宽为100 ns的高压脉冲。 相似文献
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