The finite difference beam propagation method ( fd - bpm ) can simulate the performance of the waveguide accurately . single mode rid waveguide structure parameters are derived by variational - effective index method ; fd - bpm and its transparent boundary condition ( tbc ) are concerned , and then the eim used to transfer a 3d waveguide to 2d waveguide is analyzed ; finally we summarize the characteristic of the y branch 本文先利用变分有效折射率法推导出满足单模传输的脊形波导结构参数;接着介绍了有限差分束传播法及求解的透明边界条件,同时分析了将三维结构转化为二维结构的有效折射率法,最后对y分支的特性进行了模拟。
With the trend that cdma will be the dominant multi - access scheme in the new generation of wireless communication , how to apply spatial processing in cdma system has been becoming the emphasis of research in smart antenna . a proper method is space - time processing due to the space - time structure of wireless channel . beamforming can be combined with rake to form 2d rake receiver , which can effectively weaken the enhancement of mai in conventional rake receiver . however a more effective method is to use space - time filtering . these two scheme will be discussed and the structure and realization will be presented 码分多址技术逐渐成为新一代通信系统的主流多址技术,如何在码分多址系统中引入空域处理以改善系统性能是当前智能天线技术研究的重点之一.考虑到无线信道的时空二维结构特征,一种合理的实现方式是采用时空处理方法,将波束形成技术与时域分集技术相结合;另一种更有效的方法是在接收端采用时空二维联合处理,对无线信道进行时空二维均衡
This study adopts active detection technique based on lamb wave to monitor damage in composite materials . pzt ceramics with the diameter of 8mm are bonded on the surface of fiberglass - reinforced composite material acting as both actuators and sensors to generate and collect lamb waves . the waves emitted interact with discontinuities and experience a change in their propagation characteristics when damage is generated 本文采用lamb波主动监测技术，利用粘贴在复合材料板表面的压电元件，通过选择恰当的激励信号，激励出可进行lamb波分析的主动监测信号，进而对监测信号进行分析及模式处理，初步实现了二维结构的损伤定位。
In this paper , under the wideband radar background , the simulation method of radar clutter , the principle and estimation method of one - dimension and two - dimension physical structure features of radar target , some classification method using physical structure features of target , etc . are studied 本文以宽带雷达体制为研究背景，在复杂背景下，主要研究了雷达背景杂波的仿真、雷达目标一维、二维结构成像的机理和方法，还研究了基于目标结构成像的识别方法等问题。
Material composition appears , and reading material in - put makes the chinese test change from two - dimensional construction to three - dimensional construction ( chinese knowledge , reading and composition ) . graduation tests departing from entrance tests , exploration of the standardized test , weakening the chinese knowledge , the researches of controlling error of judging composition , pattern set " 3 + x " , judging test papers on net , and experiments of spring and summer university entrance test . all the above , having made remarkable achievements , make the current chinese test more modernizing and scientific 供料作文的出现，阅读内容的增加使语文试卷由二维结构到三维结构的转变，毕业会考与升学考试的分离，标准化考试的探索，语文知识考试的淡化，对语文能力测试的重视，作文评分误差控制的研究以及高考“ 3 + x ”科目设置试验，网上阅卷和春夏两季招生考试试验等都为语文考试现代化、科学化作了有益的尝试，也取得了显著的成就。
