一类二阶Duffing方程反周期解的存在性和多重性北大核心CSCD

采用变分方法证明了一类带反周期边界条件的二阶Duffing方程解的存在性和多重性.     

用动态规划方法综合不等距线阵

动态规划方法是综合不等距阵的一个有效方法,但当阵元数比较多时计算量比较大。本文通过对阵元位置进行限制,避免过多的重复计算,使运算量大幅度减少。此外提出了重复迭代方法,可使旁瓣级进一步降低。     

圆弧阵的水平指向性和综合

本文使用稳相法详细讨论了圆弧阵的水平指向性,给出了计算指向性函数的主瓣束宽和主瓣内平均声压的比较准确的公式。本文提出的幅度束控方法和设计不等距阵方法可以成功地克服圆弧阵主瓣内指向性函数起伏大的缺点,同时使主瓣束宽和主瓣内平均声压基本保持不变。     

具有反声障板的圆柱(弧)基阵水平指向性的研究

本文详细分析了反声障板对阵元指向性和频响的影响,给出了圆柱(弧)阵的接收响应和水平指向性的计算公式,并讨论了阵参数对阵性能的影响,文后给出了部分实验结果,与理论结果基本符合。     

平面障板对换能器指向性的影响

木文利用射线声学和虚源法,研究了无限大平面障板对换能器指向性的影响.对几种典型的障板做了数字计算和讨论,从中得出的一些规律,对障板的工程设计可能有指导作用.计算值与实验做了比较,二者基本符合.     

A NEW METHOD OF AMPLITUDE SHADING FOR ANY ARRAY

In this paper a new method of amplitude shading applicable to any array is presented.Fora specified sidelobe level,this method can be used to obtain the optimum or nearly optimum direc-tivity pattern in the sense that either the area enveloped by a function,namely pressure square,reachthe minimum or the directivity factor reaches the maximum. The height and the position of every sidelobe can be Changed using this method,and so wecan obtain various directivity patterns required in practice. The compensated arc array with cylindrical reflecting back baffle is synthesized.The resultsobtained using this method are compared with those obtained using several other methods.Thismethod is also applied to linear arrays.We can obtain almost the same shading coefficients anddirectivity function as those obtained by Dolph's method.In principle,this method can also beapplied to synthesis of phase shading and unequal spacing arrays.     

沪深股票市场之间波动性影响关系研究

以对沪深两市波动性指标的解构分析为基础,给出了基于GRACH模型、Granger模型的综合运用,同时引入协整检验和误差纠正机制的均衡分析方法,对沪深两市的波动相关性进行实证分析和模型检验,系统性揭示了沪深两市波动性的关键特征和沪深两市波动互相影响的因果规律,为基于沪深两市金融资产的定价和风险管理奠定了基础.     

能量守恒定律在指向性函数计算中的应用(Ⅱ)——用于不等距阵和综合

本文应用能量守恒定律研究了稀疏不等距阵的平均旁瓣高度;导出估算最佳不等距阵最高旁瓣高度的公式,与实际设计出的阵和随机阵的估计做了对比,证明该式比随机阵的公式更加接近实际;研究了能量守恒定律在指向性综合中的应用。     

A GENERAL METHOD OF DIRECTIVITY SYNTHESIS

Two synthesis methods are discussed in this paper.One of them is the method in which criteriaof minimum mean square diviation is used.It is applicable to the synthesis in which the whole direc-tivity function is required to fit with expected function.Anothor is a successive approximation me-thod.It is applicable to the synthesis in which every peak of sidelobe fits with expected curve andthe mainbeam width is required to be narrowest.Both methods can be applied to the synthesis ofamplitude shading,phase shading and unequally spaced arrays. The principles of two methods are studied in some detail.Some typical patterns are synthesizedby the amplitude shading of linear arrays in this paper.