MIMO雷达相位编码波形集相关函数下界综述

MIMO雷达波形集的互相关函数峰值越低,则正交性越好,波形分集增益越高。非循环互相关函数下界的研究有助于确定波形分集增益的极限值,对MIMO雷达波形设计与应用有重要意义。相位编码波形集是目前被研究最多的MIMO雷达波形集,对其相关函数下界的研究较为深入。本文对目前相位编码波形集相关函数各类下界的研究进行归纳总结,包括相关函数峰值旁瓣下界、相关函数积分旁瓣下界、互相关内积下界、互补序列相关函数下界四大类。相关函数峰值旁瓣下界是影响MIMO雷达波形分集增益的关键指标,其他类型的下界与相关函数峰值旁瓣下界之间存在潜在联系,这可能有助于相关函数峰值旁瓣下界的确定。不同波形数,不同码长的典型相位编码波形相关函数指标与下界的对比结果表明,目前已有下界都不够紧,尤其在波形数较多时。因此,MIMO雷达相位编码波形集相关函数下界仍是一个值得研究的开放问题。

基于并行变可信度置信下界算法的航行体天线罩结构优化设计

[目的]为了使水下发射的航行体天线罩结构在满足碰撞性能要求的条件下,尽可能减轻结构质量,提出一种并行变可信度置信下界(PVF-LCB)算法,对航行体天线罩结构尺寸进行优化设计。[方法]变可信度置信下界(VF-LCB)函数在设计过程中可自适应地分配计算资源,可以使用高/低精度代理模型构建影响函数(IF),选取对模型改善较大的多个样本点,最后与相应的约束处理策略结合,从而对航行体天线罩结构尺寸进行优化。[结果]提出的方法使航行体天线罩的结构尺寸优化设计满足了要求,且质量比基于变可信度代理模型的串行优化方法降低了约50%,并缩短了设计优化时间;相比单精度并行优化方法,天线罩质量降低约30%,搜索优化可行解的效率得到提高。[结论]该方法在航行体的天线罩结构优化设计中不仅缩短了设计周期,而且提高了优化解的质量,在工程应用中具有一定的发展前景及指导意义。

岭估计均方误差的下界

讨论岭估计的一些理论问题,给出了若干岭估计均方误差的下界函数.

一类弱二次Hamilton系统的同宿解的多重性结果

考虑二阶非自治弱二次Hamilton系统同宿解的多重性.一般考虑的势函数关于u在无穷远点处的下界函数是一个正常数.而当该系数换为一个正函数而非常数时,情况就会相当不同.该文中讨论了这一问题,将此系数推广到下确界可以是0的一个有关t的正函数.因此该文的结果是对近期一些结果的有意义的改进.

面向不确定时间序列的分类方法

时间序列的分类问题在生物、经济金融分析、语音处理等方面有着广泛的应用.在传统的确定性的时间序列上这项技术已得到了深入的研究,并取得了很好的效果;但在新兴的不确定时间序列上解决方案还很少.不确定模型更能真实地反映现实世界;因此,研究不确定时间序列的分类问题有很大的实际意义.DTW距离是确定性的时间序列上的重要的度量方式,但其不能直接应用于不确定时间序列之上.提出了基于期望距离的不确定时间序列下的DTW距离.给出了期望距离的一种简单计算方法,从而简化了不确定时间序列的建模,降低了模型的存储代价.利用期望距离公式的特点,将确定性的时间序列DTW的距离下界函数LB_Keogh进行扩展,得到了不确定时间序列的下界函数ULB_Keogh.实验结果显示:提出的DTW算法对于不确定时间序列的分类有着很高的正确率;ULB_Keogh下界函数有着很好的剪枝效果.

一种改进的DTW相似性搜索方法

为了更有效的对时间序列进行相似性搜索,本文从相似性度量函数的角度提出一种改进的基于下界函数的DTW (Dynamic Time Warping)相似性搜索方法NLB-FDTW。上述方法定义一种更有效的下界函数,减少DTW的计算开销,加快相似性搜索的速度。为了验证所改进的DTW相似搜索算法的有效性,对一个月的交通流量进行了相似性搜索的实验。结果表明,基于下界函数的DTW在很大程度上减少计算量,NLB-FDTW相较于基于欧氏距离或原始DTW的相似性搜索是一种高效的时间序列相似性搜索方法。

语音识别中动态时间规整算法的硬件加速实现

动态时间规整算法(Dynamic Time Warping,DTW)是语音识别中常用的技术之一。为了提升因数据量增加以及算法对数据的高度依赖性所导致的计算性能降低,提出一种针对语音帧的动态时间规整算法硬件架构。识别计算过程中,通过使用算法时间复杂度相对低的下界距离函数(Lower Bound Function,LBF)取代算法时间复杂度高的动态时间规整算法进行语音特征序列全模板匹配,筛选出近似的语音特征序列,经过逻辑组件的流水线调度送入PE-FIFO环形计算单元,进行精准动态时间规整计算。实验使用ARTIX-7 XC7A35T器件进行板级验证,平均耗时4.58 ms,相较于同类型硬件识别方案速度提升4倍以上,识别率达到91%。

Remark on Some Classes of P-valent Functions

Recently,Aouf and Darwish [1] proved some estimates in relation to the real part of function D k+p-2 f(z)z p for f(z)∈R(1,k,p,α). In this paper we improve their results and obtain the sharp estimation.

Upper Bound and Lower Bound Estimate of Monotone Increasing Fractal Function

Mass distribution principle is one of important tools in studying Hausdorff dimension and Hausdorff measure. In this paper we will give a numerical approximate method of upper bound and lower bound of mass distribution function f（x）（it is a monotone increasing fractal function） and its some applications.

Multistatic radar analysis based on ambiguity function and Cramér-Rao lower bounds

The primary goal of this work is to characterize the impact of weighting selection strategy and multistatic geometry on the multistatic radar performance. With the relationship between the multistatic ambiguity function （AF） and the multistatie Cram6r-Rao lower bound （CRLB）, the problem of calculating the multistatic AF and the multistatic CRLB as a performance metric for multistatic radar system is studied. Exactly, based on the proper selection of the system parameters, the multistatic radar performance can be significantly improved. The simulation results illustrate that the multistatic AF and the multistatic CRLB can serve as guidelines for future multistatic fusion rule development and multistatic radars deployment.

Monotonicity Results and Inequalities for Inverse Hyperbolic Sine

In this paper,we present monotonicity results of a function involving the inverse hyperbolic sine.From these,we obtain some lower bounds for the inverse hyperbolic sine.

More on Convering Squares with Squares

This paper improves some lower bounds of a function f(x) introduced in the problem of covering squares with squares.

Algorithms for computing the global infimum and minimum of a polynomial function

By catching the so-called strictly critical points,this paper presents an effective algorithm for computing the global infimum of a polynomial function.For a multivariate real polynomial f ,the algorithm in this paper is able to decide whether or not the global infimum of f is finite.In the case of f having a finite infimum,the global infimum of f can be accurately coded in the Interval Representation.Another usage of our algorithm to decide whether or not the infimum of f is attained when the global infimum of f is finite.In the design of our algorithm,Wu’s well-known method plays an important role.

Gradient Estimates for a Nonlinear Parabolic Equation with Diffusion on Complete Noncompact Manifolds

The authors obtain some gradient estimates for positive solutions to the following nonlinear parabolic equation:αu/αt=△u-b(x,t)u~σ on complete noncompact manifolds with Ricci curvature bounded from below,where 0<σ<1 is a real constant,and b(x,t) is a function which is C^2 in the x-variable and C^1 in the t-variable.

A CLOSEDNESS CRITERION FOR THEDIFFERENCE OF TWO CLOSED CONVEXSETS IN GENERAL BANACH SPACES

The authors give some sufficient conditions for the difference of two closed convex sets to be closed in general Banach spaces, not necessarily reflexive.