基于克里金空间插值的位置指纹数据库建立算法*

为解决室内定位系统中建立位置指纹数据库工作量庞大的问题,提出了一种融合信号衰减因素的普通克里金空间插值建库算法。该方法首先采用高斯滤波对有限预选参考点的信号强度采样数据进行预处理,并基于球状模型由参考点预处理数据拟合出空间变异函数,然后采用普通克里金插值法对其它位置的信号强度进行估值并生成相应的位置指纹,最后由有限实测数据生成大容量高分辨位置指纹数据库,并通过KNN_Filter算法和对数权重算法完成了定位仿真,验证了该建库方法的有效性。仿真实验结果表明,该算法在保证定位精度的前提下相比传统建库方法可降低40%左右的工作量,提高了室内位置指纹定位方法的工作效率。     

Planar Shape Interpolation Based On Teichmüller Mapping

Shape interpolation is a classical problem in computer graphics and has been widely investigated in the past two decades. Ideal shape interpolation should be natural and smooth which have good properties such as affine and conformal reproduction, bounded distortion, no fold‐overs, etc. In this paper, we present a new approach for planar shape interpolation based on Teichmüller maps ‐ a special type of maps in the class of quasi‐conformal maps. The algorithm consists of two steps. In the first step, a Teichmüller map is computed from the source shape to the target shape, and then the Beltrami coefficient is interpolated such that the conformal distortion is linear with respect to the time variable. In the second step, the intermediate shape is reconstructed by solving the Beltrami equation locally over each triangle and then stitching the mapped triangles by conformal transformations. The new approach preserves all the good properties mentioned above and produces more natural and more uniform intermediate shapes than the start‐of‐the‐art methods. Especially, the conformal distortion changes linearly with respect to the time variable. Experiment results show that our method can produce appealing results regardless of interpolating between the same or different objects.     

面向高质量加工的NURBS曲线插补算法

通过分析数控系统加工时常用的插补算法的特点,提出一种基于NURBS曲线的插补算法.该算法包括速度规划和实时插补两部分:速度规划部分考虑了工件加工时允许的最大轮廓误差,以保证高速运行过程中加速度的连续,使机床运行平稳,避免产生大的冲击;实时插补部分应用弦截法计算插补参数,能将实时插补产生的速度波动控制到理想水平,进一步减小了机床震颤.仿真实验结果表明,文中算法能够减小机床振动,实现高质量加工.     

一种改进的基于FFT的信号插值算法

在传统运用FFT进行信号插值运算的基础上,提出了一种提高插值精度的改进算法.通过子序列重叠和裁剪,舍弃重建序列边缘误差较大的样点,再将相对准确的样点进行重组,从而大幅提高插值精度.实验结果表明:与Prasad等算法相比,在计算量增加3.1％的情况下,不同子序列长度对应的归一化均方误差平均下降至原来的1/19;在计算量增加2倍的情况下,不同子序列长度对应的归一化均方误差平均下降至原来的1/75.     

一种二次样条保单调Hermite插值方法

提出一种保单调的二次样条Hermite插值方法。该方法在研究总结其他二次样条插值方法的基础上,通过设定适当的结点斜率保证了插值曲线的单调性,并且给出了算法的严格证明;该算法在一个给定的点列上进行了验证,验证结果表明该算法可以得出连续、平滑的插值曲线,具备较为优秀的性能。     

An extended iterative format for the progressive-iteration approximation

Progressive-iteration approximation (PIA) is a new data fitting technique developed recently for blending curves and surfaces. Taking the given data points as the initial control points, PIA constructs a series of fitting curves (surfaces) by adjusting the control points iteratively, while the limit curve (surface) interpolates the data points. More importantly, progressive-iteration approximation has the local property, that is, the limit curve (surface) can interpolate a subset of data points by just adjusting a part of corresponding control points, and remaining others unchanged. However, the current PIA format requires that the number of the control points equals that of the data points, thus making the PIA technique inappropriate to fitting large scale data points. To overcome this drawback, in this paper, we develop an extended PIA (EPIA) format, which allows that the number of the control points is less than that of the given data points. Moreover, since the main computations of EPIA are independent, they can be performed in parallel efficiently, with storage requirement O(n), where n is the number of the control points. Therefore, due to its local property and parallel computing capability, the EPIA technique has great potential in large scale data fitting. Specifically, by the EPIA format, we develop an incremental data fitting algorithm in this paper. In addition, some examples are demonstrated in this paper, all implemented by the parallel computing toolbox of Matlab, and run on a PC with a four-core CPU.     

A general (k, n) scalable secret image sharing scheme with the smooth scalability

A novel (k, n) scalable secret image sharing (SSIS) scheme was proposed to encrypt a secret image into n shadow images. One can gradually reconstruct a secret image by stacking k or more shadows, but he/she cannot conjecture any information from fewer than k shadows. The advantage of a (k, n)-SSIS scheme is that it provides the threshold property (i.e., k is a threshold value necessary to start in to reveal the secret) as well as the scalability (i.e., the information amount of a reconstructed secret is proportional to the number of shadows used in decryption). All previous (k, n)-SSIS schemes did not have the smooth scalability so that the information amount can be “smoothly” proportional to the number of shadows. In this paper, we consider the smooth scalability in (k, n)-SSIS scheme.     

基于FPGA的四通道视频缩放引擎的研究及设计

设计了一种可实现4路视频信号缩放和帧率转换的电路架构.视频信号依次经过缩小模块、帧率转换模块以及放大模块,有效地减少了帧率转换对存储器带宽的需求.帧率变换模块采用输入和输出自适应调整的算法,同时在缩小模块采用加权均值算法,而放大模块则采用四点双三次插值算法.在满足视频放大质量要求的基础上,避免了采用过于复杂算法而消耗过...     

基于三次样条插值的采样数据光滑曲线形成法

在计算机机辅助测试（CAT）中,所测得的数据一般为一系列的离散系统样数据,怎样将它恢复为不失真的连续光滑曲曲线并打全出呢？本文提出了三次样条插值函数的形成法及其局限性,并对三次样条插值提取出了改进方法,使测得的一系列离散点能形成光滑的曲线。     

近似弧长参数化的三次保形插值

在构造近似弧长参数化曲线时,必须添加某些额外的数据点,以获得足够的近似弧长参数化精度,对于参数三次曲线,给出了一个“双点单位化”的近似弧长参数化公式,为如何选择这些额外数据点提供了理论依据,所给出的方法既能有效地提高近似弧长参数化精度,同时又满足了保形插值的要求。