干涉SAR图像数据压缩

研究干涉SAR图像数据压缩问题,提出将干涉SAR的数据压缩转化为一个幅度图像的压缩和一个干涉相位图的压缩.设计机上信号处理流程,给出基于DCT和DWT的2种机上数据压缩方法,并对其数据压缩性能进行分析.针对相干斑对干涉相位影响较大的问题,在对干涉相位图进行压缩前,插入回转中值滤波.不同信噪比下干涉SAR仿真数据和实际数据的处理结果,表明了本文方法的有效性.     

Analysis of arithmetic coding for data compression

Arithmetic coding, in conjunction with a suitable probabilistic model, can provide nearly optimal data compression. In this article we analyze the effect that the model and the particular implementation of arithmetic coding have on the code length obtained. Periodic scaling is often used in arithmetic coding implementations to reduce time and storage requirements, it also introduces a recency effect which can further affect compression. Our main contribution is introducing the concept of weighted entropy and using it to characterize in an elegant way the effect that periodic scaling has on the code length. We explain why and by how much scaling increases the code length for files with a homogeneous distribution of symbols, and we characterize the reduction in code length due to scaling for files exhibiting locality of reference. We also give a rigorous proof that the coding effects of rounding scaled weights, using integer arithmetic, and encoding end-of-file are negligible.     

基于HHT和PCA的电能质量数据压缩

针对电力系统日益突出的海量数据存储问题,本文提出了HHT和PCA结合的算法用于电能质量数据压缩.利用HHT进行电能质量信号的故障点检测,将故障信号和正常信号区分重组后用PCA进行压缩以达到数据压缩的效果.采用电能质量数据作为测试样本,实验结果表明,本文算法的压缩性能良好,重构质量高.     

Selection of prefix and postfix word fragments for data compression

In this paper a simple algorithm is used for selection of a set of codeable substrings that occur at the front or rear of the words in a textual data base. Since the words are assumed to be non-repeating, the technique is useful for data compression of dictionaries. The time complexity of the algorithm is governed by the associated sorting algorithm and hence is 0 (n log n). It has been applied to three sample data bases, consisting of words selected from street names, authors names, or general written English text. The results show that the substrings at the rear of the words, yield better compression than those at the front. By application of results of an earlier study in compression coding, efficient encoding and decoding procedures are presented for use in on-line transmission of data.     

The generation and use of text fragments for data compression

An analysis of 31,369 bibliographic titles was carried out to obtain statistics on frequently occurring character groups to increase the effective character set with the aim of estimating possible compression factors for text. It was found that a common set could be used to obtain compression ranging between 30 and 53% over a wide variety of original text.     

星载SAR原始数据实用化数据域压缩算法量化与饱和误差解析

给出了实用化压缩算法(分块自适应算法及截取高位算法)数据域量化与饱和误差的解析表达式,建立了实用化压缩算法数据域信噪比与回波信号标准差之间的关系.最后,将理论推导结果与数据仿真结果、实测数据结果相比较,验证了理论推导结果的正确性,该方法为星载SAR原始数据压缩比选取提供了理论指导.     

基于CCSDS IDC的联合信源与安全编译码

CCSDS图像数据压缩(IDC)标准和分组密码算法SMS4通过将数据压缩与安全分别最优化,使编译码总体性能达到最佳.该算法计算复杂度高,难以保障图像数据在资源受限网络中有效和安全传输.本文使用SMS4分组密钥对图像直流系数进行随机算术编码;对交流系数采用序列加密编码,提出一种基于CCSDS IDC的联合信源与安全编译码算法.仿真实验表明,该算法降低了计算复杂度,同时提供了良好的安全性能.     

一种基于CCSDS IDC标准的可伸缩性视频编码算法

空间通信具有资源受限和差错率高等特点。国际空间数据系统顾问委员会（CCSDS）所制定的图像数据压缩标准（IDC)）一种应用于空间通信的图像编码标准。但该标准未能利用序列的时域相关性,仅适用于图像编码,不适应于空间视频通信。因此,结合运动补偿时域滤波,提出了一种基于CCSDS IDC的可伸缩性视频编码算法以及一种新颖的动态帧分组算法。实验结果表明：该算法具有良好的编码性能,并能适应于空间通信网带宽的动态变化。     

一种基于视频的无损信息隐藏方法

描述了一种基于MPEG-Ⅱ彩色视频中的无损信息隐藏方法，该方法在Alattar算法的基础上，使宿主矢量类型的判别由四个不等式，减小到两个不等式，降低了算法的时间复杂度。数据嵌入过程中采用简单数据链路SDL成帧。在局域网上进行了隐秘传输模拟实验，从嵌入信息的视频中正确提取出所嵌入汉字或二值指纹图像后，原宿主视频可无损恢复。该方法较适用于视频中的隐秘传输及产权保护等领域。     

三维Q值层析成像人机交互软件及其在地震数据处理中的应用

Q值结构对了解地壳的非弹性性质、地壳内部构造、热活动状态、地壳介质非均匀性以及断层分布有着重要的意义.编写了基于吸收特征时间t*的三维Q值层析成像人机交互软件,可以方便快捷地计算地震体波（P波和S波）的振幅谱并通过拟合振幅谱得到反映地震波衰减的吸收特征时间t*,并利用t*资料通过三维Q值层析成像方法得到三维Q值结构.实际观测资料处理结果表明,文中给出的方法和软件是有效且可行的.     

On Lossless Reciprocal and Nonreciprocal Matching Networks of an Active Load

A general matching theory between an arbitrary passive impedance and an active load impedance is presented. It extends the broadband matching theory to include both lossless reciprocal and nonreciprocal networks. Application of the result to the design of nonreciprocal negative-resistance amplifier is given. The significance of the present approach is that the realization of the equalizer is accomplished by means of the driving-point synthesis based on the Darlington theory. The result enlarges the domain of realizable broadband matching networks.An illustrative example is presented to show the design procedure and the conditions under which a lossless nonreciprocal network is realized for an active load.     

视频编码无损传输中帧内多普勒域导频估计算法

通过对视频信号的帧内多普勒域导频估计,实现对视频编码无损传输,提高视频图像传输的保真度。传统方法中对视频编码的导频估计算法采用时域亮度均值重叠分块的奇异值分解方法,视频数据进行强制分片和分块重组,视频编码流出现糊分块效应,导致视频纠错效果不好。针对上述问题,提出一种改进的视频编码无损传输中帧内多普勒域导频估计算法。构建视频传输网络结构模型,进行丢包率预测,把实时视频可以看作多幅的彩色图像按一定时间间隔顺序进行刷新显示,使图像数据将其能量的大部分集中于频率域的一个小范围内,采用量化分析方法提取帧内视频压缩特征,进行视频编码无损传输中帧内多普勒域导频估计算法改进。仿真结果表明,该方法计算精度较高,提高了视频通信的图像保真度,降低了视频失真,提高了视频传输质量,具有较好的视频传输纠错性能。展示了优越性和较好的应用价值。     

一种嵌入式系统解码的高压缩比无损图像压缩算法

针对图像存储、处理和传输过程的巨大数据量和复杂度,本文通过对图像感兴趣区域采用无损编码,改进研究出了一种基于嵌入式零树小波变换算法的不同区域编解码压缩算法,可以实现改变压缩比以及可手动选择任意形状的感兴趣区域的功能。改进的算法保证了压缩重构图像感兴趣区域质量清晰,对标准测试图实验结果表明,此算法具有较高的压缩比和图像恢复质量,取得较好的效果。     

偏心受压对称配筋柱用双面围套补强实例

混凝土偏心受压构件,尤其是偏心受压对称配筋柱,强度不满足要求时,可用双面围套加以补强.     

偏心受压对称配筋柱用双面围套补强实例

混凝土偏心受压构件，尤其是偏心受压对称配筋柱，强度不满足要求时，可用双面围套加以补强.     

On the compression of search trees

Let X=_x1,_x2,…,_xn$X=x_1\text{,}{x}_2\text{,}\dots \text{,}{x}_n$ be a sequence of non-decreasing integer values. Storing a compressed representation of X that supports access and search is a problem that occurs in many domains. The most common solution to this problem uses a linear list and encodes the differences between consecutive values with encodings that favor small numbers. This solution includes additional information (i.e. samples) to support efficient searching on the encoded values. We introduce a completely different alternative that achieves compression by encoding the differences in a search tree. Our proposal has many applications, such as the representation of posting lists, geographic data, sparse bitmaps, and compressed suffix arrays, to name just a few. The structure is practical and we provide an experimental evaluation to show that it is competitive with the existing techniques.     

Data compression producing structures—Discoveries

This paper describes a formalism to construct some kinds of algorithms useful to represent one structure about a set of data. It proves that if we do not take into account cost considerations of one algorithm, one can partialy replace the memory by an algorithm. It also proves that the remaining memory part is independant of the construction process. It then evaluate the affects of algorithms representation cost and gives the resulting memory gain obtained in two particular examples.