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1.
T. Radhakrishnan 《Information processing & management》1978,14(2):97-106
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. 相似文献
2.
A new method of index term dictionary compression in an inverted-file-orientated database is discussed. A technique of word coding that generates short fixed-length codes obtained from the index terms themselves by analysis of monogram and bigram statistical distributions is described. Transformation of the index term dictionary into a code dictionary preserves a word-to-word discrimination with a rate of three synonyms per 1300 terms, at compression ratio up to 90% and at low cost in terms of the CPU time expenditure. When applied in computer network environment, it offers substantial savings in communication channel utilization at negligible response time degradation. Experimental data for 26,113 index term dictionary of the New York Times Info Bank available via a computer network are presented. 相似文献
3.
在3DGIS领域中,空间数据结构占有突出的地位,它直接关系到GIS的功能和效率。为了对3DGIS海量数据进行有效地存储和管理,本文讨论了3DGIS栅格数据结构线性八叉树编码压缩技术,并在原来压缩技术基础上,对其压缩过程进行了改进,同时给出了改进后的压缩和解压缩算法。通过对改进前后算法的比较,发现改进后的算法在压缩时间和数据压缩率上都有显著提高。 相似文献
4.
复杂地区典型特征往往表现为近地表地质结构复杂,纵向、横向变化大,地下地质构造破碎,大倾角老地层出露。介绍了该类地区地震资料的主要特点;分析了处理好该类地震资料起决定性作用的静校正、去噪技术、频率补偿及偏移成像几个重要环节,并指出了生产中应注意的几个问题。 相似文献
5.
针对分形编码算法编码时间太长、精度控制需要细分等缺点提出对编码图像进行分级逼近的新的分形编码算法．对这一思想的可行性在理论上进行了有益的探索,给出了该算法成立的理论基础,并得出了任给一图像,都可以找出一组压缩变换,使得从任意图像出发,经该组变换压缩迭代后重构原始图像的新的构造性证明．给出一个新的具体实现分形编码的算法．实验表明,在提高压缩比和图像恢复质量的同时,运算时间也大大缩短 相似文献
6.
使用动态标定是获得高压传感器的动态特性的一般方法。由于校准装置的特点，得到的模型特性有一些固有的限制。在某些频带的信息不完全，在标定的时候受到设备振动模式和产生的压力波的影响。应用小波分柝去除噪声，提高信噪此。小波理论此短时傅立叶分析有更多的优势，可以抽取更多的特征信息．它已经成功地用于图像处理、断点检测，去噪和数据压缩等方面。这项技术被用于压力传感器建模取得了一些结果。 相似文献
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8.
A novel visually imperceptible image hiding scheme based on VQ compression and LSB modification is introduced in this article. Multiple secret images can be simultaneously and imperceptibly hid into another cover image with the same image size by the proposed scheme. In order to reduce the volume of secret images to be hid, a codebook is first generated from the secret images and these images are encoded into binary indices by the vector quantization technique. Then the compressed data of secret images are embedded into the VQ codebook used in the encoding procedure by an adaptive least-significant-bits (LSB) modification technique. For the security purpose, the slightly modified codebook is further encrypted into a meaningless data stream by the DES cryptosystem. Finally, the encrypted codebook is embedded into the cover image using the greedy LSB modification technique. Simulation results show that the proposed scheme provides a good improvement in the visual quality of the extracted secret images and the cover image at the receiver. In addition, the proposed scheme provides better hiding capacity for the cover image than earlier works. 相似文献
9.
《Journal of The Franklin Institute》1987,324(1):165-172
The performance of a discrete-time linear estimator which receives compressed, quantized measurements is studied. Upper and lower bounds for the expected value of the estimate error covariance, along with the necessary equations for computing the probability of processing a measurement under the proposed data compression technique, is presented. 相似文献
10.
宏观国土资源信息是可持续发展重要基础，将部门和科研人员所拥有的数据通过互联网络等新技术进行共享，使之为我国的可持续发展发挥作用。作者从目前宏观国土资源信息共享专题所选择的数据库入手，阐述了该数据库的互联网络共享的目标、内容，并总结了在数据库上网所要解决的关键技术。指出目前宏观国土资源信息共享的重大进展和进一步工作的目标。完整共享机制的法律法规保证，强有力的技术支撑，丰富实用的数据库应该成为下一个阶段工作的重点。 相似文献
11.
大数据的应用是学术和实践热点,但现有研究缺乏数据驱动的新产品开发过程研究。基于新产品开发理论,构建大数据嵌入的新产品开发过程对创新绩效作用机理的理论模型。收集跨国数据,采用回归分析,验证理论模型。结果表明：中美新大数据嵌入的商业分析和产品测试提高创新绩效。在中国,大数据嵌入的产品设计最能提升销售增长率;而在美国和新加坡,大数据嵌入的产品测试最能提升销售增长率。在中国,大数据嵌入的产品设计最能提高毛利率;而在美国,大数据嵌入的产品测试最能提高毛利率;在新加坡,则是大数据嵌入的市场投放最能提高毛利率。 相似文献
12.
在当今类似车载系统中常有需要我们在物体时空运动数据库中进行数据挖掘,然后根据得到的规则预测物体的运动趋势的需求。至今,对于由时空两方面描述的数据进行挖掘的研究还没有特别明确的方法。提出MINE_ALLFP算法来发现所有的频繁集。为了增加研究的可行性,去掉位置信息的连续性,提出将整个大空间分割为若干个小区域的方法,这里还引进一种好的剪枝算法。 相似文献
13.
杨立强 《中国科学院研究生院学报》2005,22(3):359-363
利用LOG算子和改进相干算法相结合来提高信噪比和地震资料分辨率 ,并同其他方法作了比较 .模型数据与实际数据的应用效果证明 ,该方法具有较强的信噪分离作用 ,能有效提高地震资料分辨率 ,该方法是实用的 . 相似文献
14.
William E. Bonini 《Journal of The Franklin Institute》2006,343(3):233-242
During the mid-1960s, Peter R. Vail at Exxon Production Research Co. led a group working with the new, greatly improved generation of multifold seismic reflection data being shot along the continental margins of the world. The work of this group, inspired by Vail, brought the worlds of stratigraphy and seismic interpretation together in developing the original concepts of seismic stratigraphy.Later these concepts were applied by Vail and his co-workers to well logs, cores, and outcrops, broadening seismic stratigraphy into what is known today as sequence stratigraphy. Using these data the group was documenting and interpreting large-scale, basin-wide depositional patterns, stratal configurations, and unconformities in basins around the world. They proposed a chronology of global sea-level fluctuation as a framework for global correlation, resulting in a world sea-level curve. This further led to a new eustatic sea-level model. The results of these studies impacted on many scientific disciplines, but its implications for the petroleum industry have been extensive.A review of 19th- and 20th-Century stratigraphic thought on unconformities and unconformity-bounded stratal units suggests that Peter Vail followed in the footsteps of the eminent stratigraphers Charles Lyell, T. C. Chamberlain, and L. L. Sloss, his former teacher.For his contributions to sequence stratigraphy and the world sea-level curve, Peter R. Vail was awarded the 2005 Benjamin Franklin Medal in Earth and Environmental Science. 相似文献
15.
随着互联网技术的不断发展,以图像为主要载体的多媒体信息大大丰富了我们的生活。但由于图像数据量庞大,存储和传输时受到很大限制,使得图像压缩成为图像处理中的一个重要环节。图像压缩就是利用图像自身的相关性来消减图像的冗余信息,保留有用的信息。经过多年的研究,人们已经提出了多种图像压缩方法,并在许多领域取得了良好的应用效果。但这些方法主要是针对普通密度的图像,而对于稀疏图像的压缩,目前有效的压缩方法还屈指可数。对图像压缩技术的发展历程进行了回顾,给出了一种基于哈希表的对稀疏数据压缩方法,并利用VC＋＋6．0平台,实现了基于哈希表的数据压缩系统。 相似文献
16.
企业持续捐赠是否值得?基于时间压缩不经济及动态能力理论,以中国A股上市公司捐赠的面板数据为依据,本文分析并检验了企业持续捐赠的价值效应。研究发现,虽然持续捐赠不能直接给企业带来价值增值,但以企业通过持续捐赠获取的各种无形及有形资源需要积极运作为推论,进一步的实证表明,随着企业动态能力增强,企业持续捐赠的价值效应逐趋明显。另外,拓展性检验还发现,促成以上资源获取及能力发挥的情境因素越凸现,企业持续捐赠的价值回报亦越大。本文为针对性地探明企业持续捐赠的价值效应提供了新的理论和经验证据,有助于职能部门出台适宜的引导政策促进企业持续捐赠行为,同时也有利于企业探寻可行的对策提升持续捐赠的回报。 相似文献
17.
M.R.D. Al-Mothafar 《Journal of The Franklin Institute》2012,349(1):260-283
A procedure is established for the small-signal modelling of n-connected current-programmed parallel-input/series-output pulse-width modulated bridge-based buck dc–dc converters operating in the continuous-current conduction mode. State-space averaging is used to represent the power stage while current-mode control is modelled using a modified new continuous-time technique. Approximate analytical expressions of the major small-signal transfer functions that include the number of modules as a variable are proposed. PSpice simulations are carried out to validate the analysis. 相似文献
18.
Sequences of integers are common data types, occurring either as primary data or ancillary structures. The sizes of sequences can be large, making compression an interesting option. Effective compression presupposes variable-length coding, which destroys the regular alignment of values. Yet it would often be desirable to access only a small subset of the entries, either by position (ordinal number) or by content (element value), without having to decode most of the sequence from the start. Here such a random access technique for compressed integers is described, with the special feature that no auxiliary index is needed. The solution applies a method called interpolative coding, which is one of the most efficient non-statistical codes for integers. Indexing is avoided by address calculation guaranteeing sufficient space for codes even in the worst case. The additional redundancy, compared to regular interpolative coding, is only about 1 bit per source integer for uniform distribution. The time complexity of random access is logarithmic with respect to the source size for both position-based and content-based retrieval. According to experiments, random access is faster than full decoding when the number of accessed integers is not more than approximately 0.75 · n/log2n for sequence length n. The tests also confirm that the method is quite competitive with other approaches to random access coding, suggested in the literature. 相似文献
19.
Real options analysis was often recommended as an emerging valuation technique for high-risk investment projects. Former inter-sectoral surveys have drawn an ambivalent picture of real options usage in general. In addition, there is a lack of sector-specific investigations. In the following article the results of an in-depth analysis of collected empirical data regarding the application of this new tool in the pharmaceutical sector is presented by capturing the internal view from the pharmaceutical companies themselves and the external view from the health care departments of financial service firms. R&D stage specific modi of application, reasons for reluctance in the employment of real options and their assumed future prospects are elucidated. 相似文献
20.
最大作用距离和距离分辨力是雷达应用中两个关键的性能指标,但在常规脉冲体制雷达中,这两个指标是相互矛盾的。脉冲压缩技术的出现,有效的解决了该问题。文章先介绍了脉冲压缩技术,然后通过MATLAB仿真验证了脉冲压缩技术在解决这对矛盾时的有效性。 相似文献