共查询到20条相似文献，搜索用时 31 毫秒
1.
2.
3.
高强度人为扰动所带来的地表破碎化使得"同物异谱"和"异物同谱"现象特别严重,仅靠地物光谱特征统计提取土地利用信息存在明显缺陷与不足,探索符合特定区域的基于多元方法耦合的土地利用信息提取模型显得非常必要,可为复杂土地利用信息提取提供便捷通道.本文首先找出典型土地利用类型的光谱特征和归一化差异型指数变化规律,再运用交互式数据语言耦合光谱信息并建立决策函数,对1993年、2001年和2009年3期TM影像进行决策树分类,以自动提取三峡库区回水淹没与快速城市化重叠区这一高强度人为扰动复合区典型土地利用信息.结果表明:典型地类的波谱响应曲线和归一化差异型指数曲线分布形态符合于地表三大基本地类特征,以此验证了研究中所选取的三种指数的合理性和各地类样区选择的有效性;各地类在TM影像1、2、3波段上因光谱特征变化趋势无明显差异、相关性较强而不易于提取,3、4、5波段光谱特征因差异变化最大、所包含的土地利用信息最为丰富而更易于提取样区典型地类;三种指数及其差值组合指数的曲线分布形态及其值变化与研究区的实际地类变化较为吻合;多元方法耦合的决策树分类比监督分类方法在提取土地利用信息上具有更高的精度,在样区土地利用自动分类中是一种低成本、易实现和推广的有效方法,从1993年、2001年和2009年总体分类精度分别提高了18.46%、15.43%和24.18%.据此,基于多元方法耦合的决策树分类模型能为三峡库区人为扰动复合区土地利用信息提取提供一可操作途径,为整个三峡库区土地利用信息自动提取提供已有方法的整合思路. 相似文献
4.
扩展频水印技术是一种鲁棒的水印算法 .如何提高扩频水印算法的鲁棒性是当前一大研究热点 .充分利用图象的像素与其周围像素之间的差值的统计特性 ,利用差调制的方法嵌入水印信息 ,从而降低了原始图象对该水印算法鲁棒性的影响 ,来提高水印算法的鲁棒性 .理论分析表明 ,该算法可以同时获得较小的误警和误拒概率 ,从而表明该算法有较好的性能 .实验结果表明 ,该算法可以鲁棒地抵抗常用的攻击 ,如JPEG压缩、中值滤波、加噪声和图象大小调整 . 相似文献
5.
提出了一种具有抵抗不可见位攻击的二进制指纹编码,对由基于随机序列的编码算法产生的指纹序列进行Turbo编码,之后采用扩频理论对用户指纹进行调制,使离散编码算法在对误码情况的容忍性上有了一定的提高,具有较高的合谋容忍性。 相似文献
6.
Rodrigo P. Lemos Jonas A. Kunzler Diego F. Burgos B. Mário J. de Souza Hugo V.L. e Silva Yroá R. Ferreira Edna L. Flôres Oliver Sander 《Journal of The Franklin Institute》2019,356(9):4949-4969
SEAD method estimates the direction-of-arrival angles on an uniform linear array based on the difference between the two largest singular values, what is called differential spectrum. Although it presented an outstanding performance, the ability to indicate the source positions was not elucidated yet. Inspired by the differential spectrum formulation we derived a total differential spectrum and found out that the matrix norm induced by the vector 2-norm of a modified spatial covariance matrix can be used to estimate the direction-of-arrival of multiple plane waves. Indeed we show that matrix norms are estimators and we propose their use instead of the singular value decomposition in SEAD-based methods. We present a general mathematical expression in order to explicit the operating principles of the proposed methods. Consequently, we were able to explain how the relation between the arriving and the search angles produces the larger peaks on the differential spectrum. To evaluate the important role played by matrix norms, a thousand experiments were carried out. They showed that the proposed approach proved to be as accurate as the previous SEAD-based methods, while providing a significant reduction on runtime. It also outperformed well-established methods like MODEX regarding the estimation error. 相似文献
7.
Rodrigo P. Lemos Jonas A. Kunzler Diego F. Burgos B. Mário J. de Souza Hugo V. L. e Silva Yroá R. Ferreira Edna L. Flôres Oliver Sander 《Journal of The Franklin Institute》2019,356(6):3781-3796
SEAD method estimates the direction-of-arrival angles on an uniformly linear array based on the difference between the two largest singular values, what is called differential spectrum. Although it presented an outstanding performance, the ability to indicate the source positions was not elucidated yet. Inspired by the differential spectrum formulation we derived a total differential spectrum and found out that the matrix norm induced by the vector 2-norm of a modified spatial covariance matrix can be used to estimate the direction-of-arrival of multiple plane waves. Indeed we show that matrix norms are estimators and we propose their use instead of the singular value decomposition in SEAD-based methods. We present a general mathematical expression in order to explicit the operating principles of the proposed methods. Consequently, we were able to explain how the relation between the arriving and the search angles produces the larger peaks on the differential spectrum. To evaluate the important role played by matrix norms, a thousand experiments were carried out. They showed that the proposed approach proved to be as accurate as the previous SEAD-based methods, while providing a significant reduction on runtime. It also outperformed well-established methods like MODEX regarding the estimation error. 相似文献
8.
The Cepstrum processing method has been used on power cables (1, 2) for determining regions of damage. The method consists of: (1) observing the spectrum of an original broad band signal source, (2) introducing the signal into the cable, (3) computing the change in the observed spectrum (as a result of echos from regions of cable non-uniformity) when the signal is injected into the cable, and finally (4) computing the power-spectrum of the change in observed spectrum. A limitation of this technique is the use of band-limiting spectrum analyzers. Their limited bandwidth reduces range resolution estimation when used with the Fast Fourier Transform (FFT) technique. The maximum entropy method (MEM) is a more useful spectral estimator for this measurement technique. Examples are presented which show a comparison of the FFT and MEM techniques applied to practical cables. 相似文献
9.
Kenneth R. Fleischmann 《The Information Society》2013,29(5):361-371
This article examines nonhuman agency, or the capacity of nonhumans to carry out goal-directed action. The central argument is that agency should be conceptualized not as a binary (someone/something does or does not have agency) but rather as a spectrum, with degrees of agency. Based upon an empirical study of the design and use of frog dissection simulations (cyberfrogs) in high school biology classes, the author develops two parallel spectra of agency, bioagency and cyberagency, to describe the degrees of agency experienced by biological life forms and technologies. These spectra put agency into an evolutionary perspective, comparing how humans evolved agency over time to how technologies are now evolving agency. The article concludes with challenges for future research to further explore the validity and implications of a notion of cyberagency that evolves over time, can be represented on an analog spectrum, and is independent of human agency. 相似文献
10.
《The Information Society》2007,23(5):361-371
This article examines nonhuman agency, or the capacity of nonhumans to carry out goal-directed action. The central argument is that agency should be conceptualized not as a binary (someone/something does or does not have agency) but rather as a spectrum, with degrees of agency. Based upon an empirical study of the design and use of frog dissection simulations (cyberfrogs) in high school biology classes, the author develops two parallel spectra of agency, bioagency and cyberagency, to describe the degrees of agency experienced by biological life forms and technologies. These spectra put agency into an evolutionary perspective, comparing how humans evolved agency over time to how technologies are now evolving agency. The article concludes with challenges for future research to further explore the validity and implications of a notion of cyberagency that evolves over time, can be represented on an analog spectrum, and is independent of human agency. 相似文献
11.
高精度输出半导体激光器的温度控制系统设计 总被引：1，自引：0，他引：1
本文利用高信噪比的运算放大器、半导体制冷器,设计了一种激光器的温控系统,其能为半导体激光器提供高稳定度的恒温控制(ATC),从而提高了半导体激光器的使用寿命和输出波长的单一性。 相似文献
12.
由于色散和非线性效应的相互作用,连续波或准连续波在光纤中传输时,会出现调制不稳定性.利用非线性薛定谔耦合方程,在假设光脉冲幅值受到微扰的情况下,用解析的方法,研究了有源光纤链路中,高阶色散导致的调制不稳定性,得出了调制不稳定性的增益谱. 相似文献
13.
基于块奇异值分解的水印算法研究 总被引：8，自引：0，他引：8
奇异值分解是一种特殊的矩阵变换，并具有良好的性质。本文充分利用奇异值分解的特性，提出了一种新的基于块奇异值分解的量化水印算法和一种新的基于块奇异值分解的扩频水印算法。这两个算法都是通过对各个数据块的最大奇异值进行修改来嵌入水印，都可以根据待嵌入的水印信息量来调整分块的大小，算法的复杂度较低。其中的量化水印算法是含边信息的嵌入方法，可以实现盲检测。实验结果证明，基于块奇异值分解的水印算法对常规的图像处理攻击具有很好的鲁棒性，尤其是其中的量化水印算法。 相似文献
14.
P. Usha Sarma P V G K Sarma Taruna Madan 《Indian journal of clinical biochemistry : IJCB》2000,15(1):43-50
Diseases caused by pathogenic filamentous fungi, are an emerging threat to public health in the wake of increasing incidence of HIV and tuberculosis. At this point, discovery and development of fungal therapeutics and diagnostics are serious challenges for biomedical researchers. Recent technological advances in genomics and proteomics offer great scope for development of preventive and therapeutic measures for fungal diseases.Aspergillus, one of the medically important filamentous pathogenic fungi causes a wide spectrum of clinical disorders ranging from allergic aspergillosis to systemic invasive aspergillosis. Increase in incidence of drug resistance and the cytotoxic effects are two serious limitations of the antifungal drugs presently in use. This is primarily due to lack of understanding of biological mechanisms operative in these fungi. Today, it is possible to understand the biological mechanisms of the fungus for its colonisation, survival and invasion of the host. Future developments based on such leads can result in development of precise and specific diagnostic, therapeutic and preventive measures for a wide clinical spectrum of fungal diseases. 相似文献
15.
介绍了信息融合技术在频谱管理领域中的发展现状,针对电磁频谱态势分析、干扰源查找等功能,重点介绍了信息融合技术在频谱管理系统中的应用情况,论述了频谱数据融合技术在频谱管理系统建设过程中的挑战和发展趋势。 相似文献
16.
敌杀死乳油混滑石粉防治马尾松毛虫浅试 总被引：1，自引：0，他引：1
发生马尾松毛虫虫害,生物防治是治理松毛虫、又保护生态环境的理想防治措施,如果生物制剂紧缺,或有的时间段受天气、温度、湿度的影响,不适宜使用生物制剂,那么化学防治就是保护松树的有效急救措施。敌杀死属拟除虫菊酯类杀虫剂,杀虫谱广,击倒速度快,对鳞翅目幼虫杀伤力大,试验以敌杀死乳油混滑石粉形成敌杀死粉剂,用动力喷粉机喷粉防治马尾松毛虫,旨在为马尾松毛虫化学防治技术的合理应用提供科学依据。 相似文献
17.
18.
浙江沿海地区近十年土地利用/覆盖变化遥感监测研究 总被引：6，自引：0，他引：6
土地利用/覆盖变化是全球变化领域的研究热点,深刻认识其规律是研究全球变化与环境响应机制关系的一个重要环节。本文采用陆地卫星1993年TM和2001年ETM＋两期遥感数据,基于光谱增强技术,运用多步骤分层专题信息提取的分类方法,研究了浙江沿海地区近十年间土地利用/覆盖方式的变化规律,初步分析了变化的原因和可能由此引发的环境问题。结果表明：过去十年浙江省沿海地区的土地利用/覆盖方式发生了显著变化,这些变化不仅表现在农业、林业、建设用地的数量增减上,还表现为不同类型的内部结构和空间分布的变化。 相似文献
19.
波谱学是化学、药学领域应用性极强的一门学科,而体现化合物波谱特性、规律的波谱数据表及经验公式是化合物结构解析的基础。目前高校的波谱学教材及教学,只侧重波谱学基本原理,完全忽略或只是支离碎片式地涉及少量的数据表和经验公式,导致学生在解谱实践中没有系统性的演算、推导和预测能力,其后续积累的经验也无法融入进完备的波谱数据表及经验公式系统,严重影响其解谱能力的提升。该项研究在对波谱学基本理论(以在四大光谱中占核心地位的核磁碳谱、氢谱为教学示范内容)进行浓缩型教学的前提基础上,将波谱学基本理论与波谱数据表、经验公式进行融合教学,用波谱学基本原理对数据表中的经验值范围、增量规律进行归纳、总结,并解析其中规律产生的原因,让学生理解性地学习和记忆各类化合物基团的经验值、增量范围和经验公式。 相似文献
20.
Kari Gwen Coleman 《Ethics and Information Technology》2001,3(4):247-265
Traditional approaches to computer ethics regard computers as tools, andfocus, therefore, on the ethics of their use. Alternatively, computer ethicsmight instead be understood as a study of the ethics of computationalagents, exploring, for example, the different characteristics and behaviorsthat might benefit such an agent in accomplishing its goals. In this paper,I identify a list of characteristics of computational agents that facilitatetheir pursuit of their end, and claim that these characteristics can beunderstood as virtues within a framework of virtue ethics. This frameworkincludes four broad categories – agentive, social, environmental, and moral– each of which can be understood as a spectrum of virtues rangingbetween two extreme subcategories. Although the use of a virtue frameworkis metaphorical rather than literal, I argue that by providing a frameworkfor identifying and critiquing assumptions about what a `good' computer is,a study of android arete provides focus and direction to the developmentof future computational agents. 相似文献