共查询到20条相似文献，搜索用时 31 毫秒
1.
A large number of computer vision algorithms for finding intensity edges, computing motion, depth, and color, and recovering the three-dimensional shape of objects have been developed within the framework of minimizing an associated "energy" or "cost" functional. Particularly successful has been the introduction of binary variables coding for discontinuities in intensity, optical flow field, depth, and other variables, allowing image segmentation to occur in these modalities. The associated nonconvex variational functionals can be mapped onto analog, resistive networks, such that the stationary voltage distribution in the network corresponds to a minimum of the functional. The performance of an experimental analog very-large-scale integration (VLSI) circuit implementing the nonlinear resistive network for the problem of two-dimensional surface interpolation in the presence of discontinuities is demonstrated; this circuit is implemented in complementary metal oxide semiconductor technology. 相似文献
2.
2010-2011年,在黄土丘陵缓坡地上对旱地马铃薯全膜双垄覆盖"一膜两季"免耕栽培模式效益进行定位研究。结果发现,拆除第一季地膜,双垄全膜覆盖栽培大垄侧种植马铃薯产量最高,是获得高产的首选方法。但高产不一定能高收,马铃薯双垄全膜覆盖"一膜两季"免耕栽培最具有节本增效性能,它能很好地减少生产投入,提高投产比,应在"一膜两季"栽培中大面积推广应用。拆除第一季地膜,双垄全膜覆盖沟播栽培节本增效性能最差,生产中不提倡应用。 相似文献
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The development of an in-field plant sensing system for a site-specific application can protect the environment from excessive chemicals and save management cost while maintaining productivity. A multi-spectral imaging sensor has been introduced and widely used for in-field plant sensing. In order for a robust performance of the spectral imaging sensor under changes in ambient illumination, image quality must be maintained for proper spectral image analysis. Image formation that is affected by camera parameters was identified, and a controller was developed to compensate varying image intensity and to obtain the desired image quality. A fuzzy logic control algorithm was applied to automatically adjust the camera exposure and gain to control image brightness within a targeted gray level. Slow convergence and oscillation were regulated by dynamic membership functions with different weights in each image channel. Images affected by illumination disturbance quickly converged into a desired brightness image within a maximum of five iterations over the entire range of camera gains in all three spectral image channels. An application of in-field plant sensing using the fuzzy logic image controller was evaluated on corn crops for nitrogen detection. The normalized spectral response of the sensor was inversely correlated to a chlorophyll meter with −0.93 and −0.88 in red and green channels, respectively. The development of an image quality controller using fuzzy logic enhanced the reliable performance of the in-field plant sensing system. 相似文献
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In this paper, a new method to fuse low resolution multispectral and high resolution RGB images is introduced, in order to detect Gramineae weed in rice fields with plants at 50 days after emergence (DAE).The images are taken from a fixed-wing unmanned aerial vehicle (UAV) at 60 and 70 m altitude. The proposed method combines the texture information given by a high resolution red–green–blue (RGB) image and the reflectance information given by a low resolution multispectral (MS) image, to obtain a fused RGB-MS image with better weed discrimination features. After analyzing the normalized difference vegetation index (NDVI) and normalized green red difference index (NGRDI) for weed detection, it was found that NGRDI presents better features. The fusion method consists of decomposing the RGB image using the intensity, hue and saturation (IHS) transformation, then, a second order Haar wavelet transformation is applied to the intensity layer (I) and the NGRDI image. From this transformation, the low–low (LL) coefficients of the NGRDI image are replaced by the LL coefficients of the I layer. Finally, the fused image is obtained by transforming the new wavelet coefficients to RGB space. To test the method, a one hectare experimental plot with rice plants at 50 DAE with Gramineae weeds was selected. Additionally, to compare the performance of the method, two indices were used, specifically, the M/MGT index which is the percentage of detected weed area, and the MP index which indicates the precision of weed detection. These indices were evaluated in four validation zones using three Neural Networks (NN) detection systems based on three types of images; namely, RGB, RGB + NGRDI, and fused RGB-NGRDI. The best weed detection performance was obtained by the NN with the fused image, with M/MGT index between 80 and 108% and MP between 70 and 85%. 相似文献
5.
[目的]改善吸水树脂的综合性能,降低产品的生产成本。[方法]以淀粉、丙烯酸和钠基膨润土为主要原料,过硫酸铵为引发剂,N,N-亚甲基双丙烯酰胺为交联剂,采用水溶液法制备出高吸水树脂;通过单因素试验研究反应丙烯酸/淀粉比值、丙烯酸中和度、反应温度以及膨润土的添加量对高吸水树脂吸水性能的影响。[结果]最佳聚合反应条件为：丙烯酸和淀粉比为4∶1,丙烯酸的中和度为80%,交联剂用量0.05%,引发剂用量0.45%,反应温度60℃,膨润土用量7%。在此最佳条件下,树脂的吸水倍率达585 g/g。红外光谱和扫描电镜分析表明,膨润土与淀粉丙烯酸等单体复合得很好。[结论]膨润土的加入,不仅改善了高吸水性树脂的性能,而且也大大降低了制备成本。 相似文献
6.
马磊 《信阳农业高等专科学校学报》2012,22(4)
在现代品牌策划视野下,标志设计不再是纯粹的视觉表现,而是企业品牌形象的高度浓缩。本文围绕"对谁传达?"传达什么?"怎样传达?"三个层面,对标志设计进行探讨和分析。 相似文献
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Observations of intermolecular excimers in several pi-conjugated polymers and exciplexes of these polymers with tris(p-tolyl) amine are reported. It is shown that the luminescence of conjugated polymer thin films originates from excimer emission and that the generally low quantum yield is the result of self-quenching. Thus, in sufficiently dilute solution, the "single-chain" emission has a quantum yield of unity. Exciplex luminescence and exciplex-mediated charge photogeneration have much higher quantum yields than the excimer-mediated photophysical processes. These results provide a basis for understanding and controlling the photophysics of conjugated polymers in terms of supramolecular structure and morphology. 相似文献
9.
Reiss H 《Science (New York, N.Y.)》1987,238(4832):1368-1373
The mechanism of formation of polymer molecules in the gas phase is difficult to study because the involatile polymers tend to condense out of that phase. However, new techniques, involving the use of cloud chambers, have enabled workers to use the nucleation of liquid drops in supersaturated monomer vapors to detect single polymer molecules and therefore to work with so few simultaneously growing polymers that aggregation and condensation are avoided. Chain polymerization in which the chain carriers are either radicals or ions can therefore be studied in the vapor. Furthermore, the ability to work with such small concentrations of growing polymeric radicals, for example, makes it possible to avoid encounters between them that lead to recombination and the formation of "dead" polymers that are incapable of further growth. Many aspects of gas-phase polymerization can be studied including, besides radical and ion chains, ring-opening polymerization, initiation, radiation-induced polymerization, and especially "ultraslow" chemistry. 相似文献
10.
A synthetic pathway is described to construct "in bulk" two-dimensional (2D) polymers shaped as molecular sheets. A chiral oligomeric precursor is used that contains two reactive sites, a polymerizable group at one terminus and a reactive stereogenic center near the middle of the molecule. The bulk reaction yields bilayer 2D polymers of molecular weight in the order of millions and a monodisperse thickness of 50.2 angstroms. The 2D molecular objects form through molecular recognition by the oligomers, which self-organize into layers that place the reactive groups within specific planes. The oligomers become catenated by two different stitching reactions involving the reactive sites. At room temperature, stacks of these molecular objects can organize as single crystals and at higher temperatures melt into smectic liquid crystals. Nonlinear optical experiments reveal that solid films containing the 2D polymers form structures that are thermally and temporally more stable than those containing analogous 1D polymers. This observation suggests that the transformation of common polymers from a 1D to a 2D architecture may produce generations of organic materials with improved properties. 相似文献
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Lu W Fadeev AG Qi B Smela E Mattes BR Ding J Spinks GM Mazurkiewicz J Zhou D Wallace GG MacFarlane DR Forsyth SA Forsyth M 《Science (New York, N.Y.)》2002,297(5583):983-987
pi-Conjugated polymers that are electrochemically cycled in ionic liquids have enhanced lifetimes without failure (up to 1 million cycles) and fast cycle switching speeds (100 ms). We report results for electrochemical mechanical actuators, electrochromic windows, and numeric displays made from three types of pi-conjugated polymers: polyaniline, polypyrrole, and polythiophene. Experiments were performed under ambient conditions, yet the polymers showed negligible loss in electroactivity. These performance advantages were obtained by using environmentally stable, room-temperature ionic liquids composed of 1-butyl-3-methyl imidazolium cations together with anions such as tetrafluoroborate or hexafluorophosphate. 相似文献
13.
在医学领域,黄斑厚度可以用来量化糖尿病黄斑水肿和年龄相关性黄斑变性等疾病,临床上通常使用光学相干断层扫描的影像技术来获取黄斑图像。但现有的黄斑图像分割方法运算速度较慢,阻碍了其临床使用。本文提出一种新的基于多分辨率及水平集的黄斑图像分割方法,首先使用高斯滤波对原始图像按行进行滤波,再运用多分辨率方法获取图像初始局部轮廓,最后使用水平集方法可以快速获取黄斑图像的中间轮廓,得到最终的图像分割结果。通过在311幅黄斑图像的仿真实验对比,本文方法在边缘检测结果和运算速度上比传统方法有很大改进。 相似文献
14.
介绍了国内外专家系统在园艺植物方面的应用,提出了其发展过程中仍存在的问题,如知识获取的"瓶颈"问题、园艺植物专家系统性能较差、未形成成熟的园艺植物病虫害诊断知识的知识模型、未能从诊断推理思维方式出发建立园艺植物病虫害诊断知识的推理求解模型、缺乏系统应用效果的反馈、专家系统的商业性较差和农业专家系统的开发平台需要进一步研发等。展望了农业专家系统的发展趋势:利用"3S"、模型模拟、智能决策、多媒体技术等多技术的集成开发园艺植物专家系统;开发综合性农业专家系统;注重实用性,开发不同用户群体、不同层面的专家系统;利用图像识别检索等人工智能手段进行病虫害诊断。 相似文献
15.
Park HB Jung CH Lee YM Hill AJ Pas SJ Mudie ST Van Wagner E Freeman BD Cookson DJ 《Science (New York, N.Y.)》2007,318(5848):254-258
Within a polymer film, free-volume elements such as pores and channels typically have a wide range of sizes and topologies. This broad range of free-volume element sizes compromises a polymer's ability to perform molecular separations. We demonstrated free-volume structures in dense vitreous polymers that enable outstanding molecular and ionic transport and separation performance that surpasses the limits of conventional polymers. The unusual microstructure in these materials can be systematically tailored by thermally driven segment rearrangement. Free-volume topologies can be tailored by controlling the degree of rearrangement, flexibility of the original chain, and judicious inclusion of small templating molecules. This rational tailoring of free-volume element architecture provides a route for preparing high-performance polymers for molecular-scale separations. 相似文献
16.
图像的能量主要集中在高频部分,传统的小波变换图像编码压缩方法主要侧重低频信号,而把高频部分看为不重要的信息,这就导致图像的细节失真。考虑到图像能量分布情况,提出以对数熵为代价函数,选择最优小波包树的图像编码压缩方法,仿真结果表明这种方法不仅可以提高的压缩比,而且重构的图像效果比较好。 相似文献
17.
计算机视觉技术在水果品质检测中的研究进展 总被引：3，自引：0，他引：3
水果的品质检测是水果分级的重要依据。随着计算机和图像处理技术的发展、计算机硬件成本的下降和性能的提升,计算机视觉检测技术在水果品质检测方面获得了越来越多的应用。为了能充分利用最新研究成果,该文从计算机视觉技术在水果外观品质和内部品质的检测两个方面,分别综述了国内外的研究进展,并对其发展方向进行了展望,以供我国研究人员做同类研究时参考。 相似文献
18.
Verbiest T Burland DM Jurich MC Lee VY Miller RD Volksen W 《Science (New York, N.Y.)》1995,268(5217):1604-1606
The thermal stability of the electric field induced poled order in a new class of second-order optically nonlinear polymers, "donor-imbedded" side-chain polyimides containing no flexible connectors or tethers to the nonlinear optical (NLO) chromophore, is investigated. In these polymers, the electron-donor part of the chromophore is a diaryl-substituted amine that is incorporated as a part of the polymer backbone. The donorimbedded systems used in this study have exceptional chemical stabilities at elevated temperatures (350 degrees C) and impressive poled order stability at extremely high temperatures (300 degrees C). In both respects, they were significantly more stable than a true side-chain polyimide with a similar NLO-active chromophore covalently linked to the polymer backbone by a flexible tether group. 相似文献
19.
基于卷积神经网络的葡萄叶片病害检测方法 总被引：5，自引：0，他引：5
文章采用多角度建议区域Faster-RCNN准确定位图像中葡萄叶片,提出一种基于卷积神经网络的病害检测方法,检测图像叶片病害。相比直接检测图像病害,可去除背景因素对病害区域干扰,降低错误率。结果表明,该算法对自然条件下葡萄病害成像适应性良好。文章统计6种不同条件下拍摄图像,对一般叶片检测算法平均mAP为75.52%,显著高于传统算法。在病害检测时,采用两种策略:从一幅图像中检测到每个单个叶片,或将整幅图像对叶片取掩模后,作为下一级病害检测器输入图像。结果表明,第一种方法,6种常见葡萄病害平均mAP为66.47%,其中褐斑病与白粉病mAP超过70%;第二种方法,病害检测平均mAP为51.44%,但平均检测时间节约75%。两种方法性能均优于在原始图像上直接病害检测方法。 相似文献
20.
In conjugated polymers, radiative recombination of excitons (electron-hole pairs) competes with nonradiative thermal relaxation pathways. We visualized exciton quenching induced by hole polarons in single-polymer chains in a device geometry. The distance-scale for quenching was measured by means of a new subdiffraction, single-molecule technique--bias-modulated intensity centroid spectroscopy--which allowed the extraction of a mean centroid shift of 14 nanometers for highly ordered, single-polymer nanodomains. This shift requires energy transfer over distances an order of magnitude greater than previously reported for bulk conjugated polymers and far greater than predicted by the standard mechanism for exciton quenching, the unbiased diffusion of free excitons to quenching sites. Instead, multistep "energy funneling" to trapped, localized polarons is the probable mechanism for polaron-induced exciton quenching. 相似文献