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1.
Haotian Wu Guo Dong Bai Shuo Liu Lianlin Li Xiang Wan Qiang Cheng Tie Jun Cui 《国家科学评论(英文版)》2020,7(3):561
We propose a theory to characterize the information and information processing abilities of metasurfaces, and demonstrate the relation between the information of the metasurface and its radiation pattern in the far-field region. By incorporating a general aperture model with uncertainty relation in L2-space, we propose a theory to predict the upper bound of information contained in the radiation pattern of a metasurface, and reveal the theoretical upper limit of orthogonal radiation states. The proposed theory also provides guidance for inverse design of the metasurface with respect to given functionalities. Through investigation of the information of disordered-phase modulated metasurfaces, we find the information invariance (1−γ, where γ is Euler''s constant) of chaotic radiation patterns. That is to say, the information of the disordered-phase modulated radiation patterns is always equal to 1−γ, regardless of variations in size, the number of elements and the phase pattern of metasurface. This value might be the lower bound of radiation-pattern information of the metasurface, which can provide a theoretical limit for information modulation applications, including computational imaging, stealth technologies and wireless communications. 相似文献
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Jie Zhao Xi Yang Jun Yan Dai Qiang Cheng Xiang Li Ning Hua Qi Jun Chen Ke Guo Dong Bai Shuo Liu Shi Jin Andrea Al Tie Jun Cui 《国家科学评论(英文版)》2019,6(2):231
Optical non-linear phenomena are typically observed in natural materials interacting with light at high intensities, and they benefit a diverse range of applications from communication to sensing. However, controlling harmonic conversion with high efficiency and flexibility remains a major issue in modern optical and radio-frequency systems. Here, we introduce a dynamic time-domain digital-coding metasurface that enables efficient manipulation of spectral harmonic distribution. By dynamically modulating the local phase of the surface reflectivity, we achieve accurate control of different harmonics in a highly programmable and dynamic fashion, enabling unusual responses, such as velocity illusion. As a relevant application, we propose and realize a novel architecture for wireless communication systems based on the time-domain digital-coding metasurface, which largely simplifies the architecture of modern communication systems, at the same time yielding excellent performance for real-time signal transmission. The presented work, from new concept to new system, opens new pathways in the application of metamaterials to practical technology. 相似文献
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Francesca Sapuppo Andreu Llobera Florinda Schembri Marcos Intaglietta Victor J. Cadarso Maide Bucolo 《Biomicrofluidics》2010,4(2)
We describe design and miniaturization of a polymeric optical interface for flow monitoring in biomicrofluidics applications based on polydimethylsiloxane technology, providing optical transparency and compatibility with biological tissues. Design and ray tracing simulation are presented as well as device realization and optical analysis of flow dynamics in microscopic blood vessels. Optics characterization of this polymeric microinterface in dynamic experimental conditions provides a proof of concept for the application of the device to two-phase flow monitoring in both in vitro experiments and in vivo microcirculation investigations. This technology supports the study of in vitro and in vivo microfluidic systems. It yields simultaneous optical measurements, allowing for continuous monitoring of flow. This development, integrating a well-known and widely used optical flow monitoring systems, provides a disposable interface between live mammalian tissues and microfluidic devices making them accessible to detection∕processing technology, in support or replacing standard intravital microscopy. 相似文献
4.
Hao Chi Zhang Tie Jun Cui Yu Luo Jingjing Zhang Jie Xu Pei Hang He Le Peng Zhang 《国家科学评论(英文版)》2020,7(2):261
Digital coding and digital modulation are the foundation of modern information science. The combination of digital technology with metamaterials provides a powerful scheme for spatial and temporal controls of electromagnetic waves. Such a technique, however, has thus far been limited to the control of free-space light. Its application to plasmonics to shape subwavelength fields still remains elusive. Here, we report the design and experimental realization of a tunable conformal plasmonic metasurface, which is capable of digitally coding and modulating designer surface plasmons at the deep-subwavelength scale. Based on dynamical switching between two discrete dispersion states in a controlled manner, we achieve digital modulations of both amplitude and phase of surface waves with nearly 100% modulation depth on a single device. Our study not only introduces a new approach for active dispersion engineering, but also constitutes an important step towards the realization of subwavelength integrated plasmonic circuits. 相似文献
5.
提出了一种提升小波变换和DCT变换相结合的图像融合算法。这种算法并不依赖于对方差,而是直接使用DCT变化和小波变化分别对高频部分、低频部分进行特征提取。实验表明,这种新的融合技术与传统算法相比,不但提高了图像的信噪比,更加保留了边缘的信息细节,同时也提高了处理效率,减少了使用时间,具有较高得实用价值。 相似文献
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光电信息技术是由光学、光电子、微电子等技术结合而成的多学科综合技术,涉及光信息的辐射、传输、探测以及光电信息的转换、存储、处理与显示等众多的内容。在现有条件下,如何突破现行课程对学生理论分析能力和感性认识培养的不足,从而提高学生动手能力,真正提升学生的工作能力和创新能力,以适应信息时代的发展要求,是值得研究的课题。文章根据光电信息技术整个课程群特点,在教学内容的组织安排、教学形式与提高教师的教学和科研能力方面进行了一系列改进与探索,取得了良好的教学效果和实践成效。 相似文献
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In this work, we report a system-level integration of portable microscopy and microfluidics for the realization of optofluidic imaging flow analyzer with a throughput of 450 cells/s. With the use of a cellphone augmented with off-the-shelf optical components and custom designed microfluidics, we demonstrate a portable optofluidic imaging flow analyzer. A multiple microfluidic channel geometry was employed to demonstrate the enhancement of throughput in the context of low frame-rate imaging systems. Using the cell-phone based digital imaging flow analyzer, we have imaged yeast cells present in a suspension. By digitally processing the recorded videos of the flow stream on the cellphone, we demonstrated an automated cell viability assessment of the yeast cell population. In addition, we also demonstrate the suitability of the system for blood cell counting. 相似文献
9.
图像处理就是利用计算机及其有关技术,对图像进行运算和处理,可以使图像更清晰,从图像中提取某些特定的信息,从而达到某种特定目的,随着计算机技术的发展,图像识别技术获得了越来越广泛的应用。文章采用灰度化、消噪等方法对图像进行预处理,采用边缘提取、形态学处理、字符定位等方法实现图像字符特征提取,通过Matlab软件编写字符识别程序,实现图像字符识别。研究结果表明,采用图像处理可有效实现对图像字符的识别。 相似文献
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Microfluidic techniques have been recently developed for cell-based assays. In microfluidic systems, the objective is for these microenvironments to mimic in vivo surroundings. With advantageous characteristics such as optical transparency and the capability for automating protocols, different types of cells can be cultured, screened, and monitored in real time to systematically investigate their morphology and functions under well-controlled microenvironments in response to various stimuli. Recently, the study of stem cells using microfluidic platforms has attracted considerable interest. Even though stem cells have been studied extensively using bench-top systems, an understanding of their behavior in in vivo-like microenvironments which stimulate cell proliferation and differentiation is still lacking. In this paper, recent cell studies using microfluidic systems are first introduced. The various miniature systems for cell culture, sorting and isolation, and stimulation are then systematically reviewed. The main focus of this review is on papers published in recent years studying stem cells by using microfluidic technology. This review aims to provide experts in microfluidics an overview of various microfluidic systems for stem cell research. 相似文献
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图像增强是图像边缘检测、分割以及特征提取等技术的基础,数字图像增强的方法有频域处理法与空域处理法,本文主要介绍空域处理中的灰度变换方法和直方图均衡法。文章首先分析了它们的原理,然后通过MATLAB软件分别用这两种方法对图像进行处理,处理后使图像的对比度得到了明显的改善,增强了图像的视觉效果。 相似文献
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本文介绍了一种针对化学数据分析的挖掘系统原型实现和设计理论。阐述从化学数据分析的角度开发一个联机分析数据挖掘系统原型的理论过程，研究过程采用数据仓库提供的OLAP技术进行关联规则挖掘，提供了一种数据项的二进制编码技术，对于提高数据信息的处理能力和可靠性有一定意义。预期实现从各种文献资料或数据库自动抽取有关化学反应的信息，发现新的有用化学成分，完成合成设计和反应预测等功能，从而对数据挖掘的实现进行了有益的尝试。 相似文献
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机载激光雷达（LiDAR）技术及其应用 总被引：3，自引：0，他引：3
机载LiDAR技术是一种应用越来越广泛的新型测量系统,能够快速地获取高精度三维数据。过去十年,机载LiDAR技术作为精确、快速的地球表面三维测量方法已得到广泛认同。本文介绍了机载LiDAR技术的基本原理、数据处理流程及其应用。 相似文献
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技术创新网络对于分析和了解创新技术领域的发展演化情况,观察企业间技术合作创新和差异化竞争等具有重要意义。本文采用专利计量方法,对该领域近三十年间专利数据进行分析。借助专利耦合方法和社会网络分析方法,研究电动汽车领域技术相似创新网络的结构特征演化和技术合作创新网络的演化。并将分析结果可视化,得出该领域的技术发展热点和趋势、具有代表性的企业,以及企业之间的合作变化。结果表明,电动汽车技术集中在电池、电机、控制器和整车技术三大类上,并有均衡发展的趋势,企业间技术合作愈加密切,竞争也愈加激烈。 相似文献
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目前,实现对细胞神经递质释放过程的高时空分辨实时监测,仍存在诸多挑战。近些年来,通过发展不同的电化学检测技术实现了对细胞胞吐(exocytosis)释放以及细胞内部囊泡的定量化分析;一些研究使用这些技术,进行了细胞释放模式的探究。通过在电极表面修饰小分子或者调控电极尺寸,可实现高分辨率和高灵敏度的监测。文章重点介绍了神经递质电化学检测的机理、微米电极以及纳米电极检测技术的发展,对电化学传感与成像技术的联用进行了评述,并对电化学传感检测技术未来发展方向进行了展望。在此基础上,文章综合各种不同监测技术的优点,提出构建纳米电极与成像以及其他检测手段的联用技术,以大幅提高纳米电极在神经递质检测方面的能力。 相似文献
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在光学系统中,SOI(绝缘体上的半导体)上制备集成的MMI(多模干涉)型光耦合器已成为一种愈来愈引人注目的无源器件.由于Si和SiO2 之间具有大的折射率差,在SOI波导中可以采用SiO2 薄膜( <1.0 μm)作限制层,这与超大规模集成电路工艺相兼容.描述了采用SOI技术制备集成的MMI型光耦合器和光开关的设计和制造结果.业已证实,2× 2MMI MZI(多模干涉 麦赫 曾德干涉)型热光开关的开关时间小于 2 0 μs. 相似文献
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《普罗米修斯》2012,30(3):211-222
Globalisation is a term too easily used without reference to the basic enabling role of technology. It is the interplay between available technology and the prevailing social processes, especially dominant institutional forms, which has essentially determined the long process of globalisation. This process has gone through phases exhibiting varying core characteristics as production, transport and communications technologies especially have interrelated with the institutional structures of nation states, military forces and firms especially. However, a general trend to geographical and tendentially global expansion has been constant, along with an intensification of information processing and communications capacity. The role of technology has been to enable this physical expansion culminating in globalisation, including the techno-industrial capacity that increasingly drove it through the construction of better and cheaper artefacts. 相似文献
18.
Ram M. Narayanan 《Journal of The Franklin Institute》2008,345(6):659-678
This paper examines the results of our research on the use of ultrawideband noise waveforms for imaging objects behind walls. The advantages of using thermally generated noise as a probing signal are introduced. The technique of heterodyne correlation used to inject coherence in the random noise probing signal and to collapse the wideband reflected signal into a single frequency are presented. Central to successful imaging through building walls is the characterization of the wideband propagation properties of wall materials and these are discussed. The basic concepts of synthetic aperture radar image formation using noise waveforms and the unique problems associated with the random nature of the transmit waveform are analyzed. We also address issues related to locating, detection, and tracking humans behind walls, using new tools for human activity characterization, namely the Hilbert-Huang Transform approach. The results indicate that noise radar technology combined with modern signal processing approaches is indeed a viable technique for covert high-resolution imaging of obscured stationary and moving targets. 相似文献
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《Journal of The Franklin Institute》2007,344(3-4):312-348
Mammography is the best available tool for screening for the early detection of breast cancer. Mammographic screening has been shown to be effective in reducing breast cancer mortality rates: screening programs have reduced mortality rates by 30–70%.Mammograms are difficult to interpret, especially in the screening context. The sensitivity of screening mammography is affected by image quality and the radiologist's level of expertise. Computer-aided diagnosis (CAD) technology can improve the performance of radiologists, by increasing sensitivity to rates comparable to those obtained by double reading, in a cost-effective manner. Current research is directed toward the development of digital imaging and image analysis systems that can detect mammographic features, classify them, and provide visual prompts to the radiologist.Radiologists would like the ability to change the contrast of a mammogram, either manually or with pre-selected settings. Computer techniques for detecting, classifying, and annotating diagnostic features on the images would be desirable. This paper presents an overview of digital image processing and pattern analysis techniques to address several areas in CAD of breast cancer, including: contrast enhancement, detection and analysis of calcifications, detection and analysis of masses and tumors, analysis of bilateral asymmetry, and detection of architectural distortion. Although a few commercial CAD systems have been released, the detection of subtle signs of breast cancer such as global bilateral asymmetry and focal architectural distortion remains a difficult problem. We present some of our recent works on the development of image processing and pattern analysis techniques for these applications. 相似文献