结合阈值去噪与边缘优化的图像增强算法

针对图像在传输过程中容易出现干扰的问题,该文通过研究图像的增强技术,通过对比分析,提出了一种结合阈值去噪与边缘优化的图像增强算法,该算法结合小波Contourlet 变换与人眼的视觉固有特性,有效地对分解后的图像系数进行分类,并结合改进边缘优化算法的增益因子来优化边缘区信号;而非边缘区采用改进后的软阈值去噪算法进行去噪处理.经实验,该算法具有准确性高与去噪能力强的特性,能够在去噪的同时有效保护边缘信号,与预期目标相符,具有一定的实用价值.     

适用于抑制非平稳背景噪声的语音增强算法

1.引言 随着移动多媒体电话的问世,人们打手机的方式将要发生改变:手持电话通话的情形将会越来越少,而人们可以更多地与屏幕进行互动交流.免提电话设备使人们在通话的同时可以享受这种互动.诸多文献[1-3]中介绍了采用各种语音增强技术解决免提电话设备研制中的基本问题:传声器(话筒)远离说话者引起语音信噪比的下降.     

级联型波导中古斯-汉欣位移的增强

前期的工作已经证明,由于共振效应和渗透深度的增加,利用毫米尺度对称金属包覆波导和自由空间耦合技术,可获得毫米量级的古斯 -汉欣(Goos-H.nchen)位移。本文在此基础上,利用一对对称金属包覆波导组成级联型结构,研究了这种结构中古斯 -汉欣位移的增强效应。实验结果表明：当激光波长变化 43 pm时,由 CCD探测器测量得到的古斯 -汉欣位移达到了 2 215 μm,约为单级波导古斯 -汉欣位移的 2倍,实验结果与理论推导完全一致。     

A Photographic Encoder Applied to an Optical Processor Using Speckle Techniques

Abstract

An artificial screen has been constructed to encode spatial information of simple transparent objects. The constructed encoder is composed of a matrix of small strips, photographed several times on a high resolution film to obtain strips of nearly ten times the average grain size of natural speckles. A second encoder has been constructed by recording a natural speckle pattern on a photographic plate which has gone through a continuous shift during the time of exposure in a specific direction, forming an elongated speckle pattern. A comparison between the results obtained using the two encoders has been presented.     

互编织式光纤管道形变传感器

设计了一种基于光纤微弯理论的管道形变传感器。它不需外加变形装置,而仅由两根光纤相互编织形成微弯,实现对形变的传感功能。经理论研究和数值分析表明,它可对管道变进行实时监测,具有较大的应用价值。     

Enhancement of Goos-H(a)nchen Shift with Cascade Optical Waveguides

前期的工作已经证明,由于共振效应和渗透深度的增加,利用毫米尺度对称金属包覆波导和自由空间耦合技术,可获得毫米量级的古斯-汉欣(Goos-H(a)nchen)位移.本文在此基础上,利用一对对称金属包覆波导组成级联型结构,研究了这种结构中古斯-汉欣位移的增强效应.实验结果表明:当激光波长变化43 pm时,由CCD探测器测量得到的古斯-汉欣位移达到了2 215 μm,约为单级波导古斯-汉欣位移的2倍,实验结果与理论推导完全一致.     

An Optical Lock-in Technique as Applied to an Acousto-optic Integrated Spectrum Analyser

Abstract

A new signal coding technique is presented here for use with the existing integrated optical spectrum analyser structure. Modifications to the basic device are implemented, and shown to have a theoretical and an experimental dynamic range increase of 10–20 decibels (dB). Such an increase would bring the overall device dynamic range to 40–50 dB.     

自相似业务下光分组交换边缘节点排队方案性能分析

研究了自相似业务下光分组交换网中边缘节点的工作性能,建立了轮询机制下的排队模型,分析了平均组装／发送时延与最大汇聚分组长度等参数的关系。研究表明：平均时延与最大汇聚长度及边缘节点数目成线性关系,与发射速率成反比关系,随业务强度的增加而增大。所得结论具有轮询机制的共性,为进一步研究其他排队方案奠定了基础。     

绿色背景下可见光-近红外与热辐射波段具备特征反射光谱薄膜的研究

分析了白天以绿色植物为背景的地物在可见光-近红外和中远红外波段辐射特性的差异, 发现应该采用不同的原理对可见光-近红外和中远红外进行隐身。在此基础上分析了传统涂料和光子晶体结构在多波段兼容隐身的缺陷, 提出运用多层薄膜结构来实现兼容隐身, 研究设计了具备特征光谱的多层薄膜。该膜系在可见光-近红外波段具有与一般绿色植物相似的反射光谱特征, 可以模拟绿色植物光学亮度特性, 并且在中远红外大气窗口内的平均发射率分别为0.232和0.195, 可以在一定程度上抑制目标的热辐射。     

Dynamic Range Enhancement for Pure Rotational Coherent Anti-Stokes Raman Scattering Thermometry by use of an Optical Arrangement with Two Dye Lasers

A disadvantage of pure rotational coherent anti-Stokes Raman scattering (CARS) compared with vibrational CARS is the limited dynamic range for temperature measurements. Here an optical configuration is described that overcomes this limitation by the use of two different center-frequency dye lasers in a dual-broadband CARS approach. Its performance is demonstrated for simultaneous pure rotational CARS temperature and relative N(2)-O(2)concentration measurements up to 1950 K at ambient pressure.     

Some Phenomena Connected with the Optical Monitoring of Thin-film Deposition,and Their Application to Optical Coatings

It is shown that a combination of two dielectric layers, each with an optical thickness of less than a quarter-wave, behaves to a great extent as one quarter-wave layer.     

圆环钎焊蜂窝结构超声C扫描检测及其系统研制

利用直接数字成像和程控采样扫描技术，研制成了圆环蜂窝构件超声Ｃ扫描检测系统，精确地将蜂窝构件检测结果分析处理后直接显示在微机终端屏幕。     

Minimum Variance Beamforming Combined with Adaptive Coherence Weighting Applied to Medical Ultrasound Imaging

Currently, the nonadaptive delay-and-sum (DAS) beamformer is used in medical ultrasound imaging. However, due to its data-independent nature, DAS leads to images with limited resolution and contrast. In this paper, an adaptive minimum variance (MV)-based beamformer that combines the MV and coherence factor (CF) weighting is introduced and adapted to medical ultrasound imaging. MV-adaptive beamformers can improve the image quality in terms of resolution and sidelobes by suppressing off-axis signals, while keeping onaxis ones. In addition, CF weighting can improve contrast and sidelobes by emphasizing the in-phase signals and reducing the out-of-phase ones. Combining MV and CF weighting results in simultaneous improvement of imaging resolution and contrast, outperforming both DAS and MV beamformers. In addition, because of the power of CF in reducing the focusing errors, the proposed method presents satisfactory robustness against sound velocity inhomogeneities, outperforming the regularized MV beamformer. The excellent performance of the proposed beamforming approach is demonstrated by several simulated examples.     

Photothermal Techniques Applied to the Thermal and Optical Characterization of <Emphasis Type="Italic">Curcuma longa</Emphasis>

In recent years, has been reported an increasing interest to study vegetables and fruits in order to know their benefits to prevent different types of health problems. Curcuma longa has a great potential to prevent diseases as different types of cancer. In the present study, C. longa samples, of different trademarks, were optically and thermally characterized by using photoacoustic spectroscopy and photopyroelectric techniques, obtaining their optical absorption spectra, optical absorption length spectra, the thermal diffusivity, effusivity, conductivity and heat capacity per unit volume, observing optical absorptions corresponding to antioxidant elements, reported such as beneficial for health. These properties also could be important in the food industry for the commercialization of functional foods.     

Optical properties of dense regular cermets with relevance to selective solar absorbers

As thin films applied to metal substrates, certain cermets form selective surfaces of high solar absorptance and low thermal emittance. A prediction of the optical constants of cermets is valuable in the choosing of a combination of metal and ceramic and in the optimization of the grading profile. The metallic inclusions are in general densely packed, and only those theories which include the effects of proximity are capable of yielding correct values. In order to complement previous work on the optical and transport properties of regular arrays of spheres, we solved the problem of cylindrical inclusions arranged in a square lattice. The calculations were checked by comparison with measurements for perfectly conducting cylinders. The optical constants of gold cylinders in alumina were calculated and were compared with those for spherical inclusions. It is shown that proximity effects are more pronounced for cylinders than for spheres. For the cases of cylindrical and spherical voids in a highly conducting medium it is shown that the Maxwell-Garnett theory is accurate to within 2% for volume fractions of voids up to 0.50 and 0.40 respectively.     

Fictitious Notch Rounding Concept Applied to V-Notches with End Holes Under Mode I Loading

Taking advantage of some recent closed form expressions for the stress distributions due to V-notches with end holes, the micro-structural support factor, s, to apply the Fictitious Notch Rounding (NFR) approach, is evaluated by adopting a normal stress criterion. The closed form expressions for the micro-structural support factor (s) as well as for the fictitiously enlarged end radius (ρ _f), provided here for the first time, highlight the crucial role played by the notch opening angle for this notch configuration.