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41.
我国低温等离子体研究进展(Ⅰ) 总被引:7,自引:0,他引:7
低温等离子体物理与技术的研究在国内受到了越来越多的重视.在等离子体中发现的一些有趣的物理现象,如磁场重联、尘埃等离子体等,使人们对等离子体物理的研究掀起了新的热潮.在应用方面,几乎所有理工类实验室都有涉及低温等离子体技术的实验装置,这使得在我国低温等离子体应用方面的研究非常普及,包括微电子工业中的等离子体工艺,各种坚硬、耐腐蚀、耐摩擦材料的制备,纳米材料的制备,聚合物以及生物材料的表面改性,等等.随着低温等离子体技术的发展,低温等离子体的诊断技术也随之发展起来.文章简要地介绍了近几年来低温等离子体研究在我国的发展,介绍了一些有关低温等离子体的热点研究课题. 相似文献
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Endoscopic illumination systems conduct light down a built-in fibre-optic bundle to illuminate the object. Many modern endoscopes employ wide-field imaging optical systems and therefore require an illuminating beam of large divergence. This is commonly provided by placing a strong diverging lens at the far end of the fibre bundle, but it results in a poor uniformity of illumination in the object space. This paper describes the design of a telescopic illumination system to overcome this problem. 相似文献
45.
Jos A. Gmez-Pedrero Juan A. Quiroga M. Jos Terrn-Lpez Daniel Crespo 《Optics and Lasers in Engineering》2006,44(12):1297-1310
In this paper we present the application of a direct demodulation method for the measurement of surface topography by means of Shadow-Moiré. In our set-up, we use three LEDs (with green, red and blue peak wavelengths) to illuminate the grating. Due to the different position of these light sources, a polychromatic Shadow-Moiré fringe pattern is produced, which can be described as the superposition of three monochromatic (red, green and blue) fringe patterns. Taking the image of this polychromatic fringe pattern with a RGB CCD camera, we get a monochromatic fringe pattern stored at each RGB channel of the CCD. The direct demodulation algorithm employed uses these fringe patterns to calculate the wrapped phase map. After unwrapping the phase map using a standard multi-grid technique, we implemented an automatic procedure to detect the area of interest of the phase map by removing low modulation zones and to calculate the absolute value of the phase. In this way it is possible to determine the topography of a surface with a single RGB snapshot maintaining a simple experimental set-up, which is an important feature, especially for the study of dynamic phenomena such as deformations. We present the experimental results obtained after measuring different objects with both smooth and rough surface textures. 相似文献
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For the methylsilsesquioxane film whose optical birefringence is almost zero, it was recently reported that its vertical thermal expansion coefficient (CTE) was approximately one order of magnitude larger than the lateral CTE. Though the birefringence is not an absolute predictor of anisotropic behavior, the discrepancy in both the CTEs was so remarkable that it was essential to investigate whether the anisotropy was intrinsic property or not. If the effect of Poisson's ratio is considered in the calculation of the vertical CTE and when elastic modulus measured by surface acoustic wave spectroscopy is used in the assessment of the lateral CTE, both the CTEs are coincident with each other. Therefore, it can be concluded that the discrepancy in the CTEs can be attributed to a higher in‐plane polymer chain orientation but it can also arise from the misleadingly assumed modulus and Poisson's ratio. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3109–3120, 2006 相似文献
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Rostislav Vodák 《Mathematical Methods in the Applied Sciences》2007,30(1):43-75
We consider a sequence of curved rods which consist of isotropic material and which are clamped on the lower base or on both bases. We study the asymptotic behaviour of the stress tensor and displacement under the assumptions of linearized elasticity when the cross‐sectional diameter of the rods tends to zero and the body force is given in the particular form. The analysis covers the case of a non‐smooth limit line of centroids. We show how the body force and the choice of the approximating curved rods can affect the strong convergence and the limit form of the stress tensor for the curved rods clamped on both bases. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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用于频率合成器的低损耗声表面波滤波器 总被引:2,自引:2,他引:0
简述了产生声表面波滤波器插入损耗的主要机理和获得低损耗的原则;介绍了根据此原则对100~500MHz5种滤波器的研制过程和结果。实验表明,采用镜像阻抗连接换能器结构可达到3~4dB的低损耗,并成功地应用于频率合成器中。 相似文献
50.
微波BJT超宽带低噪声放大器的设计 总被引:3,自引:0,他引:3
本文给出了一种频带覆盖达10-1600MHz的微波BJT超宽带低噪声放大器的设计方法,从微波BJT的噪声模型出发,通过拟合50Ω源阻抗下微波BJT的噪声系数NF50和S参数来提取其噪声参数,然后根据增益,噪声及驻波比要求优化设计放大器,使放大器在超宽带范围内获得平坦增益和低噪声,本文所给出的微波BJT惨数提取及放大器优化设计方法已由实验结果所验证。 相似文献