51 resultados para Spada, Lionello, 1576-1622


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基于分析势函数的二次变分,从理论上证明了固体材料不稳定性主要取决于材质不断退化的重要特征。另一特征是,材料往往会由基本变形路径漂移为一个轴向应变被限定的模态以至失稳。文中以有限元方法计算模拟受周期性分布孔洞损伤的平面板材模型,结果显示,孔周边的应变局部化使变形路径转移到一个轴向应变被限定的失效模态。此类现象与金属板材拉胀实验中所观测到的结果相符合。

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对非线性系统提出了高精度的精细积分任意项外插多步法的计算公式。本方法只需增加插值项数即可提高计算精度,同时不会增加过大的计算量,发展完善了精细积分法。将本方法应用于混沌方程中,取得了较好的效果。数值计算结果表明,该方法是一种高精度、高效率的方法,在求解混沌系统上比传统方法有很大的优势。

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针对轴形零件实际焊接加工中遇到的困难,利用现场总线、串口通信和GALIL运动控制卡实现了上位计算机对激光器、机器人以及旋转台等系统的同步控制,提出了集成化激光制造系统的多种控制工艺焊接方法。对轴形零件进行了各种激光焊接控制工艺的实验研究,证明了此控制系统可实现多种焊接控制工艺,可以满足轴形零件激光焊接中变速度、变功率、偏角度等各种工艺条件焊接的需求,为轴形零件实际激光焊接中遇到的焊接过程不稳定、首尾衔接处凹坑缺陷等难题的解决提供了新的方法。编程采用VC++面向对象工具加以实现。

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A more powerful tool for binary image processing, i.e., logic-operated mathematical morphology (LOMM), is proposed. With LOMM the image and the structuring element (SE) are treated as binary logical variables, and the MULTIPLY between the image and the SE in correlation is replaced with 16 logical operations. A total of 12 LOMM operations are obtained. The optical implementation of LOMM is described. The application of LOMM and its experimental results are also presented. (C) 1999 Optical Society of America.

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We propose a sinusoidal phase-modulating laser diode interferometer for measuring small angular displacement. The interferometer is based on a Fabry-Perot plate. It has a simple structure and is insensitive to external disturbance. Sinusoidal phase-modulating interferometry is used for improving the measurement accuracy. A charge-coupled device (CCD) image sensor is used for measuring the distance between the reflected beams from two faces of the Fabry-Perot plate. From the distance, the initial angle of incidence is calculated. Compared with Michelson interferometers and autocollimators, this interferometer has the advantage of compact size and simple structure. The numerical calculation and experimental results verify the usefulness of this novel interferometer. (C) 2004 Society of Photo-Optical Instrumentation Engineers.

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实现了一种新型的激光脉冲整形系统,该系统使用了一个由孔径耦合带状线(ACSL)电脉冲整形器驱动的电光调制器。一个电脉冲整形器由两条通过其公共接地板上的耦合孔径发生耦合作用的带状传输线所组成的四端口装置。更换具有不同耦合孔径的公共接地板,该电脉冲整形发生器可以具有150ps时间结构的任意整形电脉冲。将任意整形的电脉冲输入到电光调制器上,就可以得到任意整形的激光脉冲。利用该系统,激光脉冲整形系统能够产生具有150ps前后沿,1~3ns脉冲宽度可调、高对比度、光滑过渡以及任意整形的激光脉冲。

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The LB films and spin-coated films of tetra-neopentoxy phthalocyanine zinc (TNPPcZn) were prepared and annealed at different temperatures. Their refractive index (n) and extinction coefficient (k) were measured by p-polarized reflectance. The similar value of n and k, as well as similar changing tendency of it and k at varied annealing temperatures, was found between LB films and spin-coated films. In addition, the absorption curves of TNPPcZn LB films and spin-coated films in visible range at different annealing temperature were investigated. The results indicate that the changing tendency of the extinction coefficient of two kinds of TNPPcZn films obtained from two methods mentioned above were coincident. When the annealing temperature increased to 150 degrees C, the monomers of TNPPcZn films transformed to aggregates, n(f) and k(f) of the films increased. Further, n(f) and k(f) decreased as aggregates changed back to monomers again at the annealing temperature of 300 degrees C. The experimental results coincide well with the theoretical analysis. (C) 2004 Elsevier B.V. All rights reserved.

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国家自然科学基金和云南省自然科学基金资助

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本研究以体外无血清培养的人早期绒毛细胞滋养层细胞和绒毛组织培养为模型,测定了天花粉蛋白对滋养层细胞hCG、孕酮分泌的影响,发现体外无血清培养的细胞滋养层细胞分泌的hCG在天花粉蛋白浓度为0.1μg/ml即下降50%,而后下降缓慢,8μg/ml以上方降为零,而绒毛组织培养在天花粉蛋白浓度为0.1μg/ml时hCG下降近90%,而后下降缓慢,至8μg/ml以上降到零,说明体外培养的细胞滋养层细胞中有两个群体,其中一个对天花粉蛋白敏感,另一个不敏感,尽管在形态上很难区别。孕酮的反应则不同,在细胞滋养层细胞和绒毛组织培养中,随天花粉蛋白浓度升高,孕酮分泌均缓慢下降,未出现两阶段下降过程。

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当前生物入侵已在全球范围内广受关注,鱼类入侵不仅会造成生物多样性不可弥补的消失,而 且其对入侵地生态环境和生态系统的破坏性影响更是深远而不可估量的。为减少鱼类入侵的负面影响,一是 要尽快开展预测预警研究,二是采用管理手段控制入侵的发生及发生后及时采取相应控制措施。综述了鱼类 入侵可能引起的各种效应,初步提出了鱼类入侵的管理策略。

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研究了四种常见优势底栖螺类的饥饿代谢(R,mgO2/ind.d)与温度(T,℃)、体重(Wd,mg dry-wt或Ww,mg wet-wt)的关系,并计算出三者间的复合关系,分别是:铜锈环棱螺,R=0.044Wd0.537e0.061T;长角涵螺,R=0.0004Ww0.9405·e0.0735T;纹沼螺,R=0.004Wd1.072e0.091T;短沟蜷,R=0.023Wd0.777e0.042T。

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Changing the ratio of light-harvesting pigments was regarded as an efficient way to improve the photosynthesis rate in microalgae, but the underlying mechanism is still unclear. In the present study, a mutant of Anabeana simensis (called SP) was selected from retrieved satellite cultures. Several parameters related with photosynthesis, such as the growth, photosynthesis rate, the content of photosynthetic pigment, low temperature fluorescence spectrum (77K) and electron transport rate, were compared with those of the wild type. It was found that the change in the ratio of light-harvesting pigments in the mutant led to more efficient light energy transfer and usage in mutant than in the wild type. This may be the reason why the mutant had higher photosynthesis and growth rates.