79 resultados para Witt, Johan de, 1625-1672.


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介绍了实验装置与测压系统,实测了饱和砂柱自由落体撞击地面后前期快过程和后期慢过程的水压力的变化。

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对公开发表的用于超声速燃烧流场分析的几种一维模型进行了研究,指出了其中存在的问题,研究结果表明:基于实验静压数据的一维模型,若不借助必要的流场测量数据或分析结果,或借助于经验性的处理方法,单靠一维假设,无法获得较为完整的一维流场分析结果。改进后的一维模型降低了数据处理过程中的不确定性,提高了对一般情况的适应能力。用编制的计算程序SSC-2对两组典型的超燃燃烧室壁面静压实验数据进行了演算,取得了燃烧室出口总压恢复系数的计算值与测量值基本一致的好结果。

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基于本文作者在文献[1]中所导出的冷压P_x,利用德拜固体模型并考虑电子的热压,得到了金属的高温高压状态方程。在与Hugoniot方程联立后,就能算出Hugoniot曲线。本文计算了五种简单金属的Hugoniot曲线。结果表明,在现有实验数据所能达到的范围内,理论计算与实验符合都比较好。

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We experimentally study the ac Stark splitting in D2 line of cold Rb-87 atoms. The frequency span between the Autler-Townes doublets is obviously larger than that derived from theoretical calculation. Two physical effects, which increase the effective Rabi frequency, contribute to the splitting broadening. First, atoms tend to distribute in strong lield places of a inhomogeneous red-detuned light field. Second, atoms reabsorb scattered light when they are huge in number and high in density.

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Polymer deposition is a serious problem associated with the etching of fused silica by use of inductively coupled plasma (ICP) technology, and it usually prevents further etching. We report an optimized etching condition under which no polymer deposition will occur for etching fused silica with ICP technology. Under the optimized etching condition, surfaces of the fabricated fused silica gratings are smooth and clean. Etch rate of fused silica is relatively high, and it demonstrates a linear relation between etched depth and working time. Results of the diffraction of gratings fabricated under the optimized etching condition match theoretical results well. (c) 2005 Optical Society of America.

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提出了一种新的光刻机像质参数热漂移原位检测技术(TDFM)。详细分析了该技术利用镜像测试标记检测投影物镜最佳焦面热漂移与放大倍率热漂移的基本原理。实验结果表明TDFM技术可同时实现最佳焦面热漂移(FFT)与放大倍率热漂移(MFT)的精确测量。与现有的放大倍率热漂移检测技术相比,该技术有效地解决了放大倍率热漂移技术中放大倍率热漂移受最佳焦面热漂移影响的问题,简化了光刻机像质参数前馈校正的测试过程,测试成本与耗时均减少50%。

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大模场面积(LMA)光纤激光器的光束质量通常比单模光纤激光器的光束质量差。采用光纤拉锥的方法进行模式选择,从而提高大模场直径光纤激光器的光束质量。拉锥区距光纤激光器的输出端约5 mm,纤芯最小为9 μm,约为未拉锥部分纤芯直径26 μm的1/3。实验研究表明,在拉锥后,光纤激光器的光束质量因子M2由3.50减小为1.81,相应的斜率效率由63.6%减小为51.1%。虽然拉锥后最大输出功率减少了约19.8%,但其亮度增大为拉锥前的3倍。

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由中国科学院上海光学精密机械研究所激光光源研究发展中心承担的国家863—804项目创新研究课题“特大口径高功率脉冲氙灯的研制”取得重大进展,

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New broadband near infrared luminescence covering the whole work windows (1260-1625 nm) of the current wavelength division multiplexing (WDM) system was found from bismuth-activated M2O-Al2O3-SiO2 (M = Li, Na) and Li2O-Ta2O5-SiO2 glasses at room temperature in the case of 808 nm-laser excitation. But the near infrared luminescence mechanism of the bismuth-activated glasses is not well understood up to now. The figure-of-merits of bandwidth and gain of the glasses are better than those of Er3+-doped silicate glasses and Ti3+ doped sapphire, implying they are the promising gain-medium candidates for the broadband amplifiers and the widely tunable laser sources. (c) 2007 Elsevier B.V. All rights reserved.

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Near-infrared broadband emission from bismuth-tantalum-codoped germanium oxide glasses was observed at room temperature when the glasses were pumped by an 808 nm laser diode. The emission band covered the 0, E, S, C, and L bands (1260-1625 nm), with a maximum peak at similar to 1310 nm, a FWHM broader than 400 nm, and a lifetime longer than 200 lis. The observed broadband luminescence was attributed to bismuth clusters in the glasses. Bismuth-tantalum-codoped germanium oxide glass might be promising as amplification media for broadly tunable lasers and wideband amplifiers in optical communications. (c) 2005 Optical Society of America.

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从计算机技术的角度出发,对植物形态学信息处理和应用,构成本文的思想,文中简略同顾了植物形态学术语的标准化的历史发展过程,对当前世界范围内在此领域的工作也作了概要般的总结,论述了计算机技术用十植物学应用和研究的重要性并提出了我国在此领域内开展工作的紧迫性和必要性。计算机的资源限制及植物信息特有的复杂性是这一领域发展的困难。因此,如何贮存植物信息?如何操作加工应用?才能充分利用计算机资源和植物信息资源成为本领域的核心问题。 本文基于上面的考虑,对植物形态学信息从基本的信息单位植物形态学术语出发,探求其分类结构,并从计算机技术的编码理论方面进行探讨.力图求得一个标准化的植物形态学描述分类群的术语编码集,提供一种实现描述的方法,并试验性地给出一种描述规范和格式,简单讨论一下实现语言处理,机器鉴定、数量分类的可能性,最后简单分析和对比了本工作和国际上的类似工作,并对本领域进行了简单的展望。

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本发明属于生物医学领域。大蹼铃蟾多肽是从中国两栖类动物大蹼铃蟾皮肤分泌物中分离得到的一种单链多肽,分子量2698.4,等电点10.0,多肽全序列一级结构为:NH2—TITTKKLSGLKTALKGAAKELASTYT—COOH。制备方是将活体大蹼铃蟾用水清洗干净,置于带盖的玻璃容器中,滴加无水乙醚,密闭容器3—5分钟,可见大量的泡沫状物质从大蹼铃蟾皮肤分泌出来,收集分泌物,离心去除沉淀、冷冻干燥后,经离子交换、凝胶过滤、高压液相反相柱层析分离纯化后得到。具有显著的抑制细菌和真菌生长、肿瘤细胞生长、和抗艾滋病病毒活性的作用。适用于制备抗微生物感染、抗肿瘤、抗艾滋病药物。