共查询到18条相似文献,搜索用时 281 毫秒
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基于光纤中的四波混频(FWM)产生高重复频率超短光脉冲的原理,并为抑制光纤中的受激Brillouin散射(SBS),采用非均匀掺杂高SBS阈值非线性光纤,通过FWM对双拍频信号进行整形压缩,实验上获得了100GHz的高重复率超短光脉冲序列,进而分析了入纤功率对输出光脉冲的影响。 相似文献
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光生微波/毫米波系统中信号控制研究 总被引:1,自引:0,他引:1
提出了一种基于单模光纤FP腔的光生微波/毫米波技术中的输出信号控制方法,得到了输出信号数目与外加应力之间的解析表达式。利用波长为1550.337nm的连续激光,经过100MHz的RF信号调制后入射单模光纤FP腔,得到了频率为1.25GHz微波信号序列的波形图。通过适当调节所施加的外力,可得到从微波到毫米波的光生信号。 相似文献
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《金陵科技学院学报》2021,(3)
在微波电路和传输线理论的基础上,设计了一种多层结构的基于有源频率选择表面的多功能吸波器,其结构分为四层:上层由金属贴片和PIN二极管组成,第二层为介质板,中间层为金属板,最下层为微带馈电结构。该设计通过调节馈电方式来控制PIN二极管通断两种工作状态,从而改变上层金属贴片的组成结构,实现了双频段频率可调。仿真结果表明:所设计的多功能吸波器可调频段范围峰值为8.95~15.32 GHz,且具有极化转换特性,实现了吸波频率的可调,为多功能吸波器的设计提供了新的思路。 相似文献
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从Nd3+:YAG脉冲激光器调Q技术出发,研究了不同腔长条件下电光调Q激光器输出脉冲的宽度、能量和峰值功率特征,得到了不同腔长的调Q激光器输出脉冲特性曲线。研究结果表明,激光器腔长的改变能较好地调节脉冲的输出特性,对脉冲激光器的灵活应用具有一定的指导意义。 相似文献
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一种采用80C51的函数信号发生器硬件设计 总被引:1,自引:0,他引:1
主要介绍了以80C51单片机为核心,通过扩展D/A转换器,得到能输出正弦波、三角波、阶梯波、矩形波等常用波形的函数信号发生器的设计方案。用这种方法设计的函数信号发生器通过外部中断口实现各种波形的选择,并且可通过使用运放调节输出信号的增益来实现对其幅度的调节。能较好满足一般电子系统设计、测试、维护要求。 相似文献
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模拟的电视信号先经脉冲编码调制模拟形式转换成数字形式,中间经信源编码、信道编码,然后送入信道传输。数字电视的接收端是发送端的反过程,经过译码后得到的数字信号又经数/模转器转变为模拟电视信号输出。 相似文献
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基于耦合非线性薛定谔方程,研究了双折射光子晶体光纤中单个光脉冲的非线性传输.当输入脉冲位于反常色散区且偏振角偏离光纤快轴0°和90°时可观察到脉冲俘获现象,脉冲俘获效率在偏振角为45°时最小,当脉冲的入射角度互余时,小角度的脉冲俘获效率更高.此外,增加输入脉冲功率俘获脉冲能够获得更大的频谱偏移. 相似文献
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Jones DJ Diddams SA Ranka JK Stentz A Windeler RS Hall JL Cundiff ST 《Science (New York, N.Y.)》2000,288(5466):635-640
We stabilized the carrier-envelope phase of the pulses emitted by a femtosecond mode-locked laser by using the powerful tools of frequency-domain laser stabilization. We confirmed control of the pulse-to-pulse carrier-envelope phase using temporal cross correlation. This phase stabilization locks the absolute frequencies emitted by the laser, which we used to perform absolute optical frequency measurements that were directly referenced to a stable microwave clock. 相似文献
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Stereochemical course of catalysis by the Tetrahymena ribozyme 总被引:11,自引:0,他引:11
The group I intron from Tetrahymena catalyzes phosphodiester transfer reactions on various RNA substrates. A modified RNA substrate with a phosphorothioate group in one stereoisomeric form at the site of reaction was synthesized in order to determine the stereochemical course of an RNA-catalyzed reaction. The reaction product was digested with a stereospecific nuclease to determine the configuration of the product phosphorothioate. The reaction occurs with inversion of configuration at phosphorus, implying an in-line pathway for the reaction. 相似文献
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随着内检测的不断推进,大部分管道已经开展了两轮及以上次数的内检测作业,获得了大量内检测数据。由于内检测受外部环境及检测误差的影响,多轮内检测数据在里程、缺陷识别与量化方面存在一定差异,难以实现多轮内检测数据的快速对齐,且人工对齐工作量巨大。为研究内检测数据的快速对齐方法,结合大量内检测数据,构建了内检测数据对齐算法模型,基于该模型实现了内检测数据的快速对齐,并通过不同单位、不同格式的内检测数据进行应用测试。测试结果表明:该方法可以实现管道阀门、三通等特征100%对齐,管节对齐比例达99%以上,弯头对齐比例达90%以上。基于该方法,可快速对内检测数据进行深度挖掘分析,预测管道本体缺陷发展趋势,为管道腐蚀控制及管道本体管理提供数据支撑,实现管道本体风险的预控,提高管道完整性管理水平。 相似文献
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The ability of scanning tunneling microscopy to probe the pathways of thermally activated high-barrier surface processes is frequently limited by competing low-barrier processes that can confuse measurement of the true initial and final configuration. We introduce an approach to circumvent this difficulty by driving the surface process with nanosecond laser heating. The method is applied to determine the pathway of recombinative desorption in the H/Si(001) system. The observed configuration of dangling bonds after laser heating reveals that the desorbed hydrogen molecules are not formed on single dimers, but rather from neighboring silicon dimers via an interdimer reaction pathway. 相似文献
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Byer RL 《Science (New York, N.Y.)》1988,239(4841):742-747
Diode laser-pumped solid-state lasers are efficient, compact, all solid-state sources of coherent optical radiation. Major advances in solid-state laser technology have historically been preceded by advances in pumping technology. The helical flash lamps used to pump early ruby lasers were superseded by the linear flash lamp and arc lamp now used to pump neodymium-doped yttrium-aluminum-garnet lasers. The latest advance in pumping technology is the diode laser. Diode laser-pumped neodymium lasers have operated at greater than 10 percent electrical to optical efficiency in a single spatial mode and with linewidths of less than 10 kilohertz. The high spectral power brightness of these lasers has allowed frequency extension by harmonic generation in nonlinear crystals, which has led to green and blue sources of coherent radiation. Diode laser pumping has also been used with ions other than neodymium to produce wavelengths from 946 to 2010 nanometers. In addition, Q-switched operation with kilowatt peak powers and mode-locked operation with 10-picosecond pulse widths have been demonstrated. Progress in diode lasers and diode laser arrays promises all solid-state lasers in which the flash lamp is replaced by diode lasers for average power levels in excess of tens of watts and at a price that is competitive with flash lamp-pumped laser systems. Power levels exceeding 1 kilowatt appear possible within the next 5 years. Potential applications of diode laser-pumped solid-state lasers include coherent radar, global sensing from satellites, medical uses, micromachining, and miniature visible sources for digital optical storage. 相似文献
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Stereochemistry of RNA cleavage by the Tetrahymena ribozyme and evidence that the chemical step is not rate-limiting 总被引:18,自引:0,他引:18
The intervening sequence of the ribosomal RNA precursor of Tetrahymena is a catalytic RNA molecule, or ribozyme. Acting as a sequence-specific endoribonuclease, it cleaves single-stranded RNA substrates with concomitant addition of guanosine. The chemistry of the reaction has now been studied by introduction of a single phosphorothioate in the substrate RNA at the cleavage site. Kinetic studies show no significant effect of this substitution on kcat (rate constant) or Km (Michaelis constant), providing evidence that some step other than the chemical step is rate-limiting. Product analysis reveals that the reaction proceeds with inversion of configuration at phosphorus, consistent with an in-line, SN2 (P) mechanism. Thus, the ribozyme reaction is in the same mechanistic category as the individual displacement reactions catalyzed by protein nucleotidyltransferases, phosphotransferases, and nucleases. 相似文献