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21.
We review our recent progress toward attosecond‐precision ultrafast photonics based on ultra‐low timing jitter optical pulse trains from mode‐locked lasers. In femtosecond mode‐locked lasers, the concentration of a large number of photons in an extremely short pulse duration enables the scaling of timing jitter into the attosecond regime. To characterize such jitter levels, we developed new attosecond‐resolution measurement techniques and show that standard fiber lasers can achieve sub‐fs high‐frequency jitter. By leveraging the ultra‐low jitter of free‐running mode‐locked lasers, we pursued high‐precision optical‐optical and optical‐microwave synchronization techniques. Optical signals spanning 1.5 octaves were synthesized by attosecond‐precision timing and phase synchronization of two independent mode‐locked lasers. High‐stability microwave signals were also synthesized from mode‐locked lasers with drift‐free sub‐10‐fs precision. We further demonstrated the attosecond‐precision distribution of optical pulse trains to remote locations via timing‐stabilized fiber links. Finally, the application of optical pulse trains for high‐resolution sampling and analog‐to‐digital conversion is discussed. 相似文献
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本文使用风险中性评价方法分三部分计算了复合期权的价值,针对需要计算联合分布的第二部分,通过选取边缘分布为GARCH模型的二元正态Copula模型进行推理验证,结果求得的联合分布与使用风险中性评价方法的计算结果一致.进一步计算得到了时间相依的复合期权的价值,并且给出了使用Bayes时序诊断法和Z检验来诊断期权定价时其出现价格大的波动时的局部拐点的方法. 相似文献
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Abstract We investigate the chirp selection of externally modulated return-to-zero soliton pulse at 10 Gb/s for fiber optical communication system for the reduction in timing jitter. The chirp range (?5 to +5), as well as the effect of the post compensation, have been examined up to ten regenerated fiber spans in the link. Here, it is shown that the chirp value of the external modulator should be set to either 0 or ?1 to reduce timing jitter. Moreover, for more number of spans, it will be better to adopt other chirp values. 相似文献
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The main problem in security protecting the computer or resources from intruders. The password and username are the most common means to provide security. But this method has many loop holes such as password sharing, shoulder surfing, brute-force attack, dictionary attack, guessing, and many more. Keystroke dynamics is one popular and inexpensive behavioral biometric technology, which identifies the authenticity of a user when the user is working via a keyboard. Keystroke features like dwell time and flight time of every user are evaluated in this paper by preprocessing techniques such as Hausdroff timing, mean, median, and standard deviation. The artificial immune system is used for feature selection, and comparison between preprocessing techniques is shown. 相似文献
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智能型高速CCD相机的时序电路的研制 总被引:3,自引:0,他引:3
首先详细地介绍了几种传统时序电路的实现方法与各自存在的优缺点 ,然后对 isp L SI器件的性能特点以及 TDI- CCD相机的组成结构、工作原理进行了简要地阐述 ,最后对采用 isp L SI器件实现 CCD相机时序电路的全过程进行了全面、细致地分析。本文结合实际课题 ,已由在线可编程大规模逻辑器件实现了高速 TDI- CCD相机的时序电路。此相机系统具有一些重要参数 (行周期、TDI级数、视频信号的增益、偏置参数 ) ,并可以灵活控制。同时该系统又具有高可靠性、高稳定性、低功耗等特点。 相似文献
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The Blade Tip Timing (BTT) measurement system is a technique to measure vibration parameters of a rotating bladed disk. In particular for synchronous vibrations the BTT provides signals versus the rotation speed of the disk starting from the measurement of the time of arrival (TOA) of each blade under the tip timing probes. The signals must be post processed in order to obtain the interesting parameters of each blade vibration. The paper presents a method to extract the main parameters (amplitude and frequency) in resonance condition from the tip timing measurements. The proposed method is a revision of the already existing well known Two-Parameter Plot (2PP) method which requires a minimum of two probes. Improvements to the existing 2PP method are here suggested mainly in the part of engine order identification.The proposed method is then applied to the BTT measured signals coming from a rotating bladed disk excited at different engine orders. At the same time on the disk the vibration of one blade was detected by strain gauges. The strain gauges were calibrated and they provide the reference values of the vibration parameters. The vibration parameters derived by the proposed method are in agreement with those obtained by the strain gauges methodology. 相似文献
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We calculate and discuss the motion of the binary black hole OJ287 based on Post-Newtonian approximation in a harmonic coordinate. With gravitational waveform obtained, theoretical timing residual of PSR B1855+09 induced by gravitational radiation of OJ287 is presented and compared with observed data, further shows that hypothesis referring to OJ287 as a binary BH system might be proper. The energy flux of gravitational radiation from binary is also provided, from which we find that the flux changes sign successively: ?N >0, ?1PN <0, ?2PN >0, in agreement with the relative signs of forces of each PN order, revealed in the previous work. 相似文献