排序方式: 共有49条查询结果,搜索用时 906 毫秒
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There are many advantages in being able to perform positron annihilation lifetime spectroscopy (PALS) using a variable energy positron beam, the most obvious being the easy identification of different defect types at different depths. The difficulty in conducting variable energy (VE) PALS studies lies in the fact that a “start” signal is required to signal the entry of the positron into the target. Two methods have been used to overcome this problem, namely the bunching technique, which employs radio frequency (RF) cavities and choppers, and secondly the use of secondary electrons emitted from the target. The latter technique is in terms of experimental complexity much simpler, but has in the past suffered from poor time resolution (typically ∼500 ps). In this work, we present a series of computer simulations of a design based on the secondary electron emission from thin C-foils in transmission mode which shows that significant improvements in time resolution can be made with resolutions ∼200 ps being in principle possible. 相似文献
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王世元 《分析测试技术与仪器》1996,2(1):28-32
为解决在线氧含量分析测试仪表常被聚合物堵塞的问题,提出了自动反吹的时序分配和实施控制方案,从而为安全生产提供了保障。 相似文献
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Gilberto Muñoz Moreno Noé Alcalá Ochoa 《Optics and Lasers in Engineering》2011,49(6):663-667
An analysis of phase modifications introduced by laser jitter in frequency-domain optical coherence tomography (OCT) is described. It is shown that a 1D spurious phase function is introduced as a consequence of this phenomenon. This phase function is added to any other introduced by the object under analysis causing a superposition of both. The result may impose some limitations for unambiguous determination of phase changes of objects. Experimental and theoretical results are presented. 相似文献
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We investigate a dominant retailer’s optimal joint strategy of pricing and timing of effort investment and analyze how it influences the decision of the manufacturer, the total supply chain profit, and the consumers’ payoff. We consider two pricing schemes of the retailer, namely, dollar markup and percentage markup, and two effort-investment sequences, namely, ex-ante and ex-post. A combination of four cases is analyzed. Our results show that: (1) under the same effort-decision sequence, a percentage-markup pricing scheme leads to higher expected profit for the retailer and the whole supply chain, but a lower expected profit for the manufacturer and a higher retail price for the consumers; (2) under the same markup-pricing strategy, the dominant retailer always prefers to postpone her effort decision until the manufacturer makes a commitment to wholesale price, since it can result in a Pareto-improvement for all the supply chain members. That is, the retailer’s and manufacturer’s expected profits are higher and the consumers pay a lower retail price; and (3) among the four joint strategies, the dominant retailer always prefers the joint strategy of percentage-markup plus ex-post effort decision. However, the dominated manufacturer always prefers the joint strategy of dollar-markup plus ex-post effort decision, which is also beneficial to the end consumers. 相似文献
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We have investigated the return-to-zero (RZ) pulse duty cycle for single-channel Standard Single mode fiber (SSMF), Non Zero Dispersion shifted fibers (normal NZDSF and anomalous NZDSF fiber) for 10 Gbps optical fiber communication system. We give a comprehensive look on the behavior of variable duty cycle optical RZ pulse indicating that lowest bit error rate for duty cycle 0.8 among the duty cycle values 0.2, 0.4, 0.6 and 0.8 investigated for the case of SSMF. The single repeaterless mode fiber length is increased from existing 55 km at duty cycle 0.2 to fiber length 85 km by keeping duty cycle at 0.8. The result is also emphasized through the 10 dB Q value improvement and corresponding improvement in average eye opening diagram. The normal NZDSF show similar improvement but at greater fiber length, it offers BER 10−9 at length 110 km with duty cycle 0.2. NZDSF operating length can further be increased to length 160 km by keeping duty cycle 0.8. The corresponding 8 dB Q value improvement and Average eye opening improvement also supports the result through its graphical variation. Thirdly Anomalous NZDSF for same optical communication system showed that 0.2 duty cycle value give operational length of 130 km which could be extended to 160 km if 0.8 duty cycle is kept. The corresponding 8 dB Q value improvement, average eye-opening improvement endorsed the fact in the graphs. 相似文献
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基于 HL-2M 装置对时序精度的要求,参考 ITER 的设计方案,设计了基于精确时间协议(PTP)的 HL-2M 分布式时间通讯网络,使 HL-2M 装置的时钟同步和事件触发的精度从微秒级提高到亚微秒级,最终优于 100ns。 相似文献
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Jacob Lasri Preetpaul Devgan Vladimir S. Grigoryan Prem Kumar 《Optics Communications》2004,240(4-6):293-298
We demonstrate a novel, polarization-insensitive scheme for multiwavelength nonreturn-to-zero to return-to-zero format conversion at 10 Gb/s rate with significant timing-jitter suppression and signal-to-noise ratio improvement. The scheme utilizes a self-starting electroabsorption-modulator based optoelectronic oscillator that simultaneously generates a 10 GHz-rate microwave signal and a train of 15 ps-wide optical pulses with 40 fs timing jitter (100–10 MHz range). Under direct optical injection locking of the oscillator with an incoming data stream, we demonstrate the extraction of a high-quality clock that enables in-line format conversion of multiple, synchronized nonreturn-to-zero channels. 相似文献