排序方式: 共有17条查询结果,搜索用时 31 毫秒
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Justine M. L. Corbel Joost N. J. vanLingen John Z. Zevenbergen Onno L. J. Gijzeman Andries Meijerink 《Propellants, Explosives, Pyrotechnics》2013,38(5):634-643
Many strobe compositions were discovered in the past but only a few have been studied and none of them were fully understood. This article aimed at introducing the ternary composition of ammonium perchlorate as oxidizer, magnalium as fuel, and barium sulfate as metal salt. Parameters that influence its performances are analyzed. First, the binary compositions ammonium perchlorate/magnesium and ammonium perchlorate/magnalium were studied to observe the differences in behavior by using magnalium instead of magnesium. Next, variations were applied to the ternary composition changing the fuel: oxidizer:metal salt ratio. Finally the effect of potassium dichromate was analyzed. It is often added to the composition because it is known to improve the regularity and sharpness of flashes. The burning behavior was recorded using a high speed camera, together with emission spectra using a Charged‐Coupled Device (CCD) camera coupled with a spectrometer and the temporal evolution of the intensity with a photodiode coupled with an oscilloscope. The results of the experiment give first insights into the physical and chemical mechanisms and give directions to the further study on strobe reactions. 相似文献
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第3代北斗卫星导航系统中B1C频点信号将使用正交复用二进制偏移载波调制方式。为了增强北斗卫星导航接收机码跟踪环路的抗多径性能并且解决码跟踪中的模糊跟踪问题,该文针对正交复用二进制偏移载波调制信号QMBOC(6, 1, 4/33)提出一种双闸波码跟踪环路结构。根据理想的目标鉴相函数和二进制偏移载波调制信号自相关函数的特点分别设计出针对BOC(1, 1)和BOC(6, 1)信号的闸波,并在本地码跟踪环路中使用这两种不同的闸波分别与输入信号相关,最后将所得的两个相关函数进行加权合并以用于鉴相过程。计算机仿真结果表明所提方法不仅能够有效消除QMBOC(6, 1, 4/33)信号的模糊跟踪可能性,且能够大幅增强接收机的抗多径性能,其对应多径误差包络面积相比于现有的方法能够减少约33%。 相似文献
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Experimental study of the vortex end in centrifugal separators: The nature of the vortex end 总被引:1,自引:0,他引:1
W. Peng A.C. Hoffmann H.W.A. Dries M.A. Regelink L.E. Stein 《Chemical engineering science》2005,60(24):6919-6928
The nature of the vortex end (or the “tail end” or “tip”) in reverse-flow centrifugal gas cleaning equipment, cyclones and swirl tubes, has been studied by visualization using a stroboscope and high-time-resolution pressure measurements. The core of the vortex is shown to bend to the wall of the separator, and rotate around the wall, forming the ring-shaped pattern normally observed at the vortex end. The end of the vortex was found to occur higher in the swirl tube (“less stable vortex”) when the solid loading is increased, and when the volumetric flow rate to the tube is decreased. The frequency with which the vortex core rotates varies with the gas flow rate and was found to be about the same as the frequency with which the gas rotates higher in the separator. The time-averaged wall pressure suddenly decreases in the separator body at the point where the vortex end attaches to the wall. 相似文献
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74LS148芯片是8线-3线优先编码器。如果要得到32线-5线优先编码器,可以通过列单块74LS148芯片的简化真值表,列32线-5线优先编码器的简化真值表,找出32线-5线优先编码器的每一个输出与每块74LS148的扩展端YEX的关系,与每块74LS148输出的关系。利用74LSL148的选通输入端S、选通输出端YS、扩展端YEX就可用四块74LS148芯片构成32线-5线优先编码器。 相似文献
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A “Strobe Correlator” is a correlation-based multipath mitigation technique that utilizes tailored reference waveform to shape the discriminator function for tracking Global Navigation Satellite System (e.g. Global Positioning System) signals. Multipath performance of these techniques for Binary Phase Shift Keying (BPSK) signals has been discussed for decades but for some, their noise performance may not be easily evaluated analytically. In this paper, a theoretical framework is provided for noise evaluation of “Strobe Correlators” using complex strobes for both BPSK and sine-phased Binary Offset Carrier (e.g. BOC(1,1)) signals. Mathematical expressions of the tailored spreading symbols as key factors are derived and used for theoretical code tracking variance analysis of various correlation techniques including the “Gating Function” using a complex strobe-pulse liked waveform (i.e. “W2-pulses”). Empirical results for the sine-phased BOC(1,1) signal are given as verification. Analytical results reveal that the techniques using a W2-pulse suffer from higher code tracking variance than others, due to increased sensitivity to noise. The sensitivity to pre-correlation bandwidth is found to relate to the relative placement of the strobe pulses. 相似文献
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基于Web的数据安全交互模式研究 总被引:3,自引:0,他引:3
目前越来越多的应用系统开始向因特网平台转移,网络安全问题已经成为计算机安全领域中的一个研究热点,首先对一般的电子商务应用系统的安全性进行分析;然后提出网闸系统模式,在保证数据通信的基础上,从物理上把企业内部网与因特网相隔离,大大提高了企业原有系统的安全性。 相似文献
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给出了BOB对奥运场馆照明设计要求.简单介绍了北京理工大学体育馆光源及灯具的选择、照明布置、照明配电,以及照明控制系统。 相似文献
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