Study of a Classical Strobe Composition

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.     

Experimental study of the vortex end in centrifugal separators: The nature of the vortex end

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.     

用74LS148芯片实现32线-5线优先编码器

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。     

GPS多径抑制方法的研究与实现

实际的全球定位系统(GPS)测量中,因为多径效应的影响而使定位精度降低.而环路滤波方法中的Strobe相关器可以有效抑制长多径,但对短多径常常无效.为克服此缺点,在传统Strobe相关器的基础上,细化对于同相多径的情况下建模,对于传统Strobe相关器的表达式进行修正,得到改进型Strobe相关器.接着结合SPIREN...     

Tailored spreading symbols in “Strobe Correlators” using “W2-pulses”

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.     

基于Web的数据安全交互模式研究

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。     

一种高效低纹波调光LED驱动频闪的研究

随着LED照明行业及LED驱动电源技术的发展,具有调光功能的LED驱动电源在LED照明中的应用越来越多,对其调光性能的要求也越来越高.通过对一种高效低纹波调光LED驱动频闪实现方式进行研究,使其既满足LED低纹波电流的要求,又能使LED灯在调光过程中无闪烁、亮度变化均匀柔和,并且可适应不同的调光曲线要求.     

北京理工大学奥运场馆照明设计方案简介

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。     

基于自相关副峰消除的多径抑制技术改进

为消除Sine-BOC(1,1)信号自相关函数的旁瓣所引起的跟踪模糊问题,Oliver Julien提出了自相关副峰消除技术。在此研究的基础上,将其与传统的窄相关和Strobe多径抑制技术相结合,并针对Sine-BOC(1,1)和CBOC(6,1,1/11)信号进行多径抑制性能分析。通过分析EML鉴别曲线过零点偏移情况和多径抑制能力可知,ASPeCT技术不仅消除跟踪模糊,而且能够有效地提升窄相关和Strobe技术的多径抑制能力。     

北京奥运会网球中心照明设计要素

以奥运公园网球中心体育建筑群为例,对体育场馆照明设计的几大要素进行了总结:①为每一部摄像机提供足够的照度;②控制背景照度;③由于高速摄影技术具有特殊的频闪问题,从接线、相序的分配、灯光瞄准方案等方面介绍了控制频闪的具体措施;④确定灯杆高度和布置,保持照明品质的一致性.