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81.
82.
A new pulse stabilisation scheme for a harmonically frequency modulated (FM) modelocked erbium fibre ring laser using a distributed feedback laser diode (DFBLD) is presented. More than 65 dB supermode noise suppression in the RF spectrum was obtained with the proposed method. Effective reduction of supermode noise can be accomplished as the DFBLD in the fibre laser acts not only as a fast-gain saturated medium but also as an optical bandpass filter for suppressing supermode noise in a harmonically modelocked laser system. 相似文献
83.
TMS320C67系列EMIF与异步FIFO存储器的接口设计 总被引:4,自引:0,他引:4
介绍了TI公司TMS320C67系列DSP的EMIF(外部存储器接口)与异步FIFO(先进先出)存储器的硬件接口设计,着重描述了用EDMA(扩展的直接存储器访问)方式读取FIFO存储器数据的软件设计流程,最后说明了在选择FIFO存储器时应注意的问题.由于EMIF的强大功能,不仅具有很高的数据吞吐率,而且可以与不同类型的同步、异步器件进行无缝连接,使硬件接口电路简单,调试方便.运用EDMA的方式进行数据传输,由EDMA控制器完成DSP存储空间内的数据搬移,这样可以最大限度地节省CPU的资源,提高整个系统的运算速度. 相似文献
84.
A simple mathematical analysis on the effect of sand in Cr(VI) reduction using zero valent iron 总被引:1,自引:0,他引:1
A simple mathematical model was proposed to analyze the enhancement of Cr(VI) reduction when sand materials are added to the
zero valent iron (ZVI). Natural decay of Cr(VI) in a control experiment was analyzed by using a zero-order decay reaction.
Adsorption kinetics of Cr(VI) to sand was modeled as a first-order reversible process, and the reduction rate by ZVI was treated
as a first-order reaction. Natural decay of Cr(VI) was also included in other experiments, i.e., the adsorption to sand, the
reduction by ZVI, and both adsorption and reduction when sand and ZVI are present together. The model parameters were estimated
by fitting the solution of each model to the corresponding experimental data. To observe the effect of sand addition to ZVI,
both adsorption and reduction rate models were considered simultaneously including the natural decay. The solution of the
combined model was fitted to the experimental data to determine the first-order adsorption and reduction rate constants when
sand as well as ZVI is present. The first-order reduction rate constant in the presence of sand was about 35 times higher
than that with ZVI only. 相似文献
85.
宋世光 《哈尔滨工业大学学报》1986,(2)
本文在增量调制的原理基础上,对“△”脉宽调制的原理及实质进行了实验分析与研究。从理论上论证了“△”调制方案的合理性。通过实验对“△”调制所提供的满足变频调速要求的控制特性及设计思想的可行性进行了验证。着重对参数选择进行了实验分析,指出了参数选择的观点及其依据。按本文的观点选择参数,在工程应用中是切实可行的。 相似文献
86.
Effects of surfactant/silica and silica/cerium ratios on the characteristics of mesoporous Ce-MCM-41
Se Ho Park Bo Yune Song Tai Gyu Lee 《Journal of Industrial and Engineering Chemistry》2008,14(2):261-264
Using the surfactant CTMABr (cetyltrimethyl ammonium bromide) and cerium(IV) sulfate, mesoporous Ce-MCM-41 molecular sieves were produced under a hydrothermal condition with various surfactant/silica (surfactant/Si) and silica/cerium (Si/Ce) ratios. Changes to the structural traits caused by changing the molar ratios of both surfactant/Si and Si/Ce were investigated. XRD (X-ray diffraction), FT-IR (fourier transform infrared spectroscopy), and SEM (scanning electro microscopy) were used for the characterization of prepared mesoporous samples. Among the tested molar ratios, surfactant/Si ratio of 0.5 and 0.2 showed highest values of d1 0 0 and intensity, respectively, for the Si-MCM-41. XRD analysis also identified a quintessential hexagonal structure of Ce-MCM-41 for the Si/Ce molar ratio higher than 40 (maintaining the surfactant/Si ratio at 0.2). When cerium content was increased to have the Si/Ce molar ratio of 20, the hexagonal structure of Ce-MCM-41 was collapsed due to the structural stress of substituted cerium. FT-IR results confirmed calcination of Ce-MCM-41 and the incorporation of Ce4+ ions of cerium sulfate into the silica surface with proper removal of the surfactant. Rod-like shape with rounded edges of the prepared Ce-MCM-41 samples was identified by SEM. These results suggest surfactant/Si ratio of 0.2 and Si/Ce ratio of 40 for the production of Ce-MCM-41 with the highest level of crystallinity. 相似文献
87.
88.
89.
90.
Song Xiao-chun Huang Song-ling Zhao Wei 《Russian Journal of Nondestructive Testing》2007,43(5):326-331
Magnetization is the key to inspection of a tank floor via the magnetic-flux-leakage (MFL) technique. In order to optimize
the magnetic circuit of the MFL detector and obtain the best detection effects, the influences of the magnet size on the floor
magnetization condition, the gap magnetic flux density, and the magnetic force were studied with the help of the finite element
method (FEM) and the effects of some other parameters, such as the magnet pole spacing and pole-piece thickness, on the signal-to-noise
ratio were analyzed. The simulation results indicate that variation of the magnet width affects the magnetization much more
than variation of the magnet thickness and that the detector can reach a trade-off between the magnetization effects and the
driving force when the magnet is about 30 mm thick and 40 mm wide. On condition that the floor has reached its magnetizing
saturation, an increase in the magnet-pole spacing and the pole-piece thickness can improve the testing sensitivity and the
signal-to-noise ratio.
The text was submitted by the authors in English. 相似文献