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991.
通过对宽展模型结构型式的选择和孔型形状系数的数学分析,建立了根据变形系数寻找几何形状的设计思想。用这种思想探讨了单个孔型和连轧孔型的设计方法。研究表明,常规型钢孔型设计总是在不断的设计—校核中完成的,而新方法避免了这种多次反复的过程。而且新方法更精确、简洁,更有利于设计过程的程序化 相似文献
992.
We describe here an aberration that is frequently encountered with water‐immersion but not oil‐immersion objectives. The aberration is shown to be induced by tilt of the coverslip out of the plane normal to the optical axis. Model calculations taking into account the path‐length distortions introduced by a tilted coverslip satisfactorily reproduce the observed effect on the images of small subresolution fluorescent beads. 相似文献
993.
Determining factor for the blowoff limit of a flame spreading in an opposed turbulent flow, in a narrow solid-fuel duct 总被引:1,自引:0,他引:1
This study clarified the blowoff mechanism for a flame spreading in an opposed turbulent flow in narrow solid fuel ducts. To clarify this mechanism, two experiments were conducted. The first experiment was to investigate the influence of ambient pressure and fuel duct size on the blowoff limit. The results indicated that the flow velocity at the point when blowoff occurred, Vg,t, increased with ambient pressure. This tendency could not be confirmed by a well-known expression for the Damköhler number, which is defined as the ratio of the characteristic flow time to the characteristic chemical time. Subsequently, to clarify the determining factor for the blowoff, the second experiment, which observed the flow field near the flame leading edge, was conducted. The results show that the flow separation in front of the flame leading edge, which provided sufficient residence time of oxidizer and gaseous fuel, is necessary for the flame to spread in an opposed oxidizer flow. From the results, it is found that the oxidizer friction velocity, u∗, which is an indicator of the turbulent momentum transfer, is the determining factor for the flame blowoff limit. When the friction velocity is larger than a critical value, flame blowoff occurs in the fuel duct, due to the absence of flow separation. 相似文献
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997.
本文针对扩频无线数据通信系统的捕获问题,提出了一种采用PN匹配滤波器实现的方法,大大提高了通信效率。文中对高斯信道和瑞利信道条件下的PN匹配滤波器的捕获性能进行了分析。 相似文献
998.
映射序列扩频通信方式及其特性 总被引:6,自引:1,他引:5
同时传送多路数据一直是通信的基本课题,本文提出用3个被调制的扩频序列处理成映射序列进行扩频通信,能同时传送3路信息数据,理论分析表明,在不改变常规扩频接收机的情况下,能可靠解出同时传送来的任何一路信息数据,它比8PSK、8QAM调制方式具有更好的通信特性。 相似文献
999.
热带粗轧机组宽度变化规律的实验研究 总被引:2,自引:0,他引:2
采用铅作为模拟材料,对热带粗轧机组平辊立轧及随后水平轧制时轧件宽度变化规律进行了实验研究。分析和比较了宽展行为及头、尾部失宽行为与变形工艺参数之间的关系,并得到了相应的数学模型。 相似文献
1000.
Ali Masoomzadeh-Fard Subbarayan Pasupathy 《International Journal of Wireless Information Networks》1996,3(2):105-115
Indoor radio communication in the 20–60 GHz band using TDMA with differentially encoded QPSK is consideed. A burst-type transmission, based on a basic time slot consisting of a preamble for synchronization and equalizer training and of an information data section, is adopted. We employ fractionally spaced decision feedback equalization and give the relevant analytical and simulated performance results in terms of Doppler frequency. An upper limit is determined for the channel variations which can be tracked by the equalizer. Performance results are obtained for equalization with and without carrier phase recovery. Calculated and simulated probability of error show that error propagation degrades the performance by about 6 dB at a bit error rate of 10–3 for a channel without any diversity. However, the effect of past decision errors is negligible for dual diversity. Numerical stability, required accuracy, and hardware complexity are also discussed. 相似文献