On the design of signal sets with constrained magnitude spectrum and phase structure

In this paper, a new method is introduced for designing signals that have low cross‐correlation among them with constant passband magnitude spectrum and quadratic phase. It is shown that in order to get low values of the cross‐correlation magnitude between any two signals in the set, the coefficients of the phase functions should be equally spaced along one axis of an ellipse determined by the bandwidth and time duration of signals. Furthermore, as an estimate of the maximum cross‐correlation magnitude, a new tighter upper bound is also given in the paper. Copyright © 2002 John Wiley & Sons, Ltd.     

用P507-磺化煤油溶液从硝酸溶液中萃取分离镅(锔)与稀土元素

测定了镅(锔)和轻稀土元素(La、Ce、Pr、Nd、Sm)在P507-磺化煤油和硝酸溶液中的分配比,确定了它们被萃取能力的顺序为:La相似文献   

Numerical modelling of the effects of joint spacing on rock fragmentation by TBM cutters

The influence of joint spacing on tunnel boring machine (TBM) penetration performance has been extensively observed at TBM site. However, the mechanism of rock mass fragmentation as function of the joint spacing has been scarcely studied. In this study, the rock indentation by a single TBM cutter is simulated by using the discrete element method (DEM), and the rock fragmentation process is highlighted. A series of two-dimensional numerical modelling with different joint spacing in a rock mass have been performed to explore the effect of joint spacing on rock fragmentation by a TBM cutter. Results show that the joint spacing can significantly influence the crack initiation and propagation, as well as the fragmentation pattern, and can hence affect the penetration rate of the TBM. Two crack initiation and propagation modes are found to fragment the rock mass due to the variation of joint spacing. The simulation results are analyzed and compared with in situ measurements.     

OPTIMAL MODEL OF COMBINED PHASE CENTER FOR HORN FEEDS AND ITS COMPUTATIONAL METHOD

A definition of combined phase center for horn feeds is given.Formulas of E-planeand H-plane combined phase center for conical horns and the corresponding Optimal model arepresented,and a fast optimization method for solving this model is described.By using thismethod,the phase center of corrugated horn is discussed and calculated,and the variation of thephase center with distance and operating frequency is given.     

以IP网为信令通道的光网络管理方案研究

提出了一种利用现有的IP网络作为信令通道的光网络管理方案。该方案应用于清华大学校级重点学科建设的高速宽带信息网项目中,成功地实现了配置管理、性能管理和故障管理功能。最后讨论了这种方法的优缺点。     

MEMS器件的腐蚀与释放

以硅微机械FP腔器件为代表,该器件采用了标准的硅表面加工工艺,分析了此类具有悬空结构的MEMS器件在进行牺牲层的腐蚀和最终的结构释放过程中的各种问题.根据所遇到问题的不同情况对器件的设计和工艺流程进行了改进,并通过实验验证了其可行性.     

宏单元阵列布局的两步模拟退火算法

本文提出了一种适用于ＶＬＳＩ布局的算法－两步模拟退火算法，针对宏单元版图模式的特点，算法将通常的模拟退火过程为分两步完成，从而使得算法性能有所改善。     

4Cr_(14)Ni_(14)W_2Mo耐热合金钢等σ_s(T)—T变化规律及其热力学判据

本文研究了4Cr_(14)Ni_(14)W_2Mo耐热合金钢等材料屈服应力随温度的变化规律,给出了σ_s(T)—T实验曲线,并对实验结果作出唯象解释。最后还探讨了判断疲劳断裂类型的热力学判据σ_r(t)/σ_s(t)。