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991.
Joint multi-user space time block coding and beamforming via convolutional weighting 总被引:1,自引:0,他引:1
A convolutional weighting (CW) scheme applied to a half-wavelength spacing array was proposed for multi-user system to joint STBC (space time block ceding) and beam forming (BF). The transmitting beam is equivalent to the product of two sub-beams. One is used to realize interference suppression, while the other is employed to form a couple of uncorrelated channels from base station (BS) to the desited user (to meet the requirement of STBC) and to maximize SINR (signal-to-interference-plus noise ratio) at the desired receiver. As an optimum combination of STBC and beam forming, the proposed scheme can achieve both full diversity order of STBC and array gain of BF. Meanwhile, it can also effec- tively restrain multi-user interference by nulling. Simulation results show that the proposed scheme can significantly improve the BER (Bit Error Rate) performance and enhance system capacity as compared with the conventional eigen-beamforming (EBF) technique applied to a half-wavelength spacing array. 相似文献
992.
The function-layer model and working model of collaborative remote fault diagnosis system (FDS), which includes three layers: task layer, collaboration layer and diagnosing layer, are proposed. The running mechanism of the system is discussed. A collaborative FDS may consist of several subsystems running at different places and the subsystem consists of several fimction modules. A structure centered on data-bus is adopted in subsystem. All the function modules in subsystem are encapsulated into software intelligent chips (SICs) and SIC can but connect with data-bus. So, it is feasible to reuse these diagnosis fimction modules and the structure of subsystem in different diagnosis applications. With the reconfigurable SICs, several different function modules can reconstruct quickly some different diagnosis subsystems in different combinations, and some subsystems can also reconfigure a specified collaborative FDS. 相似文献
993.
The rotor with bending faults that occurrs on the rotating machinery usually vibrates seriously. This paper investigates to apply the active balancing device on a flexible rotor with bending faults to solve the vibration problem. Two problems are studied by finite element method firstly: Where the balance actuator is fixed on the shaft and how much the balancing capacity of the active balancing device is needed. The experiment is then carried out on the test rig, which consists of a flexible rotor with bending faults. The test results indicate that the bending rotor peak vibration response can be decreased from 550~m to 40~tm below by using the active balancing device. The peak vibration response decreases approximately by 93 %. The synchronous vibration due to the rotor bending faults can be controlled effectively by using ac- tive balancing device. The active balancing device is especially adapted to solve the problem caused by thermal distortion with time-variation and randomness, which is varied with working conditions, thus it has good practical value in practice. 相似文献
994.
Radio frequency interference (RFI) is a major problem in high-frequency (HF) radars. Conventional filtering-involved RFI suppression methods may introduce distortions to the target signals of interest and often demand extra hardware costs. In this paper, a novel method for RFI suppression by using linearly or randomly phase-modulated (PM) chirps is proposed, which enables independent analyses of the target signal and the RFI. Furthermore, the directions of arrival (DOA) of the interference are used as constraints to ensure a better DOA estimation of the target. The effectiveness of the method is demonstrated by numerical simulation results. The method can greatly improve the anti-interference capabilities of HF radars and is extremely applicable in the portable and low-cost radar systems. 相似文献
995.
This paper proposes a checking method based on mutual instances and discusses three key problems in the method: how to deal with mistakes in the mutual instances and how to deal with too many or too few mutual instances. It provides the checking based on the weighted mutual instances considering fault tolerance, gives a way to partition the large-scale mutual instances, and proposes a process greatly reducing the manual annotation work to get more mutual instances. Intension annotation that improves the checking method is also discussed. The method is practical and effective to check subsumption relations between concept queries in different ontologies based on mutual instances. 相似文献
996.
PAN Ding SHEN Jun-yi ZHOU Mu-xin 《武汉大学学报:自然科学英文版》2006,11(1):165-169
0 IntroductionTeosda,yth meyan hya voerg daantiazbaatisoenss t hhaatv ec hmaonrgee t ahnadn glarrogwe cdoatnatibnaus--ously. One of the i mportant research issues is incrementalmining. Otherwise, various researchers have made sugges-tions that domain knowledge should be incorporated intoknowledge discovery ( KDD) process[1]. We focus on somesteps of the KDDprocess-those steps tying up with data min-ing,called a data mining (DM) process .Agrawalet al[2]showed an active data mining process ,… 相似文献
997.
一种考虑杆件初始弯曲的非线性杆单元 总被引:1,自引:0,他引:1
在假定杆件初始弯曲为半波正弦曲线的基础上,提出考虑初始弯曲的非线性杆单元,推导了轴力与轴向变形的关系和轴向切线刚度的表达式,得到了初始弯曲对轴向刚度的影响系数.分析表明,初始弯曲影响与刚度比、初始弯曲幅值、轴力大小以及杆单元长度有关.结合某索拱结构工程实例,研究不同初始预应力取值下,杆件初始弯曲对结构非线性稳定性能的影响程度和影响规律,结果表明:杆件初始弯曲对结构屈曲前的整体刚度影响很小,但对结构的极限荷载与屈曲后性能影响较大;初始预应力取值的增加对结构的位移控制非常有效,但是对结构的刚度影响却很小;在不同初始预应力取值下,极限荷载随杆件初始弯曲变化的规律相似,并且都接近于线性.非线性杆单元能够广泛应用于桁架结构和网格结构的设计与分析,在考虑杆件初始弯曲后,将使结构的设计与分析更加合理、更加科学. 相似文献
998.
ESP飞灰对燃煤锅炉烟气汞的吸附特性 总被引:13,自引:0,他引:13
用氮气(N2)等温吸附(77K)测量了一座600MW煤粉锅炉电厂静电除尘器(ESP)各个电场飞灰的比表面积、孔径、孔比表面积、孔容积和孔分布,采用扫描电镜(SEM)和X射线能谱分析仪(EDX)分析了飞灰颗粒表面结构和化学组分.结果表明,颗粒粒径越小,比表面积越大,飞灰的汞吸附趋于增加.飞灰含碳量与汞含量呈正相关关系,亚微米级颗粒物对汞的吸附不仅与其比表面积有关,而且与其比表面积的利用率有关.静电除尘过程中飞灰的孔隙结构在不断地变化和发展,孔分布越宽越有利于对汞的吸附,微孔越发达且可利用率越高,越有利于汞的被吸附. 相似文献
999.
探讨了适合厚管壁条件下的电容层析成像图像重建算法.针对厚管壁管道内几种不同流型,分别采用LBP算法、Landweber迭代算法和BP神经网络对8电极电容传感器进行成像重建计算.结果表明:在厚管壁情况下,LBP算法重建的图像质量很差;Landweber迭代算法在层流下的重建效果好于核心流和环状流;而BP神经网络算法可以有效重建管道内的介质分布,但对于没有训练到的任意流型,其重建效果不够理想. 相似文献
1000.
界面反应及界面张力对Sn-Zn-Bi焊料润湿性的影响 总被引:2,自引:0,他引:2
通过合金化的方式得到了Sn-Zn-Bi三元及Sn-Zn-Bi-Nd四元无铅焊料,采用润湿平衡法测量了其润湿力和润湿时间,并对润湿后的焊料/Cu界面组织进行了分析.结果表明:Bi元素不参与焊料/Cu界面的扩散反应,但能够通过吸附作用降低界面张力,从而提高焊料在Cu基底上的润湿力;Zn元素优先向焊料/Cu界面进行扩散形成Cu5Zn8金属间化合物,且扩散层随焊料中Zn含量的提高而增长,此时固-液界面张力方向发生改变,润湿力提高,但润湿时间延长;Nd元素的作用类似于Bi,既能提高焊料的润湿力,也能够缩短润湿时间,是一种改善Sn-Zn基焊料润湿性的有效元素. 相似文献