A novel interference suppression scheme for global navigation satellite systems using antenna array

This paper considers interference suppression and multipath mitigation in Global Navigation Satellite Systems (GNSSs). In particular, a self-coherence anti-jamming scheme is introduced which relies on the unique structure of the coarse/acquisition (C/A) code of the satellite signals. Because of the repetition of the C/A-code within each navigation symbol, the satellite signals exhibit strong self-coherence between chip-rate samples separated by integer multiples of the spreading gain. The proposed scheme utilizes this inherent self-coherence property to excise interferers that have different temporal structures from that of the satellite signals. Using a multiantenna navigation receiver, the proposed approach obtains the optimal set of beamforming coefficients by maximizing the cross correlation between the output signal and a reference signal, which is generated from the received data. It is demonstrated that the proposed scheme can provide high gains toward all satellites in the field of view, while suppressing strong interferers. By imposing constraints on the beamformer, the proposed method is also capable of mitigating multipath that enters the receiver from or near the horizon. No knowledge of either the transmitted navigation symbols or the satellite positions is required.     

Tearing, folding and deformation of a carbon-carbon sp-bonded network

A monolayer and a few layers of carbon sp²-bonded networks were torn and folded by the tip of an atomic force microscope at the steps on newly cleaved highly oriented pyrolytic graphite. It was found that the preferential breaking directions and folding axes are along the symmetry directions of the graphite hexagonal structure. Depending on the force exerted by the tip, breaking may occur along other directions. The torn part of the graphene sheet can even be stretched and deformed, and does not resume its original shape after release from the tip.     

一种控制盐层段井眼闭合率的钻井液密度新公式

针对钻井过程中钻遇的盐层段井眼蠕变缩径问题,利用弹塑性力学理论,蠕变本构方程采用Heard蠕变方程,在平面应变和均匀地应力假设下,推导出控制井眼收缩的钻井液密度新公式,该公式与前人推导的公式不同。通过理论分析,指出产生差异的根本原因在于蠕变应力差(极坐标下表示的径向应力与切向应力之差)公式的推导上,用有限元法计算结果对理论公式进行检验,证明是可行的。对文中的力学模型采用有限元法建模、求解,利用求解结果对各应力差公式进行验证,得出:根据文中公式计算结果与有限元法计算结果完全一致,而据前人公式计算结果偏离有限元计算值较大,从而间接证明了该钻井液密度新公式的推导更严密,更准确。     

热氧化磁控溅射金属锌膜合成一维ZnO纳米棒

利用退火热氧化射频磁控溅射金属锌膜的方法在Si(111)衬底上制备了一维Zn O纳米棒,同时用多种测试手段对样品的晶体结构、表面形貌和光学性能进行了研究.XRD,SEM和TEM的测试结果表明,Zn O纳米棒为单晶相六方纤锌矿结构,呈头簪状向外发散生长,直径在30～60 nm左右,其长度可达几μm.PL 谱测试结果表明:在波长为280 nm光的激发下,在372 nm处有强的近带边紫外光发射和516 nm处的较微弱深能级绿光发射.说明合成的一维Zn O纳米棒的结晶质量和光学性能优良     

数字振荡器的实现原理与仿真编程

鉴于数字信号处理中的实时应用问题，探讨了数字滤波器的实时实现原理，包括离散时间网络结构的作用和离散时间信号处理的特点，重点介绍了实时应用中实现数字滤波器的基本思想，运用MATLAB和所导出的通用数字振荡器的系统函数对一个非正弦数字振荡器进行了仿真编程，还讨论了有关实时处理的几个重要的系统性质，表达了作者对于当前学习和应用数字信号处理方法的观点。     

冷库多台冷风机电热融霜时间与温度双重自动控制方案

从节能和可靠运行的角度提出冷库多台冷风机电热融霜时间与温度双重自动控制方法.     

聚乙烯管材的国内外发展及应用

介绍国内外PE管材的现状和发展前景、以及管材专用料的生产、研究情况     

高度有序多孔氧化铝模板的制备工艺与生长机制的研究

采用二次氧化法制备出高度有序的多孔氧化铝模板，结合扫描电镜和原子力显微镜对其结构、形貌进行观察和表征。研究了铝箔预处理和温度等对多孔氧化铝模板孔洞有序性的影响，讨论了有序孔洞的自组织生长机理。     

光纤Bragg光栅监测钢筋混凝土结构应变的实验研究

研究了光纤Bragg光栅在钢筋混凝土结构应变监测中的应用。对其应变、温度灵敏系数进行标定,将其埋设在钢筋混凝土梁内,实现对结构内部应变的监测,并对其工作状态做出评价。实验结果与理论值、传统监测手段监测结果一致。研制出一种钢管封装Bragg光栅温度传感器监测温度,对光纤Bragg光栅的应变与温度的同时测量进行了研究。     

谐振式力传感器对其晶振频率稳定度的要求

为了寻找石英晶振频率稳定度对传感器影响的判据,根据石英谐振式力传感器的灵敏度阈值和量程与晶体的相关常数及结构参数间的关系,导出了反映谐振式力传感器研究水平的指标参数与晶体结构参数及晶振频率稳定度之间的关系式,为传感器的研究提供了依据。例如,欲制作量程阈值比达到105量级的传感器,所用晶振的频率稳定度必须优于108。