Matched Filter Based Spectrum Sensing When Primary User Has Multiple Power Levels

In this paper,we investigate the matched filter based spectrum sensing in a more reasonable cognitive radio(CR) scenario when the primary user(PU) has more than one transmit power levels,as regulated in most standards,i.e.,IEEE 802.11 Series,GSM,LTE,LTE-A,etc.This new multiple primary transmit power(MPTP) scenario is specialized by two different targets:detecting the presence of PU and identifying the power level.Compared to the traditional binary sensing where only the presence of PU is checked,SU may attain more information about the primary network(making CR more "intelligent") and design the subsequent optimization strategy.The key technology is the multiple hypothesis testing as opposed to the traditional binary hypothesis testing.We discuss two situations under whether the channel phase is known or not,and we derive the closed form solutions for decision regions and several performance metrics,from which some interesting phenomenons are observed and the related discussions are presented.Numerical examples are provided to corroborate the proposed studies.     

抵御海啸的住宅——为prajnopaya基金会而设计

4个小的核心比1个大的核心的强度要高模型图所示是在没有顶部限制的墙壁上的压力,变形平行于墙壁的水平位移,SAFE(R)的墙头移动明显小于目前建成的住房。较小的墙头变形意味着倒塌的门槛承受着更高的压力,是因为砌石墙的倒     

基于广义S变换的吸收衰减梯度检测

利用时频分析可以对地震波进行时频分解,进而获得地震波高频段吸收衰减梯度,用于油气检测。然而当地震记录中高频干扰较强时,高频段时频谱的吸收衰减梯度并不能很好反映真实的吸收衰减情况。本文提出利用目前时频分辨能力较高的广义S变换求取地震波低频段时频谱的衰减梯度,并与高频段的吸收衰减梯度进行对比,以期更好地指示油气。理论推导、数值模拟及实际应用结果表明:基于广义S变换的低频吸收衰减梯度可以与高频吸收衰减梯度相互佐证,更可靠地指示油气的存在。     

页岩气勘探开发对地球物理技术的需求

近几年来,伴随着建设低碳经济的需要和对清洁能源需求的增长,页岩气产业发展迅速升温,特别是北美页岩气的发展已经改变了现今能源供应格局。我国页岩气资源潜力巨大,开发前景广阔,已经引起人们的高度重视。我国页岩气勘探开发仍处于起步阶段,特别是地球物理技术在页岩气勘探开发中究竟具有什么样的作用,还存在一些困惑。本文通过页岩气地球物理技术的需求分析和对未来发展的展望,明确指出地球物理技术作为页岩气储层评价和增产改造的关键技术,将在页岩气勘探开发中发挥重要的作用。     

基于波前构建法的TTI介质射线追踪

射线(群速度)方向与旅行时梯度(相速度)方向不一致,使得TTI介质的射线追踪变得非常困难。传统的以弹性参数表示的各向异性射线追踪系统比各向同性条件下要复杂得多,而且在每一步都要求通过解特征值问题来计算极化矢量,使得整个射线追踪过程相当耗时。鉴于此,本文引入一种用相速度和群速度重构的射线追踪系统,该射线追踪系统与各向同性条件下的完全相似,从而简化了TTI介质的射线追踪问题。在综合考虑多种走时计算方法的优劣后,选择波前构建法进行射线追踪和波前传播的计算。将简化的射线追踪系统与波前构建法的优势相结合,得到了简单、高效的TTI介质射线追踪方法,并通过模型试算验证了此法的可行性。     

利用零井源距VSP资料进行品质因子反演

品质因子Q值是描述地震波衰减的一个重要物理参数,它描述了介质非完全弹性特征,是地层内部本质特征,所以研究和估算Q值在地震勘探中的作用越来越重要。谱比法和质心频移法是现在常用的两种方法。本文详细介绍了两种方法的原理并用无噪声理论模型验证了两种方法的可行性。反演结果显示在无噪声的条件下两种方法都能很好地估算介质的品质因子。通过对含有不同强度噪声的理论数据、全波场理论数据和实际零井源距VSP数据的处理,对两种方法进行了比较。结果表明,质心频移法反演的结果比谱比法更精确、更可信。     

负热膨胀反钙钛矿锰氮化合物的研究综述

反钙钛矿结构锰氮化合物是近年发展起来的一类具有各向同性、负热膨胀系数及负热膨胀温度区间可调、金属性能及力学性能优良的新型负热膨胀材料,展现出重要的应用潜力.本文从负热膨胀材料的发展历史、化合物体系、制备方法、负热膨胀性能影响因素及微观机理等方面,阐述了反钙钛矿结构锰氮化合物负热膨胀材料的研究现状及最新发展动态,并对其发展前景进行了分析和展望.     

沿空巷破碎煤体自燃耗氧及升温特征数值模拟

为研究巷道顶煤和煤柱破碎后由漏风引起的自燃耗氧及升温规律,在质量、动量和热量守恒模型的基础上利用FLUENT软件求解了沿空巷周围破碎煤体的稳态氧气分布和温度的动态变化过程。计算结果表明：在煤柱较完整的情况下,顶煤的氧气浓度分布高于煤柱,但二者都具有自然发火的危险。由于散热作用,高温区离二者的漏风边界都有一定的距离,顶煤升温速率较煤柱更快。在改变漏风强度后,高温区位置和范围也会随之改变。此研究结论可以帮助缩小现场火源区的寻找范围,以便及时采取措施抑制自燃。     

Development of High Deformability Pipeline Steel

Based on strain-based design, high deformability X70 high strength pipeline steel with dual-phase microstructure has been developed, which can be laid in the seismic, the cold or the deepwater region. The results illustrated that the developed X70 steel has the stress-strain curve like round house and it shows good anti-transformation characteristic, high uniform deformation(≥10%), enhanced n-value(≥0.10), and the low yield-tensile ratio Y/T(≤0.85). The dual-phase microstructure of ferrite and bainite conta...     

Model updating based on incomplete modal data

The objective of model updating is to improve the accuracy of a dynamic model based on the correlation between the measured data and the analytical (finite element) model. In this paper, we intend to update the mass and stiffness matrices of an analytical model when only modal frequencies or spatially incomplete modal data are available. While the proposed method is systematic in nature, it also preserves the initial configuration of the analytical model, and physical equality and/or inequality constraints ...