An analysis of seismic attenuation in random porous media

The attenuation of seismic wave in rocks has been one of the interesting research topics, but till now no poroelasticity models can thoroughly explain the strong attenuation of wave in rocks. In this paper, a random porous medium model is designed to study the law of wave propagation in complex rocks based on the theory of Biot poroelasticity and the general theory of stochastic process. This model sets the density of grain, porosity, permeability and modulus of frame as random parameters in space, and only one fluid infiltrates in rocks for the sake of better simulation effect in line with real rocks in earth strata. Numerical simulations are implemented. Two different inverse quality factors of fast P-wave are obtained by different methods to assess attenuation through records of virtual detectors in wave field (One is amplitude decay method in time domain and the other is spectral ratio method in frequency domain). Comparing the attenuation results of random porous medium with those of homogeneous porous medium, we conclude that the attenuation of seismic wave of homogeneous porous medium is far weaker than that of random porous medium. In random porous media, the higher heterogeneous level is, the stronger the attenuation becomes, and when heterogeneity σ = 0.15 in simulation, the attenuation result is consistent with that by actual observation. Since the central frequency (50 Hz) of source in numerical simulation is in earthquake band, the numerical results prove that heterogeneous porous structure is one of the important factors causing strong attenuation in real stratum at intermediate and low frequency.     

Generalized Bosbach states: part I

States have been introduced on commutative and non-commutative algebras of fuzzy logics as functions defined on these algebras with values in [0,1]. Starting from the observation that in the definition of Bosbach states there intervenes the standard MV-algebra structure of [0,1], in this paper we introduce Bosbach states defined on residuated lattices with values in residuated lattices. We are led to two types of generalized Bosbach states, with distinct behaviours. Properties of generalized states are useful for the development of an algebraic theory of probabilistic models for non-commutative fuzzy logics.     

微波消解ICP-MS测定鲜竹笋中7种微量元素

建立同时检测鲜竹笋中铬、铜、锌、砷、镉、汞、铅等7种元素的分析方法。竹笋样品在硝酸介质中经微波消解,用电感耦合等离子体质谱(ICP-MS)检测,全定量法采集数据。校准曲线线性良好,相关系数在0.9937—1.0000之间;检出限为0.005—0.202μg/L;加标回收率在88.96%—110.5%;精密度RSD小于6.09%;国家标准样品西红柿叶(GSBZ51001-94)中几种元素的测定值都在标准范围内。该方法具有灵敏、可靠、快速、准确等优点,适用于竹笋中微量元素的分析测定。     

Vanishing viscosity limit of Navier–Stokes Equations in Gevrey class

In this paper, we consider the inviscid limit for the periodic solutions to Navier–Stokes equation in the framework of Gevrey class. It is shown that the lifespan for the solutions to Navier–Stokes equation is independent of viscosity, and that the solutions of the Navier–Stokes equation converge to that of Euler equation in Gevrey class as the viscosity tends to zero. Moreover, the convergence rate in Gevrey class is presented. Copyright © 2017 John Wiley & Sons, Ltd.     

Computation offloading balance in small cell networks with mobile edge computing

Wireless Networks - As a promising way to offset the low computation capacity of user equipments (UEs), mobile edge computing (MEC) has attracted great attention of academy and industrial recently....     

Ge_xSi_1-x/Si异质结构的近红外吸收光谱测量

测量分析了采用 RRH/VLP—CVD 方法外延生长的 Ge_xSi_(1-x)/Si 异质结构中 Ge_xSi_(1-x)合金薄层的近红外吸收光谱。由谱线计算出 Ge_(0.15)Si_(0.85)与 Ge_(0.45)Si(0.55)合金层的带隙分别为1.02eV 和O.88eV,与相同组分的体合金一致。结果表明用红外吸收光谱测量研究异质结构薄层材料的能带结构及带隙是一种准确、简便的方法。     

调制掺杂Al_xGa_(1-x)As/GaAs异质结持久光电导的光谱响应

本文在77 K下研究了调制掺杂 n-Al_(0.3)Ga_(0.7)As/GaAs异质结持久光电导的光谱响应.结果表明,掺 Cr GaAs衬底中Cr深能级上电子的激发和 Al_xGa_(1-x)As中DX中心的光离化都产生持久光电导.     

Pt/Si界面化学键性质的研究

在超高真空系统中,超薄层 Pt淀积膜原位蒸发在原子清洁的 Si(111)表面上形成 Pt/Si界面.利用光电子谱技术(XPS和UPS)研究了Pt/Si 界面的化学性质.测量了Si2p和Pt 4f芯能级和价带电子态,并着重研究这些芯能级及电子态在低覆盖度时的变化.由 Si(2p)峰的强度随 Pt 覆盖度的变化可以清楚证明:在 300 K下淀积亚单原子层至数个单原子层 Pt的 Pt/Si(111)界面发生强烈混合作用,其原子组伤是缓变的.由于Si原子周围的 Pt原子数不断增加,所以 Pt 4f芯能级化学位移随 Pt原子覆盖度的增加而逐步减小,而Si 2p芯能级化学位移则逐步增大.同时,Pt 4f峰的线形也产生明显变化,对称性增加;Si 2p峰的线形则对称性降低.淀积亚单原子层至数单原子层Pt的UPS谱,主要显示两个峰:-4.2eV(A峰),-6.0eV(B峰).A峰随着覆盖度的增加移向费米能边,而B峰则保持不变.这说明Ptd-Sip键合不受周围Pt原子增加的影响.利用Pt/Si界面Pt原子向Si原子的间隙扩散模型讨论了所观察到的结果.     

TD-SCDMA无线网络解决方案

TD-SCDMA系统独立组网时,在核心网部分及Iub接口部分的连接方式与已有的各种制式移动网络并无很大区别;组网时TD-SCDMA的特点体现在无线网络的覆盖解决方案中--普天信息技术研究院针对以下不同环境,提出了采用普天外置射频单元拉远并结合各种不同天线,实现了对不同环境的有效覆盖.市区的基本覆盖：采用智能天线;地铁和隧道的覆盖：采用多支路泄漏电缆;高层建筑的覆盖：采用分布式天线;高速公路和铁路沿线的覆盖：采用定向天线.     

关于Finsler几何中的Hadamard定理

本文利用陈省身最近在Ｆｉｎｓｌｅｒ几何中引进的一个特殊仿射联络，把Ｒｉｅｍａｎｎ几何中关于非正曲率流形的Ｈａｄａｍａｒｄ定理推广到Ｆｉｎｓｌｅｒ几何中．