一种基于小波包变换的双模噪声中信号检测

利用多尺度小波包变换良好的时频局部分析能力,对一类非高斯噪声--双模噪声的统计特性进行研究.经过实际计算及仿真比较,对于两种双模噪声模型,随着双模噪声序列长度的增加,双模噪声小波包子空间变换系数都将近似服从高斯分布.通过仿真,证实小波包检测系统的检测性能不仅跟输入双模噪声的模型无关,而且比传统的高阶统计量检测系统、经典检测系统的检测性能都要好.     

MULTIPLE SOLUTIONS TO SINGULAR BVPS WITH VARIABLE COEFFICIENT ON THE HALF-LINE

This paper is concerned with a singular second-order nonlinear boundary value problem with a time depending on derivative operator and posed on the positive half-line. The nonlinearity is derivative-dependent, which has singularities at t=0 and/or x=0, and may change sign. The method of the upper and lower solutions on unbounded domains combined with the topological degree theory are employed to prove the existence and multiplicity of solutions.     

一种基于小波包和双谱的信号分析方法

在高斯噪声背景下,为了尽可能地消除噪声的干扰来提取有用信息,提出了一种基于小波包和双谱对加性高斯噪声信号进行处理的方法。主要利用小波包变换良好的时频分析能力和双谱对高斯噪声不敏感,不但能够抑制噪声、提高信噪比,而且可以得到信号幅度、相位、能量、非线性等丰富的特征信息。最后仿真表明了此方法分析信号的可行性和优越性。     

Understanding Chemical Reactivity in Extended Systems:Exploring Models of Chemical Softness in Carbon Nanotubes

Chemical reactivity towards electron transfer is captured by the Fukui function.However,this is not well defined when the system or its ions have degenerate or pseudo-degenerate ground states.In such a case,the first-order chemical response is not independent of the perturbation and the correct response has to be computed using the mathematical formalism of perturbation theory for degenerate states.Spatialpseudo-degeneracy is ubiquitous in nanostructures with high symmetry and totally extended systems.Given the size of these systems,using degenerate-state perturbation theory is impractical because it requires the calculation of many excited states.Here we present an alternative to compute the chemical response of extended systems using models of local softness in terms of the local density of states.The local softness is approximately equal to the density of states at the Fermi level.However,such approximation leaves out the contribution of inner states.In order to include and weight the contribution of the states around the Fermi level,a model inspired by the long-range behavior of the local softness is presented.Single wall capped carbon nanotubes(SWCCNT) illustrate the limitation of the frontier orbital theory in extended systems.Thus,we have used a C360 SWCCNT to test the proposed model and how it compares with available models based on the local density of states.Interestingly,a simple Hü ckel approximation captures the main features of chemical response of these systems.Our results suggest that density-of-states models of the softness along simple tight binding Hamiltonians could be used to explore the chemical reactivity of more complex system,such a surfaces and nanoparticles.     

基于物联网的配网户外箱柜预警远程智能监控系统

针对传统配网户外箱柜采用人工巡检方式存在耗时长、效率低和可靠性差等问题,文中提出了一种基于物联网的配网户外箱柜预警远程智能监控系统。该系统以物联网技术作为核心架构,对监测系统的终端感知系统、云平台管理系统和客户端系统功能进行了设计,具备监测数据的分布式计算和箱柜故障主动预警功能。结果表明：设计的系统能够更及时、全面的对户外箱柜状态进行监测和主动预警,为户外箱柜的安全管理提供了可靠有效的数据支撑。     

全固态中波发射机天调网络的防雷对策

中波发射机的研发工作随着科技快速发展而取得较大进步,发射机结构并呈现出越来越复杂的态势,同时对防雷也提出了较高要求.本文首先对雷电和天调网络进行论述,然后从微亨级电感线圈LO、石墨放电球、隔直电容器CO、移相网络这四个天调网络防雷对策进行探讨,并通过案例说明其优化策略,确保波发射机天调网络有利于中波发射机的平稳运转.     

短波电台发射控制系统的应用探讨

随着短波无线电的广泛运用,其独特的抗毁性能逐渐被重视并应用在通信中,这使得短波通信系统中核心的发射控制系统逐渐成为人们关注的焦点。本文以发射控制系统在实际应用中的运行现状为基础,对该系统的应用进行探讨。     

GSI 对最重的靶元素254Es 的首次轰击

在10月10—18日之间,在GSI,人们利用尤尼拉克(UNILAC)的束流对99号元素锒的同位素~(254)Es(半寿命T_(1/2)=276天)进行了首次轰击,这是迄今使用的最重的靶元素;该实验用了2μg 的Es 同位素,这几乎是世界上仅有的库存。实验是由劳伦斯利弗莫尔实验室和GSI 合作完成的,其目的是想用~(16)O,~(18)O和~(22)Ne 作炮弹对~(254)Es 进行轰击,找到生成丰中子重锕系元素和超锕系同位素的最佳反应条件。去年在利弗莫尔的离线化学实验表明,这个方法将被认为是这次实验的唯一有效的。     

Ag_(60)纳米颗粒[{Cl@Ag_(12)}@Ag_(48)(dppm)_(12)]的结构(其中dppm=双(二苯基膦基)甲烷)（英文）

本文合成一种新的双膦连接Ag_(60)纳米团簇[{Cl@Ag_(12)}@Ag_(48)(dppm)_(12)],并通过X射线晶体学进行表征.二十面体的银处于核心位置,里面是中心氯化物组成,外面有48个银原子/离子的包裹,顶端是12个双(二苯基膦基)甲烷(dppm)配体.同时利用密度泛函理论对阳离子[{Cl@Ag_(12)}@Ag_(48)(dppm)_(12)]~+进行计算,以确定该结构是否对应于核心数n=58的超原子.DFT计算的优化结构与X射线一致,但是HOMO-LUMO的能差并不能保证共超级稳定性.