基于区域密度曲线识别网络上的多影响力节点

复杂网络多影响力节点的识别可以帮助理解网络的结构和功能,具有重要的理论意义和应用价值.本文提出一种基于网络区域密度曲线的多影响力节点的识别方法.应用两种不同的传播模型,在不同网络上与其他中心性指标进行了比较.结果表明,基于区域密度曲线的识别方法能够更好地识别网络中的多影响力节点,选中的影响力节点之间的分布较为分散,自身也比较重要.本文所提方法是基于网络的局部信息,计算的时间复杂度较低.     

中国东部地区城市基本公共服务区域差异演化

减小区际基本公共服务差异是消除区域发展鸿沟、实现中国区域均衡发展的重要前提, 分析城际公共服务差异, 推进基本公共服务均等化是提升中国东部地区城市群发展水平面临的重要难题. 以教育、文化体育、医疗卫生3个基本公共服务一级指标构建了城际基本公共服务测度体系, 运用泰尔指数和熵值法测量1985年、1995年、2010年、2015年中国东部沿海地区88个城市间总体水平差异及不同指标差异. 结果表明: (1)东部沿海地区城市的基本公共服务质量总体不高, 基本公共服务差距明显, 长三角、环渤海地区公共服务总体水平高于珠三角地区; (2)东部沿海地区城际文化体育、教育、医疗卫生公共服务水平区域差异程度相当; (3)东部沿海地区城际基本公共服务各指标差异程度整体呈下降趋势, 且高水平城市与低水平城市差距明显减小.     

用于热光伏系统的近场辐射光谱控制表面结构

为提升近场热光伏发电系统的能源转换效率和发电功率,设计了Ⅲ-Ⅴ族半导体表面的矩形光栅结构,以实现从热发射器到热光伏电池的近场辐射热流选择性调制.使用在近红外波段具有表面等离子体激元特性的掺杂氧化锌作为热发射器,在GaSb热光伏电池表面添加亚微米二维光栅结构,在近场间距下形成与表面波耦合的陷光效应,由此有选择性地增强了电池能带内的光谱辐射热流.有别于以往类似研究中常用的等效近似方法,开展了时域有限差分方法模拟,能够严格考虑周期性结构细节,结合以涨落耗散理论为基础的Langevin方法,直接计算了复杂结构参与的近场辐射传热问题,以此揭示表面结构影响近场辐射传热的物理机理.结果显示使用带表面结构的薄膜GaSb电池,可使辐射热流的光谱峰值达到同温度远场黑体辐射源情况下的2.84倍,且热流增益区集中在波长略短于电池能带的窄波段区间,适应高效率、高功率热光伏系统对辐射传热设计的要求.     

合成孔径雷达简缩极化干涉数据的植被高度反演技术研究

该文提出了一种利用合成孔径雷达简缩极化干涉数据进行植被高度反演的三阶段方法。将全极化干涉数据处理中的相干最优方法引入简缩极化干涉数据处理,由相位最优相干系数对应的最优相位获得体去相干系数和地表相位的初始估计,利用相干区域边界提取方法更新体去相干系数,得到精确的植被高度估计值。采用欧空局提供的L波段的模拟全极化干涉数据构造简缩极化数据集,将该数据用于植被反演,反演结果验证了提出方法的有效性。     

Dynamics of an Ultracold Bose Gas in Funnel-Shaped Potential

In this paper we develop a variational theory to study the dynamicproperties of ultracold Bose gas in a funnel external potential. We obtain one-dimensional nonlinear equation which describes the dynamics of transverse tight confined bosonic gas from three-dimension to one-dimension, and find one-dimensional s-wave scattering length which depends on the shape oftransverse confining potential. If the funnel trapping potential is strong enough at zero temperature, all transverse excitations are frozen. We find the dynamic equation which describes the Tonks-Girardeau gas and present a qualitative analysis of the experimental accessibility of the Tonks-Girardeau gas with funnel-trapped alkalic atoms.     

Pinning-controlled synchronization of complex networks with bounded or unbounded synchronized regions

This paper studies pinning-controlled synchronization of complex networks with bounded or unbounded synchronized regions. To study a state-feedback pinning-controlled network with N nodes, it first converts the controlled network to an extended network of N+1 nodes without controls. It is shown that the controlled synchronizability of the given network is determined by the real part of the smallest nonzero eigenvalue of the coupling matrix of its extended network when the synchronized region is unbounded; but it is determined by the ratio of the real parts of the largest and the smallest nonzero eigenvalues of the coupling matrix when the synchronized region is bounded. Both theoretical analysis and numerical simulation show that the portion of controlled nodes has no critical values when the synchronized region is unbounded, but it has a critical value when the synchronized region is bounded. In the former case, therefore, it is possible to control the network to achieve synchronization by pinning only one node. In the latter case, the network can achieve controlled synchronization only when the portion of controlled nodes is larger than the critical value.     

扩展有限元方法计算多夹杂问题时圆形夹杂与四边形单元的几何关系

用扩展有限元法XFEM(Extended Finite Element Method)解决夹杂问题时,夹杂与基质的界面把单元分成若干部分.求单元刚度矩阵时,需要分别在这各个部分求积分.找到便于程序编制的描述各积分区域几何形状的方法是亟待解决的问题.本文把各积分区域的形成过程看成是圆对四边形的多次切割.考虑切剩区域与圆的关系时,把不完整的边仍看作完整的边,把切剩区域看成是四边形或是切去一两条边的四边形.采用排列组合的方法,把它们与圆的所有位置关系列了出来.     

卫星角反射器有效衍射区域的研究

本文基于角反射器的几何结构模型,采用矢量形式的折反射定律,推导了在不同入射条件下有效衍射区域的数学表达式.通过数值模拟的方法分析了有效衍射区域的变化规律,以及该规律对远场衍射光强空间分布的影响.结果表明,随着光束入射角的增加,有效衍射区域逐渐减小,进而导致角反射器衍射强度发散程度增加.光束方位角的引入不会改变有效衍射区域的形状和衍射强度的总能量,而只会使其各自分布旋转方位角的大小.在不考虑大气效应的情况下,根据不同入射条件对应的衍射强度分布,并结合速差补偿理论,提出了一种全新的角反射器口径设计方法.     

Extension of grid separation in the finite difference time domain analysis for predicting time-resolved reflectance of an optical pulse from scattering medium with non-scattering regions

Extension of grid separation in the finite difference time domain (FDTD) analysis has been proposed for predicting time-resolved reflectance of an optical pulse from scattering medium with non-scattering (clear) regions. Grid separation in the previous FDTD analysis formulated by the author was limited to less than 0.5 mm. By introducing the alternative boundary conditions proposed by the author at the surface of scattering medium, the grid separation limit has been extended up to 1 mm. As a result, necessary time to analyze time-resolved reflectance has been reduced to less than a sixtieth without degrading numerical accuracy.     

Reducing the NMR sample volume using a single organic liquid: Increased sensitivity for mass-limited samples with standard NMR probes

A simple inexpensive protocol for confining an aqueous sample to the active region of a standard NMR probe is examined for high-resolution NMR. The aqueous sample is sandwiched between an inert perfluorinated organic liquid that has been exploited in the design of micro-coil NMR probes. The procedure is demonstrated with 3 mm NMR tubes at ambient and elevated temperatures but should be equally applicable to smaller diameter tubes. It is shown that confinement has minimal effects on line shape and provides at least a two fold increase in sensitivity over a conventional sample, for the same mass of solute.