基于SVD的通信信号背景下脉冲波形和初相估计

雷达侦察接收机往往侦察到的是通信和雷达脉冲的混合信号，如何从通信信号背景中有效提取出雷达脉冲波形，是现代雷达信号处理领域中的重要内容。针对这一问题，提出了一种基于奇异值分解的通信与雷达混合信号中脉冲波形估计算法。该算法通过对信号观测矩阵的奇异值分析和协方差矩阵的特征值分析，证明了观测矩阵的奇异值分解具有稳定性，并且奇异值分解能够最佳近似观测信号的线性特征，给出了一种利用左右奇异向量估计脉冲波形及其相对初相的方法。本文的算法适用于任意脉冲波形，并且能够在较低信噪比环境下估计脉冲信号波形和相对相位，仿真结果证明了算法的有效性。     

复合型土壤营养调理剂改良吉林省西部风砂土的试验研究

通过两年的盆栽试验,考察了8种风砂土营养调理剂对白菜生长的影响.结果表明,与单施无机化肥相比,同时施用无机化肥与泥炭或腐泥或其混合物或腐植酸液体肥,白菜的生长高度、最大叶宽、鲜重和干重都得到了提高;单施无机化肥或共同施用无机化肥和腐植酸液体肥对当年白菜生长效果显著,第二年白菜生长明显下降;用泥炭、腐泥或其混合物改良风砂土后,再施用无机化肥,不仅当年作物生长好于单施无机化肥的,而且具有后效性.由此可见,有机物料泥炭、腐泥与无机化肥等制成的有机无机复合型土壤营养调理剂,具有改良土壤结构、提供营养,兼有长效与短效双重功能,是风砂土改良的最佳选择.     

略论交城县旮旯水电站建设的必要性

简要介绍了交城县概况及其水文气象条件,从工程规划、水土保持、环境评价、经济评价等方面对交城县旮旯水电站项目建设的可行性和必要性进行了论证。     

Chromatin-remodeling complex specificity and embryonic vascular development

Vascular development is a dynamic process that relies on the coordinated expression of numerous genes, but the factors that regulate gene expression during blood vessel development are not well defined. ATP-dependent chromatin-remodeling complexes are gaining attention for their specific temporal and spatial effects on gene expression during vascular development. Genetic mutations in chromatin-remodeling complex subunits are revealing roles for the complexes in vascular signaling pathways at discrete developmental time points. Phenotypic analysis of these models at various stages of vascular development will continue to expand our understanding of how chromatin remodeling impacts new blood vessel growth. Such research could also provide novel therapeutic targets for the treatment of vascular pathologies.     

Liquid marbles.

The transport of a small amount of liquid on a solid is not a simple process, owing to the nature of the contact between the two phases. Setting a liquid droplet in motion requires non-negligible forces (because the contact-angle hysteresis generates a force opposing the motion), and often results in the deposition of liquid behind the drop. Different methods of levitation-electrostatic, electromagnetic, acoustic, or even simpler aerodynamic techniques-have been proposed to avoid this wetting problem, but all have proved to be rather cumbersome. Here we propose a simple alternative, which consists of encapsulating an aqueous liquid droplet with a hydrophobic powder. The resulting 'liquid marbles' are found to behave like a soft solid, and show dramatically reduced adhesion to a solid surface. As a result, motion can be generated using gravitational, electrical and magnetic fields. Moreover, because the viscous friction associated with motion is very small, we can achieve quick displacements of the droplets without any leaks. All of these features are of potential benefit in microfluidic applications, and also permit the study of a drop in a non-wetting situation-an issue of renewed interest following the recent achievement of super-hydrophobic substrates.     

On-chip natural assembly of silicon photonic bandgap crystals.

Photonic bandgap crystals can reflect light for any direction of propagation in specific wavelength ranges. This property, which can be used to confine, manipulate and guide photons, should allow the creation of all-optical integrated circuits. To achieve this goal, conventional semiconductor nanofabrication techniques have been adapted to make photonic crystals. A potentially simpler and cheaper approach for creating three-dimensional periodic structures is the natural assembly of colloidal microspheres. However, this approach yields irregular, polycrystalline photonic crystals that are difficult to incorporate into a device. More importantly, it leads to many structural defects that can destroy the photonic bandgap. Here we show that by assembling a thin layer of colloidal spheres on a silicon substrate, we can obtain planar, single-crystalline silicon photonic crystals that have defect densities sufficiently low that the bandgap survives. As expected from theory, we observe unity reflectance in two crystalline directions of our photonic crystals around a wavelength of 1.3 micrometres. We also show that additional fabrication steps, intentional doping and patterning, can be performed, so demonstrating the potential for specific device applications.     

国内大学出版社客户投诉处理工作探析

通过对中国大学出版社客户投诉处理工作的抽样调查,分析了大学出版社客户投诉处理工作中的问题以及开展这项工作的现实意义,提出了大学出版社客户投诉处理的对策。     

Infection of young Douglas-firs by dwarf mistletoe in the Southwest

Studies in several areas in Arizona and New Mexico show that dwarf mistletoe ( Arceuthobium douglasii ) is rare in young Douglas-firs growing under infected overstories. Less than 5% of the Douglas-firs under 26 years old and less than 6% of those under 1.4m tall were infected in 77 mistletoe-infested stands. Both percent infection and mean dwarf mistletoe rating of young Douglas-firs increased as tree age, height, and stand dwarf mistletoe ratings increased.