移动环境下网络病毒传播模型及其稳定性研究

考虑网络节点的随机移动, 基于平均场理论 提出一个移动环境下网络病毒传播的数学模型, 利用微分动力学系统理论研究了病毒传播行为. 研究表明, 当病毒基本再生数R₀ ≤ 1时, 网络中病毒逐渐消除, 系统的无病毒平衡点全局渐进稳定; 当R₀ > 1时, 网络中病毒持续存在, 系统的地方病平衡点全局渐进稳定.通过仿真验证了所得结论的正确性.     

"神舟"五号的空间环境保障

空间环境安全保障是载人航天器飞行安全和航天员生命安全保障的一个重要部分．文章从高层大气、高能辐射环境、流星体空间碎片和重大空间环境扰动事件等四个方面空间环境要素对载人航天的影响，介绍了空间环境预报中心为“神舟”五号载人飞行任务所作的空间环境保障工作．     

Inelastic tunneling in a double quantum dot coupled to a bosonic environment

Coupling a quantum system to a bosonic environment always give rise to inelastic processes, which reduce the coherency of the system. We measure energy-dependent rates for inelastic tunneling processes in a fully controllable two-level system of a double quantum dot. The emission and absorption rates are well reproduced by Einstein's coefficients, which relate to the spontaneous emission rate. The inelastic tunneling rate can be comparable to the elastic tunneling rate if the boson occupation number becomes large. In the specific semiconductor double dot, the energy dependence of the inelastic rate suggests that acoustic phonons are coupled to the double dot piezoelectrically.     

复杂地理环境的图像分割及电波传播特性

复杂地理环境是电波传播不可避免的传播环境,不仅不规则地形会对电波传播产生影响,不同的地表媒质对电波传播也会产生不同的影响。为了使得电波传播特性的预测结果更加地准确有效,通过图像分割算法实现地表环境的简单分类,同时对不同的媒质赋予不同的电磁参数,并结合数字高程模型（DEM)数据,实现了既具有地形起伏信息又具有地表电磁环境参数的复杂地理环境建模。在此基础上,对地表电磁环境信息做了网格剖分处理,利用抛物方程（PE）模型对复杂地理环境下的电波传播特性进行了预测。     

Functionalization of Graphene Oxide and its Biomedical Applications

Graphene oxide (GO) offers interesting physicochemical and biological properties for biomedicine due to its versatility, biocompatibility, small size, large surface area, and its ability to interact with biological cells and tissues. GO is a two-dimensional material of exceptional strength, unique optical, physical, mechanical, and electronic properties. Ease of functionalization and high antibacterial activity are two major properties identified with GO. Due to its excellent aqueous processability, amphiphilicity, surface functionalization capability, surface enhanced Raman scattering (SERS), and fluorescence quenching ability, GO chemically exfoliated from oxidized graphite is considered a promising material for biological applications. In addition, due to π-π* transitions, a low energy is required for electron movement, a property important in Biosensor and Bioimaging applications of GO. In this article, we present an overview of current advances in GO applications in biomedicine and discuss future perspectives. We conclude that GO is going to play a vital role in Biomedical applications in the near future.     

基于目标与环境FD模型的多特征检测算法适应性评估

智能变形、变色、变温、变谱技术发展趋势下,低特征目标加速实现与自然地物背景的特征融合,导致复杂自然背景环境下低散射、微反射、弱辐射目标的检测与评估愈发困难,特定场景下潜在威胁目标的检测方法快速决策与准确评估成为了难题.为了提升离散目标、伪装目标、弱小目标、异常目标等低特征目标与复杂自然背景环境融合场景下的多特征检测算法...     

Improvement of packet transmission scheduling and delivery rate in wireless Ad-Hoc networks

The principal purpose of Ad-Hoc wireless networks is to increase service efficiency in terms of transmission scheduling and packet transfer rate. The approaches that assume frame unicity to satisfy a given set of packets minimize the end-to-end delay. However, they do not guarantee a maximum packet delivery rate due to the difficulty of establishing robust paths for packet transfer across nodes deployed in the network, especially in a three-dimensional (3D) environment. The objective is to minimize the end-to-end delay by ensuring the maximum delivery of packets to their destinations. Furthermore, the signal-to-interference-and-noise-ratio (SINR) model is considered to optimize transmission scheduling. In this paper, an optimal node coordinates optimization approach is proposed to extend two recently investigated schemes in the literature (S-RDSP and I-RDSP). The developed algorithms, named S-MPDR and I-MPDR, seek to reduce the end-to-end delay by delivering a collection of inserted packets over a 3D environment while also maximizing the delivery rate of these packets. Desirability functions are used to evaluate the network’s performance in various scenarios involving two different environments, Level 0 and Level 1. Numerical results demonstrate that the developed algorithms outperform both schemes in terms of end-to-end delay and packet delivery rate. In the Level 0 environment, the overall minimum delay and packet delivery rate scores provided by S-MPDR are increased by 28% and 88% compared to S-RDSP, respectively. In comparison, those provided by I-MPDR are increased by 24% and 16% compared to I-RDSP. Similarly, in the Level 1 environment, the scores provided by S-MPDR are increased by 25% and 100% compared to S-RDSP, respectively, while those provided by I-MPDR are increased by 23% and 25% compared to I-RDSP.     

Optimal growth conditions for GdBa2Cu3O7 thin-film coated conductors characterized by polarized Raman scattering spectroscopy

High temperature superconducting GdBa₂Cu₃O₇ (GdBCO) thin films were grown by pulsed laser ablation. Textured MgO on metal substrates was used as a template for second generation wire applications. Growth conditions of GdBCO thin films were investigated for substrate temperature (T_s) and oxygen partial pressure (PO₂) during deposition. Superconducting critical currents of the films were obtained in the films grown at 790–810 °C of T_s and at 100–700 mTorr of PO₂. Scanning electron micrographs of the films revealed uniform and well-connected grains with some outgrown structures. X-ray θ–2θ scans of the films grown at 810 °C and 300–500 mTorr exhibited c-axis oriented texture. In-plane alignment and c-axis mosaic spread of the films were determined from X-ray Φ scans and rocking curves, respectively. Polarized Raman scattering spectroscopy was used to characterize optical phonon modes, oxygen content, cation disorder, and some possible second phases of the films. The Raman spectra of the films with large critical current density showed modes at 326–329 cm⁻¹, 444–447 cm⁻¹, 500–503 cm⁻¹ related to vibration of oxygen atoms. Origin of small peaks near 600 cm⁻¹ will be discussed as well. The information obtained from Raman scattering measurements will be useful for quality control of the conductors as well as optimization of the process conditions.     

叶型偏差对整机环境中涡轮性能的影响

叶型加工和装配的误差可能会对涡轮部件乃至发动机整机的性能产生显著的影响。本文针对某整机环境中的涡轮部件,采用数值模拟结合实验的方法,研究了涡轮叶型偏差对其气动性能的影响。结果表明:在整机环境中,叶型偏差首先导致涡轮部件气动性能的微小变化,而整台发动机的工作点随之改变,导致涡轮部件的来流条件、各级涡轮的转速和速度三角形以及其内部的流动细节均会发生明显的变化,最终叶型偏差对涡轮部件气动性能的影响被显著放大。     

Directed polymers in a random environment: Some results on fluctuations

We consider a polymer model on ℤ ₊ ^d where to each edgee is associated a random variable v(e). A polymer configuration is represented by a directed pathr and has a weight exp[-β ∑ _e ∈r ν(e)], withβ=1/T the inverse temperature. We extend some rigorous results that have been obtained for the ground state of this model to finite temperatures. In particular we obtain some upper and lower bounds on sample-to-sample free energy fluctuations, and also rigorous scaling inequalities between the exponents describing free energy fluctuations and transversal displacements of polymer configurations