基于SI1SI2R模型的异质群体重复感染的传染病建模与仿真

具有重复感染可能性的传染病由于不受抗体或疫苗等手段的阻碍,其传播范围会比普通传染病更加广泛,严重危害人类的身心健康,影响社会的和谐稳定,有必要对其传播规律进行探究,以便于更有针对性地制定应对策略。基于经典的传染病模型,本文构建考虑了传染病重复感染特征的SI1SI2R模型,定义异质性个体之间的交互及传播规则,并利用ABM仿真建模的方法探究具有重复性感染特征的传染病在异质性群体间的传播规律。仿真实验结果表明,此类传染病感染范围会随二次感染率的提升而增加,而异质性传播群体的组成不仅会影响感染人数的比例,还会影响其到达峰值的时间。因此,不仅要减小此类疾病反复感染的可能,还要根据传播群体的异质性提出更有效率的管理方案。     

交叉耦合腔体滤波器的设计与实现

通过对广义Chebyshev滤波器设计方法的深入研究,改进了由技术指标提取滤波器阶数和传输零点的综合方法;基于提出的分析模型,用Ansoft HFSS建立同轴腔体滤波器,对谐振腔的本征频率、耦合系数、抽头位置进行仿真计算。通过960MHz交叉耦合滤波器实例设计验证了该综合方法的有效性。     

CAN总线上语音与数据混合传输技术的研究

在排队论的基础上,文章对CAN总线协议建立了数学模型,并使用Matlab仿真平台分析了通信系统中语音与数据混合传输的性能,阐述了系统负载与帧传输平均时延的关系;使用微处理器PIC18F258、语音处理模块AMBE-2000、模数转换器PCM3500等芯片建立了一个小的硬件通信系统,进行了相应的实验测试,实现了语音与数据的混合传输。     

Reflection and transmission of ultrasound by a region of damaged material

Reflection and transmission of ultrasonic waves by a layer-like region of distributed microcracks in a bulk material has been investigated. It has been assumed that for sufficiently low frequencies and far away from the damaged layer, the reflected and transmitted waves are plane waves. By applying the Betti reciprocal theorem to a cell containingN cracks, and by choosing one elastodynamic state as the actual wave state and the other as a suitably chosen auxiliary wave state, the reflection and transmission coefficients have been expressed in terms of integrals over theN cracks. Simple expressions have been obtained for the case that all cracks are identical and parallel to each other. For the case that the cracks do not interact with each other, numerical results for the reflection and transmission coefficients are presented for a distribution of penny-shaped cracks. The variation of these coefficients with frequency, relative layer thickness and angle of incidence has been displayed in graphs.     

Cathodoluminescence study of crystalline quality of (Al, In, Ga)N heterostructures

Wurtzite InGaN/GaN and AlGaN/GaN heterostructures grown by metal organic vapor phase epitaxy were studied using cathodoluminescence (CL) combined with secondary electron microscopy (SEM) and scanning transmission electron microscopy (STEM). The surface morphology of samples containing InGaN layers is dominated by three types of defects: mesa-like hexagonal structures, hexagonal pyramids and micropipes. At the positions of pyramids the whole epilayer is thicker than at defect free positions, while at the positions of micropipes the whole epilayer is much thinner. The luminescence efficiency as well as the emission wavelength are influenced by these defects. In SL structures an increasing SL period thickness in the growth direction was observed. Panchromatic CL images show intensity inhomogeneity in both InGaN/GaN and AlGaN/GaN heterostructure, which are related to local variations of the interface quality. In AlGaN/GaN SQW structures a broad deep-level luminescence band at around 543 nm was observed, which is generally absent in InGaN/GaN heterostructures. This deep-level emission is strongly enhanced in defect positions.     

New Initiatives on Comparison of Whole-field Experimental and Numerical Results

Abstract: A simple approach to plot photoelastic fringes in grey scale and also in colour from finite element (FE) results is presented for better recognition and comparison with experiments. This requires proper identification of the plotting variable from FE results. For comparison with transmission photoelasticity, post-processing of principal stress difference is needed and for reflection photoelasticity the principal strain difference is to be used. The importance of the use of appropriate correction factors for comparison with reflection photoelastic results is emphasised. A newer approach to evaluate R _f for complicated geometries is indicated. Plotting of experimental fringes from finite elements is useful not only for validating the numerical model based on experiments but also for validating the experiments. To illustrate this, the problem of an interfacial crack in a bi-material Brazilian disc is discussed.     

安徽电信宽带骨干传输网构建方案介绍

随着IP业务的超常规发展，传输瓶颈日渐显现出来；以安微电信骨干传输网的发展规划为例，介绍安微电信宽带骨干传输网的构建方案。     

Characterization survey of Ga<Subscript>x</Subscript>In<Subscript>1−x</Subscript>As/InAs<Subscript>y</Subscript>P<Subscript>1−y</Subscript> double heterostructures and InAs<Subscript>y</Subscript>P<Subscript>1−y</Subscript> multilayers grown on InP

Low-bandgap, lattice-mismatched Ga_xIn_1−xAs (GaInAs) grown using InAs_yP_1−y (InAsP) compositional-step grades on InP is a primary choice for lightabsorbing, active layers in high-efficiency thermophotovoltaic (TPV) devices. The GaInAs/InAsP double heterostructures (DHs) show exceptional minority carrier lifetimes of up to several microseconds. We have performed a characterization survey of 0.4–0.6-eV GaInAs/InAsP DHs using a variety of techniques, including transmission electron microscopy (TEM). Dislocations are rarely observed to thread into the GaInAs active layers from the InAsP buffer layers that terminate the graded regions. Nearly complete strain relaxation occurs in buried regions of the InAsP grades. The buffer-layer strain prior to deposition of the active layer is virtually independent of the net misfit. Foreknowledge of this buffer-layer strain is essential to correctly lattice match the buffer to the GaInAs active layer.     

温州某办公大楼玻璃幕墙热工性能参数对空调冷负荷的影响

阐述了玻璃幕墙的传热系数K值与遮阳系数Sc的取值不同对空调冷负荷的影响;指出了不能单纯以K值来评估玻璃幕墙的热工性能的优劣,Sc值对热工性能影响更大,只有综合考虑K值和Sc值及环境因素,才能选择一个节能、环保的合适玻璃幕墙.     

FBG解调实时校正技术研究

在基于可调谐F-P的FBG解调系统中,由于驱动电压与扫描波峰的关系不固定,增加了系统误差。为此研究了实时校正技术。首先,通过方案比较和分析,设计了并联型的实时校正系统,此系统可以通过多个参考点实时校正PZT的非线性问题以及可调谐F-P滤波器的结构性误差。然后,通过实验分析了PZT驱动电压与可调谐F-P波峰的关系,设计了快速分段算法。最后,针对此系统,设计了以现场可编程门阵列(FPGA)为核心的信号处理单元,将解调系统的控制、滤波计算和数据压缩等电路集成在FPGA芯片内部,保证了系统的实时性。实验结果表明,该系统的均方误差为2.2pm,最大误差为6pm。解决了此类解调系统受可调谐F-P滤波器精度限制的问题,提高了测量精度。