Mode I–III Decomposition of the J‐integral from DIC Displacement Data

This paper presents the implementation of the decomposition method on digital image correlation (DIC) obtained displacement fields to obtain J‐integral results (J) and respective stress intensity factors (SIFs). DIC is increasingly used with the J‐integral approach in experimental mechanics to obtain J estimates from complex fracture processes. In this approach, the decomposition method is applied to DIC displacement fields for the first time. Here, displacement fields are separated before stresses and strains are computed, so that subsequent computation of separate J or SIF components may follow the classical full‐field J‐integral approach. The sensitivity of the decomposition method to experimental errors is investigated using synthetically generated errors imposed on crack tip displacement fields (Williams' series), from which improvements to the procedure are proposed. The method is experimentally tested on PMMA Arcan specimens under mode I, II, and III, and mixed‐mode I–III loading. Test results were compared to fracture toughness values obtained from ASTM tests and literature with close agreement.     

零模间色散三芯光子晶体光纤

为了研究纤芯掺杂低折射率材料后三芯光子晶体光纤中任意两超模之间的模间色散特性,采用全矢量有限元法进行了仿真,取得了模间色散系数、零模间色散波长随纤芯折射率和结构参量变化的数据。结果表明,通过调节纤芯折射率、纤芯直径、空气孔直径以及孔间距这4个结构参量,可以使任意两超模间的模间色散在两个常用波段1.31m和1.55m处为0。该结果对于消除基于模分复用的光纤不同模式间因为模间色散导致的脉冲失真和实现零模间色散的模分复用技术是有帮助的。     

网络教学平台在教学中的应用初探

虽然我们已经迈进二十一世纪有十几年了,科学技术的发展也是日新月异,但是在实际的教学过程中,新的技术在教学中的应用并不广泛、全面。本文以高校计算机基础教学课程为例,分析在新技术支持下的网络教学平台在教学中的初步应用。     

一维磁流体掺杂光子晶体缺陷模的磁控可调特性

磁流体的有效介电常数 与磁性粒子体积分数P和外加磁场因子 有关。本文首先计算了水基MnFe2O4磁流体的有效折射率随纳米磁性粒子体积分数P和外加磁场强度因子 的变化关系,发现通过调节外加磁场因子 的大小可实现不同纳米磁性粒子体积分数P的磁流体具有相同的有效折射率。然后,应用传输矩阵法,数值模拟了水基MnFe2O4磁流体中的纳米磁性粒子体积分数P=0.745时结构为(AB)8C(BA)8的一维磁流体掺杂光子晶体的透射谱。结果表明：缺陷模随着磁流体有效折射率nc的增大出现红移现象,即缺陷模中心波长随着随有效折射率nc的增大而变长,最大改变量为36.6nm。最后讨论了缺陷模品质因子 ,发现缺陷模半峰值带宽 不变,缺陷模品质因子 与缺陷模波长 随磁流体有效折射率nc的变化具有相同的线性变化特性,即品质因子 随有效折射率nc的增大而增大。     

“现代控制理论”课程教学改革研究与探索

本文通过分析“现代控制理论”课程的教学现状,指出教学过程中存在理论内容过多,师生互动较少,教学模式单调,考核方式不科学等问题。针对这些问题,本文从调整教学内容、丰富课堂教学模式、开展课外实践活动、建立交流网站和改进考核方式等方面进行研究和探索,提出了一些改革措施。     

包层折射率均匀调制LPFG光谱特性研究

介绍了光纤光栅发展的过程,阐述了光纤光栅的各种常用写制方法以及目前LPFG的发展现状,分析了耦合模理论;基于耦合模理论在纤芯折射率均匀调制的LPFG中的应用,利用Matlab软件对LPFG的光谱进行模拟,将耦合模理论进行修改,给出了单侧写制的LPFG的光谱图,提出了多侧写制LPFG的模型及曝光均匀度的概念。     

Thermal resistance of side by side multi-chip package: Thermal mode analysis

The thermal mode analysis is used in this paper to optimize the thermal management with optimal locations and chip sizes for multi-chip package. The average thermal resistance is defined and analyzed. The spreading thermal resistance can be expanded into Fourier series so that the thermal modes can be established. For the infinite thermal modes, only a few terms are needed to be considered due to the rapid convergence of solution. The optimal locations and chip sizes can then be determined by using the first few modes to reduce the thermal resistance as minimal as possible. The optimal locations have the cosine wave property so that the wave nodes might be the suitable sites. On the other hand, the optimal chip sizes have the cardinal sine property which decays monotonously. For given optimal locations, the optimal chip sizes are determined by certain modes. These special modes can be used to analyze the range of optimal locations and chip sizes.     

用于速调管的一维光子晶体圆柱腔分析

运用ISFEL3D软件对一维光子晶体圆柱腔和金属圆柱腔进行仿真和分析。研究结果表明,一维光子晶体圆柱腔中与TM010模相邻的TM910模只存在于最外层介质中,频率间隔为213 MHz,不会影响TM010模;一维光子晶体圆柱腔的特性阻抗(94.9Ω)比金属圆柱腔(129Ω)要小,但均匀性要好;在一维光子晶体圆柱腔两端连接漂移管后,TM010模所受影响很小,说明一维光子晶体圆柱腔具有较强的抗干扰能力,这是将一维光子晶体圆柱腔应用在高射频段速调管方面的前提条件。     

国内外移动虚拟运营商业务模式与经验探讨

首先介绍了移动虚拟运营商的业务特点,然后阐述了虚拟运营商的几种业务模式和基础运营商合作策略以及基于特定业务模式下的虚拟运营商网络架构和特点,最后结合国内电信业现状和国外成功的虚拟运营商案例,为国内虚拟运营商的业务发展归纳出若干经验并提出相关建议。