空气孔辅助光纤的模式截止

光纤的截止波长是光纤设计的重要参量之一。利用全矢量正交函数模型对空气孔辅助光纤的模式截止特性进行了讨论。分析表明：由于光纤包层中存在空气孔,即使不考虑材料色散,包层的有效折射率也与波长有关;包层有效折射率由包层中空气孔的大小和波长决定,与芯子的掺杂浓度无关。在所研究的波长范围之内,与传统的w型光纤类似,在包层中空气孔的相对尺寸d／Λ较大时出现了基模截止现象。d／Λ从0．2到0．9变化时,光纤的各阶模式的截止波长都随之减小;各阶模式的截止波长随d／Λ变化曲线的斜率随模式阶次的升高而降低。     

Interaction of microbubbles with high intensity pulsed ultrasound

High intensity pulsed ultrasound, interacting with microbubble contrast agents, is potentially useful for drug delivery, cancer treatment, and tissue ablation, among other applications. To establish the fundamental understanding on the interaction of a microbubble (in an infinite volume of water) with an ultrasound pressure field, a numerical study is performed using the boundary element method. The response of the bubble, in terms of its shape at different times, the maximum bubble radius obtained, the oscillation time, the jet velocity, and its translational movement, is studied. The effect of ultrasound intensity and initial bubble size is examined as well. One important outcome is the determination of the conditions under which a clear jet will be formed in a microbubble in its interaction with a specific sound wave. The high speed jet is crucial for the aforementioned intended applications.     

Pauling's rules for oxide surfaces

Determination of surface structures currently requires careful measurement and computationally expensive methods since, unlike bulk crystals, guiding principles for generating surface structural hypotheses are frequently lacking. Herein, we discuss the applicability of Pauling's rules as a set of guidelines for surface structures. The wealth of solved reconstructions on SrTiO₃ (100), (110), and (111) are considered, as well as nanostructures on these surfaces and a few other ABO₃ oxide materials. These rules are found to explain atomic arrangements for reconstructions and thin films just as they apply to bulk oxide materials. Using this data and Pauling's rules, the fundamental structural units of reconstructions and their arrangement are discussed.     

公路连续梁桥在横向多车作用下的振动响应研究

为研究横向多车作用下连续梁桥的振动响应,通过ANSYS建立公路连续箱梁桥的三维实体有限元模型,采用三维整车模型模拟三轴自卸汽车,引入路面不平顺的激励作用,建立多车车桥耦合振动方程.采用自编Matlab程序对横向并排两车、纵向前后两车及单车工况下桥梁的振动响应进行对比研究.结果表明:横向两车工况下的冲击系数与单车工况下的冲击系数接近,且为单车工况结果的0.4～1.3倍;纵向两车工况下的冲击系数绕单车工况下的冲击系数上下波动,且为单车工况结果的0.037～43.887倍.多车工况下的桥梁振动响应与车速、桥跨、车辆间距、路面等级等多种因素有关.     

Effects of Annealing on the Properties of Gamma-Irradiated Sago Starch

The increase in health and safety concerns regarding chemical modification in recent years has caused a growing research interest in the modification of starch by physical techniques. There has been a growing trend toward using a combination of treatments in starch modification in producing desirable functional properties to widen the application of a specific starch. In this study, a novel combination of gamma irradiation and annealing (ANN) was used to modify sago starch (Metroxylon sagu). The starch was subjected to gamma irradiation (5, 10, 25, 50 kGy) prior to ANN at 5 °C (T_o-5) and 10 °C (T_o-10) below the gelatinization temperature. Determination of amylose content, pH, carboxyl content, FTIR (Fourier Transform Infrared) intensity ratio (R_1047/1022), swelling power and solubility, thermal behavior, pasting properties, and morphology were carried out. Annealing irradiated starch at T_o-5 promoted more crystalline perfection as compared to T_o-10, particularly when combined with 25 and 50 kGy, whereby a synergistic effect was observed. Dual-modified sago starch exhibited lower swelling power, improved gel firmness, and thermal stability with an intact granular structure. Results suggested the potential of gamma irradiation and annealing to induce some novel characteristics in sago starch for extended applications.     

BJT电路分析的FOURIER系数模型及多项式近似

为简化等效小参量法和谐波平衡法用于实际双极型晶体管（ＢＪＴ）电路的分析，提出了ＢＪＴ的Ｆｏｕｒｉｅｒ系数模型，并利用一种新方法—按主要谐波分量近似器件特性和分段非线性逼近─—给出了它的多项式近似．本文的结果，使谐波失真、频率稳定度等分析过程变得简单，对于ＢＪＴ电路的符号分析有重要意义。     

从机载激光雷达数据中提取电力线研究进展

介绍了国内外激光雷达测量技术在电网工程中的应用成果,并以电力线提取的基本流程为主线,详细阐述了国内外近几年提取电力线的已有方法,并对各个方法进行分析评价,最后展望了激光雷达技术应用于电力线提取的前景．     

汽车发动机压缩压力及转速现场测试系统

介绍了一种用于现场测试汽车发动机压缩压力及转速的测试系统。该系统采用通用的个人计算机、少量的硬件和自选开发的采集分析软件组成,可现场测量发动机装车电瓶驱动下的压缩压力和转速,以利于分析装车发动机的技术状况和性能。还介绍了如何用软件的办法简化系统硬件,从而使该测试系统更适于现场测试。     

强非线性非自治系统的计算机符号分析

本文论述了一种计算机符号分析方法，能用来自动快速地分析求解强非线性非自治系统，得出以简单符号算式表达的稳态周期解。其主要分析方法基于等效小参量法，是利用计算机代数系统ｍｕＭＡＴＨ的写作语言ｍｕＳＩＭＰ编写而成．本文的结果对于实际的非线性电路与系统的符号分析具有重要意义。