新一代长波长红外探测器

文章旨在介绍适应于长波红外焦平面阵列技术发展的红外探测器，由于篇幅的关系，本文着重评述ＩｎＡｓＳｂ应变层超晶格红外探测器和ＧａＡｓ／ＧａＡｌＡｓ多量子阱红外探测器的特点、器件结构、主要制作工艺，性能参数，以及急需要解决的一些问题。     

低温烧结SrTiO_3晶界势垒高度的研究

本文利用双Ｓｃｈｏｔｔｋｙ势垒模型依据ＳｒＴｉＯ３晶界层电容器材料的Ｒ～Ｔ特性和室温下的Ｉ～Ｖ特性获得了晶界势垒高度随温度变化的关系．结果表明，势垒高度随温度的升高而增加．这一结果与用各不同温度下的Ｉ～Ｖ特性拟合所得到的势垒值基本相符．     

分析恒载效应的有限元方法

本文在Takabatake关于恒载对梁静、动力影响的研究工作的基础上,导出了梁考虑恒载效应的动力分析有限元公式,提出了荷载影响刚度矩阵的概念。分析了分布和集中两种恒载型式对简支梁和悬臂梁自振特性的影响。计算结果表明,用本文方法与Takabatake应用Galerkin方法和近似闭合解方法的结果吻合良好。同时由于本文采用了矩阵形式,不仅便于编制计算机程序,且使方法有更广泛的适用性和灵活性,可更方便地用于各种不同的构造和边界条件下的实际结构。     

PWM开关变换器统一建模法与谐波分析法的应用

介绍了PWM开关功率变换器电路的统一建模方法，并将谐波分析方法应用于电路分析中，理论和实例表明，这种方法容易得到电路变量的基波解和各次谐波解，以及电路的传递函数，具有容易理解和准确度较高的优点。     

潦河灌区农业水费计收现状分析及对策

阐述了潦河灌区农业水费计收现状，对水费计收现状进行分析并提出解决办法。     

Hydrothermal Synthesis of Acicular Lead Titanate Fine Powders

A pure, acicular lead titanate (PbTiO₃) fine powder with a white color has been prepared by hydrothermal synthesis. It is a new phase of PbTiO₃ with I 4 symmetry, cell parameters of a = 12.358 Å and b = 14.541 Å, and a density of 6.80 g.cm⁻³. The influences of pH (12.5 to 14.4), Pb/Ti ratio (1.0 to 1.6) in the feedstock, reaction temperature (130° to 230°C), time (0.25 to 4 h), starting materials, and additives on the formation of acicular PbTiO₃ under hydrothermal conditions have been investigated. The acicular PbTiO₃ with I 4 symmetry, referred to as the PX phase, can be converted to the perovskite-type (PE phase) of PbTiO₃ at about 605°C while its acicular morphology is essentially unchanged. The preferable conditions for preparing pure acicular PX-phase PbTiO₃ are that the pH is 13.0 to 14.0, Pb/Ti ratio is >1.3, reaction temperature is 170° to 200°C, time is 0.5 to 1.0 h, titanium butoxide (Ti[O(CH₂)₃CH₃]₄) is the starting material, and poly(vinyl alcohol) is an additive. The acicular grain of the PX phase is usually less than 100 nm in diameter and more than 1000 nm in length.     

Optical and thermal properties of poly(ethylene oxide) doped with MnCl2 salt

The optical and thermal properties of prepared poly(ethylene oxide)/MnCl₂ films were studied as a function of MnCl₂ concentration at room temperature. The observed optical energy gap (E_opt) and energy gap tail (ΔE) were determined from the measured absorption spectra. It was found that the optical energy gap decreases with MnCl₂ concentration, and the absorption coefficient reduces sharply at concentration of 5 wt% MnCl₂ compared with the neat PEO. Differential scanning calorimetry (DSC) measurement shows that the heat of fusion increases with the MnCl₂ concentration, while the melting point decreases. Correlation between the observed optical energy gap and heat of fusion is presented.     

Temperature Dependence of Ultra-Low-Frequency Dielectric Relaxation of Barium Titanate Ceramic

Based on a linear voltage ramp method, ultraslow dielectric relaxation of undoped BaTiO₃ ceramic has been carefully measured over the temperature range between − 180° and +120°C. Temperature dependence of the dielectric constant in the frequency range from 10 ⁻⁵ to 10⁻¹ Hz can be obtained using Kramers–Kronig equations. Close to the Curie temperature, the dielectric constant increases so rapidly that the Curie peak is overwhelmed. Two kinds of relaxation processes were observed in this experiment. Ferroelectric domain and mobile charge are proposed to be responsible for the relaxation over the temperature range. With temperature increasing, Maxwell–Wagner relaxation associated with mobile charge gradually dominates. From relaxation time constants at various temperatures, relaxation activation energies about 0.06 and 0.09 eV are identified.     

大型箱梁翼缘开洞有限元分析

应用有限元法分析了大型双腹箱形开洞梁，以孔洞宽度和位置为变量，探讨孔洞对梁的应力、应变及跨中挠度的影响规律．研究结果表明，随着洞位置向跨中移动，以及洞宽度的增大，跨中挠度增大较快．当孔洞与支座的距离大于0．3倍跨度时，跨中最大正应力会突然减小，但小于0．3倍跨度时，开洞对跨中最大正应力影响不大．随着孔洞断面宽度的增大，开洞断面下翼缘正应力逐渐增大，与材料力学计算结果差异越来越大，但该断面的剪应力却与材料力学计算值较为接近．最后，比较有限元计算值与材料力学计算值，得出修正系数供设计参考．