Enhancement of pyroelectric properties of lead-free 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 ceramics by La doping

Lead-free 0.94NBT-0.06BT-xLa ceramics at x = 0.0–1.0 (%) were synthesized by a conventional solid-state route. XRD shows that the compositions are at a morphotropic phase boundary where rhombohedral and tetragonal phases coexist. With increasing La³⁺ content pyroelectric coefficient (p) and figures of merits greatly increase; however, the depolarization temperature (T_d) decreases. p is 7.24 × 10⁻⁴C m⁻² °C⁻¹ at RT at x = 0.5% and 105.4 × 10⁻⁴C.m^−2 °C⁻¹ at T_d at x = 0.2%. F_i and F_v show improvements at RT from 1.12 (x = 0%) to 2.65 (x10 ⁻¹⁰ m v⁻¹) (x = 0.5%) and from 0.021 to 0.048 (m².C⁻¹) respectively. F_i and F_v show a huge increase to 37.6 × 10⁻¹⁰ m v⁻¹ and 0.56 m² C⁻¹ respectively at T_d at x = 0.2%. F_C shows values of 2.10, 2.89, and 2.98 (x10⁻⁹C cm⁻² °C⁻¹) at RT at 33, 100 and 1000 (Hz) respectively. Giant pyroelectric properties make NBT-0.06BT-xLa at x = 0.2% and 0.5% promising materials for many pyroelectric applications.     

发射装置异型壳体轮廓尺寸加工工艺改进

针对异型壳体外形轮廓加工尺寸超差问题,通过分析产品轮廓加工工艺过程,提出了工艺改进方案；通过调整工艺路线,制作工装,提高了产品的一次交检合格率,零件加工一致性也得到提高.     

欧洲生态住宅的气候适应性

本文从气候与能源出发,总结了生态住宅气候适应控制的两种方式,强调了其中被动式调控的重要性,通过解读实例从住宅型体、缓冲空间和表皮系统三方面阐述了欧洲生态住宅的气候适应性,以期为我国生态住宅的气候适应设计提供一些参考和启示。     

风力发电机的造型设计

通过对风力发电机的形态设计学研究、空气动力学方面的研究以及机舱内的人机工程学研究从而设计出不仅造型美观而且能提高整体运行的效率、使用寿命的风力发电机。     

大动态范围抗干扰导航接收机AGC 电路性能分析与优化设计

导航接收机的特点是信号比较微弱,通常淹没于噪声以下,其入口电平的波动几乎都由干扰引起。针对这一特点,存在干扰情况下,要求接收机的噪声系数不能显著恶化。射频通道的噪声系数是制约接收机噪声系数的因素之一,本文在给定射频通道噪声系数恶化容限的条件下,以射频通道能实现最大动态范围为优化目标,分析了动态范围及各级电路增益的求解方法;进一步,针对特殊的纯电阻网络AGC 电路,得到了更为简洁的求解方法;最后,本文给出了该类AGC 电路动态范围的设计实例并进行了测试,设计预期与测试结果得到较好的吻合。本文虽然针对导航接收机设计,但可推广应用于指导各类接收机的设计。     

圆柱面上不均布数字及刻线的加工

解决圆柱面上不等间隔数字及刻线的加工,可通过Pro/E或MasterCAM实现.采用Pro/E时,用"包络"工具将数字和刻线包络在圆柱面上,用草绘中的"使用边"工具生成"修饰"特征,用Pro/E制造模块定义加工参数,完成数字和刻线模拟加工并生成加工程序.采用MasterCAM时,按展开图在X-Y平面绘制数字及刻线,定义轮廓、加工刀具及参数和旋转轴,模拟并生成加工程序.     

Influence of thermal annealing on electrical and optical properties of indium tin oxide thin films

Transparent conducting indium tin oxide (ITO) thin films with the thickness of 300 nm were deposited on quartz substrates via electron beam evaporation, and five of them post-annealed in air atmosphere for 10 min at five selected temperature points from 200 °C to 600 °C, respectively. An UV–vis spectrophotometer and Hall measurement system were adopted to characterize the ITO thin films. Influence of thermal annealing in air atmosphere on electrical and optical properties was investigated in detail. The sheet resistance reached the minimum of 6.67 Ω/sq after annealed at 300 °C. It increased dramatically at even higher annealing temperature. The mean transmittance over the range from 400 nm to 800 nm reached the maximum of 89.03% after annealed at 400 °C, and the figure of merit reached the maximum of 17.79 (Unit: 10⁻³ Ω⁻¹) under the same annealing condition. With the annealing temperature increased from 400 °C to 600 °C, the variations of transmittance were negligible, but the figure of merit decreased significantly due to the deterioration of electrical conductivity. With increasing the annealing temperature, the absorption edge shifted towards longer wavelength. It could be explained on the basis of Burstein–Moss shift. The values of optical band gap varied in the range of 3.866–4.392 eV.     

输出高品质MATLAB图形的方法与技巧

介绍将MATLAB的输出图形及Simulink的仿真模型图转化为高品质图形文件格式的方法与技巧。该格式的图形满足国内外各种期刊杂志的出版要求，并且可直接输入到Word文档中，以实现图文混排。     

Gradient Structure of Image in Scale Space

We investigate the topological structure of an image and the hierarchical relationship between local and global structures provided by spatial gradients at different levels of scale. The gradient field curves link stationary points of the image including a local minimum at infinity, and construct the topological structure of the image. The evolution of the topological structure with respect to scale is analysed using pseudograph representation. The hierarchical relationships among the structures at different scales are expressed as trajectories of the stationary points in the scale space, which we call stationary curves. Each toppoint of the local extremum curve generically has a specific gradient field curve, which we call the antidirectional figure-flow curve. The antidirectional figure-flow curve connects between the toppoint and another local extremum to which the toppoint is subordinate. A point at infinity can also be connected to the toppoints of local minimum curves. These hierarchical relationships among the stationary points are expressed as a tree. As an application, we present the temporal segmentation of an image sequence based on the transition of the hierarchical structure.