On the Numerical Stability of the Precise Integration Time-Domain (PITD) Method

In this letter, the stability issue of the recently proposed 3-D precise integration time-domain (PITD) method is reinvestigated. It is found that the PITD is not unconditionally stable; its stability condition is strongly dependent on the preselected number of sub time-steps and sizes of numerical cells as well as the order of the approximation used. However, since the upper limit of time step is found to be proportional to the number of sub time-steps, the time step can be of a value much larger than the Courant-Friedrich-Levy limit of the conventional finite difference time domain. Numerical examples are presented to verify our analysis.     

Miniaturized Dual-Mode Ring Bandpass Filters With Patterned Ground Plane

Miniaturized dual-mode ring bandpass filters with a patterned ground plane are proposed. By loading the resonator periodically with the butterfly radial slot cells on the ground plane, the size of a ring filter is reduced along with an extended upper stopband. Based on the equivalent circuits, the mode-splitting characteristics and impact of the patterned ground plane on the electrical performances of the filter are investigated. A slotline ring filter with a patterned ground plane is also proposed. The miniaturization is achieved by loading the periphery of the slotline ring with the butterfly radial stubs at the backside. The filter has a higher first spurious response and deeper stopband rejection than a conventional microstrip ring filter. Measured results validate the analysis and theoretical prediction with good agreement.     

Effects of Dielectric Constant of Glass Substrates on Properties of Liquid Crystal Lens

The effects of the dielectric constant of the glass substrates on liquid crystal lens performances are studied. Lens properties and the optimum geometrical structure almost does not change with the dielectric constant. The driving voltages become low when glass substrates of high dielectric constant are used.     

基于嵌入式WINCE的图像采集系统的设计与实现

文章介绍了在嵌入式WINCE系统下开发USB摄像头图像采集系统的方法,给出并实现了基于三星S3C2410处理器的嵌入式图像采样系统的设计方案,并对如何编写Windows CE.Net下的摄像头图像采样USB驱动程序要点进行了讨论.因WINCE下没有考虑对众多USB设备的驱动,对于每种USB设备都要自己编写相应的驱动,所以本文实现了较通用的USB摄像头驱动编写,对其他USB摄像头和其他USB设备在WINCE上的实现有一定的参考价值.     

Properties of tungsten-doped Bi4Ti3O12-SrBi4Ti4O15 intergrowth ferroelectrics

Ferroelectric and dielectric properties of tungsten-doped Bi₄Ti₃O₁₂-SrBi₄Ti₄O₁₅ ceramics were investigated. A pure phase of all the samples is confirmed by X-ray diffraction patterns. The remanent polarization (2P_r) of the samples increases initially and reaches its maximum value of 43.2 μC/cm² when W content is 0.03, which is over twice as large as that of non-doped one, then decreases with further doping. The coercive field (E_c) shows a weak tungsten content dependency. It is considered that the enlarged 2P_r could be mainly attributed to the restraint of oxygen vacancies as well as the weakening of their mobility. The Curie temperature decreases a little with increasing doping content, which indicates the good thermal stability is not deteriorated by tungsten doping.     

Effect of anionic surfactant on vaterite CaCO3

Calcium carbonate (CaCO₃) crystals with various shapes have been synthesized by aging calcium chloride and urea hybrid solution containing sodium dodecylsulfonate (SDSN) or sodium dodecylbenzenesulfonate (SDBS) in a 90 °C bath. The effects of SDSN and SDBS on the morphology and polymorph of precipitated CaCO₃ are investigated with the help of scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectrometer and X-ray diffraction (XRD). Flower-like vaterite changes from monolayer to multilayer structure with the increase of SDSN concentration. While the crystal shape changes from plate-like, through rose-shaped, hat-like, to bicone-like as the concentration of SDBS is increased.     

高灵敏度CMOS光电集成接收机设计

设计了一个由调节型级联跨阻抗放大器(TIA)和双光电二极管(DPD)构成的CMOS光电集成(OEIC)接收机.具体分析了这个光电集成接收机的噪声和灵敏度及其相互关系.接收机中的噪声主要是电路中电阻的热噪声和MOS器件的闪烁噪声.提出了优化接收机灵敏度的方法.通过低成本的CSMC 0.6μm CMOS工艺流片并对芯片进行了测试.从测试眼图可知,该CMOS光电集成接收机可工作在1.25GB/s的传输速率下,灵敏度为-12dBm.     

PMD补偿器和PMD补偿接收机的特性

以介绍ITU—TG．666建议主要内容的方式，讨论了有关PMD补偿器和PMD补偿接收机的特性。     

Synthesis and characterization of Ti-SBA-16 ordered mesoporous silica composite

Ti-SBA-16 mesoporous silica with a cubic Im3m structure has been successfully synthesized through prehydrolysis of a silica precursor in the presence of a tri-block copolymer F127 under acidic condition. X-ray diffraction (XRD) shows that the highly ordered mesostructure was maintained even at the high loading of titanium up to 5.5 (bulk molar ratio SiO₂/TiO₂). UV–vis and Raman spectroscopy reveal that the titanium species was highly dispersed in the silica framework with tetrahedral coordinate and octahedral coordinate, respectively. N₂-adsorption data exhibit that the BET surface, pore size and pore volume were maintained with an increase of titanium species loading for this cubic Im3m mesoporous composite. SEM image shows its amorphous morphology. The synthesis of mesoporous TiO₂-containing SBA-16 composite with a cubic Im3m structure will open new applications for catalysts.     

用C#.NET设计与实现三种数据库接口的统一模式

目前,在许多工程开发的过程中,都要和数据库相关联。例如:Oracle 9i,SQL Server 2000和Access 2003等。虽然每种数据库与Visual Studio.NET 2003中的C#连接方式多种多样,但也有很多相似之处,可以将相似的地方用统一方法写成实用的接口。这样可以很好地对C#Windows Forms程序和ASP.NET程序进行架构的组织,配合微软最近推出的ASP.NET 2.0版本的架构。可以将数据实体层(即数据库层)、业务逻辑层、界面表示层等进行分类。针对这3种数据库与C#.NET接口的相似性来写一种具有统一模式的接口。