下一代无线通信概念和技术

下一代无线通信(NextG:Next-generationwireless)的主流是随时随地的无线通信系统和无缝的高质量无线业务。概述了随时随地的无线通信和业务发展情况,并且介绍了为下一代无线通信的发展提供基础的关键技术。     

SCB火工品的研究与发展

文章评述了半导体桥火工品问世以来的研究成果与发展趋势。主要内容有半导体桥作用机理、半导体桥的结构与封装、半导体桥火工品的特点、半导体桥火工品的应用、半导体桥火工品的研究和发展趋势。     

石油沥青60℃动力粘度测定影响因素的探讨

粘度是表征沥青稠度的一个重要指标。通过论述石油沥青粘度测定法(真空毛细管法)中毛细管的选择、温度、真空度、取样量等对试验结果的影响及试验过程中的其它注意事项,表明了在测定石油沥青的60℃动力粘度时,必须严格按照试验方法的要求进行测定,以保证试验结果的准确性。     

固液分离水力旋流除砂器的数值模拟

利用CFD软件,采用雷诺应力模型分别计算了300型和250型水力旋流除砂器的内流场,得到了2种水力旋流除砂器的轴向、径向、切向速度及压强的分布曲线。通过对所得结果的分析,发现模拟结果基本符合旋流除砂器的运行规律。比较2种旋流除砂器的内流场,表明改进的300型水力旋流除砂器的结构及分离能力优于原来250型水力旋流除砂器,为水力旋流除砂器的优化设计和选型提供了可靠的设计依据。     

低温高速离心泵的研制与应用

阐述了适合于输送低温介质的高速离心泵的水力设计和结构设计方法，结构上采有长，中，短叶片相间的复合叶轮及双密封结构，理论上采用以效率为目标函数的优化水力设计方法，保证了低温高速离心泵具有很好的工人可靠性和优越的性能指标。     

双波长稳频CO_2激光模糊控制系统的建模与优化

报导一种模糊逻辑控制系统的建模与优化方法。以此方法设计的模糊逻辑控制器，用于双波长稳频ＣＯ２激光器的控制得到令人满意的结果。     

衍射法细丝直径的精密测量

分析了激光衍射法测量细丝直径技术中影响精度的几个主要因素，研究了一种微弱衍射条纹的精密处理及识别技术，有效地提高了测量精度，实测结果表明，文中讨论的技术能在１０￣５０μｍ的范围内实现正负０．１μｍ的重复精度，分辨力优于０．０１μｍ。     

GaN and AlGaN high-voltage rectifiers grown by metal-organic chemical-vapor deposition

In this paper, we report the study of the electrical characteristics of GaN and AlGaN vertical p-i-n junctions and Schottky rectifiers grown on both sapphire and SiC substrates by metal-organic chemical-vapor deposition. For GaN p-i-n rectifiers grown on SiC with a relatively thin “i” region of 2 μm, a breakdown voltage over 400 V, and forward voltage as low as 4.5 V at 100 A/cm² are exhibited for a 60-μm-diameter device. A GaN Schottky diode with a 2-μm-thick undoped layer exhibits a blocking voltage in excess of ∼230 V at a reverse-leakage current density below 1 mA/cm², and a forward-voltage drop of 3.5 V at a current density of 100 A/cm². It has been found that with the same device structure and process approach, the leakage current of a device grown on a SiC substrate is much lower than a device grown on a sapphire substrate. The use of Mg ion implantation for p-guard rings as planar-edge terminations in mesageometry GaN Schottky rectifiers has also been studied.     

Estimation of deformation gradient and strain from cine-PC velocity data

Phase contrast magnetic resonance imaging (MRI) can provide in vivo myocardial velocity field measurements. These data allow densely spaced material points to be tracked throughout the whole heart cycle using, for example, the Fourier tracking algorithm. To process the tracking results for myocardial deformation and strain quantification, we developed a method that is based on fitting the tracking results to an appropriate local deformation model. We further analyzed the accuracy and precision of the method and provided performance predictions for several local models. In order to validate the method and the theoretical performance analysis, we conducted controlled computer simulations and a phantom study. The results agreed well with expectations. Human heart data were also acquired and analyzed, and provided encouraging results. At the signal-to-noise ratio (SNR) level and spatial resolution expected in clinical settings, the study predicts strain quantification accuracy and precision that may allow the technique to become a practical and powerful noninvasive approach for the study of cardiac function, although clinically acceptable data acquisition strategies for three-dimensional (3-D) data are still a challenge.     

氧化铝陶瓷缺口件循环疲劳及断裂机理

用实验方法研究了Ａｌ＿２Ｏ＿３陶瓷缺口试件在循环载荷作用下的疲劳寿命。结果表明，缺口导致的应力集中效应显著降低了循环疲劳寿命；若用缺口根部最大应力为应力水平，则不同缺口半径陶瓷试件具有相同疲劳断裂规律，说明陶瓷材料的疲劳集中系数和理论应力集中系数相同。本文还分析讨论了陶瓷材料的循环疲劳寿命表达式和循环疲劳断裂机理。