蓝宝石的应用及单晶强韧化研究进展

蓝宝石具有硬度大、强度高、抗腐蚀性强及良好的光学和化学特性,已被广泛应用于众多高科技领域,其突出的光学透过性有望成为新一代电子产品屏幕的盖板材料。然而蓝宝石单晶的冲击韧性差是本征缺陷,这将限制其在电子消费产品上的应用。近年来,国内外对蓝宝石的功能开发与应用,以及蓝宝石单晶强韧化进行了大量的研究。首先,对蓝宝石的相关性能进行了详细的介绍,综述了蓝宝石在光学、半导体、激光等领域的应用;其次,总结了蓝宝石通过掺杂合金元素、掺杂石墨粉、粒子注入以及铁、钛共掺杂等方法进行强韧化的研究进展,这些方法均可不同程度地提高蓝宝石单晶的断裂强度和断裂韧性;最后,对未来蓝宝石功能材料的应用以及蓝宝石强韧化工作的发展趋势进行了分析和探讨。     

螺旋流混合器内部流动及换热分析

构建了一种无运动部件的螺旋流混合器三维模型,运用计算流体力学理论,采用湍流、非定常和传热模型,模拟了冷、热水在混合器中螺旋混合的过程,并通过对混合器内流线和温度分布等的分析,探讨了混合器内部流动和能量交换的规律,以及进口流速和混合器容积的变化对其出口温度的影响。计算结果表明:螺旋流混合器可以得到了比较好的混合效果;在一定的阻力下,进口速度越大越易形成旋流,混合效果越好;螺旋流混合器的容积变化对混合效果影响明显,随着容积的增大,调整时间显著增加。     

Thermal anomalies associated with faults: a case study of the Jinhua–Quzhou basin of Zhejiang Province,China

Faults provide the path for geothermal natural convection and partially influence the ground surface thermal environment. The land surface temperatures (LSTs) near a fault are higher than in other areas and can indicate the strike trend of an underground fault. However, these anomalies of higher LSTs are not located accurately in the fault centre but near it with some offset, and these LST data may include other thermal information that needs to be eliminated prior to analysis. In this study, LSTs were retrieved from Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) thermal infrared (TIR) images and enhanced with land cover classification and elimination. The spatial patterns of the enhanced images were compared with geophysical prospecting tectonic profiles and with regional geological tectonic maps, revealing the spatial correspondence between the thermal anomalies and the faults. The results indicated that the thermal anomalies are located near the faults and are consistent with the faults' dip planes.     

基于GASA算法和调频函数的NLFM波形设计

与线性调频信号相比,非线性调频信号无需加权就可以获得很低的距离旁瓣,而且没有信噪比损失,在脉压雷达中得到广泛的应用。一般地,设计非线性调频信号都采用基于相位逗留原理的窗函数法,但是设计的波形有很高的距离旁瓣。在分析了窗函数法设计非线性调频信号的基础上,根据一种新的调频函数数学模型,提出了一种用GASA算法来产生非线性调频信号的新方法,并给出了仿真实例,仿真验证了该算法的有效性。通过该方法获得了脉压后低副瓣的非线性调频信号,可以提高脉冲压缩性能。     

Novel capacitive sensor: Fabrication from carbon nanotube arrays and sensing property characterization

A sandwich-structured gas sensor based on vertically aligned carbon nanotube (CNT) arrays was fabricated and investigated for ammonia and formic acid sensing. Vertically aligned CNT arrays were synthesized by acetone pyrolysis in anodized aluminum oxide (AAO) templates without the use of catalysts. The capacitance change of the sensor with target gas exposure was used as the sensing parameter. The sensor had relatively short response and recovery time. It was completely recovered within 6 min, without requiring any external stimuli. The possible mechanism of the responses was also discussed.     

MIMO blind equalization algorithm based on successive interference cancellation

Modified Constant Modulus Algorithm (MCMA) is widely used in the SISO blind equalization for its simplicity. For MIMO systems MCMA can only equalize one of the source signals. Through the combination of channel estimation and successive interference cancellation, source signals can be equalized in turn. However the recovery of the first source and the channel estimation are the key points, which directly affects the recovery of the subsequent sources. This paper proposes a channel estimation method with a small amount of calculation, and can accurately estimate the channel vector. Meanwhile, a new blind equalization algorithm is put forward to reliably recovery the first source signal. Simulation results verify the effectiveness of the proposed algorithm.     

重复荷载作用下支盘桩受力特性模型试验研究

对一个双盘模型支盘桩在非饱和粉土中进行了5次循环加载-卸载试验。试验证明:支盘桩在小于其极限承载力约0.75倍的重复荷载作用下变形增加很小,工作性能十分稳定;支盘桩与普通等直径桩相比,其承载力和抗变形能力十分优越;支盘桩的荷载传递机理十分复杂,盘附近土体对桩周的摩擦阻力在不同荷载作用下有时为正有时为负;当两盘的间距小于2D(D为盘直径)时,桩周的摩擦力对桩的承载力贡献很小,在每次重复荷载作用下,盘间土体都会经历加压和卸压的过程,卸载后土体会建立新的平衡和物理性质工作状态。研究表明,支盘桩应用于桥梁等承受重复荷载的结构是可行的。     

谐波对矿山电网的影响

对谐波做了简要的数学分析，重点论述了谐波对矿山电网和变压器、旋转电机、计算机或其他电子器件的有害影响     

Development of sensors based on CuO-doped SnO2 hollow spheres for ppb level H2S gas sensing

An effort has been made to develop a new kind of SnO₂–CuO gas sensor which could detect an extremely small amount of H₂S gas at relatively low working temperature. The sensor nanomaterials were prepared from SnO₂ hollow spheres (synthesized by employing carbon microspheres as temples) and Cu precursor by dipping method. The composition and structural characteristics of the as-prepared CuO-doped SnO₂ hollow spheres were studied by X-ray photoelectron spectroscopy, X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy. Gas-sensing properties of CuO-doped SnO₂ hollow sphere were also investigated. It was found that the sensor showed good selectivity and high sensitivity to H₂S gas. A ppb level detection limit was obtained with the sensor at the relatively low temperature of 35 °C. Such good performances are probably attributed to the hollow sphere nanostructures. Our results imply that materials with hollow sphere nanostructures are promising candidates for high-performance gas sensors.     

陈述式基于方程仿真模型的约简

为解决复杂多领域连续系统的高效仿真问题,研究了陈述式基于方程仿真模型的约简策略.基于符号处理技术,提出了一种模型约简方法.该方法从方程的规范转换入手,通过消除特定形式方程缩减系统规模,将整个方程系统规划分解为一个可顺序求解的子系统序列.给出的实例表明文中约简方法效果显著.文中策略与算法已在多领域物理系统混合建模与仿真平台EMWorks中实现.