Thermal Expansion of Solid Solutions in the ZrTiO4—In2O3—M2O5 (M = Sb, Ta) System

Axial and dilatometric thermal expansions and phase transformations were studied for solid solutions having the α-PbO₂ structure in the ZrTiO₄—In₂O₃—M₂O₅ (M = Sb, Ta) system with nominal formulas of Zr _x Ti _y In _z Sb _z O₄ and Zr _x Ti _y In _z Ta _z O₄ where x + y + 2 z = 2. With increased substitution of z , the cell volume increased, the difference in the b parameters at room temperature between those quenched from 1400° and 1000°C decreased, and the thermal expansion decreased. The axial thermal expansion of ZrTi _y In _z · Ta _z O₄ with z = 0.3 was almost identical with that of HfTiO₄, and those with z = 0.4 and z = 0.45 were smaller than that of HfTiO₄. Unit-cell volumes of these compound were compared with those of single oxides to make it clear that the unit-cell volume of ZrTiO₄ was small anomalously and to distinguish the normal and abnormal substitution systems. These results were explained by the working hypothesis proposed for these compounds.     

板壳式换热器设置膨胀节的判定

介绍板壳式换热器的主要特点和应用。当壳体与板束温差较大时,笔者通过对产品开发的生产实践,提出解决板壳式换热器要否设置膨胀节的类似判定方法。     

无定位图的预测误差差值扩展可逆数据隐藏*

将Tian差值扩展技术应用于彩色图像中,提出一种利用预测误差差值进行扩展嵌入的彩色图像可逆数据隐藏算法。针对传统差值扩展技术存在过分修改像素灰度值、须嵌入定位图等缺点,首先利用色彩分量间的相关性减小差值,并将差值扩展量分散到两个色彩分量中;其次,对直方图平移技术进行改进,使得同等嵌入率下图像质量达到最佳;最后由两个色彩分量中像素的预测值之和决定可用于扩展嵌入的像素,无须保存溢出定位图,提取端在提取信息时可无损地恢复原始图像。实验结果表明,与其他算法相比,该算法在同等嵌入率下可取得更好的图像质量,算法复杂度     

管板和传热管胀接应力应变的数值模拟及分析

蒸汽发生器是核电厂一回路与二回路的枢纽,传热管和管板的连接处为事故多发区,而机械加工过程残留的应力是引起裂纹的主要原因.应用有限元软件对某型蒸汽发生器中的传热管和管板的胀接过程进行瞬态模拟,得到不同胀接压力下的管板和传热管的残余应力和残余应变值,为传热管和管板最佳胀接参数的确定以及工作过程中应力腐蚀的预防提供理论依据.研究结果标明,管板孔表面的残余径向应力和残余径向应变值都是随胀接压力的增加而增加,且沿着轴向的变化规律相似.     

基于嵌入式多串口扩展的出租车智能导航终端设计与实现

目前,ARM处理器在嵌入式系统中得到了广泛的应用,但其通常只有3个及以下的串口,难以满足需要多串口设备的系统需求;分析研究基于ARM处理器的智能车载导航终端的多串口扩展问题,提出采用具有单串口扩展为5串口功能的串口扩展芯片GM8125,实现嵌入式系统的多串口扩展需求,并在串口通信中采用分层设计的方法,提高系统的稳定性和运行效率;该出租车智能移动导航终端系统经过实际调试与运行,能够实现预定功能且效果良好,能够应用到新型的智能交通调度系统中。     

Performance analysis for range expansion in heterogeneous networks

In this paper, the uplink and downlink performance of a two-tier heterogeneous network （HetNet） with range expansion （RE） is analyzed. Different from previous works, base stations （BSs） are modeled as a spatial Poisson point process. This model can not only capture the irregularity of the BS deployment but also lead to closed form expressions. With the analytical results, the impacts of several key parameters on the coverage and throughput performance are investigated. Our results justifies the effectiveness of RE and Pico deployment. Based on our analyses, certain attention should be made on the RE design to balance the uplink and downlink performance. Our analyses are corroborated by simulations and can thus serve as a flexible and quick guidance for system design without complicated and time-consuming system-level platform construction and simulation.     

Thermal expansion of an SiC particle-reinforced aluminum composite

Using a push-rod dilatometer, we measured between 76 and 390 K the thermal expansion of a particle-reinforced-composite wrought plate obtained by powdermetallurgy methods. The particles, 30% by volume, consisted of monocrystals of -SiC with sizes near 10 m. The matrix consisted of a 6061 aluminum alloy with original particle sizes near 20 m. We found the perpendicular thermal expansivity, ₃, higher by 26% than the in-plane thermal expansivity, ₁-₂. These values differ from a rule-of-mixture prediction by –3 and –23%, respectively. All three _i, components lie outside the Rosen-Hashin bounds. Levin's isotropic model agrees within 10% with the ₁-₂-₃ average. Both the anisotropy and the bounds violation result from microstructural nonhomogeneity arising from processing. Rosen and Hashin's transverse-isotropicsymmetry relationships account approximately for these effects by introducing the anisotropic elastic constants. Using neutron diffraction, we determined that the SiC particles are textureless.Paper presented at the Tenth International Thermal Expansion Symposium, June 6–7, 1989, Boulder, Colorado, U.S.A.     

基于2030可持续发展目标的珠三角土地消耗率与人口增长率协调关系评价

量化联合国可持续发展目标SDG 11.3.1“土地消耗率与人口增长率的比率（LCRPGR）”有助于了解城市扩张与人口增长之间的关系,为城市国土空间规划和人口城镇化调控提供数据支撑,并且对指导决策者制定城市增长计划至关重要。基于土地利用产品、夜间灯光数据和人口普查数据,提取了城市建成区,利用地理加权回归模型测算了珠三角地区1 km×1 km格网尺度人口密度。依据SDG 11.3.1指标元数据中定义和公式,对珠三角地区可持续发展进行了可靠评价。结果显示：①1990~2010年珠三角建成区面积扩张4.6倍,城区人口增长3.7倍;②1990~2010年珠三角的LCRPGR值由0.71增长到2.01;城市扩张速度与人口增长速度并非是成比例协调增长关系;③建成区的扩张主要是由耕地和农村居民用地转换而来。综上,自2000年后珠三角地区土地消耗率已经超过人口增长率,城市扩张速度与人口增长速度并非是成比例协调增长关系,二者的差异在增大,应当引起一定注意。     

多孔薄壁扁管连续挤压模的研制

介绍了连续挤压模的生产工艺过程 ,模具主要结构及设计参数 ,分析了生产中存在的问题以及采取的措施 ,充分发挥了连续挤压设备的潜力 ,扩大了产品品种