空分设备氮水预冷系统改进

分析 6 0 0 0m3 /h空分设备原氮水预冷系统存在的问题及原因 ,将水循环由原制氧站大循环改为氮水预冷系统内部的自循环 ,只增加水换热器和蓄水器 ,效果明显。     

A novel compact low-power direct conversion receiver for mobile UHF RFID reader

A novel direct conversion receiver with low cost and low power is implemented in a 0.18 μm 1P6M standard CMOS process for a Mobile UHF RFID reader.A highly linear active mixer with low flicker noise and low noise active load is proposed.An efficient and low cost on-chip DC offset voltage canceling scheme is adopted with a high-input-impedance four-input OPAMP to buffer the output of the DC offset canceller(DCOC) block.The receiver has a measured input 1 dB compression point of 2 dBm and a sensitivity of 72 dBm in the presence of the large leakage signal from the transmitter.Only occupying a silicon area of 2.5 mm 2 and consuming 21 mA from a 1.8 V supply,the receiver makes the mobile UHF RFID reader to communicate with a transponder in a distance of 1 m conveniently.     

基于遥感变化检测的石漠化信息自动提取

滇黔桂地区被划定为限制开发区后,石漠化的研究变得越来越热,而信息提取是这些研究的重要内容。当前石漠化信息提取主要依据静态指标进行,鉴于静态方法的不足,在动态机理剖析的基础上,综合考虑石漠化的静态景观及其动态属性,以贵州和云南交界区域为实验区,1992年和2001年两个时相的TM/ETM+影像为数据源,研究遥感变化检测方法在石漠化信息自动提取中的应用。在几何校正和辐射校正的基础上对两个时相的影像实施差值变化检测,将实验区分为变化区和无变化区两类,根据石漠化机理进一步将变化区分为石漠化区和逆石漠化区,完成石漠化信息识别,经验证Kappa系数为0.854。结果表明:遥感变化检测方法对石漠化有较好的识别效率和精度,能够为石漠化的综合防治提供科学依据。     

Isothermal transformation and decomposition ofβ 1 phase in a CuZnAl alloy

In the present paper, the crystallography of isothermal transformation and decomposition ofβ, phase have been studied by means of transmission electron microscopy and diffraction in the CuZnAl shape memory alloy. It has been proved that the bainite formed inβ ₁, matrix when the samples were transformed isothermally at moderate temperature. The crystallography of the isothermal bainitic transformation is identical to that of martensite in the same system. When the specimens were aged at moderate temperatures for longer time, the bainite and matrix decomposed to equilibrium phases. The decomposition process can be summarized as follows: $$\begin{gathered} bainite (9R) \to 9R + \alpha \left( {fcc} \right) \to \alpha + \beta \left( {bcc} \right) \hfill \\ matrix (B2) \to 2H + B2 \to \beta \left( {bcc} \right) \hfill \\ \end{gathered} $$ There are definite orientation relationships among these phases during the decomposition process and they are shown below: $$\begin{gathered} \left( {111} \right)_\alpha \parallel \left( {001} \right)_B ,\left[ {0\bar 11} \right]_\alpha \parallel \left[ {\bar 110} \right]_B \hfill \\ \left( {111} \right)_\alpha 5^ \circ away from \left( {110} \right)_\beta ,\left[ {0\bar 11} \right]_\alpha \parallel \left[ {1\bar 1\bar 1} \right]_\beta \hfill \\ \left( {110} \right)_M \parallel \left( {001} \right)_{2H} ,\left[ {001} \right]_M \parallel \left[ {010} \right]_{2H} \hfill \\ \end{gathered} $$ Thus, the crystallography of isothermal transformation and decomposition ofβ ₁ phase and the sequence of transitions have been revealed.     

基于PCI和FPGA的信号源设计

信号源是航天遥测试验的核心部件,它作为地面设备提供实验过程中所需的各种参数;本信号源采用模块化设计方法,将PCI技术和FPGA技术进行有机结合,对信号源进行了系统方案设计、系统硬件设计和系统软件设计等工作,通过控制FPGA内部ROM的读写、高精度D/A转换器AD9744的转换和多路选择开关ADG1208的选通,产生多路参数可控模拟信号输出;测试结果满足设计要求,已经成功应用于某地面测试设备的自检和检测中。     

基于机器人运动模型的EKF-SLAM算法改进

针对两轮驱动机器人运动模型定向误差的累积问题,提出改进的三轮驱动机器人运动模型,对EKF-SLAM算法的一致性进行改进;该模型通过对机器人车轮线速度的解耦运算,将机器人运动过程中的旋转角速度提取出来并作为系统的控制输入之一,从而可以直接得到各个控制时间间隔内的机器人姿态角变化,很好地避免了机器人定向误差的累积;最后,基于归一化估计方差的检验标准进行实验,验证了三轮驱动机器人运动模型有效提高了EKF-SLAM算法的一致性。     

高校信息化校园建设的几点思考

教育信息化是我国信息化建设的重要组成部分,推进教育行业的信息化已是大势所趋。如何合理、高效地进行信息化校园建设是目前校园信息化建设过程中迫切需要解决的问题。作者多年来积极参与学校的信息化建设,对信息化校园建设深入的进行了思考,提出了信息化校园建设内容、建设过程中存在的困难与顾虑及建设思路。     

An intrinsic semantic framework for recognizing image objects

The paper proposes a new approach to find semantic meanings in visual object class structure, in line with the Gestalt laws of proximity. Micro level semantic structures are formed by line segments (arcs also approximated into line segments based on pixel deviation threshold) which are in close proximity. These structures are hierarchically combined till a semantic label can be assigned. The algorithm extracts semantic groups, their inter-relations and represents these using a graph. Invariant geometrical properties of the groups and relations are used as vertex and edge labels. A graph model captures the inter class variability by analyzing the repetitiveness of structures and relations and uses it as a weighting factor for classification. The algorithm has been tested on a standard benchmark database and compared with existing approaches.