贴片电阻表面缺陷自动识别方法

提出了一种基于非下采样Contourlet变换(NSCT)域图像去噪算法.首先根据尺度间与尺度内的NSCT系数之间的相关性,用非高斯分布模型对NSCT系数与其邻域系数及父系数进行建模,给出分类准则,把系数分为重要系数和非重要系数,再采用广义高斯分布来模拟重要系数的概率分布,根据贝叶斯理论得到自适应阈值,并求出最佳参量范围.为了克服软、硬阈值函数的缺点,提出一种自适应的新阈值函数,利用新阈值函数估计出不含噪音的变换系数,并通过非下采样Contourlet逆变换得到去噪后的图像.仿真实验表明,本文方法在峰值信噪比、结构相似性与视觉效果上均优于目前许多优秀的去噪算法.     

Preparation via the polymer route and photoluminescence properties of CeSi3N5

CeSi₃N₅ has been prepared via the polymer route, a one-pot and liquid-phase synthesis, based on a reaction between SiCl₄ and liquid NH₃ in which Ce[N(Si(CH₃)₃)₂]₃ was suspended. The sample was characterized by powder X-ray diffraction analysis, diffuse reflection and photoluminescence spectroscopies. CeSi₃N₅ exhibits a strong absorption peaking at 365 nm. Furthermore, it has a broad emission band at 468 nm due to 4f⁰5d¹ → 4f¹ transition of Ce³⁺. Obviously, CeSi₃N₅ appears to be a good candidate for use as a blue phosphor, which can be pumped by near-UV-LEDs.     

A hybrid heuristic for the maximum dispersion problem

In this paper we propose a hybrid heuristic for the Maximum Dispersion Problem of finding a balanced partition of a set of objects such that the shortest intra-part distance is maximized. In contrast to clustering problems, dispersion problems aim for a large spread of objects in the same group. They arise in many practical applications such as waste collection and the formation of study groups. The heuristic alternates between finding a balanced solution, and increasing the dispersion. Balancing is achieved by a combination of a minimum cost flow algorithm to find promising pairs of parts and a branch-and-bound algorithm that searches for an optimal balance, and the dispersion is increased by a local search followed by an ejection chain method for escaping local minima. We also propose new upper bounds for the problem. In computational experiments we show that the heuristic is able to find solutions significantly faster than previous approaches. Solutions are close to optimal and in many cases provably optimal.     

权重可变条件下员工绩效排名稳健性的Hasse图分析

绩效排名是绩效考核过程中关注度最高的环节,也是引发争议的“活火山”。因此,识别排名争议和控制排名风险是提升组织公平感和员工满意度的必要手段。以权重不确定性为切入点,应用偏序集理论重构绩效评价模型,获得员工绩效排名Hasse图,直观展示员工分层聚类及不稳健排序;并讨论Hasse图分层方法与性质。实例分析表明,利用偏序集构建的绩效评价模型有助于控制考核排名中的风险点,提升员工绩效考核质量。     

The interface effect on the lithiation of silicon/graphene composites: The first principles study

To reveal the interaction mechanism between lithium (Li) and silicon/graphene (Si/Gra) interface at the atomic scale, it was calculated that the energy band structure, density of states, charge transfer, radial distribution function and Li diffusion coefficient based on the first principles. The results indicated that the volume expansion of Si was effectively limited by the Si/Gra interface during Li insertion. There appeared the interface effect of Si/Gra on the combination of Li and Si atoms, according to the longer Li-C (2.9 Å) and the larger electron cloud near the Li atom at the Si/Gra interface. The better diffusion channel for Li atoms was constructed at the Si/Gra interface, due to the lower diffusion energy barrier (0.42–0.44 eV) and higher diffusion coefficient (D_Li = 0.784 × 10⁻⁴ cm²/s) for Li⁺ diffusion.     

微胶囊无卤阻燃剂的研究进展

介绍了作为微胶囊芯材的无卤阻燃剂——无机阻燃剂、膨胀阻燃剂、氮磷系阻燃剂的分类及优缺点。以微胶囊阻燃剂的包覆壳材料为重点,综述了阻燃剂的无机包覆、有机包覆、双层或多层包覆和反应生成阻燃剂型包覆的最新研究进展,最后介绍了界面聚合法、原位聚合法、溶胶-凝胶法和超临界法等四种制备微胶囊阻燃剂的方法,并展望了微胶囊阻燃剂的未来发展方向。     

金属离子Na+ , Li+ , Mg2+与硫酸根离子形成的无水缔合物种的从头算量子化学研究

计算并讨论了Na+, Li+和Mg2+ 3种离子与SO42-离子形成离子缔合物的结构以及阳离子的结合对ν1-SO42-频率的影响. 结果表明, 在缔合物结构方面, 阳离子数目越少, 离子间斥力越小, 越容易形成阳离子与硫酸根间距离更短, 结合更紧密的双齿缔合结构; 而当阳离子数目增加时, 特别是当具有2个正电荷的Mg2+离子数目较多时, 离子间的斥力使多离子团簇不稳定, 易形成阳离子与硫酸根间距离更长的单齿缔合结构. 有2种阳离子作用可影响ν1-SO42-频率, 一种是极化作用, 可使ν1-SO42-频率红移; 另一种是成键作用, 可使ν1-SO42-频率蓝移. 当金属离子数目≤2时, 阳离子的极化作用占主导地位, 第一个阳离子能使ν1-SO42-频率发生红移, 而当阳离子数目增多时, 不同方向结合的其它阳离子可以削弱第一个阳离子的极化作用, 因此导致多离子团簇中ν1-SO42-频率红移的减小. 当阳离子数目≥3时, 极化作用影响减小, 成键作用占据主导地位, 导致ν1-SO42-频率更大蓝移的单齿缔合结构取代双齿结构, 并使多离子团簇中的ν1-SO42-频率继续发生蓝移.     

基于复杂事件处理的WSID网络中间件的研究

射频识别(Radio Frequency Identification,简称RFID)与无线传感器网络(Wireless Sensor Network,简称WSN)融合形成的无线传感识别(Wireless Sensor Identification,简称WSID)网络,既可以识别物体携带标签的的信息,还可以检测物体周围环境的信息,将成为物联网的一个发展趋势;基于EPC体系架构提出一种WSID网络的体系架构,并详细介绍了此体系中间件的设计;运用复杂事件处理技术实时地处理来自分布式RFID读卡器和传感器的大量数据,WSID中间件通过筛选、分组、汇总和构建复杂事件,为用户提供更有意义的数据。     

矿用红外瓦斯检测仪的设计与实现

瓦斯浓度检测是煤矿生产中必不可少的环节,文中设计一种带无线发射模块的便携式红外瓦斯检测仪;该系统以AT-MEGA128控制器为核心,准确快速地实现了系统的功能,同时利用无线收发模块和上位机通信实现信息共享;文中主要介绍了部分硬件电路设计和软件实现,采用两路红外检测装置对瓦斯进行检测,有效滤除了外在红外光的干扰,将朗伯-比尔红外吸收定律和拉格朗日插值定理运用其中实现了对瓦斯浓度的精确检测;最终实验验证该瓦斯浓度检测仪具有检测精度高,检测范围广,高效节能等特点。