The role of C–H⋯O hydrogen-bonding interactions in the solid-state packing of squaraine dyes

The role of C–H⋯O hydrogen-bonding interactions in the solid-state packing networks of squaraine dyes has been investigated by re-examining the nine previously published X-ray crystal structures of these materials. In addition, two new compounds, 2,4-bis(1-hexyl-3,3-dimethyl-2-indolinylidenemethyl)cyclobutenebis(ylium)-1,3-diolate and 2,4-bis(1-(ethan-2-ol)-3,3-dimethyl-2-indolinylidenemethyl)cyclobutenebis(ylium)-1,3-diolate, have had their structures determined and lattice packings discussed with respect to their hydrogen-bonding networks. Analysis of the eleven structures shows, in seven cases, two emergent packing motifs. All structures exhibit molecules in stacked columns, but the two differing patterns arise from specific intermolecular C–H⋯O associations which are directed at the molecules of either an adjacent parallel column or a column of opposing direction. In the four structures which do not exhibit either of these two packing arrangements, hydrogen-bonding associations are still important in the analysis of the overall lattice network.     

非线性切换系统的异步事件驱动控制

事件驱动控制是一种减少通讯总量并能保持闭环系统性能的有效控制策略.在事件驱动控制中,由于取样时刻与切换时刻之间的异步会导致子系统与控制器之间的异步切换,造成切换系统的不稳定.因此,考虑非线性切换系统的异步事件驱动控制问题显得尤为重要.为了解决这一问题,首先从结构简单的线性部分和非线性部分级联的非线性切换系统入手,基于该...     

An analytic model for high-electron-mobility transistors

A new analytic model is developed for the output I–V characteristics and microwave-signal parameters of High Electron Mobility Transistors (HEMTs). In this model, the empirical formula suggested by Giblin et al. is used to approach the behavior of electron drift velocity vs electric field. The resulting I–V curves are in excellent agreement with experimental data. In order to predict the microwave performance of these devices, this model is also used to calculate the small-signal parameters, transconductance and gate capacitance, which are then used to estimate f_T, the frequency of unity current gain.     

药芯焊丝明弧堆焊Fe-Cr-C-B合金组织及耐磨性

为了提高堆焊合金的耐磨性,利用明弧堆焊方法将自保护耐磨堆焊药芯焊丝熔覆在Q235基体金属表面,制备得到Fe-Cr-C-B耐磨堆焊合金.采用金相显微镜、扫描电子显微镜、X射线衍射仪、硬度计和磨料磨损试验机对堆焊层的组织、硬度和耐磨性进行了分析.结果表明,堆焊层主要由马氏体、少量残余奥氏体、M₃(C,B)、M₂₃(C,B)6和M₇(C,B)3相组成.随着B质量分数的增大,基体组织转变为马氏体,共晶硬质相增多,并呈连续网状分布在基体组织周围.当B的质量分数为3%时,堆焊层的耐磨性达到最佳,其硬度为61. 5 HRC,磨损量为0. 362 9 g.     

New Fe-based soft magnetic amorphous alloys with high saturation magnetization and good corrosion resistance for dust core application

Fe-rich amorphous dust core alloys with minor-addition of Mo and/or Cr were synthesized because of the industrial request of mass production of high efficient low core loss Fe-based dust cores. It was found that the present Fe-(Cr, Mo)-P-B-Si-(C) amorphous alloy ribbons exhibit good soft magnetic properties of above 1.5 T for saturation magnetization, below 10 A/m for coercivity and rather good corrosion resistance in 3%NaCl aqueous solution. Besides, the amorphous alloy ribbons exhibit good bending ductility in as-spun and optimally annealed states. It is noticed that these characteristics are much superior to those for commercial Fe-Cr-Nb-P-B-Si soft magnetic dust core alloy (SENNTIX). In addition, the annealing treatment was noticed to cause the improvement of corrosion resistance without detriment to bending ductility. The new Fe-based soft magnetic alloys with good combined characteristics are expected to be used as the basic material as high-efficient soft magnetic dust cores in a high frequency range.     

基于OpenGL的工业机器人分拣系统仿真

针对工业机器人视觉分拣工件问题,开发了一套工业机器人分拣仿真系统。该系统主要包括工件的识别与定位算法和机器人分拣的动态仿真,是基于VC++6.0开发平台和OpenGL图形库而开发的。工件识别是依赖于角点检测实现的。本文在确定工件表面中心和长轴的基础上,基于几何原理提出了一种新的机器人运动学反解方法,并验证了运动学分析的正确性,且直观地实现了机器人分拣工件的动态仿真。仿真结果表明,该系统能够快速、准确分拣工件,满足实际工程的要求。