An evaluation of commercial nickel catalysts during hydrogenation of soybean oil

The activities of several commercial nickel catalysts were determined by measuring their activation energies. Among these catalysts, G95E, Resan 22, Nysosel 222 and 325, all with low activation energy, were more active than DM3 and G95H, which had higher activation energy. However, the less active catalysts increased the linoleate selectivity of soybean oil during hydrogenation. The yields of bothtrans isomers and winterized oil were higher for the more selectively hydrogenated oil catalyzed by the less active catalysts. In the sensory evaluation, the fractionated solid fat that contained moretrans isomers was lower in flavor scores than the fractionated liquid oil after hydrogenation and winterization of soybean oil.     

基于顺序统计滤波的实时语音端点检测算法

针对嵌入式语音识别系统,提出了一种高效的实时语音端点检测算法. 算法以子带频谱熵为语音/噪声的区分特征, 首先将每帧语音的频谱划分成若干个子带, 计算出每个子带的频谱熵, 然后把相继若干帧的子带频谱熵经过一组顺序统计滤波器获得每帧的频谱熵, 根据频谱熵的值对输入的语音进行分类. 实验结果表明, 该算法能够有效地区分语音和噪声, 可以显著地提高语音识别系统的性能. 在不同的噪声环境和信噪比条件下具有鲁棒性. 此外, 本文提出的算法计算代价小, 简单易实现, 适合实时嵌入式语音识别系统的应用.     

基于EMD和BP神经网络的雷达体征信号检测算法

随着城市生活中医疗、治安、反恐等方面的需求日益突出,非接触式雷达生命体征检测逐渐得到各方面的关注.文章提出一种基于EMD和神经网络的雷达生命体征信号检测算法.由于UWB雷达回波信号的非平稳非线性特性,利用EMD的空间时间尺度特性对信号进行分解,得到一系列的本征模态函数IMF,然后通过结合了免疫遗传算法IGA的BP神经网络对信号进行优化,获得心跳和呼吸信号.结果表明,文章提出的算法比直接用EMD分解重构的信号的准确性高,弥补了EMD分解的端点效应问题,具有广阔的应用前景和研究价值.     

基于静态贝叶斯博弈的蠕虫攻防策略绩效评估

现有蠕虫攻击策略(防护策略)评估方法没有考虑防护策略(攻击策略)变化对攻击策略(防护策略)绩效评估的影响,且防护策略评估忽视了策略实施成本.针对这种情况,构建了基于静态贝叶斯博弈的绩效评估模型(performance evaluation model based on static Bayesian game,简称PEM-SBG)以及对抗情形下的蠕虫攻防策略绩效评估方法.在模型PEM-SBG基础上提出的基于灰色多属性理论的防护策略绩效评估方法,综合考虑了成本类和收益类的多个评估属性,有助于提高评估过程的全面性.针对典型的蠕虫攻防场景.利用仿真工具SSFNet进行了模拟实验,验证了所提出的模型和方法的有效性.     

Ultradrawing and crystallization of isotactic polystyrene and blends with atactic polystyrene

Pure isotactic polystyrene (iPS, M_w = 8.89 × 10⁴, M_w/M_n = 4.89) and its blends with an atactic polystyrene (aPS, M_w = 3.9 × 10⁵, M_w/M_n < 1.13) were subjected to draw by solid state coextrusion at 127°C within polyethylene. The content of amorphous iPS in these blends was varied from 100 to 24.4 wt %. The extent of draw-induced crystallization was found to depend on the draw ratio and on iPS concentration. The blend with 24.4% iPS was coextruded in two stages. The highest effective draw ratio (EDR) was 7.6 and 13.7 for one- and two-stage draw, respectively. The highest crystallinity of 33.2% was obtained for pure iPS at the maximum EDR of 7.6. Considerable crystallinity was induced in blends, requiring successively higher draw ratio to reach similar crystallinity with increased aPS content. The tensile modulus increased from 1.5 to 3.2 GPa, independent of iPS concentration. Thermal shrinkage results indicate that the elastic recovery of draw in the blends is near quantitative for an EDR < 8. For pure iPS, extrudate elastic recovery was dramatically altered by the draw-induced crystallinity.     

基于VRF和RT实现BGP／MPLS VPNs中的VPN拓扑发现

在RFC 2547中定义的BGP／MPLS VPNs允许服务提供者使用他们的IP骨干提供VPN服务，使用BGP对骨干网络的路由器分发VPN路由信息，使用MPLS转发VPN流量。BGP／MPLS VPNs允许服务提供者在VPN内定义拥有任意数量结点的任意拓扑。服务提供者能建立使用相同核心网络的多个VPN。目前大多数服务提供者手工地或通过使用配置的数据库实现BGP／MPLS VPNs。本文描述的算法使VPN拓扑发现过程自动化。使用该算法，服务提供者能使用当前网络配置信息自动地发现VPN拓扑。     

Robust control oriented identification of errors-in-variables models based on normalised coprime factors

A robust control oriented identification approach is proposed to deal with the identification of errors-in-variables models (EIVMs), which are corrupted with input and output noises. Based on normalised coprime factor model (NCFM) representations, a frequency-domain perturbed NCFM for an EIVM is derived according to a geometrical explanation for the v-gap metric. As a result, identification of the EIVM is converted into that of the NCFM. Besides an identified nominal NCFM, its worst case error has to be quantified. Unlike other traditional control-oriented identification methods, the v-gap metric is employed to measure the uncertainties including a priori information on the disturbing noises and the worst case error for the resulting nominal NCFM. Since this metric is also used as an optimisation criterion, the associate parameter estimation problem can be effectively solved by linear matrix inequalities. Finally, a numerical simulation shows the effectiveness of the proposed method.     

Vibration fracture resistance of 5052H112 aluminum alloy processed by cold rolling and friction stirring

Hot-rolled Al–3Mg alloy processed by various cold-rolled reductions exhibited excellent vibration fracture resistance, however subsequent friction stirring did not endow better vibration fracture resistance than cold-rolled samples in spite of possessing microstructural refinement and homogenization. The D–N curve under a constant initial deflection amplitude (6.5 mm) also showed that the vibration fracture resistance of cold-rolled specimens increased as a result of the slower crack propagation rate. All samples used in this investigation showed a work hardening feature from the initial stage of the D–N curve, and the deflection amplitude tended to increase as the number of vibration cycles increased. During this ascending stage, slip band cracking and strain hardening in the vicinity of the main crack could be recognized. The D–N curve feature of the cold-rolled samples depicted a longer plateau region while the deflection amplitude was at its maximum. It is suggested that the dislocation tangles introduced by cold rolling can strengthen the matrix. As a result, the deflection amplitude drops could be associated with increasing the dislocation tangles due to prior cold rolling while the main crack achieved a critical crack length.     

基于DSP平台的人民币编号识别系统的设计与实现

为了在嵌入式系统中实现实时视频图像人民币号码识别,提出了基于TI系列TMS320DM642的快速人脸检测系统设计方案,包括系统软件和硬件的方案。首先,详细介绍了人民币编号图像提取与识别,针对该算法实现原理阐述硬件平台上的算法移植和优化方案,最后,实现了嵌入式快速人民币号码识别系统的研制。通过分析测试结果,系统可靠运行,优化后系统运行速度提高,能够实现实时人民币号码识别。     

Vibration fracture behavior of Sn–9Zn–<Emphasis Type="Italic">x</Emphasis>Cu lead-free solders

The effect of Cu content on the microstructure and the vibration deformation mechanisms of a potential lead-free solder, Sn–9Zn–xCu (x = 0.2, 0.5, 0.7, 1.0 wt.%), are examined in this study. Results show that Zn-rich phase and Sn–Zn eutectic decreased, while Cu–Zn intermetallic compound and proeutectic Sn-rich phase increased with increasing the Cu content. For the specimens with high Cu content (0.7Cu and 1.0Cu), hard massive Cu₅Zn₈ existed mostly amongst the proeutectic Sn-rich phase dendrites, and Zn-rich dispersed unevenly, leading to the deterioration in the tensile strength and ductility. Under a constant vibration force and constant initial-deflection testing, the high Cu specimen with a higher damping capacity was able to absorb more vibration energy and thus possessed a greater vibration fracture resistance. In addition, the lamellar-deformed structures (LDS) and Cu₅Zn₈ were able to increase the crack tortuosity, which in turn increased the crack propagation resistance.