线性切换容错控制系统稳定性的新判据*

研究了线性切换容错控制系统的稳定性问题。利用分段李雅普诺夫函数方法,结合梅茨勒矩阵的性质和矩阵不等式的分析技巧,得到了基于李雅普诺夫—梅兹勒线性矩阵不等式判定系统稳定的新结果。设计依赖于状态的切换规则便于计算、易于检验。最后利用MATLAB工具箱得到的仿真实例验证了本结果的可行性。     

Rare earth effect on the microstructure and tribological properties of FeNiCr coatings

FeNiCr alloys with various amounts of La2O3 powders were thermally sprayed onto steel substrate. Electron probe microscopy analysis (EPMA), X-ray photoelectron spectroscopy (XPS), and an Optimol SRV oscillating friction and wear tester in a ball-on-disc contact con-figuration were employed to investigate the properties of the sprayed coatings. The results show that rare earth can refine the microstructure effectively and make the element distribution uniform, which leads to the improvement in the properties of the coatings. Meanwhile, the wear rate of the FeNiCr alloy with 1.5% La2O3 is smaller than those of the other coatings. Interestingly, the rare earth can reduce the friction coef-ficient and act as a self-lubricant in the oxide debris layer formed on the worn surface in friction. The wear mechanism of the coatings is oxi-dation wear, and a large amount of counterpart material is transferred to the coatings.     

铟锡锌软金属修复润滑剂对钢的自修复及其摩擦学特性

针对目前润滑自修复技术生成的修复层厚度较薄,难以修复较严重磨损表面的不足,研制了含铟、锡和锌三种软金属添加剂的新型磨损自修复润滑剂。在摩擦磨损试验机上,考察了使用该润滑剂的钢?钢面接触摩擦副的磨损自修复行为及其摩擦学性能。用X射线能谱(EDS)和扫描电镜(SEM)分析了修复表面的主要化学元素和自修复涂层的厚度。用淬冷试验测试了涂层与基体的结合强度。结果表明,研制的铟锡锌润滑脂能在钢表面摩擦形成约30μm厚度的自修复涂层,涂层与基体结合性能良好,修复后的钢表面有良好的减摩抗磨性能。     

Incorporation and metabolism of trans 20∶5 in endothelial cells. Effect on prostacyclin synthesis

To study the ability of long-chain trans fatty acids (FA) to be incorporated and metabolized into endothelial cells, bovine aortic endothelial cells were incubated with medium enriched eicosapentaenoic acid (EPA) bound to albumin (M2) or one of its geometrical isomers: 20∶5 5c,8c,11t,14c,17c(M3), 20∶5 5c,8c,11c,14c,17t(M4), or 20∶5 5c,8c,11t,14c,17t(M5). After 48 h of incubation, supernatant and cells were harvested and their lipids were analyzed, including prostacyclin synthesis. EPA and 22∶5n−3 of endothelial cells incubated with M2 were, respectively, three and two times higher than in control cells (incubated in M1, without any fatty acid added), whereas 22∶6n−3 increased only in the supernatant, suggesting its release after biosynthesis. However, 18∶2n−6 and 22∶4n−6 decreased (about 30%). Trans 20∶5 isomers represented 4.7, 3.9, and 5.2% of total phospholipid FA in endothelial cells incubated with M3, M4, and M5, respectively. They were elongated into trans 22∶5 and trans 24∶5, as revealed by gas chromatography-mass spectrometry and gas chromatography-Fourier transform infrared analysis. In cells incubated with M2, M3, M4, and M5, prostacyclin synthesis was inhibited by 49.0, 62.5, 60.5, and 72.0%, respectively. This effect may be due to less available arachidonic acid in the cells and to a competition between EPA isomers and AA at the level of cyclooxygenase pathway, as it was demonstrated that 20∶5 Δ17t was metabolized by this enzyme.     

Thermoelectric properties of Bi_（1.5）Pb_（0.5）Sr_（2-x）La_xCo_2O_y polycrystalline materials

Polycrystalline samples of Bi 1.5 Pb 0.5 Sr 2-x La x Co 2 O y (x = 0.1, 0.2, 0.3) with a layered structure were prepared by solid-state reaction method. All samples are p-type semiconductors. The thermoelectric properties, namely, the electric resistivity (ρ), Seebeck coefficient (S), and power factor (S 2 /ρ) of the samples are dependent on chemical composition. The values of ρ, S, and S 2 /ρ increase with an increase in temperature for all samples. The substitution of Pb 2+ for Bi 3+ and La 3+ for Sr 2+ improves the thermoelectric properties of the Bi 2 Sr 2 Co 2 O y system owing to the simultaneous decrease of electric resistivity and increase of Seebeck coefficient. As a result, the optimal thermoelectric property has been obtained in Bi 1.5 Pb 0.5 Sr 1.7 La 0.3 Co 2 O y and the power factor can reach 2.1 × 10-4 W·m-1 K-2 at 998 K.     

高能脉冲精密冷补技术用于修复零件表面局部缺损

高能脉冲精密冷补技术由于其独特的能量输出方式,在实现金属零件表面修复时具有修复速度快、热量输入小和结合强度高的特点。通过对液压柱塞杆划伤表面的实际修复和修复区域的性能测试,结果表明:修复层与基体无明显气孔,结合紧密,HAZ宽度为130μm,修复层平均显微硬度为520 HV,耐磨性能较基体提高36.4%。说明高能脉冲精密冷补技术是一种操作简单,性能可靠的新型修复技术。     

真实感人脸语音同步动画系统*

提出了一个人脸动画与语音同步的系统,重点解决协同发音、表现人脸细微表情特征的问题。输入带有情绪标志的文本,就能够产生对应表情的、与语音同步的人脸动画;本系统能够生成各种不同性别、年龄、表情特征的高度真实感3D人脸模型,人脸细微表情特征(如额头皱纹)可以随人脸表情的变化而动态改变。基于语言学理论,本系统提出了解决协同发音问题的一套规则。     

核函数的度量研究进展

核函数的度量(简称核度量)研究两个核函数(或一个核函数与另一个目标函数)之间相似性的度量方法,是核函数研究中的一个重要课题。系统综述了核度量的研究状况以及目前的研究进展,分析了典型核度量方法的特点及不足,并凝炼了其进一步研究的方向。     

Web服务攻击技术研究综述*

Web服务在给基于异构平台的应用集成带来极大便利的同时,其自身各核心组件也面临着恶意攻击的威胁。详细分析了针对单个Web服务以及Web服务组合过程的各种常见攻击技术的原理、特点,探讨了相应的检测和防御措施,结合已有研究成果,讨论了Web服务攻击防护将来的研究方向以及面临的挑战。     

通过流量和数据包综合估计内网感染蠕虫概率的研究*

提出了一种分析内网感染蠕虫可能性大小的方法。对通过内网交换机上的数据包使用蠕虫行为进行分析,得到行为异常的数据包数量,然后使用AR模型分析异常数据包的数量得到异常数据包的增长率;对内网异常流量和异常数据包增长率加权,并对它们综合估计得到内网中感染蠕虫概率的大小。实验表明该方法有效可行。