Dynamic output feedback control of a flexible air-breathing hypersonic vehicle via T–S fuzzy approach

By utilising Takagi–Sugeno (T–S) fuzzy set approach, this paper addresses the robust H_∞ dynamic output feedback control for the non-linear longitudinal model of flexible air-breathing hypersonic vehicles (FAHVs). The flight control of FAHVs is highly challenging due to the unique dynamic characteristics, and the intricate couplings between the engine and fight dynamics and external disturbance. Because of the dynamics’ enormous complexity, currently, only the longitudinal dynamics models of FAHVs have been used for controller design. In this work, T–S fuzzy modelling technique is utilised to approach the non-linear dynamics of FAHVs, then a fuzzy model is developed for the output tracking problem of FAHVs. The fuzzy model contains parameter uncertainties and disturbance, which can approach the non-linear dynamics of FAHVs more exactly. The flexible models of FAHVs are difficult to measure because of the complex dynamics and the strong couplings, thus a full-order dynamic output feedback controller is designed for the fuzzy model. A robust H_∞ controller is designed for the obtained closed-loop system. By utilising the Lyapunov functional approach, sufficient solvability conditions for such controllers are established in terms of linear matrix inequalities. Finally, the effectiveness of the proposed T–S fuzzy dynamic output feedback control method is demonstrated by numerical simulations.     

An alignment-free fingerprint bio-cryptosystem based on modified Voronoi neighbor structures

Bio-cryptography is an emerging security technology which combines cryptography with biometrics. A good bio-cryptosystem is required to protect the privacy of the relevant biometric data as well as achieving high recognition accuracy. Fingerprints have been widely used in bio-cryptosystem design. However, fingerprint uncertainty caused by distortion and rotation during the image capturing process makes it difficult to achieve a high recognition rate in most bio-cryptographic systems. Moreover, most existing bio-cryptosystems rely on the accurate detection of singular points for fingerprint image pre-alignment, which is very hard to achieve, and the image rotation transformation during the alignment process can cause significant singular point deviation and minutiae changes. In this paper, by taking full advantage of local Voronoi neighbor structures (VNSs), e.g. local structural stability and distortion insensitivity, we propose an alignment-free bio-cryptosystem based on fixed-length bit-string representations extracted from modified VNSs, which are rotation- and translation-invariant and distortion robust. The proposed alignment-free bio-cryptosystem is able to provide strong security while achieving good recognition performance. Experimental results in comparison with most existing alignment-free bio-cryptosystems using the publicly-available databases show the validity of the proposed scheme.     

Dynamic response of Ti3SiC2 under shock compression up to 112 GPa

Ti₃SiC₂ is of interest due to its unique dual nature reminiscent of both brittle ceramics and ductile metals at ambient conditions. In this work, plate-impact experiments have been performed to study the dynamic behavior of Ti₃SiC₂ under shock compression up to 112 GPa by using laser velocity interferometer and electric pin techniques. Hugoniot elastic limits (HEL), spall strength, and Hugoniot equations of state have been obtained based on measured particle velocity profiles and shock wave velocities. The ratio of spall strength to HEL for Ti₃SiC₂ is larger than brittle ceramics but smaller than metals. This result indicates that the dual nature of Ti₃SiC₂ remains at least up to 10 GPa. On the other hand, the linearity of the Hugoniot equation of state, $D=6.9\text{0}1(22)+1.153(53)u_{\text{p}}$, suggests that the initial structure of Ti₃SiC₂ should be stable up to 112 GPa, in contrast to the result reported by Jordan et al. [J. Appl. Phys., 93 (2003) 9639].     

对煤磨MDC89-7袋式除尘器的节能环保改造

0 前言 湖南韶峰水泥集团有限公司规格为φ2.5 m×3.9 m的风扫式煤磨配套的MDC89-7袋式除尘器于1993年投用,经十多年的生产应用,其导流板及风道损坏达80%左右;外壳、主风道因烧袋和腐蚀,严重变形且花板变得很薄;反吹风道变形穿孔,提升阀密封不严,导致清灰时风量流失严重,运行阻力增加,系统产量降低,且系统中含氧量增加,带来安全隐患;除尘效率下降、污染严重,粉尘排放浓度高达1 g/m3;系统能耗高,且维修强度大(每个滤袋重50kg,每次换袋需12人)且费用高.为此,该公司于2004年4月对该煤磨除尘器进行技术改造,取得了明显的效果.     

光学镜头调制传递函数的测试

为了定量、客观、全面地评价光学镜头的像质,介绍了光学镜头调制传递函数的测试。先简要叙述了测试的原理,并给出计算公式;然后介绍了测试步骤,其中包括固定、穿轴、测试中心视场和测试轴外视场;最后介绍了测试时的注意事项,包括对测试工装的要求、对测试平面的要求和正、负轴外视场测试值相差较大时的处理办法。     

浅谈C语言中循环结构的教学--回答好循环结构的“三个问题”

循环结构是C语言程序设计中的重难点,其掌握情况对于后续章节的学习效果尤为关键。本文以什么是循环、何时需要使用循环以及如何使用循环三个问题为主线,通过精心选择的教学案例和灵活有效的教学方法来进行解答,以激发学生兴趣,培养编程思想。     

锅炉水处理系统除氧器的研制

锅炉和循环水处理系统的氧腐蚀是各种腐蚀中最严重的一种。因此，对给水进行除氧处理应该是最有效的防止腐蚀的方法。本文针对新研制出的新型活性铁除氧剂，又研制出与之相配套的除氧设备。该设备具有理想的除氧效果，常温操作，结构简单，弥补了过去一些除氧设备的不足。     

尿基复合肥生产技术的改进

通过分析尿基复合肥生产过程中出现的问题，并相应提出技术改进措施，优化操作，对复合肥产量的提高和产品质量的控制都取得了明显的效果。     

Fabrication and optical characterization of poly(2,5‐di‐n‐butoxyphenylene) nanofibril arrays

Anodic aluminum oxide (AAO) membrane can be used as template for the synthesized nanostructures. In this article, we have prepared the AAO membrane by using electrooxidation of aluminum substrate in phosphoric acid, and fabricated poly(2,5‐di‐n‐butoxyphenylene) (BuO–PPP) nanofibril arrays by oxidative coupling polymerization of 1,4‐di‐n‐butoxybenzene (DBB) within the pores of the AAO template membrane. The detailed molecular structure of the polymer nanofibrils was characterized by using infrared and ¹H nuclear magnetic resonance spectra, and estimated to consist of almost equal fractions of 1,4‐ and 1,3‐ linkages. We have used transmission electron microscopy, scanning electron microscopy, and atom force microscopy to confirm the morphologies and images of the AAO template membrane and the fabricated nanometer scale of BuO–PPP nanofibril arrays. The experimental results demonstrated that the pores of the AAO membrane were regular and uniform, and parallel each other, and the BuO–PPP chains in the narrowest template‐synthesized nanofibrils were oriented parallel to the porous axes of the AAO membrane and perpendicular to the surface of the aluminum substrate. The polymer chain orientation was partially responsible for the enhanced conductivity. The ultraviolet absorption spectrum of the BuO–PPP nanofibril arrays shown that the polymer contains a better extended π‐conjugation system along poly‐(p‐phenylene) backbone, which resulted in longer wavelength shift of the absorption band, the absorption maxima were located at 258 nm (E₁ absorption band) and 332 nm (E₂ absorption band), respectively. Photoluminescence spectrum of the BuO–PPP nanofibril arrays exhibited a blue emission. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 425–430, 2004     

基于大数据背景下的企业生态系统架构研究

随着全球网络技术与移动通信设备的融合发展,“大数据”时代已经引起社会各界的重点关注。苹果、三星、华为、IBM、微软、腾讯等国际知名企业都开始建构出“大数据”时代的企业生态系统。本文将对“大数据”时代的企业生态系统的演化和建构进行深入分析。