中立型灰色随机分布时滞系统的指数鲁棒稳定性

为了得到一类中立型灰色随机分布时滞系统的指数鲁棒稳定性,本文利用Lyapunov-Krasovskii泛函法、灰矩阵的连续矩阵覆盖的分解技术和Ito公式,分别得到了以非线性矩阵不等式和线性矩阵不等式(LMI)表示的该系统指数鲁棒稳定的时滞依赖性判据。对非线性矩阵不等式判据,我们给出了一般性算法,解决了非线性矩阵不等式判据不便于实际应用的问题。数值例子表明,本文所给判据是有效的,且系统的指数稳定性和时滞,随着绝对灰度矩阵的谱范数的增大而减小。     

中立时变时滞系统的稳定性与H∞滤波器设计

研究一类中立时变时滞系统的稳定性和H∞滤波器设计问题.通过构建一个新的李雅普诺夫泛函,采用新的积分不等式方法和交互式凸组合方法,得到了该中立时变时滞系统线性矩阵不等式形式的稳定性判据,给出了中立时变时滞系统H∞滤波器的设计方法.仿真实例表明,采用提出的上述方法得到的结果具有更小的保守性,且所设计的中立时变时滞系统H∞滤波器是有效的.     

一类中立型时滞系统新的鲁棒稳定性准则

本文考虑了一类具有时变时滞和非线性扰动的中立型系统的鲁棒稳定性问题.基于Lyapunov稳定性理论和自由权矩阵方法,得到保证系统鲁棒渐近稳定的新的充分条件.所得结果同时依赖于离散时滞和中立时滞,并用LMIs表示.由于对Lyapunov泛函导数采用了无保守的估计,因此所得结果具有较小的保守性,能够给出时变时滞较大的允许时...     

不确定变时滞模糊随机系统鲁棒稳定性

本文研究了不确定T-S模糊随机时滞系统的时滞相关鲁棒稳定性问题,这里的不确定性是范数有界的.通过构造新的Lyapunov泛函和矩阵不等式引理,利用具有时滞的非线性随机系统的Lypaunov稳定性理论和自由权矩阵方法,导出了使系统鲁棒均方指数稳定的时滞相关线性矩阵不等式(LMI)条件.该判据具有较低的保守性,适用时滞变化率大于1的情形.最后通过数值例子验证了所得结果的有效性.     

具多变时滞中立型奇异微分系统的稳定性(英文)

本文讨论了中立型奇异泛函微分系统的稳定性问题.利用V泛函方法和差分算子的稳定性获得具变时滞中立型奇异微分系统的渐近稳定性判据.所得结果被描述为矩阵等式或者矩阵不等式,在计算上是可行和有效的,并给出例子说明了所得结果.     

含有非线性扰动的时滞随机微分系统的鲁棒均方稳定性

研究一类含有非线性扰动的多时变时滞随机微分系统在有记忆状态的反馈控制器下的鲁棒均方稳定性问题.通过构造Lyapunov-Krasovskii泛函,运用Ito公式,引入适当的自由权矩阵,利用积分不等式和分析技巧,基于线性不等式(LMI)方法和Schur补定理,获得含该系统的鲁棒均方渐近稳定和鲁棒均方指数稳定,并给出了相应反馈控制器设计.所得结果与时滞和随机干扰相关,丰富了已有的结果.     

线性时滞广义系统的时滞相关稳定性新判据

提出一种新的方法——积分不等式方法讨论线性时滞广义系统的时滞相关稳定性.首先将广义系统转化为一个带约束条件的中立型系统,然后利用基于二次型项的积分不等式,采用Lyapunov-Krasovskii泛函方法,获得了系统稳定的、基于线性矩阵不等式（LMI）的时滞相关充分条件.实例表明,本文方法得到的结论较已有文献具有较小的保守性.     

线性时变时滞系统稳定性的新判据

目的:讨论一类具有时变时滞的线性系统渐近稳定性分析问题。方法:采用改进的三重积分不等式和凸组合方法,研究一类时变时滞线性系统渐近稳定的充分条件。结果:首先给出了一个新的改进的三重积分不等式;进而通过新构造的Lyapunov-Krasovskii泛函,基于新得到的三重积分不等式估计Lyapunov-Krasovskii泛函导数项中的三重积分项,并结合凸组合方法得到了时变时滞线性系统的渐近稳定性新判据。结论:该稳定性判据具有更小的保守性,仿真实例表明了本文方法的有效性。     

不确定多重时滞中立系统的时滞相关鲁棒H∞控制

本文利用一个新的积分不等式方法讨论了一类不确定多重时滞中立系统的时滞相关鲁棒H∞控制器设计问题.该中立系统的状态项、控制项、微分项、外部干扰输入项均含有时滞.首先,利用Lyapunov稳定性理论,推导出系统鲁棒可镇定的充分条件.在此基础上,进一步给出了鲁棒H∞控制器存在的充分条件.不需要对原系统进行模型变换,仿真算例说明了定理的可行性.     

一类具有范数有界不确定性的非线性时滞系统的控制

本文研究了一类具有范数有界不确定性的非线性时滞系统的鲁棒稳定性及其控制问题,结合Lyapunov稳定性定理、线性矩阵不等式及自由权矩阵,给出了系统的状态反馈鲁棒二次稳定的充分条件以及控制器的设计,并建立了一个具有线性矩阵不等式约束的凸优化问题,得到不确定时滞系统的最优状态反馈控制律.仿真示例说明了该方法的可行性.     

共沉淀法合成La_(0.9)Sr_(0.1)Ga_(0.8)Mg_(0.2)O_(3-δ)及其性质的研究

采用共沉淀法合成了具有钙钛矿结构的中温固体电解质La_(0.9)Sr_(0.1)Ga_(0.8)Mg_(0.2)O_(3-δ)(LSGM),并用DTA-TGA和X射线衍射仪分析了LSGM材料中钙钛矿相的形成过程,采用SEM、交流阻抗谱等检测技术对LSGM电解质的结构及性能进行了表征.XRD分析结果表明,1200℃烧结后,粉体开始形成钙钛矿结构,随温度的升高粉体中杂相含量越来越少,于1450℃时形成了单一的钙钛矿相结构.     

Degradation behaviour of sputtered Co–Al coatings on superalloy

Degradation behaviour of sputtered Co–Al coatings on Superni-718 substrate has been investigated. Cyclic high temperature oxidation tests were conducted on uncoated and coated samples at peak temperatures of 900 °C for up to 100 thermal cycles between the peak and room temperatures. The results showed that a dense scale formed on the coated samples during thermal cycling at the peak temperature of 900 °C. The external scale exhibited good spallation resistance during cyclic oxidation testing at both temperatures. The improvement in oxide scale spallation resistance is believed to be related to the fine-grained structure of the coating. Nanostructured Co–Al coatings on Superni-718 substrate were deposited by DC/RF magnetron sputtering. FE-SEM/EDS, AFM, and XRD were used to characterize the morphology and formation of different phases in the coatings, respectively. The Co–Al coating on superalloy substrate showed better performance of cyclic high temperature oxidation resistance due to its possession of β-CoAl phase as Al reservoir and the formation of Al₂O₃ and spinel phases such as CoCr₂O₄ and CoAl₂O₄ in scale. The oxidation results confirmed an improved oxidation resistance of the Co–Al coating on superalloy as compare to bare substrate in air at 900 °C temperature up to 100 cycles.     

非晶Sm5Fe74.3Nb1.5Si11.7B4.5C2.5Cu0.5合金经预退火后的晶化动力学的DTA研究

研究了非晶Sm5Fe74.3Nb1.5Si11.7B4.5C2.5Cu0.5合金经400℃，保温10min预退火后的晶化动力学。结果表明；该合金的晶化相为α-Fe固溶体和Sm2Fe17Cx金属间化合物，两相的晶化表观激活能分别为557KJ/mol和514KJ/mol，当晶化体积分数为60%时，α-Fe相的晶化激活能达极大值；Sm2Fe17Cx相晶化激活能则随其晶化体积分数的增加而逐渐减小。     

Study of the interface behaviour between MABS/TPU bi-layer structures obtained through over moulding

The strength of adhesion between two over-moulded polymers, methylmethacrylate–butadiene–styrene copolymer (MABS) and thermoplastic polyurethane (TPU) that constitute a bi-component laminar system has been the subject of study. Results showed that at the bi-layer interface the adhesive fracture toughness increases as temperature and surface roughness are increased. Roughness has been demonstrated to be the most important parameter defining adhesion strength and failure. With the increase of roughness the failure was observed to change from adhesive towards cohesive type. An increase in either the temperature or the pressure applied to the samples caused a rise in adhesion energy. However, pressure seemed to have a minor effect in comparison to temperature. Significant increments in adhesion were obtained after applying the corona discharge treatment (CDT) to the attaching surfaces resulting in adhesion strengths almost double those of non-treated systems.     

Thermal design and performance of the SCUBA-2 instrument 1-K and mK systems

Various research fields require large and complex instruments containing detectors operating at millikelvin temperatures. The materials and techniques traditionally used in cryogenics are often unsuitable for the demanding requirements of such instruments. We describe the thermal design and performance of the 1-K and millikelvin systems of the SCUBA-2 instrument. This is an astronomical “camera” operating at wavelengths of 450 and 850 μm. It is the largest and most complex instrument ever built for sub-mm astronomy, and the first to use a cryogen-free dilution refrigerator. The design consists of a mix of traditional techniques (but used in demanding situations) as well as novel elements. The thermal performance has been stable and very successful, and we hope that the details described here will be useful to the designers of future large instruments.     

Influence of mould design on the solidification of heavy forging ingots of low alloy steels by numerical simulation

Ingot casting of a 6-ton, heat-treatable Cr–Mo low alloy steel was simulated using finite element method in three dimensions. Effects of casting parameters including bottom pouring rate, mould slenderness ratio, mould slope, and height and shape of the hot top isolate on solidification behaviour and crack susceptibility during subsequent hot forging of the ingot were investigated. The simulation model was validated against experimental data of two different ingot mould designs. Influences of the casting parameters on the riser efficiency and possible crack formation in the intersection of hot top and ingot body during subsequent open-die forging of the cast steel ingots were discussed. Results showed that pouring the melt under a constant rate, reducing the mould slenderness ratio, and using a proper design for the hot top isolate would all improve the riser efficiency and thereby possibly reduce crack susceptibility during subsequent hot forging.     

Materials’ tactile testing and characterisation for consumer products’ affective packaging design

Touch is one sense through which people judge consumer products. How materials’ properties influence these judgments is the topic of this paper. People’s sensorial or psycho-physical judgments (by touch) of the roughness, softness, slipperiness and warmth of 37 material samples are reported as well as their affective judgments, such as how pleasurable, exciting, indulgent, the samples felt. Physical measurements are also reported of the samples’ coarse and fine surface finishes, compliance, sliding friction and thermal contact properties. Relationships between the affective and sensorial judgments and the physical measurements are explored. A relational hierarchy is established from the physical measurements to the sensorial to the affective judgements. By following the dependencies in reverse, from the affective to the sensorial to the physical level, the required material surface properties to transmit intended affective messages to consumers might be determined. However, further work is needed on how to quantify some aspects of surface properties, particularly of roughness and sliding friction, in a manner useful for relating to affect. The methods described currently support communication and decision taking during the product development process.     

Thermal Stability of Amorphous Hydride Mg_(50)Ni_(50)H_(54) and Mg_(30)Ni_(70)H_(45)

The thermal stability of amorphous ternary hydrides Mg_(50)Ni_(50)H_(54) and Mg_(30)Ni_(70)H_(45) and their corre-sponding amorphous binary alloys Mg_(50)Ni_(50) and Mg_(30)Ni_(70) were studied with X-ray diffraction(XRD) and differential scanning calorimetry(DSC). Samples of the amorphous alloys were preparedby mechanical alloying and the amorphous hydrides were obtained by charging the alloys with gas-eous hydrogen at 3.0 MPa and 423 K. It was found that the amorphous hydrides released most oftheir hydrogen before the crystallization of the essentially hydrogen depleted amorphous alloy. Thecrystallization temperature of amorphous Mg_(50)Ni_(50)H_(54) elevated and that of amorphousMg_(30)Ni_(70)H_(45) did not change in relation to the original binary amorphous alloy. This is very excep-tional for amorphous hydrides. The reason for the effects of hydrogen absorption/desorption on thecrystallization of amorphous alloys was discussed.     

PMMA单分子膜成膜特性研究

研究了ＰＭＭＡ单分子膜的成膜特性及其结构．结果表明，ＰＭＭＡ能够在较大的表面压范围内形成稳定的单分子膜，并且具有不可重复压缩性、表面压力的各向异性和松驰特性．ＴＥＭ照片显示，ＰＭＭＡ分子链在单分子膜中是有序平行排列的