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81.
This paper considers the robust stability of a linear time-invariant state space model subject to real parameter perturbations.
The problem is to find the distance of a given stable matrix from the set of unstable matrices. A new method, based on the
properties of the Kronecker sum and two other composite matrices, is developed to study this problem; this new method makes
it possible to distinguish real perturbations from complex ones. Although a procedure to find the exact value of the distance
is still not available, some explicit lower bounds on the distance are obtained. The bounds are applicable only for the case
of real plant perturbations, and are easy to compute numerically; if the matrix is large in size, an iterative procedure is
given to compute the bounds. Various examples including a 46th-order spacecraft system are given to illustrate the results
obtained. The examples show that the new bounds obtained can have an arbitrary degree of improvement over previously reported
ones.
This work has been supported by the Natural Sciences and Engineering Research Council of Canada under Grant No. A4396. 相似文献
82.
83.
The network model is given and used to calculate the oscillating frequency of thermoacoustic prime mover. Theoretically calculated frequency by the model is plural, whose real part denotes actual frequency of the system, and imaginary part means attenuation coefficient of acoustic pressure. Numerical calculation is made under different conditions including different acoustic cavities, spacing between each parallel plate, gas pressures and system lengths. Theoretically calculated frequency and experimentally measured frequency are in quite good agreement. 相似文献
84.
Qiang Wang Yi Shen Ye Zhang Jian Qiu Zhang 《IEEE transactions on instrumentation and measurement》2003,52(4):1041-1047
Hyperspectral image fusion is a key technique of hyperspectral data processing. In recent years, many fusion methods have been proposed, but there is little work concerning evaluation of the performances of different image fusion methods. In this paper, a method called quantitative correlation analysis (QCA) is proposed, which provides a quantitative measure of the information transferred by an image fusion technique into the output image. Using the proposed method, the performances of different image fusion methods can be compared and analyzed directly based on the images of before and after performing the fusion. The correlation information entropy, based on the developed QCA, is also proposed and testified by numerical simulations. Typical hyperspectral data are applied to the proposed method. The results show that the method is effective, and its conclusions agree with the classification results in applications. 相似文献
85.
建立五大创新体系促进绿色建筑发展 总被引:2,自引:0,他引:2
我们正站在一个新的历史起点上,同时处在一个非常重要的关口。在世界范围内,以大量消耗原材料和能源为特征的传统经济正在逐渐失去昔日的荣耀。由资源依赖型转向创新驱动型,真正实现经济增长方式的转变,已成为正处于快速城镇化、工业化与机动化进程之中的我国经济发展面临的非常迫切的重大战略选择。在未来30年内,我国还需建造400亿m2的新建筑,建筑数量和建设速度都是世界发展史上所罕见的。建筑属于长期的消费品,不可能进行频繁的更新。仅延长建筑使用寿命或装修期限,就意味着能源和资源的大量节约与环境污染的减少。绿色建筑是指为人们提… 相似文献
86.
Yang Lüyun 《中国稀土学报(英文版)》2006,24(Z2)
The fabrication of one kind of large core area Nd3 doped silicate glass photonic crystal fiber, and demonstration of the fiber's waveguidence properties were reported. This fiber owns a random air hole distribution in the cladding. The measured minimum loss of this kind of fiber is 10 dB·m-1 at 660 nm. These fibers can sustain only a single mode at least over wavelength ranging from 660 nm to 980 nm. 相似文献
87.
Jun Rong Li Jun Wang Jia Rui Xu Ming Qiu Zhang Min Zhi Rong Qiang Zheng 《Composites Science and Technology》2006,66(16):3126-3131
The authors of this paper synthesized a series of amphiphilic triblock copolymers of polystyrene-b-poly(ethylene glycol)-b-polystyrene (PS-PEG-PS) having different PEG/PS ratios with nearly identical molecular weights of the entire copolymers. The interfacial interactions in the composites consisting of carbon black and the copolymers can thus be tailored. When these conducting composites are exposed to certain solvent vapors, their electrical resistances greatly increase, showing the gas sensitivity. The present work indicated that this switching behavior is controlled by the structural relaxation of the composites because matrix swelling acts as the main mechanism. The response time has been correlated with absolute temperature by Arrhenius equation, and the estimated activation energy reflects mobility of the fillers involved in the solvent induced expansion of the surrounding polymer. Therefore, by using the gas sensibility of the conductive composites, the structure evolution of the composite materials in solid state and the effect of filler/matrix interfacial interaction on the relaxation property of the matrix polymer has been inspected. It was found that lower activation energy represents stronger interfacial interaction in case good solvent of the matrix was used for the test. 相似文献
88.
Biomimetic synthesis of spherical nano-hydroxyapatite in the presence of polyethylene glycol 总被引:1,自引:0,他引:1
Spherical nano-hydroxyapatite (nano-HA) was synthesized successfully by a biomimetic method using Ca(NO3)2·4H2O and (NH4)3PO4·3H2O as reagents in the presence of polyethylene glycol (PEG). The crystalline phase, microstructure, chemical composition, and morphology of the obtained samples were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). The results show that spherical nano-HA with diameter of 30–50 nm can be synthesized in the presence of a certain concentration (2–6%) of PEG. The crystallinity of HA powder synthesized in the presence of PEG was higher than that synthesized in the absence of PEG, but the crystallinity of HA reduced with increasing the concentration of PEG. The electrical conductivity (EC) of the solution revealed that PEG reduced the transfer rate of Ca2+ in the process of HA crystallization, indicating the interaction between PEG and HA. The possible mechanism of formation spherical nano-HA was discussed. 相似文献
89.
90.
A new efficient numerical method and the dynamic analysis of composite laminates with piezoelectric layers 总被引:1,自引:0,他引:1
Firstly, a numerical method for the inversion of Laplace transform is developed and its accuracy is shown through examples. Then, a state-vector equation for the dynamic problems of piezoelectric plates is deduced directly from a modified mixed variational principle for piezoelectric bodies and its exact solution for the dynamic problems of simply supported rectangle piezoelectric plate is simply given. For multilayered hybrid plates, we derive the solution in terms of the propagator matrices. The techniques accounts for the compatibility of generalized displacements and generalized stresses on the interface both the elastic layers and piezoelectric layers, and the transverse shear deformation and the rotary inertia of laminate are also considered in the global algebraic equation of structure. Meanwhile, there is no restriction on the thickness and the number of layers. As an application of the numerical inversion of Laplace transform presented in this paper, typical numerical examples of the harmonic vibration and transient response are proposed and discussed. Since the highly accurate numerical results, they can serve as benchmarks to test various thick plate theories and various numerical methods, such as the finite and boundary element methods for transient response problems. 相似文献