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排序方式: 共有168条查询结果,搜索用时 31 毫秒
61.
Robust Decentralized Stabilization of Uncertain Large-Scale Discrete-Time Systems with Delays 总被引:3,自引:0,他引:3
J.H. Park 《Journal of Optimization Theory and Applications》2002,113(1):105-119
This paper describes the synthesis of robust decentralized controllers for uncertain large-scale discrete-time systems with time delays in the subsystem interconnections. Based on the Lyapunov method, a sufficient condition for robust stability is derived in terms of a linear matrix inequality (LMI). The solutions of the LMIs can be obtained easily using efficient convex optimization techniques. A numerical example is given to illustrate the proposed method. 相似文献
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Several models of fragmentation have been studied that suppose random fracture forces. In this article, we did a numerical study on a dynamic model for fragmentation in which the fracture forces are generated by neighboring fragments and are proportional to the size of the common boundary between two fragments. The following assumptions were also considered: the material defects are represented by a random distribution of point flaws; the total mass is conserved; and the iterative fracture of each fragment is randomly stopped by a condition that considers a constant probability and a minimal fragment size. The motivation for this model was to determine under what circumstances a continuous fragmentation model with fracture forces defined by the neighbors’ interaction produces results that are in agreement with the experimental evidence. The main result of this work establishes that the fragment size distribution follows a power-law for fragments of greater area than the minimal fragment size mfs. The visualizations present complex fracture patterns that resemble real systems. 相似文献
64.
Zhuang LU Li-Yan ZHAO Yang-Jun ZHANG Yun CAI Yu-Lin DENG Yu-Kui ZHANG Xiao-Hong QIAN 《分析化学》2009,37(7):950-954
Biological mass spectrometry has been developed for the large-scale protein identification. The successful identification of protein in proteomic study is based on an effective match of MS data to the sequence in database. At times, because of the diversity and heterogeneity of protein modification, the experimental data obtained by mass spectrometry does not match the theoretical value; hence, approximately 90 percent or more of the tandem mass spectra cannot be identified effectively. This has become one of the most important technique issues to be resolved in current proteome research. The N-terminal cyclization of peptides, as one of a variety of modification introduced in sample preparation, has been preliminarily studied in this work. The result showed that N-terminal cyclization occurred in most of the glutamine (Q) or carbamoylmethyl-cysteine (CAM_C) residues, and the reaction is often incomplete or partial; both types of peptides can often exist in its respective state at the same time, and the behavior of modified peptides in reversion phase chromatography is changed. The success rate of protein identification could be obviously improved by the addition of the N-terminal cyclization modification in the database searching. These results will be very helpful in the mass spectrometric data analysis of proteomic study. 相似文献
65.
D. Bradley M. Lawes R. Mumby Pervez Ahmed 《Proceedings of the Combustion Institute》2019,37(2):1807-1813
The paper presents the results of a fundamental experimental and theoretical study of Darrieus–Landau, thermo-diffusive, instabilities in atmospheric explosions, and, on a smaller scale, in laboratory explosions in closed vessels. Pressure dependencies were sought to exploit the leading role of the Peclet number in the phenomena, so that similar Peclet numbers were achieved in both instances. However, in large atmospheric explosions large Peclet numbers were achieved by the size of the fireball, whereas in the closed vessel explosion it was achieved at a higher pressure by a much smaller flame, but because of the higher pressure, one endowed with a small laminar flame thickness. This study covers a much wider range of fuels and of pressures and the dependencies of the phenomena on both of these were carefully studied, although, for the atmospheric explosions, the data only covered propane and methane. The roles of both Markstein and Peclet numbers become clear and give rise to a more fundamental correlating parameter, a critical Karlovitz number, Kcl, for flame stability. This is based on the flame stretch rate, normalised by its multiplication by the chemical reaction time in a laminar flame. The experimentally measured dependencies of this key parameter on pressure and Markstein number are reported for the first time for so many different fuels. The critical Karlovitz number for flame stability decreases with increase in the strain rate Markstein number. As a result, it is possible to predict the extent of the unstable regime for laminar flames as a function of Masr and pressure. Such data can be used to estimate the severity of large scale atmospheric explosions. As Masr becomes highly negative, the regime of stability is markedly reduced. 相似文献
66.
A model is presented for the simulation of reactive gas-solids flows in large industrial reactors. Circulating fluidized bed (CFB) combustors with several thousands of cubic meters reaction volume are probably the largest reactors of this type. A semi-empirical modeling approach has been chosen to model the three-dimensional concentration distributions of gas and solids components and temperatures inside the combustion chamber of such boilers. Two industrial CFB boilers are investigated in detail: the 105 M... 相似文献
67.
We develop a non-linear relativistic model of the Shapley Concentration (SC) and its environs, including the Great Attractor (GA) and the Local Group (LG). We take the Shapley Concentration as a major attractive centre, and we use the Lemaître–Tolman model. We constrain our model with present day observations, plus the requirement that it have a physically reasonable evolution from small perturbations at last scattering. We investigate possible mass and velocity distributions, and we find that the peculiar velocity maximum near the SC is ~800 km/s inwards, the density between GA and SC must be about ~0.9 times background, the mass of the GA is probably 4–6 × 1015 M⊙, the SC’s contribution to the LG motion is negligible, and the value of the cosmological constant is not significant on this scale. 相似文献
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The turbulent momentum transport phenomena in a two-dimensional mixing layer are investigated numerically by a discrete vortex method. The numerical model and calculations are verified through a comparison with existing numerical simulations and experimental measurements. The main emphasis is placed on the exploration of the detailed time-dependent instantaneous local momentum fluctuations and on the comparison of numerical results with available experimental measurements. The current simulations confirm qualitatively the various trends in the turbulent momentum flux and fluctuating components of the velocity in the mixing layer found with several experimental results. The study shows that similarity exists in turbulent momentum quantities along the axial direction of the mixing layer. The calculations also show a definite correlation between the passage of a large-scale structure and a burst in the turbulent momentum flux. The probability density functions of the fluctuating quantities are shown to be mostly Gaussian-like, with only a few exceptions. 相似文献