Stochastic reliable control of a class of uncertain time-delay systems with unknown nonlinearities

Copyright [2001] IEEE. This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of Brunel University's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.This paper investigates the robust reliable control problem for a class of nonlinear time-delay stochastic systems. The system under study involves stochastics, state time-delay, parameter uncertainties, possible actuator failures and unknown nonlinear disturbances, which are often encountered in practice and the sources of instability. Our attention is focused on the design of linear state feedback memoryless controllers such that, for all admissible uncertainties as well as actuator failures occurring among a prespecified subset of actuators, the plant remains stochastically exponentially stable in mean square, independent of the time delay. Sufficient conditions are proposed to guarantee the desired robust reliable exponential stability despite possible actuator failures, which are in terms of the solutions to algebraic Riccati inequalities. An illustrative example is exploited to demonstrate the applicability of the proposed design approac

Use of elastic stability analysis to explain the stress-dependent nature of soil strength

The peak and critical state strengths of sands are linearly related to the stress level, just as the frictional resistance to sliding along an interface is related to the normal force. The analogy with frictional sliding has led to the use of a ‘friction angle’ to describe the relationship between strength and stress for soils. The term ‘friction angle’ implies that the underlying mechanism is frictional resistance at the particle contacts. However, experiments and discrete element simulations indicate that the material friction angle is not simply related to the friction angle at the particle contacts. Experiments and particle-scale simulations of model sands have also revealed the presence of strong force chains, aligned with the major principal stress. Buckling of these strong force chains has been proposed as an alternative to the frictional-sliding failure mechanism. Here, using an idealized abstraction of a strong force chain, the resistance is shown to be linearly proportional to the magnitude of the lateral forces supporting the force chain. Considering a triaxial stress state, and drawing an analogy between the lateral forces and the confining pressure in a triaxial test, a linear relationship between stress level and strength is seen to emerge from the failure-by-buckling hypothesis

Modelling localised fracture of reinforced concrete structures

This paper presents a robust finite element procedure for simulating the localised fracture of reinforced concrete members. In this new model the concrete member is modelled as an assembly of plain concrete, reinforcing steel bar and bond-link elements. The 4-node quadrilateral elements are used for 2D modelling of plain concrete elements, in which the extended finite element method is adopted to simulate the formation and growth of individual cracks. The reinforcing steel bars are modelled by using a 3-node beam-column element. 2-node bond-link elements are employed for modelling the interaction between plain concrete and reinforcing steel bar elements. It is evident that the nonlinear procedure proposed in this paper can properly model the formation and propagation of individual localised cracks within the reinforced concrete structures. The model presented in this paper enables the researchers and designers to access the integrity of reinforced concrete members under extreme loading conditions by using mesh independent extended finite element method.The support of the Engineering and Physical Sciences Research Council of Great Britain under Grant No. EP/I031553/1

Progenitor-like cells derived from mouse kidney protect against renal fibrosis in a remnant kidney model via decreased endothelial mesenchymal transition

Showing A quantification of GFP-positive cells in the lung after intravenous injection of MKPCs in five-sixths nephrectomized mice (y axis shows the number of cells, while the x axis (FL1-H) shows the fluorescence intensity; M1 is the area of GFP-positive cells) and B immunohistochemistry of the lung after intravenous injection of MKPCs into a mouse that underwent five-sixths nephrectomy. Few GFP positive cells were found in the lung at the first day but there were no GFP-positive cells at week 14. (TIFF 2253 kb

Exploring the micro-mechanics of triaxial instability in granular materials

The instability of granular materials due to water infiltration under fully drained conditions has been previously considered in experimental studies. While laboratory experiments can provide macro-scale insight into drained instability, the micro-mechanics under such conditions are yet to be explored. This study has employed the discrete-element method (DEM) to simulate constant shear drained (CSD) tests for an ideal soil. CSD tests were initiated from a range of packing densities and stress conditions. The DEM simulations were able to qualitatively replicate laboratory CSD tests. The choice of the loading control parameter was seen to play a central role in the macro-scale second-order work to identify an effective failure. All samples considered attained an onset of instability that coincided with fluctuations in the second-order work from a particle scale. The time of occurrence of the onset of instability was seen to depend on initial packing density and stress state. A change in the evolution of macro- and micro-mechanical quantities, showing either a sharp increase or decrease, was observed once the CSD conditions had been reached. Finally, conventional drained then constant volume (CDCV) tests were carried out where the appearance of instabilities and the evolution of macro and micro quantities were found to be different from those observed in CSD tests. The results presented in this study indicate that the constant shear drained loading conditions can result in more unfavourable situations than for the undrained loading condition

Transformation Pathways of Silica under High Pressure

Concurrent molecular dynamics simulations and ab initio calculations show that densification of silica under pressure follows a ubiquitous two-stage mechanism. First, anions form a close-packed sub-lattice, governed by the strong repulsion between them. Next, cations redistribute onto the interstices. In cristobalite silica, the first stage is manifest by the formation of a metastable phase, which was observed experimentally a decade ago, but never indexed due to ambiguous diffraction patterns. Our simulations conclusively reveal its structure and its role in the densification of silica.Comment: 14 pages, 4 figure

Exploiting Polyhedral Symmetries in Social Choice

A large amount of literature in social choice theory deals with quantifying the probability of certain election outcomes. One way of computing the probability of a specific voting situation under the Impartial Anonymous Culture assumption is via counting integral points in polyhedra. Here, Ehrhart theory can help, but unfortunately the dimension and complexity of the involved polyhedra grows rapidly with the number of candidates. However, if we exploit available polyhedral symmetries, some computations become possible that previously were infeasible. We show this in three well known examples: Condorcet's paradox, Condorcet efficiency of plurality voting and in Plurality voting vs Plurality Runoff.Comment: 14 pages; with minor improvements; to be published in Social Choice and Welfar

W::Neo: A Novel Dual-Selection Marker for High Efficiency Gene Targeting in Drosophila

We have recently developed a so-called genomic engineering approach that allows for directed, efficient and versatile modifications of Drosophila genome by combining the homologous recombination (HR)-based gene targeting with site-specific DNA integration. In genomic engineering and several similar approaches, a “founder” knock-out line must be generated first through HR-based gene targeting, which can still be a potentially time and resource intensive process. To significantly improve the efficiency and success rate of HR-based gene targeting in Drosophila, we have generated a new dual-selection marker termed W::Neo, which is a direct fusion between proteins of eye color marker White (W) and neomycin resistance (Neo). In HR-based gene targeting experiments, mutants carrying W::Neo as the selection marker can be enriched as much as fifty times by taking advantage of the antibiotic selection in Drosophila larvae. We have successfully carried out three independent gene targeting experiments using the W::Neo to generate genomic engineering founder knock-out lines in Drosophila

Harnessing Surface-Functionalized Metal-Organic Frameworks for Selective Tumor Cell Capture

A platform based on a metal-organic framework (MOF) bearing free carboxylic acid groups has been developed for tumor cell capture and potential drug screening applications. A zinc-based MOF expressing uncoordinated carboxylic acids (ZnMOF-COOH) was grown on a ZnO substrate. Post-synthetic modification (PSM) of the acid groups gave a composite material that expressed peptide linkages and allowed the immobilization of anti-epithelial cell adhesion molecule (anti-EpCAM) antibody. This strategy offers a universal method for the controllable immobilization of antibodies and even enzymes on the surface of a MOF. The resulting immunotrapper exhibited excellent capture ability, demonstrating high efficiency and selectivity towards EpCAM-positive tumor cells. The promotion of tumor cell adhesion is attributed to the 3-dimentional (3D) structure of the composite, which revealed spine-like microstructures.This work was financially supported by the National Natural Science Foundation of China (Grant Nos. 21527809 and 21575007), the China Scholarship Council and the UK EPSRC (EP/J500380/1)