On the existence of virtual exosystems for synchronized linear networks

When dealing with heterogeneous networks, where the agents are governed by non-identical models, interesting questions arise regarding the ability of the network to synchronize to a common non-trivial output trajectory, as well as the nature of such a trajectory. On this topic, Wieland, Allgöwer, and Sepulchre have recently derived results showing that for a class of heterogeneous networks of dynamically controlled linear agents, non-trivial output synchronization implies the existence of an observable virtual exosystem for which the regulator equations are solvable for each agent. Moreover, this virtual exosystem defines the output trajectories on the agreement manifold and is contained within each agent as an internal model. In this paper, we shed further light on this topic by showing that, under a more general set of assumptions, non-trivial output synchronization can occur in the absence of such a virtual exosystem. We propose a modified result for this case that specifies the existence of a possibly unobservable virtual exosystem for which the regulator equations are solvable, and for which the observable part defines the output trajectories on the agreement manifold. We also show that a variation of the virtual exosystem is contained within each agent as an internal model.     

Exact,almost and optimal input decoupled (delayed) observers

The core of this paper deals with the construction of input-decoupled observers which seek asymptotic estimation of a desired output variable (a linear combination of state and input) of a time-invariant either continuous- or discrete-time system driven by unknown inputs and disturbances. Exact, almost, optimal (suboptimal) and constrained optimal estimation or filtering problems are formulated and studied. All the problems defined and studied here are inherently interconnected, and have a strong common thread of estimation and filtering in the face of the unknown input and external disturbance signals. They are interconnected from a variety of angles, e.g. they are motivated by one another, methods of obtaining the solvability conditions and their methods of solution rely on one another, etc. Thus, a hierarchy of problems and their solutions is built on top of one another. Some of the problems studied here are known in the literature but not in as general a form as is given here, while a majority of the problems studied here are new. A classical variation of all the above problems is also studied here by introducing an l-step delay in estimating the desired output from the measured output. The underlying philosophy throughout this work has been to study most if not all of the facets of estimation and filtering in one stretch under a single folder. Our study of all the above problems has been guided by three important perspectives: (1) obtaining the solvability conditions, both necessary and sufficient; (2) obtaining optimal performance whenever it applies; and (3) developing sound methodologies to design and construct appropriate observers or filters.     

Magnetically Controlled Carbonate Nanocomposite with Ciprofloxacin for Biofilm Eradication

Biofilms are the reason for a vast majority of chronic inflammation cases and most acute inflammation. The treatment of biofilms still is a complicated task due to the low efficiency of drug delivery and high resistivity of the involved bacteria to harmful factors. Here we describe a magnetically controlled nanocomposite with a stimuli-responsive release profile based on calcium carbonate and magnetite with an encapsulated antibiotic (ciprofloxacin) that can be used to solve this problem. The material magnetic properties allowed targeted delivery, accumulation, and penetration of the composite in the biofilm, as well as the rapid triggered release of the entrapped antibiotic. Under the influence of an RF magnetic field with a frequency of 210 kHz, the composite underwent a phase transition from vaterite into calcite and promoted the release of ciprofloxacin. The effectiveness of the composite was tested against formed biofilms of E. coli and S. aureus and showed a 71% reduction in E. coli biofilm biomass and an 85% reduction in S. aureus biofilms. The efficiency of the composite with entrapped ciprofloxacin was higher than for the free antibiotic in the same concentration, up to 72%. The developed composite is a promising material for the treatment of biofilm-associated inflammations.     

First-principles investigation of migration barriers and point defect complexes in B2–NiAl

We perform a systematic first-principles investigation of atomic hop mechanisms in B2–NiAl and discover a low barrier collective hop that can mediate Al diffusion through the anti-structural bridge mechanism. We also find an alternative hop sequence for the migration of a triple defect than that proposed previously. To shed light on the dominant hop mechanisms that mediate diffusion in B2–NiAl, we study point defects and defect clusters in B2–NiAl at high temperature by combining a cluster expansion with Monte Carlo simulations. Going beyond the mean field approximation, we find that the inclusion of interactions among the various point defects is crucial to predict the concentration of defect complexes, such as the triple defects of B2–NiAl. Interactions among point defects also introduce an important degree of short-range order between Al antisite defects and Ni antisite defects. We find an increasing probability between pairs of Al antisite atoms and Ni vacancies as the alloy concentration of B2–NiAl becomes both Al rich and Ni rich, suggesting that the anti-structural bridge mechanism should play an important role in facilitating Al transport.     

Novel ammonia sorbents “porous matrix modified by active salt” for adsorptive heat transformation: 1. Barium chloride in various matrices

Novel composite materials BaCl₂/vermiculite, BaCl₂/γ-Al₂O₃ and BaCl₂/(carbon Sibunit) have been synthesised by impregnation of the three porous matrices with barium chloride and studied as ammonia sorbents. Isosters of ammonia sorption are measured at T = 15–80 °C and P = 0.7–9 bar. It was found that a modification of the host matrices by the salt increases the ammonia uptake due to a chemical reaction between ammonia and barium chloride. The enthalpy and entropy of ammonia sorption by the salt confined to the mesopores of alumina and Sibunit are significantly smaller with regard to those for the bulk salt. This indicates that the salt confinement to the small pores allows tuning its sorption properties. In the large vermiculite pores the properties remain unchanged. Based on the experimental isosteric charts, the feasibility of the new materials for adsorptive heat transformation has been analyzed. For composite BaCl₂/vermiculite the coefficient of performance (COP) for ice making and air conditioning cycles calculated from the ammonia sorption data can reach 0.6 which seems quite encouraging from a practical point of view.     

Formation and crosslinking of latex films through the reaction of acetoacetoxy groups with diamines under ambient conditions

We investigated the processes of film formation, polymer diffusion, and crosslinking of latex films at ambient temperature, using low T_g methacrylate latex bearing acetoacetoxy groups, and curing the systems with 1,6-hexanediamine as the crosslinker. The addition of diamine induces floc formation, which modifies the rheological properties of the dispersion and increases its drying rate when coated onto a substrate. The crosslinking reaction between diamine and acetoacetoxy groups occurs at a rapid rate, even in the dispersed state. Although the crosslinking reaction precedes polymer diffusion in the two systems we examined, latex films with relatively good solvent resistance are obtained. Department of Chemistry, Toronto, Ontario, Canada M5S 3H6. Department of Polymer Chemistry, P. O. Box 513, 5600 MB Eindhoven, The Netherlands.     

Modern Photoelasticity for Residual Stress Measurement in Glass

Abstract:  This paper gives a review of modern photoelastic technology for residual stress measurement in various glass articles, including glass articles of complicated shape. For residual stress measurement in axisymmetric glass articles, integrated photoelasticity is being used by many glass companies and research laboratories. In case of non-axisymmetric glass articles of complicated shape, photoelastic tomography is used. As for automotive and architectural glass panels used in buildings, surface stress can be measured with the mirage method. More complete stress analysis can be carried out with the scattered light method. The paper is illustrated by numerous examples.