Decentralised event-triggered cooperative control with limited communication

This note studies event-triggered control of Multi-Agent Systems (MAS) with first-order integrator dynamics. It extends previous work on event-triggered consensus by considering limited communication capabilities through strict peer-to-peer non-continuous information exchange. The approach provides both a decentralised control law and a decentralised communication policy. Communication events require no global information and are based only on local state errors; agents do not require a global sampling period or synchronous broadcasting as in sampled-data approaches. The proposed decentralised event-triggered control technique guarantees that the inter-event times for each agent are strictly positive. Finally, the ideas in this note are used to consider the practical scenario where agents are able to exchange only quantised measurements of their states.     

Growth and Deposition of Hygroscopic Particulate Matter in the Human Lungs

Transport and fate of inhaled particulate matter in the human lungs is calculated for realistic physicochemical conditions by a new dosimetry model. The model solves a variant of the general dynamic equation for the size evolution of respirable particles within the human tracheobronchial airways, starting at the tracheal entrance. We focus on ambient anthropogenic aerosols, which are of concern in inhalation toxicology because of their potential irritant and toxic effects on humans. The aerosols considered are polydisperse with respect to size and heterodisperse with respect to thermodynamic state and chemical composition, having initially bimodal lognormal size distribution that evolves with time as a result of condensation-evaporation and deposition processes. The architecture of the human lung is described by Weibel's symmetric bronchial tree. Simulations reveal that, due to the rapid growth of submicron-sized particles, increased number and mass fractions of the particle population can be found in the intermediate size range 0.1 < φ < 1     

Phase separation and morphology in polymer modified colloids

The morphology of films of sterically stabilised polystyrene particles, PS, with added free poly(vinyl alcohol), PVA, and poly(vinyl pyrrolidone), PVP, was investigated with scanning electron microscopy and correlated to the phase behaviour and interactions. In the case of the PS/PVP system exhibiting depletion phase separation, large polymer domains (ca. 7 μm) were present in the solid state when free polymer concentration exceeded ca. 13%. This concentration was well within the two-phase region of the phase diagram. Similar polymer domains were also observed for the homogeneous system PS/PVA. The surface of the films was sealed at free polymer concentrations of ca. 20% and ca. 40% for PVP/PS and PVA/PS, respectively. The final film morphology reflects non-equilibrium conditions arising from the increase in system viscosity due to particle close packing and continuous phase thickening by the free polymer. In the case of PS/PVP systems, incomplete depletion phase separation and phase demixing and prevention of particle restabilisation gives rise to large free polymer domains in the final film. Bridging flocculation was argued to be responsible for the large polymer domains, some with internal structure, observed with the PVA/PS systems.     

Biclustering in data mining

Biclustering consists in simultaneous partitioning of the set of samples and the set of their attributes (features) into subsets (classes). Samples and features classified together are supposed to have a high relevance to each other. In this paper we review the most widely used and successful biclustering techniques and their related applications. This survey is written from a theoretical viewpoint emphasizing mathematical concepts that can be met in existing biclustering techniques.     

Hydraulic fracture closure in a pressure-sensitive elastoplastic medium

This paper examines fracture closure in a Mohr-Coulomb pressure-sensitive dilatant material. The analysis is based on fracture propagation and closure of a plane strain geometry using a fully coupled elastoplastic hydraulic fracturing model. It is shown that the closure pattern of a fracture which has first been propagated is completely different from the closure pattern of a pressurized stationary fracture. A pressurized stationary elastoplastic fracture closes uniformly but remains open after the applied load is released. An elastoplastic fracture which has first been propagated, makes surface contact initially near the fracture tip and subsequently towards the mouth of the fracture. Applications of fracture closure pattern can be found in different aspects of hydraulic fracturing such as in the insitu parameters determination from the inversion of the pressure vs time record and in the closure stress on propped fractures.     

PRO-MOTION: Support for mobile database access

In order to provide data consistency in the presence of failures and concurrency, database methods will continue to be important to the processing of shared information in a mobile computing environment. It is important, therefore, that we develop transaction processing systems that accommodate the limitations of mobile computing, such as frequent disconnection, limited battery life, low-bandwidth communication and reduced storage capacity, so that we can migrate existing database applications to mobile environments. In this paper, motivated by these needs, we propose a mobile transaction processing system that supports disconnected transaction processing in a mobile client-server environment. The proposed system employs compacts, which encapsulate access methods, state information and consistency constraints, to allow for local management of database transactions on mobile computers.     

Model-based control of temperature and energy requirements in a fluidised furnace reactor

The main objective is to improve the control performance during catalyst processing experiments in a furnace heated fluidised bed reactor. A model-based predictive control strategy is implemented for the tight control of the reactor temperature and the overall energy requirements. A detailed dynamic model is developed for the furnace reactor and validated using open-loop experimental data. Dynamic programming techniques are used for the calculation of the optimal sequence of manipulated variables that minimise the difference between the desired and the predicted reactor temperature trajectories. The model predictive control strategy leads to superior performance than the previously installed system that consisted of conventional PID controllers.     

Representation of Crack-Tip Plasticity in Pressure Sensitive Geomaterials: Large Scale Yielding

We model large scale Mohr-Coulomb yielding that accompany fractures in weak rocks, by means of dislocations. The basic equations are derived from a simple model of the crack tip plasticity which represents the plasticity by superdislocations placed at the effective centres of the crack tip process zone.