ACT-P: A configurable theorem-prover

There has been a considerable amount of research into the provision of explicit representation of control regimes for resolution-based theorem provers. However, most of the existing systems are either not adequate or too inefficient to be of practical use. In this paper a theorem prover, ACT-P, which is adequate but retains satisfactory efficiency is presented. It does so by providing a number of user-changeable heuristics which are called at specific points during the search for a proof. The set of user-changeable heuristics was determined on the basis of a classification of the heuristics used by existing resolution-based theorem provers.     

Autominder: an intelligent cognitive orthotic system for people with memory impairment

The world’s population is aging at a phenomenal rate. Certain types of cognitive decline, in particular some forms of memory impairment, occur much more frequently in the elderly. This paper describes Autominder, a cognitive orthotic system intended to help older adults adapt to cognitive decline and continue the satisfactory performance of routine activities, thereby potentially enabling them to remain in their own homes longer. Autominder achieves this goal by providing adaptive, personalized reminders of (basic, instrumental, and extended) activities of daily living. Cognitive orthotic systems on the market today mainly provide alarms for prescribed activities at fixed times that are specified in advance. In contrast, Autominder uses a range of AI techniques to model an individual’s daily plans, observe and reason about the execution of those plans, and make decisions about whether and when it is most appropriate to issue reminders. Autominder is currently deployed on a mobile robot, and is being developed as part of the Initiative on Personal Robotic Assistants for the Elderly (the Nursebot project).     

Using a hybrid rule-based approach in developing an intelligent tutoring system with knowledge acquisition and update capabilities

In this paper, we present the architecture and describe the functionality of an Intelligent Tutoring System (ITS), which uses an expert system to make decisions during the teaching process. The expert system uses neurules for knowledge representation of the pedagogical knowledge. Neurules are a type of hybrid rules integrating symbolic rules with neurocomputing. The expert system consists of three components: the user modelling unit, the pedagogical unit and the inference system. The pedagogical knowledge is distributed in a number of neurule bases within the user modelling and the pedagogical unit. Another important component of the ITS, for both its development and maintenance, is its knowledge management unit, which provides knowledge acquisition and knowledge update capabilities to the system, that is, offers expert knowledge authoring capabilities to the system.     

Thermoresponsive behaviour in aqueous solution of poly(maleic acid‐alt‐vinyl acetate) grafted with poly(N‐isopropylacrylamide)

The synthesis of a thermoresponsive graft copolymer consisting of a maleic acid/vinyl acetate alternating copolymer backbone (MAc‐alt‐VA) and poly(N‐isopropylacrylamide) (PNIPAM) side chains is reported. Turbidimetric measurements in dilute aqueous solutions showed that no macroscopic phase separation takes place when the temperature is raised above the lower critical solution temperature (LCST) of PNIPAM, even at pH = 2. Moreover, in semi‐dilute aqueous solutions, a pronounced thermally induced viscosity increase (thermothickening) was observed. This thermoresponsive behaviour has been attributed to the interconnection of the hydrophilic MAc‐alt‐VA graft copolymer backbones by means of the hydrophobic PNIPAM side chain aggregates formed as the temperature increases above the LCST of this polymer. Copyright © 2004 Society of Chemical Industry     

Oxygen mass transport limitations at the cathode of polymer electrolyte membrane fuel cells

Oxygen transport across the cathode gas diffusion layer (GDL) in polymer electrolyte membrane (PEM) fuel cells was examined by varying the O₂/N₂ ratio and by varying the area of the GDL extending laterally from the gas flow channel under the bipolar plate (under the land). As the cathode is depleted of oxygen, the current density becomes limited by oxygen transport across the GDL. Oxygen depletion from O₂/N₂ mixtures limits catalyst utilization, especially under the land.The local current density with air fed PEM fuel cells falls to practically zero at lateral distances under the land more than 3 times the GDL thickness; on the other hand, catalyst utilization was not limited when the fuel cell cathode was fed with 100% oxygen. The ratio of GDL thickness to the extent of the land is thus critical to the effective utilization of the catalyst in an air fed PEM fuel cell. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Encapsulation of hydrophobic drugs in a copolymer: Glass transition behavior and miscibility evaluation

The knowledge of glass transition temperatures T_g in drug + polymer systems is indispensable for drug encapsulation. T_g values as a function of composition make possible the determination whether a given polymer is miscible or compatible with the drug and whether the polymer will provide release of the drug into organism within an acceptable rate range. We have used differential scanning calorimetry and Fourier‐transform infrared spectroscopy to evaluate miscibility in solid dispersions of the drugs carvedilol, itraconazole, nevirapine, and nimodipine in the pharmaceutical grade copolymer poly(vinyl pyrrolidone‐co‐vinyl acetate) (PLS‐630 Copovidone). Successful drug encapsulation is discussed in terms of thermophysical behavior (suppression of crystallization, negative excess volumes of mixing) and intermolecular interactions (concentrations of proton donating/accepting groups) in drug + polymer systems. Several equations were applied to the complex s‐shaped T_g(?) patterns obtained (? being the mass fraction of the drug). The best agreement of calculations with experiment is achieved using a recently proposed three‐parameter equation, symmetric with respect to the equal concentration of both components. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

A Radio Resource Management Framework for Multi-User Multi-Cell OFDMA Networks Based on Game Theory

This work proposes a radio resource management framework employing game theoretic concepts for orthogonal frequency division multiple access, the most prevalent multiple access technique for the next generation wireless networks. The subcarrier allocation problem is encountered as a combinatorial auction, where the base station auctions the subcarriers and the users bid for and buy bundles of subcarriers, aiming at minimising their required transmit power. Subsequently, each allocated subcarrier is loaded with a number of bits, decided by each user independently, and the power control process is set up as a non-cooperative game. Each user responds to the interference sensed in his environment and, through a best responses process, the game converges to the unique, Pareto optimal, Nash equilibrium. In order to guarantee convergence, a limit is imposed to the maximum modulation level for each subcarrier. Simulation results show that the auction algorithm follows closely the performance of the optimal algorithm, whereas it is of lower computational complexity and requires less feedback information. Similarly, the proposed distributed bit loading and power control scheme achieves lower transmit power per offered bit rate unit. However, the distributed nature of the algorithm results in lower total offered bit rate, because of the partial knowledge and exploitation of channel state information.     

Fair Radio Resource Allocation for MIMO OFDM-based Multicast Systems

This paper investigates the problem of resource allocation in a multiple-input multiple-output (MIMO) OFDM-based system, wherein multiple multicast groups exist. Multicasting is a transmission technique which enables a transmitter to communicate via a single wireless link with multiple receivers simultaneously. Moreover, the presence of multiple antennas in both transmitter and receiver enhances significantly the system spectral efficiency. MIMO technology along with multicasting offers major advantages to wireless systems. However, optimum exploitation of these technologies adds significant complexity to the system which makes very difficult any possible practical implementation. Another important issue of such systems is their capacity to ensure to all users a certain level of QoS. To that end, we propose a low complexity fair resource allocation algorithm aiming at ensuring a certain amount of resources to all users when multicasting is applied. Validation of the proposed solution is achieved through extensive simulation and it is compared to other multicast schemes for MIMO systems which exist in literature. Numerical results and complexity analysis show the feasibility of the proposed algorithm.