Control of a Robotic Wheelchair Using Recurrent Networks

This paper describes an adaptive neural control system for governing the movements of a robotic wheelchair. It presents a new model of recurrent neural network based on a RBF architecture and combining in its architecture local recurrence and synaptic connections with FIR filters. This model is used in two different control architectures to command the movements of a robotic wheelchair. The training equations and the stability conditions of the control system are obtained. Practical tests show that the results achieved using the proposed method are better than those obtained using PID controllers or other recurrent neural networks models     

Consciousness, Agents and the Knowledge Game

This paper has three goals. The first is to introduce the “knowledge game”, a new, simple and yet powerful tool for analysing some intriguing philosophical questions. The second is to apply the knowledge game as an informative test to discriminate between conscious (human) and conscious-less agents (zombies and robots), depending on which version of the game they can win. And the third is to use a version of the knowledge game to provide an answer to Dretske’s question “how do you know you are not a zombie?”.     

A unified signal transition graph model for asynchronous control circuit synthesis

Characterization of the behavior of an asynchronous system depending on the delay of components and wires is a major task facing designers. Some of these delays are outside the designer's control, and in practice may have to be assumed unbounded. The existing literature offers a number of analysis and specification models, but lacks a unified framework to verify directly if the circuit specification admits a correct implementation under these hypotheses.Our aim is to fill exactly this gap, offering both low-level (analysis-oriented) and high-level (specification-oriented) models for asynchronous circuits and the environment where they operate, together with strong equivalence results between the properties at the two levels. One interesting side result is the precise characterization of classical static and dynamic hazards in terms of our model. Consequently the designer can check the specification and directly decide if the behavior of any implementation will depend, e.g., on the delays of the signals described by such specification.We also outline a design methodology based on our models, pointing out how they can be used to select appropriate high and low-level models depending on the desired characteristics of the system.     

Experimental teleradiology. Novel telematics services using image processing, hypermedia and remote cooperation to improve image-based medical decision making

Various reports draw attention to the deficiency of services available for critically ill children. In December 1993 the British Paediatric Association published a report by a multidisciplinary working party on intensive care. The Minister of Health has apparently promised to act on the recommendations the working party made. In fact, purchasers are being encouraged to act and ask questions about the provision of paediatric intensive care--but no extra funding is available to provide it. However, this will all take time and until more resources are available children are still being cared for on adult intensive care units by nurses who may not be experienced in caring for sick children. One of the main areas of concern nurses have when caring for children is the physiological differences between an adult and a child. This paper is designed to assist in identifying the differences and consequent nursing implications. In an attempt to prioritize the nursing care a systems/modified model has been used over 2 papers. The review of the systems demonstrates the differences between adults and children and, where possible, highlights the nursing care and medical treatment a child requires. All aspects of care have been included as well as the psychological problems (see Part 2 which will be published in the next issue) encountered by the family of a critically ill child. Where possible easy reference tables have been included and the author hopes to introduce the package into the existing orientation programme for established staff and staff new to the unit in the hopes of decreasing the stress when a child is admitted. Paediatric resuscitation has not been covered intentionally, as the information on the physiological differences seemed to grow like 'Jack's beanstalk'. Therefore, a flow chart for basic and advanced life support is included as an appendix in Part I. It is hoped this will stimulate readers' interest for more in-depth study.     

Supply Estimation Using Coevolutionary Genetic Algorithms in the Spanish Electrical Market

The price of electrical energy in Spain has not been regulated by the government since 1998, but determined by the supply from the generators in a competitive market, the so-called electrical pool. A genetic method for analyzing data from this new market is presented in this paper. The eventual objective is to determine the individual supply curves of the competitive agents. Adopting the point of view of the game theory, different genetic algorithm configurations using coevolutionary and non-coevolutionary strategies combined with scalar and multi-objective fitness are compared. The results obtained are the first step toward solving the induction of the optimal individual strategies into the Spanish electrical market from data in terms of perfect oligopolistic behavior.     

The “presence of others” in a virtual environment: different collaborative modalities with hybrid resources

The purpose of this study is to see in which forms and under which conditions social presence turns into collaboration. Eight couples were asked to find some objects in a virtual environment in which collaboration was allowed but not mandatory. The qualitative analysis of the video recordings shows that all participants resorted to collaboration in forms that were justified by the requirements of the task, the environmental affordances and the different expertise.

Synthesis and characterization of poly(L-lactic acid) membranes: Studies in vivo and in vitro

The use of biodegradable polyesters as temporary structural supports in the recuperation of damaged live tissue is a promising area of research. Poly(L-lactic acid) (PLLA) membranes can act as a support for cell fixation and growth or as a barrier against soft tissues invasion in recuperating bone tissues. In this work, five different types of PLLA membranes, which varied in their polymer–solvent ratio and their content of plasticizer were studied. For the study in vivo, 6 mm diameter disks were inserted subcutaneously in the dorsal region of 15 Wistar rats, and the reactions on rats were studied 15 days later. In another series of experiments the samples were immersed in phosphate buffer, pH 7.4 at 37 °C, for 30 days. Membranes without plasticizer were morphologically dense and did not allow cell invasion nor tissue adherence, in contrast to membranes with plasticizer. While porosity enhanced cell fixation and growth, it made the membrane more fragile mechanically when compared to membranes without pores.     

Use of triethylcitrate plasticizer in the production of poly-L-lactic acid implants with different degradation times

Bioabsorbable materials have been widely used in the repair of damaged tissue as well as in the controlled release of drugs and as a supports for cultured cells. The degradation time of poly-L-(lactic acid) (PLLA) may be controlled by altering the polymer porosity through the addition of the plasticizer triethylcitrate. This in turn influences the extent cellular infiltration. In this study, we examined the degradation of PLLA membranes containing different concentrations of plasticizer. PLLA discs were implanted subcutaneouly in rats and withdrawn 2, 14 and 60 days after implantation. The samples were processed for light microscopy and scanning electron microscopy (SEM). Polymer degradation was proportional to the concentration of plasticizer, indicating that triethylcitrate could affect the degradation time of the implants, without damaging the polymer biocompatibility.