999 research outputs found

    Constructing continuum many countable, primitive, unbalanced digraphs

    Get PDF
    AbstractWe construct continuum many non-isomorphic countable digraphs which are highly arc transitive, have finite out-valency and infinite in-valency, and whose automorphism groups are primitive

    Online educational counselling for students with special needs: Building rapport

    Get PDF
    This paper reports the findings from a study that investigated the effects of providing online counselling for undergraduate students with long‐term health problems. Issues associated with learning at a distance for such students include fatigue, manual dexterity, academic and social isolation, together with a need for better interactive communication with support agencies (Debenham, 1996a). The results of a feasibility study undertaken in 1996 suggested that for students with special needs personal rapport with their educational counsellor is considered important for problems to be aired and addressed (Debenham, 1998a). This raises interesting questions relating to how such rapport can be developed using computer‐mediated communication (CMC). Participants in the study reported appreciation of a small amount of informal contact with the counsellor in a closed peer‐group conference; this conference is described in Debenham (1996b). Building on this finding, a main study was undertaken which was modified by the addition of a counselling topic ‐ a ‘Virtual Study’ for the counsellor ‐ within this conference area (Debenham, 1998b). The counsellor was encouraged to participate informally in the other student‐led topics. This added a group dimension to the study. The results are encouraging: increased levels of motivation and enjoyment of the study process were reported by more than three‐quarters of the sample and in the degree of autonomy by more than half the sample. These findings throw light on the support of students with special needs and also contribute to the development of knowledge in the wider fields of academic advising and the use of CMC in distance education

    Crystallisation of PFA glasses

    Get PDF
    Bibliography: leaves 79-81.Glasses with various compositions, falling in the CaO-AI20rSi02 and MgO-CaOAI20rSi02 systems were made, using pulverised fuel ash and silica, hydrated lime, kaolin and magnesium carbonate. Titania or ferric oxide and chromia were used as nucleants. Various crystallisation heat treatments were carried out and the nucleation and crystallisation behaviour was studied. A minimum MgO:CaO was found to be necessary for bulk nucleation to occur. The activation energy for viscous flow decreased with increased MgO:CaO ratios. This was accompanied by an increase in the surface crystal growth rates and a decrease in the activation energy for surface crystal growth. Titania also lowered the activation energies for viscous flow and surface crystal growth and caused an increase in the surface crystal growth rates

    Risks of Offline Verify PIN on Contactless Cards

    Get PDF
    Contactless card payments are being introduced around the world al- lowing customers to use a card to pay for small purchases by simply placing the card onto the Point of Sale terminal. Contactless transactions do not require veri- fication of the cardholder’s PIN. However our research has found the redundant verify PIN functionality is present on the most commonly issued contactless credit and debit cards currently in circulation in the UK. This paper presents a plausible attack scenario which exploits contactless verify PIN to give unlimited attempts to guess the cardholder’s PIN without their knowledge. It also gives experimental data to demonstrate the practical viability of the attack as well as references to support our argument that contactless verify PIN is redundant functionality which compromises the security of payment cards and the cardholder
    • 

    corecore