A Key Establishment Scheme for Mobile Wireless Sensor Networks Using Post-Deployment Knowledge

Establishment of pairwise keys between sensor nodes in a sensor network is a difficult problem due to resource limitations of sensor nodes as well as vulnerability to physical captures of sensor nodes by the enemy. Public-key cryptosystems are not much suited for most resource-constrained sensor networks. Recently, elliptic curve cryptographic techniques show that public key cryptosystem is also feasible for resource-constrained sensor networks. However, most researchers accept that the symmetric key cryptosystems are viable options for resource-constrained sensor networks. In this paper, we first develop a basic principle to address the key pre-distribution problem in mobile sensor networks. Then, using this developed basic principle, we propose a scheme which takes the advantage of the post-deployment knowledge. Our scheme is a modified version of the key prioritization technique proposed by Liu and Ning. Our improved scheme provides reasonable network connectivity and security. Moreover, the proposed scheme works for any deployment topology.Comment: Published in International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.4, July 201

The educational psychologist as a pedagogue for pupils with social, emotional and behavioural difficulties

This thesis reflects my personal and professional journey from teacher to educational psychologist through significant periods in the education of children with Social Emotional and Behavioural Difficulties (SEBDs) in the UK. It also draws of on lessons learnt from my experience working in North America in the early years of my career. The main aims of my research were to: (1) Appraise the contribution an educational psychologist could make in assessing the learning potential of children and young people with SEBDs, and (2) Consider the „added value‟ that an educational psychologist might bring to enable these children as better learners and teachers as better teachers of children with SEBDs. 45 Children and young people with Social Emotional Behavioural Difficulties and their parents and teachers participated in the research. A mixed methods approach was employed to undertake three related case studies and a reflexive and narrative analysis was employed. Main outcomes of the research were (i) SEBDs were almost always accompanied by often unrecognised learning difficulties; (ii) A cognitive assessment by an educational psychologist had an added value in understanding the needs of the child; (iii) When parents and teachers of children who participated in an especially designed intervention, it changed their views of their children‟s behaviours. They reported significant improvement in their children‟s social skills and behaviour. I conclude the thesis by considering the implications of findings for the benefit of children with SEBDs. It is crucial that teachers identify and assess learning difficulties in all children and young people and clearly differentiate these from matters of and interventions for behaviour difficulties. Teachers and parents can be empowered to deal with their children‟s behavioural difficulties by involving the Educational Psychologist as a pedagogue, sitting as he or she does at the crossroads of education and psychology

Powder Deposition and Sintering for a Two-Powder Approach to Solid Freeform Fabrication

A two-powder approach is presented where Fused Deposition modeling (FDM) is used to create a thin shell in the shape of the part to be fabricated. The shell is filled with powder of the part material and surrounded by a support powder that has a high sintering temperature. Upon compressing and sintering the shelVpowder system in a uniaxial hot press, the polymer shell burns out and the support powder compresses the part powder. The part powder consolidates into the desired part while the support material remains in powder form and can be easily removed. This paper presents results ofinitial experimental studies.Mechanical Engineerin

Investigating Unipolar Switching in Niobium Oxide Resistive Switches: Correlating Quantized Conductance and Mechanism

Memory devices based on resistive switching (RS) have not been fully realised due to lack of understanding of the underlying switching mechanisms. Nature of ion transport responsible for switching and growth of conducting filament in transition metal oxide based RS devices is still in debate. Here, we investigated the mechanism in Niobium oxide based RS devices, which shows unipolar switching with high ON/OFF ratio, good endurance cycles and high retention times. We controlled the boundary conditions between low-conductance insulating and a high-conductance metallic state where conducting filament (CF) can form atomic point contact and exhibit quantized conductance behaviour. Based on the statistics generated from quantized steps data, we demonstrated that the CF is growing atom by atom with the applied voltage sweeps. We also observed stable quantized states, which can be utilized in multistate switching