84,008 research outputs found
Conceptual techniques for reducing parasitic current gain of lateral pnp transistors
Two techniques have been conceptually proposed as possible means of reducing parasitic beta in lateral p-n-p transistors. One method uses a degenerate substrate and high concentration P /plus/ guard-ring diffusion, another places the base contact at the center of an annular ring structure
Quantum signatures of breather-breather interactions
The spectrum of the Quantum Discrete Nonlinear Schr\"odinger equation on a
periodic 1D lattice shows some interesting detailed band structure which may be
interpreted as the quantum signature of a two-breather interaction in the
classical case. We show that this fine structure can be interpreted using
degenerate perturbation theory.Comment: 4 pages, 4 fig
Designing and Building immersive education spaces using Project Wonderland: from pedagogy through to practice
This paper presents work on the JISC funded SIMiLLE project to build a culturally sensitive virtual world to support language learning. This builds on the MiRTLE project (funded by Sun Microsystems), which created a mixed-reality space for teaching and learning. The aim of the SIMiLLE project is to investigate the technical feasibility and pedagogical value of using virtual environments to provide a realistic socio-cultural setting and content for language learning interaction. The paper starts by providing some background information on the Wonderland platform and the MiRTLE project, and then outlines the requirements for SIMiLLE, and how these requirements will be supported through the use of a virtual world based on Project Wonderland. We then present our plans for the evaluation of the system, with a particular focus on the importance of incorporating pedagogy into the design of these systems, and how we can support good practice with the ever-growing use of 3D virtual environments in formalised education
The scaling properties of exchange and correlation holes of the valence shell of second row atoms
We study the exchange and correlation hole of the valence shell of second row
atoms using variational Monte Carlo techniques, especially correlated
estimates, and norm-conserving pseudopotentials. The well-known scaling of the
valence shell provides a tool to probe the behavior of exchange and correlation
as a functional of the density and thus test models of density functional
theory. The exchange hole shows an interesting competition between two scaling
forms -- one caused by self-interaction and another that is approximately
invariant under particle number, related to the known invariance of exchange
under uniform scaling to high density and constant particle number. The
correlation hole shows a scaling trend that is marked by the finite size of the
atom relative to the radius of the hole. Both trends are well captured in the
main by the Perdew-Burke-Ernzerhof generalized-gradient approximation model for
the exchange-correlation hole and energy.Comment: 18 pages, 8 figure
Teacher and student perceptions of the development of learner autonomy : a case study in the biological sciences
Biology teachers in a UK university expressed a majority view that student learning autonomy increases with progression through university. A minority suggested that pre-existing diversity in learning autonomy was more important and that individuals not cohorts differ in their learning autonomy. They suggested that personal experience prior to university and age were important and that mature students are more autonomous than 18-20 year olds. Our application of an autonomous learning scale (ALS) to four year-groups of biology students confirmed that the learning autonomy of students increases through their time at university but not that mature students are necessarily more autonomous than their younger peers. It was evident however that year of study explained relatively little
Freezing of Nonlinear Bloch Oscillations in the Generalized Discrete Nonlinear Schrodinger Equation
The dynamics in a nonlinear Schrodinger chain in an homogeneous electric
field is studied. We show that discrete translational invariant
integrability-breaking terms can freeze the Bloch nonlinear oscillations and
introduce new faster frequencies in their dynamics. These phenomena are studied
by direct numerical integration and through an adiabatic approximation. The
adiabatic approximation allows a description in terms of an effective potential
that greatly clarifies the phenomenon.Comment: LaTeX, 7 pages, 6 figures. Improved version to appear in Phys. Rev.
Functional programming framework for GRworkbench
The software tool GRworkbench is an ongoing project in visual, numerical
General Relativity at The Australian National University. Recently, the
numerical differential geometric engine of GRworkbench has been rewritten using
functional programming techniques. By allowing functions to be directly
represented as program variables in C++ code, the functional framework enables
the mathematical formalism of Differential Geometry to be more closely
reflected in GRworkbench . The powerful technique of `automatic
differentiation' has replaced numerical differentiation of the metric
components, resulting in more accurate derivatives and an order-of-magnitude
performance increase for operations relying on differentiation
Ignition and combustion characteristics of metallized propellants
Research designed to develop detailed knowledge of the secondary atomization and ignition characteristics of aluminum slurry propellants was started. These processes are studied because they are the controlling factors limiting the combustion efficiency of aluminum slurry propellants in rocket applications. A burner and spray rig system allowing the study of individual slurry droplets having diameters from about 10 to 100 microns was designed and fabricated. The burner generates a near uniform high temperature environment from the merging of 72 small laminar diffusion flames above a honeycomb matrix. This design permits essentially adiabatic operation over a wide range of stoichiometries without danger of flashback. A single particle sizing system and velocimeter also were designed and assembled. Light scattered from a focused laser beam is related to the particle (droplet) size, while the particle velocity is determined by its transit time through the focal volume. Light from the combustion of aluminum is also sensed to determine if ignition was achieved. These size and velocity measurements will allow the determination of disruption and ignition times as functions of drop sizes and ambient conditions
A peer-to-peer infrastructure for resilient web services
This work is funded by GR/M78403 “Supporting Internet Computation in Arbitrary Geographical Locations” and GR/R51872 “Reflective Application Framework for Distributed Architectures”, and by Nuffield Grant URB/01597/G “Peer-to-Peer Infrastructure for Autonomic Storage Architectures”This paper describes an infrastructure for the deployment and use of Web Services that are resilient to the failure of the nodes that host those services. The infrastructure presents a single interface that provides mechanisms for users to publish services and to find hosted services. The infrastructure supports the autonomic deployment of services and the brokerage of hosts on which services may be deployed. Once deployed, services are autonomically managed in a number of aspects including load balancing, availability, failure detection and recovery, and lifetime management. Services are published and deployed with associated metadata describing the service type. This same metadata may be used subsequently by interested parties to discover services. The infrastructure uses peer-to-peer (P2P) overlay technologies to abstract over the underlying network to deploy and locate instances of those services. It takes advantage of the P2P network to replicate directory services used to locate service instances (for using a service), Service Hosts (for deployment of services) and Autonomic Managers which manage the deployed services. The P2P overlay network is itself constructed using novel Web Services-based middleware and a variation of the Chord P2P protocol, which is self-managing.Postprin
- …