C++QED: An object-oriented framework for wave-function simulations of cavity QED systems

We present a framework for efficiently performing Monte Carlo wave-function simulations in cavity QED with moving particles. It relies heavily on the object-oriented programming paradigm as realised in C++, and is extensible and applicable for simulating open interacting quantum dynamics in general. The user is provided with a number of ``elements'', eg pumped moving particles, pumped lossy cavity modes, and various interactions to compose complex interacting systems, which contain several particles moving in electromagnetic fields of various configurations, and perform wave-function simulations on such systems. A number of tools are provided to facilitate the implementation of new elements.Comment: 31 pages, 8 figures, 3 table

CFD simulation of underground coal dust explosions and active explosion barriers

Computational fluid dynamics (CFD) is being applied to the study of coal dust explosions and their suppression in underground coal mines. As part of an ACARP funded project to develop a practical active explosion barrier, CFD is being used to simulate the explosion dynamics in simple mine roadways before examining the design requirements for an active explosion barrier. Results of these simulations will be used to develop the specifications for a prototype active explosion barrier with a reduced requirement for large scale testing. Results to-date are very encouraging with validation of the model behaviour against a range of explosion conditions in the Simtars Siwek 20 L chamber and the CSIR’s 200 m explosion tunnel in South Africa. This paper presents the results of a number of simulations with comparison against data obtained from the 200 m tunnel and preliminary modeling of an active barrier. This modeling provides an opportunity to examine explosion dynamics at a level not seen before

Scaffolding asynchronous communication

This research identifies and studies the techniques and strategies used by New Zealand tertiary tutors in the process of encouraging participation, and ultimately learning, when using online asynchronous discussion forums. The last decade has seen considerable growth in online learning and the discussion forum now features as a mainstream teaching tool in both fully online courses and in blended delivery. Of interest are the strategies tutors use in online discussion forums: exactly how do tutors encourage an online class to participate and engage in meaningful discourse in a textual asynchronous communication medium? Twelve New Zealand tertiary tutors were interviewed in a semi-structured manner, gathering both demographic data and data from open-ended questions. The openended questions were designed to ascertain the tutors’ perceptions about the pedagogical considerations of online learning, the barriers students may face and the techniques the tutors use to compensate for these barriers. The results were analysed using qualitative methods, summarised and discussed. The study shows that a number of the tutors interviewed used a range of strategies across both the affective and cognitive domains, and these tutors were aware of which barriers their strategies are targeting. Where a narrow selection of strategies was used it was apparent that some of the barriers to participation were not being addressed

All-optical signal regeneration using parametric soliton switch

A photonic switch in the form of a logical and gate within a planar waveguide was proposed. Investigations by numerical simulation were performed with two very interesting results. Firstly, the switch displays a highly digital response with respect to perturbations in the first two parameters, and secondly the switch continues to perform well with relative energy imbalances of up to a factor of 2. Thus not only could this switch be used very effectively as an all-optical and logic gate but by combining a signal with a well timed clock pulse-train, time domain multiplexing, demultiplexing, and signal regeneration in both pulse timing and pulse energy can be performed

Xmds: eXtensible multi-dimensional simulator

A software package that efficiently solves a comprehensive range of problems based on coupled complex nonlinear stochastic ODEs and PDEs is outlined. Its input and output syntax is formulated as a subset of XML, thus making a step towards a standard for specifying numerical simulations

Parametric signal regeneration

An analysis of an all-optical digital signal regeneration device concept using non-degenerate parametric interaction in one-dimensional waveguide was performed. The analysis was carried out in terms of re-amplification, re-timing and re-shaping of time domain multiplexed signals. In order to determine the input output relationship performance parameters were identified. It was found that output energy and pulse width were related to input energy and timing

Digital response in an all optical AND gate using parametric (x^(2) solitons

The main problem with optical logic is that the operation of a logic gate that works on two inputs is essentially a nonlinear process, whereas electromagnetic waves in most media are solutions to the linear Maxwell equations; in most dielectrics light does not interact with itself. However, in recent years there has been considerable advances in the theory and manufacture of nonlinear optical media, which now opens a new and exciting range of possibilities for implementing all optical logic circuits. One such possibility is the implementation of an all-optical AND gate as proposed by Drummond et al. (1999). In this method the two optical inputs are collided noncollinearly in a dispersive parametric planar waveguide. Consider firstly type II interaction in which the pulses have orthogonal polarizations. If only one pulse at a time is injected into the waveguide then it simply disperses. Whereas if two pulses arrive simultaneously then when they collide a phase-matched second harmonic is generated that traps the original two fundamentals, forming a 2+1D spatiotemporal soliton, which propagates stably towards the logic true output. Finally, it is also apparent that when no pulse is present on either input then no output will be generated. In this fashion AND gate logic operation is achieved. For such 2+1D solitons to form the basic requirements are anomalous dispersion and (nearly) matched group velocities at the fundamental and second harmonic frequencie