Seminars

The problem of finding a consistent truth assignment to all propositional variables in a formula, known as SAT problem, has been an interesting and difficult challenge. Indeed, SAT is at the heart of all computationally intractable problems. Many real world problems could be encoded as SAT problems. Thus finding an efficient solution for SAT has far reaching impact on computationally hard problems. This talk will begin with an overview of the main approaches for solving SAT problems. We will then focus on stochastic local search based methods. These methods have been shown to be highly effective for large size problems. We will present our recent results on clause weighting based local search, including an influential method that automatically learns about the structure of the problem, and efficiently exploit those structures to solve some of the difficult challenge problems.

Part 1:Quantum teleportation is one of the most important subjects in quantum information processing. We are improving the performance of continuous variable teleportation protocols and implementing several experiments involving the application of teleportation. In this talk I will outline my own research into the quantum teleportation of a single photon state. To achieve quantum teleportation, the bandwidth of the teleportation channel must be greater than the bandwidth of the input state. Consequently, current experiments in teleportation are performed with only narrow sideband frequency. In the presentation, I will describe our experimental approach to broaden the bandwidth of quantum teleportation.

Part 2: In this presentation I will outline our approach to achieve the challenging target of 10dB of quadrature squeezing at 860nm. In this application, mechanical stability of the experimental apparatus is of prime importance. I will introduce some of the approaches we have adopted to stabilize our system. Some of the techniques to be discussed include down sizing of the experimental setup, reduction of beam heights, installation of wind shields, and the development of new mirror mounts.

Mosaicing techniques are used to combine multiple images with different fields of view into a single image. Registration, or estimation of the relative motion between these images, is an important step in this process. This seminar examines practical issues in building mosaics from large numbers of images, such as video sequences, emphasising motion estimation. Issues addressed include image capture, images containing multiple objects with different motions, pixel interpolation, motion estimation techniques and image blending.

We now must investigate the atmosphere above astronomical sites to assess the complexity and expense of adaptive optic systems that would allow the new breed of Extremely Large Telescopes to achieve their grand potential. The Slope Detection and Ranging (SLODAR) technique that profiles the atmosphere above a telescope to determine the severity of the turbulence at numerous altitude layers, has been employed at Siding Spring Observatory and at the site for the Giant Magellan Telescope in Chile. I will describe the experiments and results of these studies, the ELT designs and the impact these results have in terms of future adaptive systems. I will also discuss how this technique is employed to the study of the human eye, and our current experiments using SLODAR in surveillance imaging.

This talk will discuss the evolving concept of imagery in the tactical battle space. Australian Defence Force (ADF) doctrine for intelligence, surveillance and reconnaissance (ISR) focuses on the deliberate planning process for static targets. Current operations in Iraq and Afghanistan have revealed the need, and the ADF has acquired some capability, for moving imagery data directly from ISR assets to war fighters in the tactical battle space, particularly for mobile targeting. The capabilities acquired by the ADF for moving imagery around the tactical battle space have tended to be localised solutions. The purpose of this study is to articulate possible options for using imagery information across tactical battle space networks and discuss the ADF force-level capability implications of each option.

Academic Applicant Seminars, IS and CS. 9:00-13:00.

Social groups form where individuals who are attracted to each other (usually by a common interest) interact and form clusters. These groups exist within structural networks that rely on the patterns of links between members through which communication and resource transfer occurs. The influence of individuals will impact on the emergent characteristics of a group, for example, its global opinion and collective behaviour. These characteristics form a part of the group culture. However, individuals join and leave groups, thus changing the system's dynamics. What impact does strategy development and decision making have on group dynamics? How do experience, capabilities, beliefs and values, and identity influence individual behaviour and actions? What do language and communication play in collective behaviour? This seminar does not propose to provide answers to these questions but to outline a possible research pathway that may lead to solutions.

Quantum Information Technologies, which include quantum computers and quantum key distribution, promise to revolutionise the ways in which we transmit and process information. The Quantum Electronics group in ITEE is a part of the global research community working towards the development of such technologies. In particular, the group works on the development of optical quantum computation architectures. This talk will be an introductory discussion into some of the key features of quantum mechanics that lead to the power of quantum information processing.

The goal of image registration is to automatically find the geometric transform which brings objects in the target and reference images into the best possible spatial alignment. There are many applications where the target and reference images have been captured using different devices or sensors which makes the automatic registration problem more difficult. In this talk I will describe a number of new information-theoretic approaches to the multi-sensor registration problem and show some examples of how these approaches can be used in medical and remote-sensing applications.

The use of an adaptive phase estimation technique to detect the optical phase of a coherent and more importantly a squeezed state of light has the potential to revolutionise the use of phase encoded light in a great many applications, including quantum computing and communications. Currently there are two baseline methods used for the detection of optical phase, homodyne and heterodyne or dual homodyne. Homodyne is very good but only if the phase of the signal is known to with p/2, this is not always practical in which case one must use heterodyne or dual homodyne detection. It has been shown that the detection of phase of an unknown signal using heterodyne detection is fundamentally limited by the contamination of the measurement with vacuum noise and its variance scales as 1/sqrt(2N) [1]. The use of adaptive feedback in a homodyne detection scheme allows one to estimate the phase to a greater level of accuracy with a reduction of the variance by an order of sqrt(2). Further to this Berry and Wiseman have shown that when applied to a non-classical squeezed state the scaling law is actually changed and the variance scales as (N)(5/8) [1]. This presentation covers the initial outcomes of an experimental proof of concept.

In recent years, a set of generally accepted measures (ranging from 'local' measures as node degrees, clustering coefficients, nearest neighbour degrees to 'global' measures such as distances, component size, betweenness centrality) has been developed that are well-suited to describe binary networks. Empirical networks, however, are often weighted networks. Moreover, in key examples like traffic networks, social networks or the trade network, link weights can span several orders of magnitude. It may be asked whether a binary description is suitable to capture essential system characteristics in these cases. In the talk I will give a short overview about generalizations of binary network measures to weighted networks. Advantages and shortcomings of the two main approaches discussed in the literature will be highlighted. Next, I will introduce a third approach, based on the idea of maximum flows. In a very natural way this approach provides an underlying principle from which generalizations of all binary network measures to weighted networks can be derived. The application of the weighted network measures to two real-world example networks, the international trade network and the passenger flow network between EU member countries, demonstrates that further insights about the systems' architectures can be gained this way.

Trapped ions are an attractive system for implementing quantum computing because of their extremely weak interactions with the environment, which allows the preservation of quantum coherence over many seconds. Techniques for small-scale ion-trap quantum computing have already been demonstrated and used in tests of quantum protocols. At Griffith, we have trapped and laser cooled crystals of a few Yb+ ions to be used as a quantum memory. In work toward ion-photon quantum interfacing, we have also shown that microfabricated phase Fresnel lenses can achieve diffraction-limited performance and subwavelength spot size in a configuration compatible with ion trapping. Finally, I discuss novel ion-trap quantum logic schemes that exploit the properties of ultrafast lasers.

Underwater acoustic communications systems suffer from low Transport Capacity, with 10kbps over 10km the current state-of-the-art. Multi-hop communication has been proposed as a means to boost the data rate and increase range, with absorption playing a key role in minimising inter-node interference. This absorption control on interference is crucial to maintain high data rates per node as the size of the Multi-hop network increases. The postulated absorption led control of interference has not been previously demonstrated. We have demonstrated that high frequencies, which suffer high absorption, do indeed provide a rapid decay in signal strength with range, and that this does lead to an even more rapid change in Signal-to-Interference Ratio (SIR) between two transmitters. A similarly steep decay and SIR transition is not apparent at lower frequencies. The reason this is so important is that if absorption can indeed be used to control inter-node interference, then Multi-hop networks can provide a means to step around the current capacity limits of underwater communication systems.

Metamaterials are artificial structures that produce interesting and counter-intuitive electromagnetic behaviour not possible with naturally occurring materials. Although such behaviours had been predicted decades earlier, it wasn't until about ten years ago that construction and experimental verification of a metamaterial structure was reported. Since then there has been a huge growth in interest in metamaterials, both in the research literature and popular press (eg. the technical possibility of making Harry Potter's Invisibility Cloak). In this seminar I will look at some of the ways to construct metamaterials and describe their properties. Of particular interest are the transmission line based metamaterials that overcome some of the fabrication and bandwidth issues of alternative structures.

We define a new class of spanning trees, called majority spanning trees, and cotrees, called majority cotrees, in directed graphs. We prove their existence in any digraph with non-negative weights on edges. We prove that there exists a majority spanning tree T of G such that G-T is a majority cotree. We show its applications in scheduling period transportation system by criterion of minimizing waiting times in connections, and in settling multiple debts. We also devise an algorithm for ranking players of a round robin tournament using the same structure in tournament digraph.

Organisations will increasingly move to exploit Web based content, data, architectures, frameworks, standards, technologies and tools to satisfy business requirements. This will mean in part the need for a network based approach to business applications where application data and components can be stored, transported, deployed, validated, marshalled, controlled, monitored, and governed over an end-point based network topology and operate robustly and dependably with syntactic, semantic and pragmatic consistency whilst ameliorating and amortising network affect on application performance. This presentation will outline some current and emerging architectures, frameworks and standards (for example Compound Document Format - CDF, Rich Web Application Backplane - RWAB, Semantic Web, State Chart XML - SCXML, XProc, etc) and how they can support distributed applications over the World Wide Web.

Malicious code is a threat to computer systems globally. The intrusion detection system (IDS) is one of the security defense tools for computer networks, and counters part of the malicious code threat. We briefly surveys the recent progression of multiagent intrusion detection systems. We also outline the present IDS research challenges and issues, and identify the position of IDS research in general. We present a novel architecture for an effective defense against malicious code attack, inspired by the human immune system. Two phases of program execution introduced: Adolescent and Mature. The first relies on malware profile, whereas the second relies on program profile.

This seminar will introduce a concept for Military Tactical Networks called MADNET - Mobile Ad Hoc and Disrupted Networks. Tactical military networks are not completely ad hoc nor are they a purely disrupted networks but rather they dynamically move through a spectrum of mobility ranging from relatively stable, almost enterprise like, to completely disrupted. This seminar will summarise current routing protocol research in the field of MANET and DTN, and discuss limitations of mobility modelling used to verify the protocols.

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