CECS Upcoming Seminars

Thursday 04 March, 2010 Sandun Kodituwakku - TBA

2010-03-04 11:00:00

11:00:00 - 12:00:00 - RSISE Seminar Room, ... Applied Signal Processing Series

TBA

Thursday 25 February, 2010 Kim Blackmore - TBA

2010-02-25 11:00:00

11:00:00 - 12:00:00 - RSISE Seminar Room, ... Applied Signal Processing Series

TBA

Thursday 04 February, 2010 Oday Jerew - TBA

2010-02-04 11:00:00

11:00:00 - 12:00:00 - RSISE Seminar Room, ... Applied Signal Processing Series

TBA

Thursday 28 January, 2010 Chris J Baker - TBA

2010-01-28 11:00:00

11:00:00 - 12:00:00 - RSISE Seminar Room, ... Applied Signal Processing Series

TBA

Thursday 17 December, 2009 Thushara Abhayapala - TBA

2009-12-17 11:00:00

11:00:00 - 12:00:00 - RSISE Seminar Room, ... Applied Signal Processing Series

TBA

Monday 14 December, 2009 Prof. Anthony Ephremides - Cooperation at the Network Level

2009-12-14 11:00:00

11:00:00 - 12:00:00 - RSISE Seminar Room, ... CECS Seminar Series

The concept of cooperative transmissions in a wireless network evolved from the notion of the relay channel and the MIMO technology. Most of the work to date has focused on physical layer techniques (such as decode-and-forward and the like) and aimed at characterizing the source-to-destination Information-theoretic Capacity.We take a different view and exploit the possibility of relaying in a cognitive fashion. That is, we sense unused resources (time-slots and/or frequency bamds) and make opportunistic use of these resources for relaying. We consider packets and slots rather than bits and seconds and thus our approach focuses on computing throughput, rather than capacity. In fact, we consider the realistic and practical case of finite delays, and, hence, bursty source traffic; thus we focus on the "stable throughput" region that can be achieved in a network with or without relaying. We find that significant improvements can be achieved if such cooperative/cognitive methods are used. And in fact we also consider superposing on these methods the more familiar physical layer schemes (such as combining, decode-and-forward, etc) and show that we can achieve, as expected, even further gains.We then look at cooperative routing in sensor networks (a totally different concept of cooperation, again at the network level) and identify some remarkable consequences in that case.

These novel ideas and methods are the beginning of what we call "cooperation at the network level"; the potential exists that, through such cooperation, far-reaching implications may follow with regard to achievable transmission rates under bursty traffic conditions.

Thursday 03 December, 2009 Yan Jennifer Wu - Multizone 2D Soundfield Reproduction Via Spatial Band Stop Filters

2009-12-03 11:00:00

11:00:00 - 12:00:00 - RSISE Seminar Room, ... Applied Signal Processing Series

Any attempt to create multiple independent soundfields in separate zones over an extended region of open space results in unintended interference in a given zones from other zones. For a multizone soundfield system, there are undesirable effects inherently produced on one zone which are caused by the lower order terms from the other zones. In this seminar, we present a spatial band stop filters to suppress interzone interference in the regions of interests and pass the desired soundfields with no distortion. This is achieved by using the higher order spatial harmonics of one zone to cancel the undesirable effects of the lower order harmonics of the same zone on the other zones. We illustrate the work by designing and simulating a 2D two-zone soundfield.

Friday 27 November, 2009 Dr. Sergej Celikovsky - Nonlinear techniques for the Acrobot tracking with application to robot walking

2009-11-27 11:00:00

11:00:00 - 12:00:00 - RSISE Seminar Room, ... Systems and Control Series

This talk aims to compare the performance of various techniques for the stabilization of the error dynamics of the Acrobot's walking like reference trajectory. Both the walking reference planning and the tracking feedback design are based on the Acrobot's model partial exact feedback linearization of order 3. Namely, such an exact system transformation leads to an almost linear system where error dynamics along trajectory to be tracked is a 4 dimensionallinear time varying system having 3 time varying entries only, the remaining entries are either zero or equal to one.

Three techniques to stabilize asymptotically such an error dynamics are presented and compared. All of them are based on the robust control approaches viewing the abovementioned time-dependent terms as some partially unknown disturbances. First technique combines high-gain feedback with Lyapunovs analysis, the latter one enables to obtain some reasonable gain values, yet resulting in an unrealistically large actuator torque. The second technique relies on the fact that the desirable exponentially stable tracking can be obtained by solving quadratic stability of a linear system with polytopic uncertainty. To do so, LMI methods are engaged to solve this problem numerically. The results of this careful analysis are shown to be a significant improvement of previously known approaches, especially in the case of nonrectangular convex polytopic uncertainty set. Here, the advantage is taken of the fact that "uncertainty" is, in fact, a triple of the known scalar time functions, so that one can find significantly smaller bounding convex set than just a large rectangular box. The last technique uses the time-dependent transformation of the error dynamics resulting in much better results when the high-gain approach is applied. Similarly as with the first technique, the corresponding results are in a closed form, rather than in a numerical one. Again, the advantage is taken of the fact that the time dependent error dynamics parameters are, in fact, known and differentiable.

Numerical simulations and animations of the Acrobot walking based on all above mentioned techniques will be demonstated as well. Finally, some outlooks will be presented to extend these ideas to the walking design for the general n-link systems with n-1 actuators, underactuated at the pivot point.

Thursday 26 November, 2009 Ullrich Hustadt - Reasoning in Monodic First-Order Temporal Logic

2009-11-26 16:00:00

16:00:00 - 17:00:00 - NICTA - 7 London Cir... NICTA LC Seminar

Temporal logics have long been considered as appropriate formal languages for specifyingimportant computational properties of hardware and software systems. However, while variouspropositional temporal logics have been used very successfully in this context, the same hasnot been true to the same extent for first-order temporal logic. One reason is that first-ordertemporal logic is not even semi-decidable, which limits its usefulness for the purpose ofautomatic verification. A prominent fragment of first-order temporal logic which has thecompleteness property is the monodic fragment. Besides completeness, the monodic fragmentenjoys a number of other beneficial properties, e.g. the existence of non-trivial decidablesubclasses, automated deduction, etc. Moreover, reasoning in other formalisms, like temporallogics of knowledge, can be reduced to reasoning in the monodic fragment.

In this talk I will give an overview of the monodic fragment of first-order temporal logicand of resolution-based calculi for reasoning in this logic. The main focus of the talk willbe the problems associated with turning such calculi into practical theorem provers andhow these can be solved.

Thursday 26 November, 2009 Bob Edwards - Yubikey Authentication in a Mid-sized Organisation

2009-11-26 16:00:00

16:00:00 - 17:00:00 - CSIT Seminar Room, N... DCS Seminar Series

The Swedish company Yubico manufacture the Yubikey One-Time-Password (OTP) USB device and have released all protocol and other relevant details which makes the Yubikey particularly attractive as a low-cost and non-vendor-lock-in authentication solution.

Bob will demonstrate the Yubikey for the purposes of secure authentication on untrusted end-user systems (eg. PCs at an Internet Cafe or a friends house etc.) and will discuss some of the advantages as well as some of the weaknesses of the Yubikey system. He will then go on to describe the development of an authentication server written in C and based on a PostgreSQL database and implementing LDAP and other authentication protocols. This will include some technical details of how to use the APIs for connection to the database, parsing the ASN1 LDAP queries, dealing with denial-of-service attacks etc. He will also discuss some of the code he has written to implement the Yubikey protocol on devices with no USB port (eg. a PDA or mobile phone etc.).

This talk is a prelude to a paper Bob will present at the Linux Conference of Australia in 2010 (LCA2010) in Wellington, NZ in January.

Thursday 26 November, 2009 Faisal Mufti - 3D Time-of-flight camera and radiometric range modelling

2009-11-26 16:00:00

16:00:00 - 17:00:00 - RSISE Seminar Room, ... Computer Vision and Robotics Series

In recent years, the demand for 3D vision systems has increased in several fields such as; detection and recognition, motion modelling, 3D environment reconstruction and tracking. This has resulted in an increase in efforts to develop range image technology and especially Time-of-Flight (TOF) cameras/imaging devices. TOF imaging devices provide distance measurements between a sensor and an observed target. These devices emit a modulated electromagnetic signal and measure the phase offset of the reflected signal to obtain pixel-by-pixel range estimation over a full image array. These devices have an advantage over traditional range data sensors such as LIDAR sensors due to their capability to provide range data over a full image array at video frame rate.

This talk would cover the key issue of reliability of range measurement from received signal in TOF cameras. The quality of the measurement of these sensors depends heavily on signal-to-noise ratio (SNR) of the incoming signal and the subsequent processing algorithms. I would provide an explicit statistical noise modelling of TOF measurements. This analysis combined with radiometric reflectance analysis of TOF camera allows for range error classification considering scene geometry for Lambertian surfaces.

Thursday 26 November, 2009 Parastoo Sadeghi - On Coding for Cooperative Data Exchange

2009-11-26 11:00:00

11:00:00 - 12:00:00 - RSISE Seminar Room, ... Applied Signal Processing Series

We consider the problem of data exchange by a group of clients. In this problemeach client holds a set of packets and needs to obtain all the packets held by the other clients. Each of the clients can broadcast the packets in its possession (or a combination thereof) via a noiseless broadcast channel of capacity one packet per transmission. The goal is to minimize the total number of transmissions needed tosatisfy the demands of all the clients, assuming that they can cooperate with each other and are fully aware of the packet sets available to other clients. This problem arises in many practical settings, such as peer-to-peer systems and wireless data broadcast. In this talk, we establish a number of upper and lower bounds on the optimal number of transmissions and present an efficient algorithm with provable performance guarantees. The effectiveness of our algorithms is established through numerical simulations. We discuss directions for future research.

Thursday 26 November, 2009 Dr Rui Zhang - The V*-Diagram, a Query Dependent Approach to Moving Nearest Neighbor Queries

2009-11-26 11:00:00

11:00:00 - 12:00:00 - CSIT Seminar Room, N... DCS Seminar Series

The moving k nearest neighbor (MkNN) query continuously finds the knearest neighbors of a moving query point. MkNN queries can beefficiently processed through the use of safe regions. In general, asafe region is a region within which the query point can move withoutchanging the query answer. This talk presents an incrementalsafe-region-based technique for answering MkNN queries, called theV*-Diagram, as well as analysis and evaluation of its associatedalgorithm, V*-kNN. Traditional safe-region approaches compute a saferegion based on the data objects but independent of the query location.Our approach exploits the knowledge of the query location and theboundary of the search space in addition to the data objects. As aresult, V*-kNN has much smaller I/O and computation costs than existingmethods. We further provide cost models to estimate the number of dataaccesses for V*-kNN and a competitive technique, RIS-kNN. The V*-Diagramand V*-kNN are also applicable to the domain of spatial networks and wepresent algorithms to construct a spatial-network V*-Diagram. Ourexperimental study shows that V*-kNN significantly outperforms thecompetitive techniques and verifies the accuracy of the cost models. Theresults of this work are published in VLDB'08 conference and VLDB Journal.