IT Technical Report Series for the Year 2004

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Technical Reports

A pipeline for automatically processing and analysing archival images from multiple instruments

Technical Report No. : NUIG-IT-261104
By : S. O Tuairisg, A. Golden, R. Butler, A. Shearer, B. Voisin

To take advantage of the recent upsurge in astrophysical research applications of grid technologies coupled with the increase in temporal and spatial coverage afforded to us by dedicated all-sky surveys and on-line data archives, we have developed an automated image reduction and analysis pipeline for a number of different astronomical instruments. The primary science goal of the project is in the study of long-term optical variability of brown dwarfs, although it can be tailored to suit many varied astrophysical phenomena. The pipeline complements Querator, the custom search-engine which accesses the astronomical image archives based at the ST-ECF/ESO centre in Garching, Germany. To increase our dataset we complement the reduction and analysis of WFI (Wide Field Imager, mounted on the 2.2-m MPG/ESO telescope at La Silla) archival images with the analysis of pre-reduced co-spatial HST/WFPC2 images and near infrared images from the DENIS archive. Our pipeline includes CCD-image reduction, registration, astrometry, photometry, and image matching stages. We present sample results of all stages of the pipeline and describe how we overcome such problems as missing or incorrect image meta-data, interference fringing, poor image calibration files etc. The pipeline was written using tasks contained in the IRAF environment, linked together with Unix Shell Scripts and Perl, and the image reduction and analysis is performed using a 40-processor Origin SGI 3800 based at NUI, Galway.

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An Evaluation and Simulation of VoIP Testbed Conditions Resulting in Additional Mouth-to-Ear Delays

Technical Report No. : NUIG-IT-231104
By : Brian Furey, Hugh Melvin

The International Telecommunications Union (ITU-T) recommendation- G.114 specifies that mouth-to-ear (M2E) delays should not exceed 150 msecs. M2E delays are generally more significant in Voice over IP (VoIP) calls than in the traditional Plain Old Telephone System (POTS). M2E delays include intermediate network delays and a range of sender and receiver delays within endpoints. The objective of this paper is to highlight two less well-known endpoint delays that contribute to the overall M2E delay in VoIP calls. The first is caused by the existence of different clock speeds (or skew) between the sender and receiver soundcards. The second is caused by a mismatch between sound card driver design and VoIP application design. Firstly, the impact of these two delays on overall VoIP M2E delays are demonstrated through test results obtained from a VoIP testbed. A simulator is then built to simulate the performance of the two delay conditions under different user-configurable scenarios. The results of these simulations accurately predict the performance of the two conditions in a real environment and thus can be used to predict their impact under various endpoint configurations.

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WebCom-G: Implementing an astronomical data analysis pipeline on a Grid-type infrastructure

Technical Report No. : NUIG-IT-251104
By : Seathrun O Tuairisg, Michael Browne, John Cuniffe, Andrew Shearer, John Morrison, Keith Power

The recent upsurge in astrophysical research applications of grid technologies, coupled with the increase in temporal and spatial sky-coverage by dedicated all-sky surveys and on-line data archives, have afforded us the opportunity to develop an automated image reduction and analysis pipeline. Written using Python and Pyraf, the Python implementation of the IRAF package, this has been tailored to act on data from a number of different astronomical instruments. By exploiting inherent parallelisms within the pipeline, we have augmented this project with the ability to be run over a network of computers. Of particular interest to us is an investigation into the latency penalties in running the pipeline within a cluster and between two clusters. We have used a condensed graph programming model, the Grid middle-ware solution WebCom-G, to realize Grid-implementation. We describe how a re-organisation of such an astronomical image analysis structure can improve operational efficiency and show how such a paradigm can be extended to other applications of image processing. It is intended to use this project as a test bed for eventually running our image processing applications over a grid network of computers, with a view toward possible implementation as part of a virtual observatory infrastructure.

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Parallelization of MATLAB for Euro50 integrated modelling

Technical Report No. : NUIG-IT-291104
By : M. Browne, T. Andersen, A. Enmark, D. Moraru, A. Shearer

MATLAB and its companion product Simulink are commonly used tools in systems modelling and other scientificdisciplines. A cross-disciplinary integrated MATLAB model is used to study the overall performance of the proposed 50m optical and infrared telescope, Euro50. However the computational requirements of this kind of end-to-endsimulation of the telescopeÕs behaviour, exceeds the capability of an individual contemporary Personal Computer. By parallelizing the model, primarily on a functional basis, it can be implemented across a Beowulf cluster of generic PCs.This requires MATLAB to distribute in some way data and calculations to the cluster nodes and combine completed results. There have been a number of attempts to produce toolkits to allow MATLAB to be used in a parallel fashion.They have used a variety of techniques. Here we present findings from using some of these toolkits and proposed advances.

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A Parallel Integrated Model of the Euro50

Technical Report No. : NUIG-IT-301104
By : Torben Andersen, Anita Enmark, Dan Moraru, Chengyu Fan, Mette Owner-Petersen, Holger Riewaldt, Mich

The Euro50 is an astronomical extremely large telescope for optical and infrared wavelength with a 50 m primary mirror. The telescope will have an elaborate control system ("live optics") to correct for atmospheric and telescope aberrations. To study and predict performance of the complete telescope system, an integrated model combining the structural model of the telescope, optics models, the control systems, and the adaptive optics has been established. Wind is taken into account on the basis of wind tunnel measurements and computer fluid dynamics calculations. Atmospheric aberrations are included using a seven-layer atmosphere model. The integrated model is written in Matlab and is run on a cluster computer to achieve acceptable execution times. Dedicated ordinary differential equation solvers have been written and a special toolkit for communication between Matlab processes on different nodes of the cluster computer has been set up. Preliminary results from the complete integrated model, including adaptive optics, are shown.

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Simulating Instruments For Mining Uncalibrated Archives

Technical Report No. : NUIG-IT-021204
By : Bruno Voisin, Seathrun O Tuairisg, Ray Butler, Aaron Golden, Andy Shearer, Alberto Micol

As the astronomical community continues to produce deeper and higher resolution data, it becomes increasingly important to provide tools to the scientist that help mining the data in order to provide only the scientifically interesting images. In the case of uncalibrated archives, this task is especially difficult as it is difficult to know whether an interesting source can be seen on images without actually looking. Here, we show how instrument simulation can be used to lightly process the database-stored image descriptors of the ESO/Wide Field Imager (WFI) archive, and compute the corresponding limiting magnitudes. The end result is a more scientific description of the ESO/ST-ECF archive contents, allowing a more astronomer-friendly archive user interface, and hence increasing the archive useability in the context of a Virtual Observatory. This method is developed for improving the Querator search engine of ESO/HST archive, in the context of the EC funded ASTROVIRTEL project, but also provides an independant tool that can be adapted to other archives.

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Using a Reversed Exposure Time Calculator for Querying Uncalibrated Archives

Technical Report No. : NUIG-IT-051204
By : Bruno Voisin, Seathrun O Tuairisg, Ray Butler, Aaron Golden, Andy Shearer, Alberto Micol

Mining large quantities of uncalibrated archives, for specific sources can prove to be a hard task. Even an automated search engine able to use an archive metadata (instrument, a filter, exposure time...) is not completely sufficient. Indeed, without calibration it is difficult to know whether an interesting source can be seen on images without actually looking. Here, we show how a ``reversed' exposure time calculator can be used to efficiently process the database-stored image descriptors of the ESO/Wide Field Imager (WFI) archive, and compute the corresponding limiting magnitudes. The end result is a more scientific description of the ESO/ST-ECF archive contents, allowing a more astronomer-friendly archive user interface, and hence increasing the archive useability in the context of a Virtual Observatory. This method is developed for improving the Querator search engine of ESO/HST archive, in the context of the EC funded ASTROVIRTEL project.

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Evolving, Analysing and Improving Global Term-Weighting Schemes in Information Retrieval

Technical Report No. : NUIG-IT-071204
By : R. Cummins and C. O Riordan

The ability of a term to distinguish documents, and ultimately topics, is crucial to the performance of many Information Retrieval models. We present and analyse global weighting schemes for the vector space model developed by means of evolutionary computation. The global schemes presented are shown to increase average precision over the IDF measure on TREC data. The global schemes are also shown to be consistent with Luhns theory of resolving power as certain middle frequency terms are assigned the highest weight. The use of the collection frequency measure of a term is seen as crucial to the performance of these schemes. We also show that the analysis of these evolved schemes is an important step to understanding and improving their performance.

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Evolving Connect-Four Playing Neural Networks Using Cultural Learning

Technical Report No. : NUIG-IT-081204
By : D. Curran, C. O Riordan

This paper describes a cultural learning approach to the evolution of agents to play the game of connect-four. Each agent has a neural network responsible for perceiving the current board configuration and selecting an appropriate next move. Populations evolve through population learning, a process of Darwinian evolution, using genetic algorithms. Cultural learning is implemented by selecting highly fit agents as teachers to instruct the next generation. Teachers communicate with pupils through a hidden layer in each neural network (the verbal input/output layer) and pupils attempt to replicate utterances by back-propagation. Experiments are conducted comparing the performance of populations employing population learning alone and populations employing both population and cultural learning.

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Robustness in Changing Environments in Populations of Neural Networks Using Cutural Evolution

Technical Report No. : NUIG-IT-091204
By : D. Curran, C. O'Riordan

The focus of this paper is to examine the effect of cultural learning on a population of agents in various types of dynamic environment. Cultural learning allows highly fit agents in a population to teach others in order to achieve higher levels of fitness. These agents are placed in environments which may change very frequently, moderately or infrequently. The performance of cultural learning is compared with experiments undertaken using population learning, i.e., genetic evolution, of agents in the same environments.

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An Improved Genetic Programming Technique for Identification of Solvents from Raman Spectra

Technical Report No. : NUIG-IT-131204
By : Kenneth Hennessy, Michael G. Madden, Jennifer Conroy and Alan G. Ryder

The aim of this study is to evaluate the effectiveness of genetic programming relative to that of more commonly-used methods for the identification of components within mixtures of materials using Raman spectroscopy. A key contribution of the genetic programming technique proposed in this research is that it explicitly aims to optimise the certainty levels associated with discovered rules, so as to minimize the chance of misclassification of future samples.

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Transfer of Experience between Reinforcement Learning Environments with Progressive Difficulty

Technical Report No. : NUIG-IT-141204
By : Michael G. Madden, Tom Howley

This paper describes an extension to reinforcement learning (RL), in which a standard RL algorithm is augmented with a mechanism for transferring experience gained in one problem to new but related problems. In this approach, named Progressive RL, an agent acquires experience of operating in a simple environment through experimentation, and then engages in a period of introspection, during which it rationalises the experience gained and formulates symbolic knowledge describing how to behave in that simple environment. When subsequently experimenting in a more complex but related environment, it is guided by this knowledge until it gains direct experience. A test domain with 15 maze environments, arranged in order of diï¬fculty, is described. A range of experiments in this domain are presented, that demonstrate the beneï¬?t of Progressive RL relative to a basic RL approach in which each puzzle is solved from scratch. The experiments also analyse the knowledge formed during introspection, illustrate how domain knowledge may be incorporated, and show that Progressive Reinforcement Learning may be used to solve complex puzzles more quickly.

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