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Articles 1 - 17 of 17

Full-Text Articles in Social and Behavioral Sciences

On The Soft X-Ray Spectrum Of Cooling Flows, A C. Fabian, R F. Mushotzky, Paul E. J Nulsen, J R. Peterson Jan 2001

On The Soft X-Ray Spectrum Of Cooling Flows, A C. Fabian, R F. Mushotzky, Paul E. J Nulsen, J R. Peterson

Faculty of Engineering and Information Sciences - Papers: Part A

Strong evidence for cooling flows has been found in low-resolution X-ray imaging and spectra of many clusters of galaxies. However, high-resolution X-ray spectra of several clusters from the Reflection Grating Spectrometer on XMM-Newton now show a soft X-ray spectrum inconsistent with a simple cooling flow. The main problem is a lack of the emission lines expected from gas cooling below 1–2 keV. Lines from gas at about 2–3 keV are observed, even in a high-temperature cluster such as A1835, indicating that gas is cooling down to about 2–3 keV, but is not found at lower temperatures. Here ...


Numerical Investigation Of The Angle Of Repose Of Monosized Spheres, Y C. Zhou, B H. Xu, Aibing Yu, Paul Zulli Jan 2001

Numerical Investigation Of The Angle Of Repose Of Monosized Spheres, Y C. Zhou, B H. Xu, Aibing Yu, Paul Zulli

Faculty of Engineering and Information Sciences - Papers: Part A

This paper presents a numerical study of the angle of repose, a most important macroscopic parameter in characterizing granular materials, by means of a modified distinct element method. Emphasis is given to the effect of variables related to factors such as particle characteristics, material properties, and geometrical constraints. The results show that sliding and rolling frictions are the primary reasons for the formation of a sandpile; particle size and container thickness significantly influence the angle of repose; and the angle of repose is not so sensitive to density, Poisson's ratio, damping coefficient, and Young's modulus. Increasing rolling friction ...


A Hierarchical Classifier For Multispectral Satellite Imagery, Abdesselam Bouzerdoum Jan 2001

A Hierarchical Classifier For Multispectral Satellite Imagery, Abdesselam Bouzerdoum

Faculty of Engineering and Information Sciences - Papers: Part A

In this article, a hierarchical classifier is proposed for classification of ground-cover types of a satellite image of Kangaroo Island, South Australia. The image contains seven ground-cover types, which are categorized into three groups using principal component analysis. The first group contains clouds only, the second consists of sea and cloud shadow over land, and the third contains land and three types of forest. The sea and shadow over land classes are classified with 99% accuracy using a network of threshold logic units. The land and forest classes are classified by multilayer perceptrons (MLPs) using texture features and intensity values ...


Does The Model Matter For Greg Estimation? A Business Survey Example, Dan Hedlin, Hannah Falvey, Raymond Chambers, Phillip Kokic Jan 2001

Does The Model Matter For Greg Estimation? A Business Survey Example, Dan Hedlin, Hannah Falvey, Raymond Chambers, Phillip Kokic

Faculty of Engineering and Information Sciences - Papers: Part A

Although asymptotically design-unbiased, GREG estimators may produce bad estimates. The article examines the behaviour of GREG estimators when the underlying models are misspecified. It shows how an efficient GREG estimator was found for a business survey that posed some problems. The work involved data exploration in several steps, combined with analyses of g-weights, residuals and standard regression diagnostics. We discuss two diagnostics for whether a GREG estimate is reasonable or not. A common justification for the use of GREG estimators is that, being asymptotically design unbiased, they are relatively robust to model choice. However, we show that the property of ...


Mat: A Mobile Agent System For Supporting Autonomous Mobile Agents, Wei Li, Minjie Zhang Jan 2001

Mat: A Mobile Agent System For Supporting Autonomous Mobile Agents, Wei Li, Minjie Zhang

Faculty of Engineering and Information Sciences - Papers: Part A

Mobile Agent Template (MAT) is a mobile agent system that is under study and development at the Institute of Computing Technology, Chinese Academy of Sciences and sponsored by the University of Wollongong, Australia. MAT is not an alternative to other mobile agent systems, but is an agent system that can provide the autonomy to mobile agents. MAT tries to support new Web applications, such as the mobile computation, by autonomous and mobile agents. Mobile Thread Programming Model (MTPM), Distributed Task Plan (DTP) and Active State Space (ASS) are integral components on which MAT is constructed. Integration of these three components ...


Pure Type Systems With More Liberal Rules, Martin W. Bunder, Wil Dekkers Jan 2001

Pure Type Systems With More Liberal Rules, Martin W. Bunder, Wil Dekkers

Faculty of Engineering and Information Sciences - Papers: Part A

Pure Type Systems. PTSs, introduced as a generalisation of the type systems of Barendregt's lambda-cube, provide a foundation for actual proof assistants, aiming at the mechanic verification of formal proofs. In this paper we consider simplifications of some of the rules of PTSs. This is of independent interest for PTSs as this produces more flexible PTS-like systems, but it will also help, in a later paper, to bridge the gap between PTSs and systems of Illative Combinatory Logic.

First we consider a simplification of the start and weakening rules of PTSs. which allows contexts to be sets of statements ...


Wiener Model Identification And Predictive Control For Dual Composition Control Of A Distillation Column, H H J Bloemen, C T. Chou, T J J Van Den Boom, V Verdult, M Verhaegen, T C. Backx Jan 2001

Wiener Model Identification And Predictive Control For Dual Composition Control Of A Distillation Column, H H J Bloemen, C T. Chou, T J J Van Den Boom, V Verdult, M Verhaegen, T C. Backx

Faculty of Engineering and Information Sciences - Papers: Part A

The benefits of using the Wiener model based identification and control methodology presented in this paper, compared to linear techniques, are demonstrated for dual composition control of a moderate-high purity distillation column simulation model. An identification experiment design is presented which enables one to identify both the low and high gain directions of the distillation column, properties which are important for control and hard to identify in a conventional identification experiment setup as is demonstrated in the paper. Data from the proposed experiment design is used for indirect closed-loop identification of both a linear and a Wiener model, which shows ...


Existence Of Positive Solutions Of Some Semilinear Elliptic Equations With Singular Coefficients, Nirmalendu Chaudhuri, Mythily Ramaswamy Jan 2001

Existence Of Positive Solutions Of Some Semilinear Elliptic Equations With Singular Coefficients, Nirmalendu Chaudhuri, Mythily Ramaswamy

Faculty of Engineering and Information Sciences - Papers: Part A

No abstract provided.


Multifibre Spectroscopy Of The Supernova Remnant Candidate Rcw 114, Andrew Walker, William Zealey Jan 2001

Multifibre Spectroscopy Of The Supernova Remnant Candidate Rcw 114, Andrew Walker, William Zealey

Faculty of Engineering and Information Sciences - Papers: Part A

RCW 114 is a filamentary nebula of about 250 arcmin diameter. Based on its large diameter-to-filament-width ratio, the expansion velocity, distance and size of the shell, it has been suggested that RCW 114 is a supernova remnant in its momentum-conserving phase. Confirmation of this identification is important, as the large angular size and extensive optical emission of this object will allow for detailed study to improve our knowledge of supernova remnants and their interaction with the interstellar medium.

We have used the FLAIR instrument on the UK Schmidt Telescope to obtain optical spectra of several filaments in RCW 114. These ...


Chandra X-Ray Observations Of The 3c 295 Cluster Core, S W. Allen, G B. Taylor, Paul E J Nulsen, R M. Johnstone, L P. David, S Ettori, A C. Fabian, W R. Forman, C Jones, B Mcnamara Jan 2001

Chandra X-Ray Observations Of The 3c 295 Cluster Core, S W. Allen, G B. Taylor, Paul E J Nulsen, R M. Johnstone, L P. David, S Ettori, A C. Fabian, W R. Forman, C Jones, B Mcnamara

Faculty of Engineering and Information Sciences - Papers: Part A

We examine the properties of the X-ray gas in the central regions of the distant (z=0.46), X-ray luminous cluster of galaxies surrounding the powerful radio source 3C 295, using observations made with the Chandra Observatory. Between radii of 50 and 500 kpc, the cluster gas is approximately isothermal with an emission-weighted temperature, kT∼5 keV. Within the central 50-kpc radius this value drops to kT∼3.7 keV. The spectral and imaging Chandra data indicate the presence of a cooling flow within the central 50-kpc radius of the cluster, with a mass deposition rate of approximately 280 M ...


Asca And Rosat Observations Of Nearby Cluster Cooling Flows, S W. Allen, A C. Fabian, R M. Johnstone, K A. Arnaud, Paul E J Nulsen Jan 2001

Asca And Rosat Observations Of Nearby Cluster Cooling Flows, S W. Allen, A C. Fabian, R M. Johnstone, K A. Arnaud, Paul E J Nulsen

Faculty of Engineering and Information Sciences - Papers: Part A

We present a detailed analysis of the X-ray properties of the cooling flows in a sample of nearby, X-ray-bright clusters of galaxies using high-quality ASCA spectra and ROSAT X-ray images. We demonstrate the need for multiphase models to consistently explain the spectral and imaging X-ray data for the clusters. The mass deposition rates of the cooling flows, independently determined from the ASCA spectra and ROSAT images, exhibit reasonable agreement. We confirm the presence of intrinsic X-ray absorption in the clusters using a variety of spectral models. We also report detections of 100-μm infrared emission, spatially coincident with the cooling flows ...


The Soft X-Ray Background: Evidence For Widespread Disruption Of The Gas Haloes Of Galaxy Groups, K K S Wu, A C. Fabian, Paul E. J Nulsen Jan 2001

The Soft X-Ray Background: Evidence For Widespread Disruption Of The Gas Haloes Of Galaxy Groups, K K S Wu, A C. Fabian, Paul E. J Nulsen

Faculty of Engineering and Information Sciences - Papers: Part A

Almost all of the extragalactic X-ray background (XRB) at 0.25 keV can be accounted for by radio-quiet quasars, allowing us to derive an upper limit of 4 keV cm−2 s−1 sr−1 keV−1 for the remaining background at 0.25 keV. However, the XRB from the gas haloes of groups of galaxies, with gas removal resulting from cooling accounted for, exceeds this upper limit by an order of magnitude if non-gravitational heating is not included. We calculate this using simulations of halo merger trees and realistic gas density profiles, which we require to reproduce the observed ...


A General Projection Framwork For Constrained Smoothing, E Mammen, J S. Marron, B A. Turlach, M P. Wand Jan 2001

A General Projection Framwork For Constrained Smoothing, E Mammen, J S. Marron, B A. Turlach, M P. Wand

Faculty of Engineering and Information Sciences - Papers: Part A

There are a wide array of smoothing methods available for finding structure in data. A general framework is developed which shows that many of these can be viewed as a projection of the data, with respect to appropriate norms. The underlying vector space is an unusually large product space, which allows inclusion of a wide range of smoothers in our setup (including many methods not typically considered to be projections). We give several applications of this simple geometric interpretation of smoothing. A major payoff is the natural and computationally frugal incorporation of constraints. Our point of view also motivates new ...


Filamentary Shell Structures From The Aao/Ukst Ha Survey, Andrew Walker, William Zealey, Q A. Parker Jan 2001

Filamentary Shell Structures From The Aao/Ukst Ha Survey, Andrew Walker, William Zealey, Q A. Parker

Faculty of Engineering and Information Sciences - Papers: Part A

Here we present the first results of a search for new optical supernova remnant candidates and other filamentary objects on films produced by the Anglo-Australian Observatory/UK Schmidt Telescope Há Survey. Sixty-one fields, or 26% of the Galactic plane survey fields, have been visually examined. This has resulted in the detection of four newlarge diameter filamentary structures, and the discovery of extensive new optical emission in two previously known optical supernova remnant candidates.


Values Of Minors Of An Infinite Family Of D-Optimal Designs And Their Application To The Growth Problem, C Koukouvinos, M Mitrouli, Jennifer Seberry Jan 2001

Values Of Minors Of An Infinite Family Of D-Optimal Designs And Their Application To The Growth Problem, C Koukouvinos, M Mitrouli, Jennifer Seberry

Faculty of Engineering and Information Sciences - Papers: Part A

No abstract provided.


The Application Of Coupled Bolts In Managing Adverse Horizontal Stress Conditions At Oaky Creek Coal, Justine D. Calleja Jan 2001

The Application Of Coupled Bolts In Managing Adverse Horizontal Stress Conditions At Oaky Creek Coal, Justine D. Calleja

Faculty of Engineering and Information Sciences - Papers: Part A

Development drivage of Tailgate 21 commenced in May 2000. Difficult roof conditions associated with the splitting of the G ply coal away from the immediate seam into the roof were anticipated. 4.1m Coupled Bolts were considered to be a potentially cheaper and more effective reinforcement system than long tendon cables for these conditions. Coupled bolts have been used very effectively in similar conditions at Alliance Colliery. Coupled bolts were trialed for the first time at Oaky No. 1 between 18-19c/t TG21 where the interburden thickness between the roof and the G Ply seam split was between 1.4m ...


Pilot-Scale Testing Of Diatomaceous Earth Filtration For Removal Of Cryptosporidium Oocysts, Jerry E. Ongerth, Primrose E. Hutton Jan 2001

Pilot-Scale Testing Of Diatomaceous Earth Filtration For Removal Of Cryptosporidium Oocysts, Jerry E. Ongerth, Primrose E. Hutton

Faculty of Engineering and Information Sciences - Papers: Part A

No abstract provided.