Engineering Commons^™

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 gas fractions …

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_{⊙ …}

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

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

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

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 and 4m. Indicators …

New Legislative Framework And The Role Of Geotechnical And Gas Drainage Professionals, I. Anderson

Resource Operators Conference

In recent times legislators have moved away from prescriptive legislation to duty of care models. Such a move places employers and consultants under a need to demonstrate due diligence in the exercise of their functions. The principle legislation under which the coal industry operates is the New South Wales Occupational Health and Safety Act. This Act has substantial punitive measures including fines and imprisonment. The Department of Mineral Resources has developed and implemented an Enforcement policy which includes a prosecution element.
These changes necessarily impact upon key industry personnel including:
i) Mine Managers
ii) Internal Consultants - Company Engineers
iii) …

How Nsw And Queensland Coalfields Differ - What We Need To Do Better, B. Nicholls

Resource Operators Conference

There are obviously similarities and differences between NSW and Queensland underground coal mines. The major differences are related to rock strengths, stress regimes, location and operational approaches. Issues relating to these factors are addressed, with some suggestions as to how underground coal miners can do some things better to improve efficiencies and returns on investment. The differences are many and varied. Some factors having a major bearing on mining efficiencies are discussed, with some examples of failures and successes being outlined.

Gas Emission Modelling Of Gate Road Development, R. J. Williams, E. Yurakov, D. J. Ashelford

Resource Operators Conference

This paper covers the modelling of gas emission during gate road development. Complexities related to the range of gas reservoir and mining data are briefly described. The rib emission response to initial gas reservoir parameters is defined using the SIMED II gas reservoir simulator. The rib emission decay curves are then used in an interactive EXCEL spreadsheet model that takes additional account of mining and ventilation parameters. It is an attempt at bringing to planners and mine operators an interactive tool that incorporates the important parameters and options.
SIMED’s strengths lie in it’s ability to:
• quickly convey a message …

Longwalling And Its Impact In The Southern Coalfield - Recent Bhp Experiences, P. Eade, J. Wood

Resource Operators Conference

Illawarra Coal BHP Minerals currently operate five underground coal mines in the Southern Coalfield of New South Wales in Australia. Each mine operates a retreating longwall extraction system as the primary production process. Economic reserves at several of the mines are nearing exhaustion and a feasibility study is under way to maintain production levels by development of a new mine. The level of maturity of the current operations and the nature of the remaining coal reserves in the Southern Coalfield present significant challenges for continued viable longwall mining. A general overview of the challenges and recent BHP experiences in relation …

Towards High Productivity Under A "Claystone" Roof: Great Northern Seam Support Management Experiences At Chain Valley, Moonee And Wallarah Collieries, P. J. Hayes

Resource Operators Conference

Coal Operations Australia Limited Operates the Chain Valley, Wallarah and Moonee Collieries which are located in the Newcastle Coal Fields of New South Wales in the Catherine Hill Bay area approximately 100km north of Sydney. Operations are in the Great Northern seam, which until recent years were all conducted under an immediate roof of a strong conglomerate. Large areas of the current reserves at all operations are in areas of a “claystone” immediate roof. All three mines have attempted at various stages of their history to find an economic mining method under these claystone roof conditions, with varying degrees of …

Successes And Future Challenges For Longwall Mining In Structured Ground, I. Stone

Resource Operators Conference

The experiences from the recent 3 years at Springvale Mine have highlighted once again the importance of understanding the geological structure at a mine site. Springvale Mine previously had a history of difficult roof conditions, although not clearly linked to geological structure. From mid 1998 a series of complex strike slip fault structures were encountered, one set running with and along the commencement of the 404 Panel gateroads. The unexpected faulting, its critical location, and unknown extent had a serious impact on panel development and business performance. Even the most carefully constructed business plan and budget is quickly damaged by …

Geotechnical Engineering At German Creek - A Historical And Sometimes Hysterical Review, M. Jakeman

Resource Operators Conference

The initial drilling exploration started in what we now know as the Bowen Basin coal region in the 1950’s, to open up and delineate the coal seams for the whole region. After Utah grabbed the easiest and more favorable large sandpits in the early stages, other companies started to understand the opportunities for the future. In 1979, German Creek started construction and operations at the end of the boom and bought four draglines. This paper presents the geotechnical experiences at German Creek over 21 years of operations. Today, the operation sustains one dragline, two underground longwall operations and another underground …

Thermal Diffusivity Of Iron At High Temperature In Both The Liquid And Solid States, Brian J. Monaghan, P N Quested

Faculty of Engineering - Papers (Archive)

Process models that simulate industrial processes are increasingly being used to reduce costs and improve productivity. 1–8) The success of such models is highly dependent on the thermophysical property data used in the simulation calculations. Unfortunately high temperature thermophysical data for liquid metals and slags are scarce. Also what data that are available often have a high uncertainty associated with them.1,2,9–11) Therefore regardless of how well a process model may be physically based it is likely, given the current state of high temperature thermophysical property data, in particular heat capacity, viscosity and thermal conductivity/ diffusivity, that the models predictions will …

Mechanism For Unstable Pneumatic Conveying Of Granular Materials Through Horizontal Pipe, J Yi, Peter W. Wypych, David B. Hastie

Faculty of Engineering - Papers (Archive)

Since the pneumatic conveying performance of granular materials in the transition zone between dilute- phase and dense-phase still lacks full understanding and assessment, especially the mechanism for the formation of unstable flow, tests have been carried out on poly pellets (particle diameter = 4.7 mm, particle density = 897 kg/m3) and two different stainless steel pipelines (60.3 and 98.4 mm ID, each 21 m long). By careful observation and analysis of flow behaviours (covering dilute-phase, unstable zone and low-velocity slug-flow), five different flow modes (as the air velocity is decreased): fully suspended flow; strand flow; stable or unstable strand flow …

A Versatile Experimental Test Rig For Gma Welding Research, Gary Dean, Dominic Cuiuri, John Norrish, Christopher David Cook

Faculty of Engineering - Papers (Archive)

Welding process research is severely hampered when adequate experimental equipment is not available. With the development of numerous welding processes and the control techniques associated with them, the need now exists for experimental equipment that offers the flexibility to control these processes and to set up parameters associated with the research.

At the University of Wollongong an experimental research rig has been developed based on a digital signal processor control system that offers the researcher the facilities to study the various processes associated with GMA welding.

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 we discuss several …

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, …

Early Days Of Rock Mechanics And Strata Control, J. Enever

Resource Operators Conference

BHP/AIS's Rock Mechanics and Strata Control (RM & SC) Group was formed in the late 1960's to address a range of issues then facing BHP/AIS's underground coal mining operations. Building on a local tradition of innovative rock mechanics and a global body of research targeted at sedimentary strata behaviour, RM & SC tackled a number of critical areas and made substantive contributions in all of these. Alan Hargraves, as the leader of the group, had a significant influence on all activities, as well as continuing personal research in the area of seam gas management. A direct line can be traced …

Outbursts - Management And Control, J. Hanes

Resource Operators Conference

This paper summarises some of the development of the understanding and management of outbursts in Australia, reviews the current situation and provides some thoughts on necessary research and development. It cannot be and is not comprehensive. Outbursts are better understood, prevented or controlled than they were 20 years ago. This is partly a result of the considerable amount of research into and documentation of outbursts and gas by a relatively small group of outburst pioneers supported by the coal industry. The result has been fewer outbursts in general, and the safe mining through a few potential outburst zones without risk …

Gas Drainage Practices, L. W. Lunarzewski

Resource Operators Conference

Coal seam gas problems, largely “gas-outs” and instantaneous outbursts of coal and gas, have created serious difficulties for the coal mining industry around the world. Typically, a single longwall face is now capable of producing an average 10 000 to 15 000 tonnes of coal per day. The total quantity of gas released in gassy mines could conceivably reach 5000 and 8000 litres of gas per second per single longwall block and for the total mine respectively. The introduction of various gas drainage techniques in Australian gassy mines was necessary to complement ventilation systems and to satisfy the statutory gas …

Feasibility Study Of Online High-Spatial-Resolution Mosfet Dosimetry In Static And Pulsed X-Ray Radiation Fields, Anatoly B. Rosenfeld, M. L. Lerch, T. Kron, E. Brauer-Krisch, A. Bravin, A. Holmes-Siedle, B. J. Allen

Faculty of Engineering - Papers (Archive)

Improvements have been made in the measurement of dose profiles in several types of X-ray beams. These include 120-kVp X-ray beams from an orthovoltage X-ray machine, 6-MV Bremsstrahlung from a medical LINAC in conformal mode and the 50-200 keV energy spectrum of microbeams produced at the medical beamline station of the European Synchrotron Radiation Facility. Using a quadruple metal-oxide-semiconductor field-effect transistor (MOSFET) sensor chip in "edge on" mode together with a newly developed sensor readout system, the feasibility of online scanning of the profiles of quasi-static and pulsed radiation beams was demonstrated. Measurements of synchrotron pulsed microbeams showed that a …

Dependence Of The Flux-Creep Activation Energy On Current Density And Magnetic Field For The Mgb2 Superconductor, M. J. Qin, Xiaolin Wang, Saeid Soltanian, Aihua Li, Hua-Kun Liu, S. X. Dou

Faculty of Engineering - Papers (Archive)

Systematic ac susceptibility measurements have been performed on a MgB₂ bulk sample. We demonstrate that the flux creep activation energy is a nonlinear function of the current density U(j)∝j^-0.2, indicating a nonlogarithmic relaxation of the current density in this material. The dependence of the activation energy on the magnetic field is determined to be a power law U(B)∝B^-1.33, showing a steep decline in the activation energy with the magnetic field, which accounts for the steep drop in the critical current density with magnetic field that is observed in MgB₂. The irreversibility field is …

Development Of A High Power Microwave Plasma Beam Applicator, S. A. Gower

Faculty of Engineering - Papers (Archive)

An efficient plasma beam applicator has been developed that utilizes countercurrent cooling techniques to operate at atmospheric pressure and at microwave powers in excess of 5 kW. The device has been operated continuously for tens of hours and shows no signs of degradation. Argon is used as the discharge gas and once initiated, the plasma is self-sustaining. The beam or jet of plasma is highly collimated with a beam diameter of 3 mm, is in excess of 250 mm in length, and has high heat capacity. It could potentially be used to melt industrial ceramics such as silica and alumina, …

Measurement Of Air Leakage Through Rotary Valves, David B. Hastie, Ian Frew, David M. Cook, Peter W. Wypych

Faculty of Engineering - Papers (Archive)

This paper explains the procedure used to determine the amount of air leakage expelled from two different sized drop-through rotary valves. When designing a pneumatic conveying system, rotary valve air leakage may be overlooked, believed to be only a minor factor. This is somewhat true when conveying in dilute-phase where low pressures are generated, however in dense-phase pneumatic conveying where higher pressures can be produced, rotary valve air leakage can be a high proportion of the supplied air. Knowing the air leakage present for any given situation, the total supplied air mass flowrate can be adjusted to represent the actual …

Distributed Polarizability Of The Water Dimer: Field-Induced Charge Transfer Along The Hydrogen Bond, Marc In Het Panhuis, P L A Popelier, R W. Munn, J G. Angyan

Australian Institute for Innovative Materials - Papers

The topological partitioning of electronic properties approach at Hartree-Fock level is used to investigate charge transfer response in a water dimer. Distributed polarizability components are employed to calculate the change in electron density under external fields. Field-induced charge flow between the water monomers is most significant along the direction of the hydrogen bond. The molecular polarizability of the molecules in the dimer is reduced owing to formation of the hydrogen bond.

Thermionic Cooling Of Optoelectronic And Microelectronic Devices, S. P. Lee, B. C. Lough, R. A. Lewis, C. Zhang

Faculty of Engineering - Papers (Archive)

Solid-state thermionic cooling has gained attention recently because of its potential high cooling power. Thermionic devices based on semiconductor heterostructures utilize the band-edge offset at a heterojunction as the thermionic emission potential barrier and a thin layer to separate the cold and hot junction. In this paper, we present the behavior of thermionic coolers with periodic barriers using gallium arsenide/aluminium gallium arsenide (GaAs/Al/sub x/Ga/sub 1-x/As) semiconductor heterostructures. The exact numerical calculation to model the device performance has shown that the thermal efficiency in a multilayer structure is optimised when the effect of phonon scattering is introduced in the model. Besides, …

Chandra Observation Of Abell 2142: Survival Of Dense Subcluster Cores In A Merger, M. Markevitch, T. J. Ponman, P. Nulsen, M. W. Bautz, D. J. Burke, L. P. David, D. Davis, R. H. Donnelly, W. R. Forman, C. Jones, J. Kaastra, E. Kellogg, D. W. Kim, J. Kolodziejczak, P. Mazzotta, A. Pagliaro, S. Patel, L. Van Speybroeck, A. Vikhlinen, J. Vrtilek, M. Wise, P. Zhao

Faculty of Engineering - Papers (Archive)

We use Chandra data to map the gas temperature in the central region of the merging cluster A2142. The cluster is markedly nonisothermal; it appears that the central cooling flow has been disturbed but not destroyed by a merger. The X-ray image exhibits two sharp, bow-shaped, shocklike surface brightness edges or gas density discontinuities. However, temperature and pressure profiles across these edges indicate that these are not shock fronts. The pressure is reasonably continuous across these edges, while the entropy jumps in the opposite sense to that in a shock (i.e., the denser side of the edge has lower temperature, …

Internal Transitions Of Confined Neutral Magnetoexcitons In Gaas/Alxga1–Xas Quantum Wells, H. A. Nickel, G. Kioseoglou, T. Yeo, H. D. Cheong, A. Petrou, B. D. Mccombe, D. Broido, K. K. Bajaj, R. A. Lewis

Faculty of Engineering - Papers (Archive)

Optically detected resonance spectroscopy has been used to study resonant absorption of electrons, holes, and their complexes in GaAs/AlxGa1–xAs quantum wells (QW's) in magnetic fields up to 15 T. In undoped multiple-QW samples with well widths of 12.5, 15, and 20 nm, in addition to an electron and two hole cyclotron resonances, 1s-->np+,– (in the hydrogenic notation) internal exciton transitions (IET's) arising from two distinct neutral heavy-hole magneto-excitons were observed. The unique capability of observing electron and hole cyclotron resonance as well as several IET's in a single sample permitted verification of a predicted relationship resulting from the symmetry …

Characterisation Of Indium Phosphide Using Terahertz Radiation, R. L. Causley, R. A. Lewis

Faculty of Engineering - Papers (Archive)

Specimens of undoped, n-type and p-type bulk InP have been investigated using THz radiation. Reflection spectroscopy permits the determination of the TO and LO phonon energies as well as the carrier concentration. Absorption spectroscopy reveals transitions between impurity states. We report the first absorption spectrum of an acceptor in InP. The transition energies agree well with electronic Raman scattering and photoluminescence data.