Finite-amplitude love-waves on an isotropic layered half-space

A pair of semi-linear hyperbolic partial differential equations governing the slow variations in amplitude and phase of a quasi-monochromatic finite-amplitude Love-wave on an isotropic layered half-space is derived using the method of multiple-scales. The analysis of the exact solution of these equations for a signalling problem reveals that the amplitude of the wave remains constant along its characteristic and that the phase of the wave increases linearly behind the wave-front.

Growing healthy sweetpotato: best practices for producing planting material

Sweetpotato is a major food crop in Papua New Guinea, with about 2.9 million tonnes grown each year. But sweetpotato is prone to pests and diseases, particularly viruses, which can significantly reduce yields. Because there are no varieties known to be resistant to viruses, the next best solution is to produce planting material that is free from infection, and to make this readily available to growers. This manual is aimed at researchers and technicians, and describes how to test for sweetpotato viruses and to keep vines free from infection. The methods described should help locals in PNG and other Pacific nations produce disease-free planting material for sweetpotato and other root and tuber crops.

TlBr raw material purification, crystal growth, annealing, detector fabrication and characterisation for gamma-ray detector applications

The research reported in this thesis dealt with single crystals of thallium bromide grown for gamma-ray detector applications. The crystals were used to fabricate room temperature gamma-ray detectors. Routinely produced TlBr detectors often are poor quality. Therefore, this study concentrated on developing the manufacturing processes for TlBr detectors and methods of characterisation that can be used for optimisation of TlBr purity and crystal quality. The processes under concern were TlBr raw material purification, crystal growth, annealing and detector fabrication. The study focused on single crystals of TlBr grown from material purified by a hydrothermal recrystallisation method. In addition, hydrothermal conditions for synthesis, recrystallisation, crystal growth and annealing of TlBr crystals were examined. The final manufacturing process presented in this thesis deals with TlBr material purified by the Bridgman method. Then, material is hydrothermally recrystallised in pure water. A travelling molten zone (TMZ) method is used for additional purification of the recrystallised product and then for the final crystal growth. Subsequent processing is similar to that described in the literature. In this thesis, literature on improving quality of TlBr material/crystal and detector performance is reviewed. Aging aspects as well as the influence of different factors (temperature, time, electrode material and so on) on detector stability are considered and examined. The results of the process development are summarised and discussed. This thesis shows the considerable improvement in the charge carrier properties of a detector due to additional purification by hydrothermal recrystallisation. As an example, a thick (4 mm) TlBr detector produced by the process was fabricated and found to operate successfully in gamma-ray detection, confirming the validity of the proposed purification and technological steps. However, for the complete improvement of detector performance, further developments in crystal growth are required. The detector manufacturing process was optimized by characterisation of material and crystals using methods such as X-ray diffraction (XRD), polarisation microscopy, high-resolution inductively coupled plasma mass (HR-ICPM), Fourier transform infrared (FTIR), ultraviolet and visual (UV-Vis) spectroscopy, field emission scanning electron microscope (FESEM) and energy-dispersive X-ray spectroscopy (EDS), current-voltage (I-V) and capacity voltage (CV) characterisation, and photoconductivity, as well direct detector examination.

Natural frequencies of polar orthotropic annular plates

The classical Rayleigh-Ritz method with simple polynomials as admissible functions has been used for obtaining natural frequencies of transversely vibrating polar orthotropic annular plates. The method in conjunction with transformations introduced in the analysis has been found to be quite effective, particularly for large hole sizes. Estimates of natural frequencies corresponding to modes with one as well as two nodal diameters are obtained for the nine combinations of clamped, simply supported and free edge conditions and for various values of rigidity ratio and hole sizes. Based on the variation of eigenvalue parameter with rigidity ratio, the frequencies of these modes as well as those of axisymmetric modes have been expressed by means of simple formulae in terms of rigidity ratio and the frequencies of corresponding modes in the isotropic case. These formulae have been used in determining the fundamental frequencies of orthotropic plates.

Taken for granted: Material relations between disability and codes/guidelines

This paper provides a critical examination of the taken for granted nature of the codes/guidelines used towards the creation of designed spaces, their social relations with designers, and their agency in designing for people with disabilities. We conducted case studies at three national museums in Canada where we began by questioning societal representations of disability within and through material culture through the potential of actor-network theory where non-human actors have considerable agency. Specifically, our exploration looks into how representations of disability for designing, are interpreted through mediums such as codes, standards and guidelines. We accomplish this through: deep analyses of the museums’ built environments (outdoors and indoors); interviewed curators, architects and designers involved in the creation of the spaces/displays; completed dialoguing while in motion interviews with people who have disabilities within the spaces; and analyzed available documents relating to the creation of the museums. Through analyses of our rich data set involving the mapping of codes/guidelines in their ‘representation’ of disability and their contributions in ‘fixing’ disability, this paper takes an alternative approach to designing for/with disability by aiming to question societal representations of disability within and through material culture.

Material processing and surface reaction studies in free piston driven shock tube

Recently established moderate size free piston driven hypersonic shock tunnel HST3 along with its calibration is described here. The extreme thermodynamic conditions prevalent behind the reflected shock wave have been utilized to study the catalytic and non-catalytic reactions of shock heated test gases like Ar, N2 or O2 with different material like C60 carbon, zirconia and ceria substituted zirconia. The exposed test samples are investigated using different experimental methods. These studies show the formation of carbon nitride due to the non-catalytic interaction of shock heated nitrogen gas with C60 carbon film. On the other hand, the ZrO2 undergoes only phase transformation from cubic to monoclinic structure and Ce0.5Zr0.5O2 in fluorite cubic phase changes to pyrochlore (Ce2Zr2O7±δ) phase by releasing oxygen from the lattice due to heterogeneous catalytic surface reaction.

Nonlinear mode coupling of surface acoustic waves on an isotropic solid

The nonlinear mode coupling between two co-directional quasi-harmonic Rayleigh surface waves on an isotropic solid is analysed using the method of multiple scales. This procedure yields a system of six semi-linear hyperbolic partial differential equations with the same principal part governing the slow variations in the (complex) amplitudes of the two fundamental, the two second harmonic and the two combination frequency waves at the second stage of the perturbation expansion. A numerical solution of these equations for excitation by monochromatic signals at two arbitrary frequencies, indicates that there is a continuous transfer of energy back and forth among the fundamental, second harmonic and combination frequency waves due to mode coupling. The mode coupling tends to be more pronounced as the frequencies of the interacting waves approach each other.

Nonlinear surface acoustic waves on an isotropic solid

A systematic derivation of the approximate coupled amplitude equations governing the propagation of a quasi-monochromatic Rayleigh surface wave on an isotropic solid is presented, starting from the non-linear governing differential equations and the non-linear free-surface boundary conditions, using the method of mulitple scales. An explicit solution of these equations for a signalling problem is obtained in terms of hyperbolic functions. In the case of monochromatic excitation, it is shown that the second harmonic amplitude grows initially at the expense of the fundamental and that the amplitudes of the fundamental and second harmonic remain bounded for all time.

Rapid synthetic routes to prepare LiNi1/3Mn1/3Co1/3O2 as a high voltage, high-capacity Li-ion battery cathode material

LiNi1/3Mn1/3Co1/3O2, a high voltage and high-capacity cathode material for Li-ion batteries, has been synthesized by three different rapid synthetic methods. viz. nitrate-melt decomposition, combustion and sol-gel methods. The first two methods are ultra rapid and a time period as small as 15 min is sufficient to prepare nano-crystalline LiNi1/3Mn1/3Co1/3O2. The processing parameters in obtaining the best performing materials are optimized for each process and their electrochemical performance is evaluated in Li-ion cells. The combustion-derived LiNi1/3Mn1/3Co1/3O2 sample exhibits large extent of cation mixing (10%) while the other two methods yield LiNi1/3Mn1/3Co1/3O2 with cation mixing <5%. LiNi1/3Mn1/3Co1/3O2 prepared by nitrate-melt decomposition method exhibits superior performance as Li-ion battery cathode material.

Material characterisation and numerical modelling of gypsum plasterboards in fire

The fire resistance characteristic of LSF wall systems mainly depends on the protective linings in use, commonly gypsum plasterboards. However, unclassified boards with varying composition and more notably with ambiguous thermal properties are increasingly becoming available in the market. Therefore a study was undertaken with an aim to set minimum standards for fire protective boards used in LSF wall applications. This paper presents the details of this study based on material characterisation and finite element thermal modelling of the most commonly used fire protective board, gypsum plasterboards, to address these critical issues related to fire safety design. In the material characterisation phase of this study, thermal properties of three different gypsum plasterboards manufactured in Australia were measured, analysed and compared. Subsequently, it proposes a thermal property based “k-factor” capable of giving an overall measure of the fire performance of boards, so that it can be used in appropriately classifying fire protective boards. As it is not known how this factor relates to the overall fire performance of LSF wall systems, numerical models were also developed and used to simulate the performance of LSF walls exposed to the standard fire. Finally, a correlation between time-temperature profiles from numerical analyses and calculated k-factors was established.

Nd2O3 : Eu3+ nanocrystalline phosphor - a new potential thermoluminescing material for dosimetry

Nanoparticles of trivalent Eu3+-doped Nd2O3 phosphors have been prepared using a low-temperature solution combustion method with metal nitrate as precursor and oxalyldihydrazide as a fuel at a fairly low temperature (<500 degrees C) and in a very short time (<5 min). A powder X-ray diffraction pattern reveals that cubic Nd2O3 : Eu3+ crystallites are directly obtained without the requirement of further calcinations. The crystallite size, evaluated from Scherer's formula, was found to be in the range of 20-30 nm. The microstructure and morphology were studied by scanning electron microscopy, which showed the phosphor to be foamy and fluffy in nature. Thermoluminescence characteristics of the Nd2O3 : Eu3+ have been studied using gamma irradiation. These demonstrate that the phosphor is suitable for use as a dosimeter.

Material matters [curators]

The exhibition material matters brings together new works by Amy Commins, Jamie Behrendorff, Grace Kevill-Davies, Zoe Knight, Ruth McConchie and Courtney Pedersen – Brisbane-based artists whose experimental practices engage with materiality in specific ways. These works explore incidental viewpoints, suspended moments, constructed environments, cultural memory and repetitive processes. The artists in the exhibition investigate the temporal in terms of making and experiencing art in various modes – installation, sculpture, video, sound and works on paper. Through these material engagements, the artists question and re-imagine ways of connecting in the contemporary world, drawing together considerations of humour, history, politics, nature and everyday life. This exhibition was part of the 2014 Brisbane Experimental Art Festival, held at the Judith Wright Centre of Contemporary Arts.

Microtribology and Friction-Induced Material Transfer in Layered MoS2 Nanoparticles Sprayed on a Steel Surface

Frictional performance of molybdenum disulfide (MoS2) particles sprayed on a substrate is investigated in a ball-on-disc tribometer. The ability of large (similar to 2 mu m) and small (similar to 50 nm) particles to generate low-friction transfer film is investigated with a view to elucidate the requirement for film formation. Particle migration, particle stability in the contact region, oxidation potential, and particle adhesion to the substrate are explored within a span of operating parametersp; normal load, and sliding velocity. It is found that the larger particles are able to migrate to the contact to raise a homogeneous but nonuniform low-friction transfer film that flows plastically to yield large contact areas, which aid in wear protection. Within the present load and speed range, the inability of small particles to stay in the contact region and undergo basal slip militates against the formation of a low-friction transfer film.

Ce0.67Cr0.33O2.11: A New Low-Temperature O-2 Evolution Material and H-2 Generation Catalyst by Thermochemical Splitting of Water

Ce0.67Cr0.33O2.11 was synthesized by hydrothermal method using diethylenetriamine as complexing agent (Chem. Mater. 2008, 20, 7268). Ce0.67Cr0.33O2.11 being the only compound likes UO2+delta to have excess oxygen, it releases a large proportion of its lattice oxygen (0.167 M [O]/mole of compound) at relatively low temperature (465 degrees C) directly and it has been utilized for generation of H-2 by thermo-splitting of water. An almost stoichiometric amount of H-2 (0.152 M/Mole of compound) is generated at much lower temperature (65 degrees C). There is an almost comparable amount of oxygen release and hydrogen generation over this material at very low temperature comparedto other CeO2-MOx (Mn, Fe, Cu, and Ni) mixed-oxide solid solutions (O-2 evolution >= 1300 degrees C and H-2 generation at 1000 degrees C). The reversible nature of oxygen release and intake of this material is attributed to its fluorite Structure and coupling between the Ce4+/Ce3+ and Cr4+/6+/Cr3+ redox couples. Compound shows reversible oxygen release and intake by H2O absorption and subsequent hydrogen release to gain parent structure and hence this material can be utilized for generation of H-2 at very low temperature by thermo-chemical splitting of water.