Ajay Limaye

Australian National University | ANU · National Computational Infrastructure

A better understanding of ore breakage and fragmentation is a key to meeting important industrial challenges as the mining industry is exploring and extracting more low-grade ore deposits.

Potassium silicate alteration is a hallmark of the porphyry copper deposits that supply two thirds of the world's annual copper demand. These deposits formed in the cores of calc-alkaline to alkaline volcanic systems from the flux of magmatic gas that transported copper and other metals from source to the surface. The giant 3.2 Ma Grasberg CuAu dep...

Objectives: Although 3-dimensional (3D) printing is becoming more widely adopted for clinical applications, it is yet to be accepted as part of standard practice. One of the key applications of this technology is orthopaedic surgical planning for urgent trauma cases. Anatomically accurate replicas of patients' fracture models can be produced to gui...

A better understanding of the relation between ore fragmentation and ore texture is a key to the energy efficient extraction of targeted minerals from low grade ore deposits. In this study, X-ray micro-computed tomography is employed to study mineral liberation during the tensile failure and onset of fragmentation of a copper ore. We present the re...

Background: 3D imaging and 3D printing have been widely adopted and profoundly impacted our healthcare. The use of 3D technology has a great potential to facilitate pre-operative planning and clinical education, allowing versatile view and measure of landmarks from a patient’s model pre- and during operation. However, the current clinical practice...

Computed tomography (CT) has become very widely used in scientific and medical research and industry for its non-destructive and high-resolution means of detecting internal structure. Three-dimensional segmentation of computed tomography data sheds light on internal features of target objects. Three-dimensional segmentation of CT data is supported...

3D scientific visualization is a popular non-destructive investigation tool, however current imaging processing and 3D visualization software has compatibility barriers which make replicability and reproducibility in research difficult. To solve this, we developed a new revisualization method and demonstrated four case studies using three mainstrea...

Computational tomography is more and more widely used in many fields for its non-destructive and high-resolution in detecting internal structures of the samples. 3D segmentation of computed tomography data, which sheds light into internal features of target objects, is increasingly gaining in importance. However, how to efficiently and precisely re...

Medical students have enthusiastically embraced the use of virtual reality (VR) systems to help them understand the complex anatomy of body components. We hypothesize that students studying the structure and protection of wood will show similar acceptance of VR systems. We developed X-ray micro-CT models to show the distribution of silica in the Au...

Only a few weevils have been described from Burmese amber, and although most have been misclassified, they show unusual and specialised characters unknown in extant weevils. In this paper, we present the results of a study of a much larger and more diverse selection of Burmese amber weevils. We prepared all amber blocks to maximise visibility of st...

Assessing the mechanisms of micro-structural change and their effect on transport properties using digital core analysis requires balancing field of view and resolution. This typically leads to the compromise of working with relatively small samples, where boundary effects can be substantial. A direct comparison with experiment, as e.g. desirable t...

Oriented strand board (OSB) is an important wood composite used in situations where fungal decay and termite attack can occur. To counter these threats, powdered zinc borate biocide is commonly added to OSB. The effectiveness of biocides depends on their even distribution within composites and resistance to leaching, but little is known about the d...

The micro-distribution of preservatives in wood has fascinated many scientists. Their fascination with this subject stems from the challenges of mapping and quantifying preservative elements in the complex porous micro-structure of wood and the even greater challenge of linking the micro-distribution of preservatives to the performance of the treat...

Among several rendering techniques for volumetric data, direct volume rendering is a powerful visualization tool for a wide variety of applications. This paper describes the major features of hardware based volume exploration and presentation tool - Drishti. The word, Drishti, stands for vision or insight in Sanskrit, an ancient Indian language. Dr...

X-ray micro-CT is used here to visualize the distribution of melamine–urea–formaldehyde adhesive in the wood composite, particleboard, and examine changes in adhesive distribution on wood particles (flakes) before and after pressing. CT and scanning electron microscopy of unpressed, wax-covered, wood flakes reveals that adhesive is evenly distribut...

Technologies for imaging in three dimensions are greatly desired by researchers in many biological disciplines. However, when imaging small animals such as invertebrates, the achievement of satisfactory spatial resolution and adequate contrast between tissues often requires the use of expensive and time-consuming procedures. Micro-X-ray-computed to...

The first step in understanding the properties of a specimen is to explore the configuration of materials (phases) using computer visualization. The most basic method is to traverse the data volume serially along user-defined two-dimensional cross sections, helping one to build a mental picture of the structure in the specimen. While still the most...

We describe a three-dimensional imaging and analysis study of eight industrial cellular foam morphologies. The foam morphologies were generated by differing industrial processing methods. Tomograms are acquired on an X-ray micro-computed tomography facility at scales of approximately equal to at resolutions down to 7 μm. The image quality is suffic...

A microcomputed tomography (muCT) facility and computational infrastructure developed at the Department of Applied Mathematics at the Australian National University is described. The current experimental facility is capable of acquiring 3D images made up of 20003 voxels on porous specimens up to 60 mm diameter with resolutions down to 2 mum. This a...

A reservoir carbonate core plug has been imaged in 3D across a range of length scales using high resolution X-ray microtomography (μ-CT). Data from the original 40-mm diameter plug was obtained at the vug scale (42 μm resolution) and allows the size, shape and spatial distribution of the disconnected vuggy porosity, ϕvug = 3.5% to be measured. With...

C17 Quantitative Mechanical and Transport Properties of Granular Systems Calculated from X-ray Tomography Images - Volume 20 Issue 2 - A. Sakellariou, T.J. Senden, T.J. Sawkins, M.A. Knackstedt, M.L. Turner, A.C. Jones, M. Saadatfar, A. Limaye, C.H. Arns, A.P. Sheppard, R.M. Sok

A fully integrated X-ray tomography facility with the ability to generate tomograms with 20483 voxels at 2 micron spatial resolution was built to satisfy the requirements of a virtual materials testing laboratory. The instrument comprises of a continuously pumped micro-focus X-ray gun, a milli-degree rotation stage and a high resolution and large f...

This paper illustrates the utility of micro-computed tomography (micro-CT) to study the process of tissue engineered bone growth. A micro-CT facility for imaging and visualising biomaterials in three dimensions (3D) is described. The facility is capable of acquiring 3D images made up of 2000(3) voxels on specimens up to 60mm in extent with resoluti...

A reservoir carbonate core plug has been imaged in 3D across a range of length scales using high resolution X-ray microtomography (µ-CT). Data from the original 40 mm diameter plug was obtained at the vug scale (42 µm resolution) and allows the size, shape and spatial distribution of the disconnected vuggy porosity, φvug = 3.5% to be measured. With...

This paper reports progress in the 3D pore-scale micro-CT imaging of multiple fluid phases during drainage experiments in porous materials. Experiments performed on a sintered monodisperse bead pack and a Berea sandstone sample are described. It is observed that the residual (trapped) wetting phase in the sintered bead pack is present as pendular r...

We demonstrate the capability of X-ray micro-computed tomography to image the micro-structure of human cortical bone. At voxel size we observe the complex morphology of the Haversian network in three dimensions. The local thickness of Haversian canals is measured using a maximal sphere algorithm and found to have a bimodal signature and a mean radi...

The field of mesoscale physics is concerned with length scales which lie in the sub-micron to millimetre range. As a subject, it covers complexity, disorder, cooperative effects and structure-property relationships. Much of modern material science can be found in this regime and it remains a rich ground for new research. As many of the phenomena as...

1] The use of seismic imaging techniques is widespread. Numerous three-dimensional (3-D) tomographic models have been presented over the last 30 years and subsequently analyzed by a wider community of seismologists, geodynamicists, mineral physicists, and geochemists. However, platform-independent, open source, user-friendly software for interactiv...

We illustrate some of the uses of micro-computed tomography (micro-CT) to study tissue-engineered bone using a micro-CT facility for imaging and visualizing biomaterials in three dimensions (3-D). The micro-CT is capable of acquiring 3D X-ray CT images made up of 20003 voxels on specimens up to 5 cm in extent with resolutions down to 2 m. This all...

A facility for digital imaging, visualizing and calculation of reservoir rock properties in three dimensions (3D) is described. The facility includes a high resolution X-ray micro-computed tomography system capable of acquiring 3D images made up of 20003 voxels on core plugs up to 5 cm diameter with resolutions down to 2 µm. Subsets of four sandsto...

A micro-CT facility for imaging, visualizing and calculat- ing sedimentary rock properties in three dimensions (3D) is described. The facility is capable of acquiring 3D X- ray CT images made up of 20003 voxels on core plugs up to 5 cm diameter with resolutions down to 2 μm. This allows the 3D pore-space of a rock to be imaged across several orders...

This paper describes features of UNIVIS-2000, an indigenously developed MS-WINDOWS-based package for physicists, chemists and mol. biologists interested in modeling medium-sized mols. and visualization of mol. scalar functions defined over a regular grid or on a variety of mol. surfaces. The code is written in C++ using freely available public doma...

Using quantum mechanical (QM) methods, we investigated the dependence of a number of factors on the polarization by the enzyme dihydrofolate reductase (DHFR) of its ligands—the substrates, folate and dihydrofolate, and the cofactor NADPH—and evaluated the implications for facilitation of the enzymic reductions. Two quite different levels of QM desc...

Using quantum mechanical (QM) methods, we investigated the dependence of a number of factors on the polarization by the enzyme dihydrofolate reductase (DHFR) of its ligands-the substrates, folate and dihydrofolate, and the cofactor NADPH-and evaluated the implications for facilitation of the enzymic reductions. Two quite different levels of QM desc...

We have investigated the importance of polarization by the enzyme dihydrofolate reductase (DHFR) on its substrates, folate and dihydrofolate, using a series of quantum mechanical (QM) techniques (Hartree-Fock (HF), Møller-Plesset second-order perturbation theory (MP2), local density approximation (LDA) and generalized gradient approximation (GGA) d...

We have investigated the importance of polarization by the enzyme dihydrofolate reductase (DHFR) on its substrates, folate and dihydrofolate, using a series of quantum mechanical (QM) techniques (Hartree-Fock (HF), Møller-Plesset second-order perturbation theory (MP2), local density approximation (LDA) and generalized gradient approximation (GGA) d...

Various binding sites in DNA bases and base pairs as predicted by rigorous analysis of the molecular electrostatic potential (MESP) are explored for coordination with Li+ and Ca2+ cations; the electrostatics is generally seen to provide an explanation for the observed trends in binding upon subjecting the anticipated structures to optimization at a...

A parallel algorithm for four-index transformation and MP2 energy evaluation, for distributed memory parallel (MIMD) machines is presented. The underlying serial algorithm for the present parallel effort is the four-index transform. The scheme works through parallelization over AO integrals and, therefore, spreads the O(n3) memory requirement acros...

A desktop PC-based graphics package, UNIVIS, for visualization of three-dimensional numerical data is described. Apart from routine molecular model visualization, the package provides for a host of other features such as extraction of various surfaces, planar cross-sections of the three-dimensional data, and property texturing. Fast rendering and t...

Ab initio calculations have been carried out on diacetylene-HF complexes both at the SCF and second-order Møller-Plesset level using a 6–31 + + G(d, p) basis set to determine the structures and association energies of the various possible forms of the complexes. The non-symmetric π complex has been found to be the most stable but the energy differe...

A method for synthesizing ab initio molecular electrostatic potential (MESP) and field (MEF) by ''stitching'' together suitably tailored smaller fragments is presented. The procedure is assessed for its ability to mimic the ab initio MESP and its topography for the model cases of zeolite silicon pentamer (Si5O16H12) and decamer (Si10O10H20) and has...

We present here a parallel algorithm for four‐index (integral) transformation and second‐order Møller–Plesset (MP2) energy evaluation, primarily designed for multiple instruction multiple data (MIMD) machines. It is a general algorithm designed to work with equal efficiency on any inhomogeneous network and any architecture. This algorithm works wit...

Parallelization of the SCF method for closed-shell molecules on the highly parallel transputer-based system PARAM is described. The parallelization has been implemented on three different hardware and software environments: (1) a network of bare 64 transputers; (2) configuration 1 plus a back-end file system (BFS); and (3) configuration 2 with one...

Evaluation of two-electron integrals forms a substantial part of the CPU time for any ab initio molecular orbital program. This part of the package, MICROMOL, is parallelized. However, this parallelization leads to only sublinear speedups (typically 3 on a 4-node machine). In view of these results, the task of development of an efficient program fo...

It is known that the molecular electron momentum density Γ(p) is inversion symmetric. In this article, the generalized repercussions of this fact on the symmetries of Γ(p) are discussed. A comprehensive study of the symmetry transformation from positional to momentum density due to the introduction of inversion operator i in the symmetry point grou...