Curtin University

About: Curtin University is a education organization based out in Perth, Western Australia, Australia. It is known for research contribution in the topics: Population & Zircon. The organization has 14257 authors who have published 48997 publications receiving 1336531 citations. The organization is also known as: WAIT & Western Australian Institute of Technology.

Sumudu Transform - a New Integral Transform to Solve Differential Equations and Control Engineering Problems

Abstract: It is possible to solve differential equations, integral equations, and control engineering problems by a transformation in which the differentiation and integration of f(t) in the t-domain is made equivalent to division and multiplication of F(u) by u in the u-domain. The new transformation which is called the Sumudu transformation possesses many interesting properties which make the visualization of the transformation process easier to a newcomer. Some of the properties of the Sumudu transformation are: (1) The unit-step function in t-domain is transformed to unity in u-domain. (2) Scaling of f (t) in t-domain is equivalent to the scaling of F (u) by the same scale factor, and this is true even for negative scale factors. (3) The limit of f (t) as t tends to zero is equal to the limit of F (u) as u tends to zero. (4) The slope of f (t) at t=0 is equal to the slope of F (u) at u = 0. Thus u and F (u) are no longer dummies but can be treated as replicas of t and f (t) and can be expressed using same respective units, and therefore one can check the consistency of units of a differential equation even after the Sumudu transform.

Secondary students' mental models of atoms and molecules: Implications for teaching chemistry

Abstract: This interview-based study probed 48 Grade 8–10 students' mental models of atoms and molecules and found that many of these students preferred models that are both discrete and concrete. Modeling is a powerful skill that defines much of the scientific method; however, most younger science students have difficulty separating models from reality. Language that is common to both biology and chemistry (e.g., nucleus and shells) is a major source of confusion for some students. Several students concluded that atoms can reproduce and grow and that atomic nuclei divide. Electron shells were visualized as shells that enclosed and protected atoms, while electron clouds were structures in which electrons were embedded. These, and other alternative conceptions may be generated during discussion as a result of semantic differences between teacher and student language. Students expressed a strong preference for space-filling molecular models and their conceptions of the models used in chemistry reveal much about the difficulties that students face as they try to assimilate and accommodate scientific ideas, and terminology. It is recommended that teachers develop student modeling skills and that they discuss analogical models, including shared and unshared attributes, with their students. © 1996 John Wiley & Sons, Inc.

Stable prenucleation mineral clusters are liquid-like ionic polymers

Abstract: Calcium carbonate is an abundant substance that can be created in several mineral forms by the reaction of dissolved carbon dioxide in water with calcium ions. Through biomineralization, organisms can harness and control this process to form various functional materials that can act as anything from shells through to lenses. The early stages of calcium carbonate formation have recently attracted attention as stable prenucleation clusters have been observed, contrary to classical models. Here we show, using computer simulations combined with the analysis of experimental data, that these mineral clusters are made of an ionic polymer, composed of alternating calcium and carbonate ions, with a dynamic topology consisting of chains, branches and rings. The existence of a disordered, flexible and strongly hydrated precursor provides a basis for explaining the formation of other liquid-like amorphous states of calcium carbonate, in addition to the non-classical behaviour during growth of amorphous calcium carbonate.

Extracting powers and periods in a string from its runs structure

Abstract: A breakthrough in the field of text algorithms was the discovery of the fact that the maximal number of runs in a string of length n is O(n) and that they can all be computed in O(n) time. We study some applications of this result. New simpler O(n) time algorithms are presented for a few classical string problems: computing all distinct kth string powers for a given k, in particular squares for k = 2, and finding all local periods in a given string of length n. Additionally, we present an efficient algorithm for testing primitivity of factors of a string and computing their primitive roots. Applications of runs, despite their importance, are underrepresented in existing literature (approximately one page in the paper of Kolpakov & Kucherov, 1999). In this paper we attempt to fill in this gap. We use Lyndon words and introduce the Lyndon structure of runs as a useful tool when computing powers. In problems related to periods we use some versions of the Manhattan skyline problem.

Recrystallisation of oscillatory zoned zircon: some geochronological and petrological implications

Abstract: Oscillatory zoning is a common feature in zircons from acid igneous rocks and is believed to form during crystallisation of zircons from a magma by a mechanism which is not yet understood. Many zircons with oscillatory zoning also show a patchwork replacement of zoned by unzoned zircon. The unzoned zircon occurs as rounded, transgressive patches distributed throughout the zoned zircon and as areas of transitional replacement where zoned zircon is progressively replaced by unzoned zircon such that only faint traces of original zones remain. This structure is interpreted as a progressive recrystallisation of the oscillatory zoned zircon made unstable by the incorporation of high concentrations of contaminant elements during magmatic crystallisation. Recrystallisation overprints oscillatory zones and appears to have occurred after completion of primary crystallisation. It is accompanied by loss of U, Th and Pb and the removal of oscillatory zones. The recrystallised unzoned zircon is extremely stable with respect to later Pb loss and tends to retain a concordant or slightly discordant U−Pb age. Recrystallisation provides a mechanism for resetting zircon U−Pb ages which is independent of the degree of radiation damage of the zircon lattice. This differs from other models of discordance which involve a leaching of radiogenic Pb as a consequence of a progressive breakdown of the zircon structure through time-integraded radiation damage further enhanced by high concentrations of trace-element contaminants. The U−Pb age of the unzoned zircon may date the recrystallisation event, which may be close to the age of primary crystallisation or reflect a later metamorphism.