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Periodic Solutions of a Delayed Population Model with One Predator and Two Preys
Rui Xu,M. A. J. Chaplain,F. A. Davidson 경북대학교 자연과학대학 수학과 2004 Kyungpook mathematical journal Vol.44 No.4
A delayed periodic Lotka-Volterra predator-prey model with one predator and two preys is investigated. By using Gaines and Mawhin’s continuation theorem of coincidence degree theory and by constructing appropr iate Lyapunov functionals, a set ofeasily veriable sufficient conditions are derived for the existence, uniqueness and global stability of positive periodic solutions to the model.
Lignin signatures of vegetation and soils in tropical environments
Belanger, E.,Lucotte, M.,Gregoire, B.,Moingt, M.,Paquet, S.,Davidson, R.,Mertens, F.,Passos, C.J.S.,Romana, C. Techno-Press 2015 Advances in environmental research Vol.4 No.4
The few lignin biomarker studies conducted in tropical environments are hampered by having to use references signatures established for plants and soils characteristic of the temperate zone. This study presents a lignin biomarker analysis (vanillyls (V), p-hydroxyls (P), syringyls (S), cinnamyls (C)) of the dominant plant species and soil horizons as well as an analysis of the interrelated terrigenous organic matter (TOM) dynamics between vegetation and soil of the $Tapaj{\acute{o}}s$ river region, an active colonization front in the Brazilian Amazon. We collected and analyzed samples from 17 fresh dominant plant species and 48 soil cores at three depths (0-5 cm, 20-25 cm, 50-55 cm) from primary rainforest, fallow forest, subsistence agriculture fields and pastures. Lignin signatures in tropical plants clearly distinguish from temperate ones with high ratios of Acid/aldehyde of vanillyls ((Ad/Al)v) and P/V+S. Contrary to temperate environments, similarly high ratios in tropical soils are not related to TOM degradation along with pedogenesis but to direct influence of plants growing on them. Lignin signatures of both plants and soils of primary rainforest and fallow forest clearly distinguish from those of non-forested areas, i.e., agriculture fields and pastures. Attalea speciosa Palm trees, an invasive species in all perturbed landscapes of the Amazon, exhibit lignin signatures clearly distinct from other dominant plant species. The study of lignin signatures in tropical areas thus represents a powerful tool to evaluate the impact of primary rainforest clearing on TOM dynamics in tropical areas.
'Looking into' chemical products and processes
Lynn F. Gladden,C. Buckley,P. S. Chow,J. F. Davidson,M. D. Mantle,J. Sederman 한국물리학회 2004 Current Applied Physics Vol.4 No.2-4
Nuclear magnetic resonance spectroscopy has long been established as a probe of the.A- and nm-scale chemistry and dynamics ofmolecules in the solid, glassy, gel, liquid and gas states. In the medical eld, the use of magnetic resonance imaging is now routineand will be found in most hospitals as a probe of the internal structure and blood ow within the human body. By bringing these two.families’ of magnetic resonance (MR) techniques together we have a powerful new set of tools with which to understand thefundamental physical and chemical processes that underpin our ability to formulate and manufacture materials with well-denedproperties. This article summarises some of the state-of-the-art developments and applications of MR techniques with particularapplication to obtaining new insights and strategies for controlling product properties through chemical process design. The use ofultra-fast MR techniques to study unsteady state multi-phase, multi-component processes is identied as oering exciting oppor-tunities in controlling properties during materials synthesis and subsequent processing.
R. Seetharam,Pagidi Madhukar,G. Yoganjaneyulu,S. Kanmani Subbu,M. J. Davidson 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.4
Mathematical models are among the new approaches employed to predict the properties of any material under various conditions. Mathematical models are essential for not only understanding the material properties but also estimating the costof design, product life, and failure criteria of the product. Therefore, in the current investigation, the hot deformation (HD)behaviour and microstructure alteration of deformed AA7150-5 wt% B4Ccomposite was studied through a mathematicalmodel. The new AA7150-5 wt% B4C composite was fabricated through an ultrasonic-probe assisted (20 KHz, 1000 W)stir casting process. The hot compression test was performed on a hydraulic press for various deformation temperatures(623–773 K) and strain rates (0.01–1 s−1). Based on the outcome, it is inferred that the flow stresses and microstructuresof AA7150-5 wt% B4Ccomposite was significantly altered during the hot compression test under various deformationconditions. The constitutive and dynamically recrystallized grain (DRXed) models were developed as a function of variousdeformation conditions of deformed AA7150-5 wt% B4Ccomposite, which was then applied to forecast the flow stress andgrain size behaviour for different deformation conditions. The flow stress and DRXed grain size were obtained through theproposed constitutive and DRXed models are correlated with experimental results, with excellent accuracy. The modelsdeveloped are reliable to predict the AA7150-5 wt% B4Cproperties for various conditions.
Collective Bands Built on the Proton h11/2 and the Neutron h11/2 Orbitals in Odd-odd I
C.-B. Moon,G. D. Dracoulis,R. A. Bark,A. P. Byrne,P. A. Davidson,A. N. Wilson,A. M. Baxter,T. Kib edi,G. J. Lane 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.43 No.I
The excited states of the doubly-odd 124I, 122I, and 120I nuclei have been studied by using in-beam gamma-ray spectroscopy with the 122Sn(7Li,5n), the 120Sn(7Li,5n), and the 118Sn(6Li,4n) reactions at Elab = 54, 58, and 48 MeV, respectively. Beams, which were pulsed on 1 ns separated by 1.7 s, were provided by the 14UD Pelletron accelerator at the Australian National University. In the present work, many collective bands with positive-parity as well as negative-parity have been newly identied and their excitation energies have been denitely established. The positive-parity collective bands built on the 10+ state in these doubly odd I could be interpreted as being associated with the h11=2h11=2 conguration.