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Gradient estimates via two-point functions for parabolic equations under Ricci flow
No full texthttp://dx.doi.org/10.1017/S000497272000053
Assessing healthcare providers' performance with and without risk adjustment
No full texthttp://dx.doi.org/10.1017/S000497272000039
Axiomatisability of the class of monolithic groups in a variety of nilpotent groups
No full texthttp://dx.doi.org/10.1017/S000497271900163
On a close-to-convex analogue of certain starlike functions
No full texthttp://dx.doi.org/10.1017/S000497271900160
Comparing precipitation and temperature trends between inland and coastal locations
Get PDFMotivated by the Millennium Drought and the current drought over much of southern and eastern Australia, this detailed statistical study compares trends in annual wet season precipitation and temperature between a coastal site (Newcastle) and an inland site (Scone). Bootstrap permutation tests reveal Scone precipitation has decreased significantly over the past 40 years (p-value=0.070) whereas Newcastle has recorded little to no change (p-value=0.800). Mean maximum and minimum temperatures for Newcastle have increased over the past 40 years (p-values of 0.002 and 0.015, respectively) while the mean maximum temperature for Scone has increased (p-value = 0.058) and the mean minimum temperature has remained stable. This suggests mean temperatures during the wet season for both locations are increasing. Considering these trends along with those for precipitation, water resources in the Hunter region will be increasingly strained as a result of increased evaporation with either similar or less precipitation falling in the region. Wavelet analysis reveals that both sites have similar power spectra for precipitation and mean maximum temperature with a statistically significant signal in the two to seven year period, typically indicative of the El-Nino Southern Oscillation climate driver. The El-Nino Southern Oscillation also drives the Newcastle mean minimum temperature, whereas the Scone power spectra has no indication of a definitive driver for mean minimum temperature.
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A new linear and conservative finite difference scheme for the Gross–Pitaevskii equation with angular momentum rotation
No full textA new linear and conservative finite difference scheme which preserves discrete mass and energy is developed for the two-dimensional Gross–Pitaevskii equation with angular momentum rotation. In addition to the energy estimate method and mathematical induction, we use the lifting technique as well as some well-known inequalities to establish the optimal -error estimate for the proposed scheme with no restrictions on the grid ratio. Unlike the existing numerical solutions which are of second-order accuracy at the most, the convergence rate of the numerical solution is proved to be of order with time step and mesh size . Numerical experiments have been carried out to show the efficiency and accuracy of our new method.
doi:10.1017/S144618111900002
Three ways to compute multiport inertance
Get PDFThe immediate impulse-response of a confined incompressible fluid is characterized by inertance. For a vessel with one inlet and outlet, this is a single quantity; for multiple ports the generalization is a singular reciprocal inertance matrix which acts on the port-impulses to give the corresponding inflows. The reciprocal inertance coefficients are defined by the boundary fluxes of potential flows. Green's identity converts these coefficients to domain integrals of kinetic energy. For a system discretized with finite elements, a third method is proposed for computing reciprocal inertance coefficients which requires only the stiffness matrix and the solution vectors and no numerical differentiation.
References A. Asai. Bubble dynamics in boiling under high heat flux pulse heating. J. Heat Transf., 113(4):973–979, 1991. doi:10.1115/1.2911230. A. Asai. Three-dimensional calculation of bubble growth and drop ejection in a bubble jet printer. J. Fluids Eng., 114(4):638–641, 1992. doi:10.1115/1.2910079. G. K. Batchelor. An introduction to fluid dynamics. Cambridge University Press, 1967. doi:10.1017/CBO9780511800955. J. D. Beasley. Model for fluid ejection and refill in an impulse drive jet. Soc. Photogr. Sci. Eng., 21(2):78–82, 1977. F. Dorfler and F. Bullo. Kron reduction of graphs with applications to electrical networks. IEEE T. Circuits I, 60(1):150–163, 2013. doi:10.1109/tcsi.2012.2215780. A. Ern and J.-L. Guermond. Theory and practice of finite elements. Springer, 2004. doi:10.1007/978-1-4757-4355-5. K. Foster and G. A. Parker. Fluidics: Components and circuits. Wiley, 1970. URL https://www.worldcat.org/title/fluidics-components-and-circuits/oclc/138528. C. Geuzaine and J.-F. Remacle. Gmsh: A 3-D finite element mesh generator with built-in pre- and post-processing facilities. Int. J. Numer. Meth. Eng., 79(11): 1309–1331, 2009. doi:10.1002/nme.2579. G. Geymonat and D. Chenais. Introduction, Partial differential equations and functional analysis. Ed. by J. Cea, D. Chenai, pages xi–xii. Birkhauser, 1996. doi:10.1007/978-1-4612-2436-5. T. Gustafsson and G. McBain. kinnala/scikit-fem 0.1.17, Nov. 2018. O. Heaviside. Some remarks on the Volta force and seat of electro-motive forces questions, and on impressed force and potential in condenser circuits. J. Soc. Tele.-Eng. Electric., 14(57): 269–296, 1885. doi:10.1049/jste-3.1885.0014. H. E. Koenig, Y. Tokad, and H. K. Kesavan. Analysis of discrete physical systems. McGraw–Hill, 1967. URL https://trove.nla.gov.au/work/21368152?selectedversion=NBD2690879. M. Krizek and P. Neittaanmaki. Superconvergence phenomenon in the finite element method arising from averaging gradients. Numer. Math., 45(1):105–116, 1984. doi:10.1007/bf01379664. H. Lamb. Hydrodynamics. Cambridge University Press, 6th edition, 1932. URL https://www.cambridge.org/au/academic/subjects/mathematics/fluid-dynamics-and-solid-mechanics/hydrodynamics-6th-edition. G. D. McBain and S. G. Mallinson. Impulsively generated incompressible two-phase flow and the Asai thermal ink-jet model. In 21st Australasian Fluid Mechanics Conference, 2018. URL https://people.eng.unimelb.edu.au/imarusic/proceedings/21/Contribution_616_final.pdf. K. W. Oh, K. Lee, B. Ahn, and E. P. Furlani. Design of pressure-driven microfluidic networks using electric circuit analogy. Lab Chip, 12(3):515–545, 2012. doi:10.1039/c2lc20799k. H. F. Olson. Elements of acoustical engineering. Van Nostrand, 1948. doi:10.1002/sce.3730320378. R. S. Sanford. Physical networks. Prentice-Hall, 1965. URL https://trove.nla.gov.au/work/8815056?q&versionId=10200776. V. L. Streeter. Steady flow in pipes and conduits. In H. Rouse, editor, Engineering Hydraulics: Proceedings of the Fourth Hydraulics Conference, chapter 6, pages 387–443. Wiley, 1950. URL https://trove.nla.gov.au/work/17727563
Optimal investment and consumption with stochastic factor and delay
No full textWe analyse an optimal portfolio and consumption problem with stochastic factor and delay over a finite time horizon. The financial market includes a risk-free asset, a risky asset and a stochastic factor. The price process of the risky asset is modelled as a stochastic differential delay equation whose coefficients vary according to the stochastic factor; the drift also depends on its historical performance. Employing the stochastic dynamic programming approach, we establish the associated Hamilton–Jacobi–Bellman equation. Then we solve the optimal investment and consumption strategies for the power utility function. We also consider a special case in which the price process of the stochastic factor degenerates into a Cox–Ingersoll–Ross model. Finally, the effects of the delay variable on the optimal strategies are discussed and some numerical examples are presented to illustrate the results.
doi:10.1017/S144618111900001
A new approach to select the best subset of predictors in linear regression modelling: bi-objective mixed integer linear programming
No full textWe study the problem of choosing the best subset of features in linear regression, given observations. This problem naturally contains two objective functions including minimizing the amount of bias and minimizing the number of predictors. The existing approaches transform the problem into a single-objective optimization problem. We explain the main weaknesses of existing approaches and, to overcome their drawbacks, we propose a bi-objective mixed integer linear programming approach. A computational study shows the efficacy of the proposed approach.
doi:10.1017/S144618111800027
Finite unitary rings in which all Sylow subgroups of the group of units are cyclic
No full textDOI:
10.1017/S000497271900001