217,666 research outputs found
A mathematical model of the effect of a predator on species diversity
Mathematical model determines reaction between new predator and microbe competitor when the competitor is the predator's sole nutrient resource. The model utilizes differential equations to describe the interactions with the specific growth rates, and analyzes these growth rates as they are affected by population density and nutrient concentration
Navigating global-local tensions in accountability/autonomy policies: Comparative case studies in 'Asian' universities
The twin policy domains of accountability and autonomy have featured in recent education reforms in many countries, signalling new relationships between governments and educational institutions. Despite different national and localised contexts, a number of common 'global' trends have been identified. However, simultaneously context-specific differences are also evident. For us, the concept of 'globalisation', when it implies policy homogenisation, is too blunt an instrument to critically analyse these major reforms. We would argue that there are still too few studies on globalisation processes grounded in detailed examinations of particular historical times and geographical spaces. Our research is located within the tensions between global commonalities and localised differences.
This paper reports research on changing accountability and autonomy in higher education in three 'Asian' countries. Empirical data has been collected in the People's Republic of China, Hong Kong and Singapore in an attempt to begin to redress a 'Western' hegemony in such research. Within each national context two different types of universities became case study sites for the analysis of both commonalities and differences in accountability and autonomy policies and practices. The current paper focuses in particular on the conceptual and methodological framings of the research and presents some preliminary findings
Recursive Integral Method with Cayley Transformation
Recently, a non-classical eigenvalue solver, called RIM, was proposed to
compute (all) eigenvalues in a region on the complex plane. Without solving any
eigenvalue problem, it tests if a region contains eigenvalues using an
approximate spectral projection. Regions that contain eigenvalues are
subdivided and tested recursively until eigenvalues are isolated with a
specified precision. This makes RIM an eigensolver distinct from all existing
methods. Furthermore, it requires no a priori spectral information. In this
paper, we propose an improved version of {\bf RIM} for non-Hermitian eigenvalue
problems. Using Cayley transformation and Arnoldi's method, the computation
cost is reduced significantly. Effectiveness and efficiency of the new method
are demonstrated by numerical examples and compared with 'eigs' in Matlab
Stable embedded solitons
Stable embedded solitons are discovered in the generalized third-order
nonlinear Schroedinger equation. When this equation can be reduced to a
perturbed complex modified KdV equation, we developed a soliton perturbation
theory which shows that a continuous family of sech-shaped embedded solitons
exist and are nonlinearly stable. These analytical results are confirmed by our
numerical simulations. These results establish that, contrary to previous
beliefs, embedded solitons can be robust despite being in resonance with the
linear spectrum.Comment: 2 figures. To appear in Phys. Rev. Let
The longitudinal response function of the deuteron in chiral effective field theory
We use chiral effective field theory (EFT) to make predictions for the
longitudinal electromagnetic response function of the deuteron, f_L, which is
measured in d(e,e'N) reactions. In this case the impulse approximation gives
the full chiral EFT result up to corrections that are of O(P^4) relative to
leading. By varying the cutoff in the chiral EFT calculations between 0.6 and 1
GeV we conclude that the calculation is accurate to better than 10 % for values
of q^2 within 4 fm^{-2} of the quasi-free peak, up to final-state energies
E_{np}=60 MeV. In these regions chiral EFT is in reasonable agreement with
predictions for f_L obtained using the Bonn potential. We also find good
agreement with existing experimental data on f_L, albeit in a more restricted
kinematic domain.Comment: 33 pages, 10 figures. Accepted for publication in EPJA, with a few
further correction
Fragmentation or Recombination at High p_T?
All hadronization processes, including fragmentation, are shown to proceed
through recombination. The shower partons in a jet turn out to play an
important role in describing the p_T spectra of hadrons produced in heavy-ion
collisions. Due to the recombination of the shower partons with the soft
thermal partons, the structure of jets produced in AA collisions is not the
same as that of jets produced in pp collisions.Comment: Talk given at Quark Matter 200
Numerical solutions of 2-D multi-stage rotor/stator unsteady flow interactions
The Rai method of single-stage rotor/stator flow interaction is extended to handle multistage configurations. In this study, a two-dimensional Navier-Stokes multi-zone approach was used to investigate unsteady flow interactions within two multistage axial turbines. The governing equations are solved by an iterative, factored, implicit finite-difference, upwind algorithm. Numerical accuracy is checked by investigating the effect of time step size, the effect of subiteration in the Newton-Raphson technique, and the effect of full viscous versus thin-layer approximation. Computer results compared well with experimental data. Unsteady flow interactions, wake cutting, and the associated evolution of vortical entities are discussed
The order parameter of the chiral Potts model
An outstanding problem in statistical mechanics is the order parameter of the
chiral Potts model. An elegant conjecture for this was made in 1983. It has
since been successfully tested against series expansions, but as far as the
author is aware there is as yet no proof of the conjecture. Here we show that
if one makes a certain analyticity assumption similar to that used to derive
the free energy, then one can indeed verify the conjecture. The method is based
on the ``broken rapidity line'' approach pioneered by Jimbo, Miwa and
Nakayashiki.Comment: 29 pages, 7 figures. Citations made more explicit and some typos
correcte
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