11,587 research outputs found
Roughness fluctuations, roughness exponents and the universality class of ballistic deposition
In order to estimate roughness exponents of interface growth models, we
propose the calculation of effective exponents from the roughness fluctuation
(sigma) in the steady state. We compare the finite-size behavior of these
exponents and the ones calculated from the average roughness for two
models in the 2+1-dimensional Kardar-Parisi-Zhang (KPZ) class and for a model
in the 1+1-dimensional Villain-Lai-Das Sarma (VLDS) class. The values obtained
from sigma provide consistent asymptotic estimates, eventually with smaller
finite-size corrections. For the VLDS (nonlinear molecular beam epitaxy) class,
we obtain alpha=0.93+-0.01, improving previous estimates. We also apply this
method to two versions of the ballistic deposition model in two-dimensional
substrates, in order to clarify the controversy on its universality class
raised by numerical results and a recent derivation of its continuous equation.
Effective exponents calculated from sigma suggest that both versions are in the
KPZ class. Additional support to this conclusion is obtained by a comparison of
the full roughness distributions of those models and the distribution of other
discrete KPZ models.Comment: 12 pages (4 figures included); to be published in Physica
Rethinking disaster risk management and climate change adaptation
AbstractAustralian governments face the twin challenges of dealing with extreme weather-related disasters (such as floods and bushfires) and adapting to the impacts of climate change. These challenges are connected, so any response would benefit from a more integrated approach across and between the different levels of government.This report summarises the findings of an NCCARF-funded project that addresses this problem.The project undertook a three-way comparative case study of the 2009 Victorian bushfires, the 2011 Perth Hills bushfires, and the 2011 Brisbane floods. It collected data from the official inquiry reports into each of these events, and conducted new interviews and workshops with key stakeholders. The findings of this project included recommendations that range from the conceptual to the practical. First, it was argued that a reconceptualization of terms such as ‘community’ and ‘resilience’ was necessary to allow for more tailored responses to varying circumstances. Second, it was suggested that the high level of uncertainty inherent in disaster risk management and climate change adaptation requires a more iterative approach to policymaking and planning. Third, some specific institutional reforms were proposed that included: 1) a new funding mechanism that would encourage collaboration between and across different levels of government, as well as promoting partnerships with business and the community; 2) improving community engagement through new resilience grants run by local councils; 3) embedding climate change researchers within disaster risk management agencies to promote institutional learning; and, 4) creating an inter-agency network that encourages collaboration between organisations.Please cite this report as: Howes, M, Grant-Smith, D, Reis, K, Bosomworth, K, Tangney, P, Heazle, M, McEvoy, D, Burton, P 2013 Rethinking disaster risk management and climate change adaptation, National Climate Change Adaptation Research Facility, Gold Coast, pp. 63.Australian governments face the twin challenges of dealing with extreme weather-related disasters (such as floods and bushfires) and adapting to the impacts of climate change. These challenges are connected, so any response would benefit from a more integrated approach across and between the different levels of government.This report summarises the findings of an NCCARF-funded project that addresses this problem.The project undertook a three-way comparative case study of the 2009 Victorian bushfires, the 2011 Perth Hills bushfires, and the 2011 Brisbane floods. It collected data from the official inquiry reports into each of these events, and conducted new interviews and workshops with key stakeholders. The findings of this project included recommendations that range from the conceptual to the practical. First, it was argued that a reconceptualization of terms such as ‘community’ and ‘resilience’ was necessary to allow for more tailored responses to varying circumstances. Second, it was suggested that the high level of uncertainty inherent in disaster risk management and climate change adaptation requires a more iterative approach to policymaking and planning. Third, some specific institutional reforms were proposed that included: 1) a new funding mechanism that would encourage collaboration between and across different levels of government, as well as promoting partnerships with business and the community; 2) improving community engagement through new resilience grants run by local councils; 3) embedding climate change researchers within disaster risk management agencies to promote institutional learning; and, 4) creating an inter-agency network that encourages collaboration between organisations. 
Evolution of microstructure, texture and grain boundary character distribution of potassium doped tungsten fibers annealed at variable temperatures
The effect of the annealing temperature on the microstructure and grain boundary character distribution of potassium doped tungsten fibers made of drawn wire was investigated by Electron Backscatter Diffraction. Samples, with a diameter of 148.7 μm, in the as-received condition and annealed at 1300, 1600, 1900, 2100 and 2300 °C were analyzed at the center of the transversal sections. Up to 1900 °C, a uniform microstructural coarsening and primary recrystallization followed by normal grain growth was observed. Between 1900 and 2100 °C abnormal grain growth took place. The strong texture (<110> parallel to the drawing axis) remained present in all conditions. With increasing the annealing temperature, the low angle grain boundary fraction increased at the expense of high angle grain boundaries while the amount of coincidence site lattice boundaries reached its maximum at 1600 °C. At this temperature, the most resistant configuration of triple junctions against intergranular crack propagation was obtained
Casein and soybean protein-based thermoplastics and composites as alternative biodegradable polymers for biomedical applications
This work reports on the development and characterization of novel meltable polymers and composites based on casein and soybean proteins. The effects of inert (Al(2)O(3)) and bioactive (tricalcium phosphate) ceramic reinforcements over the mechanical performance, water absorption, and ioactivity behavior of the injection-molded thermoplastics were examined. It was possible to obtain materials and composites with a range of mechanical properties, which might allow for their application in the biomedical field. The incorporation of tricalcium phosphate into the soybean thermoplastic decreased its mechanical properties but lead to the nucleation of a bioactive calcium-phosphate film on their surface when immersed in a simulated body fluid solution. When compounded with 1% of a zirconate coupling agent, the nucleation and growth of the bioactive films on the surface of the referred to composites was accelerated. The materials degradation was studied for ageing periods up to 60 days in an isotonic saline solution. Both water uptake and weight loss were monitored as a function of the immersion time. After 1 month of immersion, the materials showed signal of chemical degradation, presenting weight losses up to 30%. However, further improvement on the mechanical performance and the enhancement of the hydrolytic stability of those materials will be highly necessary for applications in the biomedical fieldPortuguese Foundation for Science and Tecnology (FCT), Ministry of Science and Tehnology, Portuga
Universality in two-dimensional Kardar-Parisi-Zhang growth
We analyze simulations results of a model proposed for etching of a
crystalline solid and results of other discrete models in the 2+1-dimensional
Kardar-Parisi-Zhang (KPZ) class. In the steady states, the moments W_n of
orders n=2,3,4 of the heights distribution are estimated. Results for the
etching model, the ballistic deposition (BD) model and the
temperature-dependent body-centered restricted solid-on-solid model (BCSOS)
suggest the universality of the absolute value of the skewness S = W_3 /
(W_2)^(3/2) and of the value of the kurtosis Q = W_4 / (W_2)^2 - 3. The sign of
the skewness is the same of the parameter \lambda of the KPZ equation which
represents the process in the continuum limit. The best numerical estimates,
obtained from the etching model, are |S| = 0.26 +- 0.01 and Q = 0.134 +- 0.015.
For this model, the roughness exponent \alpha = 0.383 +- 0.008 is obtained,
accounting for a constant correction term (intrinsic width) in the scaling of
the squared interface width. This value is slightly below previous estimates of
extensive simulations and rules out the proposal of the exact value \alpha=2/5.
The conclusion is supported by results for the ballistic deposition model.
Independent estimates of the dynamical exponent and of the growth exponent are
1.605 <= z <= 1.64 and \beta = 0.229 +- 0.005, respectively, which are
consistent with the relations \alpha + z = 2 and z = \alpha / \beta.Comment: 8 pages, 9 figures, to be published in Phys. Rev.
High-Temperature Series Analysis of the Free Energy and Susceptibility of the 2D Random-Bond Ising Model
We derive high-temperature series expansions for the free energy and
susceptibility of the two-dimensional random-bond Ising model with a symmetric
bimodal distribution of two positive coupling strengths J_1 and J_2 and study
the influence of the quenched, random bond-disorder on the critical behavior of
the model. By analysing the series expansions over a wide range of coupling
ratios J_2/J_1, covering the crossover from weak to strong disorder, we obtain
for the susceptibility with two different methods compelling evidence for a
singularity of the form , as predicted
theoretically by Shalaev, Shankar, and Ludwig. For the specific heat our
results are less convincing, but still compatible with the theoretically
predicted log-log singularity.Comment: 19 pages, 6 Postscript figure
Specific heat of two-dimensional diluted magnets
Using Monte Carlo techniques, the two-dimensional site-diluted Ising model is
studied. In particular, properties of the specific heat, its critical behaviour
and the emergence of a non-singular maximum above the transition temperature at
moderate concentration of defects, are discussed.Comment: 10 pages, 5 eps-figures, elsart-style, submitted to Physica
Scaling of local interface width of statistical growth models
We discuss the methods to calculate the roughness exponent alpha and the
dynamic exponent z from the scaling properties of the local roughness, which is
frequently used in the analysis of experimental data. Through numerical
simulations, we studied the Family, the restricted solid-on-solid (RSOS), the
Das Sarma-Tamborenea (DT) and the Wolf-Villain (WV) models in one- and two
dimensional substrates, in order to compare different methods to obtain those
exponents. The scaling at small length scales do not give reliable estimates of
alpha, suggesting that the usual methods to estimate that exponent from
experimental data may provide misleading conclusions concerning the
universality classes of the growth processes. On the other hand, we propose a
more efficient method to calculate the dynamic exponent z, based on the scaling
of characteristic correlation lengths, which gives estimates in good agreement
with the expected universality classes and indicates expected crossover
behavior. Our results also provide evidence of Edwards-Wilkinson asymptotic
behavior for the DT and the WV models in two-dimensional substrates.Comment: To appear in Surface Scienc
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