538 research outputs found
Computing Multiscale Curve and Surface Skeletons of Genus 0 Shapes Using a Global Importance Measure
Epidemiological patterns of hepatitis B virus (HBV) in highly endemic areas
This paper uses meta-analysis of published data and a deterministic mathematical model of hepatitis B virus (HBV) transmission to describe the patterns of HBV infection in high endemicity areas. We describe the association between the prevalence of carriers and a simple measure of the rate of infection, the age at which half the population have been infected (A50), and assess the contribution of horizontal and perinatal transmission to this association. We found that the two main hyper-endemic areas of sub-Saharan Africa and east Asia have similar prevalences of carriers and values of A50, and that there is a negative nonlinear relationship between A50 and the prevalence of carriers in high endemicity areas (Spearman's Rank, P = 0·0086). We quantified the risk of perinatal transmission and the age-dependent rate of infection to allow a comparison between the main hyper-endemic areas. East Asia was found to have higher prevalences of HBeAg positive mothers and a greater risk of perinatal transmission from HBeAg positive mothers than sub-Saharan Africa, though the differences were not statistically significant. However, the two areas have similar magnitudes and age-dependent rates of horizontal transmission. Results of a simple compartmental model suggest that similar rates of horizontal transmission are sufficient to generate the similar patterns between A50 and the prevalences of carriers. Interrupting horizontal transmission by mass immunization is expected to have a significant, nonlinear impact on the rate of acquisition of new carriers
Design space exploration of a poultry fillet processing system using discrete-event simulation
Developments in the poultry processing industry, such as how livestock is
raised and how consumers buy meat, make it increasingly difficult to design
poultry processing systems that meet evolving standards. More and more
iterations of (re)design are required to optimize the product flow in these
systems. This paper presents a method for design space exploration of
production systems using discrete-event simulation. This method automates most
steps of design space exploration: iterating on the design, model construction,
performing simulation experiments, and interpreting the simulation results.
This greatly reduces the time and effort required to iterate through different
designs. A case study is presented which shows that this method can be
effective for design space exploration of poultry processing systems.Comment: FOODOPS 202
Robustness of Equations Under Operational Extensions
Sound behavioral equations on open terms may become unsound after
conservative extensions of the underlying operational semantics. Providing
criteria under which such equations are preserved is extremely useful; in
particular, it can avoid the need to repeat proofs when extending the specified
language.
This paper investigates preservation of sound equations for several notions
of bisimilarity on open terms: closed-instance (ci-)bisimilarity and
formal-hypothesis (fh-)bisimilarity, both due to Robert de Simone, and
hypothesis-preserving (hp-)bisimilarity, due to Arend Rensink. For both
fh-bisimilarity and hp-bisimilarity, we prove that arbitrary sound equations on
open terms are preserved by all disjoint extensions which do not add labels. We
also define slight variations of fh- and hp-bisimilarity such that all sound
equations are preserved by arbitrary disjoint extensions. Finally, we give two
sets of syntactic criteria (on equations, resp. operational extensions) and
prove each of them to be sufficient for preserving ci-bisimilarity.Comment: In Proceedings EXPRESS'10, arXiv:1011.601
Linearization of CIF Through SOS
Linearization is the procedure of rewriting a process term into a linear
form, which consist only of basic operators of the process language. This
procedure is interesting both from a theoretical and a practical point of view.
In particular, a linearization algorithm is needed for the Compositional
Interchange Format (CIF), an automaton based modeling language.
The problem of devising efficient linearization algorithms is not trivial,
and has been already addressed in literature. However, the linearization
algorithms obtained are the result of an inventive process, and the proof of
correctness comes as an afterthought. Furthermore, the semantic specification
of the language does not play an important role on the design of the algorithm.
In this work we present a method for obtaining an efficient linearization
algorithm, through a step-wise refinement of the SOS rules of CIF. As a result,
we show how the semantic specification of the language can guide the
implementation of such a procedure, yielding a simple proof of correctness.Comment: In Proceedings EXPRESS 2011, arXiv:1108.407
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