76 research outputs found
From coinductive proofs to exact real arithmetic: theory and applications
Based on a new coinductive characterization of continuous functions we
extract certified programs for exact real number computation from constructive
proofs. The extracted programs construct and combine exact real number
algorithms with respect to the binary signed digit representation of real
numbers. The data type corresponding to the coinductive definition of
continuous functions consists of finitely branching non-wellfounded trees
describing when the algorithm writes and reads digits. We discuss several
examples including the extraction of programs for polynomials up to degree two
and the definite integral of continuous maps
Probabilistic Bisimulation: Naturally on Distributions
In contrast to the usual understanding of probabilistic systems as stochastic
processes, recently these systems have also been regarded as transformers of
probabilities. In this paper, we give a natural definition of strong
bisimulation for probabilistic systems corresponding to this view that treats
probability distributions as first-class citizens. Our definition applies in
the same way to discrete systems as well as to systems with uncountable state
and action spaces. Several examples demonstrate that our definition refines the
understanding of behavioural equivalences of probabilistic systems. In
particular, it solves a long-standing open problem concerning the
representation of memoryless continuous time by memory-full continuous time.
Finally, we give algorithms for computing this bisimulation not only for finite
but also for classes of uncountably infinite systems
Orbits and phase transitions in the multifractal spectrum
We consider the one dimensional classical Ising model in a symmetric
dichotomous random field. The problem is reduced to a random iterated function
system for an effective field. The D_q-spectrum of the invariant measure of
this effective field exhibits a sharp drop of all D_q with q < 0 at some
critical strength of the random field. We introduce the concept of orbits which
naturally group the points of the support of the invariant measure. We then
show that the pointwise dimension at all points of an orbit has the same value
and calculate it for a class of periodic orbits and their so-called offshoots
as well as for generic orbits in the non-overlapping case. The sharp drop in
the D_q-spectrum is analytically explained by a drastic change of the scaling
properties of the measure near the points of a certain periodic orbit at a
critical strength of the random field which is explicitly given. A similar
drastic change near the points of a special family of periodic orbits explains
a second, hitherto unnoticed transition in the D_q-spectrum. As it turns out, a
decisive role in this mechanism is played by a specific offshoot. We
furthermore give rigorous upper and/or lower bounds on all D_q in a wide
parameter range. In most cases the numerically obtained D_q coincide with
either the upper or the lower bound. The results in this paper are relevant for
the understanding of random iterated function systems in the case of moderate
overlap in which periodic orbits with weak singularity can play a decisive
role.Comment: The article has been completely rewritten; the title has changed; a
section about the typical pointwise dimension as well as several references
and remarks about more general systems have been added; to appear in J. Phys.
A; 25 pages, 11 figures, LaTeX2
Numerical ModelâSoftware for Predicting Rock Formation FailureâTime Using Fracture Mechanics
Realâtime integrated drilling is an important practice for the upstream petroleum industry. Traditional
preâdrill models, tend to offset the data gathered from the field since information obtained prior to
spudding and drilling of new wells often become obsolete due to the changes in geology and geomechanics
of reservoirârocks or formations. Estimating the complicated nonâlinear failureâtime of a rock
formation is a difficult but important task that helps to mitigate the effects of rock failure when drilling
and producing wells from the subsurface. In this study, parameters that have the strongest impact on
rock failure were used to develop a numerical and computational model for evaluating wellbore
instability in terms of collapse, fracture, rock strength and failureâtime. This approach presents drilling
and well engineers with a better understanding of the fracture mechanics and rock strength failureprediction
procedure required to reduce stability problems by forecasting the rock/formation failuretime.
The computational technique built into the software, uses the stress distribution around a rock
formation as well as the rockâs responses to induced stress as a means of analyzing the failure time of
the rock. The results from simulation show that the applied stress has the most significant influence on
the failureâtime of the rock. The software also shows that the failureâtime varied over several orders of
magnitude for varying stressâloads. Thus, this will help drilling engineers avoid wellbore failure by
adjusting the stress concentration properly through altering the mud pressure and well orientation with
respect to inâsitu stresses. As observed from the simulation results for the failure time analysis, the
trend shows that the time dependent strength failure is not just a function of the applied stress.
Because, at applied stress of 6000â6050 psi there was time dependent failure whereas, at higher
applied stress of 6350â6400 psi there was no time dependent strength failure
Resting and feeding preferences of Anopheles stephensi in an urban setting, perennial for malaria
Background: The Indian city of Chennai is endemic for malaria and the known local malaria vector is Anopheles stephensi. Plasmodium vivax is the predominant malaria parasite species, though Plasmodium falciparum is present at low levels. The urban ecotype of malaria prevails in Chennai with perennial transmission despite vector surveillance by the Urban Malaria Scheme (UMS) of the National Vector Borne Disease Control Programme (NVBDCP). Understanding the feeding and resting preferences, together with the transmission potential of adult vectors in the area is essential in effective planning and execution of improved vector control measures. Methods: A yearlong survey was carried out in cattle sheds and human dwellings to check the resting, feeding preferences and transmission potential of An. stephensi. The gonotrophic status, age structure, resting and host seeking preferences were studied. The infection rate in An. stephensi and Anopheles subpictus were analysed by circumsporozoite ELISA (CS-ELISA). Results: Adult vectors were found more frequently and at higher densities in cattle sheds than human dwellings. The overall Human Blood Index (HBI) was 0.009 indicating the vectors to be strongly zoophilic. Among the vectors collected from human dwellings, 94.2% were from thatched structures and the remaining 5.8% from tiled and asbestos structures. 57.75% of the dissected vectors were nulliparous whereas, 35.83% were monoparous and the rest 6.42% biparous. Sporozoite positivity rate was 0.55% (4/720) and 1.92% (1/52) for An. stephensi collected from cattle sheds and human dwellings, respectively. One adult An. subpictus (1/155) was also found to be infected with P. falciparum. Conclusions: Control of the adult vector populations can be successful only by understanding the resting and feeding preferences. The present study indicates that adult vectors predominantly feed on cattle and cattle sheds are the preferred resting place, possibly due to easy availability of blood meal source and lack of any insecticide or repellent pressure. Hence targeting these resting sites with cost effective, socially acceptable intervention tools, together with effective larval source management to reduce vector breeding, could provide an improved integrated vector management strategy to help drive down malaria transmission and assist in India's plan to eliminate malaria by 2030
Effect of Kochia (Kochia indica) Plant Density on Yield and Some Physiological Characteristics of Sorghum under Salinity Stress
This study was carried out in two years, 2012 and 2013, to determine the effects of salinity and different kochia plant densities on yield and some physiological characteristics of sorghum (cv. Sepideh) at Salinity Research Center, National Salinity Research Center, Yazd, Iran. Treatments consisted of water salinity levels: 2 (control), 6, 10, and 14 dS m-1 of NaCl as main plots and different kochia (K. indica) densities: 0 (weed free sorghum, D0), 80 (D1), 60 (D2), and 40 (D3) cm between kochia plants on the sorghum row as sub plots. Results showed that at each salinity level, increase in kochia plant density was accompanied by reduction in sorghum dry matter, leaf area index and crop growth rate. Decreases in dry matter and leaf area index of sorghum due to kochia were more pronounced when grown at salinities of up to 6 dS m-1. Chlorophyll content index at 6, 10 and 14 dS m-1 were 23, 32 and 40% lower than the non-saline control. Increase in irrigation water salinity was accompanied by increase in canopy temperature. Canopy temperature of plants subjected to 14 dS m-1 of salt was higher than the non–stressed control by 13.6%. The weed free sorghum treatment had the highest canopy temperature. Therefore, it is necessary to control both salinity and Kochia indica to avoid meaningful decreases in sorghum yield
Effectivity of regular spaces
Abstract. General methods of investigating effectivity on regular Hausdorff (T3) spaces is considered. It is shown that there exists a functor from a category of T3 spaces into a category of domain representations. Using this functor one may look at the subcategory of effective domain representations to get an effectivity theory for T3 spaces. However, this approach seems to be beset by some problems. Instead, a new approach to introducing effectivity to T3 spaces is given. The construction uses effective retractions on effective ScottâErshov domains. The benefit of the approach is that the numbering of the basis and the numbering of the elements are derived at once.
Human Urogenital Myiasis Caused by Lucilia sericata(Diptera, Calliphoridae) and Wohlfahrtia magnifica (Diptera,Sarcophagidae) in Markazi Province of Iran
We report a case of human urogenital myiasis in an 86-year-old rural man with a penil ulcer and numerous alive and motile larvae from urethra and glans penis. Entomological studies on adult flies showed the larvae were Lucilia sericata and Wohlfahrtia magnifica. The clinical presentation and treatment strategies are discussed
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