7,602 research outputs found
Theoretical Calculations for the Acidity of Cyanopolyynes HC2n+1N (n = 0â5) in Gas and Aqueous Phases Using Ab initio Methods
Cyanopolyynes have been found in the interstellar medium, cold dust cloud Taurus Molecular Cloud-1, and the Titanâs atmosphere. Theoretical calculations are carried out to predict gas and aqueous phase acidities of a series of cyanopolyynes acids. Two levels of theory were used in this study, with the combination of density functional theory, and MĂžllerâPlesset perturbation (MP2) theory, MP2 methods with two types of basis set, namely, Popleâs 6â311++g (d, p) basis set and Dunningâs aug-cc-pVTZ basis set. The calculations of these molecules reveal that pKa values varying from 12.25 to 17.25 and indicate that the acidity of these molecules in aqueous phase increases whereas the acidity in gas phase decreases with an increasing chain length of these acids
Non Parametric Distributed Inference in Sensor Networks Using Box Particles Messages
This paper deals with the problem of inference in distributed systems where the probability model is stored in a distributed fashion. Graphical models provide powerful tools for modeling this kind of problems. Inspired by the box particle filter which combines interval analysis with particle filtering to solve temporal inference problems, this paper introduces a belief propagation-like message-passing algorithm that uses bounded error methods to solve the inference problem defined on an arbitrary graphical model. We show the theoretic derivation of the novel algorithm and we test its performance on the problem of calibration in wireless sensor networks. That is the positioning of a number of randomly deployed sensors, according to some reference defined by a set of anchor nodes for which the positions are known a priori. The new algorithm, while achieving a better or similar performance, offers impressive reduction of the information circulating in the network and the needed computation times
The NEG elements in clause structures
This article deals with the syntax of sentential negative elements in a
number of languages. We start by investigating three kinds of sentential
negative elements in Arabic. We argue that these elements occupy different
positions in the hierarchic order of clause structure. Negative elements
occur in positions higher than TNS, or between TNS and AG Rs, or project
internal to the Predicate Phrase. Analysis of Arabic negative clauses reveals
that although NEG elements project as phrasal heads, they are closely
associated with TNS and AGRs. We propose a hypothesis of Adjunction
movement to TNS/ NEG motivated by morphological requirement of the
elements involved. Movements, which should apply before Spell-out, are
necessary for Checking theory. The same procedure has been applied to
negative clauses in English, French, Italian, etc. We claim that sentential
NEG elements share in their essence certain simple properties at least in
the languages investigated here
Calculations of Energy Losses due to Atomic Processes in Tokamaks with Applications to the ITER Divertor
Reduction of the peak heat loads on the plasma facing components is essential
for the success of the next generation of high fusion power tokamaks such as
the International Thermonuclear Experimental Reactor (ITER) 1 . Many present
concepts for accomplishing this involve the use of atomic processes to transfer
the heat from the plasma to the main chamber and divertor chamber walls and
much of the experimental and theoretical physics research in the fusion program
is directed toward this issue. The results of these experiments and
calculations are the result of a complex interplay of many processes. In order
to identify the key features of these experiments and calculations and the
relative role of the primary atomic processes, simple quasi-analytic models and
the latest atomic physics rate coefficients and cross sections have been used
to assess the relative roles of central radiation losses through
bremsstrahlung, impurity radiation losses from the plasma edge, charge exchange
and hydrogen radiation losses from the scrape-off layer and divertor plasma and
impurity radiation losses from the divertor plasma. This anaysis indicates that
bremsstrahlung from the plasma center and impurity radiation from the plasma
edge and divertor plasma can each play a significant role in reducing the power
to the divertor plates, and identifies many of the factors which determine the
relative role of each process. For instance, for radiation losses in the
divertor to be large enough to radiate the power in the divertor for high power
experiments, a neutral fraction of 10-3 to 10-2 and an impurity recycling rate
of netrecycle of ~ 10^16 s m^-3 will be required in the divertor.Comment: Preprint for the 1994 APSDPP meeting, uuencoded and gzipped
postscript with 22 figures, 40 pages
Ăvolution temporelle de lâenvasement des retenues de barrages de Tunisie
La mobilisation et lâexploitation des eaux de surface sont des pratiques anciennes en Tunisie. Les amĂ©nagements rĂ©alisĂ©s au cours du siĂšcle dernier sont exposĂ©s Ă un alluvionnement plus ou moins accĂ©lĂ©rĂ©. La capacitĂ© de stockage des retenues des barrages est sujette Ă une rĂ©duction progressive au cours du temps. Cette perte de capacitĂ©, parfois Ă©levĂ©e, dĂ©passe les prĂ©visions de lâalluvionnement de la retenue. La quantification des sĂ©diments piĂ©gĂ©s se base soit sur les bilans de matiĂšre solide Ă lâĂ©chelle dâune retenue, soit sur des levĂ©s bathymĂ©triques ou topographiques. Les ModĂšles NumĂ©riques de Terrain (MNT) des retenues sont de plus en plus utilisĂ©s. Les diffĂ©rentes Ă©valuations sont entachĂ©es dâune incertitude. Les retenues des barrages tunisiens perdent annuellement 0,5 % Ă 1 % de leur capacitĂ© par alluvionnement. Lâanalyse des rĂ©sultats de mesures montre que lâalluvionnement est liĂ© Ă lâhydrologie du cours dâeau, Ă la gestion de la rĂ©serve dâeau et aux manoeuvres de dĂ©vasement. La comparaison entre les rĂ©sultats de mesures de lâalluvionnement et les prĂ©visions des projets met en Ă©vidence des diffĂ©rences parfois relativement importantes qui sont dues au rĂ©gime hydrologique des cours dâeau. En effet, une crue exceptionnelle peut provoquer un alluvionnement nettement supĂ©rieur Ă la moyenne annuelle en rĂ©gime hydrologique normal. Les retenues mĂ©andriformes sont comblĂ©es rapidement alors que les retenues linĂ©aires offrent la possibilitĂ© de soutirage de quantitĂ©s importantes de sĂ©diments. Les moyennes annuelles des pertes de capacitĂ© des barrages en exploitation et des barrages projetĂ©s jusquâĂ 2010 permettent de quantifier les volumes des sĂ©diments piĂ©gĂ©s Ă 500 Mm3. En 2030, la perte de capacitĂ© de stockage des barrages en exploitation pourrait atteindre 43 % de leur capacitĂ© initiale. Les amĂ©nagements amont et les travaux de conservation des eaux et des sols permettent de rĂ©duire le taux dâalluvionnement et de prolonger la durĂ©e de vie des grands rĂ©servoirs.The mobilization and exploitation of surface water are ancient practices in Tunisia. Installations carried out during last century are exposed to a greater or lesser degree of accelerated silting. The storage capacity of reservoirs is progressively reduced over the course of time. This sometimes accelerated loss of capacity of reserves by silting exceeds the forecasts of hydraulic installation projects. The quantification of trapped sediments is based on the assessment of a reservoirâs retained solid matter, either by bathymetric or topographic rising or by Digital Models of Grounds (DMG) corresponding to different dates. These various evaluations of the sediments trapped in reservoirs are, however, sullied with uncertainty. Tunisian reservoirs lose 0.5% to 1% of their storage capacity to silting annually. The analysis of the results presented in this study shows that silting is related to three factors: river hydrology, water reserve management and dredging operations. The comparison between the silting results and the project forecasts highlights relatively significant differences which may be due to river hydrology. Indeed a significant rising in water level can cause an increase in silting above the annual average found during normal hydrological modes. While meandering reservoirs are quickly filled with sediment, linear reservoirs can undergo dredging to remove a significant quantity of sediment. The annual averages in storage capacity losses of the dam under exploitation and its projections up to the year 2010 enable us to quantify the volumes of the sediment trapped as 500 Mm3. In 2030, the loss of storage capacity of the studied reservoirs may reach 43% of their initial storage capacities. Installations upstream and soil and water conservation efforts may reduce the rate of silting and prolong the lifespan of large dams
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