7,525 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
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
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
Experimental and quantum chemical calculations on corrosion inhibition of mild steel by two furan derivatives
Two furan derivatives namely 5-methylfurfurylamine (MFA) and furfurylamine (FAM) were investigated as corrosion inhibitors for mild steel in 1 M HCl. The corrosion inhibition efficiencies (IE) were measured at 0.005M of the inhibitors using electrochemical potentiodynamic polarization measurements. The studied furan derivatives inhibit mild steel corrosion in acidic medium. The MFA shows higher inhibition efficiency of 84.77% compared to FAM of 41.75%. Quantum chemical calculations were performed at the B3LYP/6-311++G(d,p) level of density functional theory (DFT). Several quantum parameters were calculated to study the correlation between the molecular structures and the corrosion inhibition performance of the inhibitors. The MFA inhibitor shows higher HOMO energy, softness (S), fraction of electrons transferred (ÎN), and lower energy gap (ÎE) compared to the FAM. This result indicates a better corrosion inhibition performance of the MFA inhibitor. The results show that the calculated values of the quantum parameters using DFT calculations are consistent with the experimental findings
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
Behaviour and Design of Steel Box Columns In-Filled with Plain and Steel Fibre Reinforced Concrete under Centric and Eccentric Loads
Potential Liquid Fuel Savings from Crop Residue and High Sulfur Coal Combustion in Ohio, Indiana and Illinois
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