Search results for "init"
showing 10 items of 6629 documents
Geochemical mapping of magmatic gas–water–rock interactions in the aquifer of Mount Etna volcano
2001
Abstract Systematic analysis of major and minor elements in groundwaters from springs and wells on the slopes of Mt. Etna in 1995–1998 provides a detailed geochemical mapping of the aquifer of the volcano and of the interactions between magmatic gas, water bodies and their host rocks. Strong spatial correlations between the largest anomalies in pCO2 (pH and alkalinity) K, Rb, Mg, Ca and Sr suggest a dominating control by magmatic gas (CO2) and consequent basalt leaching by acidified waters of the shallow (meteoric) Etnean aquifer. Most groundwaters displaying this magmatic-type interaction discharge within active faulted zones on the S–SW and E lower flanks of the volcanic pile, but also in…
Analysis of the eigenfrequencies of the basalt machine parts by the FEM
2021
The aim of this paper was to carry out a theoretical (numerical) scientific research on the behavior of cast and recrystallized basalt, in order to use it as a material in the manufacture of structural elements of machine tools. A unitary methodology has been established for studying the eigenfrequency of structural elements for machine tools by the finite element method. Two basalt structural elements (beam type and plate type) were modeled, which were also made physically, and with the help of the COSMOS / Mark finite element program, the eigenfrequencies of the models was studied.
Low-pressure fractionation of the Nyiragongo volcanic rocks, Virunga Province, D.R. Congo
2004
Abstract A new petrogenetic model for the Nyiragongo volcanics based on petrological and geochemical studies of a wide range of highly alkaline and silica-undersaturated fractionated rocks (Mg# 23–44) invokes low-pressure fractionation occurring mainly within the Nyiragongo volcanic edifice. The most primitive Nyiragongo rocks seem correspond to a pyroxene-nephelinitic melt which evolved to melilite nephelinite and melilitite by fractionation of leucite, together with varying amounts of nepheline. Leucite nephelinite, leucitite and leucite tephrite represent rock types originating partly by phenocryst accumulation. Mineral and bulk rock geochemistry of pyroxene nephelinites indicate an alre…
Multiply Transitive Permutation Groups
1982
Since the beginnings of finite group theory, the multiply transitive permutation groups have exercised a certain fascination. This is mainly due to the fact that apart from the symmetric and alternating groups not many of them were known. Only very recently final results about multiply transitive permutation groups have been proved, using the classification of all finite simple groups (see 7.5).
Ab Initio Study of BiFeO3: Thermodynamic Stability Conditions
2015
BiFeO3 is investigated intensively, mainly as a multiferroic material. In this paper, the state-of-the-art ab initio hybrid functional approach with atomic basis sets was employed for a study of the stability range of BiFeO3 with respect to its decomposition into binary oxides and elementary metals, as a function of temperature and oxygen partial pressure. The calculated atomic and electronic structure of BiFeO3 was compared with previous LDA+U calculations using plane-wave basis sets. Based on performed calculations, the phase diagram was constructed, which allows us to predict the stability region of stoichiometric BiFeO3.
Theoretical study of stationary structures of acetamidine unimolecular decomposition
1990
Abstract The unimolecular decomposition of acetamidine to ammonia and acetonitrile was examined by ab initio methods. Stationary points, i.e. the reactant, product and transition structures, have been characterized. The process has an asynchronous mechanism, the transition state being described as a four-membered ring. To establish the relevance of different basis sets, calculations with eight standard Gaussian basis sets, STO-3G, 3-21G, 4-21G, 4-31G, 6-31G, 6-311G, 6-31G*, and G-31G**, were carried out.
Q-Chem 2.0: a high-performanceab initio electronic structure program package
2000
ABSTRACT: Q-Chem 2.0 is a new release of an electronic structure programpackage, capable of performing first principles calculations on the ground andexcited states of molecules using both density functional theory and wavefunction-based methods. A review of the technical features contained withinQ-Chem 2.0 is presented. This article contains brief descriptive discussions of thekey physical features of all new algorithms and theoretical models, together withsample calculations that illustrate their performance. c 2000 John Wiley S electronic structure; density functional theory;computer program; computational chemistry Introduction A reader glancing casually at this article mightsuspect on t…
Relay selection in FDD amplify-and-forward cooperative networks
2017
In this paper, the problems of relay selection and distributed beamforming are investigated for bi-directional dual-hop amplify-and-forward frequency-division duplex cooperative wireless networks. When using individual per-relay maximum transmission power constraint, it has been proven that the relay selection and beamforming optimization problem becomes NP hard and requires exhaustive search to find the optimal solution. Therefore, we propose a computationally affordable sub-optimal multiple relay selection and beamforming optimization scheme based on the l1 norm squared relaxation. The proposed scheme performs the selection for the two transmission directions, simultaneously, while aiming…
Influence of a thin horizontal weak layer on the mechanical behaviour of shallow foundations resting on sand
2021
The presence of minor details of the ground, including soil or rock masses, occurs more frequently than what is normally believed. Thin weak layers, shear bands, and slickensided surfaces can substantially affect the behaviour of foundations, as well as that of other geostructures. In fact, they can affect the failure mechanisms, the ultimate bearing capacity of footings, and the safety factor of the geotechnical system. In this research, numerically conducted through Finite Element Code Plaxis 2D, the influence of a horizontal thin weak layer on the mechanical behaviour of shallow footings was evaluated. The obtained results prove that the weak layer strongly influences both the failure me…
"Benjamin e Heidegger: dalla cesura al nuovo inizio Un confronto sul linguaggio poetico e l’esperienza del divino in Hölderlin", in www.syzetesis.it,…
2008
Nell’affrontare la riflessione benjaminiana Sul concetto di critica nel romanticismo tedesco, ripensando la nozione stessa di critica, irrompe prepotentemente il riferimento alla poesia di Hölderlin. L’interesse di Benjamin nei confronti di Hölderlin, maturato all’interno del circolo George-Kreis[1], è teso a individuare la linea di demarcazione tra mito e verità, stigmatizzando l’idea illusoria della vita come opera d’arte e sottraendo al poeta l’aura di “mitico eroe”, di depositario di un genio creativo. Per comprendere il modo in cui Benjamin intende affrontare la lettura di Hölderlin è necessario introdurre il concetto di ‘privo d’espressione’ – centrale nell’interpretazione benjaminian…