1,720,976 research outputs found
The carbonate fraction in carbonatitic Italian lamprophyres
No full textAlkaline and ultramafic lamprophyres represent the majority of pre-Pleistocene alkaline mafic magmatic activity in Italy and have been described from several localities. The age of magmatism ranges from Triassic to Lower Oligocene. Some contain appreciable amounts of carbonate. The primary carbonate of the Italian carbonatitic lamprophyres is mainly Sr- or Mn-rich calcite that occurs mostly as immiscible ocelli or as groundmass. Its textural occurrence, composition, and relationship with co-precipitating silicate phases is taken as evidence of an igneous origin. Low BaO and REE contents in the carbonate are explained by early crystallization of essential mica and subordinate apatite. Whole rock analyses and isotopic data (Rukhlov, A.S., Bell, K., Vichi, G., Stoppa, F., submitted for publication. The heterogeneous deep mantle: the Sr, Pb and Nd isotopic evidence from Early Cretaceous alkaline lamprophyres of Southern Tuscany, Italy. Lithos.) suggest a mantle origin for these rocks and rule out contamination in either high or low pressure regimes. The bulk compositions of the carbonatitic lamprophyres have high HFSE / LILE and LREE / HREE ratios and although the abundances of these elements are generally lower than for carbonatites s.s., they are comparable with the abundances in other ‘carbonate-free’ Italian lamprophyres and Italian carbonatites, suggesting similar mantle sources. Moreover, the age of the Italian lamprophyres, ranging from Middle Triassic to Lower Oligocene, is much greater than the Pleistocene age of Italian carbonatites and indicates that the source remained similar over a long time span
Treatment of solar dermatitis with firocoxib in five dogs: clinical outcome and cyclossigenase isoform-2 expression
No full textA methodology for engine performance optimization
No full textDesign and optimization of intake and exhaust systems and valve timing is crucial in development of a naturally aspirated engine. Nowadays numerical simulation is a fundamental tool for this area. Unfortunately to perform an optimization of engine performance by setting even only a few parameters needs great effort in terms of time and engineering resources even with simple architecture engines.To overcome this problem the authors have developed an optimization methodology: the use of a 1_D simulation code allows one to build a neural network (NN) that characterizes engine working conditions for several input data variations (such as intake/exhaust systems and valve timing). A genetic algorithm (GA) coupled with the neural network is used to carry-out the multi-parameter optimization of engine performance. As an initial application, this methodology has been used for a 1-cylinder four stroke engine for off-road motorcycle application: inlet and exhaust valve phase angles were the input parameters and the maximum shaft power was the fitness function of the optimization process.In this paper the optimization methodology is described and the results of the above-mentioned initial application presented
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Large-scale gravity-driven structures: control on margin architecture and related deposits of a Cretaceous carbonate platform (Montagna della Maiella, Central Apennines, Italy).
No full textTreatment of solar dermatitis with firocoxib in five dogs: clinical outcome and cyclooxygenase isoform-2 expression
No full textNo abstract availabl
Acoustic characterization of automotive mufflers. Part II: validation of the numerical models by means of experimental data
No full textIncreasing interest is being paid to noise pollution of internal combustion engines and as a result, recent international standards imposed more severe limitations to acoustic emissions on engine manufacturers. In particular, the noise coming from gas-dynamic interactions has an important influence in determining the final noise level of the engine; as a consequence, the muffler design is currently being considered as one of the most important research threads for engine companies. Within this context, the 1D approach to numerical simulations, which has been successfully applied by industrial designers to the fluid-dynamic design of the engine, is considered to be inaccurate in the evaluation of the acoustic behavior of the muffler for medium-high frequencies. On the other hand, an extension of the applicability of these codes in the medium-high frequencies would be desirable. The direct advantage would be the use of the same software for the simulation of both the fluid-dynamic and acoustic performance of the engine.On these bases, a commercial 1D numerical code was primarily analyzed in terms of accuracy, computational cost and modeling capability of mufflers from the acoustic point of view. As a second step, two non-conventional approaches were developed in order to improve the prediction capabilities of the 1D code and to widen its frequency range of validity, as well. The base scheme of these new approaches was to extend the application of the traditional 1D nonlinear equations not only in the axial direction but also in perpendicular directions within the cross-section of the muffler, achieving a simplified description of the acoustic phenomena in the whole volume.The 1D predictions using these new approaches were compared both with several sets of experimental data collected on a purposefully developed test rig and specific 3D simulations; as a result, their limits in terms of accuracy were highlighted. Moreover, the introduction of the new sub-models increased the accuracy of the simulations and the frequency range of validity, leading to notable results with respect to traditional formulations of the problem
Acoustic characterization of automotive mufflers. Part I: test rig design and evaluation of acoustic properties
No full textIn current automotive research, increasing attention is being paid to the design of mufflers due to the lower noise levels which have been established by the acoustic international standards. The traditional design approaches are no longer sufficient to meet the standards and more refined techniques are necessary.Within this context, a specific test rig was built at the Energy Engineering Department of the University of Florence to analyze the acoustic characteristics of both industrial mufflers and simplified models. In particular, the latter is commonly used to investigate in detail the physical phenomena connected to the acoustic response of these disposals and to calibrate numerical models. The test rig operates at ambient condition with no flow. Instead of the widely used Four Microphones Technique, the test rig was designed considering the Multi-Microphone Technique, which guarantees a wider reliable frequency range of analysis and lower errors in the evaluation of the acoustic properties of mufflers. In this paper the details of the criteria adopted in the design and the characterization of the test rig will be discussed in depth
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