169,925 research outputs found
Prediction Method for the Surface Damage in Splined Couplings
No full textThe primary purpose of my PhD thesis was to develop design criteria and to verify procedures about fretting wear, that are applicable to crowned spline couplings of a power transmission system of the aeroengines. Fretting is a very complex phenomenon being influenced by many factors, the most important being the presence or absence of lubrication, the load distribution (contact pressure) and the sliding between the bodies. Therefore, the study of fretting needs a deep knowledge of these three main aspects. The first aspect of the problem was based on models and experimental tests considering specify specimens (crowned spline couplings) and imposed movements, so as to uniquely identify the working conditions (load and sliding), in order to facilitate the comparison between the experimental tests and the analytical models. The analytical models have been validated with numerical simulations and by comparison with experimental data, that have been obtained by means of a dedicated test bench that has been designed and built. Thanks to the test rig was possible to determinate the real contact pressure of two engaging teeth; in fact, it is one of the most important parameters affecting the fretting phenomenon, but it is very difficult to evaluate in a quantitative way, especially when considering components with complex geometries. The second phase of this thesis was the development of a predictive model for crowned splined couplings. This model is based on the Ruiz first parameter. The aim of my thesis is to demonstrate how this parameter may be correctly applied to a complex component as the crowned spline coupling, taking into account experimental and FEM validation
On the increasing size of the orogens moving from the Alps to the Himalayas in the frame of the net rotation of the lithosphere
No full textThe tectonic equator represents the great circle of the non-random mainstream of plate motions and it is inclined about 30° relative to the geographic equator. Divergence or convergence rates among plates are in average faster along the tectonic equator and they tend to decrease toward the polar areas. Moving from Western Europe to eastern Asia, the mainstream is roughly oriented southwest northeast. Here we show how this pattern may have played a role in determining the dimension of the Alpine-Himalayas orogenic belt, which is increasing in size and thickness moving from west-northwest to east-southeast, i.e., moving from high-latitude to low-latitude of the tectonic mainstream of plates. The Alps are in average 200–250 km wide, whereas the Himalayas are regularly > 1000 km wide. Moreover, due to the “westerly” polarization of the lithospheric mainstream relative to the mantle, either the net-rotation or the westward drift of the lithosphere, the subduction zones can be differentiated into two types, 1) increasing or 2) decreasing the lithospheric thickness. The Alpine-Himalayas system pertains to type 1 and it may represent a prototype of the continental lithosphere growth since the Archean. The increasing size of the orogens moving from the Alps to the Himalayas is presently concentrated in the northern hemisphere of the tectonic mainstream because subduction type 2 dominated the western margin of the Pacific ocean, hence preventing continental growth in the southern hemisphere in that longitude range. Therefore, the largest growth of continental crust and mantle lithosphere should have occurred along the tectonic equator, but only where type 1 subduction was generated
Inequalities in Consumption Patterns over the Life Cycle and the Great Recession
No full textThe aim of the study is to analyse the relationship between recession, population structure and consumption behaviour over the life cycle. To this aim, we consider three clusters of non-durable expenditures such as food at home, work-related and core expenditures. The analysis has been performed on micro data on the Household Budgets for the period 1997-2013. Based on life cycle theory, two statistical models has been estimated, viz. a pre-crisis (1997-2007) and a great recession period (2008-2013) model. The study shows that the recession has entailed a reduction of the average expenditure for each category of consumption, and the intensity of the reduction is different among households and generations
Asymmetric dynamics at subduction zones derived from plate kinematic constraints
No full textThe lithospheric sinking along subduction zones is part of the mantle convection. Therefore, computing the volume of lithosphere recycled within the mantle by subducting slabs quantifies the equivalent amount of mantle that should be displaced, for the mass conservation criterion. The rate of subduction is constrained by the convergence rate between upper and lower plates and the motion of the subduction hinge H that may either converge or diverge relative to the upper plate. Here, starting from the analysis of the slab hinge kinematics, we evaluate the subduction rate at 31 subduction zones worldwide, useful to compute volumes of sinking lithosphere into the mantle. Our results show that ∼190 km3/yr and ∼88 km3/yr of lithospheric slabs are currently subducting below H-divergent and H-convergent subduction zones, respectively. We also propose supporting numerical models providing asymmetric volumes of the subducted lithosphere, using the subduction rate instead of plate convergence, as boundary condition. Furthermore, H-divergent subduction zones appear to be coincident with subductions having “westward”-directed slabs, whereas H-convergent subduction zones are mostly compatible with those that have “eastward-to-northeastward”-directed slabs. On the basis of this geographical polarity, our lithospheric volume estimation gives ∼214 km3/yr and ∼88 km3/yr of subducting lithosphere, respectively. This entails that W-directed subduction zones contribute more than twice in lithospheric sinking into the mantle with respect to E-to-NE-directed ones. In accordance with the conservation of mass principle, this volumetric asymmetry in the mantle suggests a displacement of ∼120 km3/yr of mantle material from west to east, providing a constraint for global asymmetric mantle convection
Inequalities in Consumption Patterns over the Life Cycle and during the Great Recession
No full textThe aim of the study is to analyse the relationship between recession, population structure and consumption behaviour over the life cycle. To this aim, we consider three clusters of non-durable expenditures such as food at home, work-related and core expenditures. The analysis has been performed on micro data on the Household Budgets for the period 1997-2013. Based on life cycle theory, two statistical models has been estimated, viz. a pre-crisis (1997-2007) and a great recession period (2008-2013) model. The study shows that the recession has entailed a reduction of the average expenditure for each category of consumption, and the intensity of the reduction is different among households and generations
La sostenibilità ambientale del settore alberghiero - Il ruolo dei piani energetici regionali
No full textOpposite Kinematics, no Slab dip Vs Lithosphere age Correlation, and passive Behavior of Subduction zones
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Assessment of Sustainable Well-being in the Italian Regions: An Activity Analysis Model
No full textApplying the theoretical framework of productive analysis, the paper proposes an evaluation of regional sustainable well-being (SWB) in terms of efficiency. By means of an Activity Analysis Model (AA) (Färe et al., 1996), desirable and undesirable outcomes of development have been simultaneously used to evaluate the sustainable well-being of Italian regions. Data on equal and sustainable well-being provided by the Italian Statistical Office for the year 2010 has been used. The analysis reveals that only four regions achieve sustainable well-being, balancing socio-economic and environmental outcomes and resources. Finally, the study points out the advantages of AA for policy purposes by comparing it to a composite indicator of SWB
Commento all’art 51-bis “Obbligo del venditore di indicare la propria qualità” del nuovo Codice del Turismo
No full textIl contributo ha ad oggetto l'analisi ed il commento dell'art. 51-bis del nuovo Codice del Turismo (D.Lgs. 23 maggio 2011, n. 79), che prevede che il venditore di pacchetti o servizi turistici sia chiamato a rispondere quale organizzatore qualora ometta di trasmettere al viaggiatore, ai sensi dell’art. 34, il modulo di cui all’allegato A, parte II o parte III, c. tur., e di comunicare allo stesso le informazioni relative all’organizzatore del viaggio e al proprio ruolo di venditore.
Il contributo prende in esame il regime di responsabilità del venditore in caso di omessa informazione della propria qualità al viaggiatore e offre, inoltre, un approfondimento in merito alla questione relativa al rapporto tra responsabilità dell’organizzatore e responsabilità del venditore, al fine di valutare se sussista tra i due professionisti un vincolo di solidarietà passiva
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