196,136 research outputs found
MDO techniques integrated with system modeling framework: MBSE methodologies applied to space system design and analysis
No full textThis paper presents the results of a research study related to the integration of a Design Optimization Framework in a Model Based System Engineering (MBSE) environment. The main aim of this work concerns the feasibility of such connection in order to assess actual advantages and possible drawbacks. The objective is to show how the Multidisciplinary Design Optimization (MDO) methods may be managed in the context of a MBSE environment with respect to the traditional design approach. Basically this analysis is addressed to the demonstration of the benefits of MBSE methodology in the field of aerospace engineering. The state of the art of the considered methodology is briefly introduced in the first part of the paper where also a survey on the role of MDO techniques is reported. The following part concerns the description of the modeling activities that have been used to define system characteristics. System data model is defined on the basis of MBSE paradigm and managed through a web application tool. In this section the focus is on the definition of conceptual relationships between the objects involved in the modeling activities. This part allows to assess how a web service can be used to support concurrent engineering activities. In the following part is described how a design optimization functionalities are integrated within the proposed framework to verify if possible advantages can be obtained. In particular the evaluation of framework benefits concerns mainly the management of system design variables and the possibility to trace their evolution throughout the design phase. A reference case referring is presented in the following section to show how the analyzed modeling tool can be used on a project development. The main aim of this study is to assess the feasibility of the considered approach for the management and support of engineering problems. Copyright (2013) by the International Astronautical Federation
Restauro, conservazione e valorizzazione di un insediamento fortificato alpino, con particolare riguardo alle tecniche edilizie in terra e pietra
No full textAnalysis of Costantino landslide dam evolution (Southern Italy) by means of satellite images, aerial photos, and climate data
No full textLarge landslides, triggered by earthquakes or heavy rainfall, often obstruct the river’s flow to form landslide dams, causing upstream inundations, and downstream flooding. In Italy, landslide dams are rather widespread along in Alps and Apennines: although the identification of past events is a complex task, some hundreds of landslide dams are identified in the literature. In order to assess the formation and evolution of landslide dams, several studies suggested the employment of geomorphological indexes. In this framework, the knowledge of site-specific time-space evolution can be useful in the understanding of the landslide dams phenomena. The present work focuses on a landslide dam that occurred in January 1973, which totally dammed the Bonamico River Valley (Southern Italy): the lake reached an area of about 175,000 m 2 , a volume of about 3.6 × 10 6 m 3 and a maximum depth of 40 m. During 1973-2008, the lake surface gradually decreased and nowadays it is completely extinct by filling. By using satellite and aerial images, the paper discusses the evolution of the lake surface and the causes of the lake extinction. The use of a climate index (i.e., standardized precipitation index at different time scale) indicates that in recent decades the alternance of drought and heavy rainfall periods affected the inflow/outflow dynamics, the filling of lake due to the solid transport of the Bonamico River, and the failure of the landslide dam
The fluvial dynamics of the Arno River - 4. Map of the morphological-sedimentary and human characteristics of the Arno river bed and alluvial plain (Table 7 “MONTEVARCHI”).
No full textThe results of a survey of the morphological-sedimentary and human characteristics of the Arno River bed and plain of the upper Valdarno, including the confluence of the Ambra Creek and St. Giovanni Valdarno, are reported by means of a thematic map at 1:10,000 scale. In this stretch, the river flows in an almost straight line with alternate side bars, within a plain having an average width of 1 to 2 kilometers. The present planimetric form of the river bed derives from the number of training works and canalisations undertaken in this section from the beginning of the 17th century, and which have caused, as the most visible consequence on the morphology of the course, a noticeable reduction in the width of the bankfull channel (from 300-500 metres to the present 150 metres), and the disappearance of interlacement, which was very frequent before 1700. During recent decades, the morphological and sedimentary characteristics of the river have been strongly influenced by intense gravel extraction, and by the construction of the artificial lakes of Levane and La Penna immediately upstream. These factors have certainly influenced the sedimentary equilibrium of the river, causing or encouraging erosive phenomena: the river is affected by a notable lowering of its bed, while the planimetric activity is very limited since there is hardly an erosion of the banks. The sedimentary bodies have a low mobility and a tendency to remain "suspended" with respect to the present level of the low waters. The sedimentary characteristics of the river bed are also considered in this paper and are graphically documented: the river is gravelly, with the average diameter of the material being between -3 and -6 phi. The bank protection works grant the river bed an elevated planimetric stability. On the other hand, the lowering process of the bed has made consolidation work on existing bridges necessary. The construction of a dam by E.N.E.L. has contributed to an altimetric fixation of the river bed bottom. The main aquifers present in the alluvial plain are distributed in correspondance to the coarse flood material, especially along the ancient river bed. Usually, the groundwater is affected by a field of motion which converges towards the river and which seems to be fed by them, except for local and temporary inversions of the groundwater-river relationships, especially in those areas with a greater water withdrawal. As far as the risk of flooding is concerned, this paper is limited to reporting the situation after the flood of November 4, 1966 (the maximum flow was reached in Montevarchi: 2,580 m^3/sec). On this occasion however, the tributaries caused the most damage. The flooded area of 1966 can only give us an indication of the areas which are more at risk of flooding should the same conditions repeat themselves, even if one must consider that some of the tributaries have undergone works of reinforcement, bridling and raising of the embankments. Only a few points of localised flooding have remained more or less unchanged, for example around bridges
Sexual dimorphism in the Moorish gecko (Tarentola mauritanica, Gekkota, Phyllodactylidae): body size and head shape characteristics
No full textTwo main adaptive hypotheses are invoked for the evolution of SD: sexual selection and natural selection. In snakes SD is generally interpreted as the adaptation of the two sexes to different ecological niches, whereas in lizards sexual and ecological causes may work simultaneously, with different outcomes according to taxonomic group. Surprisingly, geckos have been almost ignored in the general debate over the evolution of SD, despite their being an extremely diversified taxon with over 1300 species showing a wide range of variability in SD. The Moorish gecko is one of those species whose dimorphism is poorly studied. We took an integrated approach using a linear (biometrical) analysis on head and body size of 157 geckos and a relatively new analytical approach (geometric morphometry) to assess head size of 38 geckos from central Italy. Males were, on average, larger and heavier than females, and body size relationships differed between age classes showing a significant SD between sexes. When controlling for snout to vent length, sexes differed only in body mass and eye diameter (larger in males). Head shape, on the contrary, showed differences according to age classes, with deep differences in hatchlings compared to adults and, among adults, between sexes. However, the growth trajectories did not differ among sexes, and SD of head shape is probably due to a more prolonged growth of the males with respect to the females. The male-biased pattern of SD in this species is most parsimoniously interpreted as the result of sexual selection, whereby larger head and body size probably confer a greater advantage to males during combats and courtship, rather than conferring independent adaptations to different ecological pressures to each sex
The stream power variation in a GIS environment as an index to evaluate the most 'sensitive' points of a river
No full textThe note deals with the problem of measurement and variability, along the fluvial reaches of a hydrographic network, of the stream power, understood according to the definition originally provided by Bagnold (1966) “The available power supply, or time rate of energy supply, to unit lenght of a stream is clearly the time rate of liberation in kinetic form of the liquid’s potential energy as it descends the gravity slope S”. In formula: Ω = ρ g Q S
where: Ω = stream power per unit of flow length (W/m) ρ g = density x gravity acceleration = specific weight of the fluid (kg/m3) Q = liquid discharge (m3/s) S = slope of the considered reach (m/m). Recent digital elevation models allow the calculation of channel gradient and consequently stream power with a finer spatial resolution, opening promising and novel opportunities to investigate river geomorphological processes and forms. The work carried out consisted in defining and implementing a methodological approach that could be automated within a geographic information system and that meets two requirements: 1) use input data that is easy to find as DEM at a low resolution; 2) estimate, in the best possible way and on the basis of the available data, the stream power and its variability along the considered stream. In particular, the methodological approach has been implemented in the GIS environment (GRASS Gis, Qgis), and it has been applied to a sample basin, highlighting its variability along the streams of a higher order (in practice the main stream and its most important tributaries). The sudden and more substantial variations of stream power were then related to the processes acting in the fluvial system. This approach has made it possible to highlight how the erosion, solid transport and sedimentation phenomena occurring along the fluvial reaches (and the geomorphological and geological-applicative problems that these involve, especially in anthropized areas), are correlated precisely to abrupt variations (increase/decrease) of the ”power” available. Hence the idea that automated and standardized screening of stream power variability along a stream can be used as a preliminary diagnostic element to identify the most ”sensitive” points of the same, on which to concentrate subsequent investigations (field checks, to verify the causes), aimed at mitigating the risk due to the dynamics of the riverbed
Geotechnical Aspects in the Assessment of Stability Conditions of the Volumni Hypogeum in Perugia
No full textVolumni Hypogeum is part of the Palazzone Etruscan necropolis, an archaeological site dated back to Hellenistic period (V sec B.C.). The Hypogeum is a large underground cavity excavated in a partially saturated alluvial soil deposit located in the outskirts of Perugia city. Stability conditions and safety requirements of the vault and the lateral walls are analysed based on the available field results. The physical properties of the material in which the Hypogeum was excavated, such as, natural water content, soil suction, relative humidity of the rooms, temperature, as well as the groundwater conditions undoubtedly influence the state of conservation of the site itself. The variations of these properties may significantly affect the mechanical behaviour of the soil-materials and, in turn, the stability conditions of the ceiling/walls. Moreover, the site is daily exposed to road/rail traffic-induced vibrations. If also considering seismic actions, this site is extremely vulnerable. A multi-scale approach methodology has been recently undertaken aiming at the preservation and protection of the soil/monument system. The present study focuses on a very recent investigation of the microstructural features of the in situ materials. Preliminary numerical analyses of the cave have been performed in order to investigate on the stability conditions
Endogenous Crisis Waves: Stochastic Model with Synchronized Collective Behavior
No full textWe propose a simple framework to understand commonly observed crisis waves in macroeconomic agent-based models, which is also relevant to a variety of other physical or biological situations where synchronization occurs. We compute exactly the phase diagram of the model and the location of the synchronization transition in parameter space. Many modifications and extensions can be studied, confirming that the synchronization transition is extremely robust against various sources of noise or imperfections
Geomorphological map and main features of the area between Mt Fumaiolo and Valsavignone, Upper Tiber River Basin, central Italy | Carta e Lineamenti Geomorfologici dell'area compresa tra il M. Fumaiolo e Valsavignone (alto bacino del Fiume Tevere)
No full textViene proposta la cartografia degli elementi geomorfologici salienti della porzione più settentrionale del bacino del F. Tevere, al confine tosco-romagnolo. Lo studio è finalizzato alla definizione dei parametri che regolano la dinamica dei versanti e la dinamica fluviale ed alla identificazione delle tendenze evolutive di tale area, alla luce dell'importanza che riveste nella gestione e pianificazione territoriale per essere interessata, poco più a valle, dalla presenza di una delle dighe più importanti dell'Italia centrale, quella di Montedoglio (AR)
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