194 research outputs found
Analisi agli elementi distinti e possibile evoluzione di un fronte di cava in calcari fratturati e carsificati.
No full textA highly configurable software bug tracking system
No full textThesis (S.B. and M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.Includes bibliographical references (p. 61-62).by Calista Tait.S.B.and M.Eng
On the suitability of phillipsite-chabazite zeolitite rock for ammonia uptake in water: a case study from the Pescara River (Italy)
No full textIonic exchange tests have been performed on superficial wastewaters to remove ammonia using a volcanic zeolitized rock from Lazio Region (Central Italy). The zeolitite (natural zeolite) is characterized by chabazite, phillipsite and minor amounts of sanidine, leucite and analcime. After preliminary column experiments in laboratory focused to determine the saturation time of the zeolitite, a pilot plant was built up on a little water course near the area of San Giustino channel (Abruzzo Region, Central Italy). Wastewaters, characterized by starting ammonia value ranging between 5 and 120 mg/l, were filtered with a zeolitic bed. The first experimental results indicate a positive ammonia reduction of about 80–90% and, in all cases, NH4+ concentration values under the EU law limits. A main purpose of this paper is to evidence that most of studies published on uptake of ammonia by means of zeolitite lead with clinoptilolite-dominant zeolitite despite the large and best performance of phillipsite-chabazite zeolites (up to 61–79% improvement of ammonia uptake). Last but not least, a large number of published studies are of difficult comparison because of poor characterization of the zeolitite used
Slope stability modelling of a sandstone cliff south of Livorno (Tuscany, Italy)
No full textThe landscape of the coast south of the town of Livorno (Tuscany, Italy) is characterized by sandstone headlands and sandy pocket beaches. Lithological features and physical-chemical processes favour many slope failures (mainly rock slides and rock falls) involving the sandstone cliffs and extending all over the cliff height; these failures often threaten people and facilities. The most prominent positive relief landform is structurally controlled by three main, closely spaced orthogonal joint sets. The presence of leaning and collapsed rock blocks suggests that continuous sea erosion and mass wasting maintain the cliff slopes steepness and risk conditions. The sandstone mechanical properties and fracture pattern have been investigated in order to determine the response of the rock mass to subaerial and marine stress. Hardness and weathering of the rocks were assessed using a Schmidt hammer and the Point Load Test, and statistical analysis was undertaken to remove outlying values. The sandstone outcrops were characterized according to the Bieniawski’s RMR and Romana’s Slope Mass Rating. Such data have been reported in a GIS system in order to determine the landslide susceptibility of the cliff. A series of stability analyses, with a Distinct Element Method (DEM) model, were carried out to evaluate stress and displacement distribution near the free surface of a vertical slope face, as a function of steepness, dip direction and rock mass quality. The results showed that assessing block geometry could provide an effective tool in predicting the rock-mass stability, determining the mechanism by which blocks fail from a vertical slope, and the consequent repetitive slope failures through time
Rock slope stability analysis on the complex Livorno coastal cliff (Tuscany, Italy)
No full textThe landscape of the south coast of Livorno city (Tuscany, Italy) is characterized by sandstone headlands and sandy pocket beaches affected by serious stability problems. Lithological features and physical-chemical processes involve many slope failures concerning the sandstone cliff and extending all over the cliff height; these failures often threaten people and facilities. The most prominent positive relief landform is structurally controlled by three main closely spaced joint sets. The presence of lean- ing and collapsed rock blocks suggests that erosion and mass wasting maintain the cliff steepness and elevate risk conditions. The sandstone mechanical properties and discontinuity pattern have been investigated in order to determine the response of the rock mass to subaerial and ma- rine stresses. The sandstone outcrops were characterized according to the Rock Mass Rating (Bieniawski, 1989) and the Slope Mass Rating (Ro- mana, 1985; 1993). Such data has been reported in a GIS system in order to determine the landslide susceptibility of the cliff. Some numerical modelling, with a code at Distinct Element Method model, were carried out to evaluate stresses and displacement distribution near the free sur- face of a steep slope face, as a function of steepness, dip direction and rock mass quality. Then some fall simulations were carried out, to make a back analysis of previous events and to obtain a more general outline of possible movements. The results showed that rock mechanics and com- puter modelling can be effective tools in predicting the rock-mass stabili- ty, determining the mechanism by which blocks fall from steep slopes and their possible trajectories
Un caso di cheyletiellosi. Quando il confronto tra dermatologi e veterinari è indispensabile. A case of cheyletiellosis. When between dermatologists and veterinarians is essential.
No full textGeomorphological features and 3D modelling of Montelparo mass movement (Central Italy).
No full textThe ancient village of Montelparo (Marche region, Central Italy) is affected by a large translational mass movement. The relief is modeled on arenaceous and arenaceous-pelitic units overlying pelitic-arenaceous terrains; the bedding strata form a gently dipping monocline. The translational slide is about 1100 m long and 500–700 m wide. The upper boundary between the stable area and the sliding mass is marked by a large active trench near the hilltop. The main sliding surface is located at a depth ranging between 65 and 100 m, in the politic-arenaceous unit. We studied the mechanism of the slope instability along the stratigraphic contact between a rigid arenaceous unit and an underlying ductile pelitic unit. The uncovering of the contact caused by the intense downcutting processes of the river at the hill foot during the Holocene, favoured the onset of the movement. This was enhanced by the fractured bedrock and especially by the jointing. We created a numerical model based on the finite differences code FLAC_3D by using a specific approach for mesh generation. The model suggests a further enlargement and deepening of the trench, and a sliding direction not aligned with the slope dip direction. Failure in the model concentrates at and around the main trench, all the other elements staying in an elastic state and inducing a rigid sliding. The model shows that both the failure onset and the current evolutionary state can be explained by the geological and static conditions of the slope
Slope stability modeling of a sandstone cliff south of Livorno (Tuscany, Italy).
No full textThe landscape of the coast south of the town of Livorno (Tuscany, Italy) is characterized by sandstone headlands and sandy pocket beaches. Lithological features and physical-chemical processes favour many slope failures (mainly rock slides and rock falls) involving the sandstone cliffs and extending all over the cliff height; these failures often threaten people and facilities. The most prominent positive relief landform is structurally controlled by three main, closely spaced orthogonal joint sets. The presence of leaning and collapsed rock
blocks suggests that continuous sea erosion and mass wasting maintain the cliff slopes steepness and risk conditions. The sandstone mechanical properties and fracture pattern have been investigated in order to determine the response of the rock mass to subaerial and marine stress. Hardness and weathering of the rocks were assessed using a Schmidt hammer and the Point Load Test, and statistical analysis was undertaken to remove outlying values. The sandstone outcrops were characterized according to the Bieniawski’s RMR and Romana’s Slope Mass Rating. Such data have been reported in a GIS system in order to determine the landslide susceptibility of the cliff. A series of stability analyses, with a Distinct Element Method (DEM) model, were carried out to evaluate stress and displacement distribution near the free surface of a vertical slope face, as a function of steepness, dip direction and rock mass quality. The results showed that assessing block geometry could provide an effective tool in predicting the rock-mass stability, determining the mechanism by which blocks fail from a vertical slope, and the consequent repetitive slope failures through time
Analytical modelling of temperature and vee length evolution in electric resistance welding
No full textThis report presents recent progress in understanding the physics of high frequency electric resistance welding (HF-ERW); in particular, the role of transient ablation which determines the duration a melt is exposed on the welding surfaces. The melt’s exposure to atmosphere typically results in pancake-type oxide inclusions usually called penetrators. Penetrators have been studied in ERW since the late 1970s; however, to date, industry does not have a quantitative model that links process parameters to penetrators. Since ERW is a continuous multi-physical process, understanding each of the occurring mechanisms is crucial to understand which ones contribute to penetrators. Fundamental to ERW is the heat distribution due to the currents imposed on the surfaces. This work presents the analytical derivation and solution of the solid-state temperature distribution in ERW as a single equation. From this analysis, the physical significance of heat penetration compared to the electrical skin depth is treated explicitly. At low temperatures, the skin depth predominates the heat penetration, whereas at higher temperatures the heat penetration predominates the skin depth. As material approaches the weld point, a molten film forms on the surfaces and is immediately expelled from the vee due to electromagnetic forces. The amount of expelled material directly affects the location of the weld point, the actual vee length in the process, and the propensity to form penetrators. The current ERW heat model has been revised to capture the effects of this transient ablation on actual vee length. As heat input increases, melting is induced earlier in the vee, resulting in an actual vee length larger than defined by system geometry. The model has been validated with published mill data from independent sources. Understanding the connection between process parameters and melt exposure is expected to elucidate the connection between process parameters and penetrators
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