9,394 research outputs found
Structural setting and fluid dynamics in carbonate massifs of Umbria-Marche Apennines
No full textThe aim of this research is to understand the hydrogeological mechanisms of groundwater circulation and their relationship with the structural setting in carbonate massifs of Umbria-Marche Apennines. Karst aquifers are characterized by a strong heterogeneity in their physical properties. Hence, in order to define the dynamics of fluid circulation in these environments is necessary to integrate different investigative approaches.
Umbria-Marche carbonatic ridge is characterized by three hydrogeological complexes: a basal complex (Massiccio aquifer), an intermediate complex (Maiolica aquifer) and an upper complex (Scaglia aquifer). The carbonatic lithotypes covered about the 67% of the study area and only the 4.3% and 28.8% are represented by the Massiccio complex (the main aquifer of Apennine ridge) and Maiolica complex, respectively. On the contrary, the sub-basins showing higher percentage values of outcropping of Massiccio and Maiolica complexes. These results, indicate as the basal groundwater circulation is controlled exclusively by Massiccio and Maiolica complex.
Analysis of fracture systems exposed in different outcrops of Massiccio and Maiolica complexes, have defined a conceptual model of structural and hydraulic properties of the main aquifers. There are two main fracture sets oriented at SW-NE (dip-direction of N115) and NNE-SSW (dip-direction of N20), that probably the main pathways for the water-circulation from infiltration zone to spring outlet. Discrete Fracture Network (DFN) models of representative geocellar volumes builted to compute fracture porosity and correspondent permeability (Kxx, Kyy, Kzz), show that the fracture porosity of Calcare Massiccio Formation is much greater than Maiolica Formation (4.3% and 1.7%, respectively), and also the permeability values result well correlated with this trend.
From hydrogeological point of view, recession analysis and time series analysis (auto- and cross-correlation functions) applied at daily discharge of six karst springs highlighted the presence of two type of karst aquifers: aquifer with unimodal behaviour and aquifers with bimodal behaviour. These results indicate that Maiolica Formation is characterized by high fracturation degree and a slightly karstification, controlling the infiltration and percolation processes, whereas Calcare Massiccio Formation regulate the groundwater circulation in the deeper zones of aquifer characterized by a high karstification degree through a rather developed conduit networks
Questioni di tipologia diacronica nel dominio della diatesi
No full textObiettivo di questo articolo è illustrare il metodo della tipologia diacronica e i suoi limiti. L’analisi si concentrerà su due costruzioni che ricadono nel dominio funzionale della diatesi: gli antipassivi
e i passivi. Si illustreranno, innanzitutto, le più frequenti sorgenti diacroniche degli antipassivi individuate in un campione di 120 lingue, e si mostrerà che in alcuni casi la sorgente diacronica è in grado di spiegare alcune caratteristiche sincroniche di una specifica costruzione antipassiva. Sarà poi discusso il caso di alcune costruzioni passive che avrebbero origine da una nominalizzazione d’azione: questa ipotesi risulta, a un esame più attento, frutto di un miraggio, perché è più realistico ipotizzare che sia il passivo che la nominalizzazione d’azione derivino da un’ulteriore sorgente diacronica
Modelling of Electrodialysis with Bipolar Membranes processes using hybrid model supported by Artificial Neural Networks
No full textElectrodialysis with bipolar membranes appears to be a promising process for thesimultaneous production of acid and alkaline solutions. This process can be integratedinto circular economy approaches for waste streams valorisation or utilised alone,especially in remote areas, to reduce transportation, storage and handling of thesehazardous chemicals. However, there is a lack of information on large-scale units in realoperational environments, and, as a result, there are no validated modelling tools that canbe used for its design, optimisation, simulation and control. The aim of the present PhDthesis is to design and test a semi-industrial electrodialysis with bipolar membranes unitand develop versatile modelling tools that can be adopted for the above-mentionedapplication. The experimental investigation focused on evaluating well established andnew process configurations and operational schemes, as well as testing the process insidean integrated treatment chain to valorise a seawater brine. The collected data were utilisedto develop the modelling tools. Firstly, a model with a first principles approach wasobtained and validated to simulate large-scale units also with complex stack configuration(i.e., internal staging). The model was subsequently modified to account also fornonstationary operations. In addition, the possibility of adopting innovative modellingtools was considered. For the first time, artificial neural network models were used tosimulate the Electrodialysis with bipolar membranes process. Finally, the combination offirst principles and data-driven models was considered to develop innovative hybridmodels with superior performance compared to the two types of models used alone. Theobtained results can guide the selection of the most appropriate process configurationdepending on the applications, while the proposed models can be selected as realisabletools to predict the process behaviour depending on the application
Hydrostructural characterization of the karst reservoir in the Umbria-Marche Apennine, Italy
No full textIn carbonate reservoir, the flow patterns are conditioned by the degree of karsification of the main conduit networks and by the lower permeability microfractured blocks. To quantify patterns and nature of discontinuities in the rock mass is the main goal in the fluid circulation researches. Indeed fractures such as joint and bedding planes control infiltration, percolation and migration of groundwater into a reservoir. In the Umbria-Marche Apennine the Lower Jurassic limestones represents the basal reservoir where the larger hydrogeological structures are locate. The stratigraphic and structural setting forces a parallel-to-the ridge circulation of groundwaters, and the ridge itself can be considered as an isolated hydrogeological system. A quantitative fractures analysis was been considerate through the whole anticline, from the gently deep SW limb, in the weakly deformed hinge zone to the subvertical and much more deformed NE external side. The prevalent joint systems are oriented N55 and N295, located in the fold limbs and in the hinge zone. Besides, N15 and N345 joint systems are predominant only in western and eastern limbs of the anticline. In the hinge zone the fractures seem to be linked to a normal faults oriented at NW and SE, in correspondence of the crestal area; possibly these shear structures are responsible both for new systems development and for pre-existent sets partial reorientation. Dip discontinuities distribution gave remarkable about water process once infiltration inside the system. The high dips strongly contributed to increase groundwater percolation velocity coming both from direct infiltration areas in the upper hydrogeological complexes. Finally, spacing and frequency fracturation analysis identify rock mass properties from a quantitative point of view; these structural parameters allowed to obtained important considerations about both mechanical and hydrogeological features of a reservoir. The Giordano karst spring drains the SW limb of the M. Nerone anticline with an average discharge of more than 0,1 m3/sec and with a catchment area of about 4 km2. A deterministic approach for the hydrostructural characterization of the spring was adopted using discharge, temperature and water conductivity. The analysis of the hydrographs show that the base flow represent only the 30% and in the recession curve the discharge is controlled by the karst conduits drainage. The recession curves show different steps with a depletion constant of about 10-3 day-1, while the water temperature and electrical conductivity show variations where prevails the conduits drainage respect the fractured matrix. The complex variability and heterogeneity of the karst reservoir seems to be controlled by the larger karst conduits, which are related to the main fracture patterns
Heat as a tool for hydrodynamic characterization of fractured karst systems in Italy’s Northern Apennines
No full textCarbonate aquifers represent the main reservoir in the Apennines. The degree of their karstification controls the heterogeneity and anisotropy of the system at different scales. Bulk permeability of the karstified rock mass is controlled by a dual behavior, in which one end member is the conduit network with high hydraulic conductivity and short water-residence time, and the other is the microfractured blocks with longer water-residence times.
The geometry and the location of these flow paths in the study area are poorly constrained. An analysis of hydrographs integrated with the chemical or thermal responses can provide useful information on the geometries of the conduit drainages. A comparison of the thermal response of the karst springs with the record of cave stream temperatures will allow to distinguish between the conduit drainage and that of the fracture network. The spring hydrograph response is mainly controlled by the geometry of karst conduits and by the variation of the recharge area. Convective heat exchange in the channels and non-conservative thermal exchange between the water and the porous matrix characterize the flow in the whole karst system, as recorded by the heat output signals. The temperature signal in the conduits tends to be augmented by the high flow velocities, while being dampened by heat conduction resulting from the low flow velocities in fracture matrix. Using this information, the relationship between the system geometry and recharge area can be better defined.
The Scirca Spring is located at the foot of the Monte Cucco karstic massif in Italy’s Northern Apennines, where outcrops of Meso-Cenozoic carbonates are observable. The average discharge of the spring is about 0.2 m3/sec. It has a catchment area of about 3.4 km2 characterized by 30 km of karst conduits extending to a depth of about 1km. Several caves, in which underground streams feed the phreatic zone, allow to access the vadose zone of the drainage system. The karst aquifer was characterized by comparing the thermal behavior of the spring with that of the different cave streams as well as with the tracer test results and other physical-chemical data. The thermographs indicate a minimum of three fluctuation patterns, with hourly, daily and seasonal. The seasonal variations are out of phase with respect to the surface temperatures, showing a lag of many months. This data suggest a dampening effect exerted by the phreatic zone, in which the fracture network controls the main drainage and local inputs can modify the short term temperature signal
Groundwater Circulation in Fractured and Karstic Aquifers of the Umbria-Marche Apennine
No full textThe Umbria-Marche Apennine has a large number of springs that drain water stored in carbonate formations. Spring groundwater constitutes a crucial freshwater resource for many countries, regions, and cities around the world. This study aimed to understand the hydrological mechanisms behind groundwater circulation and their relationship to the structural and stratigraphic settings of specific aquifers. Recession analysis and time series analysis were applied to the daily discharge of six springs monitored over eight years. Both analyses indicated the presence of two types of aquifers: aquifer with unimodal behavior and aquifer with bimodal behavior. The first are characterized by two hydrodynamic sub-regimes, in which fracture networks control the baseflow and conduit networks control the quickflow. In contrast, other springs present only one hydrodynamic sub-regime related to fracture network drainage. Time series analysis confirms the results of recession analysis, showing a large memory effect and a large response time, implying the dominance of the baseflow sub-regime. These results indicate that the Maiolica Formation is characterized by a high degree of fracturation and slight karstification, which control infiltration and percolation, whereas the Calcare Massiccio Formation regulates groundwater circulation in the deeper zones of the aquifer, characterized by a high degree of karstification through moderately developed conduit networks
Nilpotent groups of semilinear transformations which are monomial
No full textLet H be a nilpotent subgroup of ΓL_n (q) = GL_n (q), where φ denotes the field automorfism induced by the Frobenius map. We give a condition on the primes dividing |H ∩ GL_n (q)| under which H is conjugate to a subgroup of the generalized monomial group Diag_n (F∗_q ) Sym(n).We show an application of this result to the determination of Carter subgroups of finite groups. </p
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