•The authors present measurements at test rig of 12 pumps running as turbine.•The pump operating mode of these machines has been correlated to that as turbine.•A procedure selecting the best pump as ...turbine for a hydrological site is set up.•The procedure is recursive giving the possibility to refine the preliminary choice.•An exemplificative case study is illustrated with the aim to explain the procedure.
The use of hydraulic pumps running as turbines offers several advantages with respect to traditional turbines. The possibility of predicting the performances of a pump running as a turbine and of selecting the suitable machine for a given hydropower site, in an easy and reliable way, is a still open issue.
The present work makes a contribution to the solution of this subject both through experimental and theoretical activities. The experimental activity is carried out by the characterisation of 12 pumps measured, at test rig both in their natural operation, as pumps and in reverse mode, as turbines. The numerical activity starts from the definition of correlations regarding the heads and capacities conversion factors, useful for the preliminary selection of a suitable pump to run as turbine in a microplant for a given hydropower site. Then, a statistical method involving polynomials was implemented, allowing the performance curves to be provided. The agreement between experimental data and numerical results is comparable to that obtained by others authors.
Finally, a comprehensive procedure has been set up, refining the selection by evaluating likewise if the efficiency of the selected pump to use as a turbine, at operating point of the proposed plant, is acceptable.
The results related to a study case are shown with the aim to highlight the easiness of the proposed method, having in mind that it does not represent the generality of the possible applications of pumps running as turbines.
Single-molecule stretching experiments on DNA, RNA, and other biological macromolecules opened up the possibility of an impressive progress in many fields of life and medical sciences. The ...reliability of such experiments may be crucially limited by the possibility of determining the influence of the apparatus on the experimental outputs. Here we deduce a model that let us analytically evaluate such influence, fundamental for the interpretation of Single Molecule Force Spectroscopy experiments and intermolecular interactions phenomena. As we show, our model is coherent with previous numerical results and quantitively reproduce AFM experimental tests on titin macromolecules and P-selectin with variable probe stiffnesses.
A one-dimensional numerical code estimating the performances of centrifugal PATs (pumps used as turbines) is presented. Firstly, the code calculates the geometrical components of the PAT using ...information provided in manufacturer catalogues. Then, once these parameters are deduced, it calculates the losses and determines the characteristics curves of the PAT. The method was validated by comparing the theoretical curves with some experimental measurements acquired at the Department of Mechanical, Energy and Management Engineering (DIMEG) of the University of Calabria, at the Mechanical Propulsion National Centre (CNPM) in Milan and at the University of Trento (Italy) on PATs working in a range of specific speed from 9 to 65 rpm m3/4 s−1/2. The estimation error was comprised in a range of 5 ÷ 20%, generally acceptable for this kind of application.
•A model, predicting the performances of pumps used as turbines, has been presented.•The model recreates the geometry of the PAT starting from manufacturers catalogues.•The model calculates the curves head-capacity and efficiency-capacity.•The Best Efficiency Point (BEP) localisation is well calculated by the model.•The Williams indicator validates the model results better than other correlations.
SUMMARY
The separation of the effects of deep-seated sources of potential fields from those of shallower ones is a frequent requirement when interpreting magnetic or gravity fields. A common ...procedure is estimating the regional, long wavelength, component of the field by analysing the data over an area larger than that of the local feature of interest. The local components are found by subtracting the estimated regional from the observed data. These approaches may have difficulties in their application, as the dataset over large areas may not be available and other local anomalies, in the enlarged area, may prevent a reliable estimate of the regional field. We present an alternative and simple approach to the regional-residual separation problem not requiring the analysis over large areas and aiming at estimating the local, rather than the regional, component. Our method exploits the natural enhancement of short wavelengths obtainable by computing vertical derivatives of potential fields. An equivalent layer source is computed from the vertical derivative and is used to estimate the local field. The optimal differentiation order can be determined by inspecting the obtained results. This parameter may assume even fractional values, so that the method results a very versatile tool. The application to a complex synthetic case and two real data examples demonstrates the utility of this approach. In summary, our method has some peculiar characteristics making it an interesting alternative to currently used approaches to regional-residual separation: (i) it is a local method, so it can work well even when processing datasets relative to areas of limited extension; (ii) unlike most current methods, estimating a smooth regional component, our method directly produces an estimate of the local field and (iii) it is highly versatile, as the key parameter, that is the fractional differentiation order, can be finely adjusted up to obtain an optimal local field.
I propose a new method to estimate the morphology of the basement under sedimentary basins, starting from measured gravity or magnetic anomalies. The method is based on a simple relation existing ...between the depth to basement and gravity or pseudogravity fields. This simple relation (approximately linear for homogeneous sediment basins) is fitted by a polynomial regression, and the data can be immediately rescaled in terms of depth to the basement. The use of this method is possible when several depth constraints are available, such as wells perforating the basement or other geophysical data interpretations indicating the depth to basement at some locations. The first‐approximation model is iteratively improved by rescaling the misfit between the observed and the model‐generated field and by adding this correction to the first model. A further output of the method is the estimation of a constant density/magnetization contrast or of a depth‐density function. The method does not consider lateral variations in the basin fill density, nor variations in the basement magnetization. The method is demonstrated on a synthetic complex basement model in the cases of a constant density contrast, with or without noise, and in the case of a variable depth‐density function. The method is computationally very efficient, as it involves no matrix inversion nor multiplication. The applicability of the method to real gravity data is finally demonstrated by the modeling of the gravity anomalies of the Pannonian basin (Austria). The obtained model compares well to a previous interpretation of the same data using different constraints.
Key Points
A simple relation exists between the depth to basement and gravity or pseudo‐gravity fields
Based on this relation, a method is developed to recover the basement morphology under sedimentary basins and the density contrast function
The new method has been successfully applied to complex basement models and to a real data set
Ground-shaking phenomena in intermontane basins emplaced in seismically active areas are strongly affected by sediment thickness. There, the development of human settlements, encouraged because of ...the flat topography in a mostly mountainous region, implies demographic growth and an increased seismic risk, as recent earthquakes in Central Italy confirmed. The knowledge of the thickness of the basin infills and of their density distribution is critical for the ground-motion amplification analysis.
We apply the recently proposed ITerative RESCaling (ITRESC) method for 3D gravity modelling to the Middle Aterno Valley (Apennines, central Italy), a fault-controlled basin where a strong seismic activity recently occurred. Although the structural framework was previously investigated through 1D or 2D geophysical studies, here for the first time a full 3D model of the carbonate basement morphology is computed by the inversion of gravity data.
Differently from usual gravity modelling approaches, the ITRESC technique 1) does not assume a density contrast function, which is instead determined through a data-driven process, and 2) integrates geological or geophysical constraints to define a global “gravity/depth-to-basement” rescaling law, valid in all the investigated area.
Our model integrates a number of depth constraints of different nature while at the same time honoring the gravity anomalies. The obtained gravity model of the basement depth shows several analogies with previous studies, although with significant, localized discrepancies. The results of this study are only partially consistent with a structural evolution of the Middle Aterno Valley through a polyphasic sequence, as previously hypothesized.
•Gravity models of basement can be useful for seismic amplification studies.•A 3D gravity basement model of Middle Aterno Valley is computed by ITRESC method.•The gravity modelling did not assume the density contrast, which was instead estimated.•Results are consistent with a polyphasic structural evolution of the basin.
An optimization procedure for the optimal design of a trigenerative system to satisfy the energy needs of civil users is proposed. For the formulation of the mathematical model, it was necessary to ...refer to the class of MINLP (Mixed Integer Non Linear Programming Models), whose complexity is related to the presence of binary decision variables and to the non linear nature of the constraints. These constraints are required to model the variation of the nominal efficiency and of the plant unitary cost in relation to the size of the cogeneration plant, and to model the decrease of the nominal efficiency of the cogeneration plant in relation to load variation. Different plant alternatives (Simple Cycle Gas Turbine, Gas Micro-Turbine, Gas Internal Combustion Engine, Fuel Cells) in the optimization procedure are taken into account with the aim of determining the optimal typology, size and operative strategy of the trigeneration system.
•Optimization procedure for optimal design of a trigenerative system.•A Mixed Integer Non Linear Programming Model was formulated.•Non linear constraints were introduced to model the system main criticalities.•Different cogeneration plant alternatives were analyzed.
We analyze a wide gravity low in the Campania Active Volcanic Area and interpret it by a large and deep source distribution of partially molten, low-density material from about 8 to 30 km depth. ...Given the complex spatial-temporal distribution of explosive volcanism in the area, we model the gravity data consistently with several volcanological and petrological constraints. We propose two possible models: one accounts for the coexistence, within the lower/intermediate crust, of large amounts of melts and cumulates besides country rocks. It implies a layered distribution of densities and, thus, a variation with depth of percentages of silicate liquids, cumulates and country rocks. The other reflects a fractal density distribution, based on the scaling exponent estimated from the gravity data. According to this model, the gravity low would be related to a distribution of melt pockets within solid rocks. Both density distributions account for the available volcanological and seismic constraints and can be considered as end-members of possible models compatible with gravity data. Such results agree with the general views about the roots of large areas of ignimbritic volcanism worldwide. Given the prolonged history of magmatism in the Campania area since Pliocene times, we interpret the detected low-density body as a developing batholith.
A procedure for optimizing energy-management of a hospital complex is described, which, starting from hourly load diagrams, derived from the optimal design, allows the determination of the design and ...the running conditions of a trigeneration plant. The results obtained from the implementation of a mixed integer programming model, described here in detail, demonstrate how a trigeneration plant configuration utilizing heat pumps which are directly fed by a cogenerator, greatly improves energy-management, achieving significant economic, energy and environmental benefits.
We study the problem of adhesion and debonding of an elastic body interacting with a rigid substrate through a layer made of soft breakable adhesive material. The general problem is formulated in the ...multidimensional vectorial case, while a detailed analysis is carried for the one dimensional case leading to the study of a 1D semilinear wave equation. The initial boundary value problem is affected by the presence of a source term characterizing the interaction of the string withe the adhesive layer. This discontinuous force jumps to zero when a critical value of the displacement is reached. We obtain conditions for the initial boundary value problem ensuring the regularity of the solutions and the attachment–detachment conditions. Finally, we focus on a numerical investigation of the problem by considering regularizations of the source term and different initial conditions.
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