A multi-objective genetic algorithm optimisation using variable speed pumps in water distribution systems

Due to its practical importance and inherent complexity, the optimisation of distribution networks for supplying drinking water has been the subject of extensive study for the past 30 years. The optimization is governed by sizing the pipes in the water distribution network (WDN) and / or optimises specific parts of the network such as pumps, tanks etc. or try to analyse and optimise the reliability of a WDN. In this thesis, the author has analysed two different WDNs (Anytown City and Cabrera city networks), trying to solve and optimise a multi-objective optimisation problem (MOOP). The main two objectives in both cases were the minimisation of Energy Cost (€) or Energy consumption (kWh), along with the total Number of pump switches (TNps) during a day. For this purpose, a decision support system generator for Multi-objective optimisation used. Its name is GANetXL and has been developed by the Center of Water System in the University of Exeter. GANetXL, works by calling the EPANET hydraulic solver, each time a hydraulic analysis has been fulfilled. The main algorithm used, was a second-generation algorithm for multi-objective optimisation called NSGA_II that gave us the Pareto fronts of each configuration. The first experiment that has been carried out was the network of Anytown city. It is a big network with a pump station of four fixed speed parallel pumps that are boosting the water dynamics. The main intervention was to change these pumps to new Variable speed driven pumps (VSDPs), by installing inverters capable to diverse their velocity during the day. Hence, it’s been achieved great Energy and cost savings along with minimisation in the number of pump switches. The results of the research are thoroughly illustrated in chapter 7, with comments and a variety of graphs and different configurations. The second experiment was about the network of Cabrera city. The smaller WDN had a unique FS pump in the system. The problem was the same as far as the optimisation process was concerned, thus, the minimisation of the energy consumption and in parallel the minimisation of TNps. The same optimisation tool has been used (GANetXL).The main scope was to carry out several and different experiments regarding a vast variety of configurations, using different pump (but this time keeping the FS mode), different tank levels, different pipe diameters and different emitters coefficient. All these different modes came up with a large number of results that were compared in the chapter 8. Concluding, it should be said that the optimisation of WDNs is a very interested field that has a vast space of options to deal with. This includes a large number of algorithms to choose from, different techniques and configurations to be made and different support system generators. The researcher has to be ready to “roam” between these choices, till a satisfactory result will convince him/her that has reached a good optimisation point.

Il child language brokering a Ravenna e provincia: la parola agli studenti e ai professori

The main aim of this study is to provide a description of the phenomenon defined as Child Language Brokering (CLB), a common practice among language minority communities but which has received less attention in the academic literature. As the children of immigrants often learn the host language much more quickly than their parents, they contribute to family life by acting as language and cultural mediators between a family members and different language speakers. Many immigrant families prefer a language broker from within their own family to an external mediator or interpreter, even though there is a well-found resistance to the use of these young interpreters by professionals. In this study I report some findings from surveys of teachers in schools in Ravenna where there has been some use of students as CLBs and of students who have acted or are still acting as mediators for their families in different contexts, not only while at school. This dissertation is divided into five chapters. Chapter one aims at providing an overview of recent migration to Italy and of the differences between first-generation immigrants and second-generation immigrants. The chapter also discusses the available professional interpreting facilities provided by the municipality of Ravenna. Chapter two presents an overview of the literature on child language brokering. Chapter three provides a description of the methodology used in order to analyze the data collected. Chapter four contains a detailed analysis of the questionnaires administered to the students and the interviews submitted to the teachers in four schools in Ravenna. Chapter five focuses on the studies carried out by the researchers of the Thomas Coram Research Unit and University College London and draws a general comparison between their findings from on-line surveys of teachers in schools and my own findings on teachers’ points of view. The results of this study demonstrate that CLB is a common practice among immigrant children living in Ravenna and, although almost all students reported positive appreciation, further work is still needed to assess the impact of this phenomenon.

Development of a biorefinery scheme for the valorization of olive mill wastewaters and grape pomaces

In the Mediterranean area, olive mill wastewater (OMW) and grape pomace (GP) are among the major agro-industrial wastes produced. These two wastes have a high organic load and high phytotoxicity. Thus, their disposal in the environment can lead to negative effects. Second-generation biorefineries are dedicated to the valorization of biowaste by the production of goods from such residual biomasses. This approach can combine bioremediation approaches to the generation of noble molecules, biomaterials and energy. The main aim of this thesis work was to study the anaerobic digestion of OMW and GP under different operational conditions to produce volatile fatti acids (VFAs) (first stage aim) and CH4 (second stage aim). To this end, a packed-bed biofilm reactor (PBBR) was set up to perform the anaerobic acidogenic digestion of the liquid dephenolized stream of OMW (OMWdeph). In parallel, the solid stream of OMW (OMWsolid), previously separated in order to allow the solid phase extraction of polyphenols, was addressed to anaerobic methanogenic digestion to obtain CH4. The latter experiment was performed in 100ml Pyrex bottles which were maintained at different temperatures (55-45-37°C). Together with previous experiments, the anaerobic acidogenic digestion of fermented GP (GPfreshacid) and dephenolized and fermented GP (GPdephacid) was performed in 100ml Pyrex bottles to estimate the concentration of VFAs achievable from each aforementioned GPs. Finally, the same matrices of GP and not pre-treated GP (GPfresh) were digested under anaerobic methanogenic condition to produce CH4. Anaerobic acidogenic and methanogenic digestion processes of GPs lasted about 33 days. Instead, the anaerobic acidogenic and methanogenic digestion process of OMWs lasted about 121 and 60 days, respectively. Each experiment was periodically monitored by analysing volume and composition of produced biogas and VFA concentration. Results showed that VFAs were produced in higher concentrations in GP compared to OMWdeph. The overall concentration of VFAs from GPfreshacid was approximately 39.5 gCOD L-1, 29 gCOD L-1 from GPdephacid, and 8.7 gCOD L-1 from OMWdeph. Concerning the CH4 production, the OMWsolid reached a high biochemical methane potential (BMP) at a thermophilic temperature (55°) than at mesophlic ones (37-45°C). The value reached was about 358.7 mlCH4 gSVsub-1. In contrast, GPfresh got a high BMP but at a mesophilic temperature. The BMP was about 207.3 mlCH4 gSVsub-1, followed by GPfreshacid with about 192.6 mlCH4 gSVsub-1 and lastly GPdephacid with about 102.2 mlCH4 gSVsub-1. In summary, based on the gathered results, GP seems to be a better carbon source for acidogenic and methanogenic microrganism compared to OMW, because higher amount of VFAs and CH4 were produced in AD of GP than OMW. In addition to these products, polyphenols were extracted by means of a solid phase extraction (SPE) procedure by another research group, and VFAs were utilised for biopolymers production, in particular polyhydroxyalkanoates (PHAs), by the same research group in which I was involved.

Finite Element Modeling of Spiral Frequency Steerable Acoustic Transducers (FSATs) for guided waves based Structural Health Monitoring of plate-like structures

Structural Health Monitoring (SHM) is an emerging area of research associated to improvement of maintainability and the safety of aerospace, civil and mechanical infrastructures by means of monitoring and damage detection. Guided wave structural testing method is an approach for health monitoring of plate-like structures using smart material piezoelectric transducers. Among many kinds of transducers, the ones that have beam steering feature can perform more accurate surface interrogation. A frequency steerable acoustic transducer (FSATs) is capable of beam steering by varying the input frequency and consequently can detect and localize damage in structures. Guided wave inspection is typically performed through phased arrays which feature a large number of piezoelectric transducers, complexity and limitations. To overcome the weight penalty, the complex circuity and maintenance concern associated with wiring a large number of transducers, new FSATs are proposed that present inherent directional capabilities when generating and sensing elastic waves. The first generation of Spiral FSAT has two main limitations. First, waves are excited or sensed in one direction and in the opposite one (180 ̊ ambiguity) and second, just a relatively rude approximation of the desired directivity has been attained. Second generation of Spiral FSAT is proposed to overcome the first generation limitations. The importance of simulation tools becomes higher when a new idea is proposed and starts to be developed. The shaped transducer concept, especially the second generation of spiral FSAT is a novel idea in guided waves based of Structural Health Monitoring systems, hence finding a simulation tool is a necessity to develop various design aspects of this innovative transducer. In this work, the numerical simulation of the 1st and 2nd generations of Spiral FSAT has been conducted to prove the directional capability of excited guided waves through a plate-like structure.

Kinetic modeling for the synthesis of ethyl levulinate

This work is focused on studying the kinetics of esterification of levulinic acid in an isothermal batch reactor using ethanol as a reactant and as a protic polar solvent at the same time and in the presence of an acid catalyst (sulfuric acid). The choice of solvent is important as it affects the kinetics and thermodynamics of the reaction system moreover, the knowledge of the reaction kinetics plays an important role in the design of the process. This work is divided into two stages; The first stage is the experimental part in which the experimental matrix was developed by changing the process variables one at a time (temperature, molar ratio between reactants, and catalyst concentration) in order to study their influence on the kinetics; the second stage is using the obtained data from the experiments to build the modeling part in order to estimate the thermodynamics parameters.

WEC-Sim Application for the Assessment of Wave Energy Generation in the Tyrrhenian Sea and the North Sea Through the 2-Body Point Absorber (2BPA) and the Oscillating Surge Wave Energy Converter (OSWEC)

In recent years, developed countries have turned their attention to clean and renewable energy, such as wind energy and wave energy that can be converted to electrical power. Companies and academic groups worldwide are investigating several wave energy ideas today. Accordingly, this thesis studies the numerical simulation of the dynamic response of the wave energy converters (WECs) subjected to the ocean waves. This study considers a two-body point absorber (2BPA) and an oscillating surge wave energy converter (OSWEC). The first aim is to mesh the bodies of the earlier mentioned WECs to calculate their hydrostatic properties using axiMesh.m and Mesh.m functions provided by NEMOH. The second aim is to calculate the first-order hydrodynamic coefficients of the WECs using the NEMOH BEM solver and to study the ability of this method to eliminate irregular frequencies. The third is to generate a *.h5 file for 2BPA and OSWEC devices, in which all the hydrodynamic data are included. The BEMIO, a pre-and post-processing tool developed by WEC-Sim, is used in this study to create *.h5 files. The primary and final goal is to run the wave energy converter Simulator (WEC-Sim) to simulate the dynamic responses of WECs studied in this thesis and estimate their power performance at different sites located in the Mediterranean Sea and the North Sea. The hydrodynamic data obtained by the NEMOH BEM solver for the 2BPA and OSWEC devices studied in this thesis is imported to WEC-Sim using BEMIO. Lastly, the power matrices and annual energy production (AEP) of WECs are estimated for different sites located in the Sea of Sicily, Sea of Sardinia, Adriatic Sea, Tyrrhenian Sea, and the North Sea. To this end, the NEMOH and WEC-Sim are still the most practical tools to estimate the power generation of WECs numerically.

An optimal control tool for trajectory generation of autonomous drones

In the recent years, autonomous aerial vehicles gained large popularity in a variety of applications in the field of automation. To accomplish various and challenging tasks the capability of generating trajectories has assumed a key role. As higher performances are sought, traditional, flatness-based trajectory generation schemes present their limitations. In these approaches the highly nonlinear dynamics of the quadrotor is, indeed, neglected. Therefore, strategies based on optimal control principles turn out to be beneficial, since in the trajectory generation process they allow the control unit to best exploit the actual dynamics, and enable the drone to perform quite aggressive maneuvers. This dissertation is then concerned with the development of an optimal control technique to generate trajectories for autonomous drones. The algorithm adopted to this end is a second-order iterative method working directly in continuous-time, which, under proper initialization, guarantees quadratic convergence to a locally optimal trajectory. At each iteration a quadratic approximation of the cost functional is minimized and a decreasing direction is then obtained as a linear-affine control law, after solving a differential Riccati equation. The algorithm has been implemented and its effectiveness has been tested on the vectored-thrust dynamical model of a quadrotor in a realistic simulative setup.