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Antibacterial properties of bioactive materials functionalized with silver nanoparticles and plant-derived biomolecules to minimize implant infections
No full texttitanium and its alloys have developed into key materials for biomedical applications owing to their biocompatibility with human tissues and excellent mechanical properties. Unmodified titanium is susceptible to microbial infections that might lead to implant failure and devastating complications with high morbidity and treatment costs. An effective approach to minimize microbial contamination on implant surfaces is to modify the biomaterial surface chemistry in order to reduce adhesion and biofilm development by microorganisms. The aim of this research was to evaluate the antibacterial activities of bioactive titanium alloy Ti6Al4V, functionalized with silver nanoparticles or the innovative Mentha piperita (MP) essential oil, both recognized for strong antimicrobial propertie
Design, Test and Identification of an Active Aerostatic Thrust Bearing with a Compliant Mechanism and Piezo Actuator
No full textAerostatic thrust bearings are currently used in applications where high accuracy is required, e.g., in machine tools, measuring instruments, manufacturing and medical equipment. Their appeal is due to the absence of contact between their moving and stationary parts, which ensures relative motions characterised by low friction, low wear and limited heat generation. However, in some operating conditions, these systems may present low specific stiffness and be subject to instability. This thesis presents the design, modelling and testing of an actively compensated aerostatic thrust bearing. A support compensation strategy has been adopted as an active compensation method. The support compensation method consists in integrating conventional passive bearings with piezoelectric actuators which make it possible to compensate for variations in the bearing position. This compensation is obtained by exploiting changes in the stroke of the actuators and makes it possible to enhance both the static and the dynamic bearing performance. This integration has been possible thanks to the presence of a compliant mechanism which gives a directional guide to and opportunely pre-loads the actuator. Preliminary experimental tests have consisted in a "classical" static characterisation of the bearing where the load, air consumption and stiffness of the bearing have been obtained. Moreover, concerning the design of bearings, their dynamic performance is becoming a crucial aspect, due to the continual demand for higher performance from today's applications. For this reason, a dynamic linear time-invariant model of the system has been proposed. Here, the linear approximation is made by presuming that around each operating condition the system motion may be considered as an equilibrium state, and the bearing is modelled as a SDOF system because of the physical constraints imposed. The model validation has been performed with the aid of step force and tracking tests. Step force tests have been firstly carried out to dynamically characterise the bearing in its passive configuration (without the automatic control) by utilising and comparing the Logarithmic Decrement and the Half Power Bandwidth methods. Secondly, step force tests have also been used to assess the capacity of compensation of the active bearing (with the automatic control). On the other hand, tracking tests have been performed to verify the positional accuracy of the bearing and assess its bandwidth. Results demonstrate both the effectiveness of the prototype and the sound of the adopted mathematical model
Preserving the Benefits of Open Government Data by Measuring and Improving Their Quality: An Empirical Study
No full textContext: Open Government Data (OGD) represent an invaluable resource for enabling active citizenship. A significant example is represented by the mandatory data that Italian public administrations (PAs) are required to publish concerning their contracts. Nevertheless, a low quality of data provided by PAs could hamper the prospect of citizen involvement. Goal: Our objective is to define a set of basic metrics for public contracts OGD on the basis of the ISO SQuaRE standards family, with the goal of enabling the automated evaluation of dataset quality. Method: We started with the metrics defined in the ISO 25024 standard and adapted them to the data schema of the OGD under evaluation. We assessed the results by looking at the issues revealed by the metrics applied to the data released by a pool of PAs. Results: We were able to define a set of metrics, and apply them to to the datasets released by 12 distinct organizations. The metrics allowed us to identify several quality issues that limit the reuse of OGD from the citizen perspective. Conclusions: The metrics we develop are able to identify quality issues and are suitable to perform an initial automated assessment of OGD datasets. This exercise also support the generality of the ISO 25024 quality measures
Content Recommendation Through Linked Data
No full textNowadays, people can easily obtain a huge amount of information from the Web, but often they have no criteria to discern it. This issue is known as information overload. Recommender systems are software tools to suggest interesting items to users and can help them to deal with a vast amount of information. Linked Data is a set of best practices to publish data on the Web, and it is the basis of the Web of Data, an interconnected global dataspace. This thesis discusses how to discover information useful for the user from the vast amount of structured data, and notably Linked Data available on the Web. The work addresses this issue by considering three research questions: how to exploit existing relationships between resources published on the Web to provide recommendations to users; how to represent the user and his context to generate better recommendations for the current situation; and how to effectively visualize the recommended resources and their relationships. To address the first question, the thesis proposes a new algorithm based on Linked Data which exploits existing relationships between resources to recommend related resources. The algorithm was integrated into a framework to deploy and evaluate Linked Data based recommendation algorithms. In fact, a related problem is how to compare them and how to evaluate their performance when applied to a given dataset. The user evaluation showed that our algorithm improves the rate of new recommendations, while maintaining a satisfying prediction accuracy. To represent the user and their context, this thesis presents the Recommender System Context ontology, which is exploited in a new context-aware approach that can be used with existing recommendation algorithms. The evaluation showed that this method can significantly improve the prediction accuracy. As regards the problem of effectively visualizing the recommended resources and their relationships, this thesis proposes a visualization framework for DBpedia (the Linked Data version of Wikipedia) and mobile devices, which is designed to be extended to other datasets. In summary, this thesis shows how it is possible to exploit structured data available on the Web to recommend useful resources to users. Linked Data were successfully exploited in recommender systems. Various proposed approaches were implemented and applied to use cases of Telecom Italia
Optimal Power Sharing between Photovoltaic Generators, Wind Turbines, Storage and Grid to Feed Tertiary Sector Users
No full textA paramount technical drawback of photovoltaic (PV) and wind power systems is the intermittency of energy production, which results in problems of stability of the electricity grid and power quality issues [1] [2] [3]. The effects of the separate installation of PV or wind power systems are well-known in literature [4] [5] [6]. In different countries, such as Denmark for wind, renewables have become the main sources of power: non-programmable RES share is currently around 50% of the national electric consumption. In Germany and Spain, this share is already higher than 20%, while in Italy this goal will be reached in few years [7]. In every case, a full transformation of the power system will be even more necessary: infrastructure, policies and markets have to be improved. To compensate for the intermittency of PV and wind generators, electrochemical storages are easy to install and manage in whatever site with respect to hydroelectric pumping systems which require large reservoirs. The widespread utilization could address the power balance of local loads and distributed generators mitigating their negative effects on the grid. For example, the power surplus from PV near midday could be used later to feed local loads. Nevertheless, storage is currently expensive and cannot solve the problem of the weak seasonal correlation between low demand and high non-programmable RES generation and vice versa. Therefore, it is fundamental to know what are the acceptable amounts of grid-connected RES and storages capacities. In particular, the maximum capacities of non-programmable RES must be defined so that there is no necessity of grid upgrade. Such an upgrade of distribution transformers and lines is a consequence of high active powers from distributed generation in reverse flow on radial networks originally designed to feed purely passive loads. Taking into account the previous general remarks, in the present PhD dissertation, the optimal power sharing between PV generators, wind turbines, storage and grid to feed tertiary sector (telecommunication equipment and offices) users is determined taking into account some technical end economic constraints. Therefore, the electrical consumers in this analysis are the owners of the PV generators, wind turbines and storage systems. These three technologies are used to meet a substantial amount of the demand, while the remaining power is provided by the distribution grid. In this way, the consumers became prosumers. First, each renewable source (sun and/or wind) is investigated in terms of hours of availability to estimate the total time in which PV and/or wind power productions occur along the whole year. Then, the primary goal of the prosumers is assumed to be the achievement of the best match between power profiles of loads and power profiles of generators. Such a best match is obtained thanks to an appropriate procedure to design the sizes of generators and storages. In this procedure, power ratings of PV and wind generators and energy capacities of batteries are chosen to reach the highest levels of self-consumption and the lowest levels of power exchange with the grid according to the load profile. In every case, the selected sizing solutions are cost-effective (Net Present Value NPV>0) and cannot create problems to the grid management (overloads of distribution lines and transformers are avoided). In Figure 1 1, it is present the scheme of the simulated systems: the main components are PV and wind generators, storage and electronic converters. They supply aggregations of tertiary-sector users with a peak of consumption corresponding to tens of megawatt, composed of many offices buildings and electronic equipment's. The core of the system is the DC bus, which connects all the renewables at the voltage imposed by the batteries. On the contrary, all the loads are in AC and can be fed by the grid, when there is no production and storage is empty. PV generators are connected to the DC bus by DC/DC converters operating as Maximum Power Point Trackers (MPPTs) to extract the maximum power. An inverter provides AC power to user loads: this converter is unidirectional, because the storage recharging is performed by PV and wind generators without the grid contribution. The reason is that storage is used to support renewables to feed loads and decrease grid-exchanges. Charge-discharge cycles performed to buy and sell energy at different prices are not allowed and batteries are recharged only when there is a surplus from wind and PV (with respect to the local loads). Simulations start from hourly load profiles and environmental parameters. Solar irradiance G, air temperature Ta and wind speed data u, with 1-minute time step, are measured with high accuracy instruments of meteorological stations. These stations are installed in five sites in Apulia (Southern Italy) and have a mutual maximum distance of 150 km. The meteorological data are inputs of energy production models (Figure 1 2): the sites are characterized by a similar annual solar radiation and high deviations in wind speed profiles. The first result is that the maximum levels of self-consumption, that can be reached according to the abovementioned constraints, are in the range 50÷61% of the energy consumption. A so high autonomy from the grid is achieved by installing high storage capacities: they permit to use more PV generators and wind turbines with negligible grid injections. If the goal is the maximization of the NPV, the costs of grid exchanges become the main driver: storage is expensive and to sell energy to the grid is less profitable than self-consumption. The best choice is to design the PV and wind generators to satisfy an amount of the total consumption; in this way, most of RES production is self-consumed and injections are low. In this case, in which storage is not used, the maximum levels of self-consumption result in the range 34÷41% of the load. At the end of the simulation part of my thesis, the data related to the five case studies are compared with the results of two additional simulations, in which loads and generators of all the five analysed sites are aggregated. In the first aggregation case, distributed storage is not present and capacity of PV and wind generators corresponds to the sum of the capacities of the five sites, previously calculated in case of maximization of NPV. The aggregation of generators and loads permits to increase the self-consumption from an average value of 37% up to 40% for the whole system (this result corresponds to that one of the best case study). In future works, this improvement could reach much higher values, if other different typology of loads (e.g. dwelling houses and factories) will be added in the aggregation. In the second aggregation case, a centralized storage is present and its capacity corresponds to the sum of the capacities of distributed storage calculated in the five independent sites in case of maximization of self-consumption. The capacity of PV and wind generators corresponds to the sum of the capacities of the five sites. The aggregation does not permit to achieve better results with respect to single cases, because the high installed capacity of storage already well manages surplus and deficit of energy. In addition to the above described simulation activity, during the whole PhD course, experimental work was performed on PV systems. Part of this experimental work was published in three journal papers [8] [9] [10] (I am co-author) and they are reported in Chapter 4. This experimental work was fundamental to study in details the operation and issues of PV systems. Thus, this work was significant for the achievement of simulation results described in the previous chapters. In the first part of the experimental work, it is defined a reasonable procedure, in terms of minimum type and number of tests and thus minimum duration (a few days), in order to identify the sources of poor performance and to solve or mitigate their negative effects. Such a procedure is based on experimental tests, partly on the PV-system site and partly in laboratory, and the suitable data processing, both before the experiments and after them [8]. The second part of experimental work is related to the electric characterization of the PV generator by tracking its I-V characteristic by connecting it to a capacitor. The curve tracer based on capacitive loads is used, because it is simpler, cheaper and scalable from module level to array level with respect to the use of a variable controlled load. Nevertheless, it is required a detailed sizing of the capacitive load to optimize the duration and the accuracy of the measurements. The practical setup of I-V curve tracers at module, string and array levels is addressed in this work for the main commercial technologies. Such tracers represent a tool to easily check the performance of PV systems at the beginning and during their operation, especially when poor performance occurs [9]. In Chapter 1, it is present a description of PV and wind power generation systems and electrochemical storage technologies. In Chapter 2, it is described the architecture of the simulated systems. The management of energy flows, the models of renewable generators, simulation constraints and sizing criteria are also described in detail in Chapter 2. In Chapter 3, inputs of the simulation and the energy and economic results of the different case studies are presented. Finally, the experimental work on PV system is reported in Chapter 4
Intra-EU agricultural trade, virtual water flows and policy implications
No full textThe development of approaches to tackle the European Union (EU) water-related challenges and shift towards sustainable water management and use is one of the main objectives of Horizon 2020, the EU strategy to lead a smart, sustainable and inclusive growth. The EU is an increasinglywater challenged area and is amajor agricultural trader. As agricultural trade entails an exchange of water embodied in goods as a factor of production, this study investigates the region's water-food-trade nexus by analysing intra-regional virtual water trade (VWT) in agricultural products. The analysed period (1993-2011) comprises the enactment of theWater Framework Directive (WFD) in the year 2000. Aspects of the VWT that are relevant for the WFD are explored. The EU is a net importer of virtualwater (VW) fromthe rest of theworld, but intra-regional VWT represents 46% of total imports and 75% of total exports. Five countries account for 60% of total VWimports (Germany, France, Italy, The Netherlands, Belgium) and 65% of total VWexports (The Netherlands, France, Germany, Belgium and Spain). Intra-EU VWT more than doubled over the period considered, while trade with extra-EU countries did not show such a marked trend. In the same period, blue VWT increased significantly within the region and net import from the rest of the world slightly decreased. Water scarce countries, such as Spain and Italy, are major exporters of blue water in the region. The traded volumes of VW have been increasing almost monotonically over the years, and with a substantial increase after 2000. The overall trend in changes in VWT does not seemto be in accordance with theWFD goals. This study demonstrated that VWTanalyses can help evaluate intertwining effects of water, agriculture and trade policies which are often made separately in respective sectors
4D Trajectory Optimization Satisfying Waypoint and No-Fly Zone Constraints
No full textThis paper presents a model of an innovative Flight Management System (FMS) which is purposely developed to control a commercial airliner along an optimized 4-Dimensional Trajectory (4DT), respecting time and path constraints, while avoiding No-Fly Zones (NFZ). The optimum, expressed in terms of minimum fuel consumption, is optained by solving an Optimization Control Problem (OCP) by means of the Chebyshev Pseudospectral numerical direct collocation scheme. The OCP trajectory solution is a discrete sequence of optimal aircraft states, which guarantee the minimum-fuel trip between two waypoints. With the aim of controlling the aircraft along lateral, vertical and longitudinal axis, and in order to respect NFZ and waypoints constraints along the optimum 4DT, different guidance navigation and control techniques can be implemented. The effectiveness of the algorithms is evaluated through simulations performed in the Multipurpose Aircraft Simulation Laboratory (MASLab), on a Boeing 747-100 model, equipped with a complete Automatic Flight Control System (AFCS) suite
