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Optimizing the Execution of Biological Models
No full textModelling biological systems allows us to understand how their components interact and give rise to complex behaviour. Initially, biology relied on mathematical models based on systems of differential equations whose solution describes the concentration of the molecules in time. Recently, spurred by the metaphor of “cells as computation” by Regev and Shapiro, the scientific community adapted concurrent languages to describe biological systems. This led to the creation of computational models which are executable and not simply solvable. Executable models offer some advantages over systems of differential equations, such as allowing the modeller to capture the causality relations among the events that constitute the dynamics of the model evolution. However, these new approaches introduce new issues; for example executing a model is more computationally intensive than solving a system of differential equations, especially if the model has to be executed several times because of statistical constraints. In this thesis we focus on reducing the execution time of biological models by applying static analysis techniques
like control flow analysis and abstract interpretation
Production of Micro-Tubular Solid Oxide Fuel Cells
No full textAn innovative current collection architecture for micro-tubular solid oxide fuel cells (SOFC) has been developed. A nickel wire is coiled around a thin carbon composite rod in order to fabricate cell supports. Different carbon composites such as pencil leads and carbon fibres were investigated. The cell support was then coated with ceramic slurries based NiO/YSZ and YSZ for anode and electrolyte, respectively, by successive dip coatings. Effect of thermal behaviour, porosity, amount of binder and dip coating parameters were conjunctly analysed to produce anode and electrolyte crack-free layers with the thickness desired. Pyrolisable materials were then eliminated under air atmosphere at 800ºC followed by co-sintering of half-cells at 1380ºC for 2 h in argon to avoid the oxidation of the nickel wire. In order to complete the cells, sintered half-cells were dipped into cathode inks consisted of LSM-YSZ composite for a functional layer and LSM pure to increase the electrical conductivity of the cathode. The cathode was also sintered at 1150ºC for 2 h under argon atmosphere.
Complete cells with an outer diameter below 1.2 mm and length of 30 mm with an effective cathode length of 20 mm and whose active cathode area is 0.75 cm2 were produced.
The efficiency of the current collector method developed is evaluated by comparison with the performance of a micro-tubular cell produced and tested under similar conditions, but with a common current collection method. The results of I-V curves shown that the innovative current collection method enhances the performance of a typical micro-tubular cell in the order of 3-4 times. The improvement in performance is attributed to the reduction of current paths of the micro-tubular cells.
Suggestions for the production and characterization of current collector-supported micro-tubular cells are also given
Novel Design Solutions for High Reliability RF MEMS Switches
No full textThis doctorate thesis focuses on the analysis, design and characterization of Radio-Frequency (RF) Micro-Electro-Mechanical System (MEMS) switches for space applications. The work was inspired and supported by the European Space Agency (ESA) Contract No. ITT AO/1-5288/06/NL/GLC ?High Reliability Redundancy Switch?. The main purpose of the project is the design and realization of high-reliability RF MEMS switches for satellite payload redundancy networks. Up to now, the common satellite architecture implements redundancy networks by means of bulky devices. RF MEMS switches allow for extremely miniaturized networks along with outstanding performances in terms of losses, power consumption and linearity, not really achievable with solid state devices. As requirements for such an application, RF MEMS switches have to survive under extremely harsh environmental and operating conditions. In particular the device should handle continuous bias voltage (at least for 10 years), 5 W of RF input power and around 1000 actuation cycles without meaningful electrical and mechanical failure. The thesis proposes novel mechanical solutions to accomplish this task, exploiting active restoring mechanisms able to restore the previous status of switch in case of reversible failure. This work also provides a deep insight on the main reliability aspects of a RF MEMS device such as dielectric charging, contact degradation and power handling
Semantic annotation of business process models
No full textIn the last decades, business process models have increasingly been used by companies with different purposes, such as documenting enacted processes or enabling and improving the communication among stakeholders (e.g., designers and implementers). Aside from the differences, all the roles played by process models involve human actors (e.g., business designers, business analysts, re-engineers) and hence demand for readability and ease of use, beyond correctness and reasonable completeness. It often happens, however, that process models are large and intricate, thus resulting potentially difficult to understand and to manage.
In this thesis we propose some techniques aimed at supporting business designers and analysts in the management of business process models. The core of the proposal is the enrichment of process models with semantic annotations from domain ontologies and the formalization of both structural and domain information in a shared knowledge base, thus opening to the possibility of exploiting reasoning for supporting business experts in their work. In detail, this thesis investigates some of the services that can be provided on top of the process semantic annotation, as for example, the automatic verification of process constraints, the automated querying of process models or the semi-automatic mining, documentation and modularization of crosscutting concerns. Moreover, special care is devoted to support designers and analysts when process models are not available or they have to be semantically annotated. Specifically, an approach for recovering process models from (Web) applications and some metrics for evaluating the understandability of the recovered models are investigated. Techniques for suggesting candidate semantic annotations are also proposed. The results obtained by applying the presented techniques have been validated by means of case studies, performance evaluations and empirical investigations
Computational inverse scattering via qualitative methods
No full textThis Ph.D. thesis presents a threefold revisitation and reformulation of the linear sampling method (LSM) for the qualitative solution of inverse scattering problems (in the resonance region and in time-harmonic regime):
1) from the viewpoint of its implementation (in a 3D setting), the LSM is recast in appropriate Hilbert spaces, whereby the set of algebraic systems arising from an angular discretization of the far-field equation (written for each sampling point of the numerical grid covering the investigation domain and for each sampling polarization) is replaced by a single functional equation. As a consequence, this 'no-sampling' LSM requires a single regularization procedure, thus resulting in an extremely fast algorithm: complex 3D objects are visualized in around one minute without loss of quality if compared to the traditional implementation;
2) from the viewpoint of its application (in a 2D setting), the LSM is coupled with the reciprocity gap functional in such a way that the influence of scatterers outside the array of receiving antennas is excluded and an inhomogeneous background inside them can be allowed for: then, the resulting 'no-sampling' algorithm proves able to detect tumoural masses inside numerical (but rather realistic) phantoms of the female breast by inverting the data of an appropriate microwave scattering experiment;
3) from the viewpoint of its theoretical foundation, the LSM is physically interpreted as a consequence of the principle of energy conservation (in a lossless background). More precisely, it is shown that the far-field equation at the basis of the LSM (which does not follow from physical laws) can be regarded as a constraint on the power flux of the scattered wave in the far-field region:
if the flow lines of the Poynting vector carrying this flux verify some regularity properties (as suggested by numerical simulations), the information contained in the far-field constraint is back-propagated to each point of the background up to the near-field region, and the (approximate) fulfilment of such constraint forces the L^2-norm of any (approximate) solution of the far-field equation to behave as a good indicator function for the unknown scatterer, i.e., to be 'small' inside the scatterer itself and 'large' outside
The Regulation of Financing and Administration of Social Security Systems in the Context of the Rights-Based Approach to Development: the Cases of Russia and Ukraine
No full textThe present work analyzes the development of the international standards in the area of financing and administration of social security and their influence on the
reforms of social security systems in transitions economies of Eastern Europe.
Particular attention is given to the concept of the rights-based approach to development as a leading principle behind the development agenda of international organizations. In particular, ILO Convention No. 102 and other international legal standards regulating the financing and administration of social security schemes are examined regarding their suitability for the ratification by transition economies. The research of possible reasons is undertaken to answer the question as to why the standards have received an unusually low level of ratifications. Examples of several
Latin American countries are provided to illustrate the lack of sustainability as a result of pension reforms which were carried out in contradiction to the basic principles of the financing and administration of social security systems as provided by ILO legal instruments. Further, the mechanisms of financing and administration of social security systems in Russia and Ukraine are analyzed in order to assess the countries’ readiness to ratify ILO instruments in these areas, as well as to assess the
suitability of the instruments for these countries. The research has showed that despite being largely outdated, ILO Convention No. 102 still has significant influence on the development of social security systems and provides for
fundamental principles in the areas of financing and administration of social security schemes. Russia and Ukraine are currently at different stages of readiness
to ratify the Convention, as they adopted contrasting strategies in the development of social security systems. In particular, due to the introduction of privately funded
social security schemes Russia is likely to be reluctant to proceed with the ratification. However, the research has revealed no legal obstacles for Ukraine to be able to ratify the Convention
AID Effectiveness in Post-Conflict Countries
No full textSince the end of the Cold War, post-conflict countries have attracted widespread economic assistance and policy advice from donor community to support their recoveries from war, to rebuild institutional capacities, and to restore their human and social capital. Yet, donor responses to post-conflict countries are uneven and some countries have received substantial amounts of assistance in the immediate aftermath of the conflict (e.g., Bosnia and Herzegovina, Kosovo, Afghanistan, and Iraq). In addition, the stark environment of the post-conflict countries poses challenges to both recipient and donor countries.
This dissertation examines the role of aid in countries recovering from conflict by investigating the determinants and the time scale of post-conflict aid and its impact on outcomes of economic recovery. In so doing, this dissertation aims to enhance understanding of the role of foreign aid in post-conflict environments. It is timely in the context of reevaluation of aid effectiveness and increasing concerns about fragile states, whereby post-conflict countries are especially significant as they are less likely to meet MDGs; and yet, post-conflict countries attract aid from the same pool of donor funding, with other non-conflict countries.
The analysis in this dissertation contributes to the ongoing debate on foreign aid effectiveness in three aspects. First, to trace temporal patterns of aid inflows and estimate their potential impact on recovery outcomes, I bring together both strands of aid literature: aid allocation and aid effectiveness. Second, under the same framework, I examine effectiveness issues through different recovery outcomes, such as economic growth, infant mortality, and good policy environment. Lastly, I combine cross-country and case study analysis.
The findings of this analysis support the view that aid offsets negative effects of conflict on recipient societies. Although the effects of post-conflict aid on growth seem more ambiguous, in post-conflict settings, aid is more effective in saving lives, reconstructing physical and institutional infrastructure, and adopting good policies. These findings unravel the heterogeneous impact of post-conflict aid on different recovery outcomes and suggest the importance of generous aid flows during the early years after the conflict; better absorptive capacities of aid in later periods may not be attained if a country fails to build its institutions and reconstruct its social capital. Consequently, the time-sequencing of aid should be governed by multiple goals, if it is to attain an immediate peace dividend
Spatiotemporal aspects in audiovisual interaction
No full textHow humans perceive everyday reality is one of the most fascinating and enduring interest of different scientific disciplines. The aim of the present dissertation is to investigate - from both a theoretical and an empirical perspective - some aspects concerning the crossmodal interactions between hearing and vision. In the first part of the introduction special attention is given to the cortical and subcortical neural substrate involved in integrating different sensory modalities, and more specifically, audiovisual stimuli. Experimental studies in the literature designed to empirically investigate different aspects of audiovisual interaction and the potential existence of a sensory dominance between hearing and vision will be presented. In the last part, the introduction will be focalized to discuss some of the principal models aimed to predict the outcome of audiovisual integration and its relation with sensory dominance.
The following chapters present the experimental studies designed to empirically investigate different aspects of audiovisual interactions and the role of eye movements in auditory cognition.
In a first study, the effects of eye movements on auditory spatial representation will be explored. The aim is to disentangle controversial results in the literature emerged in two studies that used different type of sounds (i.e., free field sounds provided through loudspeakers vs. sounds provided intracranially through headphones) and different tasks.
In a second study, the disputed relation between perception and action will be investigated in presence of a crossmodal audiovisual illusion. The aim is to verify whether participants’ visuo-motor behaviour might be biased by the visual illusion as emerged for perception, and eventually, whether perceptive and motor biases are correlated.
The last study presented in this dissertation will explore the effects of crossmodal audiovisual stimulation in low vision patients and the relation between the visual pathology. More precisely, the possible visual detection enhancement provided by a sound coupled with a visual stimulus will be investigated. To this purpose, in a first experiment, the effect of spatial disparity between audiovisual stimuli will be deepened while the last two experiments will be focalized on the effects of temporal audiovisual disparities of crossmodal stimuli.
The results of the studies described in the present dissertation provide evidence of an effect of eye movements in the auditory spatial cognition and a relation between the perceptive and visuo-motor systems in presence of an illusion induced by a sound. Moreover the presented findings report for the first time a significant crossmodal effect of audition on visual perception in low vision patients
Il caso Oriani: analisi di una appropriazione
No full textIl lavoro prende in esame la rivendicazione della continuità con la figura e l'opera di Alfredo Oriani da parte prima del movimento nazionalista, quindi del regime fascista. Tale appropriazione viene trattata alla stregua di un "caso" a sottolinearne la forzatura politico-ideologica
Multilayered Structures under large Bending: Finite Solution and Bifurcation Analysis
No full textFinite plane strain bending is solved for a multilayered elastic–incompressible thick plate. This multilayered solution, previously considered only in the case of homogeneity, is in itself interesting and reveals complex stress states such as the existence of more than one neutral axis for certain geometries. The bending solution is employed to investigate possible in-plane and out-of-plane incremental bifurcations. The analysis reveals that a multilayered structure can behave in a completely different way from the corresponding homogeneous plate. For a thick plate of neo-Hookean material for instance, the presence of a stiff coating strongly affects the bifurcation critical angle. Experiments designed and performed to substantiate our theoretical findings demonstrate that the theory can be effectively used as a design tool for predicting the capability of an elastic multilayered structure