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Hydrothermal carbonization of waste biomass
No full textHydrothermal carbonization (in acronym, HTC) is a thermochemical conversion process through which it is possible to directly transform wet organic substrates into a carbonaceous material, referred as hydrochar. Hydrochar has chemical and physical characteristics that make it similar to fossil peats and lignite. Depending on the process conditions, mostly temperature and residence time, this material can be enriched in its carbon content, modifying its structure and providing it interesting characteristics that make it possible to be used for several applications, such as for energy production, as a soil conditioner and improver, for carbon dioxide sorption and sequestration, and some others reported in literature. HTC is a different process, if compared to other common thermochemical processes, such as pyrolysis, torrefaction, gasification, etc., because it works in wet conditions (humidity content higher than 60%). As a matter of fact, biomass is transformed into hydrochar because of the properties of hot pressurized water, that acts both as a reactant and as a catalyst. The HTC process has been studied from many years, although at present not all the chemical reactions that occur during the process are completely known. Moreover, the application of this quite new process to different substrates can bring to different results. Even though HTC can be applied to any kind of organic material (of both animal and vegetable derivation), the possible uses of hydrochar can strongly be influenced by the characteristics of the feedstock. This, for example, can be due to legislative constraints. In Chapter 1, an overview of the existing literature is presented. To get insights on this process, a small bench scale batch reactor has been designed and built at the Department of Civil, Environmental and Mechanical engineering of the University of Trento, Italy. This reactor has been tested, prior to be used with real substrates. In Chapter 2 the reactor and the preliminary tests done are described. In this work, the HTC process applied to three different substrates have been studied: grape marc, the EWC 19.05.03 residue and the EWC 19.12.12 residue. In Chapter 3 the three raw substrates are described. Grape marc is produced by the winery industries or by distilleries. This feedstock is composed by woody seeds and holocellulosic skins and it presents an average humidity content of about 60%. At present, it is used for the production of animal food or it is landfilled. In this case, the application of HTC can be an interesting alternative to these end uses because, through this process, grape marc can be recovered, for example, for energy production. The hydrochar produced from this feedstock could be even used as a soil conditioner. In Chapter 4 several analyses on the hydrochar, on the process water and on the gaseous phase obtained during the carbonization tests are presented. The EWC 19.05.03 residue is a by-product of the composting treatment applied to the organic fraction of municipal solid waste (MSW). In collaboration with Contarina S.p.A., a company that collects and treats MSW in the province of Treviso, in the North-East of Italy, this by-product was carbonized and tested both as a soil conditioner and for energy production. Results of the analyses on the solid, liquid and gaseous phases produced by the HTC process are reported in Chapter 5. The EWC 19.12.12 residue is a by-product of the refuse derived fuel (RDF) production, from the residual fraction of the MSW. This substrate was provided by Contarina S.p.A. and preliminary tests on the exploitability of the hydrochar for energy production are reported in Chapter 6, together with analyses on both the liquid and gaseous phases. A rigorous energy balance has been proposed in Chapter 8, based on the experimental data obtained for grape seeds. In this chapter, all the hypotheses and the assumptions taken to evaluate the enthalpy of the HTC reaction at different process conditions (namely, three different temperatures and three residence times) are described. In Chapter 8 a kinetic model is proposed, based on a two-step reaction mechanism. The activation energy and pre-exponential factor of the various degradation reactions were determined by means of least square optimization versus the experimental data of grape marc. A thermo fluid model is even proposed in this chapter. The model integrates mass, momentum and heat equations within the reactor domain by means of the finite volumes method (f.v.m.) approach. Convective and radiative exchange between the reactor and the fluid within the reactor have been implemented in the f.v.m. model. Under two strong assumptions (mono-component and mono-phase fluid, which fulfils the reactor), it was possible to estimate the behaviour of an equivalent fluid (eq_fluid), in terms of thermal properties of the fluid (thermal capacity, thermal conductivity and thermal diffusivity). Moreover, a simplified dynamic analytic model is also presented – based on lumped capacitance method – in order to simulate the thermal behaviour of the system, using the actual temperature profile imposed by the reactor external heater. A resistance-capacitance network was used to describe the system. Finally, the Henry’s law has been applied to assess the amount of gas really produced during the HTC process.
In Chapter 9, the main conclusions of this work are reported
Stress singularities, annihilations and invisibilities induced by polygonal inclusions in linear elasticity
No full textNotches, wedges, cracks, stiffeners, inclusions and defects in plane elastostatics are known to generate singular stresses and limit the overall strength of a composite material. In the present thesis, after showing experimentally that the singular stress field predicted by the linear elastic solution for the rigid inclusion
model can be generated in reality and with great accuracy within a material, attention is devoted then in achieving the out-of-plane response of an infinite plane containing polygonal and hypocycloidal-shaped voids and rigid inclusions subject to generalized remote loading conditions.
The analytical solution obtained for the case of polygonal inclusions shows some unexpected and interesting features such as an infinite set of geometries and loading conditions exist for which not only the singularity is absent, but the stress vanishes (annihilates) at the corners. Thus
the material, which even without the inclusion corners would have a finite stress, remains unstressed at these points in spite of the applied remote load. Moreover, similar conditions are determined in which a star-shaped
crack or stiffener leaves the ambient stress completely unperturbed, thus reaching a condition of ‘quasi-static invisibility’. The solution in closed-form is also obtained for the case of hypocycloidalshaped voids and rigid inclusions, showing that cusps may in certain conditions act as stress reducers, situations for which the stress at the cusp tip in the presence of the inclusion is smaller than in the case when the inclusion is absent.
Ph.D. Thesis – Summer Shahzad vThe obtained solutions provide closed-form expressions for Stress Intensity Factors and Notch Stress Intensity Factors at varying the inclusion
geometry and of loading conditions, fundamental quantities in defining criteria of fracture initiation/propagation or inclusion detachment. The findings of stress annihilation, stress reduction and inclusion invisibility define optimal loading modes for the overall strength of a composite
and are useful in the design of ultra-resistant materials
There and Back Again: Post-return experiences of Highly-skilled Belarusian professionals
No full textThe research lies at the intersection of two large social research areas—highly skilled migration and return migration—and aims to provide a contribution to the studies of sending countries by focusing on post-return experiences of highly skilled professionals in the Belarusian context. Thus, I explore public attitudes toward migration issues in Belarus; investigate the dynamics of return migration among highly skilled migrants; analyse the complexities of highly skilled people’s lifestyles; and study in which ways they apply socio-cultural remittances to different spheres of their lives. Among the main results of this research are the following. This study has conceptualised return in relation to the transnational involvement of returnees, by introducing the concepts of ‘locally oriented’- and ‘transnationally oriented style of life’. These ideal types of post-return lifestyle differ in degree of mobility, attitudes toward home, consumption practices, and type of employment. International experience of living abroad seems to have had a substantial effect on individual styles of life in terms of transnational orientation. However, it appears to be quite heterogeneous and has evident gender differences in its manifestations. Moreover, I argue that formation and transmission of socio-cultural remittances are strongly heterogeneous and selective processes, which manifest themselves to varying degrees not only in different people, but also in different aspects of people’s lives. The analysis of several socio-cultural remittances in private and public spheres showed that under certain conditions, the formation of ‘reactive’ socio-cultural remittances occurred. What is more, in some cases the socio-cultural remittances appeared to have strong gender differences. The results draw on qualitative content analysis of three online discussions (almost 19 thousand posts) and 43 in-depth interviews with highly skilled Belarusian returnees
Auto da fé. Rileggere Giorgio Manganelli
Get PDFQuesta tesi rilegge l'opera di Manganelli, cercando di sfrondare l'aneddotica fiorita attorno alla sua figura e di motivare i giudizi critici spesso limitativi del suo lavoro. La tesi è suddivisa in tre parti: una prima dedicata agli scritti giovanili di Manganelli, visti in parallelo con opere più mature (Centuria, Encomio del tiranno) e il rapporto con Leopardi, Pavese, Edmund Wilson, facendo ricorso anche a materiale inedito; nella seconda parte viene tentata una lettura (volutamente forzata) di Hilarotragoedia come un effettivo 'trattatello' retorico, da sviscerare Lausberg alla mano; infine, una terza parte indaga il rapporto di Manganelli con la letteratura inglese e la sua attività di traduttore
Labour, Environment and Empire in the South Atlantic (1780-1860)
No full textThe South Atlantic Ocean and its islands (Saint Helena, Tristan da Cunha, Ascension) were a periphery of the British Empire. Nevertheless this region faced a dramatic transformation during the Global Age of Revolutions (1780-1830) and moved from being a transition zone between Europe and Asia into a proper maritime system. The great global issues of labour (slavery, indentured labour, white emigration), environment (environmental imperialism and imperial environmentalism) and Empire (colonial government, authority and freedom) evolved in the micro-histories of the South Atlantic islands in a very peculiar way, making them precious case-studies to assess wider themes in a new perspective
Multi-decadal morphodynamics of alternate bars in channelized rivers: a multiple perspective
No full textAlpine rivers have been regulated to claim productive land in valley bottoms since the last two centuries. Width reduction and rectification often induced the development of regular scour-deposition sequences, called alternate bars, with implications for flood protection, river navigation, environmental integrity. Understanding how alternate bars evolve in rivers and defining the key aspects that influence the development of these regular deposits of sediments represents a challenge that is not fully described. Most studies on alternate bars are in fact based on mathematical theories, laboratory experiments and since 1990s numerical simulations, but only few studies on field cases have been performed so far. The goals of this work are: i) to quantify the morphodynamics of alternate bars in the Alpine Rhine River, with a particular emphasis on bar migration; ii) to assess to what extent the predictions of analytical bar theories are consistent with field observations and to explore how theories may help interpret observed alternate bars dynamics; iii) to determine the ability of a numerical model to simulate correctly the formation and the length scale of alternate bars and the influence of different multi-decadal inflow conditions. The 42 km chosen reach is located along the border between Austria and Switzerland, between the confluences of Landquart and Ill rivers. The whole reach has been completely embanked starting from the 19th century, so alternate bars have been present for more than a century. Moreover the simplification of the cross section, together with the presence of only few bends, puts the Alpine Rhine in the ideal position to be compared with analytical theories of alternate bars in straight channels.
The goals are achieved by analyzing a dataset of freely available Landsat imagery, which combine unprecedented temporal length (3 decades), spatial length (more than 400 channel widths) and temporal resolution (around 3 images per year). Bars show a spatially selective behavior, with short bars occurring in distinct straight reaches with respect to longer bars. The same evidence is found in terms of bar migration, so that short bars are shown to migrate more than longer bars, in agreement with theoretical predictions. A full range of bar wavelengths and more complex patterns occur in reaches with bends and ramps. Bar height, obtained from cross section monitoring, was found to be much more uniform. The temporally long dataset, including approximately 30 floods with different magnitude and duration, allowed the investigation of bar migration as a function of discharge, showing that bars migrate faster for intermediate floods. Predicted values of linear theories for free and forced bars in straight channels are in good general agreement with field observations, when considering conditions of bar formation and bar wavelength. Comparing theories and observations suggests that theoretical outcomes may represent the boundaries of the actual, wide range of bar behavior, which likely reflects non-linear interactions, flow unsteadiness, sediment size heterogeneity and finite length of straight reaches, which are not retained in
linear theories. Non-linear interactions are investigated through the 2D numerical morphodynamic model Basement, developed at the Swiss Federal Institute of Technology of Zurich. Preliminary investigations focus on the role of the transverse sediment transport, that behaves as a diffusive term. The numerical diffusion can be indirectly evaluated starting from the calibration of the coefficient of the diffusive term. A benchmark methodology to evaluate the lateral and numerical diffusion is defined. The results are
used in the morphological calibration of the model. The spatial trend of wavelengths is in general agreement with the field data, and the migration takes place mainly in correspondence to short bars, whereas long bars tend to elongate with time. The choice of a constant discharge or a real hydrograph influences the time scale of bar evolution.
The present analysis results in the longest spatial and temporal field case study of river bars in channelized rivers with a temporal survey resolution that allows the investigation of the effect of individual flood events, and provides new quantitative data on bar wavelength and migration. The dataset provides useful information to assess the applicability of analytical bar theories, so far mainly tested against flume experiments, and following recent attempts in French and Dutch streams. Moreover, a novel
two-dimensional morphological benchmark to access the role of numerical diffusion is proposed
Information Fusion Approaches for Distant Speech Recognition in a Multi-microphone Setting
No full textIt is a well known fact that high quality Automatic Speech Recognition is still difficult to guarantee under conditions in which the speaker is distant from the microphone due to the distortions caused by acoustic phenomena, such as noise and reverberation. Among the different research directions pursued around this problem, the adoption of multi-channel approaches is of great interest to the community given the potential of taking advantage of information diversity.
In this thesis we elaborate on approaches that exploit different instances of a sound source, captured by various largely spaced microphones, in order to extract a Distant Speech Recognition hypothesis. Two original solutions are presented, based on information fusion approaches at different levels of the recognition system, one at front-end stage and one at post-decoding stage, namely for the problems of channel selection (CS) and hypothesis combination. First, a new CS framework is proposed. Cepstral distance (CD), which is effectively applied in other acoustic processing fields, is the basis of the CS method developed. Experimental results confirmed the advantages of a CD-based selection schema under different scenarios. The second contribution concerns the combination of information extracted from the individual decoding processes performed over the multiple captured signals. It is shown how temporal cues can be identified in the hypothesis space, and be beneficial for the elaboration of a multi-microphone confusion network, from which the final speech transcription is derived. The proposed methods are applicable in a setting equipped with synchronized distributed microphones, independently of the proximity between the sensors. Analysis of the novel concepts were performed over synthetic and real-captured data. Both approaches achieved positive results at the different assessment tasks they were exposed to
Micro fabrication technologies for tear fluid sensors for functional contact lens applications
No full textFunctional multi-purpose contact lenses have recently attracted attention as suitable means to exploit the characteristics of the eye to diagnose diseases and for drug delivery. Such enrichment of the normal contact lenses are mainly achieved by the integration of different components like micro sensors and microelectronics onto the contact lens substrate. The surface of our eye is an interesting chemical interface, which acts like a window into the human body. For example, intraocular pressure is a surrogate marker of cardiovascular health. Just like the blood, the eye tear contains many health parameters which could be used to diagnose various illness. Therefore, a contact lens with integrated biosensors shall provide health professionals with a new tool for research studies and for diagnosing diseases in a novel way without traditional lab works. Motivated by this fact, this thesis deals with the integration of biosensors on contact lens to sense the eye tear film solution. The contact lens is made of polydimethylsiloxane (PDMS) and the sensor is bare gold electrodes patterned using micro fabrication technology. However there are several challenges that need to be addressed before reaching the final functional contact lens with incorporated micro devices and micro sensors for biomedical applications. One such challenge is related to the metallization on polymer substrates. The results are presented in the direction of realizing robust metal patterns on polymer substrates. Comparison study of various metallization techniques on different polymer substrates like PDMS, PET(Polyethylene terephthalate) to name a few and different metals patterned like Ag, Au to name a few are presented and thus emphasizing the reasons for the selection of polymer and micro fabrication technique used for the final device. Surface characterization of the patterned metal is performed using various techniques and the analyzed data are presented. Specific steps and solutions to issues like crack formation and adhesion of the metal on the polymer substrates are also discussed.
An electrochemical sensor for the diagnosis of Keratoconjuctivitis sicca or dry eye syndrome (DES) is presented. Aqueous layer in the tear film plays an important role in maintaining the moisture inside the eye. This layer consists of proteins, carbohydrates, oxygen and some inorganic salts. It has been shown that in dry eye patients, the salt content in the tear film is higher compared to that of a healthy person. So to diagnose dry eye syndrome, we developed an impedimetric sensor to measure the resistance of the eye tear solution and we conduct associated experiments to analyze the performance. An inverse relationship between solution resistance and saline concentration in a log10vslog10 plot was confirmed. The fabricated sensors were tested for reproducibility of the results and the DES severity scale falls well inside the detection limit of the sensor. The work is wrapped up by the proof of concept experiments performed for the wireless transmission of the data from the sensor using resonance RLC circuit
La diàtriba cinico-stoica: uno strumento concettuale o un mito filologico? Analisi del dialogismo diatribico e del ruolo dell'interlocutore fittizio nella filosofia romana
Get PDFThe starting point of our thesis is the critical discussion of a concept taken for granted by literary and ancient philosophy scholars. This is the cynic-stoic diatribe, so named because cynical themes would coexist with Stoic ones.
Our first step is assessing the accuracy of the widely accepted definition, which makes the connection between the diatribe and a tradition of topics relating to moral popular philosophy. Then we explain our choice to accept and to try to integrate recent scientific acknowledgments which accept the diatribe as a literary genre relating to the spiritual guidance method of the Socratic philosophical schools, with a particularly attentive focus on the relationship between master and disciple. Starting from this controversial genre of Greek origin, we analyze the transition to the Roman period, by first examining the terminological aspect and then the philosophical framing. Among the methods, defined as diatribic, we focus on the only feature which does not appear to be challenged and that for this exact reason could be the basis of the existence of the genre itself: dialogism and the presence of a fictitious interlocutor.
We then focus our attention on Seneca's work, and particularly on Letters to Lucilius, where the attempt to create a master-disciple relationship is intensely visible, and in which the presence of a fictitious interlocutor is structurally related to the development of this relationship. Then we discuss the diatribic forms of Roman satire, to reach Lucilius', Horace's and Persius' cases.
A brief presentation is finally devoted to the analysis of relations between the diatribe, the Second Sophistic and the religious preaching
Interaction among vegetation and morphology in channelized rivers
Get PDFThe presence of aquatic vegetation on riverbed and embankments influences flow structure and consequently flow resistance, sediment transport, morphology, and ecology. These influences would lead to a hydraulic diversity, which is a key ingredient of physical habitat in streams. According to this fact, vegetation is commonly incorporated within stream restoration. Although significance of vegetation as an inseparable part of riverine systems is recognized, but yet it is still difficult to predict how the associated influences will respond to the introduction of vegetation and how advantages of vegetation can be optimized to a multitude of different processes.
The primary impact of vegetation is slower flow velocity and thus, reduction in conveyance capacity. In addition to affecting the velocity profile over the full depth, vegetation affects turbulence intensity and diffusion. When mean kinetic energy converts to turbulent kinetic energy within the area planted with stems, turbulence intensity will begin to intensify. As a result of velocity and turbulence changes, aquatic vegetation can affect sediment movement and consequently bed form shapes could be stabilized with new patterns. Bed form characteristics (length, shape, structure, dimensions, stability, etc.) also depend on flow structure and can be divided into different categories according to the bed load materials.
Locations and extension of vegetation in river channels is a fundamental factor should be considered besides the general impacts of vegetation in rivers. Isolated patches of vegetation are more common in practical applications rather than uniform vegetated channels in which the mean properties of the vegetation canopy are independent of the location.
The present study considered the changes in bed forms through semi-circular patches of emergent vegetation, which are located at the banks of the channel. One of the goals is to find out how an island of vegetation modifies the morphology of rivers and mass transport. In particular, this research focuses on the physics of sediment transport and its effect on bed forms, and flow resistance in the presence of a patch of vegetation, by using experimental data and numerical modeling. Providing a physically based model for estimating the effects of vegetation on flow parameters, turbulence dispersion, and sediment transportation, the results of the present study contribute to extending the knowledge of morphology and mass transport in vegetated streams