Nuovo modello cinetostatico della caviglia umana.

The relevance of human joint models has been shown in the literature. They can help in diagnosis, in prostheses and ortheses design and in predicting the joints’ behavior. Recently a sequential approach for the modeling of the human diarthrodial joints composed of three steps has been proposed. At each step the role of some anatomical structures is considered. Starting from a limited number of structures, the model gets more and more sophisticated until all the components, both passive (articular surfaces, ligaments and tendons) and active (muscles), are incorporated in the final model. According to this procedure, the behavior of the human ankle during passive motion (no loads applied) has been previously modeled by a one degree of freedom 5-5 fully parallel mechanism. Starting from this model, the kinetostatic model of the human ankle joint that replicates its behavior when external loads are applied is developed. The anatomical and mechanical characteristics and the role of the passive structures are considered; a multifiber model is developed and an optimization criteria based on experimental data is proposed. Finally an application of the developed model to an amputated ankle is presented, together with the results obtained from the optimization of the geometrical and mechanical Parameters. Although some improvements can be achieved, the model is satisfactorily able to replicate the behavior of the human ankle subject to the anterior drawer and the inversion clinical tests applied in the neutral position.

Numerical simulation of interdigitated back contact hetero-junction solar cells

The goal of this thesis is the application of an opto-electronic numerical simulation to heterojunction silicon solar cells featuring an all back contact architecture (Interdigitated Back Contact Hetero-Junction IBC-HJ). The studied structure exhibits both metal contacts, emitter and base, at the back surface of the cell with the objective to reduce the optical losses due to the shadowing by front contact of conventional photovoltaic devices. Overall, IBC-HJ are promising low-cost alternatives to monocrystalline wafer-based solar cells featuring front and back contact schemes, in fact, for IBC-HJ the high concentration doping diffusions are replaced by low-temperature deposition processes of thin amorphous silicon layers. Furthermore, another advantage of IBC solar cells with reference to conventional architectures is the possibility to enable a low-cost assembling of photovoltaic modules, being all contacts on the same side. A preliminary extensive literature survey has been helpful to highlight the specific critical aspects of IBC-HJ solar cells as well as the state-of-the-art of their modeling, processing and performance of practical devices. In order to perform the analysis of IBC-HJ devices, a two-dimensional (2-D) numerical simulation flow has been set up. A commercial device simulator based on finite-difference method to solve numerically the whole set of equations governing the electrical transport in semiconductor materials (Sentuarus Device by Synopsys) has been adopted. The first activity carried out during this work has been the definition of a 2-D geometry corresponding to the simulation domain and the specification of the electrical and optical properties of materials. In order to calculate the main figures of merit of the investigated solar cells, the spatially resolved photon absorption rate map has been calculated by means of an optical simulator. Optical simulations have been performed by using two different methods depending upon the geometrical features of the front interface of the solar cell: the transfer matrix method (TMM) and the raytracing (RT). The first method allows to model light prop-agation by plane waves within one-dimensional spatial domains under the assumption of devices exhibiting stacks of parallel layers with planar interfaces. In addition, TMM is suitable for the simulation of thin multi-layer anti reflection coating layers for the reduction of the amount of reflected light at the front interface. Raytracing is required for three-dimensional optical simulations of upright pyramidal textured surfaces which are widely adopted to significantly reduce the reflection at the front surface. The optical generation profiles are interpolated onto the electrical grid adopted by the device simulator which solves the carriers transport equations coupled with Poisson and continuity equations in a self-consistent way. The main figures of merit are calculated by means of a postprocessing of the output data from device simulation. After the validation of the simulation methodology by means of comparison of the simulation result with literature data, the ultimate efficiency of the IBC-HJ architecture has been calculated. By accounting for all optical losses, IBC-HJ solar cells result in a theoretical maximum efficiency above 23.5% (without texturing at front interface) higher than that of both standard homojunction crystalline silicon (Homogeneous Emitter HE) and front contact heterojuction (Heterojunction with Intrinsic Thin layer HIT) solar cells. However it is clear that the criticalities of this structure are mainly due to the defects density and to the poor carriers transport mobility in the amorphous silicon layers. Lastly, the influence of the most critical geometrical and physical parameters on the main figures of merit have been investigated by applying the numerical simulation tool set-up during the first part of the present thesis. Simulations have highlighted that carrier mobility and defects level in amorphous silicon may lead to a potentially significant reduction of the conversion efficiency.

Investigation of the reactivity of metal oxide catalysts for the gas-phase phenol methylation

The gas-phase phenol methylation with methanol was investigated both from catalitic and spectroscopic point of view. In particular, the work focus on the behavior of metal oxide catalysts, like iron(III) vanadate and aluminum vanadate. Spectroscopic studies include: X-ray diffraction and Raman analysis for catalyst charactrerization; Diffuse reflectance infrared fourier transform spectroscopy and in-situ Infrared spectroscopy in vacuum for investigation of interactions between reactants and surface of catalysts.

Catalytic reduction of organic pollutants using supported metal nanoparticles

Metal nanoparticle catalysts have in the last decades been extensively researched for their enhanced performance compared to their bulk counterpart. Properties of nanoparticles can be controlled by modifying their size and shape as well as adding a support and stabilizing agent. In this study, preformed colloidal gold nanoparticles supported on activated carbon were tested on the reduction of 4-nitrophenol by NaBH4, a model reaction for evaluating catalytic activity of metal nanoparticles and one with high significance in the remediation of industrial wastewaters. Methods of wastewater remediation are reviewed, with case studies from literature on two major reactions, ozonation and reduction, displaying the synergistic effects observed with bimetallic and trimetallic catalysts, as well as the effects of differences in metal and support. Several methods of preparation of nanoparticles are discussed, in particular, the sol immobilization technique, which was used to prepare the supported nanoparticles in this study. Different characterization techniques used in this study to evaluate the materials and spectroscopic techniques to analyze catalytic activities of the catalyst are reviewed: ultraviolet-visible (UV-Vis) spectroscopy, dynamic light scattering (DLS) analysis, X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM) imaging. Optimization of catalytic parameters was carried out through modifications in the reaction setup. The effects of the molar ratio of reactants, stirring, type and amount of stabilizing agent are explored. Another important factor of an effective catalyst is its reusability and long-term stability, which was examined with suggestions for further studies. Lastly, a biochar support was newly tested for its potential as a replacement for activated carbon.

From point cloud to HBIM: an integrated workflow for 3D reconstruction of heritage building with model accuracy evaluation

Modern society is now facing significant difficulties in attempting to preserve its architectural heritage. Numerous challenges arise consequently when it comes to documentation, preservation and restoration. Fortunately, new perspectives on architectural heritage are emerging owing to the rapid development of digitalization. Therefore, this presents new challenges for architects, restorers and specialists. Additionally, this has changed the way they approach the study of existing heritage, changing from conventional 2D drawings in response to the increasing requirement for 3D representations. Recently, Building Information Modelling for historic buildings (HBIM) has escalated as an emerging trend to interconnect geometrical and informational data. Currently, the latest 3D geomatics techniques based on 3D laser scanners with enhanced photogrammetry along with the continuous improvement in the BIM industry allow for an enhanced 3D digital reconstruction of historical and existing buildings. This research study aimed to develop an integrated workflow for the 3D digital reconstruction of heritage buildings starting from a point cloud. The Pieve of San Michele in Acerboli’s Church in Santarcangelo Di Romagna (6th century) served as the test bed. The point cloud was utilized as an essential referential to model the BIM geometry using Autodesk Revit® 2022. To validate the accuracy of the model, Deviation Analysis Method was employed using CloudCompare software to determine the degree of deviation between the HBIM model and the point cloud. The acquired findings showed a very promising outcome in the average distance between the HBIM model and the point cloud. The conducted approach in this study demonstrated the viability of producing a precise BIM geometry from point clouds.