The purpose of this study is to compare the shear bond strength of different resin bases and artificial teeth made of ceramic or acrylic resin materials and whether tooth-base interface may be treated with aluminium oxide sandblasting. Experimental measurements were carried on 80 specimens consisting of a cylinder of acrylic resin into which a single tooth is inserted. An ad hoc metallic frame was realized to measure the shear bond strength at the tooth-base interface. A complete factorial plan was designed and a three-way ANalysis Of VAriance (ANOVA) was carried out to investigate if shear bond strength is affected by the following factors: (i) tooth material (ceramic or resin); (ii) base material (self-curing or thermal-curing resin); (iii) presence or absence of aluminium oxide sandblasting treatment at the tooth-base interface. Tukey post hoc test was also conducted to evaluate any statistically significant difference between shear strength values measured for the differently prepared samples. It was found from ANOVA that the above mentioned factors all affect shear strength. Furthermore, post hoc analysis indicated that there are statistically significant differences (p-value=0.000) between measured shear strength values for: (i) teeth made of ceramic material vs. teeth made of acrylic resin material; (ii) bases made of self-curing resin vs. thermalcuring resin; (iii) specimens treated with aluminium oxide sandblasting vs. untreated specimens. Shear strength values measured for acrylic resin teeth were on average 70% higher than those measured for ceramic teeth. The shear bond strength was maximized by preparing samples with thermal-curing resin bases and resin teeth submitted to aluminium oxide sandblasting.

The zona pellucida (ZP) is a specialized extracellular matrix surrounding the developing oocyte. This thick matrix consists of various types of glycoprotein that play different roles in the fertilization process. Nowadays, several techniques are available for assessing ZP’s mechanical response. The basic assumption behind these methods is that the ZP behaves like an elastic body: hence, dissipative forces are neglected and Young’s modulus remains unaffected by probe dynamics. However, dissipative forces are strongly regulated by the slippage of ZP chains past one another while reaction forces related to elastic deformations (driven by the ability of each chain to stretch) depend on the ZP structure (i.e. number of cross-links and distances between knots). Although viscous reaction forces generated by the ZP are one of the main factors regulating sperm transit, their peculiar behaviour along the ZP structure remains poorly understood and rarely investigated. In order to overcome this limitation, a novel visco-hyperelastic model describing the porcine ZP reaction forces generated by nanoindentations at different probe rates is developed and verified in this study. Visco-hyperelastic parameters of porcine ZP membranes are determined by means of a hybrid characterization framework combining atomic force microscopy nanoindentation measurements, nonlinear finite-element analysis and nonlinear optimization. Remarkably, it is possible to separate the contributions of hyperelastic and viscous terms to ZP mechanical response and evaluate the error made in the determination of ZP mechanical properties if viscous effects were not considered.

In this study a multi-scale mechano-regulation model was developed in order to investigate the mechanobiology of trabecular fracture healing in vertebral bodies. Amacro-scale finite element model of the spinal segment L3–L4–L5, including a mild wedge fracture in the body of the L4 vertebra, was used to determine the boundary conditions acting on a micro-scale finite element model simulating a portion of fractured trabecular bone. The micro-scale model, in turn, was utilized to predict the local patterns of tissue differentiation within the fracture gap and then how the equivalent mechanical properties of the macro-scale model change with time. The patterns of tissue differentiation predicted by the model appeared consistent with those observed in vivo. Bone formation occurred primarily through endochondral ossification.New woven bone was predicted to occupy the majority of the space within the fracture site approximately 7–8 weeks after the fracture event. Remodeling of cancellous bone architecture was then predicted, with complete new trabeculae forming due to bridging of the microcallus between the remnant trabeculae.

Contouring of surfaces covers both metrology measurements and determination of displacements. There are a variety of scientific methods and corresponding devices used in contouring problems. Optical methods of contouring (OMC) have been proven to compete with the high precision and accuracy of Coordinate Measurement Machines (CMM). A general model of moiré contouring was recently developed by C.A. Sciammarella and his collaborators. The model integrates concepts of projective geometry and differential geometry of surfaces and utilizes symmetric projectors to reproduce the condition of projection from infinity. For specimens with dimensions ranging from few mm to more than 1 m, the measuring system and software provided standard deviations of the measured values that can reach 1/500 of the theoretical sensitivity defined by the pitch of the utilized grating. This paper will discuss the most recent trends in the optical contouring of surfaces focusing in particular on how to extend the general model of moiré contouring to the measurement of the three-dimensional displacement field of objects of arbitrary shape.

Nanoindentation has recently emerged as a powerful tool for measuring nano- and microscale mechanical properties in tissues and other biomaterials. This technique has been used to measure the mechanical properties of microstructural features in cells, biopolymer networks, and complex biomaterials. Despite the wide use of the nanoindentation, the residual stress effect in the determination of soft samples elastic properties is still poorly explored. By using parametric finite element analysis and atomic force spectroscopy, we determined the relationships between residual stress and indenter geometry and how it can affect the structural response of polymeric spherical shells flattened on a hard surface.

Thin-walled elements are widely utilized in the design of aerospace structures as they allow to obtain lightweight structures. However, while the structures so designed may be sufficient to carry the in-plane tensile loads and satisfy strength requirements, they are often prone to fail under buckling induced by compressive or shear loads. Buckling is a highly non-linear phenomenon caused by the sudden conversion of a large amount of in-plane strain energy into bending strain energy [1]. This process may be expressed in different modes. For example, global buckling is said the catastrophic collapse of the entire structure; local buckling affects a portion of the skin; stiffener buckling occurs in correspondence of stiffener segments. Other “special” buckling modes are typical of sandwich structures (wrinkling, dimpling, etc.). In order to guarantee structural safety against buckling, reinforcing elements (stiffeners) running in the longitudinal and transverse directions are added to the panel skin to increase the stiffness of the structure. The proper selection of the stiffening configuration and materials leads to minimize structural weight thus maximizing payload. A number of trade studies on the sensitivity of structural weight of stiffened panels to parameters such as stiffener geometry, materials, and type of construction and manufacturing methods were presented in literature (see for example, [2,3]). Design concepts are usually compared and preliminarily selected to be further developed later on the basis of their structural weight (typically, the weight per unit area) which is minimized by means of optimization methods. Structural optimization is mandatory in the design of aerospace structures. Design variables are repeatedly perturbed to satisfy non-linear constraints on displacements, stresses and critical buckling loads. Optimization methods can be divided in two main groups: Approximate Optimization Methods (AOM) and Global Optimization Methods (GOM). AOM formulate and solve a set of sub-problems where the original non-linear functions of the optimization problem are replaced by linear, quadratic or higher order approximations built including gradient information. Larger fractions of design space can be explored using multi-start approximate optimization (MSAO) where different optimization runs are performed starting from points generated randomly. The main difficulty of approximate optimization is to keep the quality of the approximation as highest as possible and always reliable in the region of design space currently being searched. Furthermore, approximate models should change during the optimization process based on the sequence in which design constraints become active. Global optimization methods search the optimum design by generating randomly a certain number of trial designs. This is done in purpose to expand the portion of design space explored by the optimizer thus increasing the probability of finding the global optimum

Abstract. Il presente progetto di ricerca ha come obiettivo la messa a punto (e la realizzazione di un prototipo) di un impianto per il trattamento di rifiuti speciali pericolosi e non. Tale impianto deve essere in grado di incenerire i rifiuti e rendere gli scarti compatibili con le specifiche indicate nella normativa di settore in materia di discariche (DM 03/08/05). Tale esigenza nasce dall’evidenza che il peso dei rifiuti speciali, derivanti dalle attività economiche e industriali, rispetto alla produzione totale di rifiuti è elevato, sia in Italia che nel resto d’Europa e del mondo. L’impianto di incenerimento sarà a bassa temperatura (pirolisi) e con possibilità di recupero di energia termica. L’impianto consentirà agli utilizzatori: - di trattare qualsiasi tipologia di rifiuto eterogeneo organico e non; - di ridurre drasticamente i costi per l’energia necessaria per il trattamento e l’incenerimento di rifiuti; - di ridurre significativamente il tasso di inquinamento, rispetto ad impianti di incenerimento tradizionali essendo quello in oggetto ad emissioni quasi nulle.

The Big Bang-Big Crunch (BB−BC) algorithm is a recently developed metaheuristic optimization method that mimics the process of evolution of the universe. The inherent simplicity of BB−BC is very attractive for structural optimization experts but the huge computational cost entailed by the optimization process is a serious obstacle to the large-scale diffusion of BB−BC. To overcome this problem, at least in the case of sizing optimization problems of truss structures, the paper presents an improved BB−BC formulation where each new trial design is always forced to lie on a descent direction. The efficiency of the new BB−BC algorithm is demonstrated by a trade study carried out on four classical weight minimization problems of truss structures that include various amounts of non-convexity in the design space

Il Big Bang–Big Crunch (BBBC) riproduce l'evoluzione dell'universo generando in maniera casuale una popolazione di design (fase di esplosione) e determinandone poi il centro di massa (fase di contrazione). Se il centro di massa migliore l’ottimo corrente si effettua nuova esplosione generando così una nuova popolazione per cui si valuta nuovamente il centro di massa. Tale processo si reitera fino a che non si arriva al design ottimo. Benché il BBBC sia uno degli algoritmi meta-euristici meglio formulati in assoluto, richiede un notevole sforzo computazionale. Per ovviare a tale limitazione, il presente lavoro propone una formulazione avanzata dell’algoritmo BBBC incorporando nel processo di generazione dei design candidati informazioni sui gradienti della funzione obiettivo. Il nuovo algoritmo è quindi un BBBC con esplosioni infrequenti. I risultati ottenuti in problemi di ottimizzazione di travature reticolari comprendenti sino a 3586 elementi e 280 variabili di sizing dimostrano la bontà dell'approccio proposto