1,720,993 research outputs found
Crystals and phase transitions in protohistoric glass materials
No full textThis article reviews the crystalline material present in representative Bronze Age glasses and glassy materials from Northern and Central Italy. Their nature and formation processes are discussed based on textural, crystallographic, and chemical data. Distinction is made between crystals present in the starting raw materials and left unreacted during the glass production process, crystalline phases deliberately or accidentally formed during manufacturing, and crystalline phases added in the last stages of glass working to change the macroscopic properties of the final material. It is argued that in Bronze Age Italy glass production technology was advanced and well mastered so to produce materials having unique characters of colour and workability
Padri e madri alla prima esperienza genitoriale: comportamenti, sentimenti, atteggiamenti e desideri prima e dopo la nascita del bambino
No full textNegli ultimi anni l’interesse dei ricercatori, sia in ambito psicanalitico che in psicologia dello sviluppo, si è rivolto con crescente attenzione allo studio e alla comprensione della paternità, in particolare alle caratteristiche della funzione paterna e all’influenza che esse hanno sullo sviluppo e la crescita dei figli.
La maggior parte delle ricerche utilizza un approccio comparativo che, nel mettere a confronto le caratteristiche materne con quelle paterne, ha consentito di individuare somiglianze e differenze tra madri e padri rispetto a ruoli, compiti, atteggiamenti e credenze (Dubeau & Moss, 1998).
La funzione paterna è stata indagata considerando i fattori intrafamiliari ed extrafamiliari che influiscono nella cura e nella crescita dei figli e influenzano le modalità di interazione padre-figlio. Tra i fattori intrafamiliari, alcuni autori mettono in primo piano la qualità della relazione di coppia, il grado di soddisfazione che ne deriva per ogni coniuge (Belsky, 1984). Tra i fattori extrafamiliari che possono condizionare i padri nell’adempimento della funzione parentale, sono stati considerati di primaria importanza il grado di soddisfazione lavorativa di entrambi i coniugi (Grich & Clark, 1999) e il contesto socioculturale di appartenenza di madri e padri.
L’obiettivo della ricerca è studiare, attraverso colloqui di ricerca, la funzione paterna e materna rispetto a dimensioni quali: la sfera comportamentale, la sfera affettiva ed emozionale e la sfera attitudinale. Dal confronto dei contenuti di risposta dei coniugi è possibile verificare se esistono rilevanti differenze tra madri e padri e valutare in una prospettiva evolutiva eventuali variazioni nella funzione genitoriale.
Partecipanti
Il campione è costituito da venti coppie di coniugi alla prima esperienza genitoriale che hanno liberamente scelto di partecipare alla ricerca. L’età media dei padri è di 31 anni, quella delle madri di 27. Per entrambi i partner il livello culturale va dalla licenza media al completamento degli studi universitari, mentre il livello socioeconomico è eterogeneo.
Strumenti
La ricerca si estende dal settimo mese di gravidanza fino al tredicesimo mese di vita del bambino. Come strumento della ricerca è stato scelto un colloquio semistrutturato per aree: l’utilizzo del racconto dei genitori costituisce l’elemento distintivo del nostro lavoro. Il colloquio semistrutturato consente l’approfondimento di tematiche di natura emotiva, garantisce un’elevata libertà e flessibilità di esposizione da parte del soggetto e risponde alle esigenze di omogeneità nella raccolta dei dati. Le aree di indagine in cui si articolano i colloqui consentono un approfondimento delle dinamiche psicologiche e dei vissuti dei genitori e delle esperienze legate alle attività di cura del bambino nel corso del tempo.
Sul materiale audioregistrato dei colloqui è stata effettuata un'analisi del contenuto (Krippendorff, 1980) attraverso le seguenti categorie descrittive: comportamenti, comportamenti riferiti, atteggiamenti, desideri e sentimenti.
Risultati
L’analisi statistica ANOVA effettuata ha evidenziato sia differenze significative tra madri e padri rispetto alle unità di contenuto da considerate, sia variazioni significative della esperienza materna e paterna in funzione della variabile tempo e dello sviluppo del bambino.
Investigare i fattori che possono influenzare la transizione alla paternità e maternità è importante non soltanto nell’ambito di ricerca, ma anche e soprattutto all’interno di una prospettiva clinica
Protohistoric Vitreous Materials and Synthetic Analogues: Study of Chemico-Physical and Rheological Properties.
No full textThe experimental measurements of the rheological properties of selected archaeological glasses are presented, and compared to the experimental values obtained on synthetic analogues. The data, measured both by monitored hot stage and high-temperature rheometer, allow for the first time to asses the physical and working properties of protohistoric glasses. A preliminary interpretation of the compositional evolution of Bronze Age glasses is proposed, based on their rheological properties. The data indicate that the mean compositions of most common ancient glasses are close to the compositions having the best working properties
EQUIVALENT MATERIAL IDENTIFICATION IN COMPOSITE SCALED HULLS VERTICAL IMPACT TESTS
No full textAirworthiness regulations require that aircraft should be proved to ensure the survivability of the ditching for the passengers. In particular seaplane aircrafts must be designed for water loads developed during take-off and landing with the seaplane in any attitude likely to occur in normal operation at appropriate forward and sinking velocities under the most severe sea conditions [1]. In order to make a stress analysis of seaplane floats, and especially of the members connecting the floats with the fuselage, it is of great importance to determine the maximum pressure acting on the floats during landing [1,2,6]. The impact in water is a very complicated phenomenon due to the interaction between the hydrodynamic field and the structures so the possibility to investigate its characteristics by means of a scaled model seems straightforward. In general the similarity procedure requires the scaling of different properties (mass, length, speed, etc.) in order to properly represent such a phenomenon. In the present case the fluid-dynamic phenomena are scaled thanks to the Froude similarity while the definition of specific material and its scaling rules for a complete similarity is required in several cases particularly when composites play a predominant role on the test response. The introduction of TRACE parameter is proposed as a method orienting the designer for the right material selection in these situations [2,3,4,5]. Non-dimensional TRACE behaviour in function of shear-ratio coefficient is shown in figure 1a. Materials can be grouped in classes according to the value of the orthotropic ratio and each class can be scaled by TRACE. Non-dimensional deflection is determined as a function of load parameters and TRACE according to typical material classes definition. The procedure is extended to a typical drop-test impacted on water including structural flexibility [7,8]. Numerical simulation using the LS-DYNA software is used to validate the procedure in predicting the maximum pressure in the first phases of impact (figure 1b and figure 2b). The model shown in figure1b provides the adoption of SPHs, a particular tool adopted for the modelling of a fluid like water. Each SPH (Smoothed Particle Hydrodynamics) is described like a structural FEM node and by a EOS (Equation of State) that describes the mechanical behaviour and interaction with other SPH and the structure. LS-DYNA is an explicit software, so it can simulate dynamic phenomena.
An experimental test is finally designed as shown in figure 2a to calibrate the physical and numerical parameters useful for the definition of SPH properties with the aim to define analyse and correctly describe the dynamics of fluid-structure interaction during a seaplane hull water impact (figure 2b)
Thomas G. Rosenmeyer, Deina ta polla. A Classicist's Checklist of Twenty Literary-Critical Positions
No full textDonnet Daniel. Thomas G. Rosenmeyer, Deina ta polla. A Classicist's Checklist of Twenty Literary-Critical Positions. In: L'antiquité classique, Tome 58, 1989. pp. 309-310
Studio delle proprietà fisiche e reologiche di vetri archeologici tramite confronto con materiali di sintesi.
No full textIl Lavoro caratterizza vetri protostorici e loro analoghi sintetici mediante prove fisico-chimiche e reologiche
Protohistoric vitreous materials and synthetic analogues: study of chemico-physical and rheological.
No full text
Numerical and experimental structural characterization of composite advanced joint for ultra light aerospace platforms
No full textIn the present work, the results of a numerical campaign aimed to evaluate the progressive damage failure
analysis (PDFA) of a specific advanced pin-hole connection under tensile and compressive loads are presented.
The proposed numerical models are based on the application of constitutive material models available in LSDYNA. High fidelity shell-cohesive method was employed to represent composite delamination behavior. In this
model each lamina has been modeled separately with the application of interlaminar cohesive elements.
Preliminary experimental/numerical correlation indicates that the selected modeling technique predicts
experimental results when compared to the proposed laboratory test results. A reduced computational cost has
been also determined. The location and extension of the predicted fracture during the damage process are
comparable to experimental observations. The proposed methodology demonstrates its preliminary ability to be
used for design of composite joints up to failure. Specific outcomes have been also pointed out
Coupled thermo-mechanical numerical modelling of carbon fibre reinforced composites impacted with different projectile configurations
Full text linkA key challenge in building a predictive numerical model for composite structures is the ability to accurately characterize their failure behaviour, especially under impact loading. In this paper, a coupled thermo-mechanical modelling technique and the associated numerical simulations of carbon fibre-reinforced composite panels under the high-velocity impact (HVI) are introduced. The modelling technique aims to evaluate the progressive damage failure analysis (PDFA) of a flat composite panel made of T800/F3900 unidirectional carbon fibre and epoxy, with 16-ply in a quasi-isotropic layup configuration [(0/90/45/-45)2]S. Mechanical characterization test data of the proposed composite materials have been obtained from FAA experimental campaign. High fidelity complete stacked shell-cohesive method is implemented to evaluate composite delaminations and intralaminar damage. The heat generated due to the projectile kinetic energy and impact-induced damage energy transformation is investigated with the proposed numerical coupled model. Thermal effects on the mechanical performance of composite targets are investigated based on the application of the constitutive transient thermal coupling method available in LS-DYNA®. Moreover, the explicit dynamic finite element analysis presented considers four characteristic aerospace projectiles to compare the development of the damage generated during normal highvelocity impact events. The impact response results of the selected projectile configurations, including rubber cylindrical projectile, bird-like projectile, CFRP composite platelike projectile, and ASTM D8101 aluminium axisymmetric projectile, are compared. Impactors with equivalent kinematic energy are investigated with emphasis on energy transfer mechanisms and the local projectile-induced target deformation, damage, and failure. The study introduces the proposed modelling techniques, energy transfer phenomenon, and damage mechanisms that are observed in the target plates. The proposed numerical technique will be used in future research works to investigate engine bird-strike events and the consequently Fan Blade-Out (FBO) scenario to increase the reliability of aerospace structures and to improve the design numerical methods
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