Search results for "MECHANICS"

Misfit evaluation of dental implant-supported metal frameworks manufactured with different techniques: Photoelastic and strain gauge measurements

2016

This study aims to compare in-vitro the fitting accuracy of implant-supported metal frameworks used for full-arch orthodontic restoration. The hypotheses tested were as follows: (1) for a fixed implant morphology, strains developed within the framework depend on how the framework had been fabricated and (2) stresses transferred to the implant–bone interface are related to the amount of framework misfit. Metal frameworks were fabricated using four different manufacturing techniques: conventional lost-wax casting, resin cement luting, electrospark erosion, and computer-aided design/computer-aided manufacturing milling. Each framework was instrumented with three strain gauges to measure strai…

The modelling of the behaviour of solid inclusions in the EM induced recirculated turbulent flows of liquid metal

2014

Promocijas darbā skaitliski un eksperimentāli pētītas noslēgtas elektromagnētiski ierosinātas šķidrā metāla turbulentās plūsmas ar cietām daļiņām. Šādas plūsmas veidojas metalurģiskajās indukcijas krāsnīs. Darbā ir izveidots uz LES plūsmas aprēķina pieejas bāzēts Lagranža modelis ar paplašinātu spēku kopu inerciālo daļiņu pārneses aprakstam. Veikts eksperimentāls daļiņu koncentrācijas pētījums kvazi-stacionārā stāvoklī, izmantojot jaunu ideju: ferromagnētiskās daļiņas izmantotas kā nevadošu daļiņu fiziskais modelis šķidrajā metālā - tas ir pirmais zināmais eksperimentālais darbs cietu ieslēgumu sadalījuma analīzē elektormagnētiski ierosinātu šķidro metālu plūsmu iekšienē. Eksperiments pierā…

Serious game design : supporting collaborative learning and investigating learners' experiences

2014

Sobre la naturalización de la lógica*

2003

El presente artículo se ocupa de dar razones en contra de la naturalización de la lógica, en tanto en cuanto esto signifique una revisión de esta ciencia. El trabajo critica cada uno de los intentos históricos importantes que ha habido de revisión de las leyes lógicas -- intuicionismo, lógica cuántica, lógicas alternativas - y también intenta argumentar que el problema de la interpretación de la mecánica cuántica no tiene nada que ver con la naturalización de la lógica. This article is devoted to give reasons against the naturalization of logic, in a sense which entails a revision of this science. The paper criticizes each historical important attempt to revise logical laws - intuitionism, …

BEM analysis of a piezoelectric structural health monitoring system for delamination detection

2013

In the present work a piezoelectric based structural health monitoring (SHM) system is analyzed with the aim of assessing the ability of the piezoelectric patch to detect both edge and embedded delaminations proper of flange-skin composite laminated structures. he boundary element model is developed for piezoelectric solids and is implemented by taking advantage of the multidomain technique to model laminated and cracked configurations. A non-linear spring model interface is then implemented in conjunction with an iterative procedure allowing for the simulation of the finite stiffness of the bonding layers as well as of the non-penetration condition of the delamination surfaces. he dynamic …

Fracture and fatigue of titanium narrow dental implants: New trends in order to improve the mechanical response

2019

Sixty-four fractured commercially pure titanium (cp-Ti) narrow dental implants (NDIs) with similar macrogeometry and connection designs were studied after different implantation times in humans in order to determine their reliability and to evaluate the causes of the fracture. These NDIs were compared with other similar implants, made with alloyed titanium with 15% Zr and with 12% strained titanium. Original implants were tested under static and fatigue conditions, simulating the tri-axial loads in the mouth by means of a Bionix hydraulic test machine. Fractography was studied using field-emission scanning electron microscopy (FSEM). The results showed that cp-Ti NDI exhibits low strength f…

Self-Consistent Charge Density-Functional Tight-Binding Parametrization for Pt–Ru Alloys

2017

We present a self-consistent charge density-functional tight-binding (SCC-DFTB) parametrization for PtRu alloys, which is developed by employing a training set of alloy cluster energies and forces obtained from Kohn-Sham density-functional theory (DFT) calculations. Extensive simulations of a testing set of PtRu alloy nanoclusters show that this SCC-DFTB scheme is capable of capturing cluster formation energies with high accuracy relative to DFT calculations. The new SCC-DFTB parametrization is employed within a genetic algorithm to search for global minima of PtRu clusters in the range of 13-81 atoms and the emergence of Ru-core/Pt-shell structures at intermediate alloy compositions, consi…

Effects of Polyacrylic Acid Pre-Treatment on Bonded-Dentine Interfaces Created with a Modern Bioactive Resin-Modified Glass Ionomer Cement and Subjec…

2018

Objectives: Resin-modified glass ionomer cements (RMGIC) are considered excellent restorative materials with unique therapeutic and anti-cariogenic activity. However, concerns exist regarding the use of polyacrylic acid as a dentine conditioner as it may influence the bonding performance of RMGIC. The aim of this study was to evaluate the effect of different protocols for cycling mechanical stress on the bond durability and interfacial ultramorphology of a modern RMGIC applied to dentine pre-treated with/without polyacrylic acid conditioner (PAA). Methods: The RMGIC was applied onto human dentine specimens prepared with silicon-carbide (SiC) abrasive paper with or without the use of a PAA c…

Pro-Degradant Activity of Naturally Occurring Compounds on Polyethylene in Accelerate Weathering Conditions

2019

In this work, naturally occurring compounds, such as Vitamin E (VE) and Ferulic Acid (FA), at high concentrations, have been considered as pro-degradant agents for Low Density Polyethylene (PE). However, all obtained results using the naturally occurring molecules as pro-oxidant agents for PE have been compared with the results achieved using a classical pro-oxidant agent, such as calcium stearate (Ca stearate) and with neat PE. The preliminary characterization, through rheological, mechanical and thermal analysis, of the PE-based systems highlights that the used naturally occurring molecules are able to exert a slight plasticizing action on PE and subsequently the PE rigidity and crystalli…

On the effectiveness of different additives and concentrations on the re-building of the molecular structure of degraded polyethylene

2006

Mechanical recycling is an easy and economic way to re-use plastic waste as secondary materials, but, in general, their properties are worse with respect to the reclaimed materials and the virgin polymer. The aim of this work was to study the effect of concentration and reaction kinetics of two additives, an ethylene-co-glycidyl methacrylate (Lotader) and a hydroxylamine derivative (CGX), in the re-building of a degraded polyethylene. CGX is a nitroxyl radical generator able to form branching in polyolefins while the epoxy groups of Lotader can react with the functional groups present in the recycled polyethylene. The results indicate that the CGX has a higher reaction rate than Lotader, pr…