Search results for "GLASS"
showing 10 items of 1153 documents
Effect of addition of bioactive glass to resin modified glass ionomer cement on enamel demineralization under orthodontic brackets
2019
Background Enamel demineralization and white spot lesions around orthodontic brackets is a common problem associated with fixed orthodontic treatment. Glass ionomer cements (GICs) are commonly used for bracket bonding and recently, bioactive glass (BAG) was added to GICs to enhance deposition of calcium phosphate in adjacent dental structure. This study sought to assess the effect of addition of BAG particles to resin modified GIC (RMGIC) on enamel demineralization under orthodontic brackets. Material and methods In this in vitro, experimental study, 60 sound human premolars were immersed in distilled water at 6°C. The teeth were randomly divided into three groups. Using a sticker, a window…
ELECTRODEPOSITION OF NOVEL POLY(NAPHTHALENEDIIMIDE-QUATERTHIOPHENE) THIN FILMS AND APPLICATIONS IN PLASTIC OPTOELECTRONICS DEVICES
2013
A novel symmetric naphthalenediimide-quaterthiophene derivative (NDIT4d) has been polymerized on different substrates including glassy carbon and ITO/PET electrodes by means of electrochemical methods. XPS and UV-VIS spectroscopy as well as cyclic voltammetry have been employed for characterizing the thin film chemical features, the band gap and the HOMO and LUMO levels. DFT computational studies were in close agreement with the experimental observables also showing intriguing geometrical effects on the band gap energy values. The comparison of the energy levels locations of the electrodeposited poly(naphthalenediimide-quaterthiophene) derivative (e-PNDIT4) and P3HT thin films transferred b…
Static and dynamic mechanical properties of Arundo Donax fillers-epoxy composites
2014
Abstract Aim of this work is to investigate the feasibility of using a natural and inexpensive filler obtained by grinding the culms of Arundo Donax as reinforcement of epoxy resins. The effect of the content and size of Arundo Donax fillers on static and dynamic mechanical properties was evaluated showing that the composites exhibit higher tensile moduli, comparable flexural moduli and lower strength properties in comparison to the neat resin. Moreover, changes in the storage and the loss moduli only above the glass transition temperature (i.e. in the rubbery region) were found while neither significant shifts of tan δ peaks to higher temperatures nor reductions in the peak height of the c…
The effect of alkaline treatment on mechanical properties of kenaf fibers and their epoxy composites
2015
Abstract In this work, kenaf fibers were pre-treated in a NaOH solution (6% in weight) at room temperature for two different periods (48 and 144 h). The chemical treatment of kenaf fibers for 48 h allowed to clean their surface removing each impurity whereas 144 h of immersion time had detrimental effect on the fibers surface and, consequently, on their mechanical properties. Untreated and NaOH treated kenaf fibers (i.e. for 48 h) were also used as reinforcing agent of epoxy resin composites. The effect of the stacking sequence (i.e. using unidirectional long fibers or randomly oriented short fibers) and the chemical treatment on the static mechanical properties was evaluated showing that t…
Realization and drive tests of active thin glass x-ray mirrors
2016
A technique to obtain lightweight and high-resolution focusing mirror segments for large aperture X-ray telescopes is the hot slumping of thin glass foils. In this approach, already successfully experimented to manufacture the optics of the NuSTAR X-ray telescope, thin glasses are formed at high temperature onto a precisely figured mould. The formed glass foils are subsequently stacked onto a stiff backplane with a common axis and focus to form an XOU (X-ray Optical Unit), to be later integrated in the telescope optic structure. In this process, the low thickness of the glass foils guarantees a low specific mass and a very low obstruction of the effective area. However, thin glasses are sub…
CFD prediction of bubble behavior in two-dimensional gas-solid fluidized beds
2009
This work focuses on the computational fluid dynamics (CFD) simulation of a laboratory-scale, two-dimensional fluidized bed and the relevant experiments in order to validate the prediction capability of the adopted codes and models. Both experimental and computational quantitative data were analyzed by means of an original digital image analysis technique, allowing for coherent comparison of computational and experimental results. In particular, this work analyzes the capability of the CFD simulations in predicting the fluctuating behavior of bubbling fluidized beds by means of frequency analysis of bubble-related phenomena.
<title>Dot-matrix holographic recording in amorphous chalcogenide films</title>
2006
We have developed PC controlled dot-matrix holographic recording system based on the CW diode pumped YAG:Nd SHG laser (wavelength 532 nm, power 30mW,) modulated electronically with TTL signals. Two-beam technique has been used with convergence angle 30o and PC controlled incident beam plane rotation 0-360o. Optical system consists of beam splitter, 40mm focus length forming cylindrical lens and 40mm focusing lens. Characteristic parameters of experimental equipment are following: spot size - 50-200 micrometers, direct laser writing area, limited by x-y positioning system, was 70mm x 70mm, number of writing head rotation positions up to 256 (8 bit), time of each exposure - 1-1000 msec. As th…
Improving the Long‐Term Stability of Doped Spiro‐Type Hole‐Transporting Materials in Planar Perovskite Solar Cells
2021
The improvement of the long-term stability of perovskite-based solar cells (PSCs) toward commercialization is closely linked to the development of cutting-edge charge-transporting materials. The progress on the design and the synthesis of new hole-transporting materials (HTMs) is synergistically attaining both top efficiencies and promising stability. Herein, the synthesis and characterization of two doped-HTMs based on electron-rich spiranic cores, namely, 9H-quinolinophenoxazine (spiro-POZ) and 9H-quinolinophenothiazine (spiro-PTZ), are presented. The novel HTMs exhibit excellent solubility, optimal highest occupied molecular orbital energy, and excellent thermal stability with glass tran…
50 mJ/30 ns FTIR Q-switched diode-pumped Er:Yb:glass 1.54 μm laser
2001
Abstract 50 mJ Q-switched output at 30 ns pulse duration was demonstrated with a transversely diode-pumped bulk Er 3+ :Yb 3+ :glass 1.54 μm laser system of uncomplicated and compact design, using a piezoelectrically driven FTIR shutter. In long-pulse operation, 360 mJ output was obtained for 2.65 J incident optical pump energy. Maximum optical slope efficiencies of 20.5% and 5.4% were measured in long-pulse and Q-switched operation, respectively. Optimum Q-switch timing was studied taking into account the Yb 3+ →Er 3+ energy transfer process and was correlated with free-running delay parameters.
EXPERIMENTAL AND NUMERICAL EVALUATION OF THE MECHANICAL BEHAVIOUR OF GFRP SANDWICH PANELS
2007
This work deals with the analysis of the mechanical behaviour of a class of sandwich structures widely employed in marine constructions, constituted by fiber-glass laminate skins over PVC foam or polyester mat cores. In detail, a systematic experimental study and numerical simulations have shown that the theoretical prediction of the strength and the actual failure mechanism of these sandwich structures can be affected by significant errors, specially in the presence of prevalent shear loading. Moreover, because of the low shear stiffness and the elastic constants mismatch of the skins and core material, failure modes and strength are strongly influenced by eventual stresses orthogonal to t…