Search results for "visual_art"
showing 10 items of 2987 documents
Modeling the influence of mineral content and porosity on ultrasound parameters in bone by using synthetic phantoms
1999
Model composite media − 10×15×80 mm3 bone tissue phantoms based on an epoxy resin with fillers—were made to study the influence of porosity and mineral content on ultrasound velocity and attenuation. The pores were simulated by ∼ 1 mm3 particles of a soft rubber, while the mineral content was imitated by a mineral residue of natural bone obtained by burning and grinding. The porosity and mineral content were varied in the range of 0–70% by volume with a step of 10%. The velocity, attenuation, and prevalent frequency of ultrasound were measured by the pulse transition method, using transducers with nominal frequencies 0.1, 0.2, 0.5, and 1.0 MHz. It was experimentally found that the ultrasoun…
A novel configuration for the optical characterization of waveguiding layers
1991
When a transparent layer of sufficient thickness is suitably coated on both sides with metal, the structure supports one-dimensionally bound optical modes which propagate in two dimensions but which can be detected externally in a very simple manner. We show that this configuration can be used to determine the optical constants of the layer.
Thermal and dynamic mechanical properties of beeswax-halloysite nanocomposites for consolidating waterlogged archaeological woods
2015
Abstract Thermal and mechanical properties were determined for the halloysite nanotubes (HNT)/beeswax composites at various compositions. The beeswax degradation temperatures and time course, provided by thermogravimetry (TG), evidenced the improvement of the thermal properties operated by HNT. Differential scanning calorimetry (DSC) allowed us to determine the enthalpy of melting as well as the time course of the melting process for beeswax. A slight loss of beeswax crystallinity was observed upon HNT addition. The dynamical mechanical analysis (DMA) provided the loss and the storage modulus for the nanocomposites upon heating and it was shown that the nanoclays create an inorganic framewo…
Preparation and Characterization of Composites Materials with Rubber Matrix and with Polyvinyl Chloride Addition (PVC)
2020
An important problem that arises at present refers to the increase in performances in the exploitation of the conveyor belts. Additionally, it is pursued to use some materials, which can be obtained by recycling rubber and PVC waste, in their structure. Thus, the research aimed at creating conveyor belts using materials obtained from the recycling of rubber and PVC waste. Under these conditions, conveyor belts were made that had in their structure two types of rubber and PVC, which was obtained by adding in certain proportions of reclaimed rubber and powder obtained from grinding rubber waste. In order to study the effect of adding PVC on properties, four types of conveyor belts were made, …
Cyclic moisture sorption and its effects on the thermomechanical properties of epoxy and epoxy/MWCNT nanocomposite
2019
The aim of this work was to reveal the moisture absorption&ndash
Dielectric investigation of sodium potassium niobate ceramic doped 7% of antimony
2012
Abstract Electric properties of sodium potassium niobate ceramic doped antimony (Na0.5K0.5)(Nb0.93Sb0.07)O3 with sintering aid MnO2 (0.5 mol% MnO2) (KNNSbx + 0.5Mn) were investigated in a broad frequency (from 1 Hz to 54 GHz) and temperature (from 110 K to 800 K) ranges. The mean relaxation times calculated from the dielectric permittivity measurements fulfill Arrhenius relationship with dipole activation energy EA = 3409 K (EA/kB = 0.29 eV). The DC conductivity has been extracted from experimental results and the activation energy was calculated EA = 11733.78 K (EA/kB = 1.011 eV).
INFLUENCE OF MONOXIDES ADDITION ON SINTERING OF SODIUM-POTASSIUM NIOBATES SOLID SOLUTION
2008
ABSTRACT In this paper the preparation, structure and dielectric parameters of ceramics from different powders of pure potassium sodium niobate (KNN) and KNN doped with 1.0 wt% of Li2O, CdO, Bi2O3, MnO2, V2O5 and WO3 have been studied. The dopping of sintering aids did not affect the crystallographic structure of the ceramics significantly; all ceramic samples had a single-phase perovskite structure. Added elements Li2O, CdO, MnO2, V2O5 effectively decreased the sintering temperature of KNN (50°–80°C). All sintering aids influenced sinterability, microstructure and dielectric properties of ceramics. Dielectric constant for doped samples increased from 6000 up to 8000.
Metal–organic covalent network chemical vapor deposition for gas separation
2016
The chemical vapor deposition (CVD) polymerization of metalloporphyrin building units is demonstrated to provide an easily up-scalable one-step method toward the deposition of a new class of dense and defect-free metal–organic covalent network (MOCN) layers. The resulting hyper-thin and flexible MOCN layers exhibit outstanding gas-separation performances for multiple gas pairs.
Comparative study of the radiopacity of resin cements used in aesthetic dentistry
2015
PURPOSE. The aim of this study was to compare the radiopacity of 6 modern resin cements with that of human enamel and dentine using the Digora digital radiography system, to verify whether they meet the requirements of ANSI/ADA specification no. 27/1993 and the ISO 4049/2000 standard and assess whether their radiopacity is influenced by the thickness of the cement employed. MATERIALS AND METHODS. Three 3-thickness samples (0.5, 1 and 1.5 mm) were fabricated for each material. The individual cement samples were radiographed on the CCD sensor next to the aluminium wedge and the tooth samples. Five radiographs were made of each sample and therefore five readings of radiographic density were ta…
A Raman spectroscopy study of the oxidation processes in synthetic chromite FeCr2O4
2020
Abstract A crystal of synthetic chromite FeCr2O4 has been annealed in air at 700 °C for 50 days at room pressure in order to study physical-chemical changes. After the annealing treatment, Scanning Electron Microscopy (SEM) images of the polished surface of the sample showed areas of different composition. Detailed Raman mapping revealed that the annealed chromite undergoes an oxidation process, proceeding inwards from the outer surface and leading to the transformation of chromite to magnetite, and ultimately to hematite. The oxidation process also leads to the formation of trellis-like lines, arguably via stress-related mechanisms associated with the phase transformation and consequent vo…