Search results for "visual_art"

Exothermic adsorption of chromate by goethite

2020

Abstract Goethite is a common Fe oxyhydroxide coating soil particle surfaces, which has a high Cr(VI) adsorption capacity under acidic pH conditions. Batch equilibrium adsorption experiments with chromate concentrations of 0.1, 0.2, and 0.3 mM were performed using solutions with ionic strengths of 0.1, 0.05, and 0.01 M and pH values of 3–11 and at four temperatures between 10 and 75 °C. The results of these experiments show that the amount of chromate adsorbed decreases as the pH increases towards the zero-point-of-surface-charge of goethite (pHPZC 9.1), which is typical for anions. The chromate adsorption efficiency also depends on the ionic strength of the solution. The amount of chromate…

Modelling of phase transitions and residual thermal stress of CTBN rubber modified epoxy resins during a pultrusion process

2007

Abstract The implicit finite difference and fourth order Runge-Kutta method are used both to solve the heat transfer problem in the pultrusion reaction and to calculate the temperature and conversion distributions within a thermoset composite profile. The aim of our work is to study the influence of a rubbery phase added to the epoxy matrix in production conditions. The results have shown that the rubber modified systems have a low exothermic temperature peak value, so that neither the amount of cured resin nor the final product properties are limited. First of all we will show that the phase transition (gelation and vitrification) zones within the die change as the amount of rubber varies …

The fate of silver ions in the photochemical synthesis of gold nanorods: an Extended X-ray Absorption Fine Structure analysis

2009

Water-soluble gold nanorods (Au NRs) were synthesized using a silver-ion mediated photochemical route under UV irradiation. Extended X-ray Absorption Fine Structure (EXAFS) measurements on the Ag K-edge were performed on samples obtained at different Ag/Au ratios and at increasing irradiation times in order to investigate the fate of silver ions during the growth of Au NRs. EXAFS measurements allowed to probe the chemical state and the local environment of silver in the final product. Experimental data suggest that Ag atoms are placed on top of the Au particles as metallic Ag(0), while no significant contribution to the EXAFS spectra comes from AgBr or other Ag(+) based species. The reporte…

Sulfur-free pulping of hot-water-extracted spruce sawdust

2016

Softwood (Picea abies) sawdust was hot-water-extracted with two multi-phase processes (160-180°C, 100-280 min, and liquor-to-wood ratio 5 l/kg) corresponding to P-factors of ~780 (yield 80.0%) and ~4580 (yield 72.4%). The pre-treated materials were then pulped with the soda-AQ cooking (170°C, NaOH charge 20%, AQ charge 0.1%, 30-150 min, and liquor-to-wood ratio 5 l/kg), resulting in a yield range of 36.1-61.4% (for reference cooks without pre-extraction 47.9-60.0%). It was observed that the pre-extraction under moderate conditions enhanced the dissolution especially of large-molar-mass lignin during cooking, and the total amount of the dissolved lignin was also higher than that removed from…

Microwave harmonic emission in MgB2 superconductor: Comparison with YBA2CU3O7

2006

We report results of microwave second-harmonic generation in ceramic samples of MgB2, prepared by different methods. The SH signal has been investigated as a function of the temperature and the static magnetic field. The results are discussed in the framework of models reported in the literature. We show that the peculiarities of the SH signal are related to the specific properties of the sample. A comparison with the results obtained in ceramic and crystalline YBa2Cu3O7 shows that the second-harmonic emission in MgB2 is weaker than that observed in ceramic YBa2CuO7. (c) 2006 Wiley Periodicals, Inc.

Comparison between FSW and bonded lap joints - A preliminary investigation

2017

Difficult to weld aluminium alloys can be effectively joined by different alternative processes. Friction Stir Welding (FSW), among the solid-state processes and adhesive bonding represent two very attractive techniques. They allow the production of highly resistant joints avoiding the formation of the typical fusion weld defects. The aim of this work is to identify, analyse and compare the mechanical properties of AA6016 aluminium alloy joints made out of 1 mm thick sheets. FSW lap joints were and epoxy bonded joints were produced. Using the FSW results as benchmark, the overlap required in the bonded joint was identified to ensure the same static strength. Once the geometric configuration…

2016

The structure–property relationship study of a series of cationic Ir(III) complexes in the form of [Ir(C^N)2(dtBubpy)]PF6 [where dtBubpy = 4,4′-di-tert-butyl-2,2′-bipyridine and C^N = cyclometallating ligand bearing an electron-withdrawing group (EWG) at C4 of the phenyl substituent, i.e., −CF3 (1), −OCF3 (2), −SCF3 (3), −SO2CF3 (4)] has been investigated. The physical and optoelectronic properties of the four complexes were comprehensively characterized, including by X-ray diffraction analysis. All the complexes exhibit quasireversible dtBubpy-based reductions from −1.29 to −1.34 V (vs SCE). The oxidation processes are likewise quasireversible (metal + C^N ligand) and are between 1.54 and …

Label swapper device for spectral amplitude coded optical packet networks monolithically integrated on InP

2011

In this paper the design, fabrication and experimental characterization of an spectral amplitude coded (SAC) optical label swapper monolithically integrated on Indium Phosphide (InP) is presented. The device has a footprint of 4.8x1.5 mm 2 and is able to perform label swapping operations required in SAC at a speed of 155 Mbps. The device was manufactured in InP using a multiple purpose generic integration scheme. Compared to previous SAC label swapper demonstrations, using discrete component assembly, this label swapper chip operates two order of magnitudes faster. © 2011 Optical Society of America.

Formation of lead by reduction of electrodeposited PbO2: comparison between bulk films and nanowires fabrication

2012

Metallic lead was deposited, both in form of bulk films and nanowire array within pores of anodic alumina membranes, following a new two-step procedure, consisting in anodic electrodeposition of α-PbO2, followed by its reduction to metallic lead. This method allows to overcome drawbacks of the “direct” electrodeposition of lead from aqueous solution, consisting, essentially, in the formation of dendritic deposits. Here, we report the comparison between results obtained in the two cases and discuss the kinetic of oxide reduction both for films and nanowires. Deposit morphology and structure are also discussed. We have found that reduction of α-PbO2 films proceeds always at high speed and uni…

Electrical characterization of deoxyribonucleic acid hybridization in metal-oxide-semiconductor-like structures

2012

In this work, metal-oxide-semiconductor (MOS)-like sensors in which deoxyribonucleic acid (DNA) strands are covalently immobilized either on Si oxide or on a gold surface were electrically characterized. Si oxide fabrication process allowed us to have a surface insensitive to the solution pH. A significant shift in the flat band voltage was measured after single strand DNA immobilization (+0.47 +/- 0.04 V) and after the complementary strand binding (+0.07 +/- 0.02 V). The results show that DNA sensing can be performed using a MOS structure which can be easily integrated in a more complex design, thus avoiding the problems related to the integration of micro-electrochemical cells.