Search results for " effect"
showing 10 items of 7524 documents
The enrichment ratio of atomic contacts in crystals, an indicator derived from the Hirshfeld surface analysis
2014
An enrichment ratio is derived from the decomposition of the crystal contact surface between pairs of interacting chemical species. The propensity of different contact types to form is investigated.
Improvement of catalytic activity over Cu--Fe modified Al-rich Beta catalyst for the selective catalytic reduction of NOx with NH3
2016
Copper and iron bimetal modified Al-rich Beta zeolites from template-free synthesis were prepared for selective catalytic reduction (SCR) of NOx with NH3 in exhaust gas streams. Comparing to the Cu-based and Fe-based mono-component Beta catalysts, Cu(3.0)-Fe(1.3)-Beta bi-component catalyst shows better low-temperature activity and wider reaction-temperature window. Over 80% of NO conversion can be achieved at the temperature region of 125–500 °C. Due to the synergistic effect of copper and iron evidenced by XRD, UV–Vis–NIR, EPR and XPS measurements, the dispersion state of active components as well as the ratio of Cu2+/Cu+ and Fe3+/Fe2+ were improved over Cu(3.0)-Fe(1.3)-Beta. Isolated Cu2+…
Combined TL and 10B-alanine ESR dosimetry for BNCT
2004
The dosimetric technique described in this paper is based on electron spin resonance (ESR) detectors using an alanine-boric compound acid enriched with 1 0 B, and beryllium oxide thermoluminescent (TL) detectors; with this combined dosimetry, it is possible to discriminate the doses due to thermal neutrons and gamma radiation in a mixed field. Irradiations were carried out inside the thermal column of a TRIGA MARK II water-pool-type research nuclear reactor, also used for Boron Neutron Capture therapy (BNCT) applications, with thermal neutron fluence from 10 9 to 10 1 4 n t h cm - 2 . The ESR dosemeters using the alanine-boron compound indicated ESR signals about 30-fold stronger than those…
Influence of oxide substrates on monolayer graphene doping process by thermal treatments in oxygen
2019
Abstract The structural and the electronic properties of monolayer graphene made by chemical vapor deposition and transferred on various oxide substrates ( SiO 2 , Al 2 O 3 , and HfO 2 ) are investigated by Raman Spectroscopy and Atomic Force Microscopy in order to highlight the influence of the substrate on the features of p-doping obtained by O 2 thermal treatments. By varing the treatment temperature up to 400 °C, the distribution of the reaction sites of the substrates is evaluated. Their total concentration and the consequent highest doping available is determined and it is shown that this latter is linked to the water affinity of the substrate. Finally, by varing the exposure time to …
Thermal Properties, Raman Spectroscopy and Tem Images of Neutron-Bombarded Graphite
2013
Neutron-irradiated graphite to a total dose of 3.6 × 1016 n cm−2 was studied by DSC, Raman spectroscopy and transmission electron microscopy (TEM). The Wigner energy of neutron-irradiated graphite was 9.5 J/g as measured by DSC; it was released with an exothermal peak at 220°C. The Raman spectroscopy has confirmed the expected effect caused by neutron irradiation of the graphite substrate. The TEM imaging has shown that neutron-irradiated graphite can be effectively exfoliated by sonication in comparison to pristine graphite, which under similar conditions does not exfoliate at all. The interstitial Frenkel defects in neutron-irradiated graphite are intercalated between the graphene layers …
Dose calculation in biological samples in a mixed neutron-gamma field at the TRIGA reactor of the University of Mainz
2010
To establish Boron Neutron Capture Therapy (BNCT) for non-resectable liver metastases and for in vitro experiments at the TRIGA Mark II reactor at the University of Mainz, Germany, it is necessary to have a reliable dose monitoring system. The in vitro experiments are used to determine the relative biological effectiveness (RBE) of liver and cancer cells in our mixed neutron and gamma fi eld. We work with alanine detectors in combination with Monte Carlo simulations, where we can measure and characterize the dose. To verify our calculations we perform neutron fl ux measurements using gold foil activation and pin-diodes . Material and methods . When L- α -alanine is irradiated with ionizing …
EPR DOSIMETRY IN A MIXED NEUTRON AND GAMMA RADIATION FIELD
2004
Suitability of Electron Paramagnetic Resonance (EPR) spectroscopy for criticality dosimetry was evaluated for tooth enamel, mannose and alanine pellets during the 'international intercomparison of criticality dosimetry techniques' at the SILENE reactor held in Valduc in June 2002, France. These three materials were irradiated in neutron and gamma-ray fields of various relative intensities and spectral distributions in order to evaluate their neutron sensitivity. The neutron response was found to be around 10% for tooth enamel, 45% for mannose and between 40 and 90% for alanine pellets according their type. According to the IAEA recommendations on the early estimate of criticality accident a…
Ni(II) and Pd(II) complexes of camphor-derived diazadiene ligands: steric bulk tuning and ethylene polymerization
1998
Abstract Nickel(II) and palladium(II) centers were coordinated to a series of chiral 1,4-diazadiene ligands. The ligand backbones are camphor derivatives and the imine nitrogens are attached to independently varied 2- and 2,6-substituted aryl groups. Upon activation with methyl-aluminoxane, the dibromo nickel complexes polymerize ethylene and 1-hexene. The polymerization properties are dependent on the steric features of the aryl substituents on the imine nitrogens.
Electronic and Steric Effects: How Do They Work in Ionic Liquids? The Case of Benzoic Acid Dissociation
2010
The need to have a measure of the strength of some substituted benzoic acids in ionic liquid solution led us to use the protonation equilibrium of sodium p-nitrophenolate as a probe reaction, which was studied by means of spectrophotometric titration at 298 K. In order to evaluate the importance of electronic effect of the substituents present on the aromatic ring, both electron-withdrawing and -donor substituents were taken into account. Furthermore, to have a measure of the importance of the steric effect of the substituents both para- and ortho-substituted benzoic acids were analyzed. The probe reaction was studied in two ionic liquids differing for the ability of the cation to give hydr…
Feedback Linearizing Control of Induction Motor Considering Magnetic Saturation Effects
2015
This paper presents an input-output feedback linearization (FL) control technique for rotating induction motors, which takes into consideration the magnetic saturation of the iron core. Starting from a new formulation of the dynamic model taking into consideration the magnetic saturation expressed in a space-state form in the rotor-flux-oriented reference frame, the corresponding FL technique has been developed. To this aim, a particular care has been given to the choice of nonlinear functions interpolating the magnetic parameters versus the rotor magnetizing current and the corresponding magnetic characteristic. The proposed FL technique has been tested experimentally on a suitably develop…