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Ubeda C.,University of Tarapaca | Vano E.,Complutense University of Madrid | Gonzalez L.,Complutense University of Madrid | Miranda P.,Cardiovascular Service | And 3 more authors.
Radiation Protection Dosimetry | Year: 2010

Interventional cardiology procedures usually imply high doses to the staff, as paediatric cardiologists need to stay closer to the patient than during adult procedures. Also, biplane systems are used that imply an additional source of staff doses. The objective of this paper is to measure scatter doses in four X-ray systems, using polymethyl methacrylate phantoms with thicknesses ranging from 4 to 16 cm to simulate paediatric patients, for the different acquisition modes. Scatter dose rates measured at the position of cardiologist's eyes ranged from 0.8 to 12 mSv h-1, and about twice the above values at lower extremities, as a linear function of the surface air kerma at the phantom, keeping the irradiated area constant. Therefore, the respective personal dose equivalent for the lens of the eyes may be around 0.5 and 1 mSv throughout the procedure, if additional protection is not used. Simultaneous cine acquisition in biplane systems yielded scatter doses to cardiologists, increased by factors from 5 to 21, compared with a single C-arm acquisition case and depending on geometry. Knowledge of scatter doses for different operation modes, patient thicknesses and the biplane operation should help paediatric cardiologists to adopt conservative attitudes in respect of their occupational radiation risks. © The Author 2010. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org. Source

Mangalaraja R.V.,University of Concepcion | Ananthakumar S.,Indian National Institute for Interdisciplinary Science and Technology | Schachtsiek A.,TU Darmstadt | Lopez M.,University of Concepcion | And 2 more authors.
Materials Science and Engineering A | Year: 2010

Nanocrystalline Ce0.9Sm0.1O1.95 electrolyte was prepared by nitrate-fuel combustion technique using urea, citric acid, glycine and polyethylene glycol as organic fuels. The combusted precursors were calcined at 700°C/2h and then compacted to cylindrical pellets and sintered at 1200°C for 2, 4 and 6h durations. The sintered samples were tested for the mechanical hardness and fracture toughness and the results were compared within the fuel sources. Dense nanocrystalline ceria electrolyte membranes having theoretical sintered densities of 98% and the sintered grain sizes below 1μm were successfully achieved at 1200°C. Ceria electrolytes derived from the glycine and citric acid fuels have maximum microhardness of 7.94±0.2 and 7.63±0.2GPa. Whereas high toughness is observed for the samples prepared from the urea and polyethylene glycol fuels. They were estimated as 3.06±0.3 and 3.17±0.3MPam1/2 respectively at 20N. The study significantly contributes to select the fuels appropriately so that the advantages of low temperature densification and mechanically durability can be achieved in ceria electrolyte membranes for IT-SOFC applications. © 2010 Elsevier B.V. Source

Yianatos J.,University of Santa Maria in Ecuador | Contreras F.,University of Santa Maria in Ecuador | Diaz F.,Chilean Commission of Nuclear Energy
Minerals Engineering | Year: 2010

In this work, the measurement of the axial gas holdup profile and gas residence time distribution (RTD), in a 130 m 3 self-aerated flotation cell, is presented. For this purpose, a radioactive tracer gas was activated in the Nuclear Reactor of the Chilean Commission of Nuclear Energy. The gas tracer, Freon 13B1, was injected as an impulse signal at the gas (air) inlet point, located at the top of the cell, from which the gas tracer circulates first through the rotor, where the bubble dispersion occurs, and then the gas becomes well distributed over the whole cross-sectional area before leaving the cell. The axial gas holdup profile was estimated from the transient gas concentration measurement at different depths inside the cell. From these experiments it was found that the air entering the cell was preferentially distributed in the upper half of the cell, while the gas entrainment into tailings was negligible. The mean gas holdup was 8.8%, and consequently the effective pulp volume of collection zone was 91.2%. The gas concentration on top of froth was recorded for RTD measurement of the gas leaving the cell. It was found that the mean gas residence time was around 42 s and the mixing condition for gas and pulp was similar. © 2009 Elsevier Ltd. All rights reserved. Source

Akbari-Fakhrabadi A.,University of Concepcion | Avila R.E.,Chilean Commission of Nuclear Energy | Carrasco H.E.,University of Concepcion | Ananthakumar S.,Indian National Institute for Interdisciplinary Science and Technology | Mangalaraja R.V.,University of Concepcion
Journal of Alloys and Compounds | Year: 2012

NiO-Ce 0.9Gd 0.1O 1.95 (NiO-10GDC) nanocomposite anode material was synthesized through combustion technique for possible low temperature solid oxide fuel cells (LT-SOFCs). A low weight loss is seen in the TG/DTA thermogram that indicates the complete combustion of the reactant mixtures. The powder X-ray diffraction patterns showed that the presence of NiO, GDC and Ni crystallite phases in the as combusted product. Upon calcination at 600 °C, the metallic Ni oxidized to NiO. TEM images showed a wide size distribution of fine spherical GDC and large irregularly shaped NiO particles. This NiO-10GDC anode material was applied over GDC electrolyte as a porous thin layer. Using this surface engineered GDC electrolyte a semi-cell (electrode/electrolyte structure) was fabricated. The electrical conductivity of the semi-cell was characterized with respect to temperature. © 2012 Published by Elsevier B.V. Source

Yianatos J.,University of Santa Maria in Ecuador | Bergh L.,University of Santa Maria in Ecuador | Vinnett L.,University of Santa Maria in Ecuador | Contreras F.,University of Santa Maria in Ecuador | Diaz F.,Chilean Commission of Nuclear Energy
Minerals Engineering | Year: 2010

The batch flotation process has been commonly characterized assuming a flotation rate distribution function F(k), e.g.: Dirac delta, Rectangular, Gamma or Weibull functions. The identification of F(k) for the collection zone of continuous industrial cells is more complex and to the authors knowledge, has not been reported yet. In this work, a novel procedure to estimate the flotation rate distribution from the collection zone of industrial flotation cells, using the radioactive tracer technique, is presented. The approach consists of measuring the impulse response of the floatable mineral tracer concentration, and non-floatable gangue tracer concentration (Residence Time Distribution, RTD), in the cell tailings. Then, the floatable tracer concentration can be compared with the model prediction, using the Gamma function and the RTD of the non-floatable tracer. Thus, the F(k) distribution parameters were obtained by means of the least-square estimation. The new approach was successfully tested in industrial rougher flotation cells of large size. © 2010 Elsevier Ltd. All rights reserved. Source

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