Time filter

Source Type

Manresa, Spain

Turo A.,Polytechnic University of Catalonia | Chavez J.A.,Polytechnic University of Catalonia | Garcia-Hernandez M.J.,Polytechnic University of Catalonia | Bulkai A.,Invention and Research Center Services Co. | And 4 more authors.
Measurement: Journal of the International Measurement Confederation | Year: 2013

The demand for powder metallurgy (P/M) parts in its traditional automotive market is predicted to grow, but future sector expansion depends directly upon its capability to manufacture zero-defect parts for industries such as aerospace and medicine. The lack of adequate inspection systems has important implications from the point of view of quality assurance, since it increases the costs, time and wasted material. In recent years the applicability of several techniques for the inspection of P/M parts has been investigated, such as Eddy current testing, computer tomography or X-ray imaging, but studies have revealed that all of them have deficiencies that make them unavailable for a complete and reliable flaw detection and density defect recognition. A new inspection tool has been developed based on pulse echo ultrasonic technology combined with robotics, which makes it possible to provide a global density map of sintered. © 2012 Elsevier Ltd. All rights reserved. Source

Torrento C.,Institute Of Diagnosi Ambiental I Estudis Of Laigua Idaea | Urmeneta J.,University of Barcelona | Otero N.,University of Barcelona | Soler A.,University of Barcelona | And 2 more authors.
Chemical Geology | Year: 2011

Using chemical, isotopic and microbiologic techniques we tested in laboratory experiments the extent to which the addition of pyrite to groundwater and sediments from a nitrate-contaminated aquifer could stimulate denitrification by indigenous bacteria. In addition to this biostimulated approach, a combined biostimulated and bioaugmented treatment was also evaluated by inoculating the well-known autotrophic denitrifying bacterium Thiobacillus denitrificans. Results showed that the addition of pyrite enhanced nitrate removal and that denitrifying bacteria existing in the aquifer material were able to reduce nitrate using pyrite as the electron donor, obviating the need for the inoculation of T. denitrificans. The results of the 16S rRNA and nosZ gene-based DGGE and the quantitative PCR (qPCR) showed that the addition of pyrite led to an increase in the proportion of denitrifying bacteria and that bacterial populations closely related to the Xanthomonadaceae might probably be the autotrophic denitrifiers that used pyrite as the electron donor. Not only autotrophic but also heterotrophic denitrifying bacteria were stimulated through pyrite addition and both populations probably contributed to nitrate removal. Isotopic analyses (δ15N and δ18ONO3) were used to monitor enhanced denitrification and the N and O isotopic enrichment factors (-26.3±1.8‰ and -20.4±1.3‰, respectively) allowed to calculate the degree of natural nitrate attenuation in the aquifer. Furthermore, flow-through experiments amended with pyrite confirmed the long-term efficiency of the process under the study conditions. Further research under field conditions is needed to determine whether stimulation of denitrification by pyrite addition constitutes a feasible bioremediation strategy for nitrate-contaminated aquifers. © 2011 Elsevier B.V. Source

Nothhaft K.,TU Munich | Suh J.,TU Munich | Golle M.,Pforzheim University | Picas I.,Center Tecnologic | And 2 more authors.
Production Engineering | Year: 2012

In order to cope with the difficulties of shearing operations of press hardened steels, this work attempted to optimize these processes. Herefore, it is necessary to reduce the press forces and stresses in tools, while still obtaining adequate sheared edge quality levels. To reach this goal, different punch chamfer angles (0°, 2°, 7° and 20°) and relative cutting clearances (5, 10 and 15 % of the sheet thickness) were tested in a cutting tool, which was adapted in a way that different active elements could be mounted. The tool was equipped with a measurement system, which allowed the determination of the process forces in three dimensions at each punch stroke. Basis was an AlSi coated 22MnB5 sheet with a thickness of 1. 5 mm. In addition a finite element model was developed to predict the stress distribution in tools and the sheared edge qualities. According to the experimental results the application of a 20° chamfer angle succeeded to reduce the forces and stresses of tools, but the sheared parts had a poor quality. In contrast, the 7° chamfer angle gave lowest tool stresses and sufficient part qualities, but the forces were very high. The simulation results agreed with the experimental data, except for the prediction of the rollover zone. These deviations were attributed among others to the presence of the AlSi coating, which was not considered. © 2012 German Academic Society for Production Engineering (WGP). Source

Gimenez J.,Polytechnic University of Catalonia | Pablo J.D.,Polytechnic University of Catalonia | Pablo J.D.,Center Tecnologic | Martinez M.,Polytechnic University of Catalonia | And 3 more authors.
Journal of Colloid and Interface Science | Year: 2010

Natural hematite was used for the removal of arsenic(III) and arsenic(V) from aqueous solution. The experimental breakthrough curves were obtained in fixed-bed columns. The transport of arsenic in a simplified fixed-bed configuration was quantified by using the CXTFIT code, which was used to estimate the transport and sorption parameters of the convective-dispersive equation (CDE) and the two-site deterministic nonequilibrium (TSM/CDE) model by fitting the models to the experimental breakthrough curves (BTC). The prediction of the breakthrough curves performed by the two-site nonequilibrium sorption model resulted in a good fit, indicating that this model can properly describe the transport and sorption processes of arsenic on natural hematite. Additionally the parameters obtained indicate that nonequilibrium sorption governs the As(III) and As(V) uptake onto hematite in a fixed-bed column. No significant differences in the transport and sorption parameters of As(III) and As(V) on natural hematite were obtained; the retardation factor values were in the same order of magnitude for both species. © 2010 Elsevier Inc. Source

Serrano-Purroy D.,Institute for Transuranium Elements | Clarens F.,Center Tecnologic | Gonzalez-Robles E.,Center Tecnologic | Glatz J.P.,Institute for Transuranium Elements | And 6 more authors.
Journal of Nuclear Materials | Year: 2012

Two weak points in Performance Assessment (PA) exercises regarding the alteration of Spent Nuclear Fuel (SNF) are the contribution of the so-called Instant Release Fraction (IRF) and the effect of High Burn-Up Structure (HBS). This manuscript focuses on the effect of HBS in matrix (long term) and instant release of a Pressurised Water Reactor (PWR) SNF irradiated in a commercial reactor with a mean Burn-Up (BU) of 60 GWd/tU. In order to study the HBS contribution, two samples from different radial positions have been prepared. One from the centre of the SNF, labelled CORE, and one from the periphery, enriched with HBS and labelled OUT. Static leaching experiments have been carried out with two synthetic leaching solutions: bicarbonate (BIC) and Bentonitic Granitic Groundwater (BGW), and in all cases under oxidising conditions. IRF values have been calculated from the determined Fraction of Inventory in Aqueous Phase (FIAP). In all studied cases, some radionuclides (RN): Rb, Sr and Cs, have shown higher release rates than uranium, especially at the beginning of the experiment, and have been considered as IRF. Redox sensitive RN like Mo and Tc have been found to dissolve slightly faster than uranium and further studies might be needed to confirm if they can also be considered part of the IRF. Most of the remaining studied RN, mainly actinides and lanthanides, have been found to dissolve congruently with the uranium matrix. Finally, Zr, Ru and Rh presented lower release rates than the matrix. Higher matrix release has been determined for CORE than for OUT samples showing that the formation of HBS might have a protective effect against the oxidative corrosion of the SNF. On the contrary, no significant differences have been observed between the two studied leaching solutions (BIC and BGW). Two different IRF contributions have been determined. One corresponding to the fraction of inventory segregated in the external open grain boundaries, directly available to water and very significant during the first days of the experiment; and a second one corresponding to a less accessible, most probably located at the internal grain boundaries, one order of magnitude lower than the first one at equal given dissolution times but of much longer period of incidence. Unlike matrix release results, higher Cs IRF release was found for OUT than for CORE sample. This effect can be attributed to thermal migration of Cs to the periphery of the fuel during irradiation. In the case of Rb no clear differences were observed between CORE and OUT showing equilibrium between the opposing thermal migration and matrix effects. Finally, Sr CORE/OUT release ratio showed similar behaviour to matrix release, thus proving no significant thermal migration during irradiation. © 2012 Elsevier B.V. All rights reserved. Source

Discover hidden collaborations