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RISS 인기검색어
- 검색키워드
- 저자 : Pescador, E. Diaz (검색결과 4 건)
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Pescador, E. Diaz,Schafer, F.,Kliem, S. Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.10
The implementation and validation of multi-dimensional (multi-D) features in thermal-hydraulic system codes aims to extend the application of these codes towards multi-scale simulations. The main goal is the simulation of large-scale three-dimensional effects inside large volumes such as piping or vessel. This novel approach becomes especially relevant during the simulation of accidents with strongly asymmetric flow conditions entailing density gradients. Under such conditions, coolant mixing is a key phenomenon on the eventual variation of the coolant temperature and/or boron concentration at the core inlet and on the extent of a local re-criticality based on the reactivity feedback effects. This approach presents several advantages compared to CFD calculations, mainly concerning the model size and computational efforts. However, the range of applicability and accuracy of the newly implemented physical models at this point is still limited and needs to be further extended. This paper aims at contributing to the validation of the multi-D features of the system code ATHLET based on the simulation of the Tests 1.1 and 2.1, conducted at the test facility ROCOM. Overall, the multi-D features of ATHLET predict reasonably well the evolution from both experiments, despite an observed overprediction of coolant mixing at the vessel during both experiments.
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Diaz-Pescador E.,Schäfer F.,Kliem S. 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.9
This paper provides an assessment of fluid transport and mixing processes inside the primary circuit of the test facility ROCOM through the numerical simulation of Test 2.1 with the system code ATHLET. The experiment represents an asymmetric injection of cold and non-borated water into the reactor coolant system (RCS) of a pressurized water reactor (PWR) to restore core cooling, an emergency procedure which may subsequently trigger a core re-criticality. The injection takes place at low velocity under single-phase subcooled conditions and presents a major challenge for the simulation in lumped parameter codes, due to multidimensional effects in horizontal piping and vessel arising from density gradients and gravity forces. Aiming at further validating ATHLET 3-D capabilities against horizontal geometries, the experiment conditions are applied to a ROCOM model, which includes a newly developed horizontal pipe object to enhance code prediction inside coolant loops. The obtained results show code strong simulation capabilities to represent multidimensional flows. Enhanced prediction is observed at the vessel inlet compared to traditional 1-D approach, whereas mixing overprediction from the descending denser plume is observed at the upper-half downcomer region, which leads to eventual deviations at the core inlet.
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Juan C Pescador-Piedra,Reynold R Farrera-Rebollo,Georgina Calderón- Domínguez 한국식품과학회 2010 Food Science and Biotechnology Vol.19 No.6
Glucose oxidase (GOX) has been recognized as an alternative to substitute chemical oxidants in bread making, however the action exerted on wheat flour proteins by the H2O2 produced is still unclear. Looking for a better understanding of the role of GOX and H2O2 in the bread making process, the effect of varying GOX levels and mixing time on soluble and insoluble wheat flour protein fractions was studied. Results showed that GOX promoted a decrement in free SH groups in both proteins,being the most evident effect on the soluble fraction at the beginning of the mixing process, remaining almost constant afterwards. H2O2 was continuously produced during mixing,showing its largest consumption during the first 6 min without significant SH changes afterwards. Results suggest that H2O2 must be involved in other reactions as it remains in the sample; this also suggests that oxygen is not a limiting factor in this reaction.
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Angeles-Hernandez, J.C.,Albarran-Portillo, B.,Gomez Gonzalez, A.V.,Pescador Salas, N.,Gonzalez-Ronquillo, M. Asian Australasian Association of Animal Productio 2013 Animal Bioscience Vol.26 No.8
The objective of this study was to compare the goodness of fit of four lactation curve models: Wood's Gamma model (WD), Wilmink (WL), and Pollott's multiplicative two (POL2) and three parameters (POL3) and to determine the environmental factors affecting the complete lactation curve of F1 dairy sheep under organic management. A total of 5,382 weekly milk yields records from 150 ewes, under organic management were used. Residual mean square (RMS), determination coefficients ($R^2$), and correlation (r) analysis were used as an indicator of goodness of fit for each model. WL model best fitted the lactation curves as indicated by the lower RMS values (0.019), followed by WD (0.023), POL2 (0.025) and POL3 (0.029). The four models provided total milk yield (TMY) estimations that were highly correlated (0.93 to 0.97) with observed TMY (89.9 kg). The four models under estimated peak yield (PY), whereas POL2 and POL3 gave nearer peak time lactation estimations. Ewes lambing in autumn had higher TMY and showed a typical curve shape. Higher TMY were recorded in second and third lambing. Season of lambing, number of lambing and type of lambing had a great influenced over TMY shaping the complete lactation curve of F1 dairy sheep. In general terms WL model showed the best fit to the F1 dairy sheep lactation curve under organic management.
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