Filters
Results 1 - 10 of 831
Results 1 - 10 of 831.
Search took: 0.036 seconds
| Sort by: date | relevance |
[en] A small break in a horizontal coolant pipe is investigated. This flow geometry and accident scenario are of interest in nuclear reactor safety research. For the calculation of break mass flow rate, appropriate experiments are needed, especially for the case where stratified two-phase flow exists in the main pipe. The flow geometry corresponds to a ''T''-junction with a large-diameter ratio of the horizontal pipe, D, to the branch pipe, d. In the present experiments, D was 206 mm, the downward-oriented branch diameters were 6, 12, and 30 mm. Air/water experiments were performed at a system pressure of 0.5 MPa and various differential pressures. The flow field could be observed visually. Photographs reveal both vortex-induced and vortex-free gas pull-through the break and the corresponding correlations for the onset of gas pull-through. The mass flow rate and quality distribution as a function of a dimensionless interface level are presented
Journal
Nuclear Science and Engineering; ISSN 0029-5639; 
; v. 88(3); p. 297-310
; v. 88(3); p. 297-310
[en] Nowadays researchers are developing a new hybrid fiber reinforced cement-based composites (HyFRCC). The new HyFRCC can restrain micro-cracking, improves compressive and flexural performance of beams by addition of calcium carbonate (CaCO3) whisker, polyvinyl alcohol (PVA) fiber and steel fiber. In this work, a mix optimization procedure is shown for multi-scale HyFRCC, with steel, PVA fiber and CaCO3 whisker. The new HyFRCC is explored with addition of coarse sand to further improve its mechanical properties. Additionally, the flexural performance of beam and slabs has been investigated to optimize sand gradation and fiber combination in new HyFRCC. The compressive strength, flexural strength, flexural behavior, flexural toughness, equivalent flexural strength and deflection-hardening behavior of beams and slabs are improved with optimized content of sand gradation, fibers and CaCO3 whisker. The HyFRCC slab with 1.5% steel fiber, 0.4% PVA fiber, 1% CaCO3 whisker and optimized coarse sand showed overall best properties.
[es]
En la actualidad se están desarrollando nuevos cementos compuestos reforzados con fibras híbridas (HyFRCC, por sus siglas en inglés). Estos nuevos cementos HyFRCC pueden impedir la microfisuración y aumentar la resistencia a compresión y flexotracción de las vigas, mediante la incorporación de filamentos de carbonato cálcico (CaCO3), fibras de alcohol polivinílico (PVA) y fibras de acero. En estetrabajo se plantea un procedimiento para optimizar la proporción de fibras (de acero y de PVA) y filamentos (de CaCO3) en un nuevo HyFRCC. Se investiga la influencia de la arena gruesa en sus propiedades mecánicas, además de la resistencia a flexotracción de vigas y forjados a fin de adecuar la granulometría de la arena y la combinación de fibras en el nuevo material. Un buen ajuste entre el contenido y la granulometría de la arena y la proporción de las fibras y de los filamentos de CaCO3 permite: incrementar la resistencia tanto a compresión como a flexotracción, la tenacidad a flexotracción y la resistencia a flexotracción equivalente; perfeccionar el comportamiento a flexión; y reducir la flecha de vigas y forjados endurecidos. La mezcla que mejores resultados arroja en conjunto contiene 1,5 % de fibras de acero, 0,4 % de fibras de PVA, 1 % de filamentos de CaCO3 y arena gruesa optimizadaJournal
Materiales de Construccion; ISSN 0465-2746; ; v. 68(330); 13 p
; v. 68(330); 13 p
[en] Purpose: The purpose of this study is to investigate the dose-volume variations of planning target volume (PTV) and organs-at-risk (OARs) in prostate volumetric modulated arc therapy (VMAT) when using different collimator angles. It is because collimator angle awareness is essential for planner to produce an optimal prostate VMAT plan in a rational time. Methods: Single-arc VMAT plans at different collimator angles (0o, 15o, 30o, 45o, 60o, 75o and 90o) were created systematically using a Harold heterogeneous pelvis phantom. For each change of collimator angle, a new plan was re-optimized for that angle. The prescription dose was 78 Gy per 39 fractions. Conformity index (CI), homogeneity index (HI), gradient index, machine monitor unit, dose-volume histogram, the mean and maximum doses of the PTV were calculated and analyzed. On the other hand, dose-volume histogram, the mean and maximum doses of the OARs such as bladder, rectum and femoral heads for different collimator angles were determined from the plans. Results: There was no significance difference, based on the plan dose-volume evaluation criteria, found in the VMAT optimizations for all studied collimator angles. Higher CI and lower HI were found for the 45o collimator angle. In addition, the 15o collimator angle provided lower HI similar to the 45o collimator angle. The 75o and 90o collimator angle were found good for the rectum sparing, and the 75o and 30o collimator angle were found good for the right and left femur sparing, respectively. The PTV dose coverage for each plan was comparatively independent of the collimator angle. Conclusion: The dosimetric results in this study are useful to the planner to select different collimator angles to improve the PTV coverage and OAR sparing in prostate VMAT
Journal
[en] Heavy metals, due to its effect on microbial diversity, soil fertility and the yields of various crops have attracted greater attention worldwide. Conventional methods for removing/detoxifying metals from polluted sites generate huge quantities of toxic products and are not economical. The use of microbial communities for remediation of heavy metals, from contaminated sites has provided an alternative to conventional techniques. (Author)
Source
350 p; ISBN 978-84-692-4948-2; ; 2009; p. 247; Graficas Terrasa; Islas Baleares (Spain); 3. International Meeting on Environmental Biotechnology and Engineering; Palma de Mallorca (Spain); 21-25 Sep 2008
; 2009; p. 247; Graficas Terrasa; Islas Baleares (Spain); 3. International Meeting on Environmental Biotechnology and Engineering; Palma de Mallorca (Spain); 21-25 Sep 2008
| 1 | 2 | 3 | Next |