Search for emission of unstable 8^8Be clusters from hot 40^40Ca and 56^56Ni nuclei

The possible occurence of highly deformed configurations is investigated in the $^{40}$Ca and $^{56}$Ni di-nuclear systems as formed in the $^{28}$Si + $^{12}$C and $^{28}$Si + $^{28}$Si reactions, respectively, by using the properties of emitted light charged particles. Inclusive as well as exclusive data of the heavy fragments (A $\geq$ 6) and their associated light charged particles (p, d, t, and $\alpha$-particles) have been collected at the IReS Strasbourg VIVITRON Tandem facility with two bombarding energies $E_{lab}(^{28}$Si) = 112 and 180 MeV by using the ICARE charged particle multidetector array, which consists of nearly 40 telescopes. The measured energy spectra, velocity distributions, in-plane and out-of-plane angular correlations are analysed by Monte Carlo CASCADE statistical-model calculations using a consistent set of parameters with spin-dependent level densities. Although significant deformation effects at high spin are needed, the remaining disagreement observed in the $^{28}$Si + $^{12}$C reaction for the S evaporation residue suggests an unexpected large unstable $^{8}$Be cluster emission of a binary nature.Comment: 13 pages latex, 9 eps figures. Paper presented at the XXXIX International Winter Meeting on Nuclear Physics, Bormio(Italy) January 22-27, 2001 (to be published at Ricerca Scientifica ed Educazione Permanente

Microstructural and mechanical characteristics of EUROFER'97 processed by equal channel angular pressing

Proceedings of : 14th International Conference on Fusion Reactor Materials (ICFRM-14), 6-11 september, 2009. Sapporo Convention Center Sapporo, Japan.EUROFER'97 was processed by equal channel angular pressing (ECAP) at 823 K for a total of 4 or 8 passes, using a die angle of 105°, and its microstructure and tensile behavior in temperature range 568 873 K investigated. A single ECAP pass developed a deformation texture {1 1 0} 〈0 1 1〉 that was practically stable during subsequent ECAP passes. The materials processed by 1 or 2 passes exhibited a fine microstructure of recovered subgrains and tensile behavior very similar to that for the tempered material in the as-received condition. The materials processed using 4 or 8 passes exhibited nearly equiaxial submicron grained structures with a high density of high-angle grain boundaries. These materials became softer than the as-received material at a testing temperature of ~8764;823 K. EUROFER ECAP processed under the present conditions exhibited hardening ratio somewhat higher than that of the as-received material.This investigation was supported by the EURATOM/CIEMAT association through Contract 09 240, by the Comunidad de Madrid (program ESTRUMAT CM S0505/MAT/0077) and by Spanish Ministry of Science and Innovation Contract ENE 2008 06403 C06 04.Publicad

Large Deformation Effects in the N = Z 44Ti Compound Nucleus

The N = Z 44Ti* nucleus has been populated in Fusion Evaporation process at very high excitation energies and angular momenta using two entrance channels with different mass-asymmetry. The deformation effects in the rapidly rotating nuclei have been investigated through the energy distribution of the alpha-particle combined to statistical-model calculations. In the case of low-multiplicity events, the ratio between first particle emitted has been measured and shows significant disagreement with the predictions of the statistical-model. This may explain The large discrepancies observed in proton energy spectra measured in previous experiments performed in the same mass region.Comment: Proceeding of the 10th International Conference on Nuclear Reaction Mechanisms, Varenna Italy, June 9-13 2003. 10 pages, 6 figures, 1 tabl

On the monotone stability approach to BSDEs with jumps: Extensions, concrete criteria and examples

We show a concise extension of the monotone stability approach to backward stochastic differential equations (BSDEs) that are jointly driven by a Brownian motion and a random measure for jumps, which could be of infinite activity with a non-deterministic and time inhomogeneous compensator. The BSDE generator function can be non convex and needs not to satisfy global Lipschitz conditions in the jump integrand. We contribute concrete criteria, that are easy to verify, for results on existence and uniqueness of bounded solutions to BSDEs with jumps, and on comparison and a-priori $L^{\infty}$-bounds. Several examples and counter examples are discussed to shed light on the scope and applicability of different assumptions, and we provide an overview of major applications in finance and optimal control.Comment: 28 pages. Added DOI https://link.springer.com/chapter/10.1007%2F978-3-030-22285-7_1 for final publication, corrected typo (missing gamma) in example 4.1

Deformation effects in the 28^{28}Si+12^{12}C and 28^{28}Si+28^{28}Si reaction Search

The possible occurence of highly deformed configurations is investigated in the $^{40}$Ca and $^{56}$Ni di-nuclear systems as formed in the $^{28}$Si+$^{12}$C,$^{28}$Si reactions by using the properties of emitted light charged particles. Inclusive as well as exclusive data of the heavy fragments and their associated light charged particles have been collected by using the {\sc ICARE} charged particle multidetector array. The data are analysed by Monte Carlo CASCADE statistical-model calculations using a consistent set of parameters with spin-dependent level densities. Significant deformation effects at high spin are observed as well as an unexpected large $^{8}$Be cluster emission of a binary nature.Comment: 3 pages latex, 2 eps figures, paper presented in "wokshop on physics with multidetector array (pmda2000)Calcutta, India (to be published at PRAMANA, journal of Physics, India

Highly deformed 40^{40}Ca configurations in 28^{28}Si + 12^{12}C

The possible occurrence of highly deformed configurations in the $^{40}$Ca di-nuclear system formed in the $^{28}$Si + $^{12}$C reaction is investigated by analyzing the spectra of emitted light charged particles. Both inclusive and exclusive measurements of the heavy fragments (A $\geq$ 10) and their associated light charged particles (protons and $\alpha$ particles) have been made at the IReS Strasbourg {\sc VIVITRON} Tandem facility at bombarding energies of $E_{lab} (^{28}$Si) = 112 MeV and 180 MeV by using the {\sc ICARE} charged particle multidetector array. The energy spectra, velocity distributions, and both in-plane and out-of-plane angular correlations of light charged particles are compared to statistical-model calculations using a consistent set of parameters with spin-dependent level densities. The analysis suggests the onset of large nuclear deformation in $^{40}$Ca at high spin.Comment: 33 pages, 11 figure

Texture evolution during deformation of an AI-6 % Cu-0,4 % Zf superplastic alloy

7 páginas, 6 figuras.[ES] Se ha estudiado la evolución de la microestructura y textura de una aleación superplástica de Al-6%Cu-0,4 %Zr a 480 °C/5.10-4s-1. La microestructura en estado de recepción consta de una subestructura fina. Presenta gradientes de textura a través del espesor de la chapa. En la superficie la textura esta compuesta, principalmente, por la orientación {311} (Cu) mientras que en el centro por la orientación {631} (S). La curva de tracción (σ)-(ε) presenta tres estados de deformación, llamados estado I, II y III. En el estado I la textura inicial aumenta ligeramente. En el estado II la intensidad de la orientación {311} disminuye, lo que sugiere la operación del deslizamiento de las fronteras de grano. Sin embargo, en el centro se estima que la componente {631} evoluciona a lo largo de la fibra β induciendo la formación de orientaciones en tomo a las componentes {110} (Β) y/o {110} (Ρ) por un proceso de deslizamiento de dislocaciones. En el estado III de deformación la textura global disminuye.[EN] Evolution of the grain structure and microstructure was studied at 480 °C/5-10 -4 s-1 on an A1-6 % Cu-0,4 % Zr superplastic alloy. The as-received material showed a fine deformed substructure. A texture gradient was present through the thickness of the rolled sheet. At the surface, the texture found was close to the orientation {311} whereas in the midplane of the sheet it was {631}. The {omega)-(£) tensile test curve presented three deformation stages called, stage I, II and III. The global texture in stage I increased slightly. In stage II, the intensity of the orientation {311} decreased, suggesting that a grain boundary sliding process should take place near the surface. However, in the center of the sheet it is approached that the {63I} component changes along the p-fiber inducing a clustering around the {110} (B) and//or {110} orientations by slip process. In the stage III the intensity of orientations decreases.Los autores agradecen a la Comunidad Autónoma de Madrid 345/200 la concesión de la beca postdoctoral. También, agradecen la Comisión Interministerial de Ciencia y Tecnología (CICYT) la subvención del proyecto MAT2000-1313Peer reviewe

Comportamiento superplástico de una aleación AZ61 procesada por extrusión en canal angular

This study is concerned with microstructural and mechanical characterization of the superplastic behaviour of a magnesium base AZ61 alloy processed by equal channel angular extrusion (ECA). Microscopic examinations showed that the microstructure after ECA was homogeneous and the grain size was about 5 mm. The extruded material showed better mechanical properties than the rolled material. The strain rate sensitivity exponent, at 250ºC, was 0.5 at strain rates ranging from 10-4 to 5 . 10-4 s-1. Under these conditions, the maximum elongation obtained was 250% and the microstructure remained homogeneous and stable. Furthermore, the stress strain curves showed strong strain hardening which was not attributed exclusively to dynamic grain growth.En este trabajo se estudia el comportamiento superplástico, tanto mecánico como microestructural, de una aleación de base magnesio AZ61 procesada por extrusión en canal angular (ECA). Las observaciones microscópicas revelaron que la microestructura después de ECA es muy homogénea y el tamaño de grano es de aproximadamente 5 mm. El material extruido, comparado con el material laminado, muestra buenas propiedades mecánicas. El exponente de la sensibilidad a la velocidad de deformación, a 250ºC, es próximo a 0,5 en el intervalo de velocidades entre 10-4 y 5.10-4 s-1 y el máximo alargamiento obtenido es de 250%. La microestructura permanece muy homogénea y estable durante la deformación superplástica. Además, las curvas de tensión deformación muestran un importante endurecimiento que, en este caso, no se puede atribuir únicamente al crecimiento dinámico de grano.M. Eddahbi agradece a la Comunidad Autónoma de Madrid por la beca Postdoctoral Ref. 345/2000. Asimismo, los autores agradecen a la CICYT por el proyecto MAT2003-5108.Peer reviewe