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[en] Distribution of a local field B(x) on the surface of Bi2Sr2CaCu2O8+d single crystal and its time dependence are measured using a micro Hall-probe array with 7 elements. From these data, the activation energy dependence on B(x) and on the current density J are estimated. The three-dimensional mapping of in B, J and U space gives us information on spatial behavior of in the sample.
SummaryA test fixture has been designed that allows the measurement of steady-state and transient temperature profiles in composites or other types of anisotropic or orthotropic materials under pure conduction in a vacuum. The uniqueness of this approach is the ability to study heat source to composite interface techniques by comparison of surface temperature contours and temperature versus time profiles. Localized changes in these conditions can be evaluated and the most successful technique can be adapted to larger parts, i.e., printed wiring boards (PWBs), electronic enclosure thermal walls, etc.
[en] As shown by this study, subsidies and advantages awarded to nuclear and fossil energies are prevailing in the French energy sector, notably with respect to renewable energies and energy savings. This study indeed aimed at assessing direct and indirect budgetary supports to the different forms of energy in France in order to assess the role of the French State in subsidies, taxing and support to industries. It appears that the support to renewable energies represents only between one and four per cent of that to nuclear energy. The study also notices that pollutions and consequences of accidents are not taken into account, that supports to renewable energies are badly managed, and that the evolution is very slow. After a definition of subsidies and supports, the report addresses different aspects related to renewable energies (R and D, ADEME's intervention, financing support for electrification projects, taxing, tax exemption for biofuels), to electro-nuclear energy (direct and indirect subsidies), to natural gas (R and D, investments of collectivities in gas networks, commercial supports), to coal (subsidies for research, for production and for reconversion, purchases order between EDF and Charbonnages de France, external costs paid by the community), to oil (direct subsidies, indirect subsidies in transports), to actions for the management of energy demand, and to electric power (direct subsidies, power in overseas districts and in Corsica)
[en] We have studied possible ground-state phases of Pd(dmit)2 salts using the two-band Hubbard model. From a strong coupling expansion, an effective model is derived and used to describe low-energy excitations. It is found that mutual interactions and dimensionality of effective bands cooperatively determine the transport and magnetic properties.
[en] We have studied the Fermi surface properties in strongly anisotropic or quasi-two-dimensional systems of CePtX (X=As, P) and UX2 (X=Sb, As). Not only the band folding but also the strong hybridization effect play an important role in the quasi-two-dimensionality for these compounds.
[en] The gamma displacement cross-sections for energies up to 14 MeV have been calculated in various materials at two values of displacement threshold energy (24 and 40 eV). Three types of gamma ray interactions with materials are considered, the photoelectric effect, Compton scattering and pair production. Depending on the atomic number (Z) of target materials and energy of incident gamma rays, the relative contribution of three interactions to total displacements changes. It is found that for medium and low-Z material Compton scattering is predominant over most of the energy range, while pair production becomes important for high-Z material at high gamma energy.
[en] The aim of this study is to understand the effect of rotation on the spatial transport of turbulent kinetic energy in inhomogeneous turbulent flows. The configuration retained is a shearless turbulent mixing layer where transport effects are preponderant. This mixing layer is formed in two decaying grid turbulences put side by side, having different intensities and length scales, and interacting. The transport terms which appears in the equation of the Reynolds stress equation are the gradient of triple velocity correlations and the gradient of the pressure velocity correlation. Experimentally, this kind of flow was studied without rotation by Veeravalli and Warhaft (1989). The specificity of this present work compare with the Veeravalli and Warhaft's experiment is to include the effects of rotation with the help of the experimental study of Jacquin (1987). In the non rotating case, we obtain a peak of the triple velocity correlation profile, which is characteristic of the turbulent transport across the mixing layer. It can also be pointed out that the transverse velocity fluctuations have a large kurtosis associated with the existence of strong intermittency effects near the edge of the mixing layer. Without rotation, we obtain the same results in agreement with those of Veeravalli et Warhaft. A Large Eddy Simulations of the mixing layer (Shao, Michard and Bertoglio (1991)) shows that the pressure-velocity correlation plays a negligible role in this case. When rotation is present, the triple moment is found to be reduced which is characteristic of the reduction of the turbulent transport by this term. It can be noticed that the intermittency of the mixing layer is also reduced when rotation is present. To model the triple correlation, we used the Hanjalic and Launder's (1972) model. A modification of this model with a constant function of the rotation rate, permits to take into account the reduction of the turbulent kinetic energy transport by these moments. In the L.E.S., it was found that, at high rotation rates, turbulence transport is no longer associated with triple moments, but still remains efficient, being due to the pressure velocity fluctuation whose effect is strongly promoted by rotation effects (see also Le Penven, Bertoglio and Shao (1993)). Since the experimental results do not show significant influence of rotation on the profiles of turbulent kinetic energy, whereas the triple correlations are found to be strongly affected, the present work seems to support the conclusion of the LES study, and it can reasonably be inferred that pressure velocity-correlation must play a significant role at high rotation rate.
[fr]Le but de cette etude est de comprendre les effets de la rotation sur le transport spatial de l'energie cinetique dans les ecoulements turbulents inhomogenes. La configuration retenue est celle d'une couche de melange turbulente non cisaillee. Cette couche de melange est constituee de deux turbulences de grille, mises cote a cote, ayant des energies et des echelles de longueur differentes et qui interagissent Les termes de transport qui apparaissent dans les equations d'evolution du tenseur de Reynolds sont les gradients des correlations triples de vitesse et les gradients des correlations pression-vitesse. Experimentalement, ce type d'ecoulement a ete etudie sans rotation par Veeravalli et Warhaft (1989). La specificite de la presente etude par rapport a l'etude de Veeravalli et Warhaft est d'inclure les effets de rotation en s'inspirant de l'etude experimentale de Jacquin (1987). En l'absence de rotation, nous observons un pic sur les profils des moments d'ordre trois dans la couche de melange. ce qui traduit l'importance du transport par les correlations triples de vitesse dans cette zone. Il apparait egalement que cette zone de melange est fortement intermittente, ce qui se traduit par un ecart a la gaussianite des profils des moments d'ordre quatre. Ces resultats sont en accord avec ceux obtenus par Veeravalli et Warhaft. Une etude numerique par simulation des grandes echelles (Shao, Michard et Bertoglio (1991)) a montre que les correlations pression-vitesse jouent dans ce cas un role negligeable. En presence de rotation, nous observons une forte reduction du transport turbulent par les correlations triples de vitesse ainsi qu'une reduction de l'intermittence de la zone de melange. Pour modeliser ces moments d'ordre trois, nous avons utilise le modele de Hanjalic et Launder (1972). Une modification de ce modele, avec une constante fonction du taux de rotation, permet de rendre compte de la diminution du transport de l'energie cinetique turbulente par ces moments. Les simulations L.E.S. ont montre que dans le cas ou la rotation est presente, ce sont les correlations pression-vitesse qui assurent le transport de l'energie a travers la couche de melange. Comme nous n'observons pas d'effet sensible de la rotation sur les profils d'energie cinetique turbulente alors que les moments d'ordre trois sont fortement reduits, cette presente etude semble donc aller dans le sens de la conclusion des simulations numeriques, a savoir que ce sont les correlations pression-vitesse qui assurent le transport turbulent a travers la couche de melange (voir Le Penven, Bertoglio et Shao (1993)).
[en] This paper is to do a rethinking of nuclear criticality safety management in China, focusing on the safety performance achieved in nuclear fuel cycle in the country over the last 40 years, pointing out the key aspects and the central problems that would result in nuclear criticality accident. A wide range of countermeasures to further strengthen nuclear criticality safety management is suggested. (authors)
[en] The γ-ray mass attenuation coefficients of sample matrixes of marine organisms were calculated. The results have shown that there are difference among various sample matrixes of marine organisms, especially in the energy range of 10∼100 keV. (authors)
[en] A coupled-channel formalism is presented which allows to calculate, simultaneously, cross sections corresponding to elastic, inelastic, transfer of two neutrons and fusion. The nuclear excitations are considered as rotations in the real space and the two-neutron transfer as a rotation in a gauge space. The target as well as the projectile are considered to have zero spin. For different reaction channels the formalism permits to obtain wave functions angular distributions of differential cross sections, total cross sections, excitation functions and spin distributions. (authors)