The apparition of a new reaction at lower temperature in equiatomic CuAu alloy

Recently a lot of interest has been devoted to the study of order–disorder transitions in different materials. Although the equiatomic CuAu alloy represents a classical model of this type of transformation, it still receives considerable attention because many questions about phase transitions are still raised according to its equilibrium diagram. In this context, the present paper carries a new result observed in CuAu alloy consisting of a new anomaly observed on differential scanning calorimetry (DSC) curves at low temperature and new peaks in X-ray diffraction (XRD) spectra. For that, we will try to give an explanation of the origin of this new reaction, with the help of other techniques as electrical resistivity and microhardness measurements. The kinetic behaviour of this new reaction has been also studied by anisothermal analysis during DSC tests to estimate the kinetics parameters as activation energy E _act and Avrami exponent n.     

Realization and characterization of flexible supercapacitors based on doped graphene electrodes

Journal of Solid State Electrochemistry - High energy consumption leads to the development of various energy types. As a result, the storage of these different types of energy becomes a key issue....     

Finding a strict feasible solution of a linear semidefinite program

This study deals with the performance of projective interior point methods for linear semidefinite program. We propose a modification in the initialization phases of the method in order to reduce the computation time.This purpose is confirmed by numerical experiments showing the efficiency which are presented in the last section of the paper.     

Molecular hydrogen-induced nucleation of hydrogenated silicon nanocrystals at low temperature

Highly crystallized hydrogenated silicon layers were obtained via the treatment of hydrogenated polymorphous silicon films in a molecular hydrogen ambient. This contrasts other postdeposition studies that obtained nanocrystalline silicon films but necessitated either a plasma activation or high-temperature annealing. The structure of the samples was analyzed by Raman spectroscopy to determine the crystallite volume fraction, which was found to increase up to 80% within 1 hour of treatment. Atomic force microscopy (AFM) showed that the roughness of the surfaces was found to increase after the H₂ treatment. Optical transmission and spectroscopic ellipsometry revealed the pronounced porosity of the films characterized by a static refractive index that is below three, which is a low value for hydrogenated silicon films and a void fraction that is around 15% in the bulk of the films. The effect of the hydrogen molecules on the structure of the films was discussed in terms of the compressive stress exerted by the molecules, trapped in structural inhomogeneities, on the amorphous tissue. It is suggested that for this process to take effect, the films need to be porous and that the amorphous network needs to be in a “relaxed” state.     

Determination of the porosities of monolithic columns by inverse size-exclusion chromatography

Retention data of polystyrene samples of narrow molecular size distribution and known average molecular mass were measured on several monolithic columns (Chromolith Performance, Merck) and one conventional packed column (Luna C18, Phenomenex) by size-exclusion chromatography. These data were used to determine the external, the internal, and the total porosities of these columns. These data provided also information on the pore-size distribution of the adsorbent medium. The external and the total porosities of these columns are much higher than those of conventional packed columns. The results illustrate the profound changes brought by monolithic columns to the balance of the hydrodynamic and the mass transfer kinetic properties of chromatographic columns. Classical methods of comparison between column performance must be re-evaluated.     

Black-Hole Entropy as Causal Links

We model a black hole spacetime as a causal set and count, with a certain definition, the number of causal links crossing the horizon in proximity to a spacelike or null hypersurface . We find that this number is proportional to the horizon's area on , thus supporting the interpretation of the links as the horizon atoms that account for its entropy. The cases studied include not only equilibrium black holes but ones far from equilibrium.     

Surface behavior during abrasive grain action in the glass lapping process

In this study the surface behavior during its contact with the abrasive grain in the glass lapping process was studied using practical simulation which is the scratch test and the real contact between glass surfaces and α-alumina abrasive grains during lapping process. Formations and dimensions of the produced scratches were investigated to explain the grain action on the surface and the glass material removal rate. It has been found that humid environment created by the use of the slurry of loose abrasives causes more significant damages than the dry one. The use of slurry produces higher glass material removal rate in this environment and proves its utility in the lapping process. The shape of abrasive grains influences the nature of their action. Indeed, the worn grains produce scratches and chippings less than the sharp grains. During lapping, the number of scratches and theirs dimensions depend on the contact time and the abrasive grain size. It was concluded that the glass material removal rate during lapping depends on the cumulative actions of individual grains which produce scratches and chippings.     

A new efficient short-step projective interior point method for linear programming

In this paper, we are interested in the performance of Karmarkar’s projective algorithm for linear programming. We propose a new displacement step to accelerate and improve the convergence of this algorithm. This purpose is confirmed by numerical experimentations showing the efficiency and the robustness of the obtained algorithm over Schrijver’s one for small problem dimensions.