On the equivalence of the invariant subdistribution algorithm and the structure algorithm

The invariant subdistribution algorithm is shown to be equivalent to the Structure Algorithm for the computation of the formal ‘structure at infinity' of a nonlinear system which satisfies an assumption introduced earlier by the author. In addition, the above assumption is proved to be weaker than Hirschorn's condition.     

In situ thermal residual stress evolution in ultrathin ZnO and Ag films studied by synchrotron x-ray diffraction

Residual-stress evolution in sputtered encapsulated ZnO/Ag/ZnO stack has been studied in-situ by synchrotron x-ray diffraction when heat treated. The ZnO/Ag/ZnO stack encapsulated into Si₃N₄ layers and deposited on (001) Si substrates was thermally heated from 25 °C to 600 °C and cooled down to 25 °C. X-ray diffraction 2D patterns captured continuously during the heat treatment allowed monitoring the diffraction peak shifts of both Ag (15 nm thick) and ZnO (10 nm and 50 nm thick) sublayers. Due to the mismatch between the coefficients of thermal expansion, the silicon substrate induced compressive thermal stresses in the films during heating. We first observed a linear increase of the compressive stress state in both Ag and ZnO films and then a more complex elastic-stress evolution starts to operate from about 100 °C for Ag and about 250 °C for ZnO. Thermal contraction upon cooling seems to dominate so that the initial compressive film stresses relax by about 300 and 700 MPa after thermal treatment for ZnO and Ag, respectively. The overall behavior is discussed in terms of structural changes induced by the heat treatment.     

Effects of various loading stress paths on the stress-strain properties and on crushability of an industrial soft granular material

Mechanical characteristics (i.e., stiffness, internal friction angle, peak strength) and crushability of a soft granular material were evaluated by performing a comprehensive series of laboratory tests using the following devices: standard and non-standard triaxial apparatus, direct and annular shear box, oedometer and hydrostatic devices. The initial tested specimens differ by initial void ratio, grading characteristics and particle hardness. The air-dried specimen of soft particles were then subjected to monotonic loadings for various stress paths (direct and annular shear stress paths, oedometer stress paths until different upper normal pressures, triaxial stress paths including different confining pressures). After each homogeneous test, sieving has been performed in order to characterize the evolution of grading characteristics of the granular packing. Experimental results on mechanical properties show that maximum internal friction angle is rather independent of the particle stiffness even though small differences may exist before peak stress-state. As highlighted by recent studies (Arslan in Granul Matter 11(2): 87–97, 2009), the volumetric response of the specimen indicates that classical critical state is no more a relevant framework when particle crushability is too high compared with the applied stress-state. Crushability related to loading paths has been evaluated through the relative breakage ratio (B_r). The first results pointed out the effects of initial geometrical configuration (i.e., void ratio, grading) and particle stiffness. Analysis of the stress paths effects on the amount of breakage revealed that stress-state is not sufficient to describe properly breakage undergone by the material which is confirmed by an obvious link between volumetric strain and total breakage. Finally, the present study showed that the percentage of fine particles content during breakage may be seen as a function of the “level” of deviatoric loading paths.     

A multidimensional approach to academic productivity

This study represents one of the first attempts to use empirical analysis to estimate academic productivity complex and proves the thesis that academic productivity is a function of multidimensional combination of the work of academic researchers: the scientific work, education, and external relationships. Given the complexity of academic productivity, it is necessary to clarify that it is divided into scientific productivity of the first type (scientific publications); scientific productivity of the second type (awards and academic positions); productivity in terms of external relationships (or external advice); and educational productivity. This objective of this paper is achieved through a sample survey (2,738 academics responded) conducted by Italian researchers from the PIR research project. The results obtained, however (as a case of estimates obtained using the results of a sample survey), are the result of a working reality that Italian academics are flooded by a myriad of activities that are not always consistent with the primary aims of the work of a researcher with an organisational and environmental well-being at the limit of iper productivity (or hyper productivity). The overall productivity (academic productivity) is significantly correlated with the four dimensions: average annual scientific productivity of the first type, average annual scientific productivity of the second type, the productivity external advice and, lastly, teaching productivity. The estimate of the sizes for the four indicators of productivity are the result of a literature search of the primary techniques used to assess productivity in academia. By comparing the most significant indicators, we managed to select all of the technical aspects missing in the Italian system of evaluation. This process allowed for us to add additional variables characterising the various aspects of productivity and prove the validity of our theory about the multidimensionality of academic productivity.     

Effect of the Re number on heat and mass transport in a catalytic monolith

The numerical investigation of inter-phase heat transfer in a catalytic combustor, under laminar flow regime at different values of the Re number, is performed by means of a 2D axi-symmetric model of a single monolith channel. Numerical results highlight that axial diffusion comes to play an important role in the ignition region also at high convective fluxes (high Re) due to the strong flow perturbation accompanying light-off, with the consequences that: (a) the ignition position is not a linear function of contact time, as it would be expected at high Re; (b) the heat and mass transfer between surface and bulk gas phase are non-linearly affected by Re, especially in the entrance and in the ignition regions.A previously developed correlation for Nu and Sh is, hence, extended to include the effect of the Re number on heat and mass fluxes, enabling the prediction of the local value of Nu and Sh in the main features, and in particular the enhancement in the ignition region and the dependence on Re.