The investigation of model selection criteria in artificial neural networks by the Taguchi method

Artificial neural networks (ANNs) have been successfully used for solving variety of problems. One major disadvantage of ANNs is that there is no formal systematic model building approach. This paper presents the application of the Taguchi method in the optimization of the design parameters of the ANNs. The performances of the ANNs were determined by the Taguchi method considering factors relevant for ANNs’ performance. The properties affecting the performance of the ANNs and their levels on the peak analytical function were determined by performing computational experiments. After training the network, the values of the statistical data criteria were determined and the optimum parameter levels were obtained in terms of the performance statistics. The performance of ANNs is shown to be better in the case of the application of the Taguchi method rather than in the case of random choice of factor values.     

Flow characterization of diffusion flame oscillations using particle image velocimetry

Particle image velocimetry (PIV) was used to measure velocity fields inside and around oscillating methane-air diffusion flames with a slot fuel orifice. PIV provided velocity and directional information of the flow field comprised of both the flame and air. From this, information on flow paths of entrained air into the flame were obtained and visualized. These show that at low fuel flow rates for which the oscillations were strongest, the responsible mechanism for the oscillating flow appeared to be the repetitive occurrence of flame quenching. PIV findings indicated that quenching appears to be associated primarily with air entrainment. Velocity was found to be considerably larger in regions where quenching occurred. The shedding of vortices in the shear layer occurs immediately outside the boundary of the flame envelope and was speculated to be the primary driving force for air entrainment.     

Cation assisted binding and cleavage of dinitrogen by uranium complexes

The role of alkali promoters in N₂ cleavage by metal complexes remains poorly understood despite its relevance to the industrial production of ammonia from N₂. Here we report a series of alkali bound-oxo-bridged diuranium(iii) complexes that provide a unique example of decreasing N₂ binding affinity with increasing cation size (from K to Cs). N₂ binding was found to be irreversible in the presence of K. A N₂ complex could be isolated in the solid state in the presence of the Rb cation and crystallographically characterized, but N₂ binding was found to be reversible under vacuum. In the presence of the Cs cation N₂ binding could not be detected at 1 atm. Electrochemical and Computational studies suggest that the decrease in N₂ binding affinity is due to steric rather than electronic effects. We also find that weak N₂ binding in ambient conditions does not prevent alkali assisted N₂ cleavage to nitride from occurring. More importantly, we present the first example of cesium assisted N₂ cleavage leading to the isolation of a N₂ derived multimetallic U/Cs bis-nitride. The nitrides readily react with protons and CO to yield ammonia, cyanate and cyanide.

N₂ binding affinity decreases markedly in a series of isostructural U(iii)–alkali ions complexes with increasing cation size. N₂ binding is undetectable in the Cs analogue, but the first example of cesium-assisted N₂ cleavage to bis-nitride was observed at ambient condition.     

Groups with some restrictions on non-Baer subgroups

Ricerche di Matematica - It is proved that if G is an $$\mathfrak {X}$$ -group of infinite rank whose proper subgroups of infinite rank are Baer groups, then so are all proper subgroups of G, where...     

Experimental mixing parameterization due to multiphase fluid–structure interactions

Experimental estimates of the rate at which energy is extracted from the barotropic tide at corrugated sloping topography are presented. To this end, a series of experimental simulations of the process of generation of internal tides (i.e., internal waves of the tidal frequency) over a corrugated slope in stratified fluid were performed. An oceanic interior is modeled as four-layer stratified fluid. The main focus in these studies was to obtain the relation for the potential energy available for mixing as a function of a slope of a corrugated slope. The available potential energy available for partial mixing to the topographic slope was compared with the available potential energy sufficient for complete mixing of the four layers. The experimental data were compared with the analytic results of a linear theory and found in agreement with a recent theoretically predicted scenario showing that the dominant contribution of the energy distribution in internal wave field resides in waves of the lowest allowed frequency.     

Phonons and related crystal properties in indium phosphide under pressure

Based on the pseudopotential approach, the lattice vibration and polaron properties in InP under pressure up to 8 GPa have been investigated. At zero pressure, our calculated values for all features of interest are in reasonable agreement with data available in literature. Upon compression, the optical phonon modes at Γ point in the Brillouin zone are shifted towards high energies and their frequencies display a blueshift with rising pressure. The splitting of the longitudinal and transverse optical phonons narrows under pressure, indicating thus a decrease of the ionicity of InP crystal with pressure. It is observed that all physical quantities being studied in this contribution behave monotonically upon compression. To the best of the author's knowledge, the pressure dependence of the polaron properties for InP in the present study is reported for the first time.     

Effective masses of electrons, heavy holes and positrons in quasi-binary (GaSb)1−x(InAs)x crystals

The present investigation is focused on the effective masses of electrons, heavy holes and positrons in quasi-binary (GaSb)_1−x(InAs)_x crystals. To the best of our knowledge, this is the first time such quantities have been obtained for such a quasi-binary crystals. Our computations are based on the pseudopotential scheme within the virtual crystal approximation in which the effects of composition disorder are involved, while the positron wave function is evaluated under the point core approximation for the ionic potential. Comparisons are made with the measured values, which are only available for binary parent compounds and showed roughly good agreement. The calculated quantities in the quasi-binary crystals of interest are found to be generally different from those of the conventional quaternary alloys GaInAsSb which may provide more diverse opportunities to describe most carrier transport properties.