Analysis of plane and axisymmetric flows of incompressible fluids with the stream tube method: Numerical simulation by trust-region optimization algorithm

New concepts for the study of incompressible plane or axisymmetric flows are analysed by the stream tube method. Flows without eddies and pure vortex flows are considered in a transformed domain where the mapped streamlines are rectilinear or circular. The transformation between the physical domain and the computational domain is an unknown of the problem. In order to solve the non-linear set of relevant equations, we present a new algorithm based on a trust region technique which is effective for non-convex optimization problems. Experimental results show that the new algorithm is more robust compared to the Newton-Raphson method.     

Quark mass effects toO(α s ) ine + e −→hadrons asymmetries and precision tests of electroweak physics

We estimate, to first order in α _s , quark mass effects on a number of fully integrated and “two-jet” asymmetries for the processe ⁺ e ^?→ \(q\bar q \to q\bar qg\) . We find that the effects of strong interactions are appreciably decreased, especially in the case of theb quark, with respect to the massless case. For the fully integrated asymmetries these effects are sizeable. Concentrating on the “two-jet” asymmetries, we find that for small values of the parameters ε and δ defining a ”two-jet” event all the asymmetries are α _s independent. For larger values of these parameters this is no longer true. However it is still possible to define regions in the (ε, δ) plane where the strong interaction effects can be made arbitrarily small. These important features enhance the role of “two-jet” asymmetries as specially convenient candidates for high precision tests of Electroweak Physics.     

Kelvin states in an inhomogeneous elastic space

Summary An explicit solution to Kelvin's problem in linear elastostatics is given when the indefinite elastic medium in isotropie, but not homogeneous. As a constitutive law, it is assumed that the tangent modulus is a constant, while varies with the distance from the origin according to an exponential law.

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Sommario Viene data una soluzione formale del problema di Kelvin in elastostatica quando il mezzo elastico indefinito è isotropo, ma non omogeneo. Come legge costitutiva, si assume costante il modulo tangenziale , mentre varia con la dlstanza dall'origine secondo una legge esponenziale.

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On leave at Istituto di Scienza delle Costruzioni. Pisa (Italy).     

Convenient and easy access to 2-hydroxycyclopent-2-enones from acylcyanohydrins

A convenient access to 2-hydroxycyclopentenones was designed from acylcyanohydrins, by using titanacyclopropane complexes as nucleophilic partners and an intramolecular aldol condensation in basic conditions. The development of a one-pot procedure allows a step- and atom-economic process, and the use of Grignard reagents other than ethylmagnesium bromide provided valuable 3,4-disubstituted 2-hydroxycyclopentenones. The utility of the hydroxy group was illustrated by further functionalization of the α-position using palladium-mediated cross-coupling reactions.     

Preparation and characterization of the system NiMn2O4/TiO2 by sol–gel: application to the photodegradation of benzamide under visible light

Journal of Sol-Gel Science and Technology - Benzamide is successfully degraded on the novel heterosystem NiMn2O4/TiO2 under visible light. The nanosized spinel is synthesized by the sol–gel...     

Thermodynamic properties of the NdBr3–MBr binary systems (M = Na,K)

Thixoforming involves heating different types of alloys to the semisolid state at high heating rates and forming in die-casting machines or conventional presses. At temperatures higher than the solidus and lower than the liquidus, the mush metal behaves like a high-viscosity thixotropic material. Therefore, determining the thermodynamic behavior of the solid-to-liquid transition is paramount to control thixoforming processes. This article describes a simple, novel experimental setup based on differential thermal analysis (DTA) for analyzing the phase transitions in an alloy heated using high heating rates typical of industrial applications. A365 alloy was chosen to demonstrate the effectiveness of the method as the phase transformations for this alloy in semisolid materials (SSM) processing are well understood. Samples were heated to 750 °C using constant linear heating rates of 5, 10, 15, 20, 25, 50, 75, 100 and 125 °C min in a Norax 25 kW 8 kHz induction furnace with an Omron E5CK temperature controller. AISI 316 austenitic stainless steel was used as the inert reference. Comparison of the results of DTA using the proposed method and the results of simulation with Thermo-Calc^® indicates that the proposed in situ DTA device and its method is suitable for analyzing phase transitions when high heating rates are used.