Neutron irradiation effects on martensitic iron-nickel alloys

Summary Iron-nickel alloys in the range from 29 to 32 wt.% Ni have been irradiated with an integral flux of 3·10¹⁸ n cm⁻² and then subjected to martensitic transformation. the resistivity, magnetoresistivity and Hall-effect measurements performed on the irradiated samples allow us to support the formation of iron-rich or nichel-rich ordered microstructures and additional α-phase from the supersaturated γ-matrix. The nickel content of the above-ordered region, is evaluated from the behaviour of the anomalous Hall effect in the irradiated specimens with different composition.

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Riassunto Leghe di ferro-nichel, con contenuto in Ni variabile dal 29% al 32%, sono state irradiate con un fascio di neutroni avente flusso integrale di 3·10¹⁸ n cm⁻² a 80°C e sono state successivamente sottoposte a trasformazione martensitica mediante raffreddamento. Le misure di resistività, di magnetoresistenza e di effetto Hall compiute sui campioni irradiati consentono di fare l'ipotesi della presenza nella fase supersatura γ di microstrutture ordinate, ricche di Fe o di Ni, oltre ad una fase α addizionale. Dal comportamento dell'effetto Hall anomalo nei campioni irradiati si è valutato il contenuto di Ni presente nelle regioni ordinate.

     

On oscillation and nonoscillation properties of Emden-Fowler difference equations

A characterization of oscillation and nonoscillation of the Emden-Fowler difference equation

Membrane bioreactor processes: a must for the wastewater treatment plants of the Lagoon of Venice

A pilot scale experimentation of a membrane bioreactor has been progressing since 1999 at Fusina-Venice wastewater treatment plant. Results showed that the limits introduced by Law Decree 30 July 1999 (Decree "Ronchi-Costa") can be fulfilled (except for Arsenic) and treated water is suitable for reuse purposes. According to the results reported in this paper, sizing and involved costs for the membranes application at Fusina wastewater treatment plant are presented. This can be the proper engineering solution for the Integrated Project Fusina.     

A collocation method to fit geophysical survey data

A self adaptive collocation method has been applied to the quantitative interpretation of geophysical survey data. Examples of interpretation of vertical electrical soundings (VES) and magneto-telluric soundings (MTS) have been chosen for this work due to the high nonlinearity of the response functions and to the high degree of correlation of the parameters involved. In both cases horizontally isotropic multi-layered models have been adopted.For comparison two different computing algorithms have been considered. In the first, using a generalized inverse formulation a new different decomposition into characteristic values has been used. In the second the Marquardt procedure has been modified in an original way to give a faster convergence using a strategy based on the contemporary adjustment of the step length and the direction of the regression. The confidence limits of the results have been evaluated.Results are given for interpretation of both MTS and VES curves using the two different algorithms. Model data and field data have been considered for an effective comparison of speed of convergence and accuracy.     

Calculations of molecular wave functions in terms of modulated plane waves

The possibility of representing molecular orbitals in terms of a many centre expansion of modulated plane waves is discussed. All integrals appearing in the usual SCF procedure for the calculation of the energy are obtained in an analytical form. The resulting formulae are rather simple to be evaluated.

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Zusammenfassung Es wird die Möglichkeit, Molekülorbitale mittels einer Mehrzentrenentwicklung von modulierten ebenen Wellen darzustellen, diskutiert. Alle Integrale, die in einer SCF-Rechnung üblichen Typs (z. B. CNDO) erscheinen, werden in einer einfach auszuwertenden analytischen Form angegeben.

     

Tricyclic heteroaromatic systems. 5H-1,2,3-triazolo[5,1-c][1,4]benzodiazepine

The synthesis of the new tricyclic system 5H-1,2,3-triazolo[5,1-c][1,4]benzodiazepine, diaza-analogue of 5H-pyrrolo[2,1-c][1,4]benzodiazepine, which is the common feature of some antitumor antibiotics, is reported. The structure of the new tricyclic system and of some of its key intermediates is assigned by means of a ¹³C nmr study.     

New enantiopure C2 symmetric bis(2-oxazolinyl)cage (Cage-Box) ligands from 4,5-dicyanopyridazine

7,8-Dicyanotetracyclo[7.3.0.0^2,60^5,10]dodec-7-ene 3, obtained from 4,5-dicyanopyridazine 1 and cycloocta-1,5-diene 2 through a three-step pericyclic homodomino process, was found to react with optically active β-amino alcohols 4a–d, under zinc chloride catalysis, to afford a new class of enantiopure C₂ symmetric bis(oxazolinyl)cage (Cage-Box) ligands 6a–d, along with the corresponding mono(oxazolinyl) derivatives 5a–d.     

On a cyclic disconjugate operator associated to linear differential equations

In this paper the disconjugate linear differential operator of n-th order D^1/(n) given by $$D_1^{(n)} (x)(t) = \frac{1}{{a_n (t)}}\frac{d}{{dt}}\frac{1}{{a_{n - 1} (t)}} \ldots \frac{1}{{a_1 (t)}}\frac{d}{{dt}}x(t)$$ is considered together with other n?1 operators, which are obtained from D ₁ ⁽ⁿ⁾ by an ordered cyclic permutation of the functions a_i. Such operators play an important role in the study of oscillation of the associated linear differential equation (*) $$D_1^{(n)} (x)(t) \pm x(t) = 0.$$ Some properties of these operators suggest the new idea of «isomorphism of oscillation». The existence of an isomorphism of oscillation allows to describe the oscillatory or nonoscillatory behavior of solutions of (*) by the oscillatory or nonoscillatory behavior of solutions of other n ?1 suitable linear differential equations. From this fact one can easily obtain new results about oscillation or nonoscillation of (*) that might be hard to prove directly. Several interesting consequences concerning the classification of solutions of (*) are also presented together with some new applications to the structure of the set of nonoscillatory solutions of (*).     

Discrete and continuous models for in plane loaded random elastic brickwork

The aim of this paper is to study non-periodic masonries – typical of historical buildings – by means of a perturbation approach and to evaluate the effect of a random perturbation on the elastic response of a periodic masonry wall. The random masonry is obtained starting from a periodic running bond pattern. A random perturbation on the horizontal positions of the vertical interfaces between the blocks which form the masonry wall is introduced. In this way, the height of the blocks is uniform, while their width in the horizontal direction is random. The perturbation is limited such as each block has still exactly 6 neighboring blocks. In a first discrete model, the blocks are modeled as rigid bodies connected by elastic interfaces (mortar thin joints). In other words, masonry is seen as a “skeleton” in which the interactions between the rigid blocks are represented by forces and moments which depend on their relative displacements and rotations. A second continuous model is based on the homogenization of the discrete model. Explicit upper and lower bounds on the effective elastic moduli of the homogenized continuous model are obtained and compared to the well-known effective elastic moduli of the regular periodic masonry. It is found that the effective moduli are not very sensitive to the random perturbation (less than 10%). At the end, the Monte Carlo simulation method is used to compare the discrete random model and the continuous model at the structural level (a panel undergoing in plane actions). The randomness of the geometry requires the generation of several samples of size L of the discrete masonry. For a sample of size L, the structural discrete problem is solved using the same numerical procedure adopted in [Cecchi, A., Sab, K., 2004. A comparison between a 3D discrete model and two homogenized plate models for periodic elastic brickwork, International Journal of Solids Structures 41 (9–10), 2259–2276] and the average solution over the samples gives an estimation which depends on L. As L increases, an asymptotic limit is reached. One issue is to find the minimum size for L and to compare the asymptotic average solution to the one obtained from the continuous homogenized model.