Silicoaluminophosphate molecular sieves: Characterization of textural and acidic properties

The silicoaluminophosphate SAPO-37 as well as ZSM-20 zeolite have a faujaside-like structure and are potentially useful as catalysts. We report in this work different procedures to decompose the organic template occluded in SAPO-37. The texture of the final products was analyzed by means of nitrogen adsorption. The acid properties of SAPO-37 and ZSM-20 were also compared by IR measurements of adsorbed pyridine and related to the acidic properties of the presently commonly used cracking catalyst zeolite Y.

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Partially and totally asynchronous algorithms for linear complementarity problems

A unified treatment is given for partially and totally asynchronous parallel successive overrelaxation (SOR) algorithms for the linear complementarity problem. Convergence conditions are established and compared to previous results. Convergence of the partially asynchronous method for the symmetric linear complementarity problem can be guaranteed if the relaxation factor is sufficiently small. Unlike previous results, this relaxation factor interval does not depend explicitly on problem size.This material is based on research supported by the Air Force Office of Scientific Research Grant No. AFOSR-89-0410.The author wishes to thank the referee for pointing out how to improve the bound (12). The same technique can be used to reduce the factorn in Ref. 5, p. 553, to .     

Potential surfaces for time-like geodesics in the Curzon metric

In this paper we deduce the general pattern of the potential surfaces for time-like geodesics in the Curzon metric. We find that for fairly small energies and orbital angular momenta, the time-like geodesics group into two sets; the geodesics of one set tend to thez-axis asR=(r²+z²)^1/2 0,R=0 being a directional singularity, the others tend to ther-axis. At low energies these two sets are detached but they merge together as the energy increases. Stable circular motion is confined to thez = 0-plane and an energy threshold for stationary motion exists and is equal (per unit of rest-mass energy) to 0.945, a value almost indistinguishable from that in the Schwarzschild space-time.     

On solving a D.C. programming problem by a sequence of linear programs

We are dealing with a numerical method for solving the problem of minimizing a difference of two convex functions (a d.c. function) over a closed convex set in ⁿ . This algorithm combines a new prismatic branch and bound technique with polyhedral outer approximation in such a way that only linear programming problems have to be solved.Parts of this research were accomplished while the third author was visiting the University of Trier, Germany, as a fellow of the Alexander von Humboldt foundation.     

The prediction of the behaviour of Λ-hyperon electromagnetic form factors

The behaviour of the -hyperon electric and magnetic form factors is predicted within the modified three resonance ((783), (1020), (1680)) vector-meson dominance (VMD) model with correct analytic properties and the asymptotic behaviour predestinated by the quark model for baryons. The resonance couplings to are evaluated from the known couplings to nucleons by utilizing theSU(3) symmetry and normalization conditions for Dirac and Pauli form factors. The masses and widths of the considered vector mesons are fixed at the world averaged values. The optimal position of the effective inelastic threshold, common for Dirac and Pauli form factors, is determined from the fit of the only existing Orsay DM2 point on the cross section att=5·693 GeV². The mean square charge and magnetic radii of the -hyperon are found to be r _E ² =0·018 F² and r _M ² =–0·027 F², respectively.The authors are very much indebted to Prof. R. Baldini-Ferroli for calling their attention to the problem of -hyperon e.m. ff 's in connection with the FENICE experiment.