Designing information structures for quadratic decision problems

This paper investigates the problem of unconstrained optimization when there is only partial information on the random parameters in the objective function. The relation between the optimization performance and the available information is established. The best information structure design with fixed rank is described. The designing procedure is set up in such a way that successive information augmentation or deletion can be considered. The procedure can also be extended to multiperson decision problems.     

Diffusion and reaction in random media and models of evolution processes

A diffusion equation including source terms, representing randomly distributed sources and sinks is considered. For quasilinear growth rates the eigenvalue problem is equivalent to that of the quantum mechanical motion of electrons in random fields. Correspondingly there exist localized and extended density distributions dependent on the statistics of the random field and on the dimension of the space. Besides applications in physics (nonequilibrium processes in pumped disordered solid materials) a new evolution model is discussed which considers evolution as hill climbing in a random landscape.We dedicate this work to the memory of Ilya M. Lifshitz.     

Robust inverse optimal control for flexible structures

An inverse optimal control problem is formulated to develop robust control laws for purely oscillatory systems. The optimal control solution requires output feedback with specified constraints, leading to robustness with respect to unmodeled modes and a large class of parameter variations. The robustness properties are proved directly from known properties of control laws resulting from quadratic performance indices. The control laws are useful for poorly damped flexible structures.This research was supported by the Office of Naval Research, Contract No. N00014-77-C-0247.     

Mode structure in wideband waveguide radiofrequency CO2 lasers

We have analysed the mode structure of a wideband radiofrequency excited waveguide CO₂ laser by using different waveguide diameters and optical cavities. In particular we have observed the phase shift of some linear polarized waveguide modes in the transition region between the guided and the free Gaussian propagation.     

Molecular modeling of polymers. 10. Characterization of conformational transitions of poly(acrylic acid) and poly(methacrylic acid) using dyad structures

The conformational profiles of nearest side-chain neighbors, methylene-dyad structures, of poly(acrylic acid), PAA, and poly(methacrylic acid), PMA, were determined as a function of tacticity, extent of ionization, and presence of counterion. The dominant backbone conformer states are quite similar for both isotactic and syndiotactic diads in a common charge state. Thus, the overall dimensional properties of isotactic syndiotactic and atactic chains of PAA or PMA, based upon dyad interactions, are predicted to be alike for a given charge state. Significant deviations from precise t, g⁺, and g^? states are found for the dyad minimum energy conformations. The rod-to-coil and coil-to-rod transitions observed in PAA and PMA, respectively, as a function of increasing counterion concentration can be explained, to a large extent, by the conformational profiles of the corresponding dyad model structures. © 1994 John Wiley & Sons, Inc.     

Structural Relations in the Family of Nonmetallic Filled β-Manganese Phases: The new members AGa6Te10 (A: Sn,Pb) and PbIn6Te10

Nonmetallic filled β-manganese phases form a new class of solids with a wide spaced (“eutactical”) partial structure of nonmetal atoms (Te, I), which is topologically equivalent to the arrangement of manganese atoms in cubic β-Mn (a = 6.315 Å, P4₁32, Z = 20), a manganese polymorph crystallizing in a tetrahedrally close packed structure. Different fractions of the 100 tetrahedral and 4 metaprismatic holes per unit cell of the β-Mn like arrangement of nonmetal atoms are occupied by metal atoms or pairs of covalently bonded metal atoms, leading to the different chemical compositions M₇Te₁₀, AM₆Te₁₀, Ag₂Ga₆Te₁₀, RbX₄I₅ (M: Al, Ga, In; A: Ca, Pb, Sn; X: Ag, Cu;). Basic structural properties and structural relations between the members of this new family of solids are discussed. In addition we present structural data for three new members of the family of filled β-Mn phases: SnGa₆Te₁₀ (single crystal data: a = 10.203 Å, α = 89.94°, space group R32, Z = 2) PbIn₆Te₁₀ (single crystal data: a = 10.619 Å, R32, Z = 2) and PbGa₆Te₁₀ (powder data: a = 10.237 Å, α = 89.93°, R32, Z = 2).     

EXAFS spectroscopy,from one perspective

Summary Extended X-ray absorption fine-structure (EXAFS) spectroscopy has been demonstrated to be a most useful probe of short-range interatomic correlations in a wide variety of materials. The theory of the EXAFS is presented in its simplest form so as to provide the basis for a discussion about the kind and quality of the structural information which can be extracted from EXAFS data. The adequacy of several of the approximations commonly incorporated in this theory is examined with emphasis on those areas of the theory which bear most directly on the analysis of EXAFS data. Paper presented at the Workshop on ?EXAFS Data Analysis in Disordered Systems?, held in Parma, October 5–7, 1981.     

EXAFS results on metallic amorphous alloys and on metallurgy

Summary A review of some general trends of EXAFS in alloys and metallic glasses is given. The intrinsic qualities of the EXAFS method in metallurgy, structure of amorphous materials, clustering and spin glasses are discussed. Paper presented at the Workshop on ?EXAFS Data Analysis in Disordered Systems?, held in Parma, October 5–7, 1981.     

Reaction48Ca (p,n)48Sc fromE p =1.885 to 5.1 MeV

The total (p, n) reaction cross section for⁴⁸Ca has been measured as a function of proton energy in the energy range 1.885 to 5.100 MeV with an overall resolution of ∼ 2 keV and in ∼ 5 keV energy steps. The fluctutions in fine resolution data have been analysed to determine the average coherence width 〈Γ〉. The excitation function averaged over large energy intervals has been analyzed in terms of the optical model. The isobaric analogue resonances atE _p ∼ 1.95 and 4 MeV have been shape-analyzed to extract the proton partial width and the spectroscopic factorS _n . A comparison of the gross structures observed in ∼ 55 keV averaged excitation function with the predictions of Izumo’s partial equilibrium model has also been made.