Development of Surfaces Optically Suitable for Flat Solar Panels

Innovations in reflectometry techniques are described; and the development of an absorbing selective coating is discussed along with details of surface properties. Conclusions as to the parameterization desired for practical applications of selective surfaces are provided

An exactly size consistent geminal power via Jastrow factor networks in a local one particle basis

The accurate but expensive product of geminals ansatz may be approximated by a geminal power, but this approach sacrifices size consistency. Here we show both analytically and numerically that a size consistent form very similar to the product of geminals can be recovered using a network of location specific Jastrow factors. Upon variational energy minimization, the network creates particle number projections that remove the charge fluctuations responsible for size inconsistency. This polynomial cost approach captures strong many-electron correlations, giving a maximum error of just 1.8 kcal/mol during the double-bond dissociation of H2O in an STO-3G atomic orbital basis.Comment: Updated the original arXiv submission to include improvements resulting from journal peer review. 5 pages, 4 figures, 1 tabl

Gradient tempering process

A process for tempering a product made from a metal alloy that produces varying degrees of toughness throughout a cross section of the product is presented

Application of single crystal superalloys for Earth-to-orbit propulsion systems

Single crystal superalloys were first identified as potentially useful engineering materials for aircraft gas turbine engines in the mid-1960's. Although they were not introduced into service as turbine blades in commercial aircraft engines until the early 1980's, they have subsequently accumulated tens of millions of flight hours in revenue producing service. The space shuttle main engine (SSME) and potential advanced earth-to-orbit propulsion systems impose severe conditions on turbopump turbine blades which for some potential failure modes are more severe than in aircraft gas turbines. Research activities which are directed at evaluating the potential for single crystal superalloys for application as turbopump turbine blades in the SSME and advanced rocket engines are discussed. The mechanical properties of these alloys are summarized and the effects of hydrogen are noted. The use of high gradient directional solidification and hot isostatic pressing to improve fatigue properties is also addressed

Spin-independent v-representability of Wigner crystal oscillations in one-dimensional Hubbard chains: The role of spin-charge separation

Electrons in one-dimension display the unusual property of separating their spin and charge into two independent entities: The first, which derive from uncharged spin-1/2 electrons, can travel at different velocities when compared with the second, built from charged spinless electrons. Predicted theoretically in the early sixties, the spin-charge separation has attracted renewed attention since the first evidences of experimental observation, with usual mentions as a possible explanation for high-temperature superconductivity. In one-dimensional (1D) model systems, the spin-charge separation leads the frequencies of Friedel oscillations to suffer a 2k_F -- 4k_F crossover, mainly when dealing with strong correlations, where they are referred to as Wigner crystal oscillations. In non-magnetized systems, the current density functionals which are applied to the 1D Hubbard model are not seen to reproduce this crossover, referring to a more fundamental question: Are the Wigner crystal oscillations in 1D systems non-interacting v-representable? Or, is there a spin-independent Kohn-Sham potential which is able to yield spin-charge separation? Finding an appropriate answer to both questions is our main task here. By means of exact and DMRG solutions, as well as, a new approach of exchange-correlation potential, we show the answer to be positive. Specifically, the v-representable 4k_F oscillations emerge from attractive interactions mediated by positively charged spinless holes -- the holons -- as an additional contribution to the repulsive on-site Hubbard interaction

Performance of periodic piezoelectric composite arrays incorporating a passive phase exhibiting anisotropic properties

This paper explores the minimisation of interelement cross talk in 1-D and 2-D periodic composite array structures through the incorporation of a passive phase exhibiting anisotropic elastic properties. Initially the PZFlex finite element code was used to monitor array aperture response as a function of material properties. It is shown that in array structures comprising passive polymer materials possessing low longitudinal loss and high shear loss, inter-element mechanical cross talk is reduced, without a concomitant reduction in element sensitivity. A number of polymer materials with the desired properties were synthesised and their elastic character confirmed through a program of materials characterisation. Finally, a range of experimental devices exhibiting improved directional response, as a result of a significant reduction in interelement cross talk, are presented and the predicted array characteristics are shown to compare favourably in each case

Random-phase-approximation-based correlation energy functionals: Benchmark results for atoms

The random phase approximation (RPA) for the correlation energy functional of density functional theory has recently attracted renewed interest. Formulated in terms of the Kohn-Sham (KS) orbitals and eigenvalues, it promises to resolve some of the fundamental limitations of the local density and generalized gradient approximations, as for instance their inability to account for dispersion forces. First results for atoms, however, indicate that the RPA overestimates correlation effects as much as the orbital-dependent functional obtained by a second order perturbation expansion on the basis of the KS Hamiltonian. In this contribution, three simple extensions of the RPA are examined, (a) its augmentation by an LDA for short-range correlation, (b) its combination with the second order exchange term, and (c) its combination with a partial resummation of the perturbation series including the second order exchange. It is found that the ground state and correlation energies as well as the ionization potentials resulting from the extensions (a) and (c) for closed sub-shell atoms are clearly superior to those obtained with the unmodified RPA. Quite some effort is made to ensure highly converged RPA data, so that the results may serve as benchmark data. The numerical techniques developed in this context, in particular for the inherent frequency integration, should also be useful for applications of RPA-type functionals to more complex systems.Comment: 11 pages, 7 figure

Mito, Modo y Género en algunos clásicos de la literatura española

La Anatomía de Frye nos hizo más conscientes de los mitos y arquetipos de la literatura, pero sirvió también para hacernos volver sobre cuestiones de modo y género. Examino la estructura mítica –o sea el mito del deseo– del Libro de buen amor solamente, para luego considerar los modos y géneros que entran en juego en obras tan diversas como el Lazarillo, el Quijote, La Celestina y la comedia nueva. El radical de presentación y el axis mundi son otros conceptos útiles comentados y aplicados. Frye’s Anatomy was instrumental in making us more aware of the myths and archetypes of literature, but it also inspired much reconsideration of issues of mode and genre. I look at myth –the myth of desire– only in the Libro de buen amor, then at the interplay of mode and genre in the Lazarillo, the Quixote, the Celestina and the comedia nueva. Each is complex in that it illustrates generic blending. Frye’s radical of presentation and axis mundi are also discussed and applied

SOYBEAN TRADER: A MICROCOMPUTER SIMULATION OF INTERNATIONAL AGRICULTURAL TRADE

Soybean Trader is a microcomputer simulation of international grain trading. The program uses the format of a graphics-oriented game to teach basic economic principles and to stimulate interest in agricultural trade. Profits from trading serve as a score, and competition is encouraged by ranking top scores in Trader's Hall of Fame. Results of tests with adult and youth audiences indicated that the program is an interesting and effective teaching tool.International Relations/Trade,

Fractional charge perspective on the band-gap in density-functional theory

The calculation of the band-gap by density-functional theory (DFT) methods is examined by considering the behavior of the energy as a function of number of electrons. It is found that the incorrect band-gap prediction with most approximate functionals originates mainly from errors in describing systems with fractional charges. Formulas for the energy derivatives with respect to number of electrons are derived which clarify the role of optimized effective potentials in prediction of the band-gap. Calculations with a recent functional that has much improved behavior for fractional charges give a good prediction of the energy gap and also $\epsilon_{{\rm homo}}\simeq-I$ for finite systems. Our results indicate it is possible, within DFT, to have a functional whose eigenvalues or derivatives accurately predict the band-gap