Allan variance of frequency fluctuations due to momentum exchange and thermomechanical noises

We investigate the Allan variance of nanoresonators with random rough surfaces under the simultaneous influence of thermomechanical and momentum exchange noises. Random roughness is observed in various surface engineering processes, and it is characterized by the roughness amplitude w, the lateral correlation length ξ, and the roughness exponent 0<H<1. The roughness influence becomes significant for measurement time τA so that ωoτA~1, with ωo the fundamental resonance frequency. The Allan variance increases significantly with increasing roughness (decreasing H and/or increasing ratio w/ξ) if the quality factor due to gas collisions is smaller than the intrinsic quality factor associated with thermomechanical noise.

Computational interferometric description of nested flow fields

Computer graphics and theoretical descriptions of density are used to obtain computer generated flow visualizations called computational interferograms. Computational interferograms are pictorially analogous to optical interferograms, and examples showing the fringe pattern for the flow about a sharp tip cone in a supersonic air stream are presented. To ascertain the effect of unsteady behavior, local density disturbances are added to the steady state flow field. This introduces irregularities to the computational interferogram like those seen in the optical interferograms. These theoretical disturbances can be varied in geometry, density description, translated with time, and strengthened or dissipated. The accuracy of computational interferometry relies on the accuracy of the theoretical density descriptions and therefore, it provides a way of verifying existing models of flow fields, especially those containing unsteady or turbulent behavior. In addition to being a unique method of flow visualization, computational interferometry can be used to develop and modify theories or numerical solutions to both simple and complex flow fields. The presented research is a general description of this process

The Macroeconomics of Low Inflation

macroeconomics, low inflation

Near-Rational Wage and Price Setting and the Long-Run Phillips Curve

macroeconomics, Near-Rational Wage, Price Setting, Long-Run Phillips Curve

The role of merchandise exports to Mexico in the pattern of Texas employment

In 1987, Texas exported $25 billion worth of merchandise to foreign countries. Twenty-six percent, or$6.5 billion, of those exports went south to Mexico. By 1994, Texas merchandise exports to Mexico had grown to more than $18.5 billion per year (in 1987 constant dollars). Texas merchandise exports to Mexico (in real terms) have grown more than 10 percent a year for six of the last seven years. ; Using input-output analysis, Kelly George and Lori Taylor find that merchandise exports to Mexico, while representing only about 5 percent of Texas output, have grown in ways that have substantially influenced the composition of the state's economy. The authors attribute a small portion of the state's overall job gains since 1987 to rising merchandise exports to Mexico but find that almost all Texas employment growth in high-tech manufacturing sectors stems from trade with Mexico.Employment (Economic theory) ; Exports ; Mexico ; Texas

Effects of atomic short-range order on the properties of perovskite alloys in their morphotropic phase boundary

The effects of atomic short-range order on the properties of Pb(Zr_{1-x}Ti_x)O_3 alloy in its morphotropic phase boundary (MPB) are predicted by combining first-principles-based methods and annealing techniques. Clustering is found to lead to a compositional expansion of this boundary, while the association of unlike atoms yields a contraction of this region. Atomic short-range order can thus drastically affect properties of perovskite alloys in their MPB, by inducing phase transitions. Microscopic mechanisms responsible for these effects are revealed and discussed.Comment: 4 pages, with 2 postscript figures embedded. Uses REVTEX4 and graphicx macro