Directions in propulsion control

The research needs in the area of propulsion control as driven by trends in advanced aircraft are considered. Ongoing propulsion control research at NASA Lewis is discussed. Special emphasis is made on research to improve control system reliability through the use of analytical redundancy to accommodate failed control sensors. In conclusion, a discussion of new research thrusts in the area of supersonic STOVL integrated control and intelligent system control is presented

Scaling of Power Corrections for Angularities from Dressed Gluon Exponentiation

We study power corrections to a recently introduced family of event shapes, the class of angularities, within the formalism of dressed gluon exponentiation (DGE). We find that the universal scaling rule for the leading power corrections deduced from resummation also holds when taking renormalon enhancements into account. The scaling is due to boost invariance of eikonal dynamics in the two-jet limit, which we recover in the context of DGE. Furthermore, dressed gluon exponentiation provides an ansatz for non-leading power corrections that violate the scaling. These non-leading corrections are further suppressed by non-integer powers of the hard scale.Comment: 24 page

Directions in propulsion control

Discussed here is research at NASA Lewis in the area of propulsion controls as driven by trends in advanced aircraft. The objective of the Lewis program is to develop the technology for advanced reliable propulsion control systems and to integrate the propulsion control with the flight control for optimal full-system control

Symbolic reduction of block diagrams using FORMAC

Two computer programs - one written in FORMAC to generate the desired symbolic expressions, the other in FORTRAN 4 to numerically evaluate the expressions are announced. The FORTRAN program accepts the symbolic punched output from the FORMAC program in either unexpanded or expanded form. It numerically evaluates the expressions

B -> X_d gamma and constraints on new physics

We combine recent progress in measuring the branching ratio of the decay B->X_d gamma$ with the discovery that hadronic uncertainties in the CP-averaged branching ratio drop out to a large extent. Implications of these improvements on the size of possible new physics effects are investigated. We find the updated SM prediction for the CP-averaged branching ratio to be Br[B->X_d gamma]^SM_E_gamma>1.6 GeV = 1.54^+0.26-0.31*10^-5, which should be compared with the experimental value of Br[B->X_d gamma]^exp_E_gamma>1.6GeV = (1.41+-0.57) 10^-5. After performing a model independent analysis, we consider different new physics models: the MSSM with generic sources of flavor violation, the two Higgs doublet model of type III and a model with right-handed charged currents. It is found that the constraints on the SUSY parameters delta^d_13 have improved and that the absolute value of the right-handed quark mixing matrix element |V^R_td| must be smaller than 1.5*10^-4.Comment: 5 pages, 3 figures, experimental value for b->d+gamma corrected, version accepted for publication in PR

Real-time growth rate for general stochastic SIR epidemics on unclustered networks

Networks have become an important tool for infectious disease epidemiology. Most previous theoretical studies of transmission network models have either considered simple Markovian dynamics at the individual level, or have focused on the invasion threshold and final outcome of the epidemic. Here, we provide a general theory for early real-time behaviour of epidemics on large configuration model networks (i.e. static and locally unclustered), in particular focusing on the computation of the Malthusian parameter that describes the early exponential epidemic growth. Analytical, numerical and Monte-Carlo methods under a wide variety of Markovian and non-Markovian assumptions about the infectivity profile are presented. Numerous examples provide explicit quantification of the impact of the network structure on the temporal dynamics of the spread of infection and provide a benchmark for validating results of large scale simulations.Comment: 45 pages, 8 figures, submitted to Mathematical Biosciences on 29/11/2014; Version 2: resubmitted on 15/04/2015; accepted on 17/04/2015. Changes: better explanations in introduction; restructured section 3.3 (3.3.3 added); section 6.3.1 added; more precise terminology; typos correcte

The impact of tidal errors on the determination of the Lense-Thirring effect from satellite laser ranging

The general relativistic Lense-Thirring effect can be detected by means of a suitable combination of orbital residuals of the laser-ranged LAGEOS and LAGEOS II satellites. While this observable is not affected by the orbital perturbation induced by the zonal Earth solid and ocean tides, it is sensitive to those generated by the tesseral and sectorial tides. The assessment of their influence on the measurement of the parameter mu, with which the gravitomagnetic effect is accounted for, is the goal of this paper. After simulating the combined residual curve by calculating accurately the mismodeling of the more effective tidal perturbations, it has been found that, while the solid tides affect the recovery of mu at a level always well below 1%, for the ocean tides and the other long-period signals Delta mu depends strongly on the observational period and the noise level: Delta mu(tides) amounts to almost 2% after 7 years. The aliasing effect of K1 l=3 p=1 tide and SRP(4241) solar radiation pressure harmonic, with periods longer than 4 years, on the perigee of LAGEOS II yield to a maximum systematic uncertainty on \m_{LT} of less than 4% over different observational periods. The zonal 18.6-year tide does not affect the combined residuals.Comment: 24 pages, 4 tables, 6 figures, submitted to Int. Journal of Mod. Phys. D. Changes in auctorship, references and conten

Energy-state formulation of lumped volume dynamic equations with application to a simplified free piston Stirling engine

Lumped volume dynamic equations are derived using an energy state formulation. This technique requires that kinetic and potential energy state functions be written for the physical system being investigated. To account for losses in the system, a Rayleigh dissipation function is formed. Using these functions, a Lagrangian is formed and using Lagrange's equation, the equations of motion for the system are derived. The results of the application of this technique to a lumped volume are used to derive a model for the free piston Stirling engine. The model was simplified and programmed on an analog computer. Results are given comparing the model response with experimental data