Experimental investigation and analysis of two sources of nozzle-thrust misalignment

Asymmetry of nozzle's throat produces oscillatory type net side-force axial profile. Using mean values of localized static pressure and Mach number, scaling laws for flat-plate supersonic flow over protrusion are applied to nozzle expansion cone irregularities to give approximate indication of perturbed-pressure profiles and induced side forces

Land issues and poverty reduction: Requirements for lasting peace in Sudan and Afghanistan

Poverty reduction, Hunger, Poverty, Underdevelopment, Agricultural growth, War and peace,

Cold-flow experimental investigation and analysis of two sources of nozzle thrust misalignment

Cold flow investigation and analysis of two nozzle thrust misalignmen

Double precision trajectory program /DPTRAJ 2.2C/

Four part program computes trajectory of space probe moving in solar system and subject to variety of forces

The Dynamical Mean Field Theory phase space extension and critical properties of the finite temperature Mott transition

We consider the finite temperature metal-insulator transition in the half filled paramagnetic Hubbard model on the infinite dimensional Bethe lattice. A new method for calculating the Dynamical Mean Field Theory fixpoint surface in the phase diagram is presented and shown to be free from the convergence problems of standard forward recursion. The fixpoint equation is then analyzed using dynamical systems methods. On the fixpoint surface the eigenspectra of its Jacobian is used to characterize the hysteresis boundaries of the first order transition line and its second order critical end point. The critical point is shown to be a cusp catastrophe in the parameter space, opening a pitchfork bifurcation along the first order transition line, while the hysteresis boundaries are shown to be saddle-node bifurcations of two merging fixpoints. Using Landau theory the properties of the critical end point is determined and related to the critical eigenmode of the Jacobian. Our findings provide new insights into basic properties of this intensively studied transition.Comment: 11 pages, 12 figures, 1 tabl

Efficient implementation of the Gutzwiller variational method

We present a self-consistent numerical approach to solve the Gutzwiller variational problem for general multi-band models with arbitrary on-site interaction. The proposed method generalizes and improves the procedure derived by Deng et al., Phys. Rev. B. 79 075114 (2009), overcoming the restriction to density-density interaction without increasing the complexity of the computational algorithm. Our approach drastically reduces the problem of the high-dimensional Gutzwiller minimization by mapping it to a minimization only in the variational density matrix, in the spirit of the Levy and Lieb formulation of DFT. For fixed density the Gutzwiller renormalization matrix is determined as a fixpoint of a proper functional, whose evaluation only requires ground-state calculations of matrices defined in the Gutzwiller variational space. Furthermore, the proposed method is able to account for the symmetries of the variational function in a controlled way, reducing the number of variational parameters. After a detailed description of the method we present calculations for multi-band Hubbard models with full (rotationally invariant) Hund's rule on-site interaction. Our analysis shows that the numerical algorithm is very efficient, stable and easy to implement. For these reasons this method is particularly suitable for first principle studies -- e.g., in combination with DFT -- of many complex real materials, where the full intra-atomic interaction is important to obtain correct results.Comment: 19 pages, 7 figure

Spin Injection and Relaxation in Ferromagnet-Semiconductor Heterostructures

We present a complete description of spin injection and detection in Fe/Al_xGa_{1-x}As/GaAs heterostructures for temperatures from 2 to 295 K. Measurements of the steady-state spin polarization in the semiconductor indicate three temperature regimes for spin transport and relaxation. At temperatures below 70 K, spin-polarized electrons injected into quantum well structures form excitons, and the spin polarization in the quantum well depends strongly on the electrical bias conditions. At intermediate temperatures, the spin polarization is determined primarily by the spin relaxation rate for free electrons in the quantum well. This process is slow relative to the excitonic spin relaxation rate at lower temperatures and is responsible for a broad maximum in the spin polarization between 100 and 200 K. The spin injection efficiency of the Fe/Al_xGa_{1-x}As Schottky barrier decreases at higher temperatures, although a steady-state spin polarization of at least 6 % is observed at 295 K.Comment: 3 Figures Submitted to Phys. Rev. Let