Like vs. Like: Strategy and Improvements in Supernova Cosmology Systematics

Control of systematic uncertainties in the use of Type Ia supernovae as standardized distance indicators can be achieved through contrasting subsets of observationally-characterized, like supernovae. Essentially, like supernovae at different redshifts reveal the cosmology, and differing supernovae at the same redshift reveal systematics, including evolution not already corrected for by the standardization. Here we examine the strategy for use of empirically defined subsets to minimize the cosmological parameter risk, the quadratic sum of the parameter uncertainty and systematic bias. We investigate the optimal recognition of subsets within the sample and discuss some issues of observational requirements on accurately measuring subset properties. Neglecting like vs. like comparison (i.e. creating only a single Hubble diagram) can cause cosmological constraints on dark energy to be biased by 1\sigma or degraded by a factor 1.6 for a total drift of 0.02 mag. Recognition of subsets at the 0.016 mag level (relative differences) erases bias and reduces the degradation to 2%.Comment: 11 pages, 6 figure

Single stage experimental evaluation of slotted rotor and stator blading. Part I - Analysis and design

Analysis and design of slotted rotor and stator blading for application to compressors in advanced airbreathing propulsion system

Quasiclassical theory for the superconducting proximity effect in Dirac materials

We derive the quasiclassical non-equilibrium Eilenberger and Usadel equations to first order in quantities small compared to the Fermi energy, valid for Dirac edge and surface electrons with spin-momentum locking, as relevant for topological insulators. We discuss in detail several of the key technical points and assumptions of the derivation, and provide a Riccati-parametrization of the equations. Solving first the equilibrium equations for S/N and S/F bilayers and Josephson junctions, we study the superconducting proximity effect in Dirac materials. Similarly to related works, we find that the effect of an exchange field depends strongly on the direction of the field. Only components normal to the transport direction lead to attenuation of the Cooper pair wavefunction inside the F. Fields parallel to the transport direction lead to phase-shifts in the dependence on the superconducting phase difference for both the charge current and density of states in an S/F/S-junction. Moreover, we compute the differential conductance in S/N and S/F bilayers with an applied voltage bias, and determine the dependence on the length of the N and F regions and the exchange field.Comment: 13 pages, 5 figures. Accepted for publication in Phys. Rev.

The Intrinsic Magnetization of Antiferromagnetic Textures

Antiferromagnets (AFMs) exhibit intrinsic magnetization when the order parameter spatially varies. This intrinsic spin is present even at equilibrium and can be interpreted as a twisting of the homogeneous AFM into a state with a finite spin. Because magnetic moments couple directly to external magnetic fields, the intrinsic magnetization can alter the dynamics of antiferromagnetic textures under such influence. Starting from the discrete Heisenberg model, we derive the continuum limit of the free energy of AFMs in the exchange approximation and explicitly rederive that the spatial variation of the antiferromagnetic order parameter is associated with an intrinsic magnetization density. We calculate the magnetization profile of a domain wall and discuss how the intrinsic magnetization reacts to external forces. We show conclusively, both analytically and numerically, that a spatially inhomogeneous magnetic field can move and control the position of domain walls in AFMs. By comparing our model to a commonly used alternative parametrization procedure for the continuum fields, we show that the physical interpretations of these fields depend critically on the choice of parametrization procedure for the discrete-to-continuous transition. This can explain why a significant amount of recent studies of the dynamics of AFMs, including effective models that describe the motion of antiferromagnetic domain walls, have neglected the intrinsic spin of the textured order parameter.Comment: 12 pages, 7 figure

Paper Session I-A - An Examination of the Human Factors Support of NASA\u27s Safety Directorate on the Space Station Processing Facility

The goal of the Human Factors Engineering (HFE) pilot project undertaken by NASA on the Space Station Processing Facility (SSPF) at Kennedy Space Center, Florida, is to demonstrate the advantages of using Human Factors to support NASA Safety. The primary objective of the project is to demonstrate how Human Factors can assist in decreasing the causes of accidents by reducing error producing situations. The project began with a review of design drawings for the SSPF, in which all Human Factors (HF) concerns were identified especially those that affected personnel safety, pay load protection, and operational efficiency. Visits to other KSC facilities produced insights that could be applied to the drawing critiques when the drawings were not sufficient to disclose how the facility\u27s characteristics would fulfill operational needs. Overall, the drawing review revealed a broad range of HF and Safety concerns. When possible, these concerns were discussed with the appropriate engineering personnel to effect workable solutions. To date, some of these HF & Safety concerns have been resolved by incorporating HF principles. Thus, this project has reduced potential problems that can contribute to accidents and costly delays, such as the Magellan Spacecraft incident in October of 1988. This incident typifies payload processing problems that can develop unexpectedly within any processing facility when Human Factors issues are either ignored or overlooked in the initial design of the spacecraft or in developing appropriate service and checkout procedures. Although the problem occurred on a spacecraft, this type of problem also could easily occur within a processing facility, on payloads that are being processed, or on the ground support equipment being used to process the payloads. In addition, this project has led to the evaluation of candidate methods for the implementation of HF. Among these, a means of conducting HF evaluations during Engineering Prototyping in a Computer Aided Design environment. This innovative technique is expected to demonstrate the Safety advantage and substantial cost savings of incorporating HF principles