Flow Visualization Techniques for Flight Research

In-flight flow visualization techniques used at the Dryden Flight Research Facility of NASA Ames Research Center (Ames-Dryden) and its predecessor organizations are described. Results from flight tests which visualized surface flows using flow cones, tufts, oil flows, liquid crystals, sublimating chemicals, and emitted fluids have been obtained. Off-surface flow visualization of vortical flow has been obtained from natural condensation and two methods using smoke generator systems. Recent results from flight tests at NASA Langley Research Center using a propylene glycol smoker and an infrared imager are also included. Results from photo-chase aircraft, onboard and postflight photography are presented

Book Reviews

Book Review

No Longer a Neutral Magistrate: The Foreign Intelligence Surveillance Court in the Wake of the War on Terror

Since the founding of our nation, the executive, judicial, and legislative branches of government have struggled with maintaining an appropriate balance between gathering intelligence for national security purposes and protecting the civil liberties of United States citizens. This difficulty is compounded by the uniquely challenging separation of powers issues national security problems present. In 1978, after the scale tipped too far toward “security” at the expense of personal liberties, the United States Senate formed the United States Select Committee to Study Governmental Operations with Respect to Intelligence Activities (Church Committee) to investigate executive overreach and recommend structural and statutory changes to ensure such overreach did not occur again. In response to the Church Committee’s recommendations, among other reforms, Congress enacted the Foreign Intelligence Surveillance Act (FISA) and created the FISA Court. FISA conformed with the Church Committee’s recommendations for over two decades, but, in the wake of 9/11, Congress significantly altered FISA’s scheme, opening the door once again to executive overreach. Because of post-9/11 changes to FISA, the executive branch is able to engage in practices similar to those that catalyzed the formation of the Church Committee and the enactment of FISA. This Article chronicles the evolution of FISA and the FISA Court. Drawing from the unique perspective of Vice President Mondale — who, while a Senator, served as a member of the Church Committee and as chairman of the subcommittee that drafted the Church Committee’s final report on domestic intelligence activities, and, as Vice President, was instrumental to the enactment of FISA — the Article analyzes the ways in which the post-9/11 Act and court are at odds with their original design. The Article concludes that such overreach is possible in part because of structural changes to the FISA Court and the executive branch’s invocation of the need for secrecy in non-FISA Court proceedings. The recently enacted FREEDOM Act addresses some “liberty” concerns but fails to fix the structural issues that currently limit the authority and efficacy of the FISA Court. The FISA Court no longer serves its intended function as a specialized Article III court of limited jurisdiction. Rather, the FISA Court is more akin to an adjunct to the executive branch, lending legitimacy to intelligence operations without practically limiting executive authority. This Article concludes by recommending tangible actions Congress can and should take to reestablish the structures and processes recommended by the Church Committee — structures and processes that limit executive authority and comport with Article III of the United States Constitution

The relation between the frequency distributions of sieve diameters and fall velocities of sediment particles

A relation between the frequency distributions of sieve diameters and fall velocities is developed. The relation shows that if the sieve diameters of a sediment are log-normally distributed, the fall velocities will also have this distribution, but with a different standard deviation which can be calculated. The results of detailed measurements of the fall velocities of two different natural sands are presented, and the distributions of fall velocities are found to be in good agreement with the predicted distributions. The sedimentation diameters determined from the measured fall velocities agree very well with those predicted from the sieve diameters by the Inter-Agency Committee on Water Resources [1957]

Legalizing Merger to Monopoly and Higher Prices: The Canadian Competition Tribunal Gets It Wrong

This article analyzes the Canadian Superior Propane decision, apparently the first merger decision in world history to consider explicitly what to do when a merger was predicted to lead to both higher consumer prices and to net efficiencies. The article advocates analyzing the merger under a price to consumers or consumer welfare standard, rather than a total efficiency standard, and advocates that the enforcers and the courts block such mergers

Sub-Alfvenic Non-Ideal MHD Turbulence Simulations with Ambipolar Diffusion: I. Turbulence Statistics

Most numerical investigations on the role of magnetic fields in turbulent molecular clouds (MCs) are based on ideal magneto-hydrodynamics (MHD). However, MCs are weakly ionized, so that the time scale required for the magnetic field to diffuse through the neutral component of the plasma by ambipolar diffusion (AD) can be comparable to the dynamical time scale. We have performed a series of 256^3 and 512^3 simulations on supersonic but sub-Alfvenic turbulent systems with AD using the Heavy-Ion Approximation developed in Li, McKee, & Klein (2006). Our calculations are based on the assumption that the number of ions is conserved, but we show that these results approximately apply to the case of time-dependent ionization in molecular clouds as well. Convergence studies allow us to determine the optimal value of the ionization mass fraction when using the heavy-ion approximation for low Mach number, sub-Alfvenic turbulent systems. We find that ambipolar diffusion steepens the velocity and magnetic power spectra compared to the ideal MHD case. Changes in the density PDF, total magnetic energy, and ionization fraction are determined as a function of the AD Reynolds number. The power spectra for the neutral gas properties of a strongly magnetized medium with a low AD Reynolds number are similar to those for a weakly magnetized medium; in particular, the power spectrum of the neutral velocity is close to that for Burgers turbulence.Comment: 37 pages, 11 figures, 4 table

Piezoelectric Rotary Tube Motor

A custom rotary SQUIGGLE(Registered TradeMark) motor has been developed that sets new benchmarks for small motor size, high position resolution, and high torque without gear reduction. Its capabilities cannot be achieved with conventional electromagnetic motors. It consists of piezoelectric plates mounted on a square flexible tube. The plates are actuated via voltage waveforms 90 out of phase at the resonant frequency of the device to create rotary motion. The motors were incorporated into a two-axis postioner that was designed for fiber-fed spectroscopy for ground-based and space-based projects. The positioner enables large-scale celestial object surveys to take place in a practical amount of time

Free-to-roll tests of X-31 and F-18 subscale models with correlation to flight test results

This presentation will concentrate on a series of low-speed wind tunnel tests conducted on a 2.5 percent subscale F-18 model and a 2 percent subscale X-31 model. The model's control surfaces were unaugmented; and for the most part, were deflected at a constant angle throughout the tests. The tests consisted mostly of free-to-roll experiments conducted with the use of an air-bearing, surface pressure measurements, off-surface flow visualization, and force-balance tests. Where possible the results of the subscale tests have been compared to flight test data, or to other wind tunnel data taken at higher Reynolds numbers

Fluctuations and defect-defect correlations in the ordering kinetics of the O(2) model

The theory of phase ordering kinetics for the O(2) model using the gaussian auxiliary field approach is reexamined from two points of view. The effects of fluctuations about the ordering field are included and we organize the theory such that the auxiliary field correlation function is analytic in the short-scaled distance (x) expansion. These two points are connected and we find in the refined theory that the divergence at the origin in the defect-defect correlation function $\tilde{g}(x)$ obtained in the original theory is removed. Modifications to the order-parameter autocorrelation exponent $\lambda$ are computed.Comment: 29 pages, REVTeX, to be published in Phys. Rev. E. Minor grammatical/syntax changes from the origina

SN 2005hj: Evidence for Two Classes of Normal-Bright SNe Ia and Implications for Cosmology

HET Optical spectra covering the evolution from about 6 days before to about 5 weeks after maximum light and the ROTSE-IIIb unfiltered light curve of the "Branch-normal" Type Ia Supernova SN 2005hj are presented. The host galaxy shows HII region lines at redshift of z=0.0574, which puts the peak unfiltered absolute magnitude at a somewhat over-luminous -19.6. The spectra show weak and narrow SiII lines, and for a period of at least 10 days beginning around maximum light these profiles do not change in width or depth and they indicate a constant expansion velocity of ~10,600 km/s. We analyzed the observations based on detailed radiation dynamical models in the literature. Whereas delayed detonation and deflagration models have been used to explain the majority of SNe Ia, they do not predict a long velocity plateau in the SiII minimum with an unvarying line profile. Pulsating delayed detonations and merger scenarios form shell-like density structures with properties mostly related to the mass of the shell, M_shell, and we discuss how these models may explain the observed SiII line evolution; however, these models are based on spherical calculations and other possibilities may exist. SN 2005hj is consistent with respect to the onset, duration, and velocity of the plateau, the peak luminosity and, within the uncertainties, with the intrinsic colors for models with M_shell=0.2 M_sun. Our analysis suggests a distinct class of events hidden within the Branch-normal SNe Ia. If the predicted relations between observables are confirmed, they may provide a way to separate these two groups. We discuss the implications of two distinct progenitor classes on cosmological studies employing SNe Ia, including possible differences in the peak luminosity to light curve width relation.Comment: ApJ accepted, 31 page