LOX/Hydrocarbon Combustion Instability Investigation

The LOX/Hydrocarbon Combustion Instability Investigation Program was structured to determine if the use of light hydrocarbon combustion fuels with liquid oxygen (LOX) produces combustion performance and stability behavior similar to the LOX/hydrogen propellant combination. In particular methane was investigated to determine if that fuel can be rated for combustion instability using the same techniques as previously used for LOX/hydrogen. These techniques included fuel temperature ramping and stability bomb tests. The hot fire program probed the combustion behavior of methane from ambient to subambient temperatures. Very interesting results were obtained from this program that have potential importance to future LOX/methane development programs. A very thorough and carefully reasoned documentation of the experimental data obtained is contained. The hot fire test logic and the associated tests are discussed. Subscale performance and stability rating testing was accomplished using 40,000 lb. thrust class hardware. Stability rating tests used both bombs and fuel temperature ramping techniques. The test program was successful in generating data for the evaluation of the methane stability characteristics relative to hydrogen and to anchor stability models. Data correlations, performance analysis, stability analyses, and key stability margin enhancement parameters are discussed

A Measurement System Experiment to Evaluate the Nosing-to-nosing Method for Measuring Dimensions of Steps

Non-uniformity of steps within a flight is a major risk factor for falls. Guidelines and requirements for uniformity of step risers and tread depths assume the measurement system provides precise dimensional values. The state-of-the-art measurement system is a relatively new method, known as the nosing-to-nosing method. It involves measuring the distance between the noses of adjacent steps and the angle formed with the horizontal. From these measurements, the effective riser height and tread depth are calculated. This study was undertaken for the purpose of evaluating the measurement system to determine how much of total measurement variability comes from the step variations versus that due to repeatability and reproducibility (R&R) associated with the measurers. Using an experimental design quality control professionals call a measurement system experiment, two measurers measured all steps in six randomly selected flights, and repeated the process on a subsequent day. After marking each step in a flight in three lateral places (left, center, and right), the measurers took their measurement. This process yielded 774 values of riser height and 672 values of tread depth. Results of applying the Gage R&R ANOVA procedure in Minitab software indicated that the R&R contribution to riser height variability was 1.42%; and to tread depth was 0.50%. All remaining variability was attributed to actual step-to-step differences. These results may be compared with guidelines used in the automobile industry for measurement systems that consider R&R less than 1% as an acceptable measurement system; and R&R between 1% and 9% as acceptable depending on the application, the cost of the measuring device, cost of repair, or other factors

Three-body structure of low-lying 12Be states

We investigate to what extent a description of 12Be as a three-body system made of an inert 10Be-core and two neutrons is able to reproduce the experimental 12Be data. Three-body wave functions are obtained with the hyperspherical adiabatic expansion method. We study the discrete spectrum of 12Be, the structure of the different states, the predominant transition strengths, and the continuum energy spectrum after high energy fragmentation on a light target. Two 0+, one 2+, one 1- and one 0- bound states are found where the first four are known experimentally whereas the 0- is predicted as an isomeric state. An effective neutron charge, reproducing the measured B(E1) transition and the charge rms radius in 11Be, leads to a computed B(E1) transition strength for 12Be in agreement with the experimental value. For the E0 and E2 transitions the contributions from core excitations could be more significant. The experimental 10Be-neutron continuum energy spectrum is also well reproduced except in the energy region corresponding to the 3/2- resonance in 11Be where core excitations contribute.Comment: 16 pages, 9 figures. Accepted for publication in Physical Review

Plane-wave impulse approximation extraction of the neutron magnetic form factor from quasielastic ^3He(e,e') at Q^2=0.3 to 0.6 (GeV/c)^2

A high precision measurement of the transverse spin-dependent asymmetry A_T' in ^3He(e,e') quasielastic scattering was performed in Hall A at Jefferson Lab at values of the squared four-momentum transfer, Q^2, between 0.1 and 0.6 (GeV/c)^2. A_(T') is sensitive to the neutron magnetic form factor, G_M^n . Values of G_M^n at Q^2 = 0.1 and 0.2 (GeV/c)^2, extracted using Faddeev calculations, were reported previously. Here, we report the extraction of G_M^n for the remaining Q^2 values in the range from 0.3 to 0.6 (GeV/c)^2 using a plane-wave impulse approximation calculation. The results are in good agreement with recent precision data from experiments using a deuterium target

On the definition of Quantum Free Particle on Curved Manifolds

A selfconsistent definition of quantum free particle on a generic curved manifold emerges naturally by restricting the dynamics to submanifolds of co-dimension one. PACS 0365 0240Comment: 8 p., phyzzx macropackag

Reconsidering "the love of art" : evaluating the potential of art museum outreach

Art museums have long been identified as bastions of social and cultural exclusion. This conclusion was best evidenced by the large-scale 1967 French study by Bourdieu and Darbel demonstrating the exclusionary nature of “The Love of Art.” However, in recent years there have been increasing efforts to reach out to a broader range of visitors beyond conventional audiences. The present study investigates the impacts of an outreach program at a UK art museum, which sought to engage socially excluded young mothers. This study employs ethnographic research methods on a longitudinal basis to develop qualitative insights about the program seeking to mitigate cultural exclusion. While the study’s findings uphold many longstanding critiques of art museums’ conventional approaches, the study also indicates that carefully designed outreach activities can overcome such limitations and enhance cultural engagement. Thus, art museums’ limited appeal is tied to problematic public engagement practices that can be changed

Honeycomb lattice polygons and walks as a test of series analysis techniques

We have calculated long series expansions for self-avoiding walks and polygons on the honeycomb lattice, including series for metric properties such as mean-squared radius of gyration as well as series for moments of the area-distribution for polygons. Analysis of the series yields accurate estimates for the connective constant, critical exponents and amplitudes of honeycomb self-avoiding walks and polygons. The results from the numerical analysis agree to a high degree of accuracy with theoretical predictions for these quantities.Comment: 16 pages, 9 figures, jpconf style files. Presented at the conference "Counting Complexity: An international workshop on statistical mechanics and combinatorics." In celebration of Prof. Tony Guttmann's 60th birthda

Hall noise and transverse freezing in driven vortex lattices

We study driven vortices lattices in superconducting thin films. Above the critical force $F_c$ we find two dynamical phase transitions at $F_p$ and $F_t$, which could be observed in simultaneous noise measurements of the longitudinal and the Hall voltage. At $F_p$ there is a transition from plastic flow to smectic flow where the voltage noise is isotropic (Hall noise = longitudinal noise) and there is a peak in the differential resistance. At $F_t$ there is a sharp transition to a frozen transverse solid where the Hall noise falls down abruptly and vortex motion is localized in the transverse direction.Comment: 4 pages, 3 figure

Precision Measurement of the Spin-Dependent Asymmetry in the Threshold Region of ^3He(e, e')

We present the first precision measurement of the spin-dependent asymmetry in the threshold region of ^3He(e,e′) at Q^2 values of 0.1 and 0.2(GeV/c)^2. The agreement between the data and nonrelativistic Faddeev calculations which include both final-state interactions and meson-exchange current effects is very good at Q^2 = 0.1(GeV/c)^2, while a small discrepancy at Q^2 = 0.2(GeV/c)^2 is observed

Q^2 Evolution of the Generalized Gerasimov-Drell-Hearn Integral for the Neutron using a ^3He Target

We present data on the inclusive scattering of polarized electrons from a polarized ^3He target at energies from 0.862 to 5.06 GeV, obtained at a scattering angle of 15.5°. Our data include measurements from the quasielastic peak, through the nucleon resonance region, and beyond, and were used to determine the virtual photon cross-section difference σ_(1/2)-σ_(3/2). We extract the extended Gerasimov-Drell-Hearn integral for the neutron in the range of four-momentum transfer squared Q^2 of 0.1–0.9   GeV^2