Advanced expander test bed program

The Advanced Expander Test Bed (AETB) is a key element in NASA's Chemical Transfer Propulsion Program for development and demonstration of expander cycle oxygen/hydrogen engine technology component technology for the next space engine. The AETB will be used to validate the high-pressure expander cycle concept, investigate system interactions, and conduct investigations of advanced missions focused components and new health monitoring techniques. The split-expander cycle AETB will operate at combustion chamber pressures up to 1200 psia with propellant flow rates equivalent to 20,000 lbf vacuum thrust

Cl electrosorption on Ag(100): Lateral interactions and electrosorption valency from comparison of Monte Carlo simulations with chronocoulometry experiments

We present Monte Carlo Simulations using an equilibrium lattice-gas model for the electrosorption of Cl on Ag(100) single-crystal surfaces. Fitting the simulated isotherms to chronocoulometry experiments, we extract parameters such as the electrosorption valency gamma and the next-nearest-neighbor lateral interaction energy phi_nnn. Both coverage-dependent and coverage independent gamma were previously studied assuming a constant phi_nnn [I. Abou Hamad, Th. Wandlowski, G. Brown, P.A. Rikvold, J. Electroanal. Chem. 554-555 (2003) 211]. Here, a self-consistent, entirely electrostatic picture of the lateral interactions with a coverage-dependent phi_nnn is developed, and a relationship between phi_nnn and gamma is investigated for Cl on Ag(100).Comment: Accepted for publication in Electrochimica Acta, 10 pages, 7 figures, 2 tables and an appendi

Identification of phenological stages and vegetative types for land use classification

There are no author-identified significant results in this report

Invariant manifolds and the geometry of front propagation in fluid flows

Recent theoretical and experimental work has demonstrated the existence of one-sided, invariant barriers to the propagation of reaction-diffusion fronts in quasi-two-dimensional periodically-driven fluid flows. These barriers were called burning invariant manifolds (BIMs). We provide a detailed theoretical analysis of BIMs, providing criteria for their existence, a classification of their stability, a formalization of their barrier property, and mechanisms by which the barriers can be circumvented. This analysis assumes the sharp front limit and negligible feedback of the front on the fluid velocity. A low-dimensional dynamical systems analysis provides the core of our results.Comment: 14 pages, 11 figures. To appear in Chaos Focus Issue: Chemo-Hydrodynamic Patterns and Instabilities (2012

Opportunities and barriers faced by early-career civil engineers enacting global responsibility

The term ‘global responsibility’ projects a holistic sense of ethics, sustainability, and obligation. To achieve the long-term viability of human life on Earth, civil engineering must be conducted in increasingly responsible ways, and civil engineers must value and enact global responsibility in their work. Interviews conducted with nine civil engineers in London provide insight regarding engineers’ familiarity with the term, how they learned about it, what opportunities and barriers they face, and what might be done by professional and educational institutions to help them practice more responsibly. Results indicate: the term itself is novel but underlying concepts are not; continuing professional development has played a crucial role in their understanding; material selection and Health & Safety represent primary avenues for contributing responsibly at work. This paper provides advice to professional institutions regarding transparencies, procedures, and metrics to enhance the UK workplace and ideas for educational institutions preparing engineering students for practice

Testing Hawking particle creation by black holes through correlation measurements

Hawking's prediction of thermal radiation by black holes has been shown by Unruh to be expected also in condensed matter systems. We show here that in a black hole-like configuration realised in a BEC this particle creation does indeed take place and can be unambiguously identified via a characteristic pattern in the density-density correlations. This opens the concrete possibility of the experimental verification of this effect.Comment: 13 pages, 2 figures. Honorable mention in the 2010 GRF Essay Competitio

Defining Medical Futility in Ethics, Law and Clinical Practice: An Exercise in Futility?

The debate as to the meaning of medical futility and what physicians should do in clinical practice dates back to the time of the writings of Hippocrates and Plato where it was said, "To attempt futile treatment is to display an ignorance that is allied to madness". In simpler times assertions regarding the obvious were sufficient to indicate what was thought "fitting" as a medical practitioner. In recent times, however, modern technology, professional values and power, patient autonomy, limited health care resources and societal expectations, make for a much more potent and potentially explosive mixture. In this article we argue that futility is a problem that will not go away, both because of increased health expectations and emerging technologies that keep making possible what was previously impossible. The problem of definition and its ramifications in terms of institutional policies is one in which the legal profession and its process (which often represents and reflects societal values) has a key role to play by way of critical reflection and appraisal

Material studies related to lunar surface exploration. Volume 4 - Preliminary studies for the design of engineering probes Final report, 6 Mar. 1967 - 30 Jun. 1968

Preliminary design of engineering probes for studying lunar surface material propertie

Material studies related to lunar surface exploration, volume 3 Final report, 6 Mar. 1967 - 30 Jun. 1968

Mechanical properties of lunar soils related to lunar exploratio