Influence of Water Depth on the Rate of Expansion of Giant Cutgrass Populations and Management Implications

Giant cutgrass ( Zizaniopsis miliacea (Michx.) Doell. & Asch.), a tall emergent grass native to the southeastern United States, was studied in Lake Seminole where it formed large expanding stands, and Lake Alice where it was confined to a stable narrow fringe

The Art of Community: Creativity at the Crossroads of Immigrant Cultures and Social Services

These are case studies that give credance to the belief that respect for one's own artistic traditions is critical to the acculturation process. The essays contained here offer clear and shining examples of how paying attention to culture and creativity can build self-confidence, nurture a productive and valuable citizenry, and even save a life. Through these stories, we begin to see that encouraging the practice of cultural traditions and participation in arts activities will help newcomers spread their wings and fly

La economía informal

Incluye BibliografíaEl objetivo de este trabajo es analizar de qué manera las actividades desarrolladas por las empresas informales interactúan con las estructuras sociales existentes y las prácticas y políticas de fiscalización de los Estados nacionales. Es a través de estas interacciones como se pone de manifiesto el carácter paradójico de la economía informal y se ilustran con mayor fuerza las conclusiones que se emplean para elaborar las teorías económicas y sociológicas del comportamiento del mercado. Tras analizar varias definiciones y enfoques de medición posibles, el trabajo centra la atención en estos factores dinámicos, focalizados en cuatro paradojas: los fundamentos sociales de la economía informal; la ambigüedad de las relaciones con las regulaciones del Estado; las dificultades para definirla; su funcionalidad en relación con las instituciones económicas y políticas que presuntamente socava

Technical Challenges to Systems Analysis and MDAO for Advanced Subsonic Transport Aircraft

No abstract availabl

La segunda generación en Madrid: un estudio longitudinal

La segunda generación de inmigrantes en España tiene modestas aspiraciones educativas y ocupacionales y no se siente aún española. En este ARI se sintetizan los resultados preliminares de la primera fase de un estudio longitudinal sobre la adaptación social y económica de los hijos de inmigrantes –la segunda generación– en España. La fase inicial del estudio consiste en una muestra estadísticamente representativa de estudiantes de segunda generación en colegios de las áreas metropolitanas de Madrid y Barcelona, incluyendo tanto colegios públicos como concertados. El documento incluye los resultados iniciales del estudio en Madrid

A Noise and Emissions Assessment of the N3-X Transport

Analytical predictions of certification noise and exhaust emissions for NASA's N3-X - a notional, hybrid wingbody airplane - are presented in this paper. The N3-X is a 300-passenger concept transport propelled by an array of fans distributed spanwise near the trailing edge of the wingbody. These fans are driven by electric motors deriving power from twin generators driven by turboshaft engines. Turboelectric distributed hybrid propulsion has the potential to dramatically increase the propulsive efficiency of aircraft. The noise and exhaust emission estimates presented here are generated using NASA's conceptual design systems analysis tools with several key modifications to accommodate this unconventional architecture. These tools predict certification noise and the emissions of oxides of nitrogen by leveraging data generated from a recent analysis of the N3-X propulsion system

An Assessment of NASA Aeropropulsion Technologies: A System Study

Aviation industry s robust growth rate has given rise to growing concerns about the contribution that aviation emissions will make to local air quality and global climate change. Over the last several years, NASA has been engaged in the development of aeropropulsion technologies with specific objectives to reduce aircraft emissions. A system analysis was performed to evaluate the potential impact of these propulsion technologies on aircraft CO2 (directly proportional to fuel burn) and NOx reductions. A large subsonic aircraft, with two 396-kN thrust (85,000-pound) engines was chosen for the study. Performance benefit estimates are presented for each technology, with a summary of potential emissions reduction possible from the development of these technologies. The results show that NASA s aeropropulsion technologies have the potential to significantly reduce the CO2 and NO(x) emissions. The results are used to support informed decision-making on the development of aeropropulsion technology portfolio for CO2 and NO(x) reductions

Thermometry in high pressure gases using spontaneous Raman scattering

Spontaneous Raman scattering from nitrogen is studied in high pressure gases. Collision frequency increases with increasing gas density, causing spectral lines to broaden due to pressure broadening and mix when the lines are strongly overlapped. Because spontaneous Raman thermometry is accomplished by fitting a simulated spectrum to an experimental spectrum, spectral models that neglect these collision-induced effects will lead to erroneous temperature inference. This work investigates the influence of high density on ro-vibrational spontaneous Raman scattering, which must be understood to obtain accurate thermometry in high pressure gases. The temperature profile through a flame front was measured at 1 atm, 3 atm, and 5 atm using spontaneous Raman scattering from nitrogen. The pressure broadening was measured for the anisotropic tensor component of spontaneous Raman scattering from room temperature nitrogen over the pressure range of 10 atm to 70 atm for three gas compositions: pure nitrogen, air, and nitrogen in argon. The unmixed line model was found to give good fits to the O and S branches for all pressures, which indicates that line mixing effects are not significant in the O and S branches over this pressure range. Using indirect experimental evidence, line mixing effects in the anisotropic component of the Q branch were inferred to be below the threshold set by the experimental spectral resolution at pressures up to 70 atm at room temperature. Assuming that the anisotropic Q branch lines mix like the isotropic lines was found to result in a small systematic error in the inferred temperature at flame temperatures, with the error increasing slowly with pressure. The bias can be removed by modeling the anisotropic spectrum separately from the isotropic spectrum. Line mixing effects should be included in the modeling of the isotropic component of the Raman spectrum, but can probably be neglected in the anisotropic component of the ro-vibrational spontaneous Raman spectrum of nitrogen.Aerospace Engineerin

Adaptive Engine Technologies for Aviation CO2 Emissions Reduction

Adaptive turbine engine technologies are assessed for their potential to reduce carbon dioxide emissions from commercial air transports.Technologies including inlet, fan, and compressor flow control, compressor stall control, blade clearance control, combustion control, active bearings and enabling technologies such as active materials and wireless sensors are discussed. The method of systems assessment is described, including strengths and weaknesses of the approach. Performance benefit estimates are presented for each technology, with a summary of potential emissions reduction possible from the development of new, adaptively controlled engine components