Satellite versus ground-based estimates of burned area: a comparison between MODIS based burned area and fire agency reports over North America in 2007

North American wildfire management teams routinely assess burned area on site during firefighting campaigns; meanwhile, satellite observations provide systematic and global burned-area data. Here we compare satellite and ground-based daily burned area for wildfire events for selected large fires across North America in 2007 on daily timescales. In a sample of 26 fires across North America, we found the Global Fire Emissions Database Version 4 (GFED4) estimated about 80% of the burned area logged in ground-based Incident Status Summary (ICS-209) over 8-day analysis windows. Linear regression analysis found a slope between GFED and ICS-209 of 0.67 (with R = 0.96). The agreement between these data sets was found to degrade at short timescales (from R = 0.81 for 4-day to R = 0.55 for 2-day). Furthermore, during large burning days (> 3000 ha) GFED4 typically estimates half of the burned area logged in the ICS-209 estimates

Variable mixer propulsion cycle

A design technique, method and apparatus are delineated for controlling the bypass gas stream pressure and varying the bypass ratio of a mixed flow gas turbine engine in order to achieve improved performance. The disclosed embodiments each include a mixing device for combining the core and bypass gas streams. The variable area mixing device permits the static pressures of the core and bypass streams to be balanced prior to mixing at widely varying bypass stream pressure levels. The mixed flow gas turbine engine therefore operates efficiently over a wide range of bypass ratios and the dynamic pressure of the bypass stream is maintained at a level which will keep the engine inlet airflow matched to an optimum design level throughout a wide range of engine thrust settings

Reduction of Ion Heating During Magnetic Reconnection by Large-Scale Effective Potentials

The physical processes that control the partition of released magnetic energy between electrons and ions during reconnection is explored through particle-in-cell simulations and analytical techniques. We demonstrate that the development of a large-scale parallel electric field and its associated potential controls the relative heating of electrons and ions. The potential develops to restrain heated exhaust electrons and enhances their heating by confining electrons in the region where magnetic energy is released. Simultaneously the potential slows ions entering the exhaust below the Alfv\'enic speed expected from the traditional counterstreaming picture of ion heating. Unexpectedly, the magnitude of the potential and therefore the relative partition of energy between electrons and ions is not a constant but rather depends on the upstream parameters and specifically the upstream electron normalized temperature (electron beta). These findings suggest that the fraction of magnetic energy converted into the total thermal energy may be independent of upstream parameters

Effect of parallel magnetic field on the Zero Differential Resistance State

The non-linear zero-differential resistance state (ZDRS) that occurs for highly mobile two-dimensional electron systems in response to a dc bias in the presence of a strong magnetic field applied perpendicular to the electron plane is suppressed and disappears gradually as the magnetic field is tilted away from the perpendicular at fixed filling factor $\nu$. Good agreement is found with a model that considers the effect of the Zeeman splitting of Landau levels enhanced by the in-plane component of the magnetic field.Comment: 4 pages, 4 figure

Transformation of an urban river's edge

Thesis (M. Arch.)--Massachusetts Institute of Technology, Dept. of Architecture, 1998.Includes bibliographical references (p. 107-112).I grew up in Philadelphia. The waterfront and its urban character motivated my original focus combined with architectural interests in dealing with public spaces. The search began for a site which was a locus of intensity and contained elements of time, sense of place, the character of the city and a particular relationship with the waterfront. Venice Island, located in the Schuylkill River at Manayunk, a Northwest neighborhood, was chosen due to its intimate scale, localized community and richness of natural and manmade environment. The equal strength of the context pushed the thesis to explore the transformation of the site using the influence of these existing forces. The site contains physical boundaries that include river, island, canal, and Main Street. These suggest threshold and propose a journey or passage to connect the Main Street to the river. Thus the importance of memory and identity to the formation of place combined with that of a journey incorporates existing remains on the island and interventions that intensify the experience. By introducing aspects of the city to the island and further connections to the river, I propose it is a place for people to learn about the environment as an integration of existing forces through the physical forms and sense of place generated by the transformation. The thesis is organized into three parts, which follows the development of the exploration, the first being the urban waterfront and examining ideas relating to public space, inhabiting the edge and the important of the River. The second part outlines the early ideas and study of the site and the city and issues of built and natural environment and design approach. The final section documents the design and transformation of the site related to landscape experience, journey and the urban rivers edge.by Eileen T. McHugh.M.Arch