Digital Collaboration and Classroom Practice: Educator Use of ARIS Connect

A major focus of the booming education technology sector is on products that aim to help teachers improve classroom practice. For their part, districts must figure out which of these resources will be most useful to schools. In New York City, the Department of Education developed its own Achievement Reporting and Innovation System (ARIS), which was rolled out in 2008. ARIS was an early effort at a system-wide data and teacher collaboration platform, and a major undertaking for the nation's largest school district. In 2011, the Research Alliance received a grant from the Spencer Foundation to investigate how this ambitious initiative played out in schools. Our first report focused on overall use and perceptions of ARIS. In the current phase of our study, we honed our focus onto ARIS Connect -- a component designed specifically to help educators improve their practice by sharing resources, posting questions, and giving one another feedback, both within schools and across the district. Our investigation sought to understand what educators thought of Connect, and whether, as its designers intended, Connect supported their ability to communicate with other educators and improve classroom practice. The study is based on two years of "clickstream" data, which tracks user visits to and navigation through ARIS. We also visited nine middle schools that recorded higher-than-average use of Connect, where we interviewed administrators and held focus groups with teachers. This report presents our findings, including insights on why educators did or did not use Connect; what might have made Connect more useful; and what external tools educators use for similar purposes

Experimental and Analytical Study of Balanced-Diaphragm Fuel Distributors for Gas-Turbine Engines

A method of distributing fuel equally to a plurality of spray nozzles in a gas-turbine engine by means of balanced-diaphragm fuel distributors is presented. The experimental performance of three of eight possible distributor arrangements are discussed. An analysis of all eight arrangements is included. Criterions are given for choosing a fuel-distributor arrangement to meet specific fuel-system requirements of fuel-distribution accuracy, spray-nozzle pressure variations, and fuel-system pressures. Data obtained with a model of one distributor arrangement indicated a maximum deviation from perfect distribution of 3.3 percent for a 44 to 1 range (19.5 to 862 lb/hr) of fuel-flow rates. The maximum distributor pressure drop was 125 pounds per square inch. The method used to obtain the required wide range of flow control in the distributor valves consisted in varying the length of a constant-area flow path

What image features guide lightness perception?

Lightness constancy is the ability to perceive black and white surface colors under a wide range of lighting conditions. This fundamental visual ability is not well understood, and current theories differ greatly on what image features are important for lightness perception. Here we measured classification images for human observers and four models of lightness perception to determine which image regions influenced lightness judgments. The models were a high-pass-filter model, an oriented difference-of-Gaussians model, an anchoring model, and an atmospheric-link-function model. Human and model observers viewed three variants of the argyle illusion (Adelson, 1993) and judged which of two test patches appeared lighter. Classification images showed that human lightness judgments were based on local, anisotropic stimulus regions that were bounded by regions of uniform lighting. The atmospheric-link-function and anchoring models predicted the lightness illusion perceived by human observers, but the high-pass-filter and oriented-difference-of-Gaussians models did not. Furthermore, all four models produced classification images that were qualitatively different from those of human observers, meaning that the model lightness judgments were guided by different image regions than human lightness judgments. These experiments provide a new test of models of lightness perception, and show that human observers' lightness computations can be highly local, as in low-level models, and nevertheless depend strongly on lighting boundaries, as suggested by midlevel models.York University Librarie

The surface geometry of inherited joint and fracture trace patterns resulting from active and passive deformation

Hypothetical models are considered for detecting subsurface structure from the fracture or joint pattern, which may be influenced by the structure and propagated to the surface. Various patterns of an initially orthogonal fracture grid are modeled according to active and passive deformation mechanisms. In the active periclinal structure with a vertical axis, fracture frequency increased both over the dome and basin, and remained constant with decreasing depth to the structure. For passive periclinal features such as a reef or sand body, fracture frequency is determined by the arc of curvature and showed a reduction over the reefmound and increased over the basin

Magnetoresistance of a two-dimensional electron gas in a parallel magnetic field

The conductivity of a two-dimensional electron gas in a parallel magnetic field is calculated. We take into account the magnetic field induced spin-splitting, which changes the density of states, the Fermi momentum and the screening behavior of the electron gas. For impurity scattering we predict a positive magnetoresistance for low electron density and a negative magnetoresistance for high electron density. The theory is in qualitative agreement with recent experimental results found for Si inversion layers and Si quantum wells.Comment: 4 pages, figures included, PDF onl

Physical properties of the Apollo 12 lunar fines

Optical and radio frequency electrical properties and grain size analyses of Apollo 11 and 12 lunar soil sample

Droplet size and morphology characterization for diesel sprays under atmospheric operating conditions

The shape of microscopic fuel droplets may differ from the perfect sphere, affecting their external surface area and thus the heat transfer with the surrounding gas. Hence there is a need for the characterization of droplet shapes, and the estimation of external surface area, in order to enable the development of physically accurate mathematical models for the heating and evaporation of diesel fuel sprays. We present ongoing work to automat-ically identify and reconstruct the morphology of fuel droplets, primarily focusing in this study on irregularly-shaped, partially-deformed and oscillating droplets under atmospheric conditions. We used direct imaging tech-niques based on long-working distance microscopy and ultra-high-speed video to conduct a detailed temporal investigation of droplet morphology. We applied purpose-built algorithms to extract droplet size, velocity, vol-ume and external surface area from the microscopic ultra-high-speed video frames. High resolution images of oscillating droplets and a formation of a droplet form ligament, sphericity factors, volume as well as external surface area are presented for 500 bar injection pressure in the near nozzle region (up to 0.7 mm from nozzle exit) under atmospheric conditions. We observed a range of different liquid structures, including perfectly spher-ical, non-spherical droplets and stretched ligaments. We found that large droplets and ligaments exceeding the size of the nozzle hole could be found at the end of injection. In order to estimate droplet volume and external surface area from two-dimensional droplet information, a discrete revolution of the droplet silhouette about its major centroidal axis was used. Special attention was paid to the estimation of actual errors in the prediction of volume and surface characteristics from a droplet silhouette. In addition to the estimation of droplet volume and external surface area, the actual shape reconstruction in 3D coordinates from a droplet silhouette was performed in order to enable future numerical modelling studies of real droplets

Tales of the Olympic city: Memory, narrative and the built environment = Historias de la ciudad olímpica: memoria, narrativa y el entorno construido

The Olympics have a greater, more profound and more pervasive impact on the urban fabric of their host cities than any other sporting or cultural event. This paper is concerned with issues of memory and remembering in Olympic host cities. After a contextual introduction, it employs a case study of the Queen Elizabeth Olympic Park (QEOP), the main event space for the London 2012 Summer Games, to supply insight into how to read the urban traces of Olympic memory. Three key themes are identified when interpreting the memories associated with the Park and its built structures, namely: treatment of the area’s displaced past, memorializing the Games, and with memory legacy. The ensuing discussion section then adopts a historiographic slant, stressing the importance of narrative and offering wider conclusions about Olympic memory and the city. = El impacto de los Juegos Olímpicos en el tejido urbano de las ciudades anfitrionas es mayor, más profundo y más generalizado que el de cualquier otro evento deportivo o cultural. Este trabajo analiza temas relacionados con la memoria y el recuerdo en las ciudades anfitrionas de los Juegos Olímpicos. Tras introducir del contexto, se utiliza un estudio de caso del Parque Olímpico Queen Elizabeth (QEOP, por sus siglas en inglés), el principal espacio de los Juegos de Verano de Londres 2012, para plantear un nuevo enfoque sobre cómo leer las huellas urbanas de la memoria olímpica. Se identifican tres temas clave al interpretar los recuerdos asociados con el Parque y sus estructuras construidas, a saber: el tratamiento del pasado desplazado del área, la conmemoración de los Juegos y el legado de la memoria. La sección de discusión adopta un enfoque historiográfico, subrayando la importancia de la narrativa y ofreciendo gran variedad de conclusiones sobre la memoria olímpica y la ciudad