20,688 research outputs found
Structure and utilization of supersonic free jets in low density wind tunnels
Inviscid and slightly viscous flow in supersonic free jet core, and low density wind tunnel application
Relativistic models of the universe with pressure equal to zero and time-dependent uniformity
Zero density and approximate, relativistic models of univers
Preliminary study of a possible automatic landing system
Navigation and control laws for a possible automatic landing system have been investigated. The system makes use of data from an inertial table and either an airborne or ground radar to generate signals that guide the airplane to a landing. All landing maneuvers take place within a zone that extends 6000 m out from the touchdown point, 4000 m on each side of the runway center line, and 540 m high. The results show that the system can adequately control the airplane on steep, curved decelerating approaches to a landing that takes place with small errors from the desired landing point and desired airplane attitude. The system studied would interface well with the scanning beam microwave landing system (MLS). The use of this system with the MLS makes it possible to incorporate an independent landing monitor
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Examining the Relationships Among Categorization, Stereotype Activation, and Stereotype Application.
Increased category salience is associated with increased stereotyping. Prior research has not examined the processes that may account for this relationship. That is, it is unclear whether category salience leads to increased stereotyping by increasing stereotype activation (i.e., increased accessibility of stereotypic information), application (i.e., increasing the tendency to apply activated stereotypes), or both processes simultaneously. We examined this question across three studies by manipulating category salience in an implicit stereotyping measure and by applying a process model that provides independent estimates of stereotype activation and application. Our results replicated past findings that category salience increases stereotyping. Modeling results showed that category salience consistently increased the extent of stereotype application but increased stereotype activation in more limited contexts. Implications for models of social categorization and stereotyping are discussed
Mars digital terrain model
The Mars Digital Terrain Model (DTM) is the result of a new project to: (1) digitize the series of 1:2,000,000-scale topographic maps of Mars, which are being derived photogrammetically under a separate project, and (2) reformat the digital contour information into rasters of elevation that can be readily registered with the Digital Image Model (DIM) of Mars. Derivation of DTM's involves interpolation of elevation values into 1/64-degree resolution and transformation of them to a sinusoidal equal-area projection. Digital data are produced in blocks corresponding with the coordinates of the original 1:2,000,000-scale maps, i.e., the dimensions of each block in the equatorial belt are 22.5 deg of longitude and 15 deg of latitude. This DTM is not only compatible with the DIM, but it can also be registered with other data such as geologic units or gravity. It will be the most comprehensive record of topographic information yet compiled for the Martian surface. Once the DTM's are established, any enhancement of Mars topographic information made with updated data, such as data from the planned Mars Observer Mission, will be by mathematical transformation of the DTM's, eliminating the need for recompilation
Publication of topographic atlas and control network of Mars
To aid planetary studies and the planning of future Mars missions, the Topographic Atlas and Control Network for Mars will be submitted by the end of fiscal year 1992 for publication as a NASA Special Publication. It will consist of reduced versions of 108 1:2 million-scale photomosaics that show contour lines from topographic maps at the same scale, as well as precisely located control points. The control points are from the planetwide network, which is not only instrumental in the compilation of maps at various scales, but is also widely used in other research such as studies of Mars' gravity and atmosphere. An example, a combination of MC 8-NW and -SW, of the photomosaics to be included in the atlas is presented. Contour lines in the figure are at 1-km intervals. The final adjusted ground coordinates and elevations of the 77 control points shown are given in table form. The last column in the table lists the topographic datum (zero elevation) that can be used to compute the solid radius of the control point from the center of mass of Mars. The atlas will also include information such as the adjusted C-matrices of each image, descriptions of the methods used, and their accuracy, and guidelines for users
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