5,225 research outputs found
A superior edge preserving filter with a systematic analysis
A new, adaptive, edge preserving filter for use in image processing is presented. It had superior performance when compared to other filters. Termed the contiguous K-average, it aggregates pixels by examining all pixels contiguous to an existing cluster and adding the pixel closest to the mean of the existing cluster. The process is iterated until K pixels were accumulated. Rather than simply compare the visual results of processing with this operator to other filters, some approaches were developed which allow quantitative evaluation of how well and filter performs. Particular attention is given to the standard deviation of noise within a feature and the stability of imagery under iterative processing. Demonstrations illustrate the performance of several filters to discriminate against noise and retain edges, the effect of filtering as a preprocessing step, and the utility of the contiguous K-average filter when used with remote sensing data
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A Shift in Louisiana Salt Marsh Microbial Communities Reflecting Changes in Salinity and Biogeochemical Parameters
The relationship between microbial communities, salinity, soil depth, and time was evaluated using phospholipid fatty acids (PLFA) collected from coastal wetlands in Louisiana post hurricanes Katrina and Rita. The three marsh types studied included freshwater and intermediate marshes from the Jean Lafitte Preserve as well as two brackish marsh sites from the Caernarvon Basin. The Caernarvon Basin was heavily impacted from the hurricanes leaving the lower sites sampled remnant marsh. The goal of this study was to examine microbial community changes along a salinity gradient to further understand the impact of salinity on the wetland ecosystem. This was done using multivariate comparison analysis (CCA) in combination with descriptive analysis comparing water chemistry (pH, DOC, TDN, NO2-, NO3-, Cl-, and SO43-) to PLFA data. This study finds a noticeable impact of salinity on PLFA as seen in an increased ratio of saturated to unsaturated PLFA as well as an increase the amount of cyclopropane PLFA in areas with a higher chloride content. The lower Caernarvon sites through exposure to the Caernarvon freshwater diversion and the recent hurricanes had salinity levels much closer to the intermediate marsh and proved to be an outlier on all findings. These findings mean that the microbial community is dynamic changing with season, depth, and salinity
Project Slope - Analysis of the performance of the lunar orbiter 1 and 2 imaging systems Final report
Lunar Orbiter 1 and 2 imaging system evaluation based on reconstructed photograph qualit
Project SLOPE - Study of Lunar Orbiter Photographic Evaluation Final report
Quantitative measurement methods for evaluating ability of Lunar Orbiter photographs to detect topographic feature
GPU ACCELERATION OF THE ISO–7 NUCLEAR REACTION NETWORK USING OPENCL
We looked at the potential performance increases available through OpenCL and its parallel computing capabilities, including GPU computing as it applies to time inte- gration of nuclear reaction networks. The particular method chosen in this work was the trapezoidal BDF-2 method using Picard iteration, which is a non-linear second order method. Nuclear reaction network integration by itself is a sequential process and not easily accelerated via parallel computation. However, in tackling a problem like modeling supernova dynamics, a spatial discretization of the volume of the star necessary, and in many cases is combined with the computational technique of oper- ator splitting. Every spatial cell would have its own reaction network independent of the others, which is where the parallel computation would prove useful. The partic- ular reaction network analyzed is called the iso–7 reaction network that looks at the dynamics of 7 of the more dominant nuclides in supernovae. The computational per- formance was compared between the CPU and the GPU, in which the GPU showed performance increases of up to 8 times. This increase was realized on the small–scale, because the computations were limited to running on a single device at any given time. However, these performance gains would only increase as the problem size was scaled up to the large–scale
Affordability Approaches for Human Space Exploration
The design and development of historical NASA Programs (Apollo, Shuttle and International Space Station), have been based on pre-agreed missions which included specific pre-defined destinations (e.g., the Moon and low Earth orbit). Due to more constrained budget profiles, and the desire to have a more flexible architecture for Mission capture as it is affordable, NASA is working toward a set of Programs that are capability based, rather than mission and/or destination specific. This means designing for a performance capability that can be applied to a specific human exploration mission/destination later (sometime years later). This approach does support developing systems to flatter budgets over time, however, it also poses the challenge of how to accomplish this effectively while maintaining a trained workforce, extensive manufacturing, test and launch facilities, and ensuring mission success ranging from Low Earth Orbit to asteroid destinations. NASA Marshall Space Flight Center (MSFC) in support of Exploration Systems Directorate (ESD) in Washington, DC has been developing approaches to track affordability across multiple Programs. The first step is to ensure a common definition of affordability: the discipline to bear cost in meeting a budget with margin over the life of the program. The second step is to infuse responsibility and accountability for affordability into all levels of the implementing organization since affordability is no single person s job; it is everyone s job. The third step is to use existing data to identify common affordability elements organized by configuration (vehicle/facility), cost, schedule, and risk. The fourth step is to analyze and trend this affordability data using an affordability dashboard to provide status, measures, and trends for ESD and Program level of affordability tracking. This paper will provide examples of how regular application of this approach supports affordable and therefore sustainable human space exploration architecture
Cargo-Positioning System for Next-Generation Spacecraft
A report discusses a proposed system for mounting loaded pallets in the cargo bay of a next-generation space-shuttle-like spacecraft, such that the center of mass of the cargo would lie within a 1-in. (2.54-cm) cube that would also contain the center of mass of the spacecraft. The system would include (1) an algorithm for planning the locations of the pallets, given the geometric and weight properties of the pallets, and the geometric restrictions of the cargo bay; (2) quick-connect/quick-disconnect mounting mechanisms similar to those now used on air hoses; (3) other mounting mechanisms, comprising mostly spring-loaded pins, in a locking subsystem that would prevent shifting of the pallets under load; and (4) mechanisms for performing fine position adjustments to satisfy the center-of-mass requirement. The position- adjusting mechanisms would be motor-driven lead-screw mechanisms in groups of three - one for positioning each pin of the locking subsystem along each of three mutually perpendicular coordinate axes. The system also would include a triple-threaded screw that would provide compensation for thermal expansion or contraction of the spacecraft
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