Adaptive and mobile ground sensor array.

The goal of this LDRD was to demonstrate the use of robotic vehicles for deploying and autonomously reconfiguring seismic and acoustic sensor arrays with high (centimeter) accuracy to obtain enhancement of our capability to locate and characterize remote targets. The capability to accurately place sensors and then retrieve and reconfigure them allows sensors to be placed in phased arrays in an initial monitoring configuration and then to be reconfigured in an array tuned to the specific frequencies and directions of the selected target. This report reviews the findings and accomplishments achieved during this three-year project. This project successfully demonstrated autonomous deployment and retrieval of a payload package with an accuracy of a few centimeters using differential global positioning system (GPS) signals. It developed an autonomous, multisensor, temporally aligned, radio-frequency communication and signal processing capability, and an array optimization algorithm, which was implemented on a digital signal processor (DSP). Additionally, the project converted the existing single-threaded, monolithic robotic vehicle control code into a multi-threaded, modular control architecture that enhances the reuse of control code in future projects

Performance evaluation of NUMA and COMA distributed shared-memory multiprocessors

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references.Issued also on microfiche from Lange Micrographics.Memory architecture is an important component in a distributed shared-memory parallel computer. This thesis studies three shared-memory architectures-Non-Uniform Memory Access (NUMA) with full-mapped directories, Cache-Only Memory Architecture (COMA) with full-mapped directories, and COMA with directories based on a new design using binomial trees. The three architectures were implemented in the Proteus execution driven simulator. Proteus simulated the execution of three applications taken from the SPLASH-2 suite of benchmark parallel programs. Six sets of simulations were run. These simulations provided performance data for a range of values of important design parameters. The parameters studied were page size, block size, number of processors, memory controller speed, cache size and interconnection network topology. These simulations have two major benefits. First, they aid in choosing the best values for key design parameters. Second, these simulations facilitate the direct comparison of COMA vs. NUMA as well as the two directory designs. The simulations show that both COMA architectures generally perform better than NUMA. COMA proved to be less sensitive to suboptimum choices of primary cache and block sizes. In most cases the COMA with full-mapped directories performed a little better than with binomial trees. However, the binomial tree directories require significantly less hardware (eleven versus sixty-four bite per block for the machines simulated in this thesis)

A novel polar format algorithm for SAR images utilizing post azimuth transform interpolation.

SAR phase history data represents a polar array in the Fourier space of a scene being imaged. Polar Format processing is about reformatting the collected SAR data to a Cartesian data location array for efficient processing and image formation. In a real-time system, this reformatting or ''re-gridding'' operation is the most processing intensive, consuming the majority of the processing time; it also is a source of error in the final image. Therefore, any effort to reduce processing time while not degrading image quality is valued. What is proposed in this document is a new way of implementing real-time polar-format processing through a variation on the traditional interpolation/2-D Fast Fourier Transform (FFT) algorithm. The proposed change is based upon the frequency scaling property of the Fourier Transform, which allows a post azimuth FFT interpolation. A post azimuth processing interpolation provides overall benefits to image quality and potentially more efficient implementation of the polar format image formation process