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Articles 1 - 21 of 21
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A Bayesian Perspective On Estimating Mean, Variance, And Standard-Deviation From Data, Travis E. Oliphant
A Bayesian Perspective On Estimating Mean, Variance, And Standard-Deviation From Data, Travis E. Oliphant
Faculty Publications
This article shows how to compute confidence intervals for mean, standard-deviation, and variance using Bayesian methods. The method is implemented in SciPy as scipy.stats.bayes_mvs After reviewing some classical estimators for mean, variance, and standard-deviation and showing that un-biased estimates are not usually desirable, a Bayesian perspective is employed to determine what is known about mean, variance, and standard deviation given only that a data set in-fact has a common mean and variance. Maximum-entropy is used to argue that the likelihood function in this situation should be the same as if the data were independent and identically distributed Gaussian. A non-informative …
Predicting On-Orbit Static Single Event Upset Rates In Xilinx Virtex Fpgas, Joshua Engel, Keith S. Morgan, Michael J. Wirthlin, Paul S. Graham
Predicting On-Orbit Static Single Event Upset Rates In Xilinx Virtex Fpgas, Joshua Engel, Keith S. Morgan, Michael J. Wirthlin, Paul S. Graham
Faculty Publications
Sponsorship: Department of Energy, Los Alamos National Laboratory. This document describes the methodology used to predict single-event upset rates for Xilinx Virtex FPGAs based on the CREME96 orbit modeling tool. Using this methodology, SEU upset rates are obtained for several Xilinx Virtex FPGAs including Virtex, Virtex-II, and Virtex-4. Further, SEU upset rates are obtained for a variety of orbits for each of these FPGAs.
Time-Varying Mimo Channels: Measurement, Analysis, And Modeling, Michael A. Jensen, Jon W. Wallace
Time-Varying Mimo Channels: Measurement, Analysis, And Modeling, Michael A. Jensen, Jon W. Wallace
Faculty Publications
communication nodes is analyzed. A wide-band 8 times 8 sounder is employed to measure the response of indoor and outdoor channels at 2.55 and 5.2 GHz. The rate of channel temporal variation is then quantified in terms of information theoretic metrics that indicate the loss in channel quality as transmit and receive channel state information becomes increasingly outdated. Finally, these metrics are used to investigate the ability of two different modeling strategies-a random matrix model and a physical time-varying cluster model-to capture the channel temporal variation.
Anisotropic High Aspect Ratio Etch Development For Fluorinated Polymers With Stress Relief Technique, S. Kim, Gregory P. Nordin, N. Rahmanian
Anisotropic High Aspect Ratio Etch Development For Fluorinated Polymers With Stress Relief Technique, S. Kim, Gregory P. Nordin, N. Rahmanian
Faculty Publications
The authors have developed an anisotropic, high aspect ratio (18:1) etch for perfluorocyclobutyl (PFCB) polymers with trenches as narrow as 800 nm using a CO/O2 etch chemistry in an inductively coupled plasma reactive ion etcher. Anisotropy is achieved by carbon sidewall passivation. The motivation for this etch development is to use the air trenches as very compact waveguide splitters [S. Kim et al., Opt. Eng. 45, 054602 (2006)] The authors report a new trench widening mechanism due to tensile stress of the PFCB films and a method of avoiding this widening through the use of additional stress relief trenches on …
Maximizing Miniature Aerial Vehicles, Stephen Griffiths, Jeffery Brian Saunders, Andrew Curtis, Blake Barber, Timothy W. Mclain, Randal W. Beard
Maximizing Miniature Aerial Vehicles, Stephen Griffiths, Jeffery Brian Saunders, Andrew Curtis, Blake Barber, Timothy W. Mclain, Randal W. Beard
Faculty Publications
Despite the tremendous potential demonstrated by miniature aerial vehicles (MAV) in numerous applications, they are currently limited to operations in open air space, far away from obstacles and terrain. To broaden the range of applications for MAVs, methods to enable operation in environments of increased complexity must be developed. In this article, we presented two strategies for obstacle and terrain avoidance that provide a means for avoiding obstacles in the flight path and for staying centered in a winding corridor.
Melt Detection In Antarctic Ice Shelves Using Scatterometers And Microwave Radiometers, David G. Long, Lucas B. Kunz
Melt Detection In Antarctic Ice Shelves Using Scatterometers And Microwave Radiometers, David G. Long, Lucas B. Kunz
Faculty Publications
Ku-band dual-polarization radar backscatter measurements from the SeaWinds-on-QuikSCAT scatterometer are used to determine periods of surface freeze and melt in the Antarctic ice shelves. The normalized horizontal-polarization radar backscatter (sigmao) and backscatter polarization ratio are used in maximum-likelihood estimation of the ice state. This method is used to infer the daily ice-surface conditions for 25 study locations located on the Ronne, Ross, Larsen, Amery, Shackleton, and other ice shelves. The temporal and spatial variations of the radar response are observed for various neighborhood sizes surrounding each given location during the study period. Criteria for determining the dates of melt onset …
Comparison Of Microcantilever Hg Sensing Behavior With Thermal Higher Order Modes For As-Deposited Sputtered And Thermally Evaporated Au Films, Gregory P. Nordin, Michael A. George, Ashwini R. Kadam
Comparison Of Microcantilever Hg Sensing Behavior With Thermal Higher Order Modes For As-Deposited Sputtered And Thermally Evaporated Au Films, Gregory P. Nordin, Michael A. George, Ashwini R. Kadam
Faculty Publications
As-deposited sputtered and thermally evaporated Au films are studied for Hg sensing with rectangular Si microcantilevers. Microcantilever deflection and frequency shifts in the first four thermally induced flexural modes are measured for each type of Au film as a function of Hg exposure. All thermally induced higher order modes show shifts in their frequencies for Hg exposures when the Au is sputter deposited whereas typically only the third and fourth order modes show frequency shifts when the Au is thermally evaporated. A technique is employed in order to vary Au coverage along a microcantilever surface. The shifts in the thermal …
Systematic Design Process For Slanted Graing Couplers,, Gregory P. Nordin, J. Jiang, B. Wang
Systematic Design Process For Slanted Graing Couplers,, Gregory P. Nordin, J. Jiang, B. Wang
Faculty Publications
We have developed a systematic design process for recently proposed slanted grating couplers (SGCs) that operates in the strong coupling regime. Based on rigorous analysis of SGC properties, this design process utilizes the k-vector diagram and a rigorous grating leaky-mode solver to intentionally enforce the phase-match and Bragg conditions. We demonstrate that the resultant SGC designs have performance similar to those obtained by parallel micro-genetic algorithm (µGA) optimization with the twodimensional finite-difference time-domain (2D FDTD) method. Only two 2D FDTD simulations are necessary in the later stages of our systematic design process. Therefore the time saving is tremendous compared to …
Cross-Layer Issues In Mac Protocol Design For Mimo Ad Hoc Networks, Michael A. Jensen, A. Lee Swindlehurst, Michele Zorzi, James R. Zeidler, Adam L. Anderson, Bhaskar Rao, John Proakis, Srikanth Krishnamurthy
Cross-Layer Issues In Mac Protocol Design For Mimo Ad Hoc Networks, Michael A. Jensen, A. Lee Swindlehurst, Michele Zorzi, James R. Zeidler, Adam L. Anderson, Bhaskar Rao, John Proakis, Srikanth Krishnamurthy
Faculty Publications
In this article, we discuss research and design issues that arise in the development of networking protocols for an ad hoc network where nodes are equipped with multiple antenna elements and have the ability to perform signal processing operations as required by adaptive beamforming, interference cancellation, and space-time coding.
Random City Generator Technical Report, Brandon Call
Random City Generator Technical Report, Brandon Call
Faculty Publications
The Brigham Young University (BYU) Multiple Agent Intelligent Coordination and Control (MAGICC) research lab researchs many aspects of small unmanned air vehicles (UAV). To facilitate this research, students have created a UAV simulator called Aviones. In order to increase the capability of Aviones to simulate an urban environment, the ability to draw buildings, streets and vehicles have been added. This document outlines how cities are created and how a researcher can use them in conjunction with Aviones.
Decentralized Cooperative Aerial Surveillance Using Fixed-Wing Miniature Uavs, Randal Beard, Derek Kingston, Timothy W. Mclain, Derek Nelson
Decentralized Cooperative Aerial Surveillance Using Fixed-Wing Miniature Uavs, Randal Beard, Derek Kingston, Timothy W. Mclain, Derek Nelson
Faculty Publications
Numerous applications require aerial surveillance. Civilian applications include monitoring forest fires, oil fields and pipelines, and tracking wildlife. Applications to homeland security include border patrol and monitoring the perimeter of nuclear power plants. Military applications are numerous. The current approach to these applications is to use a single manned vehicle for surveillance. However, manned vehicles are typically large and expensive. In addition, hazardous environments and operator fatigue can potentially threaten the life of the pilot. Therefore, there is a critical need for automating aerial surveillance using unmanned air vehicles (UAVs). This paper gives an overview of a cooperative control strategy …
Compact And Low Loss Silicon-On-Insulator Rib Waveguide 90° Bend, Yusheng Qian, Seunghyun Kim, Jiguo Song, Gregory P. Nordin, Jianhua Jiang
Compact And Low Loss Silicon-On-Insulator Rib Waveguide 90° Bend, Yusheng Qian, Seunghyun Kim, Jiguo Song, Gregory P. Nordin, Jianhua Jiang
Faculty Publications
A compact and low loss silicon-on-insulator rib waveguide 90° bend is designed and demonstrated. An interface realized by a trench filled with SU8 at the corner of a waveguide bend effectively reflects incoming light through total internal reflection (TIR). In order to accurately position the SU8-filled trench relative to the waveguide and reduce sidewall roughness of the interface, electron beam lithography (EBL) is employed while inductively coupled plasma reactive ion etching (ICP RIE) is used to achieve a vertical sidewall. The measured loss for TE polarization is 0.32 dB ± 0.02 dB/bend at a wavelength of 1.55 µm.
Vector Field Path Following For Small Unmanned Aerial Vehicles, Derek R. Nelson, D. Blake Barber, Timothy W. Mclain, Randal W. Beard
Vector Field Path Following For Small Unmanned Aerial Vehicles, Derek R. Nelson, D. Blake Barber, Timothy W. Mclain, Randal W. Beard
Faculty Publications
This paper presents a new method for unmanned aerial vehicle path following using vector fields to represent desired ground track headings to direct the vehicle onto the desired path. The key feature of this approach is that ground track heading error and lateral following error approach zero asymptotically even in the presence of constant wind disturbances. Methods for following straight-line and circularorbit paths, as well as combinations of straight lines and arcs, are presented. Experimental results validate the effectiveness of this path following approach for small air vehicles flying in high-wind conditions.
Vision-Based Target Localization From A Fixed-Wing Miniature Air Vehicle, Joshua D. Redding, Timothy W. Mclain, Randal W. Beard, Clark N. Taylor
Vision-Based Target Localization From A Fixed-Wing Miniature Air Vehicle, Joshua D. Redding, Timothy W. Mclain, Randal W. Beard, Clark N. Taylor
Faculty Publications
This paper presents a method for localizing a ground-based object when imaged from a small fixed-wing unmanned aerial vehicle (UAV). Using the pixel location of the target in an image, with measurements of UAV position and attitude, and camera pose angles, the target is localized in world coordinates. This paper presents a study of possible error sources and localization sensitivities to each source. The localization method has been implemented and experimental results are presented demonstrating the localization of a target to within 11 m of its known location.
Compact Integrated Depolarizer For Interferometric Fiber Optic Gyroscopes, Lixia Li, Jaime Cardenas, Jianhua Jiang, Gregory P. Nordin
Compact Integrated Depolarizer For Interferometric Fiber Optic Gyroscopes, Lixia Li, Jaime Cardenas, Jianhua Jiang, Gregory P. Nordin
Faculty Publications
We propose an integrated waveguide depolarizer for use in interferometric fiber optic gyroscopes (IFOGs) with single-mode fiber coils. The integrated waveguide depolarizer is based on a Mach-Zender interferometer with polarizing beamsplitters. A waveguide polarizing beamsplitter is designed using multiple air trench structures oriented at the Brewster angle. We also analyze the effect of component imperfections on the degree of polarization achievable with an integrated waveguide depolarizer.
Design Of Compact Polymer Mach-Zender Interferometer And Ring Resonator With Air Trench Structures, Seunghyun Kim, Jianhua Jiang, Gregory P. Nordin
Design Of Compact Polymer Mach-Zender Interferometer And Ring Resonator With Air Trench Structures, Seunghyun Kim, Jianhua Jiang, Gregory P. Nordin
Faculty Publications
We discuss the design of a compact ring resonator (RR) and Mach-Zehnder interferometer (MZI) in a low-refractive-index-contrast waveguide material system through the use of air trenches. A narrow air trench at the intersection of one input and two output waveguides can function as a high-efficiency splitter, while wider air trenches operate as waveguide bends. We first discuss the design of individual splitters and bends and then show how they can be used to realize a compact MZI and RR. The RR has a footprint of only 70 X 100 um, and its optical efficiency at the drop wavelengths is 86%. …
Cooperative Forest Fire Surveillance Using A Team Of Small Unmanned Air Vehicles, Randal Beard, David Casbeer, Derek Kingston, Timothy W. Mclain, Sai-Ming Li, Raman Mehra
Cooperative Forest Fire Surveillance Using A Team Of Small Unmanned Air Vehicles, Randal Beard, David Casbeer, Derek Kingston, Timothy W. Mclain, Sai-Ming Li, Raman Mehra
Faculty Publications
This research was supported by NASA under STTR contract No. NNA04AA19C to Scientific Systems Company, Inc (SSCI) and Brigham Young University (BYU), and by AFOSR grants F49620-01-1-0091 and F49620-02-C- 0094. The objective of this paper is to explore the feasibility of using multiple low-altitude, short endurance (LASE) unmanned air vehicles (UAVs) to cooperatively monitor and track the propagation of large forest fires. A real-time algorithm for tracking the perimeter of a fire with an on-board infrared sensor is developed. Using this algorithm, we develop a decentralized multiple-UAV approach to monitoring the perimeter of the fire. The UAVs are assumed to …
Satisficing Negotiations, Wynn C. Stirling, James K. Archibald, Jared C. Hill, F. Ryan Johnson
Satisficing Negotiations, Wynn C. Stirling, James K. Archibald, Jared C. Hill, F. Ryan Johnson
Faculty Publications
Negotiation procedures that are founded on the doctrine of individual rationality, where each participant is committed to maximizing its own satisfaction, are limited in their ability to accommodate the interests of others, and therefore, may unnecessarily constrain the negotiability of a decision maker, particularly in cooperative environments. Satisficing game theory provides a distinct alternative to the hyperrationality of conventional rational choice by waiving reliance on the individual rationality premise and offering an approach to negotiatory decision making that is based on a well-defined mathematical notion of satisficing, or being good enough, that permits the modeling of complex interrelationships between agents. …
Microwave Observations Of Daily Antarctic Sea-Ice Edge Expansion And Contraction Rates, David G. Long, Jeffrey R. Allen
Microwave Observations Of Daily Antarctic Sea-Ice Edge Expansion And Contraction Rates, David G. Long, Jeffrey R. Allen
Faculty Publications
Algorithms for estimating sea-ice extent from remotely sensed microwave sensor data can benefit from knowledge of the "a priori" distribution of the daily expansion and contraction of the sea-ice pack. To estimate the probability distribution of daily Antarctic sea-ice extent change, two independent sea-ice datasets are analyzed: sea-ice extent derived from the QuikSCAT scatterometer and ice concentration estimates from the Special Sensor Microwave/Imager. The daily sea-ice advance and retreat is tracked over a four-year period. The distribution of the daily sea-ice advance/retreat from each sensor is similar and is approximately double-exponential. Daily ice-pack statistics are presented.
Use Of Thermally Induced Higher Order Modes Of A Microcantilever For Mercury Vapor Detection, Gregory P. Nordin, Michael A. George, Ashwini R. Kadam
Use Of Thermally Induced Higher Order Modes Of A Microcantilever For Mercury Vapor Detection, Gregory P. Nordin, Michael A. George, Ashwini R. Kadam
Faculty Publications
We demonstrate the use of thermally induced higher order modes of a microcantilever as an alternate detection technique by studying Au-Hg interactions. The first four thermally induced flexural modes - i.e., the fundamental and first three higher order modes - have been examined for two different Au coatings. In the first case, 50 nm thick Au is sputter deposited along the entire length of a rectangular Si microcantilever. In the second case the Au is confined to a 30 µm length at the tip of the Si microcantilever. In both cases the microcantilever spectral response and deflection has been studied …
Reducing Energy In Fpga Multipliers Through Glitch Reduction - Clock Power And Digit-Serial Addendum, Nathaniel Rollins, Michael J. Wirthlin
Reducing Energy In Fpga Multipliers Through Glitch Reduction - Clock Power And Digit-Serial Addendum, Nathaniel Rollins, Michael J. Wirthlin
Faculty Publications
Sponsorship: NASA. In a previous paper it was shown that reducing the amount of glitches in digital designs can significantly reduce the amount of dynamic power consumption. Pipelined multipliers and a bit-serial multiplier design were used to show this. The paper failed to mention how much of the dynamic power consumption was due to the clock distribution. Also the only digit- serial multiplier digit size investigated was a digit size of 1. This paper addresses the issue of dynamic clocking power and includes results of digit-serial multipliers with larger digit sizes.