Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

2013

Faculty Publications

Air Force Institute of Technology

Articles 1 - 10 of 10

Full-Text Articles in Physical Sciences and Mathematics

Ground State Of The Singly Ionized Oxygen Vacancy In Rutile Tio2, A. T. Brant, Nancy C. Giles, Shan Yang (杨山), M. A. R. Sarker, S. Watauchi, M. Nagao, I. Tanaka, D. A. Tryk, A. Manivannan, Larry E. Halliburton Sep 2013

Ground State Of The Singly Ionized Oxygen Vacancy In Rutile Tio2, A. T. Brant, Nancy C. Giles, Shan Yang (杨山), M. A. R. Sarker, S. Watauchi, M. Nagao, I. Tanaka, D. A. Tryk, A. Manivannan, Larry E. Halliburton

Faculty Publications

Results from electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) experiments are used to establish the model for the ground state of the singly ionized oxygen vacancy in the interior of bulk rutile TiO2 crystals. Hyperfine from 47Ti and 49Ti nuclei show that the unpaired electron in this S = 1/2 defect is localized on one titanium ion adjacent to the oxygen vacancy (i.e., the spin is not shared by two titanium ions). These defects are formed at low temperature (∼35 K) in as-grown oxidized crystals when sub-band-gap 442 nm laser light converts doubly ionized nonparamagnetic …

Go to article

Temperature-Dependent Photoluminescence Of Ge/Si And Ge 1-Ysn Y/Si, Indicating Possible Indirect-To-Direct Bandgap Transition At Lower Sn Content, Mee-Yi Ryu, Thomas R. Harris, Yung Kee Yeo, Richard T. Beeler, John Kouvetakis May 2013

Temperature-Dependent Photoluminescence Of Ge/Si And Ge 1-Ysn Y/Si, Indicating Possible Indirect-To-Direct Bandgap Transition At Lower Sn Content, Mee-Yi Ryu, Thomas R. Harris, Yung Kee Yeo, Richard T. Beeler, John Kouvetakis

Faculty Publications

Temperature (T)-dependent photoluminescence (PL) has been investigated for both p-Ge and n-Ge1-ySny films grown on Si substrates. For the p-Ge, strong direct bandgap (ED) along with weak indirect bandgap related (EID) PL at low temperatures (LTs) and strong ED PL at room temperature (RT) were observed. In contrast, for the n-Ge1-ySny, very strong dominant EID PL at LT and strong ED PL were observed at RT. This T-dependent PL study indicates that the indirect-to-direct bandgap transitions of Ge1-ySn …

Go to article

Context-Driven Image Annotation Using Imagenet, George E. Noel, Gilbert L. Peterson May 2013

Context-Driven Image Annotation Using Imagenet, George E. Noel, Gilbert L. Peterson

Faculty Publications

Image annotation research has demonstrated success on test data for focused domains. Unfortunately, extending these techniques to the broader topics found in real world data often results in poor performance. This paper proposes a novel approach that leverages WordNet and ImageNet capabilities to annotate images based on local text and image features. Signatures generated from ImageNet images based on WordNet synonymous sets are compared using Earth Mover's Distance against the query image and used to rank order surrounding words by relevancy. The results demonstrate effective image annotation, producing higher accuracy and improved specificity over the ALIPR image annotation system. Abstract …

Go to article

Reversible Mn Segregation At The Polar Surface Of Lithium Tetraborate, Christina L. Dugan, Robert L. Hengehold, Stephen R. Mchale, Juan A. Colon Santana, John W. Mcclory, Volodymyr T. Adamiv, Yaroslav V. Burak, Ya B. Losovyj, Peter A. Dowben Apr 2013

Reversible Mn Segregation At The Polar Surface Of Lithium Tetraborate, Christina L. Dugan, Robert L. Hengehold, Stephen R. Mchale, Juan A. Colon Santana, John W. Mcclory, Volodymyr T. Adamiv, Yaroslav V. Burak, Ya B. Losovyj, Peter A. Dowben

Faculty Publications

We find Mn surface segregation for single crystals of Mn doped Li2B4O7, nominally Li1.95Mn0.05B4O7(001), but as the temperature increases, evidence of this Mn surface segregation diminishes significantly. At room temperature, the surface photovoltaic charging is significant for this pyroelectric material but is quenched at a temperature well below that seen for the undoped Li2B4O7 samples. The suppression of surface charging in the region of 120 °C that accompanies the temperature of Mn dissolution in the bulk of Li2B4 …

Go to article

Role Of Excited State Photoionization In The 852.1 Nm Cs Laser Pumped By Cs-Ar Photoassociation, J. D. Hewitt, T. J. Houlahan Jr., Jeffrey E. Gallagher, D. L. Carroll, A. D. Palla, J. T. Verdeyen, Glen P. Perram, J. G. Eden Mar 2013

Role Of Excited State Photoionization In The 852.1 Nm Cs Laser Pumped By Cs-Ar Photoassociation, J. D. Hewitt, T. J. Houlahan Jr., Jeffrey E. Gallagher, D. L. Carroll, A. D. Palla, J. T. Verdeyen, Glen P. Perram, J. G. Eden

Faculty Publications

Photoionization of Cs (6p 2P3/2) atoms during the operation of a Cs D2 line (852.1 nm: 6p 2P3/2→6s 2S1/2) laser, pumped by free→free transitions of thermal Cs-Ar ground state pairs, has been investigated experimentally and computationally. Photoexcitation of Cs vapor/Ar mixtures through the blue satellite of the D2 transition (peaking at 836.7 nm) selectively populates the 2P3/2 upper laser level by the dissociation of the CsAr excited complex. Comparison of laser output energy data, for instantaneous pump powers up to 3 MW, with the …

Go to article

Insertion Of Lithium Ions Into Tio2 (Rutile) Crystals: An Electron Paramagnetic Resonance Study Of The Li-Associated Ti3+ Small Polaron, A. T. Brant, Nancy C. Giles, Larry E. Halliburton Feb 2013

Insertion Of Lithium Ions Into Tio2 (Rutile) Crystals: An Electron Paramagnetic Resonance Study Of The Li-Associated Ti3+ Small Polaron, A. T. Brant, Nancy C. Giles, Larry E. Halliburton

Faculty Publications

Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) are used to identify a Ti3+-Li+ complex in TiO2 crystals having the rutile structure. This defect consists of an interstitial Li+ ion adjacent to a substitutional Ti3+ ion (the unpaired electron on the Ti3+ ion provides charge compensation for the Li+ ion). The neutral Ti3+-Li+ complex is best described as a donor-bound small polaron and is similar in structure to the recently reported neutral fluorine and hydrogen donors in TiO2 (rutile). Lithium ions are diffused into the crystals at …

Go to article

Large-Scale Cooperative Task Distribution On Peer-To-Peer Networks, Daniel R. Karrels, Gilbert L. Peterson, Barry E. Mullins Jan 2013

Large-Scale Cooperative Task Distribution On Peer-To-Peer Networks, Daniel R. Karrels, Gilbert L. Peterson, Barry E. Mullins

Faculty Publications

Large-scale systems are part of a growing trend in distributed computing, and coordinating control of them is an increasing challenge. This paper presents a cooperative agent system that scales to one million or more nodes in which agents form coalitions to complete global task objectives. This approach uses the large-scale Command and Control (C2) capabilities of the Resource Clustered Chord (RC-Chord) Hierarchical Peer-to-Peer (HP2P) design. Tasks are submitted that require access to processing, data, or hardware resources, and a distributed agent search is performed to recruit agents to satisfy the distributed task. This approach differs from others by incorporating design …

Go to article

Ensemble Forecasting Of Coronal Mass Ejections Using The Wsa-Enlil With Coned Model, D. Emmons, Ariel O. Acebal, A. Pulkkinen, A. Taktakishvili, Peter Macneice, D. Odstrcil Jan 2013

Ensemble Forecasting Of Coronal Mass Ejections Using The Wsa-Enlil With Coned Model, D. Emmons, Ariel O. Acebal, A. Pulkkinen, A. Taktakishvili, Peter Macneice, D. Odstrcil

Faculty Publications

The combination of the Wang‐Sheeley‐Arge (WSA) coronal model, ENLIL heliospherical model version 2.7, and CONED Model version 1.3 (WSA‐ENLIL with CONED Model) was employed to form ensemble forecasts for 15 halo coronal mass ejections (halo CMEs). The input parameter distributions were formed from 100 sets of CME cone parameters derived from the CONED Model. The CONED Model used image processing along with the bootstrap approach to automatically calculate cone parameter distributions from SOHO/LASCO imagery based on techniques described by Pulkkinen et al. (2010). The input parameter distributions were used as input to WSA‐ENLIL to calculate the temporal evolution of the …

Go to article

Insider Threat Detection Using Virtual Machine Introspection, M. Crawford, Gilbert L. Peterson, Robert F. Mills, Michael R. Grimaila Jan 2013

Insider Threat Detection Using Virtual Machine Introspection, M. Crawford, Gilbert L. Peterson, Robert F. Mills, Michael R. Grimaila

Faculty Publications

This paper presents a methodology for signaling potentially malicious insider behavior using virtual machine introspection (VMI). VMI provides a novel means to detect potential malicious insiders because the introspection tools remain transparent and inaccessible to the guest and are extremely difficult to subvert. This research develops a four step methodology for development and validation of malicious insider threat alerting using VMI. A malicious attacker taxonomy is used to decompose each scenario to aid identification of observables for monitoring for potentially malicious actions. The effectiveness of the identified observables is validated using two data sets. Results of the research show the …

Go to article

The Road To Deterministic Matrices With The Restricted Isometry Property, Afonso S. Bandeira, Matthew C. Fickus, Dustin G. Mixon, Percy Wong Jan 2013

The Road To Deterministic Matrices With The Restricted Isometry Property, Afonso S. Bandeira, Matthew C. Fickus, Dustin G. Mixon, Percy Wong

Faculty Publications

The restricted isometry property (RIP) is a well-known matrix condition that provides state-of-the-art reconstruction guarantees for compressed sensing. While random matrices are known to satisfy this property with high probability, deterministic constructions have found less success. In this paper, we consider various techniques for demonstrating RIP deterministically, some popular and some novel, and we evaluate their performance. In evaluating some techniques, we apply random matrix theory and inadvertently find a simple alternative proof that certain random matrices are RIP. Later, we propose a particular class of matrices as candidates for being RIP, namely, equiangular tight frames (ETFs). Using the known …

Go to article