| Dielectric Response at THz Frequencies of Fe Water Complexes and Their Interaction with O3 Calculated by Density Functional Theory |
24 Oct 2012 |
69 pages |
| Authors:
L Huang; Samuel G Lambrakos; A Shabaev; L Massa; C Yapijakis; NAVAL RESEARCH LAB WASHINGTON DC
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 | The need for better monitoring of water quality and levels of water contamination implies a need for determining the dielectric response properties of water contaminants with respect to electromagnetic wave excitation. In addition to monitoring contaminants, there is an associated need for monitoring chemical processes whose purpose is deactivation or assistance in the removal of water contaminants. Two naturally occurring water contaminants, which are the result of decaying vegetation, are ... |
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| Dielectric Response at THz Frequencies of Mg Water Complexes Interacting with O3 Calculated by Density Functional Theory |
24 Oct 2012 |
67 pages |
| Authors:
L Huang; Samuel G Lambrakos; A Shabaev; L Massa; C Yapijakis; NAVAL RESEARCH LAB WASHINGTON DC CENTER FOR COMPUTATIONAL MATERIALS SCIENCE
|
| The need for better monitoring of water quality and levels of water contamination implies a need for determining the dielectric response properties of water contaminants with respect to electromagnetic wave excitation. In addition to monitoring contaminants, there is an associated need for monitoring chemical processes whose purpose is deactivation or assistance in the removal of water contaminants. Two naturally occurring water contaminants, which are the result of decaying vegetation, are ... |
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| Flat-Top Sector Beams Using Only Array Element Phase Weighting: A Metaheuristic Optimization Approach |
10 Oct 2012 |
53 pages |
| Authors:
Irwin D Olin; NAVAL RESEARCH LAB WASHINGTON DC
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| The development of wide flat-top sector main beams by control of only the excitation phase of phased array elements is described. Pattern parameters are determined by an optimization approach using Visual Basic macros that control the repetitive application of Microsoft Excel's Solver spreadsheet add-in. By only controlling element phases with maximum equal amplitude signals, maximum integrated beam power is achieved. The basic common structure is a linear array of equally ... |
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| Renormalization of the Graphene Dispersion Velocity Determined from Scanning Tunneling Spectroscopy |
14 Sep 2012 |
6 pages |
| Authors:
Jungseok Chae; Suyong Jung; Andrea F Young; Cory R Dean; Lei Wang; Yuanda Gao; Kenji Watanabe; Takashi Taniguchi; James Hone; Kenneth L Shepard; COLUMBIA UNIV NEW YORK DEPT OF ELECTRICAL ENGINEERING
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| In graphene, as in most metals, electron-electron interactions renormalize the properties of electrons but leave them behaving like noninteracting quasiparticles. Many measurements probe the renormalized properties of electrons right at the Fermi energy. Uniquely for graphene, the accessibility of the electrons at the surface offers the opportunity to use scanned probe techniques to examine the effect of interactions at energies away from the Fermi energy, over a broad range of ... |
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| Analysis and Simulation of Far-Field Seismic Data from the Source Physics Experiment |
Sep 2012 |
12 pages |
| Authors:
Arben Pitarka; Robert J Mellors; Arthur J Rodgers; Sean R Ford; Phillip E Harben; Jeffery L Wagoner; William R Walter; Michael E Pasyanos; Anders petersson; Oleg Y Vorobiev; LAWRENCE LIVERMORE NATIONAL LAB CA
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| The SPE-N is a series of chemical explosions intended to enhance our physical understanding and ability to quantitatively model seismic signals from explosions at the NNSS with the goal of improving our nuclear test monitoring capabilities (Brunish et al., 2010). The main objective is to develop comprehensive three-dimensional high fidelity modeling capabilities to enable a transition from the current empirically-based explosion monitoring approach, where accuracy hinges on the availability of ... |
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| High-purity Transmission of a Slow Light Odd Mode in a Photonic Crystal Waveguide |
01 Aug 2012 |
4 pages |
| Authors:
Jun Tan; Ming Lu; Aaron Stein; Wei Jiang; RUTGERS - THE STATE UNIV PISCATAWAY NJ DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
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| We demonstrate a novel scheme to control the excitation symmetry for an odd mode in a photonic crystal waveguide and investigate the spectral signature of this slow light mode. An odd-mode Mach Zehnder coupler is introduced to transform mode symmetry and excite a high-purity odd mode with 20 dB signal contrast over the background. Assisted by a mixed-mode Mach Zehnder coupler, slow light mode beating can be observed and is ... |
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| Ultraviolet Surface-Enhanced Rama Scattering for Detection Applications |
Aug 2012 |
26 pages |
| Authors:
Erik D Emmons; Jason A Guicheteau; III Fountain Augustus W; ARMY EDGEWOOD CHEMICAL BIOLOGICAL CENTER APG MD
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| Surface-enhanced resonance Raman scattering with UV excitation has the potential advantage of combining surface and molecular-resonance enhancements for a wide variety of analytes of interest. Nanostructured surfaces of Pd and Pt were formed by electroless deposition on germanium substrates. Ultrathin layers of Al were made by coating thick layers of Al on a microscope slide and partially dissolving them with hydrochloric acid. The substrates were assessed for their ability to ... |
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| Control of Plasmon Dynamics in Coupled Plasmonic Hybrid Mode Microcavities |
10 Jul 2012 |
7 pages |
| Authors:
N D Lanzillotti-Kimura; T Zentgraf; X Zhang; CALIFORNIA UNIV BERKELEY NANOSCALE SCIENCE AND ENGINEERING CENTER
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| Hybrid plasmonic microcavities display localized electromagnetic states similar to the confined electronic levels in atoms and quantum wells. Exploiting this parallelism and concepts used in photonics, we describe a novel plasmonic device based on the coupling between a plasmonic microcavity and a photonic microcavity.We theoretically analyze the coupling effects and the plasmon dynamics in structures integrated in silicon optical waveguides. We observe a strong coupling behavior between the eigenmodes that ... |
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| Compact Magnetic Antennas for Directional Excitation of Surface Plasmons |
Jul 2012 |
7 pages |
| Authors:
Yongmin Liu; Stefano Palomba; Yongshik Park; Thomas Zentgraf; Xiaobo Yin; Xiang Zhang; CALIFORNIA UNIV BERKELEY NANOSCALE SCIENCE AND ENGINEERING CENTER
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| Plasmonics is considered as one of the most promising candidates for implementing the next generation of ultrafast and ultracompact photonic circuits. Considerable effort has been made to scale down individual plasmonic components into the nanometer regime. However, a compact plasmonic source that can efficiently generate surface plasmon polaritons (SPPs) and deliver SPPs to the region of interest is yet to be realized. Here, bridging the optical antenna theory and the ... |
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| Near Field Imaging for the Characterization of Diffusion Length and Waveguiding in Zinc Oxide Nanowires |
Jun 2012 |
101 pages |
| Authors:
Anree G Little; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| novel technique of near field imaging has been advanced and used to measure free carrier diffusion length and study optical waveguiding in ZnO nanowires. The technique employs a near field scanning optical microscope (NSOM) and atomic force microscope (AFM) to optically and spatially map cathodoluminescence generated by a scanning electron microscope (SEM). The technique has been advanced from previous work on nanowires by the use of a higher resolution SEM ... |
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| Dynamics-based Nondestructive Structural Monitoring Teclrniques |
21 May 2012 |
184 pages |
| Authors:
Michael J Avioli; Fei Yan; Joseph L Rose; FBS INC STATE COLLEGE PA
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| A novel Ultrasonic Modal Analysis Teclrnique (UMAT) capable of damage detection in 3-dimensional, non-homogeneous, anisotropic structures based on ultrasonic vibration signatures was developed and implemented into a portable inspection system. The system contains an annular array actuator that is capable of providing various guided wave modes and frequencies as the loading functions to achieve high sensitivity to different defects. An analytical theory on guided wave excitations by annular arrays with/without ... |
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| Laser-induced Multi-energy Processing in Diamond Growth |
May 2012 |
168 pages |
| Authors:
Zhiqiang Xie; NEBRASKA UNIV LINCOLN DEPT OF ELECTRICAL ENGINEERING
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| Laser-induced multi-energy processing (MEP) introduces resonant vibrational excitations of precursor molecules to conventional chemical vapor deposition methods for material synthesis. In this study, efforts were extended to explore the capability of resonant vibrational excitations for promotion of energy efficiency in chemical reactions for enhancement of diamond deposition, and for control of chemical reactions. The research project mainly focused on resonant vibrational excitations of precursor molecules using lasers in combustion flame ... |
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| Terahertz Spectra of Water Complexes of Beta-HMX Calculated by Density Functional Theory |
16 Mar 2012 |
29 pages |
| Authors:
L Huang; Samuel G Lambrakos; N Bernstein; V Jacobs; A Shabaev; L Massa; NAVAL RESEARCH LAB WASHINGTON DC
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| The need for better detection of explosive devices has imposed a necessity for determining the dielectric response properties of energetic materials with respect to electromagnetic wave excitation. Among the range of different frequencies for electromagnetic excitation, the THz frequency range is of particular interest because of its nondestructive nature. The present study is based on significant progress in density functional theory (DFT), and associated software technology, which is sufficiently mature ... |
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| Free Carrier Induced Spectral Shift for GaAs Filled Metallic Hole Arrays |
13 Mar 2012 |
10 pages |
| Authors:
Jingyu Zhang; Bin Xiang; Mansoor Sheik-Bahae; S R Brueck; NEW MEXICO UNIV ALBUQUERQUE
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| For a GaAs filled metallic hole array on a pre-epi GaAs substrate, the free carriers, generated by three-photon absorption (3PA) assisted by strongly enhanced local fields, reduce the refractive index of GaAs in 200-nm thick active area through band filling and free carrier absorption. Therefore, the surface plasma wave (SPW) resonance, and the related second harmonic (SH) spectrum blue shifts with increasing fluence For the plasmonic structure on a substrate ... |
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| Binary Phase Shaping for Selective Single-Beam CARS Spectroscopy and Imaging of Gas-Phase Molecules (Postprint) |
Mar 2012 |
8 pages |
| Authors:
Paul J Wrzesinski; Dmitry Pestov; Vadim V Lozovoy; Bingwei Xu; Marcos Dantus; Sukesh Roy; James R Gord; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH PROPULSION DIRECTORATE/TURBINE ENGINE DIVISION
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| We report on mode-selective single-beam coherent anti-Stokes Raman spectroscopy (CARS) of gas-phase molecules. Binary phase shaping (BPS) is used to produce single-mode excitation of O2, N2, and CO2 vibrational modes in ambient air and gas phase mixtures, with high-contrast rejection of off-resonant Raman modes and efficient nonresonant-background suppression. In particular, we demonstrate independent excitation of CO2 Fermi dyads at 1280 and 1380 cm-1 and apply BPS for high-contrast imaging of ... |
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| Effect of Electric Fields of the Reaction Rates in Shock Initiating and Detonating Solid Explosives |
Jan 2012 |
6 pages |
| Authors:
Craig M Tarver; LAWRENCE LIVERMORE NATIONAL LAB CA
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| The presence of a strong electric field has been demonstrated to effect the shock initiation and detonation wave propagation of solid high explosives. Several mechanisms have been proposed to explain the observed increased shock sensitivity, increased detonation velocity, and decreased failure diameter of certain explosives. The most likely chemical mechanism is postulated to be the excitation of some of the explosive molecules and/or intermediate reaction products to higher energy electronic ... |
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| Vibrational and Rotational CARS Measurements of Nitrogen in Afterglow of Streamer Discharge in Atmospheric Pressure Fuel/Air Mixtures |
Jan 2012 |
11 pages |
| Authors:
S J Pendleton; A Montello; C Carter; W Lempert; M A Gundersen; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH
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| The use of nonequilibrium plasma generated by nanosecond discharges to ignite fuel/air mixtures, known as transient plasma ignition (TPI), has been shown to effectively reduce ignition delay and improve engine performance relative to spark ignition for combustion engines. While this method is potentially useful for many engine applications, at present the underlying physics are poorly understood. This work uses coherent anti-Stokes Raman spectroscopy (CARS) to measure the rotational and vibrational ... |
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| Programmable Triplet Formation and Decay in Metal-Organic Chromophores |
13 Dec 2011 |
40 pages |
| Authors:
Felix N Castellano; BOWLING GREEN STATE UNIV OH
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| This research project focused on 3 primary areas of investigation. The generalized concept of low power photon upconversion has been developed under the auspices of this funding and has led to broad recognition that this technology, based on regenerative photochemical reactions, can be applied in a range of energy-relevant applications for the conversion of low energy sunlight to higher energy photons. A second focus related to developing systematically-variable photophysics in ... |
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| Demonstration Report, Munitions Management Projects, ESTCP Project MR-200809, ALLTEM Multi-Axis Electromagnetic Induction System Demonstration and Validation, Aberdeen Proving Ground Standardized UXO Technology Demonstration Site, Version 1.0 |
17 Nov 2011 |
291 pages |
| Authors:
Theodore H Asch; GEOLOGICAL SURVEY WASHINGTON DC
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| An advanced multi-axis electromagnetic induction system, ALLTEM, has been specifically designed for detection and discrimination of unexploded ordnance (UXO). This work has been funded by ESTCP (Project MM-0809). ALLTEM uses a continuous trianglewave excitation that measures the target step response rather than the more common impulse response. Ferrous and non-ferrous metal objects have opposite polarities. The system multiplexes through all three orthogonal (Hx, Hy, and Hz axes) transmitting loops and ... |
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| Observation of Query Pulse Length Dependent Ramsey Interference in Rubidium Vapor Using Pulsed Raman Excitation |
07 Nov 2011 |
15 pages |
| Authors:
G S Pati; F K Fatemi; M S Shahriar; NAVAL RESEARCH LAB WASHINGTON DC OPTICAL SCIENCES DIV
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| We report observation of query pulse length dependent Ramsey interference (QPLD-RI), using pulsed Raman excitation in rubidium vapor. This is observed when a long, attenuated query pulse is used during pulsed Raman excitation. We explain the physical mechanism behind the QPLDRI using a Bloch vector model. We also use numerical solutions to time-dependent density matrix equations to simulate this interference effect showing qualitative agreement with experimental results. Presence of such ... |
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| Modeling Turbine Blade Crack Detection in Sonic IR Imaging with a Method of Creating Flat Crack Surface in FEA (Preprint) |
Nov 2011 |
9 pages |
| Authors:
Xiaoyan Han; Ding Zhang; Golam Newaz; Lawrence D Favro; Robert L Thomas; UNIVERSAL TECHNOLOGY CORP DAYTON OH
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| Sonic Infrared (IR) Imaging Nondestructive Evaluation (NDE) technology has shown inherent advantages for defect detection in aircraft structures. It can image a wide area within a second or two for metal material targets. Due to high stresses aircraft engine turbine blades bear during their operation, fatigue cracks can form after a number of hours of service. Sonic IR imaging shows great potential for this application. However, interaction of the sonic ... |
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| Chirp Excitation of Ultrasonic Guided Waves (Preprint) |
Nov 2011 |
16 pages |
| Authors:
Jennifer E Michaels; Sang J Lee; Anthony J Croxford; Paul D Wilcox; GEORGIA TECH RESEARCH INST ATLANTA
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| This work was funded in whole or in part by Department of the Air Force contract FA8650-09-C-5206. The U.S. Government has for itself and others acting on its behalf an unlimited, paid-up, nonexclusive, irrevocable worldwide license to use, modify, reproduce, release, perform, display, or disclose the work by or on behalf of the U.S. Government. PA Case Number and clearance date: 88ABW-2011-5438, 12 Oct 2011. Preprint journal article to be ... |
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| Control of Spatially Inhomogeneous Shear Flows |
Oct 2011 |
13 pages |
| Authors:
Dan S Henningson; Reza Dadfar; Onofrio Semeraro; Shervin Bagheri; Luca Brandt; ROYAL INST OF TECH STOCKHOLM (SWEDEN) DEPT OF MECHANICS
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| It was demonstrated the possibility to delay the transition process using a feedback controller based on localized sensors/actuators. Three-dimensional TS wave packets and streaks with finite amplitudes are considered; reduced-order models based on balanced truncation are built and used for the control design. The controller mitigates the disturbances amplitude when the flow is still laminar but nonlinear, resulting in a significant reduction of the perturbation energy and, later, in a ... |
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| Relaxation of Fermionic Excitations in a Strongly Attractive Fermi Gas in an Optical Lattice |
27 Sep 2011 |
6 pages |
| Authors:
Rajdeep Sensarma; David Pekker; Ana M Rey; Mikhail D Lukin; Eugene Demler; CALIFORNIA INST OF TECH PASADENA DEPT OF PHYSICS
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| We theoretically study the relaxation of high energy single particle excitations into molecules in a system of attractive fermions in an optical lattice, both in the superfluid and the normal phase. In a system characterized by an interaction scale U and a tunneling rate tau, we show that the relaxation rate scales as approximately Ctexp[-alphaU(2)/tau(2)In(U/tau)] in the large U/tau limit. We obtain explicit expressions for the temperature and density dependent ... |
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| Quasi-Molecular Fluorescence from Graphene Oxide |
08 Sep 2011 |
6 pages |
| Authors:
Charudatta Galande; Aditya D Mohite; Anton V Naumov; Wei Gao; Lijie Ci; Anakha Ajayan; Hui Gao; Anchal Srivastava; R B Weisman; Pulickel M Ajayan; RICE UNIV HOUSTON TX DEPT OF MECHANICAL ENGINEERING AND MATERIALS SCIENCE
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| Aqueous dispersions of graphene oxide (GO) have been found to emit a structured, strongly pH-dependent visible fluorescence. Based on experimental results and model computations, this is proposed to arise from quasi-molecular fluorophores, similar to polycyclic aromatic compounds, formed by the electronic coupling of carboxylic acid groups with nearby carbon atoms of graphene. Sharp and structured emission and excitation features resembling the spectra of molecular fluorophores are present near 500 nm ... |
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| Non-Adiabatic Atomic Transitions: Computational Cross Section Calculations of Alkali Metal-Noble Gas Collisions |
Sep 2011 |
268 pages |
| Authors:
II Lewis Charlton D; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
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| Diode Pumped Alkali Lasers operate by exciting a gaseous cell of alkali metal to its P(3/2) excited energy state. A noble gas, present in the cell, collisionally de-excites the alkali metal to its P(1/2) state. The alkali atoms then relax to their S(1/2) ground state by emitting photons. The non-radiative de-excitation due to inert gas atoms represents an interesting juncture for DPALs operation. This process must be faster than the ... |
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| Creating Extended and Dense Plasma Channels in Air by Using Spatially and Temporally Shaped Ultra-Intense Laser Pulses |
16 Aug 2011 |
24 pages |
| Authors:
Pavel Polynkin; Jerome Moloney; ARIZONA UNIV TUCSON
|
| Funds from this one-year grant supported one dedicated graduate student (Craig Ament) and the PI at 50%. The experimental research under this program was supporting the ongoing AFOSR MURI program on theoretical and numerical studies of femtosecond laser filamentation. The particular projects that we pursued in the course of this program are: 1. Creation of extended and dense plasma channels in air and other gases using a nanosecond-femtosecond dual-pulse laser ... |
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| Effects of Molecular Adsorption on the Electronic Structure of Single-Layer Graphene |
03 Aug 2011 |
12 pages |
| Authors:
V M Bermudez; J T Robinson; NAVAL RESEARCH LAB WASHINGTON DC ELECTRONICS SCIENCE AND TECHNOLOGY DIV
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| The interaction of small molecules (CCl4, CS2, H2O, and acetone) with singlelayer graphene (SLG) has been studied under steady-state conditions using infrared multipleinternal- reflection spectroscopy. Adsorption results in a broad and intense absorption band spanning the ∼200 to 500 meV range, which is attributed to electronic excitation. This effect which has not previously been reported for SLG, has been further investigated using dispersioncorrected density functional theory to model the adsorption ... |
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| Stimulated Optomechanical Excitation of Surface Acoustic Waves in a Microdevice |
26 Jul 2011 |
7 pages |
| Authors:
Gaurav Bahl; John Zehnpfennig; Matthew Tomes; Tal Carmon; MILITARY ACADEMY WEST POINT NY DEPT OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCE
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| Stimulated Brillouin interaction between sound and light, known to be the strongest optical nonlinearity common to all amorphous and crystalline dielectrics, has been widely studied in fibres and bulk materials but rarely in optical microresonators. The possibility of experimentally extending this principle to excite mechanical resonances in photonic microsystems, for sensing and frequency reference applications, has remained largely unexplored. The challenge lies in the fact that microresonators inherently have large ... |
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| Surface Optomechanics: Calculating Optically Excited Acoustical Whispering Gallery Modes in Microspheres |
18 Jul 2011 |
10 pages |
| Authors:
John Zehnpfennig; Gaurav Bahl; Matthew Tomes; Tal Carmon; MILITARY ACADEMY WEST POINT NY DEPT OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCE
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| Stimulated Brillouin scattering recently allowed experimental excitation of surface acoustic resonances in micro-devices, enabling vibration at rates in the range of 50 MHz to 12 GHz. The experimental availability of such mechanical whispering gallery modes in photonic- MEMS raises questions on their structure and spectral distribution. Here we calculate the form and frequency of such vibrational surface whispering gallery modes, revealing diverse types of surface vibrations including longitudinal, transverse, and ... |
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| Acoustic Determination of Methane Hydrate Disssociation Pressures |
JUL 2011 |
12 pages |
| Authors:
Chad A. Greene; Preston S. Wilson; Richard B. Coffin; NAVAL RESEARCH LAB WASHINGTON DC
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| The unique nature of the molecular structures of gas hydrates results in curious acoustic properties which have yet to be adequately characterized. Understanding the acoustic behavior of hydrates in liquids, in bubbly liquids, and in sediments containing liquids and/or gas is vital for surveying their location using seismic or echosounding techniques and may become a key tool for monitoring hydrate dissociation and its possible link to climate change. Acoustic properties ... |
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| Leaky Waves in Metamaterials for Antenna Applications |
JUL 2011 |
65 pages |
| Authors:
Jiming Song; IOWA STATE UNIV AMES
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| Focus was on investigating leaky waves and their excitation with multilayered metamaterials to enhance antenna performance: wave propagation along a grounded dielectric slab with double negative (DNG) materials, complex waves (leaky waves) changes with different material parameters, electric size (frequency and thickness) and loss, Sommerfeld integral path for evaluating fields accurately and efficiently, the radiation intensity and directivity of electric/magnetic dipoles over a grounded slab, and optimization of the directivity ... |
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| Ground State Resonance Structure of Molecular Clusters of beta-HMX Calculated by Density Functional Theory for THz Frequencies |
21 JUN 2011 |
41 pages |
| Authors:
L. Huang; A. Shabaev; S. G. Lambrakos; L. Massa; NAVAL RESEARCH LAB WASHINGTON DC CENTER FOR COMPUTATIONAL MATERIALS SCIENCE
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| We present calculations of ground state resonance structure associated with molecular clusters of HMX using density functional theory (DFT), which is for the construction of parameterized dielectric response functions for excitation by electromagnetic waves at compatible frequencies. These dielectric functions provide for different types of analyses concerning the dielectric response of explosives. In particular, these dielectric response functions provide quantitative initial estimates of spectral response features for subsequent adjustment with ... |
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| Coherent Control of Thermal Transport |
10 May 2011 |
8 pages |
| Authors:
Xianfan Xu; PURDUE UNIV LAFAYETTE IN
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| This project is to develop techniques for controlling conductive thermal transport through excitation and manipulation of coherent phonons in a material. Fundamental studies of coherent phonon generation and interactions with other energy carriers were carried out for the development of the technique. The main method employed in this project is a temporal pulse shaping technique to generate femtosecond laser pulse trains and to excite, enhance, and/or suppress coherent phonons in ... |
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| Optical Excitation Effects on Spin-Noise Spectroscopy in Semiconductors |
Apr 2011 |
11 pages |
| Authors:
Qiong Huang; Duncan Steel; MICHIGAN UNIV ANN ARBOR
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| The effects of laser intensity and laser wavelength on measurements of spin noise in bulk semiconductors are studied with an absorption-based optically excited impurity ionization model. The laser intensity and wavelength dependent electron spin relaxation time illustrates the gradual transition from a near nonperturbative measurement to a perturbative measurement. A strong relationship between the measured wavelength and intensity dependent absorption and the spin relaxation time is observed and is shown ... |
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| Advanced Computational Methods for Study of Electromagnetic Compatibility |
31 MAR 2011 |
18 pages |
| Authors:
Oscar Bruno; Catalin Turc; MATHEMATICAL SYSTEMS AND SOLUTIONS INC PASADENA CA
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| We have developed a variety of electromagnetic scattering solvers whose combined use enables solution of a wide range of problems in the field of electromagnetic compatibility. In particular, we 1) Developed surface integral equations for homogeneous and isotropic dielectric bodies whose bounding surfaces can contain corners and edges, and that incorporate regularizations which give rise to favorable eigenvalue distributions and small numbers of GMRES iterations; 2) Implemented a fast high-order ... |
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| Controlling the Nuclear Polarization in Quantum Dots Using Optical Pulse Shape with a Modest Bandwidth |
23 Mar 2011 |
7 pages |
| Authors:
S G Carter; Sophia E Economou; A Shabaev; A S Bracker; NAVAL RESEARCH LAB WASHINGTON DC
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| We show that detuned optical pulse trains with a modest spectral width can polarize nuclear spins in indium arsenide quantum dots. The pulse bandwidth is large enough to excite a coherent superposition of both electron spin eigenstates in these negatively charged dots but narrow enough to give partial spectral selectivity between the eigenstates. The coherent precession of electron spin states and periodic excitation focuses the nuclear spin distribution, producing a ... |
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| Novel Flexible Plastic-Based Solar Cells |
06 Mar 2011 |
6 pages |
| Authors:
Paras N Prasad; STATE UNIV OF NEW YORK AT BUFFALO AMHERST
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| In summary, CdTe nanocluster, CdTe QD with different emissions can be synthesized by carefully controlling the synthetic parameters. We observed that the non-emitting nanocluster exhibits distinguishable extinction at 446 nm. The two photon studies reveal that the two photon absorption of cluster sample is slightly higher than the QD samples. We speculate that most of the absorbed energy was transferred to phonon vibration and localized heat which may be used ... |
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| Infrasound Signal Characteristics from Small Earthquakes |
Sep 2010 |
13 pages |
| Authors:
J M Hale; Stephen J Arrowsmith; Chris Hayward; Relu Burlacu; Kristine L Pankow; Brian W Stump; George E Randall; Steven R Taylor; LOS ALAMOS NATIONAL LAB NM
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| Understanding the source properties responsible for infrasound generation is critical to developing a seismo-acoustic data discriminant to distinguish between near-surface explosions and earthquakes. The regional seismicity, complex topography, open-pit quarries, and subsurface mining in the Utah region create a unique setting for the study of near-field infrasound. The Utah network has been operating three permanent infrasound arrays collocated with seismic stations NOQ (2006), BGU (2007), and EPU (2007). Additionally, four ... |
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| Progress in Three-Dimensional Simulations of Explosions and Earthquakes |
Sep 2010 |
11 pages |
| Authors:
Arthur J Rodgers; Oleg Vorobiev; N A Petersson; Bjorn A Sjogreen; William Foxall; LAWRENCE LIVERMORE NATIONAL LAB CA
|
| Advances in numerical methods for modeling seismic wave excitation and propagation and ever more powerful parallel computers are making it easier to simulate ground motions on the scale lengths (domain sizes) and frequencies (resolutions) of importance to nuclear explosion monitoring. The objective of this research is to develop and improve methods for seismic simulation in fully 3D earth models to improve nuclear explosion monitoring. Specifically, research is directed along three ... |
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| 3-dB Bandwidth Enhancement via the Gain-Lever Effect in Quantum-Dot Lasers |
JUL 2010 |
11 pages |
| Authors:
Y. Li; Nader A. Naderi; Luke F. Lester; Vassilios Kovanis; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH AEROSPACE COMPONENTS AND SUBSYSTEMS TECHNOLOGY DIVISION
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| We investigate the small-signal modulation response of two-section, gain-lever, quantum-dot semiconductor lasers. A three-pole modulation function is derived from a 3-D set of rate equations, and a 70% 3-dB bandwidth enhancement is computed and experimentally realized in an undoped quantum-dot gain-lever laser under extreme asymmetric-bias conditions. Finally, it is demonstrated that the 3-dB bandwidth is three times the free-running relaxation oscillation frequency in these types of laser structures, as opposed ... |
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| Organic/Organometallic Hybrids as Broadband Nonlinear Transmission Materials |
JUN 2010 |
33 pages |
| Authors:
Wenfang Sun; NORTH DAKOTA STATE UNIV FARGO
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| The ultimate goal of this project is to understand the structure-property correlation in organometallic complexes in order to develop broadband nonlinear transmission materials. To realize this goal, we have synthesized and performed systematic photophysical study and nonlinear optical characterization of 87 square-planar platinum terdentate/bidentate complexes, 5 texaphyrin derivatives, and 6 stilbazolium derivatives. In addition, we investigated the photophysics and nonlinear absorption of 10 other platinum complexes and 10 zinc phthalocyanine ... |
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| Vibrational and Electronic Dynamics of Photoexcited Molecules in Solution |
18 MAY 2010 |
4 pages |
| Authors:
Fleming Crim; WISCONSIN UNIV-MADISON DEPT OF CHEMISTRY
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| This research focused on three topics that are critical to understanding and exploiting vibrational excita-tion in photoisomerization dynamics. The first aspect is exploring energy flow within a vibrationally ex-cited molecule and into the surrounding the solvent. The second aspect is intercepting the vibrationally excited molecule at different times to promote it to an electronically excited state with energy in selected vibrational motions, and the third aspect is probing the molecule ... |
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| Intrinsic Energy Localization Through Discrete Gap Breathers in One-Dimensional Diatomic Granular Crystals |
May 2010 |
15 pages |
| Authors:
G Theocharis; N Boechler; P Kevrekidis; S Job; Mason Porter; C Daraio; CALIFORNIA INST OF TECH PASADENA
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| We study localized modes in uniform one-dimensional chains of tightly packed and uniaxially compressed elastic beads in the presence of one or two light-mass impurities. For chains composed of beads of the same type, the intrinsic nonlinearity, which is caused by the Hertzian interaction of the beads, appears not to support localized, breathing modes. Consequently, the inclusion of light-mass impurities is crucial for their appearance. By analyzing the problem's linear ... |
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| Fast Spin Rotations by Optically Controlled Geometric Phases in a Charge-Tunable InAs Quantum Dot |
23 Apr 2010 |
8 pages |
| Authors:
Erik D Kim; Katherine Truex; Xiaodong Xu; Bo Sun; D G Steel; A S Bracker; D Gammon; L J Sham; MICHIGAN UNIV ANN ARBOR
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| We demonstrate optical control of the geometric phase acquired by one of the spin states of an electron confined in a charge-tunable InAs quantum dot via cyclic 2 pi excitations of an optical transition in the dot. In the presence of a constant in-plane magnetic field, these optically induced geometric phases result in the effective rotation of the spin about the magnetic field axis and manifest as phase shifts in ... |
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| Development of Improved Molecular Excitation Models |
05 Feb 2010 |
8 pages |
| Authors:
Deborah Levin; PENNSYLVANIA STATE UNIV STATE COLLEGE
|
| With respect to our modeling of condensation in supersonic expansions, we have used molecular dynamics to derive condensation based models for DSMC for non-Lennard Jonesian gases such as water, carbon dioxide, and ammonia, common combustion products found in rocket plumes. The challenge was to incorporate charge polarization terms in the cluster potential, develop and automate a strategy for recognizing the formation of clusters in an MD study of a supersonic ... |
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| Electron Spin Polarization and Detection in InAs Quantum Dots Through p-Shell Trions |
08 Jan 2010 |
7 pages |
| Authors:
S G Carter; S C Badescu; A S Bracker; NAVAL RESEARCH LAB WASHINGTON DC
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| We perform two-color time-resolved spectroscopy of spin dynamics in an ensemble of InAs quantum dots, demonstrating that an electron spin polarization in negatively charged quantum dots can be efficiently generated or detected with pulses tuned to p-shell trions. Due to the polarization selection rules and exchange splitting of the electron spin triplet and singlet trion states, the absorption probability of circularly polarized light depends strongly on the spin state of ... |
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| Excited-State Structure of Oligothiophene Dendrimers: Computational and Experimental Study |
Jan 2010 |
14 pages |
| Authors:
Ekaterina Badaeva; Michael R Harpham; Ramakrishna Guda; Oezguen Suezer; Chang-Qi Ma; Peter Baeuerle; III Goodson Theodore; Sergei Tretiak; MICHIGAN UNIV ANN ARBOR DEPT OF CHEMISTRY
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| The nature of one and two-photon absorption enhancement in a series of oligothiophene dendrimers, recently proposed for applications in entangled photon sensors and solar cells, has been analyzed using both theory (time dependent density functional theory calculations) and experiment (fluorescence upconversion measurements). The linear absorption spectra exhibit a red shift of the absorption maxima and broadening as a function of dendrimer generations. The two-photon absorption cross sections increase sharply with ... |
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| Flame Propagation Enhancement by Plasma Excitation of Oxygen. Part 2. Effects of O2(a1 Delta sub g) |
Jan 2010 |
14 pages |
| Authors:
Timothy Ombrello; Sang H Won; Yiguang Ju; Skip Williams; PRINCETON UNIV NJ DEPT OF MECHANICAL AND AEROSPACE ENGINEERING
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| The isolated effect of O2(a1Dg) on the propagation of C2H4 lifted flames was studied at reduced pressures (3.61 kPa and 6.73 kPa). The O2(a1Dg) was produced in a microwave discharge plasma and was isolated from O and O3 by NO addition to the plasma afterglow in a flow residence time on the order of 1 s. The concentrations of O2(a1Dg) and O3 were measured quantitatively through absorption by sensitive off-axis ... |
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| Flame Propagation Enhancement by Plasma Excitation of Oxygen. Part 1. Effects of O3 |
Jan 2010 |
11 pages |
| Authors:
Timothy Ombrello; Sang H Won; Yiguang Ju; Skip Williams; PRINCETON UNIV NJ DEPT OF MECHANICAL AND AEROSPACE ENGINEERING
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| The thermal and kinetic effects of O3 on flame propagation were investigated experimentally and numerically by using C3H8/O2/N2 laminar lifted flames. Ozone produced by a dielectric barrier plasma discharge was isolated and measured quantitatively by using absorption spectroscopy. Significant kinetic enhancement by O3 was observed by comparing flame stabilization locations with and without O3 production. Experiments at atmospheric pressures showed an 8% enhancement in the flame propagation speed for 1260 ... |
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