| Electromagnetic Field Control and Optimization Using Metamaterials |
Dec-2009 |
168 pages |
| Authors:
Jeffrey S McGuirk; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
|
 | Transformation optics has shown the ability to cloak an object from incident electromagnetic radiation is possible. However, the material parameters are inhomogeneous, anisotropic, and, in some instances, singular at various locations. In order for a cloak to be practically realized, simplified parameter sets are required. However, the simplified parameters result in a degradation in the cloaking function. Constitutive parameters for simplified two-dimensional cylindrical cloaks have been developed with two material ... |
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| Advanced Microwave Ferrite Research (AMFeR): Phase Four |
15-Oct-2009 |
27 pages |
| Authors:
Jeffrey L Young; IDAHO UNIV MOSCOW
|
| The purpose of this research endeavor is to devise ferrite materials for microwave, self-biased circulator applications. To this end, the research team focused on two key activities. The first was the development of a ferrite/epoxy composite that can be directly injected into a dielectric substrate. As the ferrite cured, two external magnets were placed on both sides of the ferrite to align the ferrite moments; once cured, the moments were ... |
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| Mechanistic Investigations of Branched Macromolecules and Metal Nanocomposites for Nonlinear Optical Applications |
26-Sep-2009 |
29 pages |
| Authors:
Goodson; Theodore III; MICHIGAN UNIV ANN ARBOR
|
| Support from the Army Research Office (ARO) has provided the opportunity for studies encompassing a combined effort consisting of different experimental and synthetic methods to produce novel nonlinear optical (NLO) materials with enhanced properties. This included the development of new synthetic branched organic macromolecules with different central core groups such as benzene, nitrogen, phosphorous, carbon as well as adamantine. These investigations gave the opportunity to probe the importance of the ... |
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| Linearized Optically Phase-Modulated Fiber Optic Links for Microwave Signal Transport |
03-Mar-2009 |
164 pages |
| Authors:
Bryan M Hass; MARYLAND UNIV COLLEGE PARK LAB FOR PHYSICAL SCIENCES
|
| Several novel phase-modulated fiber optic links for analog or microwave signal transport up to at least 20 GHz frequency are theoretically developed and experimentally demonstrated. Each link uses a linearization technique exploiting the Lithium Niobate modulator's electro-optic anisotropy between orthogonal crystallographic axes that has not previously been applied to phase-modulated links. This technique and its variants suppress the dominant third-order distortion product to extend the sub-octave spur-free dynamic range of ... |
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| A New Approach for Investigating Crystal Stresses that Drive the Initiation of Fatigue-Induced Defects in Structural Alloys |
31-Dec-2008 |
15 pages |
| Authors:
Paul R Dawson; CORNELL UNIV ITHACA NY
|
| We have developed an approach to investigate crystals stresses during cyclic load by coordinating experiments and simulations at the size scale where fatigue induced defects initiate. Our efforts provided new understanding of the stress evolution during cyclic loading through a complementary process between the experimental measurement of lattice strain and the simulation results. The comparison of the experimental and the simulated lattice data culminated in a novel picture of how ... |
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| High Yield Magnetic Nanoparticles Filled Multiwalled Carbon Nanotubes Using Pulsed Laser Deposition |
Dec-2008 |
5 pages |
| Authors:
Dereje Seifu; Shashi P Karna; MORGAN STATE UNIV BALTIMORE MD DEPT OF PHYSICS
|
| We present a high yield filling technique of multi-walled carbon nanotubes (MWCNTs), grown vertically on a SiO2 substrate, with magnetic nanoparticles using pulsed laser deposition (PLD). Magnetization measurements in-plane and out-of-plane with respect to the sample surface indicate reasonable coercivity estimated at 0.4 T. The magnetic anisotropy is however found to be randomly oriented, indicating a polycrystalline structure. The unique difference between the in-plane and out-of-plane magnetizations is the sharing ... |
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| Theoretical and Numerical Investigation of Polymer-Particle Nanocomposites and their Effective Materials Properties |
Nov-2008 |
8 pages |
| Authors:
Qi Wang; FLORIDA STATE UNIV TALLAHASSEE DEPT OF MATHEMATICS
|
| Polymer paniculate nanocomposites (PNCs) have many industrial and military applications. They can achieve very high mechanical modulus and possess superior transport or barrier properties. The project aimed to study the mesoscopic structure formation during flow processing and the corresponding rheological consequence leading to characterization of material properties in solid states. Significant progress has been made to model the materials and to understand their rheological properties in melt or solution processing ... |
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| Toward Modeling Limited Plasticity in Ceramic Materials |
01-Sep-2008 |
22 pages |
| Authors:
ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
|
| The characteristic features of many armor-related ceramic materials are the anisotropy on the micro-scale level and the very limited, though non-vanishing, plasticity due to limited number of the planes for plastic slip. This work in progress is targeted toward revising phenomenological models of such materials with limited number of slip planes. In order to emphasize the key ideas of our approach, we illustrate the approach using the simplest possible model, ... |
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| Correlating Microstructure with Switching Field Distribution in Nanomagnetic Systems with Transmission Electron Microscopy |
Aug-2008 |
3 pages |
| Authors:
June W Lau; NATIONAL INST OF STANDARDS AND TECHNOLOGY GAITHERSBURG MD
|
| This paper examines how nominally identical nanostructures can exhibit different switching behaviors in two model systems. The first system consists of an array of perpendicularly magnetized Co/Pd multilayer nanodots. The authors found that the nonuniformity in switching fields among the nanodots in an array is due to a single grain of weak uniaxial anisotropy. In the second system, which consists of inplane magnetized Permalloy nanodot arrays, they found that edge ... |
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| High Yield Magnetic Nanoparticles Filled Multiwalled Carbon Nanotubes Using Pulsed Laser Deposition |
Aug-2008 |
3 pages |
| Authors:
Dereje Seifu; Shashi P Karna; MORGAN STATE UNIV BALTIMORE MD DEPT OF PHYSICS
|
| We present a high yield filling technique of multiwalled carbon nanotubes (MWNTs), grown vertically on a SiO2 substrate, with magnetic nanoparticles using pulsed laser deposition (PLD). Magnetization measurements in-plane and out-of- plane with respect to the sample surface indicate reasonable coercivity estimated at 0.4 T. The magnetic anisotropy is however found to be randomly oriented, indicating a polycrystalline structure. The unique difference between the in-plane and out-of-plane magnetizations is the ... |
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| The Effect of Size Distribution on the Switching Field Distribution of Co/Pd Multilayered Nanostructure Arrays |
Aug-2008 |
3 pages |
| Authors:
Dmitri Litvinov; Darren Smith; James Rantschler; Paul Ruchhoeft; Sakhrat Khizroev; HOUSTON UNIV TX CENTER FOR NANOMAGNETIC SYSTEMS
|
| We use Ion Beam Proximity Lithography (IBPL) to produce 4mm x 4mm arrays of 220 nm dots in perpendicularly-oriented Co/Pd multilayered media. IBPL is used to reduce the size distribution sigmaD of the arrays, and subsequently He+ ion irradiation is used to reduce their anisotropy. The Switching Field Distribution sigma(Hcr)/H(Cr) is measured for each sample before and after irradiation, and a linear relationship is experimentally found between sigma(Hcr)/H(Cr) and sigmaD. ... |
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| Subwavelength Imaging |
12-Jun-2008 |
19 pages |
| Authors:
Kevin J Webb; Huikan Liu; Alon Ludwig; S Schivanand; PURDUE UNIV LAFAYETTE IN SCHOOL OF ELECTRICAL AND COMPUTER ENGINEERING
|
| The imaging properties of a uniaxial anisotropic slab lens, where the dielectric tensor components are of opposite sign, are studied as a function of the structure parameters. While hypothetical parameters yield various levels of performance, a design principle to achieve good sub-wavelength resolution is suggested. The anisotropy can be implemented with a metal-insulator stack. The influence of material and thickness on the subwavelength imaging performance of a negative dielectric constant ... |
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| Multiscale Modeling and Computation of Liquid Crystal Polymers, Polymer Blends, and Polymer Nanocomposites: Investigation of Rheology and Material Properties |
15 APR 2008 |
11 pages |
| Authors:
Qi Wang; FLORIDA STATE UNIV TALLAHASSEE DEPT OF MATHEMATICS
|
| High-performance polymeric materials such as liquid crystal polymers and polymer nano-particle composites have many military applications. The project aimed to study the mesoscopic structure formation during flow processing and characterization of material properties in solid states. Significant progress has been made to model the materials and to understand their rheological properties in melt or solution processing. Electrical and thermal conduction properties of the nanocomposites are characterized by the low volume ... |
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| Investigation of 2-Dimensional Isotropy of Under-Ice Roughness in the Beaufort Gyre and Implications for Mixed Layer Ocean Turbulence |
MAR 2008 |
73 pages |
| Authors:
Timothy P. McGeehan; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| The two-dimensional (2D) spectral properties, including the degree of isotropy, of under-ice roughness in the Beaufort Gyre were investigated. Under-ice roughness plays an important role in turbulent ocean heat, salt, and momentum fluxes that determine the delicate balance between surface forcing and the ocean interior that sustains or reduces the perennial ice cover. Accurate characterization of this roughness is important for numerical modeling and prediction of the Arctic air-ice-ocean system, ... |
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| Microstructure Signature of Equilibrium Double-Diffusive Convection |
MAR 2008 |
75 pages |
| Authors:
Shelley D. Caplan; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Salt fingering is an oceanographic small-scale phenomenon that occurs in statically stable regions where relatively warm salty water lies above cold, fresh water. Currently, analyses and interpretation of most microstructure measurements and salt fingers in particular, are based upon the fundamental assumption that the microstructure is isotropic. While is it generally accepted that the isotropic assumption may lead to underestimates of the dissipation rates of thermal and velocity fluctuations by ... |
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| Noninvasive Localization of Prostate Cancer via Diffusion Sensitive MRI |
MAR 2008 |
42 pages |
| Authors:
Junqian Xu; WASHINGTON UNIV ST LOUIS MO
|
| Diffusion tensor magnetic resonance imaging (DTI) measurements of prostate cancer (PCa) were performed in vivo, in patients undergoing radical prostatectomy, and ex vivo, in the same patients' prostatectomy specimens. For the first time, the imaging data were co-registered to histological sections of the prostatectomy specimens, thereby enabling unambiguous characterization of diffusion parameters in cancerous and benign tissues. Through image co-registration and histological analysis, we have shown that increased cellularity, and ... |
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| Polymers and Liquid Crystals Symposium held in Boston, Massachusetts on August 19-23, 2007 (Abstracts) |
20 DEC 2007 |
12 pages |
| Authors:
Douglas L. Gin; COLORADO UNIV AT BOULDER
|
| This grant was used to provide partial travel assistance for 5 invited speakers for a POLY Division symposium titled "Polymers and Liquid Crystals" at the Fall 2007 ACS National Meeting in Boston, MA (Aug. 19-23, 2007). The co-organizers of this symposium were the Pt (CU Boulder) and Prof. C. Allan Guymon (University of Iowa). The focus of this symposium was to showcase new research and application directions in the area ... |
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| Proton Flux Anisotropy in Low Earth Orbit |
03 DEC 2007 |
7 pages |
| Authors:
Gregory P. Ginet; Bronislaw K. Dichter; Donald H. Brautigam; Dan Madden; AIR FORCE RESEARCH LAB HANSCOM AFB MA
|
| Proton flux anisotropy as a function of altitude in the South Atlantic Anomaly (SAA) is investigated using data from the Compact Environment Sensor (CEASE) flown onboard the Tri-Service Experiment-5 (TSX-5) satellite from June 2000 to July 2006. In a 410 x 1710 km, 69 degree inclination orbit, TSX-5 spanned a broad range of the low Earth orbit regime. Using measurements of total dose, integral energy flux >40 MeV and the ... |
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| Technical Operations Support (TOPS) III. Delivery Order 0007: Chalcopyrite Crystal Growth |
DEC 2007 |
|
| Authors:
Arnold Burger; FISK UNIV NASHVILLE TN DEPT OF PHYSICS
|
 | 1. Chalcopyrite crystal growth - AgGaSeTe was grown via Accelerated Crucible Rotation Technique (ACRT). ACRT did provide good homogeneity and elimination of bulk bubbles, however overall crystal quality was inferior to crystals grown by Horizontal Bridgman technique. The anisotropic expansion of AgGaSeTe results in better growth in horizontal configurations which leave a degree of freedom for expansion and contraction along the long, unrestricted (top) side of the crystal. AgGaSe2 and ... |
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| Estimating the Strength of Single-Ended Dislocation Sources in Micron-Sized Single Crystals (Postprint) |
OCT 2007 |
20 pages |
| Authors:
S. I. Rao; D. M. Dimiduk; M. Tang; T. A. Parthasarathy; M. D. Uchic; C. Woodward; UES INC DAYTON OH
|
| Three-dimensional (3D) discrete dislocation dynamics simulations were used to calculate the effects of anisotropy of dislocation line tension (increasing Poisson's volumes with free surfaces) and to compare them with the strength of double-ended sources of equal length. Their plastic response was directly modeled within a 1um3 volume composed of a single crystal fcc metal. In general, double-ended sources are stronger than single-ended sources of an equal length and exhibit no ... |
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| Free Space Measured Loss Comparison of Single and Double Ring Resonators for Negative Index Media |
14 SEP 2007 |
6 pages |
| Authors:
John S. Derov; Beverly W. Turchinetz; James W. Dean; Everett E. Crisman; Alvin J. Drehman; AIR FORCE RESEARCH LAB HANSCOM AFB MA SENSORS DIRECTORATE
|
| Since the first demonstration of negative refractive index using nested or edge coupled split ring resonators and posts, various proposals have been made for improvement of the structures. Loss is an ongoing concern for these media at microwave frequencies and above. One alternate design uses broadside coupled split rings printed front to back on a substrate. This approach, which avoids bianisotropic effects of edge coupled rings, has been demonstrated successfully ... |
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| Topics in the Analysis of Shear-Wave Propagation in Oblique-Plate Impact Tests |
SEP 2007 |
26 pages |
| Authors:
Mike Scheidler; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
|
| This report addresses several topics in the theoretical analysis of shock waves, acceleration waves, and centered simple waves, with emphasis on the propagation of shear waves generated in oblique-plate impact tests. The first report, "Formulas for the Pressure and Bulk Modulus in Uniaxial Strain," demonstrates that for a general, nonlinear, isotropic elastic solid, the shear stress in the uniaxially strained region ahead of the shear wave may be inferred from ... |
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| Geochemical and Rheological Constraints on the Dynamics of the Oceanic Upper Mantle |
SEP 2007 |
|
| Authors:
Jessica M. Warren; MASSACHUSETTS INST OF TECH CAMBRIDGE
|
| I provide constraints on mantle convection through observations of the rheology and composition of the oceanic upper mantle. Convection cannot be directly observed, yet is a fundamental part of the plate tectonic cycle. Relative motion among plates is accommodated by localized deformation at their boundaries. I demonstrate that in the ductile regime, strain localization occurs when different mineral phases are mixed together, limiting grain annealing. Upper mantle flow is by ... |
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| Target Tracking Onboard an Autonomous Underwater Vehicle: Determining Optimal Towed Array Heading in an Anisotropic Noise Field |
Sep-2007 |
110 pages |
| Authors:
Maria A Parra-Orlandoni; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF MECHANICAL ENGINEERING
|
| In order to overcome the challenges that an anisotropic noise field poses for underwater target tracking, we conduct an onboard estimation of the horizontal noise directionality in the real-time processing suite of an autonomous underwater vehicle (AUV) towing a horizontal line array. The estimation of the noise directionality is a precursor to another adaptive behavior: optimizing tracking capability of a towed array by choosing a particular heading that minimizes the ... |
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| Effect of Crystalline Anisotropy on Shock Propagation in Sapphire (Al2O3) |
26-Jul-2007 |
11 pages |
| Authors:
W J Nellis; I F Silvera; HARVARD UNIV CAMBRIDGE MA DEPT OF PHYSICS
|
| The main goal was to find a transparent material stronger than B4C and SiC that remains transparent under shock compression. Sapphire (Al2O3) was chosen because of its high strength and the large body of experimental data that exists to design experiments and interpret results. Published optical images of sapphire under shock indicate heterogeneous yielding and optical emission, which are probably the cause of shock-induced opacity. Heterogeneous deformation is largest for ... |
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| Magnetostatically-Coupled Anisotropic Composite Magnets with Enhanced Remanence |
JUL 2007 |
9 pages |
| Authors:
George C. Hadjipanayis; DELAWARE UNIV NEWARK
|
| The computer simulation confirmed a magnetostatic coupling between R-Fe-B matrix and thick Fe layers in hot-deformed composite magnets. However, enhancement in the remanence and maximum energy product of the hard-soft composites requires at least a partial inter-phase exchange coupling. The combination of a complete magnetostatic coupling and a partial exchange coupling may facilitate the development of anisotropic composite magnets with superior performance. The experimental studies found that (1) magneto-statically coupled ... |
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| Nonparallel Solutions of Extended Nematic Polymers Under an External Field |
01-Jun-2007 |
24 pages |
| Authors:
Qi Wang; Hong Zhou; Hongyun Wang; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| We continue the study on equilibria of the Smoluchowski equation for dilute solutions of rigid extended (dipolar) nematics and dispersions under an imposed electric or magnetic field. We first provide an alternative proof for the theorem that all equilibria are dipolar with the polarity vector parallel to the external field direction if the strength of the permanent dipole is larger than or equal to the product of the external field ... |
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| Investigation into the Combined Effects of Compaction, Strain Rate Sensitivity, and Anisotropic Damage of a Geologic Target on the Trajectory Stability of Rigid Penetrators |
01 MAY 2007 |
58 pages |
| Authors:
Oana Cazacu; Ioan R. Ionescu; FLORIDA UNIV GAINESVILLE COLL OF ENGINEERING
|
| This report presents the results of an experimental investigation into the combined effects of inelasticity and strain rate sensitivity on penetration into geologic or geological derived targets. Both material models and specific computational methods have been developed. A new class of compressible rigid viscoplastic models were proposed to capture the solid-fluid transition in behavior at high strain rates, account for damage/plasticity couplings and viscous effects which are observed in geological ... |
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| Image Enhancement in a Quantum Environment |
MAY 2007 |
33 pages |
| Authors:
Mark Coffey; COLORADO SCHOOL OF MINES GOLDEN DEPT OF PHYSICS
|
| This program investigated the ability to perform image enhancement, based upon diffusion processing, on a purely quantum or hybrid classical-quantum (type-II) computer. Given that image processing based upon solving partial differential equations has become more prevalent and developed in recent years and given that the fundamental equation of non-relativistic quantum mechanics, the Schrodinger equation, may be viewed as diffusion in imaginary time, quantum information may provide practical speedups for image ... |
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| On the Correlation Between the Self-Organized Island Pattern and Substrate Elastic Anisotropy |
APR 2007 |
12 pages |
| Authors:
Ernian Pan; Richard Zhu; Peter W. Chung; AKRON UNIV OH
|
| Self-organized quantum dots pattern depends strongly on the elastic strain energy of the substrate. It is well-known experimentally that for the elastic substrate with a high degree of anisotropy, the epitaxially grown island patterns are different for different growth orientations. In this report, by incorporating the anisotropic strain energy field into a kinetic Monte Carlo algorithm for adatom diffusion, we show that the self-organized island pattern on the surface of ... |
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| Time-Resolved and Spectroscopic Three-Dimensional Optical Breast Tomography |
APR 2007 |
36 pages |
| Authors:
Robert R. Alfano; STATE UNIV OF NEW YORK
|
| The research carried out during the current reporting period included: (a) Use of optical tomographic imaging using independent component analysis (OPTICA) developed during the first reporting period to image targets in ex vivo breast tissue specimens, (b) Extension of OPTICA for obtaining cross sectional image of targets in turbid media, (c) (d) Development of a forward model for scattered light intensity distribution in the backscattering geometry; and (e) Development of ... |
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| Image Reconstruction Based Modeling of 3D Textile Composite (Postprint) |
APR 2007 |
22 pages |
| Authors:
Eric Zhou; David Mollenhauer; Endel Iarve; DAYTON UNIV OH RESEARCH INST
|
| Innovative weaving and braiding processes open up a new opportunity for making 3-D textile composites that give significantly damage-tolerant structural response with design flexibility for durable joints, near-net shape processing, etc. To fully understand the mechanical behavior of 3-D textile composites, it is essential to perform analyses to predict effective material properties and damage initiation and growth. In this paper we present a new approach to generating 3-D textile composite ... |
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| Development and Implementation of Practical Optimal LES Models |
31 MAR 2007 |
75 pages |
| Authors:
R. D. Moser; R. J. Adrian; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| One of the most promising techniques for the prediction of turbulent flows is that of Large Eddy Simulation (LES), in which an under-resolved representation of the turbulence is simulated numerically by modeling the effects of the unresolved small-scales on the simulation. Such simulations have been applied in several flows with reasonable success. However, there are several outstanding problems that need to be addressed before LES can fulfill its promise as ... |
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| Transurethral Ultrasound Diffraction Tomography |
MAR 2007 |
48 pages |
| Authors:
Matthias C. Schabel; UTAH UNIV SALT LAKE CITY
|
| The potential for cost-effective tomographic imaging using ultrasound continues to be confronted with difficulties arising from the computational complexity of fully three-dimensional object reconstruction in the diffraction regime. Development of fast and accurate forward and inverse models for ultrasound propagation in the biomedical frequency range of 1-10 MHz is essential for diffraction tomography to be a practical imaging modality. We have implemented a flexible, object-oriented simulation system in MATLAB for ... |
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| Interactions of Organic Surfactants With Oxide Nanoparticles Grown in Aqueous Environments |
FEB 2007 |
28 pages |
| Authors:
Jennifer Synowczynski; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
|
| The goal of this report is to provide a fundamental understanding of how organic surfactants with different functional endgroups and branching structures affect the surface chemistry, organization, and growth of oxide nanoparticles (e.g., TiO2, ZnO) in aqueous solutions. It is generally known that particles grow from solution into shapes that minimize their surface free energy . The surface free energy is a complex function of the surface area, crystal anisotropy ... |
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| Thermo-Oxidative Behavior of High Temperature PMR-15 Resin and Composites (Postprint) |
FEB 2007 |
49 pages |
| Authors:
G. P. Tandon; K. V. Pochiraju; G. A. Schoeppner; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH STRUCTURAL MATERIALS BRANCH/NONMETALLIC MATERIALS DIV
|
| The present study examines the thermo-oxidative behavior of high-temperature polymer matrix composite (HTPMC) materials. Thermo-oxidative aging in neat resin is simulated with a diffusion-reaction model in which temperature, oxygen concentration, and weight loss effects are considered. The thermo-oxidative behavior of the composite, on the other hand, is significantly different from that of the constituents as the composite microstructure, including the fiber/matrix interphase/interface, introduces anisotropy in the diffusion and oxidation behavior. ... |
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| Experimental and Seismological Constraints on the Rheology, Evolution, and Alteration of the Lithosphere at Oceanic Spreading Centers |
FEB 2007 |
|
| Authors:
Brian J. deMartin; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
|
| Oceanic spreading centers are sites of magmatic, tectonic, and hydrothermal processes. In this thesis I present experimental and seismological constraints on the evolution of these complex regions of focused crustal accretion and extension. Experimental results from drained, triaxial deformation experiments on partially molten olivine reveal that melt extraction rates are linearly dependent on effective mean stress when the effective mean stress is low and non-linearly dependent on effective mean stress ... |
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| Optical Detection of Nuclear Spin States |
31 JAN 2007 |
|
| Authors:
David Cory; Chandrasekhar Ramanathan; Timothy Havel; MASSACHUSETTS INST OF TECH CAMBRIDGE
|
| The goal of this project was to improve our control over nuclear spins in the solid state, and to extend this control to coupled electron-nuclear spins. Our key results are summarized below. 1. We extended the control techniques developed in liquid state NMR quantum information processing to the control of a three-qubit solid state NMR quantum information processor. 2. To explore multi-body spin dynamics and their sensitivity to decoherence, we ... |
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| On the Equilibria of the Extended Nematic Polymers under Elongational Flow |
01-Jan-2007 |
16 pages |
| Authors:
Hong Zhou; Lynda Wilson; Hongyn Wang; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF MATHEMATICS
|
| We classify the equilibrium solutions of the Smoluchowski equation for dipolar (extended) rigid nematic polymers under imposed elongational flow. The Smoluchowski equation couples theMaier-Saupe short-range interaction, dipole-dipole interaction, and an external elongational flow. We show that all stable equilibria of rigid, dipolar rod dispersions under imposed uniaxial elongational flow field are axisymmetric. This finding of axisymmetry significantly simplifies any procedure of obtaining experimentally observable equilibria. Copyright 2007 Hong Zhou et ... |
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| Advanced Microwave Ferrite Research (AMFeR): Phase Two |
31 DEC 2006 |
48 pages |
| Authors:
Jeffrey L. Young; IDAHO UNIV MOSCOW
|
| Reported herein are the key findings and activities associated with the Office of Naval Research (ONR) Advance Microwave Ferrite Research (AMFeR) Phase Two project. This project was conceived to develop high anisotropy ferrite crystals for microwave, self-biased circulator devices. To accomplish the research objectives stated in the proposal to ONR, the AMFeR team organized itself into three task-oriented groups: material fabrication, micromagnetic modeling and microwave device design. Principle team members ... |
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| Direct Imaging of Minority Charge Carrier Transport in Triple Junction Solar Cell Layers |
DEC 2006 |
81 pages |
| Authors:
Ted J. Mills; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| An optical, contact-free method for measuring minority carrier diffusion lengths is developed and demonstrated for a range of semiconductor materials used in high efficiency triple junction solar cells. This method uses a Scanning Electron Microscope (SEM) coupled with an optical microscope. The diffusion lengths, combined with minority carrier lifetime measured via time-resolved photoluminescence, allow for the computation of minority charge carrier mobility. The technique uses images to extract diffusion length ... |
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| Regularization for Inverting the Radon Transform with Wedge Consideration (PREPRINT) |
NOV 2006 |
6 pages |
| Authors:
I. Aganj; A. Bartesaghi; M. Borgnia; H. Y. Liao; G. Sapiro; S. Subramaniam; MINNESOTA UNIV MINNEAPOLIS INST FOR MATHEMATICS AND ITS APPLICATIONS
|
| In limited angle tomography, with applications such as electron microscopy, medical imaging, and industrial testing, the object of interest is scanned over a limited angular range, which is less than the full 180 deg mathematically required for density reconstruction. The use of standard full-range reconstruction algorithms produces results with notorious "butter-fly" or "wedge" artifacts. In this work we propose a reconstruction technique with a regularization term that takes into account ... |
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| Left Handed Materials Based on Magnetic Nanocomposites |
18 OCT 2006 |
11 pages |
| Authors:
John Q. Xiao; DELAWARE STATE COLL DOVER DEPT OF PHYSICS AND ASTRONOMY
|
| A new measurement technique has been proposed to determine the sign of the index of refraction in thin film samples. We have observed signature of negative index in NiFe-SiO2 magnetic granular materials and in NiFe/SiO2 multilayers. However, the signal is weak due to thin sample and is very much sample dependent, we could not consistently confirm the properties. We have theoretically established selection criteria for magnetic materials and their structures ... |
|
| All-Optical, Photonic Band Gap Modulation in Azobenzene Liquid Crystal Doped Cholesterics (Preprint) |
OCT 2006 |
30 pages |
| Authors:
Uladzimir A. Hrozhyk; Svetlana V. Serak; Nelson V. Tabiryan; Timothy J. Bunning; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
|
| Cholesteric liquid crystals doped with high clearing temperature azobenzene liquid crystals are shown to possess large, fast, and reversible dynamic photosensitive features. Selective wavelengths shifts approaching 400 nm are reported and depending on the host cholesteric liquid crystal, both red-shifted and blue-shifted wavelength changes can be induced. The photoinduced states of these material systems are shown to be stable for long periods of time upon removal of the radiation source, ... |
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| Continuum Multiscale Modeling of Finite Deformation Plasticity and Anisotropic Damage in Polycrystals |
SEP 2006 |
30 pages |
| Authors:
J. D. Clayton; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
|
| A framework for describing the deformation and failure responses of multi-phase polycrystalline microstructures is developed from micromechanical considerations and volume averaging techniques. Contributions from damage (i.e., displacement discontinuities such as cracks, voids, and shear bands) are captured explicitly in the framework's kinematics and balance relations through additive decompositions of the total deformation gradient and nominal stress, respectively. These additive decompositions which notably enable description of arbitrarily anisotropic deformations and stresses ... |
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| Deformation and Recrystallization During Thermomechanical Processing of a Nickel-Base Superalloy Ingot Material |
SEP 2006 |
14 pages |
| Authors:
S. L. Semiatin; D. S. Weaver; R. L. Goetz; J. P. Thomas; T. J. Turner; UES INC DAYTON OH
|
| The deformation response and recrystallization behavior of a coarse, columnar-grain superalloy ingot material, Waspaloy, with a fiber texture were established. For this purpose, isothermal hot compression tests were performed on cylindrical and doublecone samples at supersolvus temperatures under both monotonic (constant strain rate) and multi-hit conditions. Plastic flow showed a noticeable dependence on test direction relative to the columnar-grain orientation; the observed anisotropy in peak flow stress and flow softening ... |
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| Prediction of Crystallographic Texture Evolution and Anisotropic Stress-Strain Curves During Large Plastic Strains in High Purity alpha-Titanium Using a Taylor-Type Crystal Plasticity Model (Preprint) |
SEP 2006 |
27 pages |
| Authors:
Xianping Wu; Surya R. Kalidindi; Carl Necker; Ayman Salem; DREXEL UNIV PHILADELPHIA PA DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| A new Taylor-type polycrystalline model has been developed to simulate the evolution of crystallographic texture and the anisotropic stress-strain response during large deformation of high purity alpha-titanium at room temperature. Crystallographic slip, deformation twinning, and slip inside the twinned regions were all considered as contributing mechanisms for the plastic strain in the model. This was accomplished by treating the dominant twin systems in a given crystal as independent grains once ... |
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| Development of Advanced Hall Plume Models |
11 AUG 2006 |
26 pages |
| Authors:
Jaume Peraire; Manuel Martinez-Sanchez; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF AERONAUTICS AND ASTRONAUTICS
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| The purpose of this work was twofold: (a) To develop numerical or analytical methods capable of dealing with the combination of three-dimensionality and strong anisotropy that occurs in the plume region near the exit of a Hall thruster, and (b) To explore the use of fluid-based models in plume computations, so as to overcome the granularity associated with normal particle-based approaches. In area (a) we have carefully formulated the 3D ... |
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| Switches and Frequency-Agile Sources With Photonic Bandgap Structures |
07 AUG 2006 |
12 pages |
| Authors:
Philippe M. Fauchet; ROCHESTER UNIV NY DEPT OF ELECTRICAL ENGINEERING
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| The tunable devices are made mostly in bulk silicon (porous silicon one- and two-dimensional photonic bandgap structures) although a few have been made in SOI (two-dimensional photonic bandgap structures). Porous silicon is formed by electrochemically etching a silicon wafer in a hydrofluoric acid-based solution. By choosing the proper silicon doping and controlling the applied current density, it is possible to achieve high quality photonic bandgap structures. Liquid crystals are the ... |
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| Microstructural Characterization and Modeling of Discontinuously-Reinforced Aluminum Composites (Postprint) |
AUG 2006 |
15 pages |
| Authors:
Jonathan E. Spowart; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
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| Models for predicting the constitutive behavior of spatially-heterogeneous microstructures such as discontinuously-reinforced aluminum (DRA) and other metallic matrix composites based on unit cell approaches generally do not incorporate higher-order microstructural features such as degree of homogeneity and spatial anisotropy of the reinforcement phase. Moreover, more complex numerical models rarely encompass the volumes of material necessary to ensure statistical relevance. The present contribution offers an alternative approach for quantifying and then ... |
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