| Time Resolved Magneto-Optical Imaging in High Frequency AC Currents of YBa2Cu3O7-delta Thin Films (Postprint) |
Feb 2012 |
8 pages |
| Authors:
Andrea Lucarelli; Alexander Frey; Ran Yang; Gunter Luepke; Timothy J Haugan; George A Levin; Paul N Barnes; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH PROPULSION DIRECTORATE
|
 | We present a time-resolved magneto-optical (MO) imaging study of high-temperature superconductor (HTS) in high-frequency alternating current (AC) regime. The evolution of the magnetic flux density distribution in YBa2Cu3O7-delta (YBCO) thin film samples is studied in small steps of the phase of the applied AC current. The flux distribution at 10 K exhibits instabilities including flux jumps and flux creep. A quantitative analysis of the data allows us to obtain the ... |
|
| Pulsed Plasma Arrays for Tubulence Control |
31 Jan 2012 |
16 pages |
| Authors:
Haris J Catrakis; CALIFORNIA UNIV IRVINE
|
| The PI successfully achieved active control of flow separation using dielectric barrier discharge plasma actuation on a hemisphere mounted on an elevated flat surface in a wind tunnel. Visualization of streaklines in the flow around the hemisphere at Re = 40,000 for control-on vs. control-off showed a reduction in the size of the separation region with active flow control. Measurement of the surface pressure coefficient also showed a recovery in ... |
|
| 11.72-sq cm Active-Area Wafer Interconnected PiN Diode Pulsed at 64 kA Dissipates 382 J and Exhibits an Action of 1.7 MA(sup 2)-s |
30 Jan 2012 |
5 pages |
| Authors:
M Snook; H Hearne; Ty McNutt; N El-Hinnawy; V Veliadis; B Nechay; S Woodruff; R S Howell; David Giorgi; Joe White; NORTHROP GRUMMAN SYSTEMS CORP LINTHICUM MD ELECTRONIC SYSTEMS
|
| The Silicon carbide (SiC) device area is presently limited by material and processing defects. To meet the large current handling requirements of modern power conditioning systems, the paralleling of a large number of devices is required. This can increase costs and complexity through wafer dicing, device soldering, the inclusion of ballast resistors, and the formation of multiple wire bonds. Furthermore, paralleling numerous discrete devices increases package volume and weight and ... |
|
| Oxidation Resistance, Electrical and Thermal Conductivity, and Spectral Emittance of Fully Dense HfB2 and ZrB2 with SiC, TaSi2, and LaB6 Additives |
26 Jan 2012 |
100 pages |
| Authors:
Robert F Speyer; GEORGIA INST OF TECH ATLANTA SCHOOL OF MATERIALS SCIENCE AND MECHANICAL ENGINEERING
|
| The oxidation resistances of ZrB2 containing SiC, TaB2, and TaSi2 additions of various concentrations were studied using isothermal thermogravimetry at 1200, 1400, and 1500 deg C. Theoretically-dense ZrB2-SiC two-phase microstructures were isothermally oxidized for 90 min in a thermogravimetric analyzer in flowing air in the range 1500-1900 deg C. The oxidation resistances of theoretically-dense HfB2-SiC test specimens were evaluated via isothermal thermogravimetry at 1600, 1700 and 1800 deg C. The ... |
|
| SPIN-TORQUE MICROWAVE DETECTOR WITH OUT-OF-PLANE PRECESSING MAGNETIC MOMENT |
18 Jan 2012 |
7 pages |
| Authors:
Thomas Meitzler; Elena Bankowski; O V Prokopenko; A N Slavin; I N Krivorotov; S Jaroch; V S Tiberkevich; ARMY TANK AUTOMOTIVE RESEARCH DEVELOPMENT AND ENGINEERING CENTER WARREN MI
|
| Operation of a spin-torque microwave detector (STMD) in a weak perpendicular bias magnetic field has been studied theoretically. It is shown that in this geometry a novel dynamical regime of STMD operation, characterized by large-angle out-of-plane magnetization precession, can be realized. The excitation of the large-angle precession has threshold character and is possible only for input microwave currents exceeding a certain frequency-dependent critical value. The output voltage of an STMD ... |
|
| Fluid-Structure Interaction Evaluation of F-16 Limit Cycle Oscillations |
09 Jan 2012 |
11 pages |
| Authors:
Jason A Lechniak; Keerti K Bhamidipati; AIR FORCE FLIGHT TEST CENTER EDWARDS AFB CA
|
| Application of high-fidelity computational science and engineering (CSE) tools provide better data for decisions to enhance weapon systems acquisition, testing, and support. Fluid structure interaction (FSI) simulation is being evaluated to quantify aero-structural dynamic mechanisms that bound F-16 limit cycle oscillations (LCO). The intent of the research objectives is to provide a better understanding of flight-test aero-structural observations through the utilization of CSE tools. Validation of results provided by CSE ... |
|
| Programmable Matter |
03 Jan 2012 |
31 pages |
| Authors:
George M Whitesides; Michael Brenner; Zhigang Suo; L Mahadevan; Ralph Nuzzo; Bartosz Grzybowski; HARVARD UNIV CAMBRIDGE MA OFFICE FOR RESEARCH CONTRACTS
|
| Our final report for this program summerizes how we (Harvard) have greatly improved our understanding of assembly using magnetic levitation, and mechanical agitation. Additionally, we report on how we have developed several types of soft-actuators that change compliance and shape based on pneumatic pressurization. The Nuzzo group (University of Illinois, Urbana-Champaign) describe a new form of stimuli-responsive polymeric actuator-a chemically-driven, mechano-polymer-that provides a new approach to effecting efficient, |
|
| Piezoelectric, Solar and Thermal Energy Harvesting for Hybrid Low-Power Generator Systems With Thin-Film Batteries |
Jan 2012 |
14 pages |
| Authors:
P Gambier; S R Anton; N Kong; A Erturk; D J Inman; LOS ALAMOS NATIONAL LAB NM ENGINEERING INSTITUTE
|
| The harvesting of ambient energy to power small electronic components has received tremendous attention over the last decade. The research goal in this field is to enable self-powered electronic components for use particularly in wireless sensing and measurement applications. Thermal energy due to temperature gradients, solar energy and ambient vibrations constitute some of the major sources of energy that can be harvested. Researchers have presented several papers focusing on each ... |
|
| The Homogenized Energy Model (HEM) for Characterizing Polarization and Strains in Hysteretic Ferroelectric Materials: Material Properties and Uniaxial Model Development |
Jan 2012 |
51 pages |
| Authors:
Ralph C Smith; Zhengzheng Hu; NORTH CAROLINA STATE UNIV AT RALEIGH CENTER FOR RESEARCH IN SCIENTIFIC COMPUTATION
|
| Ferroelectric materials, such as PZT, PLZT and BaTiO3, are being considered, or are already being employed, for a large number of applications including nanopositioning, high speed valves for fuel injectors, ultrasonic transducers, high speed camera shutters and auto focusing mechanisms energy harvesting, and pico air vehicle design. Their advantages include nanometer positioning resolution, broadband frequency responses, moderate power requirements, the capability for miniaturization and complementary actuator and sensor capabilities. However, ... |
|
| The Homogenized Energy Model (HEM) for Characterizing Polarization and Strains in Hysteretic Ferroelectric Materials: Implementation Algorithms and Data-Driven Parameter Estimation Techniques |
Jan 2012 |
37 pages |
| Authors:
Zhengzheng Hu; Ralph C Smith; Jon Ernstberger; NORTH CAROLINA STATE UNIV AT RALEIGH CENTER FOR RESEARCH IN SCIENTIFIC COMPUTATION
|
| Ferroelectric materials, such as PZT, PLZT, PMN and BaTiO3, provide unique actuator and sensor capabilities for applications including nanopositioning, high speed valves and fuel injectors camera focusing and shutter mechanisms, ultrasonic devices for biomedical imaging and treatment and energy harvesting devices. However, to achieve the full potential of the materials, it is necessary to develop and employ models that quantify the creep, rate-dependent hysteresis, and constitutive nonlinearities that are intrinsic ... |
|
| The Basics of Electric Weapons and Pulsed-Power Technologies |
Jan 2012 |
9 pages |
| Authors:
Stuart Moran; NAVAL SURFACE WARFARE CENTER DAHLGREN DIV VA
|
| Most conventional weapons rely on chemical energy (explosives) as their destruction mechanism, either to explode on target, like bombs, or to create kinetic energy, like a bullet. Electric weapons are different. Electric weapons use stored electrical energy, rather than explosives, to attack or destroy the target. Electric weapons generally fall into two categories: directed-energy weapons (DEWs) and electromagnetic (EM) launchers. DEWs send energy, instead of matter, toward a target, and ... |
|
| 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
|
| 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 ... |
|
| Numerical Simulation of Nanosecond-Pulse Electrical Discharges |
Jan 2012 |
27 pages |
| Authors:
Jonathan Poggie; Nicholas J Bisek; Igor V Adamovich; Munetake Nishihara; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH
|
| Numerical calculations were carried out to examine the physics of the operation of a nanosecond-pulse, single dielectric barrier discharge in a configuration with planar symmetry. This simplified configuration was chosen as a vehicle to develop a physics-based nanosecond discharge model, including realistic air plasma chemistry and compressible bulk gas flow. First, a reduced plasma kinetic model (15 species and 42 processes) was developed by carrying out a sensitivity analysis of ... |
|
| High-Power Electrical Vehicle-Stopping Systems |
Jan 2012 |
5 pages |
| Authors:
Jordan Chaparro; Melanie Everton; NAVAL SURFACE WARFARE CENTER DAHLGREN DIV VA
|
| The military needs devices that can safely and reliably stop or arrest vehicles. The primary concern is security at entry control points and vehicle check points. In such scenarios, it is desirable to be able to stop unauthorized vehicles at predefined standoff ranges to protect personnel, equipment, and critical infrastructure. Both the military and civilian law enforcement agencies face similar issues with chase scenarios, where concerns over bringing an offending ... |
|
| Impacts of Interior Permanent Magnet Machine Technology for Electric Vehicles |
Jan 2012 |
6 pages |
| Authors:
M A Rahman; M A Masrur; M Nasir Uddin; ARMY TANK AUTOMOTIVE RESEARCH DEVELOPMENT AND ENGINEERING CENTER WARREN MI
|
| The past twenty years have been an exciting period with tremendous advances in the development of interior permanent magnet (IPM) electrical machines. Over this period the interior permanent magnet synchronous machines (IPMSM) have expanded their presence in the automotive marketplace of high-efficiency electric traction drives for the latest generation of electric vehicles (EV) and hybrid-electric vehicles (HEV). Closer examination reveals that several different knowledge-based technological advancements and market forces have ... |
|
| Characterization Techniques for a MEMS Electric-Field Sensor in Vacuum |
Jan 2012 |
13 pages |
| Authors:
Simon Ghionea; David Hull; ARMY RESEARCH LAB ADELPHI MD SENSORS AND ELECTRON DEVICES DIRECTORATE
|
| An accurate calibration of an electric-field sensor is difficult to carry out due to challenges involved in generating a uniform electric field over the sensor volume. Additionally, capacitive coupling between the field source and the sensors and related instrumentation tends to distort the measured field further. Sensor characterization includes not only calibration, but also determination of the frequency response (both magnitude and phase), noise power spectral density, dynamic range, and ... |
|
| The Magnetocatenary |
Jan 2012 |
10 pages |
| Authors:
Trevor C Lipscombe; Carl E Mungan; NAVAL ACADEMY ANNAPOLIS MD DEPT OF PHYSICS
|
| A current-carrying wire hanging between two suspension points in a transverse magnetic field adopts a shape intermediate between a circle and a hyperbolic cosine. This magnetocatenary can be analytically calculated as a novel extension of the standard hanging chain problem in an intermediate mechanics course. |
|
| Dynamic Response of Exchange Bias in Graphene Nanoribbons |
Jan 2012 |
18 pages |
| Authors:
S N Jammalamadaka; S S Rao; J Vanacken; V V Moshchalkov; WEI LU; J M Tour; ARMY RESEARCH LAB RESEARCH TRIANGLE PARK NC ARMY RESEARCH OFFICE
|
| The dynamics of magnetic hysteresis, including the training effect and the field sweep rate dependence of the exchange bias, is experimentally investigated in exchange-coupled potassium split graphene nanoribbons (GNRs). We find that, at low field sweep rate, the pronounced absolute training effect is present over a large number of cycles. This is reflected in a gradual decrease of the exchange bias with the sequential field cycling. However, at high field ... |
|
| Modular Electronics for Flash Memory Production |
28 Dec 2011 |
12 pages |
| Authors:
J F Stoddart; Chad A Mirkin; NORTHWESTERN UNIV EVANSTON IL DEPT OF CHEMISTRY
|
| The continued reduction of the feature density of memory chips has increased interest in the utilization of molecules as the functional elements in electronic memory devices because of the advantages they offer in terms of size compared to conventional circuit elements. The development of molecular electronic devices for memory applications in computing, however, continues to be an important challenge to researchers in nanoscience and nanotechnology, both from a fundamental and ... |
|
| Experimental Demonstration of Multi Barrier Plasma Actuators (MBPA) |
23 Dec 2011 |
10 pages |
| Authors:
Subrata Roy; Ryan Durscher; FLORIDA UNIV GAINESVILLE DEPT OF MECHANICAL AND AEROSPACE ENGINEERING
|
| This report is a summary of a one-year effort on demonstration experiments of a novel set of multi-barrier plasma actuators (MBPA) by the PI s research team. The typical dielectric barrier discharge (DBD) plasma actuator consists of two electrodes separated by a dielectric layer. The surrounding air locally ionizes when a radio frequency (RF), high voltage waveform is applied to one of the electrodes. This results in an electrohydrodynamic (EHD) ... |
|
| Demonstration of a Wingless Electromagnetic Air Vehicle |
20 Dec 2011 |
56 pages |
| Authors:
Subrata Roy; David Arnold; Jenshan Lin; Tony Schmidt; Rick Lind; Ryan Durscher; Mark Riherd; Tomas Houba; Richard Anderson; Justin Zito; FLORIDA UNIV GAINESVILLE
|
| The goal of this project is the proof-of-concept demonstration of an electromagnetically driven wingless aircraft with no moving component that will be able to selflift, hover and fly reliably especially under gust and impact conditions. |
|
| Modeling of Electron Field Emission from Graphene |
02 Dec 2011 |
3 pages |
| Authors:
Lay-Kee Ang; NANYANG TECHNOLOGICAL UNIV (SINGAPORE)
|
| Two tasks were focused on graphene: (1) A check if traditional Fowler-Nordheim (FN) law can be used to describe field emission from single layer vertical aligned graphene. The researchers created a Klein tunneling model to show the FN law may not be valid. The results were published in APL 99, 093112 (2011). (2) It is clear that the traditional understanding or properties of the field emission is going to be ... |
|
| Dielectric Nonlinear Transmission Line (Postprint) |
01 Dec 2011 |
6 pages |
| Authors:
David M French; Brad W Hoff; Susan Heidger; Don Shiffler; AIR FORCE RESEARCH LAB KIRTLAND AFB NM DIRECTED ENERGY DIRECTORATE
|
| A parallel plate nonlinear transmission line (NLTL) was constructed. Periodic loading of nonlinear dielectric slabs provides the nonlinear capacitance and the gaps between provide linear inductive interconnects, this is essentially the same design used by Ikezi [1],[2]. The NLTL was modeled in a circuit simulation code using the experimentally measured form of the nonlinear capacitance. Dielectric loss included in the model as an equivalent series resistance derived from the measured ... |
|
| Linear-Quadratic Control of a MEMS Micromirror using Kalman Filtering |
Dec 2011 |
91 pages |
| Authors:
Jamie P Schnapp; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
|
| The deflection limitations of electrostatic flexure-beam actuators are well known. Specifically, as the beam is actuated and the gap traversed, the restoring force necessary for equilibrium increases proportionally with the displacement to first order, while the electrostatic actuating force increases with the inverse square of the gap. Equilibrium, and thus stable open-loop voltage control, ceases at one-third the total gap distance, leading to actuator snap-in. A Kalman Filter is designed ... |
|
| Advances in Developing Multiscale Flaw Models for Eddy-Current NDE (Preprint) |
Dec 2011 |
9 pages |
| Authors:
R K Murphy; Harold A Sabbagh; Elias H Sabbagh; John R Bowler; Yuan Ji; John C Aldrin; VICTOR TECHNOLOGIES LLC BLOOMINGTON IN
|
| The need to accurately model multiscale phenomena is ubiquitous in eddy-current nondestructive evaluation. By using volume-integral equations, we are able to develop a very simple algorithm for accurately computing the response of a very small anomaly in the presence of a much larger one. We validate the algorithm and its associated code in VIC-3D(copyright) through benchmark data on two test sets: (1) a notch at a bolt hole with an ... |
|
| Characterizing Randomly Anisotropic Surfaces in Eddy-Current NDE (Preprint) |
Dec 2011 |
10 pages |
| Authors:
Harold A Sabbagh; R K Murphy; Elias H Sabbagh; John C Aldrin; VICTOR TECHNOLOGIES LLC BLOOMINGTON IN
|
| This research is motivated by two distinct considerations: the ability to model noise in Ti-6Al-4V, and to characterize surfaces that have undergone treatment due to shot-peening, low-plasticity burnishing, etc. We will show that with a single model we can analyze these sources of noise and develop a protocol and system requirements for detecting and inverting flaws in a random background. An important result of this study is the application of ... |
|
| Transient Eddy-Current Nondestructive Evaluation: Benchmark Data for Backface Slots in a Plate |
Dec 2011 |
23 pages |
| Authors:
S K Burke; M E Ibrahim; DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION CANBERRA (AUSTRALIA)
|
| The results of a benchmark experiment for transient eddy-current nondestructive evaluation are reported. The benchmark configuration corresponds to the canonical geometry of an air-cored probe coil positioned above a conductive plate containing a long back-face slot. The coil is excited by an exponentially-damped step function current and measurements are made of the change in the transient magnetic field due to the slot. The aim of the work is to provide ... |
|
| Next Generation Data Collection System for One-Pass Detection and Discrimination |
Dec 2011 |
44 pages |
| Authors:
Stephen Billings; SKY RESEARCH INC VANCOUVER (CANADA)
|
| The objective of this demonstration was to deploy the OPTEMA system to the Yuma Proving Grounds to quantify its expected detection and discrimination performance. As far as we are aware, OPTEMA represents the only advanced EMI sensor technology with the objective of achieving both the detection and discrimination tasks in a single pass of the sensor system1. In principal there will be sites where this approach is more cost effective ... |
|
| Investigation of Propagation in Foliage Using Simulation Techniques |
Dec 2011 |
115 pages |
| Authors:
Chung W Chan; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
|
| In a foliage environment, radio wave propagation is subjected to fading on both large-scales and small-scales that impairs the quality and reliability of data link transmission. This has implications for many military operations. One example is the effects of foliage on the performance of communications links and unmanned aerial vehicle (UAV) radio links when ground forces are operating in foliage environments. The purpose of this research is to evaluate some ... |
|
| Investigation of an Electromagnetic Induction Sensor |
Dec 2011 |
143 pages |
| Authors:
Jr Scott Waymond R; GEORGIA TECH APPLIED RESEARCH CORP ATLANTA GA
|
| In recent years, advanced EMI sensors that use a broad range of frequencies long with advanced signal processing have been shown to be capable of discrimination between buried land mines and many types of buried metal clutter. For these EMI sensors to be effective, they must be able to accurately, repeatably, and quickly measure the response of a buried target. This is difficult because the sensor must operate with bandwidths ... |
|
| Magnetic Surface Modes and UXO/Clutter Classification and Discrimination |
Dec 2011 |
44 pages |
| Authors:
Thomas Bell; Daniel Steinhurst; SCIENCE APPLICATIONS INTERNATIONAL CORP (SAIC) ARLINGTON VA
|
| The basic objective of this research project was to develop an improved understanding of the fundamental physics underlying classification and discrimination of unexploded ordnance (UXO) and clutter items using electromagnetic induction (EMI) data. This improved understanding can help to establish a rational basis for the development and implementation of improved UXO/clutter discrimination processing and analysis techniques capable of fully exploiting the capabilities of new EMI sensor technologies purpose-built for target ... |
|
| Electromagnetically Tunable Fluids |
29 Nov 2011 |
27 pages |
| Authors:
G H Huff; M A Bevan; Z Ounaies; J Boyd; D Lagoudas; TEXAS ENGINEERING EXPERIMENT STATION COLLEGE STATION
|
| The overarching goal of this project was to exploit the transport properties at colloidal and microfluidic dimensions to controllably alter the high-frequency electromagnetic material properties at the macro level. This was to achieve multifunctionality and reconconfigurability at device-level (antenna) scales through tunability provided by a combination of structural colloidal components and functional microfluidic components; the microfluidic system was used to both reversibly control physical properties through fluidic transport and provide ... |
|
| High Transition Temperature Quantum Interference Filters |
28 Nov 2011 |
3 pages |
| Authors:
Shane A Cybart; R C Dynes; CALIFORNIA UNIV BERKELEY DEPT OF PHYSICS
|
| We have fabricated and tested large scale arrays of Josephson junctions. Some devices have as many as 150,000 junctions in a single device. To aid in device design we have also developed a numerical simulation program in Matlab to simulate voltage magnetic field characteristics for these arrays. Our numerical simulation code supports the modeling of 2 dimensional array structures and takes into account mutual interactions between all of the squids ... |
|
| Model Development and Model-Based Control Design for Nonlinear Smart Composite Systems |
22 Nov 2011 |
14 pages |
| Authors:
Ralph C Smith; NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF MATHEMATICS
|
| This program focused on the development of physics-based models, highly efficient numerical approximation techniques, parameter estimation algorithms, and model-based control techniques for shape memory alloys and polymers, electroactive polymers, magnetic actuators, and PZT-based actuators and sensors that provide unique transducer capabilities for Air Force applications. In the modeling and simulation component, energy and statistic-based techniques were used to characterize hysteresis, constitutive nonlinearities, and complex dynamics in a manner that facilitates ... |
|
| 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
|
| 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 ... |
|
| AFLOWLIB.ORG: a Distributed Materials Properties Repository from High-throughput Ab initio Calculations |
15 Nov 2011 |
12 pages |
| Authors:
Stefano Curtarolo; Wahyu Setyawan; Shidong Wang; Junkai Xue; Kesong Yang; Richard H Taylor; Gus L Hart; Stefano Sanvito; Marco B Nardelli; Natalio Mingo; Ohad Levy; DUKE UNIV DURHAM NC DEPT OF MECHANICAL ENGINEERING AND MATERIALS SCIENCE
|
| Empirical databases of crystal structures and thermodynamic properties are fundamental tools for materials research. Recent rapid proliferation of computational data on materials properties presents the possibility to complement and extend the databases where the experimental data is lacking or difficult to obtain. Enhanced repositories that integrate both computational and empirical approaches open novel opportunities for structure discovery and optimization including uncovering of unsuspected compounds, metastable structures and correlations between various ... |
|
| Development of High Resolution Eddy Current Imaging Using an Electro-Mechanical Sensor (Preprint) |
Nov 2011 |
10 pages |
| Authors:
M R Cherry; J Welter; M P Blodgett; S Sathish; R Reibel; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
|
| Typical eddy current probes are based on measuring the impedance change of a coil excited by an AC current when the coil is placed above a conductive sample. These types of probes are limited in spatial resolution to the dimensions of the coil, and coil diameter is limited by operating frequency. Because of this, the highest resolution available with these probes is on the order of 100 mum. While detecting ... |
|
| The Impact of GaN/Substrate Thermal Boundary Resistance on a HEMT Device |
Nov 2011 |
10 pages |
| Authors:
Horacio C Nochetto; Nicholas R Jankowski; Avram Bar-Cohen; ARMY RESEARCH LAB ADELPHI MD
|
| The present work uses finite element thermal simulations of Gallium Nitride High Electron Mobility Transistors (GaN HEMTs) to evaluate the impact of device design parameters on the junction temperature. In particular the effects of substrate thickness, substrate thermal conductivity, GaN thickness, and GaN-to-substrate thermal boundary resistance (TBR) on device temperature rise are quantified. In all cases examined, the TBR was a dominant factor in overall device temperature rise. It is ... |
|
| Model Based Studies of the Split D Differential Eddy Current Probe (Preprint) |
Nov 2011 |
10 pages |
| Authors:
Jeremy S Knopp; Mark P Blodgett; R D Mooers; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
|
| This paper presents preliminary modeling work of split D differential probes, in both regular differential and reflection modes. This work is a prelude for a more in-depth model validation study using split D type probes. A modeling comparison is made for both air and ferrite cores. Lastly, numerical and experimental results are compared. |
|
| Temperature Dependence of GaN HEMT Small Signal Parameters |
Nov 2011 |
5 pages |
| Authors:
Ali M Darwish; Amr A Ibrahim; H A Hung; ARMY RESEARCH LAB ADELPHI MD
|
| This study presents the temperature dependence of small signal parameters of GaN/SiC HEMTs across the 0-150 deg C range. The changes with temperature for transconductance (gm), output impedance (C(ds) and R(ds)), feedback capacitance (C(dg)), input capacitance (C(gs)), and gate resistance (R(g)) are measured. The variations with temperature are established for g(m), C(ds), R(ds), C(dg), C(gs), and R(g) in the GaN technology. This information is useful for MMIC designs. |
|
| Impedance Compensation Method for Giant Magneto-Impedance Magnetic Sensors to Null Out the Terrestrial Residual Magnetic Field |
31 Oct 2011 |
20 pages |
| Authors:
James D Hagerty; NAVAL UNDERSEA WARFARE CENTER DIV NEWPORT RI
|
| The invention is a method, described with the appropriate auxiliary electronic circuitry, for compensating the effect of the earth s magnetic field on Giant Magneto-Impedance magnetic sensors. The method as taught is an alternate way of cancelling out the effect of the very large residual earth s magnetic field using an impedance-tuning circuit (i.e. electrical compensation) rather than the usual magnetic type of compensation. |
|
| 2010 ESTCP UXO Classification Study Rougemont, NC, ESTCP MR-1034, Demonstration Data Report, Former Camp Butner, MTADS Discrimination Array (TEMTADS) Survey |
20 Oct 2011 |
56 pages |
| Authors:
Nagi Khadr; James B Kingdon; Glenn R Harbaugh; Daniel A Steinhurst; NAVAL RESEARCH LAB WASHINGTON DC
|
| A twenty-five element planar array of transient electromagnetic induction (TEM) sensors developed by the Naval Research Laboratory under SERDP and ESTCP sponsorship was deployed to the former Camp Butner, NC as part of the ESTCP UXO Classification Study in July 2010. The TEMTADS array is used in a cued interrogation mode. It is delivered by a tow vehicle to a series of GPS-flagged locations corresponding to anomalies detected during prior ... |
|
| Free Energy Computations by Minimization of Kullback-Leibler Divergence: An Efficient Adaptive Biasing Potential Method for Sparse Representations |
14 Oct 2011 |
59 pages |
| Authors:
I Bilionis; P S Koutsourelakis; CORNELL UNIV ITHACA NY CENTER FOR APPLIED MATHEMATICS
|
| The present paper proposes an adaptive biasing potential technique for the computation of free energy landscapes. It is motivated by statistical learning arguments and unifies the tasks of biasing the molecular dynamics to escape free energy wells and estimating the free energy function, under the same objective of minimizing the Kullback-Leibler divergence between appropriately selected densities. It offers rigorous convergence diagnostics even though history dependent, non-Markovian dynamics are employed. It ... |
|
| Reconfigurable Electronics and Non-Volatile Memory Research |
14 Oct 2011 |
143 pages |
| Authors:
Kristy A Campbell; BOISE STATE UNIV ID DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
|
| This is a final report for the DEPSCoR grant titled Reconfigurable Electronics and Non-Volatile Memory Research. The primary purpose of this work was to investigate materials and fabricate devices that may display electronic properties useful for reconfigurable electronics applications and/or non-volatile memory. The grant enabled the development of microfabrication processes for exotic materials at Boise State University including material synthesis. Single-bit devices, 10 x 10 cross point arrays, 150 x ... |
|
| Light Weight Active Structural Materials |
12 Oct 2011 |
12 pages |
| Authors:
Raju V Ramanujan; NANYANG TECHNOLOGICAL UNIV (SINGAPORE)
|
| Magnet-polymer (Magpol) composites have very interesting soft transduction properties, including the ability to undergo large strains in response to an external magnetic field. In this project, the mechanical properties of a ferrogel composite system were investigated. The contraction behavior of composites prepared from silicone and micron sized iron particles was studied under the influence of an external magnetic field. By simply changing the boundary conditions, the actuation mode could be ... |
|
| Combinatorial and High Throughput Discovery of High Temperature Piezoelectric Ceramics |
10 Oct 2011 |
9 pages |
| Authors:
Krishna Rajan; Xiaoli Tan; IOWA STATE UNIV AMES
|
| This project has developed a statistical learning approach to identify potential new high temperature ferroelectric piezoelectric perovskite compounds. Our predictions of the Curie temperature (Tc) ranging from 700C-1100C are the highest reported in either experimental or theoretical studies and the number of new proposed compounds based on our work nearly doubles the known candidate piezoelectric ferroelectric perovskites. Unlike most computational studies on crystal chemistry, where the starting point is some ... |
|
| Eddy Current Benchmarking Experiments for Model Validation at AFRL |
Oct 2011 |
7 pages |
| Authors:
Jeremy S Knopp; Mark P Blodgett; Ryan D Mooers; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
|
| To support an effort to estimate characteristics of surface-connected damage (i.e., cracks) in aerospace and propulsion structures, a computer-controlled scanning capability that acquires experimental eddy current data was developed based on an Agilent 4294A Impedance Analyzer. This instrument is being used to assess performance of different computational electromagnetic codes in terms of determining how well they predict the complex response from simulated flaws in conducting plates. The particular benchmark problem ... |
|
| Efficient Propagation of Uncertainty in Simulations via the Probabilistic Collocation Method (Postprint) |
Oct 2011 |
10 pages |
| Authors:
Jeremy S Knopp; Mark P Blodgett; John C Aldrin; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
|
| Eddy current models have matured to such a degree that it is now possible to simulate realistic nondestructive inspection (NDI) scenarios. Models have been used in the design and analysis of NDI systems and to a limited extent, model-based inverse methods for Nondestructive Evaluation (NDE).The science base is also being established to quantify the reliability systems via Model-Assisted Probability of Detection (MAPOD), In realistic situations, it is more accurate to ... |
|
| Numerical Simulations of Cloaking Problems using a DPG Method |
Oct 2011 |
21 pages |
| Authors:
L Demkowicz; Jichun Li; TEXAS UNIV AT AUSTIN INST FOR COMPUTATIONAL ENGINEERING AND SCIENCES
|
| The paper reviews the construction of cloaks for 2D acoustic or electromagnetic waves using the Piola transform, and shows how the transform leads to the construction of a quasi-optimal test norm for the Discontinuous Petrov-Galerkin (DPG) method with optimal test functions for this class of problems. Numerical experiments for cylindrical and square cloaks illustrate the discussed concepts and show that the DPG method is effective in cloak simulations. |
|
| Radio Frequency and Optical Metamaterials |
Oct 2011 |
20 pages |
| Authors:
John S Derov; Alvin D Drehman; Everett E Crisman; Beverly Turchinetz; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH SENSORS DIRECTORATE
|
| This research encompassed the study of radio frequency (RF) and optical metamaterials. The RF study of metamaterials focuses on the polarization behavior of split-ring-resonators (SRR), wire-post (WP) elements, and the spatially dispersive behavior of the SRR-WP elements. The optical study of metamaterials consisted of using the nano -dot and - particle media for their electric and magnetic plasmon behavior. |
|
Electricity and Magnetism
