| Phase-Locking and Frustration in an Array of Nonlinear Spin-Torque Nano-Oscillators (Preprint) |
23-Oct-2009 |
|
| Authors:
Elena Bankowski; Grant Gerhart; Andrei Slavin; Vasil Tiberkevich; OAKLAND UNIV ROCHESTER MI DEPT OF PHYSICS
|
 | We demonstrate that high-frequency cooperative dynamics of an array of coupled nonlinear spin-torque nano-oscillators (STNO) can be controlled by introduction of an additional external phase shift BETAc between the microwave current, which couples STNOs, and the total array microwave voltage. When this external phase shift BETAc compensates the intrinsic phase shift BETA0, caused by the STNO nonlinearity, a phase-locking regime with increased output power and vanishing inhomogeneous linewidth broadening is ... |
|
| High Frequency Combustion Instability Studies of LOX/Methane Fueled Rocket Engines |
25-Sep-2009 |
28 pages |
| Authors:
Robert J Santoro; PENNSYLVANIA STATE UNIV UNIVERSITY PARK
|
 | A series of studies were conducted using a rectangular rocket chamber burning LOX methane propellanrs to investigate the effect of the temperature of the methane on the lunation of combustion instability The rectangular rocket used in these studies employed LOX centered coaxial swirl injectors The rectangular injector used in these studied provided 16 possible injector element locations in a linear array. Variation of injector element location showed that injector elements ... |
|
| Power Enhancement of a Rubidium Vapor Laser With a Master Oscillator Power Amplifier (Postprint) |
15-Sep-2009 |
6 pages |
| Authors:
David A Hostutler; Wade L Klennert; AIR FORCE RESEARCH LAB KIRTLAND AFB NM DIRECTED ENERGY DIRECTORATE
|
| A master oscillator power amplifier (MOPA) with variable amplifier gain lengths was built to demonstrate power enhancement of an alkali vapor laser. A small signal gain of 0.91 / cm for two different gain lengths was observed. For a 2 cm long amplifier gain length an amplification of 7.9 dB was observed. |
|
| Wall-Plug Efficiencies of High-Power Free Electron Lasers Employing Energy Recovery Linacs |
23-Apr-2009 |
28 pages |
| Authors:
Phillip Sprangle; Joseph Penano; Bahman Hafizi; Ilan Ben-Zvi; NAVAL RESEARCH LAB WASHINGTON DC BEAM PHYSICS BRANCH
|
| In a high average power free electron laser (FEL) the wall-plug efficiency is of critical importance in determining the size, complexity and cost of the overall system. The wall-plug efficiency for the FEL oscillator and amplifier (uniform and tapered wiggler) are strongly dependent on the energy recovery process. A theoretical model for electron beam dynamics in the energy recovery linac is derived and applied to the acceleration and de-acceleration of ... |
|
| Q-Switched and Mode Locked Short Pulses from a Diode Pumped, YB-Doped Fiber Laser |
26-Mar-2009 |
115 pages |
| Authors:
Seth M Swift; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
|
| A diode-pumped, ytterbium (Yb)-doped fiber laser system was designed and demonstrated to operate in continuous wave (cw), passively Q-switched and possibly passively mode locked operation. To our knowledge, this was the first fiber laser oscillator built at the Air Force Institute of Technology. A Cr4+:YAG (Chromium: Ytterbium Aluminum Garnett) crystal was used as a saturable absorber to generate Q-switched pulses. Attempts to mode lock the laser were performed using a ... |
|
| Equivalent Roughness Height for Plane Bed Under Oscillatory Flow |
Jan-2009 |
15 pages |
| Authors:
Magnus Larson; Benoit Camenen; Atilla Bayram; CEMAGREF LYON (FRANCE)
|
| A new relationship between the roughness height and the main hydrodynamic and sediment parameters for plane beds under oscillatory conditions is presented. In order to derive such a relationship, a large data base encompassing plane-bed experiments was compiled from previous investigations and analyzed. Different methods to estimate the roughness height were investigated. Comparisons between the data and different existing predictive formulas for the bed roughness obtained from the literature were ... |
|
| Complexity-Enabled Sensor Networks and Photonic Switching Devices |
20-Dec-2008 |
23 pages |
| Authors:
D J Gauthier; DUKE UNIV DURHAM NC OFFICE OF RESEARCH SUPPORT
|
| The researchers have demonstrated that a holistic, complexity-based design approach can lead to improved functionality or sensitivity of devices. They have developed two different types of devices, each of which is optimized for different applications: an opto-electronic chaotic oscillator that can be used as a building block for an intrusion detection network; and an ultra-low-light-level photonic switch for quantum information networks. Although these devices are quite different, they are both ... |
|
| UMD/NPS Free Electron Laser Research |
01-Dec-2008 |
77 pages |
| Authors:
Joseph Blau; William B Colson; MARYLAND UNIV COLLEGE PARK
|
| Simulations and theoretical analysis are used to study the development of high-average-power free electron lasers (FELs). Various existing and proposed FELs are studied, in both amplifier and oscillator configurations. Comparisons to experimental results show good agreement in each case. At the outset of this project, short Rayleigh length (SRL) optical cavities were proposed to reduce the optical intensity on the mirrors. Contrary to conventional wisdom, our simulations showed that an ... |
|
| Evaluation of Output Phase Stability in a Fiber-Optic Two-Way Frequency Distribution System |
01-Dec-2008 |
9 pages |
| Authors:
Sven-Christian Ebenhag; Kenneth Jaldehag; Per Jarlemark; Per O Hedekvist; Carsten Rieck; Hakan Skoogh; SP TECHNICAL RESEARCH INST OF SWEDEN BORAS (SWEDEN)
|
| The assembly of a real-time actively controlled fiber-optic frequency transfer link based on additions to an existing static solution is proposed and evaluated. The dynamic variations of transmission delays, caused mainly by temperature dependence of the fiber, is continuously measured and used to adjust a delay at the transmitter for net cancellation of the effect. The resulting link shows no visible temperature dependence; however, the feedback induces added noise at ... |
|
| A Prototype Cesium Clock Ensemble for The Loran-C Radionavigation System |
01-Dec-2008 |
15 pages |
| Authors:
Aaron P Dahlen; COAST GUARD WILDWOOD NJ ELECTRONICS ENGINEERING CENTER
|
| This paper presents a prototype real time clock ensemble designed for semi-autonomous operation at unmanned Loran-C radionavigation transmitting stations. This clock is designed to mitigate a doomsday scenario where all space-based timing assets are lost. It is implemented using three free-running commercial cesium oscillators, a traditional measurement system, and an Auxiliary Output Generator (AOG) phase-locked to the weighted mean of the cesium ensemble. A relatively inexpensive rubidium oscillator is used ... |
|
| Chaotic Scrambling for Wireless Analog Video |
Dec-2008 |
8 pages |
| Authors:
KRISHNA MYNENI; Shawn D Pethel; Ned J Corron; Billy R Reed; Jonathan N Blakely; ARMY RESEARCH DEVELOPMENT AND ENGINEERING COMMAND REDSTONE ARSENAL AL
|
| We report the implementation of an in-band chaotic scrambler for securing wireless analog video. In this demonstration system, an analog video signal is injected into a chaotic oscillator and the output is transmitted through a standard wireless video link. At the receiver, a descrambler separates the video from the chaotic signal in real time. Experimental results show the scrambled signal effectively hides the original video image, yet the descrambler recovers ... |
|
| Time Shifting Chaotic Signals Using Synchronization |
Dec-2008 |
6 pages |
| Authors:
Ned J Corron; Jonathan N Blakely; ARMY AVIATION AND MISSILE RESEARCH DEVELOPMENT ENG CTR REDSTONE ARSENAL AL
|
| In this paper we examine two couplings that produce time-shifted synchronization in a pair of chaotic oscillators. The couplings do not utilize an explicit time-delay term. We characterize the observed synchronization by determining the dependence of the time shift and cross correlation between the drive and response oscillators on a tunable parameter. Our observations agree well with estimates of the time shift and cross correlation using a transfer function. |
|
| Efficient THZ Source Based on Cascaded Optical Down-Conversion in Orientation-Patterned GaAs Structures |
20-Nov-2008 |
34 pages |
| Authors:
Xiaojun Yu; Walter Hurlbut; Vladimir Kozlov; James Harris; Anjie Lin; Paulina Kuo; Joe Schaar; Martin Fejer; Konstantin Vodopyanov; Candace Lynch; David Bliss; Yun-Shik Lee; STANFORD UNIV CA EDWARD L GINZTON LAB OF PHYSICS
|
| The goal of this DARPA TIFT project was to demonstrate an efficient room temperature source for THz imaging systems based on optical down-conversion in an orientation-patterned GaAs microstructure, incorporated into an optical resonant cavity, and pumped by a compact solid state laser. The main achievements are: (1) quasi-phase-matched (QPM) GaAs microstructures with periodic reversal of crystalline orientation, including orientation-patterned GaAs (OPGaAs), diffusion-bonded GaAs (DB-GaAs) and optically-contacted GaAs (OC-GaAs) suitable for ... |
|
| Laser Induced Millimeter Wave Fluorescence From Bio-Materials |
Oct-2008 |
32 pages |
| Authors:
Ashish Tripathi; Raphael P Moon; Boris Gelmont; EDGEWOOD CHEMICAL BIOLOGICAL CENTER ABERDEEN PROVING GROUND MD RESEARCH AND TECHNOLOGY DIR
|
| In this report, we conduct the initial theoretical investigation of emission of radiation by DNA components upon the absorption of infrared (IR) radiation. Excitation wavelengths in 9 and 11 urn region are of interest. These transitions are related to the bond vibrations including only small groups of atoms. Hence, it is possible to analyze different fragments of DNA for identification of proper transitions. The carbon dioxide (CO2) laser was chosen ... |
|
| A Plasma-Assisted Megawatt Class Microwave Source With an Output of 1KJ Per Pulse |
01-Sep-2008 |
9 pages |
| Authors:
Yuval Carmel; MARYLAND UNIV COLLEGE PARK INST FOR RESEARCH IN ELECTRONICS AND APPLIED PHYSICS
|
| The Air Force requires lightweight, compact sources of high-power high-frequency radiation for numerous applications in communications, radar, ECM, and directed-energy weapons (DEW). This effort will be a satellite effort under the "Microwave Power Research Initiative (MiPRI)" program that addresses important research issues that impact directly on both the high-power microwave (HPM) and microwave vacuum electronics (MVE) R&D thrusts within the DOD. The goal of the proposed basic research is to ... |
|
| Advanced Electrodynamic Tether Systems: Modeling of Scattering and Unsteady Effects |
06-Jun-2008 |
|
| Authors:
Manuel Martinez-Sanchez; Oleg Batishchev; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF AERONAUTICS/ASTRONAUTICS
|
| This work addresses the needs for advanced computational tools and theoretical models devoted to the study of two interrelated topics of interest to the Air Force: Radiation Belt Remediation (RBR) and potential use of tethers as low frequency oscillators/radiators. Both problems stretch the capabilities of existing numerical methods, while connecting with a body of previous work on probe theory, spacecraft-plasma interactions and electrodynamic tether propulsion. The Electrostatic RBR application would ... |
|
| Quantum Communication Systems |
15-Mar-2008 |
21 pages |
| Authors:
Ian A Walmsley; OXFORD UNIV (UNITED KINGDOM)
|
| This report results from a contract tasking University of Oxford as follows: The Grantee will investigate ....... Photonic quantum sources for scalable Linear Optics Quantum Communications (LOQC). The objective of this work package is to develop photonic sources suitable for linear optical quantum communications. This requires the efficient preparation and utilization of single- and multiple photons in pure states, with good modal quality, compatible with guided wave optics |
|
| Limitations of a True Random Number Generator in a Field Programmable Gate Array |
DEC 2007 |
146 pages |
| Authors:
Jennifer L. Brady; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
|
| Random number generators are used in many areas of engineering, computer science, most notably in simulations and cryptographic applications. Only a true random number generator is secure because the output bits are non-repeating and non-reproducible. A true random number generator on a field programmable gate array allows the generator on chip reducing the possibility of a breach in security. An oscillator sampling technique is an effective TRNG in a Xilinx ... |
|
| Novel Designs and Coupling Schemes for Affordable High Energy Laser Modules |
28 SEP 2007 |
74 pages |
| Authors:
Jerome V. Moloney; Axel Schulzgen; Pavel Polynkin; Masud Mansuripur; Mahmoud Fallahi; Yoel Fink; Chiping Chen; ARIZONA UNIV BOARD OF REGENTS TUCSON
|
| This multi-disciplinary research effort developed new classes of compact, highly-doped Er/Yb phosphate-doped glass fibers as high power, low noise single wavelength, single mode oscillators. Three world record powers in low-noise, single frequency laser oscillators at the eyesafe wavelength of 1.55 micrometers were reported. The project vertically integrated fabrication, testing, and optimization of all components necessary for manufacturing of fiber laser units including highly doped specialty glasses, fiber preforms, fiber drawing ... |
|
| Wall-Plug Efficiencies of FEL Amplifiers and Oscillators Employing Energy Recovery Linacs |
06 JUN 2007 |
10 pages |
| Authors:
Phillip Sprangle; Joseph Penano; Bahman Hafizi; Ilan Ben-Zvi; NAVAL RESEARCH LAB WASHINGTON DC PLASMA PHYSICS DIV
|
| In a high average power FEL, the wall-plug efficiency is of critical importance in determining the size, complexity, and cost of the overall system. The wall-plug efficiency for the FEL oscillator and amplifier (uniform and tapered wiggler) are obtained and compared. In general, we find that the wall-plug efficiency for the tapered wiggler FEL amplifier is more than a factor of two greater than that of the oscillator. For typical ... |
|
| A Practical Guide to Isolation Amplifier Selection |
MAY 2007 |
7 pages |
| Authors:
Warren F. Walls; Fred L. Walls; NAVAL OBSERVATORY WASHINGTON DC TIME SERVICE DIV
|
| Whether distributing a house standard, adding a distribution module in a larger circuit design, or just working with a measurement system on the bench, one must be aware of how a number of distribution amplifier parameters can make or break an entire system's performance. This paper looks at a high performance quartz oscillator, a hydrogen maser, and a rubidium fountain's performance both in the short-term and long-term to develop a ... |
|
| Ocean Wave Energy Harvesting Devices |
APR 2007 |
34 pages |
| Authors:
Jeffrey T. Cheung; III Childress Earl F.; TELEDYNE SCIENTIFIC AND IMAGING LLC THOUSAND OAKS CA
|
| Development of an ocean wave energy-harvesting device that can be used as a renewable energy source for ocean monitoring systems. The core technology is a mass-spring based high efficiency, low frequency linear generator that was integrated to a spar buoy to form a robust unit. Its dynamic sensitivity is improved by the use of a near zero friction liquid bearing. Through extensive theoretical modeling and wave tank testing, we studied ... |
|
| Early Detection of Prostate Cancer |
JAN 2007 |
|
| Authors:
Massood Atashbar; Bruce E. Bejcek; WESTERN MICHIGAN UNIV KALAMAZOO
|
| Acoustic wave sensors have been widely used for detection of various chemical and biological species in liquid media. An improved binding of Protein A and IgG molecules on QCM biosensors by modifying the gold surface of the quartz crystal with a 35nm polystyrene film followed by an acidic treatment was accomplished. Also, the increase in the sensitivity of the QCM biosensor with CNT as the chemical interface was studied. Immobilization ... |
|
| IEEE 1588: An Update on the Standard and Its Application |
Jan-2007 |
20 pages |
| Authors:
John C Eidson; AGILENT TECHNOLOGIES INC SANTA CLARA CA
|
| Since the publication of version 1 of IEEE 1588 in November 2002, there has been increasing interest in and development of the technology. The standard has been adopted by a number of trade groups and is referenced in several other standards. The 1588 standard is currently being revised to include provisions for new application areas and to improve the quality of synchronization. This paper will present the technical issues under ... |
|
| Strong Optical Injection Locking of Edge-Emitting Lasers and Its Applications |
18 AUG 2006 |
158 pages |
| Authors:
Hyuk-Kee Sung; CALIFORNIA UNIV BERKELEY DEPT OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCE
|
| Semiconductor lasers are essential components that enable high-speed long-haul communication and have been widely used for various applications in photonics technology. Semiconductor lasers under optical injection locking exhibit superior performance over free-running lasers and provide useful applications not achievable through the free-running lasers. The performance of injection-locked lasers has been found to be significantly improved with stronger injection. In this dissertation, the characteristics and applications of semiconductor lasers under strong ... |
|
| Effects of Conjugation in Length and Dimension on Spectroscopic Properties of Fluorene-Based Chromophores from Experiment and Theory (Preprint) |
JUL 2006 |
38 pages |
| Authors:
Loon-Seng Tao; Paul A. Fleitz; Ruth Pachter; Kiet A. Nguyen; Joy E. Rogers; Jonathan E. Slagle; Paul N. Day; Ramamurthi Kannan; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH SURVIVABILITY AND SENSOR MATERIALS DIV/HARDENED MATERIALS
|
| A series of one-photon (OPA) absorption spectra for fluorine-based donor pi acceptor molecules is presented and spectroscopically assigned, based upon the results obtained from time-dependent density functional theory (TDDFT). The computed excitation energies were generally shown to be in good agreement with experiment, particularly when compared to results from measurements carried out in a nonpolar solvent, which were available for some molecules. The computed oscillator strengths may resolve discordant experimental ... |
|
| Electra: Repetitively Pulsed 700 J, 100 ns Electron Beam Pumped KrF Laser |
May-2006 |
5 pages |
| Authors:
J D Sethian; J L Giuliani; M F Wolford; F Hegeler; M C Myers; M Friedman; P Burns; R Jaynes; NAVAL RESEARCH LAB WASHINGTON DC PLASMA PHYSICS DIV
|
| This paper presents a brief overview of the Electra laser system and report on the most recent results. The laser system consists of an electron beam pumped main amplifier with an aperture of 30x30 cm2, an e-beam pumped 10x10 cm2 pre-amplifier, and a commercial discharge laser serving as the seed oscillator. The main amplifier, currently operated as an oscillator, has demonstrated single shot and rep-rate laser energies exceeding 700 J, ... |
|
| Optical Characterization of Thick Growth Orientation-Patterned Gallium Arsenide |
15 MAR 2006 |
69 pages |
| Authors:
Joshua W. Meyer; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
|
| Tunable laser sources in the mid-infrared (MIR) spectral range are required for several Air Force applications. Orientation patterned gallium arsenide (OPGaAs) is a promising nonlinear conversion material because it has broad transparency and can be engineered for specific pump laser and output wavelengths using quasi-phase matching techniques. This research examines the optical quality of seven OPGaAs crystal samples and explores the design of an optical parametric oscillator (OPO) device. Direct ... |
|
| Effects of Conjugation in Length and Dimension on Spectroscopic Properties of Fluorene-Based Chromophores from Experiment and Theory (Postprint) |
2006 |
14 pages |
| Authors:
Loon-Seng Tan; Paul A. Fleitz; Ruth Patchter; Kiet A. Nguyen; Joy E. Rogers; Jonathan E. Slagle; Paul N. Day; Ramamurthi Kannan; UES INC DAYTON OH
|
| A series of one-photon absorption spectra for fluorene-based donor-pi;-acceptor molecules is presented and spectroscopically assigned, based upon the results obtained from time-dependent density functional theory. The computed excitation energies were generally shown to be in good agreement with experiment, particularly when compared to results from measurements carried out in a nonpolar solvent, which were available for some molecules. The computed oscillator strengths may resolve discordant experimental values in some cases, ... |
|
| Nonlinear Dynamics and Ergodic Theory Methods in Control |
31 DEC 2005 |
15 pages |
| Authors:
Igor Mezic; CALIFORNIA UNIV SANTA BARBARA DEPT OF MECHANICAL ENGINEERING
|
| The objective of our research was to develop new control theory and dynamical systems/ergodic theory tools for the problems of active control of complex systems and control of mixing and apply the developed theoretical tools to problems of active control of mixing and particle control. |
|
| A Compact, Optically Guided, Megawatt Free-Electron Laser Amplifier for Maritime Propagation |
30 DEC 2005 |
28 pages |
| Authors:
Phillip Sprangle; Joseph Penano; Bahman Hafizi; NAVAL RESEARCH LAB WASHINGTON DC
|
| In this paper, we present a conceptual design and parameters for a compact, megawatt-class, optically guided free-electron laser (FEL) amplifier. Full-scale laser propagation simulations, including the effects of aerosols, turbulence, and thermal blooming, indicate that operating the FEL in water-vapor transmission windows, i.e., 1.045, 1.625, and 2.141 micrometer, can result in high propagation efficiencies in a maritime environment (>50% over a 5 km range). In the present design we choose ... |
|
| Numerical and Experimental Models of Dry Friction Damping in Aeroelastic Structures |
29 AUG 2005 |
7 pages |
| Authors:
Tod A. Laursen; Henri P. Gavin; Lawrence N. Virgin; DUKE UNIV DURHAM NC DEPT OF CIVIL AND ENVIRONMENTAL ENGINEERING
|
| This project has represented an integrated modeling and experimental effort, with the following objectives: 1. Experimental characterization of the dynamics of both total and partial frictional slip; 2. Development of corresponding numerical strategies for treatment of such slip between elastically compliant structural members, exploring friction models and corresponding numerical strategies; and 3. Use of the results of 1) and 2) to investigate prediction of damping characteristics in idealized frictional damping ... |
|
| Delay Loop Correction for Programmable Controllers |
24 AUG 2005 |
30 pages |
| Authors:
Jeremy R. O'Neal; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| An apparatus provides a correction value for an oscillator. At least one parameter sensor measures a system parameter influencing the oscillator. A lookup table determines a cycle adjustment value based on the system parameter. A processor joined to the oscillator implements the cycle adjustment value to correct for oscillator variation. Cycle adjustment values can be computed in both whole cycles and partial cycles through accumulated error thresholding. The parameter sensor ... |
|
| Design Techniques for Radiation Hardened Phase-Locked Loops |
23 AUG 2005 |
58 pages |
| Authors:
Anantha N. Nemmani; OREGON STATE UNIV CORVALLIS SCHOOL OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCE
|
| Spacecraft experience radiation in the course of their operation and all the electronic equipment on-board these vehicles has to be designed to withstand the effects of this radiation. This thesis describes the effects of total ionization dose (TID) and single-event transients (SET) in phase-locked loops -- an important circuit block for communication circuits and clock generation. The design of a digital phase-locked loop made tolerant to SET through redundancy and ... |
|
| All Solid-State Photomixing THZ Transmitter |
17 AUG 2005 |
60 pages |
| Authors:
Elliot R. Brown; Marie A. Celis; CALIFORNIA UNIV LOS ANGELES
|
| The goal of this project was to explore THz technologies for wider bandwidth communications and sensing for DoD systems. More specifically the objective was to develop solid state THz sources for operation in the range between 0.3 to 10 (1 millimeter to 30 micrometer) mainly for aerospace communications and atmospheric sensing; and potentially, short-range terrestrial and airborne communications and near-object analysis. The focus was on all solid-state high efficiency, high ... |
|
| Controlling High-Dimensional Chaos in Optical Devices |
22 JUL 2005 |
14 pages |
| Authors:
Daniel J. Gauthier; DUKE UNIV DURHAM NC DEPT OF PHYSICS
|
| The primary purpose of the proposed program is to develop methods for controlling and synchronizing the behavior of optical and electronic systems that display complicated behavior, such as high-dimensional chaos and turbulent-like behavior. The results of the program have the following potential applications: increasing the coherence of high-power lasers and nonlinear optical devices, developing an entirely new class of high-speed digital communications system based on chaotic elements, devising ultra-high speed ... |
|
| Optical Technologies for On-Board Processing of Microwave Signals |
13 JUL 2005 |
8 pages |
| Authors:
Michel Sotom; Benoit Benazet; Michel Maignan; Josep-Maria P. Armengol; ALCATEL SPACE TOULOUSE (FRANCE)
|
| In the last decade, optics has proved a key technology for the transmission and handling of broadband signals in telecommunication networks. Future telecom satellite payloads will have to receive, process, route and re-transmit an increasing number of microwave signals. We have been investigating how the technologies inherited from terrestrial optical communications may bring substantial improvements or provide any breakthrough in satellite sub-systems. Optical technologies may contribute to the advent of ... |
|
| Investigations of Parametric Excitation in Physical Systems |
JUN 2005 |
79 pages |
| Authors:
Michael T. Janssen; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Parametric excitation can occur when the value of a parameter of an oscillator is modulated at twice the natural frequency of the oscillator. The response grows exponentially and is only limited by a nonlinearity of the system, so large response amplitudes typically occur. However, there is no response unless the parametric drive amplitude is above a threshold value that is dictated by the damping. We investigate parametric excitation in three ... |
|
| Development and Validation of a Computational Model for Intra-Cellular Circadian Oscillators |
MAY 2005 |
31 pages |
| Authors:
David R. Weaver; BRIGHAM AND WOMEN'S HOSPITAL BOSTON MA
|
| Circadian rhythms are endogenous rhythms in physiology or behavior with a cycle length near 24 hours. Circadian rhythms are relevant to military activities because the ability of military personnel to maintain high level of cognitive performance and vigilance for long intervals is degraded by human factors, including fatigue, sleep loss and other circadian factors. Underlying circadian rhythmicity is a molecular feedback loop. This project developed mathematical models of the mammalian ... |
|
| Developing RF-Photonics Components for the Army's Future Combat Systems |
DEC 2004 |
8 pages |
| Authors:
Weimin Zhou; Steven Weiss; Christian Fazi; ARMY RESEARCH LAB ADELPHI MD
|
| The U.S. Army's Future Combat Systems are designed to support the future force with three integrated transformation phases: Concept and Technology Development, Systems Design, Demonstration and Production. The Concept and Technology Developments phase is creating new challenges and opportunities for radio frequency and microwave applications in global positioning, navigation, timing, communications, improved radar target detection, and new forms of combat identification. The merging of photonics and microwave electronics may revolutionize ... |
|
| Beam Steering by Lag Synchronization in Ultra-Wide Bandwidth, Chaotic Arrays |
DEC 2004 |
3 pages |
| Authors:
Ned J. Corron; Jonathan N. Blakely; Shawn D. Pethel; ARMY AVIATION AND MISSILE COMMAND REDSTONE ARSENAL AL MISSILE RESEARCH DEVELOPMENT AND ENGINEERING CENTER
|
| We introduce a new method for beam steering in ultra-wide bandwidth arrays. The approach avoids the need for tunable microwave delays by using lag synchronization in a linear array of locally coupled chaotic oscillators. Steering is controlled by tuning the natural frequency of the oscillators and is analytically equivalent to first order to using explicit delay elements. Using chaotic rf circuits oscillating at tilde20MHz, we show both lag and lead ... |
|
| An Information-Theoretic Basis for Designing Efficient Signal Sources Using Unstable Nonlinear Electronic Oscillators |
DEC 2004 |
3 pages |
| Authors:
Shawn D. Pethel; Ned J. Corron; Krishna Myneni; ARMY AVIATION AND MISSILE COMMAND REDSTONE ARSENAL AL
|
| We review recent progress at AMRDEC in establishing an information- theoretic basis for designing efficient signals sources using unstable nonlinear electronic oscillators. Such oscillators appear to be generally useful in ranging and communications, particularly when used in a chaotic mode. Their primary advantages lie in their tremendous natural bandwidth and simplicity of construction. We show that the dynamics of these novel devices can be modeled as an information source of ... |
|
| Ultrashort Pulse Propagation in Negative Index Materials: From Negative Refraction to Nonlinear Pulse Propagation |
DEC 2004 |
3 pages |
| Authors:
Michael Scalora; Mark J. Bloemer; Charles M. Bowden; Giuseppe D'Aguanno; Nadia Mattiucci; TIME DOMAIN CORP HUNTSVILLE AL
|
| Negative index materials (NIMs) hold the promise for super lensing of electromagnetic radiation for applications in radar, THz, and possibly at optical frequencies. We have developed a new vector pulse propagation method that we use to study the electrodynamics of negative index materials (NIMs). Although numerous papers have been published on the unusual properties of NIMs, we are the first to apply a propagation model to the problem. As we ... |
|
| Employing Noisy Environments to Support Quantum Information Processing |
14 SEP 2004 |
5 pages |
| Authors:
Martin B. Plenio; Susana F. Huelga; IMPERIAL COLL OF SCIENCE TECHNOLOGY ANDMEDICINE LONDON (UNITED KINGDOM)
|
| In this project we have investigated the use of noise to support the generation of noise and coherent quantum information processing. We have presented schemes to this effect firstly in quantum optical settings (optical cavity QED, ion traps) and then in condensed matter environments (nano- mechanical oscillators and SQUID technologies). Abstract theoretical investigations into the usefulness of noise for quantum information processing have been carried out. The work on this ... |
|
| MTIE and TDEV Analysis of Unevenly Spaced Time Series Data and its Application to Telecommunications Synchronization Measurements |
SEP 2004 |
|
| Authors:
Mingfu Li; Hsin-Min Peng; Chia-Shu Liao; TELECOMMUNICATION LABS TAOYUAN (TAIWAN)
|
| In this work, we investigated the effect of uneven data spacing on the computations of MTIE and TDEV. We evaluated MTIE and TDEV with unevenly spaced data having the five different power-law noise types. Each simulated data set had 3600 evenly spaced data points spaced one second apart. In the next step, we removed data points for each file according to the parameter p. Each data point in a file ... |
|
| Modelling the Control of the Space Charge Dynamics in a System of Two Electrical Glow Discharge Plasma |
07 APR 2004 |
2 pages |
| Authors:
Cristina Stan; C. P. Cristescu; D. Alexandroaei; UNIVERSITY OF POLITEHNICA BUCHAREST (ROMANIA)
|
| This work present a comparative study between the experimental data on the system of two electrical glow discharge plasma and the simulated data from a system of ordinary differential equations based on van der Pol oscillators with reference to the control of the space charge dynamics. |
|
| Dynamical Behavior of Coupled Chaotic Oscillators Including Phase Synchronization and Complete Synchronization in Plasma |
07 APR 2004 |
2 pages |
| Authors:
Takao Fukuyama; Yoshinobu Kawai; KYUSHU UNIV FUKUOKA (JAPAN)
|
| The dynamical behavior of two coupled chaotic oscillators caused by the current-driven ion acoustic instability is experimentally studied. It is found that when two oscillators (two unstable waves) are interacting, and the dc potential applied to either of the two oscillators is varied gradually while maintaining coupling, the two oscillators synchronize in a certain region. |
|
| International van der Ziel Symposium on Quantum 1/f, 1/f Noise and Other Low Frequency Fluctuations, Mainly in GaN, Quantum or Nanometric Devices (9th) Held in Richmond, Virginia on August 2-4, 2002 |
10 FEB 2004 |
12 pages |
| Authors:
Peter H. Handel; MISSOURI UNIV-ST LOUIS
|
| The "19th International van der Ziel Symposium on Quantum l/fl/f Noise and Other Low Frequency Fluctuations, mainly in GaN, Quantum or Nanometric Devices" has brought substantial progress both in fundamental quantum l/f noise theory, and in the application to GaN devices and oscillators. The new developments were obtained in the US, in Japan and in Europe, with the top specialists in this new quantum l/f field participating from 3 continents, ... |
|
| The Hannay-Berry Phase of the Vibrating Ring Gyroscope |
2004 |
26 pages |
| Authors:
Sean B. Andersson; P. S. Krishnaprasad; MARYLAND UNIV COLLEGE PARK
|
| In an analysis published in 1890, G.H. Bryan investigated the retrograde precession of the nodal points in a vibrating, rotating shell and wrote down a formula relating the rate of precession to the rate of rotation. This effect has been utilized in the design of various vibratory gyroscopes including modern MEMS-based devices. Existing analyses model these systems with a pair of harmonic oscillators coupled through the Coriolis force (the normal ... |
|
| Proceedings of the Annual Precise Time and Time Interval (PTTI) Systems and Applications Meeting (35th) (CD-ROM) |
2004 |
|
| Authors:
NAVAL OBSERVATORY WASHINGTON DC
|
| ELECTRONIC FILE CHARACTERISTICS: 98 files; Adobe Acrobat (.PDF). PHYSICAL DESCRIPTION: 1 computer laser optical disc (CD-ROM); 4 3/4 in.; 41.5 MB. SYSTEMS DETAIL NOTE: ABSTRACT: This document is a compilation of technical papers presented at the 35th Annual Precise Time and Time Interval (PTTI) Systems and Applications Meeting held 2-4 December 2003 at the Hilton Resort on Mission Bay at San Diego, Calif. Paper categories: - Recent developments in rubidium, ... |
|
Reports by Keyword(s)
OSCILLATORS
