| Lines of Energy Deposition for Supersonic/Hypersonic Temperature/ Drag-Reduction and Vehicle Control |
06-Oct-2009 |
15 pages |
| Authors:
Michael P Reilly; George H Miley; Kevin Kremeyer; AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
|
 | Lines of energy are deposited ahead of supersonic and hypersonic vehicles in order to create a low-density channel, through which a vehicle can travel with dramatically reduced drag. Temperature and pressure are both also reduced on the front surfaces of the vehicle, while density and pressure are increased at the vehicle base. When applied off-center, this technique can be used to control the vehicle, employing the entire body as the ... |
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| High-Velocity Impact of Low-Density Projectiles on Structural Aluminum Armor |
Sep-2009 |
14 pages |
| Authors:
B R Sorensen; K D Kimsey; B M Love; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
|
| The US Army Research Laboratory has been studying the impact physics of low-density projectiles on urban and light-armor structures for use in electro-magnetic cannons. In this report, results of low-aspect ratio projectiles of nylon, aluminum and steel impacting aluminum armor at velocities above 2000 m/s will be presented. Both computational solid mechanics and analytic modeling techniques were used to supplement experiments to derive a toolkit for assessing target response and ... |
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| Near-Infrared Collisional Radiative Model for Xe Plasma Electrostatic Thrusters: The Role of Metastable Atoms |
Aug-2009 |
10 pages |
| Authors:
Yu-Hui Chiu; Rajesh Srivastava; Rainer A Dressler; Oleg Zatsarinny; Klaus Bartschat; Lalita Sharma; AIR FORCE RESEARCH LAB HANSCOM AFB MA SPACE VEHICLES DIRECTORATE
|
| Metastable Xe atoms play an important role in the collisional radiative processes of dense xenon plasmas, including those of electric thrusters for space vehicles. Recent measurements and calculations of electron-excitation processes out of the metastable state have allowed for the development of a collisional radiative model for Xe near-infrared (NIR) emissions based on the population of the metastable level through radiative transitions, and based on depopulation through electron-impact excitation. A ... |
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| Structural Performance of Aluminum and Stainless Steel Pyramidal Truss Core Sandwich Panels |
Jul-2009 |
22 pages |
| Authors:
Aristedes Yiournas; Yellapu Murty; Kevin J Doherty; Jordan A Wagner; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
|
| Future lightweight military vehicles will demand increasingly mass-efficient structures to satisfy design requirements such as increased mobility and survivability. One possible family of lightweight structures entails sandwich panels consisting of solid facesheets and a low-density core. The sandwich structures can provide both structural strength and stiffness, with load-bearing potential. In this study, sandwich panels consisting of metallic facesheets and a pyramidal truss core manufactured from either 6061-T6 aluminum or 316L ... |
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| Growth of Low Defect Density Gallium Nitride (GaN) Films on Novel Tantalum Carbide (TaC) Substrates for Improved Device Performance |
May-2009 |
34 pages |
| Authors:
M A Derenge; K A Jones; K W Kirchner; T S Zheleva; R D Vispute; ARMY RESEARCH LAB ADELPHI MD SENSORS AND ELECTRON DEVICES DIRECTORATE
|
| To potentially improve device performance, we attempted to grow gallium nitride (GaN) films with better crystalline quality (fewer mismatch dislocations) using a tantalum carbide (TaC) substrate, which is more closely lattice matched to GaN than currently used substrates. We created the TaC substrate, using pulse laser deposition (PLD) of TaC onto (0001) SiC substrates at tilde 1000 deg C, and grew GaN films, using metal organic chemical vapor deposition (MOCVD). ... |
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| Modern Nondestructive Test Methods for Army Ceramic Matrix Composites |
Oct-2008 |
18 pages |
| Authors:
Douglas J Strand; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
|
| As composites have developed and matured, the nondestructive testing (NDT) methods needed to characterize and maintain them have also developed and matured. The purpose of this report is to examine the newer methods of NDT, which may be applicable to some of the new composite materials being used for U.S. Army applications. Ceramic matrix composites (CMC) are potentially good high-temperature structural materials because of their low density, high elastic moduli, ... |
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| Two-Dimensional Electron Gas in Strained Silicon for Studying Ultra-Low Energy Electronic Processes |
10-Mar-2008 |
18 pages |
| Authors:
Ya-Hong Xie; Daniel Tsui; CALIFORNIA UNIV LOS ANGELES DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| The proposed research focuses on the fabrication of high mobility 2D electron gases or low density for the understanding of correlated electron behavior under extreme conditions: low temperature and high magnetic field. The experimental efforts are in 3 related topics: (1) fabricate 2DES in strained Si with the highest achievable electron mobility; (2) fabricate 2DES in strained Si with low electron density; and (3) explore alternative approaches for fabricating strained ... |
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| An Analysis of Magnesium Alloy AZ31B-H24 for Ballistic Applications |
DEC 2007 |
20 pages |
| Authors:
Tyrone L. Jones; Matthew S. Burkins; William A. Gooch; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
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| The U.S. Army Research Laboratory is developing a ballistic specification for the use of magnesium alloy AZ31B-H24 as armor on Army platforms. Data were generated for a range of thicknesses of this magnesium alloy, 0.25 to 4 inches, with the use of five different projectiles. The magnesium performance is parametrically quantified on an equivalent areal density to meet the aluminum alloy 5083-H131, which means a mature, well defined, low-density metal. ... |
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| Turbulence Instrumentation for Stratospheric Airships |
01-Sep-2007 |
83 pages |
| Authors:
Mark L Duell; Lawrence M Saupe; Brent E Barbeau; Kris D Robinson; George Y Jumper; AIR FORCE RESEARCH LAB HANSCOM AFB MA SPACE VEHICLES DIRECTORATE
|
| Both commercial and high altitude aircraft such as the U-2 may encounter turbulence in flight. The turbulence seems to be associated with buoyancy waves generated by flow over mountains that can break into turbulence. The exact nature of the wave breaking is not fully understood, and forecast models need to be examined to determine their ability to forecast turbulence. The High Altitude Airship is designed to investigate these phenomena. In ... |
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| Heat Release Rates for Shipboard Dry Goods Storage Space Materials |
04 MAY 2007 |
50 pages |
| Authors:
John B. Hoover; Hung Pham; Frederick W. Williams; NAVY TECHNOLOGY CENTER FOR SAFETY AND SURVIVABILITY WASHINGTON DC
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| Compartment-scale tests were conducted to evaluate the fire performance of items found in typical dry goods storage spaces on DDG-51 class destroyers. Packaging materials included cardboard boxes, Kraft paper and polyethylene bubble wrap. Toilet paper, paper towels, and copy paper were used as representative flammable stock items. Heat release rate (HRR) was measured by oxygen consumption calorimetry. It was found that both the nature of the material and the packing ... |
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| Bone Growth, Mechanical Stimulus and IGF-1 |
01 OCT 2006 |
51 pages |
| Authors:
Vicente Gilsanz; CHILDREN'S HOSPITAL LOS ANGELES CA
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| The purpose of this study was to assess the potential for brief periods of low magnitude high frequency mechanical stimulation signals in the musculoskeletal system. The major findings were that short bouts of extremely low-level mechanical signals, several orders of magnitude below that associated with vigorous exercise, increased bone and muscle mass in the weight bearing skeleton of young adult females with low bone density. Ultimately, this information could be ... |
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| Development of Low Density CaMg-A1-Based Bulk Metallic Glasses (Preprint) |
OCT 2006 |
18 pages |
| Authors:
O. N. Senkov; J. M. Scott; D. B. Miracle; UES INC DAYTON OH
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| Low density Ca-Mg-Al-based bulk metallic glasses containing additionally Cu and Zn, were produced by a copper mold casting method as wedge-shaped samples with thicknesses varying from 0.5 mm to 10 rom. The compositions of the alloys were selected using recently developed specific criteria for glass formation. A structural assessment using the efficient cluster packing model was also applied and showed a good ability to represent these glasses. Thermal properties of ... |
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| Experimental and Numerical Study of Spacecraft Contamination Problems Associated With Gas and Gas-Droplet Thruster Plume Flows |
17 APR 2006 |
219 pages |
| Authors:
Mikhail S. Ivanov; RUSSIAN ACADEMY OF SCIENCES NOVOSIBIRSK INST OF THEORETICAL AND APPLIED MECHANICS
|
| The project consists of two large parts. The first part is the study of plume flows escaping into vacuum, and the second part deals with gasdroplet flows. These two parts are united by a common area of research, namely, contamination problems of space station surfaces due to thruster firing. The objective of the first part is accurate prediction of force and heat loads and contamination due to interaction of thruster ... |
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| Void Detection in Foam With Knit Lines Using THz Pulse Interrogation |
04 FEB 2006 |
11 pages |
| Authors:
H. T. Banks; N. L. Gibson; NORTH CAROLINA STATE UNIV AT RALEIGH CENTER FOR RESEARCH IN SCIENTIFIC COMPUTATION
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| We model electromagnetic interrogation of a polyurethane foam using the TE mode of the 2D Maxwell's equations reduced to the wave equation for a fixed frequency in the THz regime. The foam block target contains knit lines which are modeled by modifying the speed of propagation, i.e., by altering the index of refraction. We describe our efforts to estimate the dielectric constant in the knit lines, as well as in ... |
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| Embedding Luminescent Nanocrystals in Silica Sol-Gel Matrices |
2006 |
|
| Authors:
Lindsey M. Sorensen; FLORIDA STATE UNIV TALLAHASSEE COLL OF ARTS AND SCIENCES
|
 | We have synthesized stable, highly luminescent silica xerogels as well as optically transparent, stable aerogels that were embedded with 2.5 nm and 6 nm CdSe and 6 nm InP quantum dots. By capping the quantum dot with 3-aminopropyltriethoxysilane, a dot is able to condense within the structure of a forming silica gel. This network keeps the quantum dot in place during the solvent exchange procedure necessary to form low-density silica ... |
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| The Effect of Aerodynamic Surfaces Versus Thrust Maneuvers on Reentry Vehicles |
SEP 2005 |
85 pages |
| Authors:
Meredith M. Albrecht; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
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| This research effort analyzes the effect of aerodynamic surfaces versus thrust maneuvers on a reentry vehicle. At high altitudes the effect of aerodynamic surfaces on the reentry vehicle is small due to low atmospheric density; however as the vehicle reaches lower altitudes a lift maneuver is very successful in deflecting the vehicle and creating a large impact footprint. When a continuous thrust maneuver is input in the place of a ... |
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| Polymer-Carbon Nanotube Composites, A Literature Review |
24 AUG 2005 |
|
| Authors:
Trisha A. Huber; DEFENCE RESEARCH AND DEVELOPMENT ATLANTIC DARTMOUTH (CANADA)
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| Carbon nanotubes were first discovered in 1991, and quickly became the focus of much research activity, due to their exceptional electrical, mechanical, and thermal properties. The extraordinary properties arise from the unique tubular structure; the nanotubes may be envisioned as rolled up graphene sheets that are on the order of a nanometer in diameter, and microns in length, resulting in high aspect ratios (length/diameter). In addition to the many applications ... |
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| Studies on Impingement Effects of Low Density Jets on Surfaces - Determination of Shear Stress and Normal Pressure |
13 JUL 2005 |
|
| Authors:
Sarith P. Sathian; Job Kurian; INDIAN INST OF TECH MADRAS DEPT OF AEROSPACE ENGINEERING
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| This paper presents the results of the Laser Reflection Method (LRM) for the determination of shear stress due to impingement of low-density free jets on flat plate. For thin oil film moving under the action of aerodynamic boundary layer the shear stress at the air-oil interface is equal to the shear stress between the surface and air. A direct and dynamic measurement of the oil film slope is measured using ... |
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| The Far-Infrared Emission Line and Continuum Spectrum of the Seyfert Galaxy NGC 1068 |
10 APR 2005 |
15 pages |
| Authors:
Luigi Spinoglio; Matthew A. Malkan; Howard A. Smith; Eduardo Gonzalez-Alfonso; Jacqueline Fischer; NAVAL RESEARCH LAB WASHINGTON DC
|
| We report on the analysis of the first complete far-infrared spectrum (43 197 m) of the Seyfert 2 galaxy NGC 1068 as observed with the > Long Wavelength Spectrometer (LWS) on board the Infrared Space Observatory (ISO). In addition to the seven expected ionic fine-structure emission lines, the OH rotational lines at 79, 119, and 163 m were all detected in emission, which is unique among galaxies with full LWS ... |
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| Small Molecules That Suppress IGF-Activated Prostate Cancers |
APR 2005 |
8 pages |
| Authors:
Motonari Uesugi; BAYLOR COLL OF MEDICINE HOUSTON TX
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| Elevated serum levels of insulin-like growth factor 1 (IGF1) have been found in prostate cancer patients, and IGF1-related signal transduction is thought to be an important factor in the development of prostate cancers. The goals of this project are to discover small organic molecules that suppress ICE-activated prostate cancers by cell-based screening and to analyze their action mechanisms. In the first year of funding, we discovered, from our collection of ... |
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| Analysis of High-Speed Vessels for Seventh Fleet Logistics Support |
MAR 2005 |
114 pages |
| Authors:
Eric A. Morgan; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF OPERATIONS RESEARCH
|
| Commander, Logistics Group, Western Pacific (COMLOGWESTPAC) is concerned with the delivery of high priority material, ordnance, and passengers to U.S. Navy ships due to a very large operations area and limited Combat Logistics Force (CLF) assets. High-speed vessels (HSVs) may have the potential to improve the delivery of these materials when used to complement existing logistics shuttle ships. This thesis quantifies current levels of traditional naval logistics support and provides ... |
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| Focus Paper 1 - What Is Unique About Small Scale Contingency (SSC) Analysis? |
01 FEB 2005 |
|
| Authors:
DEFENCE EVALUATION AND RESEARCH AGENCY FARNBOROUGH (UNITED KINGDOM)
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| This paper has been commissioned by the NATO SAS-027 group that was recently established to examine the analysis of Small Scale Contingencies (SSC). The aim of the paper is to identify the differences between SSC analysis and existing operational research activities. For reference SSC are characterized as low density low (military) casualty operations involving 100,000 personnel or less. Peacekeeping peace enforcement humanitarian aid, counter-insurgency military aid to civil authorities and ... |
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| Plasma Transferred Arc Deposition of Beryllium (Preprint) |
2005 |
14 pages |
| Authors:
K. Hollis; B. Bartram; R. Strom; J. Withers; J. Massarello; LOS ALAMOS NATIONAL LAB NM
|
| The exceptional properties of beryllium (Be) including low density and high elastic modulus, make it the materials of choice in many defense and aerospace applications. however, health hazards associated with Be material handling limit the applications that are suited for beryllium use. Innovative solutions that enable continued use of Be in critical applications while addressing worker health concerns are highly desirable. Plasma Transferred Arc solid freeform fabrication is being evaluated ... |
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| A Novel Processing Technique for Growing Bulk Gallium Nitride Ingots From Gallium Melt |
DEC 2004 |
47 pages |
| Authors:
Mahendra K. Sunkara; Hongwei Li; Hari Chandrasekaran; Sreeram Vaddiraju; LOUISVILLE UNIV KY DEPT OF CHEMICAL ENGINEERING
|
| In summary, a new process is being developed to obtain free standing, large area, near single crystal quality GaN flake (highly oriented GaN films) promising as native substrates for homoepitaxial growth of device quality, low- defect density GaN layers. However, the experiments to date resulted only in GaN flakes of sizes around 1 sq cm due to the following reasons: (a) the wetting and flow of molten Ga affected the ... |
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| Quantifying Channelized Submarine Depositional Systems From Bed to Basin Scale |
SEP 2004 |
|
| Authors:
William J. Lyons III; MASSACHUSETTS INST OF TECH CAMBRIDGE
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| In this thesis, I employ 3-D seismic data and outcrops to study turbidites from bed to basin scales. Using seismic data from the Fisk Basin, Gulf of Mexico, I develop a method to estimate the time frame over which sedimentation and subsidence come into equilibrium within a basin. Basin- specific equilibrium times are found to range from 4.6x10(exp 5) years to 2. 0x10(exp 5) years, depending upon depositional architecture. Such ... |
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| High-Speed and Low-Power VLSI Error Control Coders |
SEP 2004 |
9 pages |
| Authors:
Keshab K. Parhi; MINNESOTA UNIV MINNEAPOLIS DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
|
| This final report describes our research results obtained during the period August 1, 2001 to July 31, 2004 by support from the ARO grant "High Speed and Low Power VLSI Error Control Coders" (ARO Grant Number:DA/DAAD19-01-1- 0705(42436-CI). Research results obtained in the areas of architectures for product turbo coders (based on component codes such as BCH codes, extended Hamming codes, and single parity check codes), space-time block codes, low- density ... |
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| High Speed Network Access to the Last-Mile Using Fixed Broadband Wireless |
MAR 2004 |
119 pages |
| Authors:
Nikolaos Fougias; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Despite the increase in the demand for high speed Internet services, the last-mile solutions currently available neither are inexpensive enough to attract the majority of the population, nor are they available in low density populated areas, This thesis examines Fixed Broadband Wireless (FBW) as an alternative technology to the current last-mile solutions, The analysis shows that LMDS and MMDS are the most promising emerging FBW technologies and that they are ... |
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| Understanding Injection Into High Pressure Supercritical Environments |
09 OCT 2003 |
37 pages |
| Authors:
B. Chehroudi; D. Talley; W. Mayer; R. Branam; J. J. Smith; AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
|
| This paper summarizes the results of systematic research programs at both the DLR and the AFRL which began nearly ten years ago. The research is aimed at improving the understanding of atomization, mixing, and combustion processes associated with coaxially injected liquid propellant rocket engines. Cold flow studies are imperative for investigations without the complexities introduced with combustion. Initial studies utilized liquid nitrogen (LN2) without a co-flow stream into a chamber ... |
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| Plasma-Propellant Interactions |
OCT 2003 |
49 pages |
| Authors:
W. G. Proud; P. Kalafatis; M. J. Gifford; M. W. Greenaway; C. Dobson; CAMBRIDGE UNIV (UNITED KINGDOM) DEPT OF PHYSICS
|
| In one series of experiments, see Sections 1-6, plasma/propellant interactions were studied. Four different propellants (see Section 3) were placed at chosen distances from the discharge. The discharges were made either in a high pressure vessel or at ambient pressures. In some cases, the propellant was at room temperature and in others at elevated temperature. Additionally, attempts were made to quench burning propellant. Optical and Environmental Scanning Electron Microscopy (ESEM), ... |
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| Deep Ultra-Violet (DUV) Light Emitting Diodes |
30 AUG 2003 |
14 pages |
| Authors:
Deepika Singh; Steve Pearton; SINMAT INC GAINESVILLE FL
|
| Problems to Overcome: The main problem to overcome is to develop a commercially and economically viable method to synthesize and process high crystalline quality diamond films for applications such as DUV LEDs and solar- blind detectors. Scientific Approach: The scientific approach is the homoepitaxial deposition on diamond films on large area (50 - 100 sq mm) synthetic Type Ib diamond substrates. Although type Ib diamond substrates have a high nitrogen ... |
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| Study of Hydrogen As An Aircraft Fuel |
JUN 2003 |
69 pages |
| Authors:
J. S. Ciaravino; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF AERONAUTICS AND ASTRONAUTICS
|
| The conversion to hydrogen as a naval aviation fuel would allow for independence on fuel cost and supply, as hydrogen is globally accessible. The biggest obstacle to using hydrogen is its very low density, a property that even combined with hydrogen's high heat of combustion still results in very large fuel tanks. Liquid hydrogen (LH2) with its higher density would still require a larger volume than kerosene for the aircraft ... |
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| Internal Energy Mode Relaxation in High Speed Continuum and Rarefied Flows |
07 MAY 2003 |
20 pages |
| Authors:
Eswar Josyula; Dean C. Wadsworth; ENGINEERING RESEARCH AND CONSULTING INC(ERC INC) EDWARDS AFB CA
|
| The presence of shock waves in high speed flow of a polyatomic gas presents considerable difficulties for accurate numerical simulation of the flowfield. The shock wave redistributes the high kinetic energy of the oncoming flow into various internal energy modes, which relax relatively slowly, leading to significant chemical and thermal nonequilibrium the stagnation region. In the gas kinetic description, intermolecular collisions change the translational, rotational, vibrational, and electronic energies of ... |
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| Computing Surface Charging in the Auroral Environment Using NASCAP-2K |
MAY 2003 |
36 pages |
| Authors:
V. A. Davis; M. J. Mandell; G. A. Jongeward; SCIENCE APPLICATIONS INC SAN DIEGO CA
|
| At high latitudes, during periods of auroral activity, low-earth polar orbiting spacecraft can pass through a region of intense, energetic electron fluxes and low thermal plasma density. The Nascap-2k computer code has been extended to model spacecraft surface charging in the auroral region. This report documents how to use the new capabilities, the equations used to describe the environment and its interactions with the surfaces, and the validation of the ... |
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| Electric Micropropulsion |
08 JAN 2003 |
6 pages |
| Authors:
Manuel Martinez-Sanchez; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF AERONAUTICS AND ASTRONAUTICS
|
| Results from two research are report in this paper: 1) fully kinetic modeling of the plasma in Hall thrusters, and 2) fluid modeling plus time-of- flight experiments on cone-jet colloid emitters for micropropulsion. The objective of the research in task 1 is to develop computational techniques to calculate the electron distribution function in low density plasmas with geometries and parameters which are realistic for application to Hall and ion thrusters. ... |
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| Use of OCR for Rapid Construction of Bilingual Lexicons |
2003 |
18 pages |
| Authors:
Burcu Karagol-Ayan; David Doermann; Bonnie J. Dorr; MARYLAND UNIV COLLEGE PARK INST FOR ADVANCED COMPUTER STUDIES
|
| This paper describes an approach to analyzing the lexical structure of OCRed bilingual dictionaries to construct resources suited for machine translation of low-density languages, where online resources are limited. |
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| Tensile Deformation and Fatigue Crack Growth in Bulk Nanocrystalline A1-7.5Mg |
2003 |
6 pages |
| Authors:
P. S. Pao; H. N. Jones; S. J. Gill; C. R. Feng; NAVAL RESEARCH LAB WASHINGTON DC MATERIAL SCIENCE AND TECHNOLOGY DIV
|
| The fatigue crack growth kinetics and tensile deformation of bulk nanocrystalline Al-7.5Mg were investigated. Nanocrystalline particulates were first prepared by mechanically ball milling spray atomized Al-7.5Mg powders in liquid nitrogen. These particulates were then degassed, consolidated by hot isostatic pressing and extruded into rods. Bulk nanocrystalline Al-7.5Mg has significantly higher fatigue crack growth rates and lower fatigue crack growth thresholds than those of ingot-processed 7050-T7451. The fatigue crack growth thresholds ... |
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| Bonded Fly Ash: A Low-Energy Replacement for Portland Cement Concrete to Improve Resistance to Chem-Bio Intrusion |
OCT 2002 |
13 pages |
| Authors:
Mark Anderson; Dov Dover; APPLIED RESEARCH ASSOCIATES INC PANAMA CITY FL
|
| The paper discusses the background of cementitious materials, and generally compares natural (Pozzolanic) cement to manufactured (Portland) cement. Fly ash is discussed as a common Pozzolan, and in particular, the low- energy requirement for fly ash as compared to Portland cement. Also, photomicrographs of fly ash particles and of chemically bonded fly ash are compared to a photomicrograph of Portland cement particles and a photograph of Portland cement concrete to ... |
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| Simulation of the Optical Properties of Atmospheric Aerosols in the Planetary Boundary Layer (BPL) |
SEP 2002 |
|
| Authors:
Rosalba Saija; MESSINA UNIV (ITALY)
|
| We report in this paper the relevant results obtained for the calculation and the retrieving of the optical properties of the particles that can constitute the atmospheric aerosols. In the first section we present the preliminary results of computations of the optical properties (extinction and backscattering) for low density dispersions of particles with an irregular shape. These particles are modelled as clusters of spheres and the calculated Lidar ratios will ... |
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| Practical Limits on Positron Accumulation and the Creation of Electron-Positron Plasmas |
24 JUN 2002 |
14 pages |
| Authors:
R. G. Greaves; C. M. Surko; FIRST POINT SCIENTIFIC INC AGOURA HILLSCA
|
| The tasks of accumulating large numbers of positrons, creating high-density positron plasmas, and confining electron-positron plasmas present a number of technical challenges. Some practical considerations and limitations of common confinement schemes are discussed. A novel design for a multi-cell Penning-Malmberg trap is proposed for the accumulation of large number of positrons (e.g.>10(exp12) and Tau ^0.5 eV). A method is described to create a low-density, electron-positron plasma (e.g., n ^ 10(exp7) ... |
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| Classical Collisional Diffusion in the Annular Penning Trap |
24 JUN 2002 |
9 pages |
| Authors:
Qudsia Quraishi; Scott Robertson; Bob Walch; COLORADO UNIV AT BOULDER DEPT OF PHYSICS
|
| Transport of particles and energy by cross-field diffusion has been studied in the annular Penning trap in which a nonneutral plasma of electrons is contained between concentric cylinders. At densities sufficiently low ( |
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| Test and Analysis of Composite Sandwich Panels With Impact Damage |
MAR 2002 |
67 pages |
| Authors:
R. C. Moody; Anthony J. Vizzini; MARYLAND UNIV COLLEGE PARK DEPT OF AEROSPACE ENGINEERING
|
| Flat and curved (1.07-m radius) sandwich panels of various widths (83, 152, and 305 mm) were impacted and loaded uniaxially in compression until failure. Test results indicated that the width and curvature of the specimen had little effect on the ultimate strength. However, the point at which the impact damage grew as indicated by a nonlinear strain response was a function of The width and curvature of the specimen. An ... |
|
| Inversion Channel MOSFETs in 3C-SiC on Silicon |
2002 |
7 pages |
| Authors:
Jianwei Wan; M. A. Capano; M. R. Melloch; James A. Cooper Jr.; PURDUE UNIV LAFAYETTE IN SCHOOL OF ELECTRICAL AND COMPUTER ENGINERING
|
| As a substrate material, single crystal SiC wafers are commercially available in diameters up to 75 mm, whereas silicon wafers a?e available in diameters of 200-300 mm. SiC wafers remain quite expensive compared to silicon, and contain%troublesome densities of micropipes that limit the yield of large devices. In the past, several groups have attempted to circumvent these problems by fabricating devices in 3C-SiC films grown epitaxially on silicon substrates, with ... |
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| Contractors on the Battlefield: A Case Study of the Airborne Reconnaissance Low (ARL) Life-Cycle Logistics Support Contract - March 2000 Through August 2001 |
DEC 2001 |
96 pages |
| Authors:
Henrietta H. Maples; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Contractors have consistently contributed to successful military operations. The goal of this thesis is to provide an assessment of the life- cycle logistics support contract for Airborne Reconnaissance Low (ARL). The ARL performs a reconnaissance mission in support of other than military missions. this is not 'war' in the traditional sense of the word; however, every deployment presents unique problems associated with the location and the mission. Based on the ... |
|
| Risk Factors for Osteoporosis and Oral Bone Loss in Postmenopausal Women |
OCT 2001 |
21 pages |
| Authors:
Jean Wactawski-Wende; STATE UNIV OF NEW YORK AT BUFFALO AMHERST
|
| The overall purpose of this study is to determine the relationship between skeletal and oral bone density, identify factors influencing bone loss, and determine the relationship between osteoporosis and oral bone loss, periodontal disease and tooth loss. We hypothesize that reduction in bone density leading to osteoporosis, plays a significant role in increasing susceptibility to destructive periodontitis and tooth loss. Sensitive and accurate measures of skeletal and oral bone mineral ... |
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| Shear Stress and Sediment Resuspension in Canopy-and Meadow-Forming Submersed Macrophyte Communities |
JUN 2001 |
17 pages |
| Authors:
William F. James; John W. Barko; Malcolm G. Butler; ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS
|
| This technical note examines the impact of differing biomass levels and plant architectural types on bottom shear stress and sediment resuspension in shallow systems. Studies were conducted at Lake Christina, Minnesota, in late August-early September 1998, when macrophyte biomass levels exceeded 200 g/m2 and in June 2000, when biomass was greatly reduced (<20 g/m2). The macrophyte beds that were studied were dominated by either a canopy-forming species (Myriophyllum sibiricum) or ... |
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| Application of Aluminum Foam for Stress-Wave Management in Lightweight Composite Integral Armor |
MAY 2001 |
54 pages |
| Authors:
Bruce K. Fink; Travis A. Bogetti; Bazle Gama; John W. Gillespie Jr.; Chin-Jye Yu; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
|
| Closed-cell aluminum foam offers a unique combination of properties such as low density, high stiffness, strength, and energy absorption that can be tailored through design of the microstructure. During ballistic impact, the foam exhibits significant nonlinear deformation and stress-wave attenuation. Composite structural armor panels containing closed-cell aluminum foam are impacted with 20-mm fragment-simulating projectiles (FSP). One-dimensional plane strain finite element analysis (FEA) of stress-wave propagation is performed to understand the ... |
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| Assessment of Two Electro-Rheological Fluids for Use in Recoil Abatement Applications |
MAY 2001 |
68 pages |
| Authors:
Laszlo J. Kecskes; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
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| The electrical and rheological properties of two state-of-the-art electro-rheological (ER) fluids have been evaluated from 0 to 60 deg C, using a unique constant-stress viscometer. The measurements were performed at the facilities of ER Fluid Developments, Ltd. (ERFD), a small British company located in Sheffield, United Kingdom, that specializes in developing and marketing ER fluid-based technology. In addition to these measurements, the response time of the fluids was determined using ... |
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| Reinforced Metal Structural Jackets for Advanced Gun Barrels |
26 APR 2001 |
14 pages |
| Authors:
James M. Burnett; Horst Gigerenzer; Eric Pennell; Craig Dampier; TRITON SYSTEMS INC CHELMSFORD MA
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| High performance reinforced metals are being developed that have a series of desirable properties for gun barrel structural jacket applications. The two materials of interest are reinforced aluminum and reinforced titanium. Both of these materials possess very high strength, high fatigue resistance, high temperature resistance, and low density. Ongoing work to apply these promising materials to high performance gun barrels includes diffusion bonding to specified liners, material characterization, development of ... |
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| Modeling of Pem Fuel Cell Systems Including Controls and Reforming Effects for Hybrid Automotive Applications |
2001 |
262 pages |
| Authors:
Daisie D. Boettner; OHIO STATE UNIV COLUMBUS
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| Due to the nature of fuel cell reactions, fuel cells have the potential of being more fuel efficient while generating fewer harmful emissions than conventional automotive power systems. Additionally, by hybridizing a fuel cell system with a battery, opportunities may exist for significantly improving overall performance. This study develops models for a stand-alone Proton Exchange Membrane (PEM) fuel cell stack, a direct-hydrogen fuel cell system including auxiliaries, and a methanol ... |
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| The 24th International Conference on Phenomena in Ionized Gases Held in Warsaw, Poland on July 11-16, 1999 |
11 AUG 2000 |
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| Authors:
INSTITUTE OF PLASMA PHYSICS AND LASER MICROFUSION WARSAW (POLAND) LASER PRODUCED PLASMA PHYSICS DEPT
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| The XXIV International Conference on Phenomena in Ionized Gases is a subsequent conference in the series of meetings being organized biennially with participation of 400-500 attendees, the last having been held in Toulouse, France, in 1997. The ICPIG is the only international conference comprising a full range of low-temperature plasma which, produced by various methods, has some common physical properties. For a long time such ... |
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