| Wafer-Fused Orientation-Patterned GaAs |
13 FEB 2008 |
9 pages |
| Authors:
Jin Li; David B. Fenner; Krongtip Termkoa; Mark G. Allen; Peter F. Moulton; Candace Lynch; David F. Bliss; William D. Goodhue; MASSACHUSETTS UNIV LOWELL
|
 | The fabrication of thick orientation-patterned GaAs (OP-GaAs) films is reported using a two-step process where an OP-GaAs template with the desired crystal domain pattern was prepared by wafer fusion bonding and then a thick film was grown over the template by low pressure hydride vapor phase epitaxy (HVPE). The OP template was fabricated using molecular beam epitaxy (MBE) followed by thermocompression wafer fusion, substrate removal, and lithographic patterning. On-axis (100) ... |
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| Theoretical Study of Defect Signatures in III-V and II-VI Semiconductors |
MAR 2006 |
62 pages |
| Authors:
Sukit Limpijumnong; SURANAREE UNIV OF TECHNOLOGY NAKHON RATCHASIMA (THAILAND)
|
| The study of defects in III-V and ZnO semiconductors was accomplished using ultrasoft pseudopotential (USPP) method. For that, a numerical approach was also implemented to calculate isotropic hyperfine-parameters for isolated defects based on a supercell method. |
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| Optically Addressed Nanostructures for High Density Data Storage |
14 OCT 2005 |
70 pages |
| Authors:
Mark A. Neifeld; Richard W. Ziolkowski; ARIZONA UNIV TUCSON DEPT OF ELECTRICALAND COMPUTER ENGINEERING
|
| A memory is any physical system with a large number of distinguishable states. Through the work undertaken in this program we have shown that an optical field can be used to distinguish among N different physical configurations of a nanostructure whose volume is comparable to a cubic wavelength, thus achieving log2(N) bits of capacity within a single resolution element. We have studied the use of near-field optical measurement together with ... |
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| Simulation and Evaluation of Routing Protocols for Mobile Ad Hoc Networks (MANETs) |
SEP 2005 |
154 pages |
| Authors:
George Kioumourtzis; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Mobile Ad hoc networks (MANETs) are of much interest to both the research community and the military because of the potential to establish a communication network in any situation that involves emergencies. Examples are search-and-rescue operations, military deployment in hostile environment, and several types of police operations. One critical open issue is how to route messages considering the characteristics of these networks. The nodes act as routers in an environment ... |
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| Comparison of Demineralized Dentin and Demineralized Freeze Dried Bone as Carriers for Enamel Matrix Proteins in a Rat Critical Size Defect |
MAY 2005 |
90 pages |
| Authors:
Kerri Font; AIR FORCE INST OF TECH WRIGHT-PATTERSONAFB OH
|
| This study evaluated the ability of Emdogain (EMD) in combination with demineralized freeze dried bone (DFDBA) or demineralized dentin matrix (DDM) to enhance bone regeneration as well as the ability of these carriers to maintain EMD at the surgical site. Critical size defects were created in rat calvaria. In Part I of the experiments, varying amounts of EMD (1 mg, 3 mg, 9 mg) with DFDBA or DDM were placed ... |
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| Effect of Sonic Thermographic Inspection on Fatigue Crack Growth in an Al Alloy |
OCT 2004 |
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| Authors:
Kelly A. Tsoi; Nik Rajic; DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION VICTORIA (AUSTRALIA) AIR VEHICLES DIV
|
 | Sonic thermography has recently emerged as an important inspection technique capable of resolving inspection problems that contemporary methods have struggled with, such as tightly closed cracks in metallic structures and kissing bonds in composite repairs. The technique uses elastic waves injected by an acoustic horn resonating at typically either 20 or 40 kHz, which often excites lateral motion at the surfaces of a defect. This motion induces frictional heating and ... |
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| Photoionisation Spectroscopy of Traps in AlGaN/GaN High Electron Mobility Transistors Grown by Molecular Beam Epitaxy |
04 SEP 2003 |
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| Authors:
P. B. Klein; J. A. Mittereder; S. C. Binari; J. A. Roussos; D. S. Katzer; D. F. Storm; NAVAL RESEARCH LAB WASHINGTON DC
|
| Photoionization spectroscopy has been carried out in bias-stressed AlGaN=GaN high electron mobility transistors (HEMTs) grown by Molecular Beam Epitaxy (MBE) to probe the nature of the deep trapping centers responsible for stress-induced current collapse in these devices. The results indicate that a GaN buffer layer trap previously associated with current collapse in devices grown by Metal Organic Chemical Vapor Deposition (MOCVD) is responsible for induced collapse in MBE-grown structures. |
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| Electron Paramagnetic Resonance Spectroscopy and Hall Effect Studies of the Effects of Low Energy Electron Irradiation on Gallium Nitride |
SEP 2003 |
186 pages |
| Authors:
Kevin D. Greene; AIR FORCE INST OF TECH WRIGHT-PATTERSONAFB OH
|
| The nature of native donors in GaN, types and interactions of radiation-induced defects, and damage creation coefficients for 1.0 MeV electron irradiation have been ascertained by the concerted application of electron paramagnetic resonance spectroscopy and Hall effect measurements to virgin and electron-irradiated GaN epilayers. Samples produced via molecular beam epitaxy and hydride vapor phase epitaxy, both silicon doped and nominally undoped, were subjected to Van de Graff generator produced monoenergtic ... |
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| Deep Level Transient Spectroscopy Study of Defects and Impurities in GaN and Related III-N Materials |
29 AUG 2003 |
5 pages |
| Authors:
David C. Look; SEMICONDUCTOR RESEARCH CENTER DAYTON OH
|
| The new system, for the first time, uses powerful Microsoft Windows Software for various options of DLTS measurements and data analyses. However, Phys Tech, which is a contractor of Accent and responsible for writing the software, did not provide us with a detailed manual of the DLTS Software until July of this year (we only received a draft of the Software manual in July). Therefore, we still have to learn ... |
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| US Department of Defense Surveillance for Neoplasms of Infancy |
MAY 2003 |
9 pages |
| Authors:
Margaret A. Ryan; NAVAL HEALTH RESEARCH CENTER SAN DIEGO CA
|
| Neoplasms of infancy include an array of diagnoses of concern to military families. These conditions affect 3-5% of all infants, and can be disfiguring, disabling, or life-threatening. Infant neoplasms are similar to birth defects in that suspected risk factors include only those exposures in the prenatal and immediate postnatal periods, including parental exposures. Since infant neoplasms are not captured by national standardized surveillance systems for birth defects, and may be ... |
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| Ex-Service F/A-18 Centre Barrel Fatigue Flaw Identification Test Plan |
MAY 2003 |
|
| Authors:
B. Dixon; L. Molent; DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION VICTORIA (AUSTRALIA) PLATFORM SCIENCES LAB
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| This report provides a generic plan for fatigue cycling and teardown of ex-service F/A-18 centre barrels for the purpose of fatigue flaw identification. It describes the accelerated fatigue test cycling program which will be applied to each centre barrel to increase the size of existing microflaws or defects so that they can be more reliably detected. It also covers the teardown, inspection and storage requirements of the project. |
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| Fracture and Residual Characterization of Tungsten Carbide Cobalt Coatings on High Strength Steel |
MAY 2003 |
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| Authors:
Donald S. Parker; OAK RIDGE NATIONAL LAB TN
|
| Tungsten carbide cobalt coatings applied via high velocity oxygen fuel thermal spray deposition are essentially anisotropic composite structures with aggregates of tungsten carbide particles bonded with both amorphous and crystalline cobalt phases. X-ray diffraction was used to characterize the residual stresses within the coatings to understand the crack initiation and propagation behavior of samples subjected to axial fatigue loads. Diffraction was also used to establish a baseline stress state of ... |
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| Fundamental Studies: Inspection Properties for Engine Titanium Alloys |
DEC 2002 |
159 pages |
| Authors:
F. J. Margetan; M. Gigliotti; L. Brashe; W. Leach; IOWA STATE UNIV AMES CENTER FOR NONDESTRUCTIVE EVALUATION
|
| Titanium alloys are widely used in critical rotating components for jet engine applications. Because of the important role they play in overall flight safety, it is important that the components be free of defects which can lead to failure. In light of this requirement, titanium components are typically inspected several times during the production process. One of the methods used is ultrasonic inspection. However, titanium is an ultrasonically noisy material ... |
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| Base Excision Repair Gene Mutations and Polymorphisms as a Potential Modifier of Breast Cancer Risk |
OCT 2002 |
11 pages |
| Authors:
Anthony T. Yeung; INSTITUTE FOR CANCER RESEARCH PHILADELPHIA PA
|
| Our hypothesis is that functional redundancy in Base Excision repair (BER) may permit polymorphism to accumulate in these parallel pathways. Deficiencies in BER may lead to elevated spontaneous mutation rates and an earlier onset of cancer. We have analysed two BER enzymes: TDG and MEDl(MBD4), both DNA N-glycosylases that remove the T residue in a T/U mismatch and the U residue in a U/U mismatch. Our analysis revealed that neither ... |
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| Pathophysiologic Impact of Doxorubicin and Radiation Therapy on the Heart of Patients Treated for Breast Cancer |
JUL 2002 |
|
| Authors:
Lawrence B. Marks; DUKE UNIV MEDICAL CENTER DURHAM NC
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| To determine the incidence, dose/time-dependence, and functional significance of regional cardiac perfusion abnormalities in patients with left-sided breast cancer treated with radiation therapy (RT) with and without doxorubicin. |
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| Electrical Conductivity in Glass-Forming Solid Electrolytes: Theory and Experiment |
01 JUL 2001 |
20 pages |
| Authors:
J. T. Bendler; C. A. Edmondson; J. J. Fontanella; M. F. Shlesinger; M. C. Wintersgill; NAVAL ACADEMY ANNAPOLIS MD
|
| A theory of the ionic conductivity in polymer electrolytes based on defect diffusion is evaluated using previously published data. Those data include the pressure and temperature variation of the electrical conductivity for poly(dimethylsiloxane-ethylene-oxide) complexed with NaCF3COO. In the defect diffusion model, ion transport is controlled by defects and ion motion occurs when the ion is encountered by a single defect. As temperature is lowered or pressure increases, the number of ... |
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| Radiation Defects in Amorphous As-Ge-S Studied by Positron Annihilation Techniques |
JUN 2001 |
|
| Authors:
O. I. Shpotyuk; J. Filipecki; R. Y. Golovchak; A. P. Kovalskiy; M. Hyla; NATIONAL UNIV LVIV (UKRAINE)
|
| The nature of coordination defects in chalcogenide vitreous semiconductors of As-Ge-S system have been analyzed before and after gamma-irradiation using the results of positron lifetime measurements. The correlations between the positron lifetime data, the structural features and the chemical compositions of glasses have been established. The identification of negatively charged point defects has been carried out. |
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| Proton Irradiation of InAs/AlSb/GaSb Resonant Interband Tunneling Diodes |
23 APR 2001 |
|
| Authors:
R. Magno; B. D. Weaver; A. S. Bracker; B. R. Bennett; NAVAL RESEARCH LAB WASHINGTON DC
|
| Room temperature current voltage measurements have been made on InAs/AlSb/GaSb resonant interband tunnel diodes (RITDs) irradiated with 2 MeV protons to determine the effect of displacement damage on the negative resistance peak current I(sub p) and the peak-to-valley current ratio P/V. Diodes with 5 and 13 ML AlSb barrier thickness were irradiated and measured several times until the total fluences reached 1 x 10(exp 15) and 2 x 10(exp 14) ... |
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| Evaluation of PPT-2 Flux-Cored Titanium Weldment |
OCT 2000 |
23 pages |
| Authors:
Michael E. Wells; NAVAL SURFACE WARFARE CENTER CARDEROCK DIV BETHESDA MD
|
| A titanium weldment fabricated in 1/2-inch thick commercially pure plate with the PPT-2 flux-cored wire was obtained from The Paton Institute for evaluation. The results of nondestructive inspection showed that the flux cored wire and welding procedures used to produce the weldment resulted in a sound weld with no indications of cracking or other internal defects. Chemical analysis showed acceptable carbon, hydrogen, iron and oxygen ... |
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| Long-Term Follow-up of Veterans Experimentally Exposed to Sarin and Other Anticholinesterase Chemical Warfare Agents |
SEP 2000 |
|
| Authors:
William Page; NATIONAL ACADEMY OF SCIENCES WASHINGTON DC
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| Between 1955 and l975, the US Army enrolled volunteers in an experimental exposure program of chemical warfare and other agents at the Edgewood Arsenal, Maryland. In 1980 the National Research Council issued a three-volume report, the last volume dealing with the current health status of test subjects which included 1,581 men exposed to anticholinesterase agents. The current study is a continued follow-up of the same subjects ... |
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| Vascular CD44 Expression and Breast Cancer Angiogenesis and Metastasis |
SEP 2000 |
|
| Authors:
Kristina G. Flores; Laura Hale; DUKE UNIV MEDICAL CENTER DURHAM NC
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| The breast cancer susceptibility gene, BRCA2, is thought to function during cellular proliferation, differentiation and DNA repair. Several lines of evidence suggest that BRCA2 may play a vital role in these processes particularly in the human thymus. First, whereas BRCA2 is expressed at relatively low levels in most tissues, it is highly expressed in normal thymus, a tissue having elevated levels of proliferation, differentiation, and DNA break and repair compared ... |
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| Advanced Nondestructive Evaluation (NDE) for Retirement for Cause/Engine Structural Integrity Program (RFC/RNSIP) |
AUG 2000 |
59 pages |
| Authors:
Mark Leethy; Robert Olding; VERIDIAN ENGINEERING DAYTON OH
|
| The Eddy Current Inspection System (ECIS) is an automated aircraft engine part inspection system that uses eddy current technology to inspect aircraft engine parts for small flaws and cracks (5 to 10 mils.) created by engine wear and fatigue. This technology was used in the Retirement for Cause/ Non-Destructive Evaluation (RFCYNDE) portion of the Engine Structural Integrity Program (ENSIP). The ECIS is comprised of three primary modules, the Signal Generation/Detection ... |
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| Characterization of Breast Cancer Cell Death Induced by Interferons and Retinoids |
JUN 2000 |
|
| Authors:
Dhan Kalvakolanu; Edward Hofmann; MARYLAND UNIV BALTIMORE
|
| Apoptosis or programmed cell death (PCD) is a biological process used by metazoans to eliminate cells that are superfluous or potentially dangerous. PCD is vital to proper animal development as well as tissue homeostasis in adults. It has also been implicated as a mechanism for eliminating pathogen infected cells. Defective regulation of apoptosis has been implicated in various pathological conditions including cancer, autoimmune diseases 1, 2 stroke damage and neurodegenerative ... |
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| Using the Foerster Rivet Check System to Detect Cracks Under Installed Fasteners |
MAY 2000 |
|
| Authors:
R. W. Nolan; DEFENCE AND CIVIL INST OF ENVIRONMENTALMEDICINE DOWNSVIEW (ONTARIO)
|
| The Foerster Rivet Check system is an instrument designed to detect cracks under installed fasteners in relatively thin layers of an aircraft skin. Its operation is based on a rotating self-nulling eddy current probe. It was found that the system is able to detect relatively small cracks under non- ferrous fasteners at depths up to 0.12" in layers of aircraft skin. The amplitude of its' ... |
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| Observation of Deep Traps Responsible for Current Collapse in GaN Metal-Semiconductor Field-Effect Transistors |
20 DEC 1999 |
|
| Authors:
P. B. Klein; Jr. Freitas J. A.; S. C. Binari; A. E. Wickenden; NAVAL RESEARCH LAB WASHINGTON DC
|
| Deep traps responsible for current collapse phenomena in GaN metal semiconductor field-effect transistors have been detected using a spectroscopic technique that employs the optical reversibility of current collapse to determine the photoionization spectra of the traps involved. In the n-channel device investigated, the two electron traps observed were found to be very deep and strongly coupled to the lattice. Photoionization thresholds for these traps were determined at 1.8 and at ... |
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| ASSERT Grant: Evolution of Stress and Damage in Coatings for Thermal Protection Systems |
MAY 1999 |
41 pages |
| Authors:
David R. Clarke; CALIFORNIA UNIV SANTA BARBARA DEPT OF MATERIALS
|
| The goals of this AASERT were to establish quantitative relationshipsbetween the stress in alumina scales (formed beneath thermal barrier coatings during high-temperature exposure), the oxidation conditions and accompanying microstructural changes. The technique utilized was that of photostimulated Cr(3+) luminescence piezospectroscopy developed under the parent grant. Piezospectroscopy measurements of the residual stress evolution during prolongedoxidation exposure have revealed that, contrary to expectation in the community,the stress initially changes rather rapidly and ... |
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| Microlithographic Mask Development (MMD). CDRL H007: Option 3 Contract Summary Report CDRL H004: Contractor Progress, Status, Management Report |
22 JAN 1999 |
|
| Authors:
LOCKHEED MARTIN FEDERAL SYSTEMS MANASSAS VA
|
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| Amorphous Silicon Research |
JUN 1998 |
56 pages |
| Authors:
R. Arya; D. Carlson; L. Chen; G. Ganguly; M. He; G. Lin; R. Middya; S. Skibo; G. Wood; NATIONAL RENEWABLE ENERGY LAB GOLDEN CO
|
| This report describes the Solarex R&D effort as part of the Thin Film Partnership with NREL under Subcontract No. ZAN-4-13318-01. The major goal of this program has been to develop the device and processing technology necessary to commercialize large-area amorphous silicon tandem PV modules. There were three major areas of investigation in this program: (1) research on mid-gap amorphous silicon alloys; (2) research on low-bandgap amorphous silicon alloys; and (3) ... |
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| Defense Logistics Agency Product Quality Deficiency Program |
05 FEB 1998 |
49 pages |
| Authors:
INSPECTOR GENERAL DEPT OF DEFENSE ARLINGTON VA
|
| We initiated the audit in response to a request from the Director, Defense Logistics Agency. He was interested in improving the product quality deficiency report system, which is used by DoD Components to identify and purge nonconforming material from inventory and to provide information to contracting officers, contractors, and customers. Nonconforming material is a defective supply item that cannot be used for its designed purpose because of material, manufacturing, or ... |
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| Vortex Dynamics in Lightly-Doped Films of High Temperature Superconductors |
JUN 1997 |
5 pages |
| Authors:
Lemberger; OHIO STATE UNIV RESEARCH FOUNDATION COLUMBUS
|
| Evidence is presented supporting the view that the inductance of vortices in films is due to columnar defects. The temperature dependence of the pinning strength is dominated by thermal supercurrent or "phase" fluctuations rather than by the mean-field temperature dependence of basic superconducting quantities like the Helmholtz free energy and the magnetic penetration depth. |
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| Electronic Applications of Magnetic Resonance Force Microscopy |
97 |
134 pages |
| Authors:
IBM RESEARCH LAB SAN JOSE CA
|
| This is the final report for Office of Naval Research Contract N0001495-C- 0124. Work under this recently completed contract has focused on improving the basic technology of magnetic resonance force microscopy (MRFM) and working towards the dual goals of dopant detection ill silicon and single electron spin detection. In addition, a number of important advances were achieved, including ultrasensitive force detection, magnetic resonance characterization of dangling bond defects in SiO2, ... |
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| Thermal Wave Imaging of Hidden Corrosion in Aircraft Components |
22 NOV 96 |
22 pages |
| Authors:
R. L. Thomas; L. D. Favro; P. K. Kuo; WAYNE STATE UNIV DETROIT MI INST FOR MANUFACTURING RESEARCH
|
| A program of basic research was carried out, whose objective was to make the promising qualitative thermal wave imaging NDI technique a truly quantitative tool which can have a major impact on the rapid, wide-area inspection of Air Force aircraft for hidden corrosion in aircraft components. During the program a theoretical framework was developed, based on three- dimensional scattering of thermal waves from planar subsurface defects, and the model was ... |
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| Nondestructive Detection and Characterization of Corrosion in Aircraft |
NOV 96 |
9 pages |
| Authors:
James H. Rose; John C. Moulder; Joseph N. Gray; IOWA STATE UNIV AMES CENTER FOR NONDESTRUCTIVE EVALUATION
|
| We have developed a fully characterized pulsed eddy current (PEC) instrument to detect and characterize second-layer corrosion in aircraft skin. In the first year, we developed the theory needed to accurately model the response of the PEC instrument measured on a variety of calibration specimens. In the second year, we made experimental measurements on a number of realistic samples including a corrosion test panel provided by Boeing corporation. In addition, ... |
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| Scanning Tunneling Microscopy Studies of the Morphology and Kinetic Pathways for Corrosion Reactions of Stressed Materials |
NOV 96 |
16 pages |
| Authors:
Steven J. Sibener; CHICAGO UNIV IL DEPT OF CHEMISTRY
|
| This research program improved our understanding of how surface chemical reactions, surface stress, and atomic level microstructure influence materials oxidation/corrosion processes. Central to this effort was the construction of a new scanning probe microscopy facility which now houses a UHV- STM and a combined STM/AFM for operation in both air and electrochemical environments. It was demonstrated that applied stress fields can influence the electrochemical pitting corrosion chemistry of pure aluminum ... |
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| Defects and Impurities in 4H- and 6H-SiC Homoepitaxial Layers: Identification, Origin, Effect on Properties of Ohmic Contacts and Insulating Layers and Reduction |
SEP 96 |
36 pages |
| Authors:
R. F. Davis; M. O. Aboelfotoh; B. J. Baliga; R. J. Nemanich; NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| A SiC CVD system has been assembled to grow and dope 4H- and 6H-SiC thin films. The design incorporates a separate load lock from which the growth chamber and a RHEED chamber are attached. Power supply components remain to be received. Comparisons between the wetting characteristics of the on- and off- axis as well as the oxidized and unoxidized 6H-SiC(0001)subSi surfaces in various acids and bases were made to that ... |
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| Development of a Laser-Based System for the Detection of Flaws in Solid Rocket Motors |
MAY 1996 |
70 pages |
| Authors:
J. L. Doyle; R. McCullough; G. K. Torrington; QUEST INTEGRATED INC KENT WA
|
| Solid rocket motors are often stored for long periods of time, frequently under extreme environmental conditions. Thermal cycling and aging can induce internal flaws, such as cracking and slumping, that can lead to catastrophic failures, often resulting in significant loss of property and even loss of life. This report summarizes the results of the Phase I study to develop a lightweight, portable, and rugged system that is capable of conducting ... |
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| Automated Silicon Nitride Bearing Ball Inspection Station |
FEB 96 |
13 pages |
| Authors:
David E. Thomas; QUATRO CORP ALBUQUERQUE NM
|
| Contract Number DAAH0l-94-C-R285, Quatro Corporation has developed a fully-functional, automated silicon nitride Bearing Ball Inspection Station which utilizes Resonant Inspection (Resonant Inspection) to determine if the balls are flawed or acceptable. The Bearing Ball Inspection Station was demonstrated at the Norton Advanced Ceramics facility in East Granby, Connecticut in October of 1995. The station was successful in finding flaws in several sizes of silicon nitride bearing balls, although more work ... |
|
| Fort Irwin, CA, Family Housing Comparison Test: Operation and Maintenance Costs of Manufactured vs. Conventionally Built Units |
SEP 95 |
66 pages |
| Authors:
Robert D. Neathammer; CONSTRUCTION ENGINEERING RESEARCH LAB (ARMY) CHAMPAIGN IL
|
| To determine if manufactured factory-built family housing is more cost-effective in providing housing than conventional construction, Congress directed that a test of construction methods be conducted. In 1982, Congress authorized the construction of 200 units of manufactured factory-built housing at Fort Irwin, CA, and concurrently, 144 units of conventionally built units. Congress directed the Department of Defense (DOD) to conduct a fair and reliable study comparing the operation and maintenance ... |
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| Roof Blisters: Cause and Cure |
JUL 95 |
13 pages |
| Authors:
Charles Korhonen; Brian Charest; COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH
|
| Blisters are a major problem of built-up roof membranes. They are caused by voids built into the roof during construction. They develop into the characteristic dome-shaped humps by a breathing action driven by thermal cycling. A small pressure relief vent was patented by CRREL as a cost-effective way to repair blisters. Though these vents cannot prevent blisters from forming, they can lengthen a roof's service life by repairing the blisters ... |
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| Atomistic Calculations of Defects in ZnGeP2 |
09 JUN 95 |
24 pages |
| Authors:
Ravi Pandey; MICHIGAN TECHNOLOGICAL UNIV HOUGHTON DEPT OF PHYSICS
|
| Atomistic calculations are performed to study defect energetics in ZnGeP2 were two- and three-body interatomic potentials are used to simulate the perfect lattice. Formation energies for native ionic defects and binding energies for some of the electronic defect-complexes are calculated. The dominance of antisite defect-pairs is predicted in the lattice. However, the defects controlling the spectroscopic properties would seem to be associated with vacancies. For the EPR-active acceptor center, the ... |
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| LNTlSb as a Long-Wave Infrared (LWIR) Material: Defects and Transport Properties |
FEB 95 |
67 pages |
| Authors:
S. Krishnamurthy; M. van Schilfgaarde; M. A. Berding; A. Sher; SRI INTERNATIONAL MENLO PARK CA
|
| We have evaluated three III-V semiconductor alloys as possible candidates for future long-wave infrared (LWIR) detector materials. The cohesive energies, elastic constants, band structures, electron mobilities, and phase diagrams are calculated and are compared to those of Hg sub 1-xCd sub xTe (MCT) alloys. All three of these III-V alloys have their band gap change from negative to positive values as the alloy composition x decreases from 1 to 0. ... |
|
| Third Monthly Progress Report on Contract N00014-94-C-0210. Phase 1 |
21 DEC 94 |
2 pages |
| Authors:
Steven Green; NEOCERA INC COLLEGE PARK MD
|
| The goal of this SBIR Phase I project is to establish the feasibility of designing a High Temperature Superconductor (HTS) Superconducting QUantum Interference Device (SQUID) microscope in order to detect defects, and verify customizations and repairs in MCM substrates. The overall goal of this SBIR program is to market an HTS SQUID microscope dedicated to the inspection of MCM substrates in a manufacturing environment. Neocera and its subcontractor, the Center ... |
|
| CT-Assisted Solid Freedom Manufacturing |
15 NOV 94 |
6 pages |
| Authors:
James H. Stanley; ADVANCED RESEARCH AND APPLICATIONS CORP SUNNYVALE CA
|
| In response to the Advanced Research Projects Agency (ARPA) Broad Area Announcement (BAA) 93-24, "Solid Freeform Manufacturing," ARACOR successfully proposed the development and demonstration of CT-assisted solid- freeform manufacturing practices. The project will provide critical reverse engineering and part characterization functions common to all ARPA-sponsored SFM activities. The goal is to facilitate the timely transition of CT-assisted reverse-engineering, dimensional verification and defect detection practices to the SFM manufacturing community. (AN) ... |
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| Study of the Vortex-Glass Phase Transition in High Tc Superconductors |
SEP 94 |
124 pages |
| Authors:
Thomas Lemberger; OHIO STATE UNIV COLUMBUS DEPT OF PHYSICS
|
| This project extended understanding of vortex behavior in oxide superconductors in two important directions. First, we made discoveries regarding the morphology of the defects that pin vortices in films very effectively and regarding the nature of the phase transition that separates the low magnetic field, low temperature vortex glass from the high field, high temperature vortex liquid. In both cases, our results challenge the status quo. Second, we demonstrated fabrication ... |
|
| Characterization of the Ferroelectric Imprinting Mechanism |
16 MAY 94 |
|
| Authors:
Joseph T. Evans Jr; RADIANT TECHNOLOGIES ALBUQUERQUE NM
|
|
| Role of Water in Proton-Hydroxide Conductance Across Model and Biological Membranes |
25 OCT 93 |
|
| Authors:
David W. Deamer; CALIFORNIA UNIV DAVIS
|
| Our research effort focused on proton flux mechanisms, building on our original observation that protons diffuse across lipid bilayer membranes by a process quite different from that of other cations. As a working hypothesis, we proposed that proton equivalents move along hydrogen bonded chains of water molecules which occur in transient defects in the bilayer. We have extended this concept to the action of certain membrane perturbants on the bilayer. ... |
|
| Effect of Fiber-Matrix Interphase on Transverse Tensile Strength and Fracture Resistance of Organic Composite Materials |
04 SEP 93 |
279 pages |
| Authors:
Hsi C. Tsai; Annette Arocho; NAVAL AIR WARFARE CENTER AIRCRAFT DIV WARMINSTER PA
|
| Unidirectional fiber reinforced composites have a very low transverse tensile strength. This strength is much lower than the strength of the pure matrix and limits the performance of the composite system. The objective of this IR program is to develop analytical methods which predict the transverse tensile failures of organic composites and to examine how various parameters influence the transverse tensile strength and failure modes. Analytical methods developed in this ... |
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| Impact of Materials Defects on Engine Structures Integrity (L'Impact des Defauts des Materiaux sur l'Integrite des Structures des Moteurs) |
APR 93 |
|
| Authors:
ADVISORY GROUP FOR AEROSPACE RESEARCH AND DEVELOPMENT NEUILLY-SUR-SEINE (FRAN CE)
|
| Even though we have made significant progress in increasing reliability of critical components of aeroengines, we have far too many failures in both military and commercial engines. As well, maintenance costs, warranty costs (spares) and liability costs are too high. In addition, designers of aeroengines will undoubtedly always seek to increase performance and efficiency as well to increase the life of components. At the same time, it is desirable to ... |
|
| Detection and Removal of Defects in Apparel Production |
MAR 93 |
34 pages |
| Authors:
Wayne Tincher; Wayne Daley; Wiley Holcombe; GEORGIA INST OF TECH ATLANTA
|
| Defects in fabric have been and continue to be a major source of seconds in finished garments. These, defects persist despite several visual inspections and intensive efforts to remove defective parts during, sewing operations. The increase use of automation in assembly steps will intensify the problem of detection and removal of fabric defects in cut-parts. A workstation utilizing machine vision has been designed and constructed to detect and remove defective ... |
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| Three-Dimensional Elastic Stress Analysis in Materials With Many Inhomogeneities |
FEB 93 |
|
| Authors:
Mark Kachanov; TUFTS UNIV MEDFORD MA DEPT OF MECHANICAL ENGINEERING
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| The research effort was concentrated on micromechanics of brittle materials with multiple interacting defects, and on the impact of the defects on the overall (effective) properties. The work addressed the following problems: (1) Three-dimensional mechanics of crack interactions. (2) Three-dimensional mechanics of crack-microcrack interactions. (3) Relationship between fracturing of a brittle microcracking material and reduction of its effective stiffness. (4) Effective elastic properties of cracked solids and continuum characterization of ... |
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Reports by Keyword(s)
DEFECTS(MATERIALS)
