| Interfacial Studies of Refractory Glass-Ceramic Matrix/Advanced SiC fiber Reinforced Composites |
01 APR 93 |
65 pages |
| Authors:
J. J. Brennan; UNITED TECHNOLOGIES RESEARCH CENTER EAST HARTFORD CT
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 | The main objective of this program was to characterize the chemistry and structure of new advanced small diameter silicon based fibers and determine how these factors influence the nature of the fiber/matrix interface in refractory glass-ceramic matrix composites. It is the nature of this interface that then determines to a great degree the composite thermal, environmental, and mechanical properties. The fibers under investigation during the course of this program included ... |
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| Real-Space Formation and Dissipation Dynamics of Hexagonal Reconstruction on Au(100) in Aqueous Media as Explored by Potentiodynamic Scanning Tunneling Microscopy |
APR 93 |
48 pages |
| Authors:
Xiaoping Gao; Gregory J. Edens; Antoinette Hamelin; Michael J. Weaver; PURDUE UNIV LAFAYETTE IN DEPT OF CHEMISTRY
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| The electrode potential-induced formation and dissipation dynamics of the hexagonal ('hex') reconstruction on ordered Au(100) in perchloric and sulfuric acid electrolytes has been studied by means of in-situ scanning tunneling microscopy (STM). The real-space/real-time evolution of surface structures associated with the potential-dependent hex left and right arrows (1 x 1) phase transition was examined on timescales down to ca 1 s by acquiring STM images during appropriate potential sweeps and ... |
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| Some Electrochemical Consequences of Potential-Induced Surface Reconstruction on Au(100): Double-Layer Nonuniformity and Electrode Kinetics |
APR 93 |
31 pages |
| Authors:
Antoinette Hamelin; Livia Stoicoviciu; Gregory J. Edens; Xiaoping Gao; Michael J. Weaver; PURDUE UNIV LAFAYETTE IN DEPT OF CHEMISTRY
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| Some consequences of potential-induced surface reconstruction upon the double-layer structure and electrocatalytic properties of Au(100) in aqueous perchloric acid have been explored by means of cyclic voltammetry and differential capacitance measurements, along with in-situ scanning tunneling microscopy (STM) . Initially unreconstructed i.e. (1 x 1) Au(100) yields capacitance-potential (C-E) profiles in dilute (1 mM) perchloric acid in the vicinity of the potential of zero charge, E sub pzc, which are ... |
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| Electrode Potential-Induced Reconstruction of Au(100): Effect of Chemisorption of Nanoscale Dynamics as Probed by In-Situ Scanning Tunneling Microscopy |
APR 93 |
21 pages |
| Authors:
Xiaoping Gao; Michael J. Weaver; PURDUE UNIV LAFAYETTE IN DEPT OF CHEMISTRY
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| The effect of iodide chemisorption on the nanoscale real-space dynamics associated with the electrode potential-induced formation and removal of the hexagonal reconstruction on Au(100) in aqueous solution has been examined by means of in-situ scanning tunneling microscopy under potentiodynamic conditions. Unlike in 'non-adsorbing' media such as perchloric acid where the (1 x 1) yields (hex) phase change is slow (T 1/2 approx. 10 min), requiring adatom diffusion from terrace edges, ... |
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| FI-STM Investigation of Atomic Hydrogen Adsorption on the Si(100)2x1 Surface |
APR 93 |
27 pages |
| Authors:
Xiangdong Wang; T. Hashizume; H. Lu; H. W. Pickering; T. Sakurai; PENNSYLVANIA STATE UNIV UNIVERSITY PARK DEPT OF MATERIALS SCIENCE AND ENGINEE RING
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| A field ion-scanning tunneling microscopy study on hydrogen chemisorption on the Si(100)2x1 surface is presented. At low coverages, hydrogen atoms reside singly on top of the dimerised Si atoms, and are imaged brightly. The hydrogen chemisorption induces the buckling of dimers, indicating the strong bonding between Si and H atoms. With increasing coverage, both the 2x1 monohydride and 1x1 dihydride phases were formed. The former is imaged dark compared with ... |
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| Automated Crack Identification for Cement Paste |
APR 93 |
77 pages |
| Authors:
Kirk W. Ketcham; Francisco A. Romero; David Darwin; Shanglong Gong; Mohamed N. Abou-Zeid; KANSAS UNIV LAWRENCE CENTER FOR RESEARCH IN ENGINEERING SCIENCE
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| The development of an automated procedure for the identification of microcracks in cementitious materials is described. The degree and nature of microcracking is measured using backscattered electron images Obtained with an integrated scanning electron microscope/image analysis system. Multiple developed to identify and measure microcracks within the individual phases of cement paste. The procedure is developed to assist in the determination of the roles played by individual phases in cement paste ... |
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| Growth, Characterization and Device Development in Monocrystalline Diamond Films |
31 MAR 93 |
24 pages |
| Authors:
R. F. Davis; J. T. Glass; R. J. Nemanich; R. J. Trew; NORTH CAROLINA STATE UNIV AT RALEIGH
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| Silicon-germanium films have been grown by electron-beam deposition on naturally occurring p-type semiconducting diamond(OO1) substrates. As evidenced by low-energy electron diffraction and scanning tunneling microscopy, the SiGe layers were polycrystalline. Corresponding current-voltage (I-V) measurements conducted at room temperature demonstrated the formation of a low- barrier rectifying contact. Consistent with the observed low-barrier height, the I-V measurements recorded at 300 deg C exhibited ohmic-behavior. In addition, subsequent post-growth annealing of the ... |
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| Sea Beam 2000 Purchase and Installation |
25 MAR 93 |
2 pages |
| Authors:
G. G. Shor Jr; SCRIPPS INSTITUTION OF OCEANOGRAPHY LA JOLLA CA
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| Electric Field Induced Phenomena in STM: Tip Deformations and Au(111)- Surface Phase Transitions during Tunneling Spectroscopy Experiments |
20 MAR 93 |
34 pages |
| Authors:
Joachim H. Schott; Henry S. White; MINNESOTA UNIV MINNEAPOLIS DEPT OF CHEMICAL ENGINEERING AND MATERIALS SCIENCE
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| We report electric field induced phase transitions of Au(111) surfaces and electric field stress induced elongations of Pt-Ir and Au tips during current voltage measurements with an STM in air. Transitions between the reconstructed square root of 3 x 22 and the unreconstructed 1x1 phase of the Au(111) surface are attributed to changes in the electronic surface excess charge density induced by the electric field between tip and sample. Elongations ... |
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| Halogen Adlayers on Ag(111) |
20 MAR 93 |
24 pages |
| Authors:
Joachim H. Schott; Henry S. White; MINNESOTA UNIV MINNEAPOLIS DEPT OF CHEMICAL ENGINEERING AND MATERIALS SCIENCE
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| Atomically smooth halogen adlayers on Ag(111) (AgX, where X = I, Br, Cl and F) have been prepared by quenching of heated Ag samples in concentrated acid halide (HX) solutions. The AgX adlayers are chemically stable in air for several hours, allowing detailed characterization of the adlayer atomic structures by scanning tunneling microscopy (STM). STM images of I adlayers are consistent with a nearly perfect square root of 3 x ... |
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| Resonant Tunneling through Chemisorbed Halogen Atoms on Ag(111) |
20 MAR 93 |
17 pages |
| Authors:
Joachim H. Schott; Henry S. White; MINNESOTA UNIV MINNEAPOLIS DEPT OF CHEMICAL ENGINEERING AND MATERIALS SCIENCE
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| Tunneling spectroscopy measurements performed with a scanning tunneling microscope (STM) on Ag(111) surfaces coated with a monolayer of halogen atoms (F, Cl, Br and I) are reported. Maxima in the tunneling spectra are assigned to resonance tunneling through both the occupied p- and virtual bound states of the halogen adatoms. The observed minimum tunneling resistance at resonance is pi h/2pi/e sup 2 (approx. 12.6 k omega), in agreement with theoretical ... |
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| Direct Visualization of Defect Structures Contained Within Self- Assembled Organomercaptan Monolayers: Combined Use of Electrochemistry and Scanning Tunneling Microscopy |
19 MAR 93 |
26 pages |
| Authors:
Li Sun; Richard M. Crooks; NEW MEXICO UNIV ALBUQUERQUE DEPT OF CHEMISTRY
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| Adventitious defects within self-assembled monolayers of 1- octadecanethiol confined to Au substrate have been studied by a new method which takes advantage of the high spatial resolution of scanning tunneling microscopy (STM) and the molecular specificity of electrochemistry. The method permits direct visualization of the defect density and provides information about the chemical and structural nature of the defects. CN- was used to electrochemically etch Au from surface regions near ... |
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| Applications of Surface Science to Solid Lubricants |
15 MAR 93 |
59 pages |
| Authors:
Stephen V. Didziulis; Paul D. Fleischauer; AEROSPACE CORP EL SEGUNDO CA ENGINEERING AND TECHNOLOGY GROUP
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| Solid lubricants fill a very important niche in the world of tribology by providing low-friction surfaces under harsh operating conditions, such as high or very low temperature and high vacuum. The successful use of solid lubricants in most applications relies on controlling the chemical interactions occurring at several interfaces, and the use of surface science techniques to study and understand these chemical interactions has become increasingly more important in recent ... |
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| Site Dependence of the Apparent Shape of a Molecule in STM Images: Benzene on Pt(111) |
01 MAR 93 |
12 pages |
| Authors:
P. S. Weiss; D. M. Eigler; PENNSYLVANIA STATE UNIV UNIVERSITY PARK DEPT OF CHEMISTRY
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| We present scanning tunneling microscope images of benzene adsorbed on the Pt (111) surface. We find three distinct types of images for isolated benzene molecules, depending upon the benzene adsorption site. This site dependence is in agreement with recent theoretical calculations, and may limit the usefulness of the scanning tunneling microscope in elucidating the structures of adsorbed molecules. |
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| Antenna Gain Loss and Pattern Degradation due to Transmission Through Dielectric Radomes |
MAR 93 |
122 pages |
| Authors:
Karl A. Klopp; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| A computer model for axially symmetric dielectric radomes in the near field of a circular aperture has been developed. This model, based on a method of moments solution for bodies of revolution. is used to determine the electric field pattern of a linearly polarized circular aperture radiation through a dielectric radome. The program is written in FORTRAN and can accommodate rotationally symmetric radome shapes. Arbitrary illumination distributions for the aperture ... |
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| Effect of Water Immersion on Fiber/Matrix Adhesion in Thermoplastic Composites |
MAR 93 |
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| Authors:
Thomas Juska; NAVAL SURFACE WARFARE CENTER CARDEROCK DIV BETHESDA MD SURVIVABILITY STRUCTU RES AND MATERIALS DIRECTORATE
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 | Continuous fiber reinforced thermoplastics were tested for the effect of water immersion on fiber/matrix adhesion. The materials evaluated were E/PPS, AS4/PPS, E/J2, AS4/J2, S2/PEEK, AS4/PEEK, S2/PEKK, AS4/PEKK, and S2/VECTRA. These materials were tested in uniaxial compression, transverse flexure, and short beam shear, both dry and water-conditioned. Scanning electron microscopy was used to assess the quality of the fiber/matrix bond. The carbon reinforced materials retained adhesion after water immersion. However, the ... |
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| An Investigation of Graphite Peek Composite under Compression with a Centrally Located Circular Discontinuity |
MAR 93 |
251 pages |
| Authors:
Benjamin Wham Ii; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING
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| The purpose of this thesis was to determine (both experimentally and analytically) the initiation and progression of failure, stress-strain response, and the failure loads of Graphite/Polyetheretherketone (Gr/PEEK) laminates, incorporating a centrally located circular discontinuity, loading in axial compression at room temperature. The laminates studied were (0 deg)16,(90 deg) 16, (0 deg/90 deg)4S, (+ or - 45 deg)4S, and (0 deg/+ or - 45 deg/90 deg)2S. The specimens were loaded within ... |
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| Delay Estimation on Congested Waterways |
MAR 93 |
111 pages |
| Authors:
Melody D. Dai; ARMY ENGINEER INST FOR WATER RESOURCES FORT BELVOIR VA
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| A simulation model has been developed for estimating delays on congested waterways and a numerical method has been developed to approximate the results of the simulation model. The structural relations in the numerical method were largely based on exact analytic results from queueing theory while their unknown parameters were estimated statistically with results from the simulation model. The numerical method is valuable for screening improvement alternatives, while the simulation model ... |
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| USAF PRAM Program: SMART Shop |
23 FEB 1993 |
17 pages |
| Authors:
WARNER ROBINS AIR LOGISTICS CENTER ROBINS AFB GA
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| The Avionics Management Production Division (WR-ALC/LYP) performs depot maintenance on 125,800 end items per year from more than 20 different aircraft. The basic depot maintenance philosophy has been to test an end item until a faulty function is found and then to narrow the test to identify a failed component. No visibility was given to the prior performance or failure history. No one knew if a particular end item was ... |
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| Pseudomorphic Stabilization of Diamond on Non-Diamond Substrates: Heteroepitaxially Grown Diamond on a c-BN(111) Surface |
08 FEB 93 |
14 pages |
| Authors:
L. Wang; A. Argoitia; J. S. Ma; J. C. Angus; P. Pirouz; CASE WESTERN RESERVE UNIV CLEVELAND OH
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| A continuous diamond film with a thickness of about 10 microns was grown on (111) faces of single crystal cubic boron nitride (c-BN) by hot- Filament chemical vapor deposition (CVD). The morphology and microstructure of the diamond film were investigated by scanning and transmission electron microscopy. Cross-sectional selected area diffraction pattern (SADP) and high resolution electron microscopy (HREM) of the diamond/c-BN interface show that the diamond has a parallel orientation ... |
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| Mechanical Interaction Between Synthetic Fiber and Cement Base Matrix in FRC Composites |
FEB 93 |
26 pages |
| Authors:
Victor C. Li; Yin-Wen Chan; MICHIGAN UNIV ANN ARBOR DEPT OF CIVIL ENGINEERING
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| In cement-based materials, cement is usually employed to bind other materials together. Different interfaces are thus generated between various media in the resulted materials. It has been well recognized that the interfacial microstructure between cement binder and inclusions is of the greatest importance for the mechanical properties of the composite. Specifically, in fiber reinforced cementitious composites, the composite material properties are especially predominated by the fiber-cement interface due to its ... |
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| Material Analysis of Austempered Ductile Iron |
JAN 93 |
17 pages |
| Authors:
Sandra O. Roy; Kathryn E. Noll; ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY BENET LABS
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| A materials analysis was performed on a sample of austempered ductile iron (ADI). This material was supplied in the heat-treated condition by a commercial producer. ADI is being examined as a potential alternate material to be used in the manufacture of muzzle brakes and other candidate weapon components. The analysis included mechanical property determination, chemical composition determination, metallographic examination, and scanning electron microscopy. The mechanical properties obtained were compared to ... |
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| Development of a Laser-Induced Fluorescence System for Application to Rocket Plumes |
JAN 93 |
48 pages |
| Authors:
C. W. Brasier; R. G. Porter; ARNOLD ENGINEERING DEVELOPMENT CENTER ARNOLD AFS TN
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| The status of a continuous wave scanning ring-dye laser-induced fluorescence system is presented. This system has been developed for measurements of velocity, temperature, pressure, and specie concentration in high-speed, high-temperature gas flows. Basic principles of laser-induced fluorescence of the sodium atom are discussed. Results of laboratory studies on a sodium vapor cell are presented. Application of this system to three full- scale liquid-propellant rocket engines is discussed, and initial results ... |
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| Defect Initiation/Growth and Energy Dissipation Induced by Deformation and Fracture |
JAN 93 |
313 pages |
| Authors:
J. T. Dickinson; WASHINGTON STATE UNIV PULLMAN DEPT OF PHYSICS
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| Based on our capabilities to (1) detect and characterize particle release from surfaces on fast time scales, (2) to measure rapid electrical transients, and (3) to obtain high resolution topographical information utilizing scanning tunneling and atomic force microscopy, we present new results on the time sequence of events leading up to defect Initiation and growth which ultimately leads to fracture. We employ dynamic methods as well as post-fracture examination in ... |
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| Advantages of Environmental Scanning Electron Microscopy in Studies of Microorganisms |
93 |
9 pages |
| Authors:
Scott P. Collins; Robert K. Pope; Raymond W. Scheetz; RIchard I. Ray; Patricia A. Wagner; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS
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| Microorganisms, including bacteria, fungi, protozoa, and microalgae, are composed predominantly of water which prohibits direct observation in a traditional scanning electron microscope (SEM), Preparation for SEM requires that microorganisms be fixed, frozen or dehydrated, and coated with a conductive film before observation in a high vacuum environment. Sample preparation may mechanically disturb delicate samples, compromise morphological information, and introduce other artifacts. The environmental scanning electron microscope (ESEM) provides a technology ... |
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| Materials and Manufacturing Processing; Special Issue on Hard Carbon Films |
93 |
139 pages |
| Authors:
T. S. Sudarshan; T. S. Srivatsan; MATERIALS MODIFICATION INC FAIRFAX VA
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| Laser processing of polycrystalline diamond and amorphous carbon films is shown to be a promising technology for micropatterning of these materials in electronics and other applications. By using excimer lasers, holes and pits have been formed in 10-60 micrometers thick diamond films by physical etching with ablation rates of up to 300 nm/pulse. The channels of micrometer scale width were created in diamond-like carbon films on silicon by chemical etching ... |
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| Centroid Target Tracking System Utilizing Parallel Processing of Digital Data Patterns. |
29 DEC 1992 |
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| Authors:
Gaetano T. Amato; DEPARTMENT OF THE NAVY WASHINGTON DC
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| Outputs from data bit areas of a target sensing array, above a signal threshold level, are obtained by sequential scanning of groups of the data bit area aligned in columns and rows to form a digital pattern of binary data interrogated to determined the offset of the digital pattern from the centroid of the sensor array. Interrogation is performed by simultaneous counting of data bit pulses derived from separate segments ... |
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| Final Progress Report for Grant N00014-91-J-1785 (University of North Texas, Department of Physics, Office of Naval Research) |
29 DEC 1992 |
2 pages |
| Authors:
Floyd D. McDaniel; UNIVERSITY OF NORTH TEXAS DENTON
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| An accelerator mass spectrometry (AMS) facility has been developed at the Ion Beam Modification and Analysis Laboratory (IBMAL) at the University of North Texas (UNT) in conjunction with the 3 MV Tandem Accelerator. The computer controlled AMS instrument allows automatic mass scans of stable isotopes in solid materials using a new ultra-clean, low sample contamination ion source. The AMS instrument allows molecular interference-free mass scans to be obtained with a ... |
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| RADTRAN With Spherical-Refractive Geometry |
22 DEC 92 |
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| Authors:
William Gallery; Ronald Isaacs; ATMOSPHERIC AND ENVIRONMENTAL RESEARCH INC CAMBRIDGE MA
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| RADTRAN is a model and computer program for computing atmospheric transmittance and radiance in the microwave region. The previous version of RADTRAN assumed a plane parallel non-refracting atmosphere for computing the amounts of absorbers and scatterers (e.g. oxygen, water vapor, clouds, rain) along the optical path. However, the plane-parallel assumption breaks down for zenith angles greater than about 80 degrees, leading to large errors in the calculated radiance and transmittance. ... |
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| Pairing and Clustering of Hydrogen on Si(100)2x1: Monte Carlo Studies |
11 DEC 92 |
16 pages |
| Authors:
Yuemei L. Yang; Mark P. D'Evelyn; RICE UNIV HOUSTON TX DEPT OF CHEMISTRY
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| We consider a generalization of the doubly-occupied dimer model we proposed recently to explain the near-first-order desorption kinetics of H2 from Si(100)2xl, incorporating effective nearest-neighbor interactions between paired hydrogen atoms on adjacent dimers. We have performed Monte Carlo simulations of the generalized model, and compare the pairing and cluster-size distributions with those observed recently by scanning tunneling microscopy (STM). The agreement is reasonable but the cluster size distributions differ in ... |
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| What is Underneath? Moving Atoms and Molecules to Find Out |
01 DEC 92 |
6 pages |
| Authors:
P. S. Weiss; D. M. Eigler; PENNSYLVANIA STATE UNIV UNIVERSITY PARK DEPT OF CHEMISTRY
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| We have used the scanning tunneling microscope (STM) to move adsorbates such as benzene molecules and Xe clusters in order to determine their initial adsorption site. This has allowed us to image the initiation of the growth of a Xe surface overlayer, and to identify the sites at which this growth begins. This capability has also allowed us not only to examine the binding sites of the adsorbates, but also ... |
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| High Strain-Rate Compression Testing of a Ceramic Matrix Composite |
01 DEC 92 |
101 pages |
| Authors:
James M. Parker; ARMY STUDENT DETACHMENT FORT BENJAMIN HARRISON IN
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| Spectra of Stable Sonoluminescence |
DEC 92 |
94 pages |
| Authors:
Stephen D. Lewis; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| The continuous emission of picosecond pulses of light has been observed to originate from a bubble trapped at the pressure antinode of a resonant sound field in water and in water/glycerin mixtures. The spectra of this light in several solutions has been measured with a scanning monochrometer/ photomultiplier detector system. The spectra are broadband and show strong emission in the UV region. A comparison of this measurement to two other ... |
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| Nitride Semiconductors for Ultraviolet Detection |
DEC 92 |
55 pages |
| Authors:
Robert F. Davis; NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF MATERIALS SCIENCE AND ENGINEERING
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| Thin films of GaN and AlxGal-xN have been deposited by modified gas source MBE on alpha(6H)SiC(0001) and sapphire(0001). The values of x ranged from 0 to 1 in intervals of 0.2, as determined scanning Auger spectrometry. Simple UV photo detectors were produced and tested. The gains in the detectors was 10-20 at a bias voltage of 5 volts. The photocurrents for the solid solution detectors were much larger than for ... |
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| Sensor Modelling for the 'Cyclops' Focal Plane Detector Array Based Technology Demonstrator |
DEC 92 |
29 pages |
| Authors:
G. V. Poropat; SURVEILLANCE RESEARCH LAB SALISBURY (AUSTRALIA)
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| The Surveillance Research Laboratory of the DSTO has developed a technology demonstrator utilizing an infrared focal plane detector array to assess the feasibility of using large scale infrared detector arrays for ADF applications. The imaging sensor which has been developed requires no scanning mechanism and uses an array of mercury cadmium telluride detectors sensitive to radiation in the 8 um to 12 um spectral region to produce an image. The ... |
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| Photoelectric Analysis of the Solar Granulation in IR |
12 NOV 92 |
4 pages |
| Authors:
Serge Koutchmy; PHILLIPS LAB HANSCOM AFB MA
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| Results of both image analysis and statistical analysis of 1D scans the IR granulation observed in the opacity minimum region are briefly presented. The same technique was applied at 600 nm and results partially presented by Koutchmy and Lebecq, 1986, Astron. Astrophys. 169, 323. All observations were collected at the prime focus of the Sac Peak VTT using high signal-to-noise ratio measurements with a specially-designed pinhole PbS spectro-photometer; imaging has ... |
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| Kwalificate/Classificatie van Explosieve Stoffen en Munitie. Rapport 2. Testontwikkeling (Qualification/Classification Explosive Materials and Munition. 2. Test Development |
NOV 92 |
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| Authors:
M. W. Dirkse; R. Eerligh; E. G. De Jong; H. P. De Klerck; H. H. Kodde; PRINS MAURITS LABORATORIUM TNO RIJSWIJK (NETHERLANDS)
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| In order to supply the armed forces with adequate support in the filed of qualification of explosive substances and munition, the TNO-PML performed a research assignment in which a number of preliminary activities were executed in the field mentioned above. The activities were carried out in the period June 1991-June 1992. First an overview is made of the relevant STANAG's and AOP's. Furthermore, it was checked which of the tests ... |
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| Diagnostics of Diamond Film Deposition Plasmas |
NOV 92 |
20 pages |
| Authors:
Kenneth R. Stalder; Jay B. Jeffries; SRI INTERNATIONAL MENLO PARK CA
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| Diagnostic methods were developed and applied toward understanding the gas phase processes occurring in diamond film deposition plasmas. Diagnostics were applied in plasma arcjet environments, hot filament systems and in radio frequency plasma systems. The diagnostic methods included optical emission spectroscopy, surface Raman spectroscopy, scanning electron microscopy, laser-induced fluorescence, and surface analysis by laser ionization. The parameters that were measured included radical concentrations and temperatures, ground-state and excited-state temperatures of ... |
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| Analysis and Trial of an Active Longwave Infrared Imaging System for Minefield Detection and Identification |
NOV 92 |
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| Authors:
Jean R. Simard; DEFENCE RESEARCH ESTABLISHMENT SUFFIELD RALSTON (ALBERTA)
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| This document shows theoretical and experimental results of the capabilities of an active longwave infrared imaging system on surface laid minefields. Three anti-tank and three anti-personnel mines on soil and prairie grass backgrounds are investigated for the detection and identification capabilities of this scanning imaging system. After establishing the detection and identification capabilities of the set-up used in this experiment, an associated parameter of the imaging system is evaluated which ... |
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| Carbon and Graphite Matrices in Carbon-Carbon Composites: An Overview of their Formation, Structure, and Properties |
23 OCT 92 |
41 pages |
| Authors:
Gerald S. Rellick; AEROSPACE CORP EL SEGUNDO CA MECHANICS AND MATERIALS TECHNOLOGY CENTER
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| Carbon-carbon (C/C) composites, so called because they combine carbon-fiber reinforcement in an all-carbon matrix, can best be viewed as part of the broader category of carbon-fiber-based composites, all of which seek to utilize the light weight and exceptional strength and stiffness of carbon fibers. In C/C particularly, the structural benefits of carbon-fiber reinforcement are combined with the high-temperature capability of an all-carbon materials system, making C/C composites the material of ... |
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| Adhesion in Atomic Scale Metal Contacts |
06 OCT 92 |
16 pages |
| Authors:
L. C. Wang; H. J. Kreuzer; U. During; O. Zuger; DALHOUSIE UNIV HALIFAX (NOVA SCOTIA) DEPT OF PHYSICS
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| The adhesion interaction of an Ir tip with Ir and Al surfaces has been investigated using the scanning tunneling microscope. Qualitative differences in the adhesion characteristics have been observed. A cluster model based on effective pair-potentials has been set up to understand adhesion in atomic scale contacts. The model calculation provides a semi-quantitative explanation of the experimental data. In particular it is shown that subtle differences of the atomic interaction ... |
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| Electrical Conductivity of Ion Implanted Ladder and Semi-Ladder Polymers |
OCT 92 |
35 pages |
| Authors:
Arthur J. Epstein; OHIO STATE UNIV COLUMBUS
|
| Aromatic heterocyclic ordered rigid rod, ladder and semi-ladder polymers (including BBL, PBO, and BBB) combine exceptional high temperatures stability with excellent mechanical properties as well as environmental stability. We have carried out systemic coordinated investigation of the morphological, chemical, optical and electrical properties of ion implanted rigid rod, ladder and semi-ladder polymers, XPS data of films reveal significant reduction in the heteroatoms. An increase carbon content after implantation together with ... |
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| Corrosion Resistance of Metal Matrix Composites |
OCT 92 |
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| Authors:
R. M. Latanision; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF MATERIALS SCIENCE AND ENGINEERIN G
|
| This program examined the relationship between processing and chemistry in continuous fiber graphite/aluminum alloy metal mix composites (G/Al MMCs) with particular attention to subsequent effects on electrochemical behavior. In general, anodic polarization of (G/Al MMCs) compared well with mixed electrode model predictions. Deviations were associated with commercial fiber type and interfacial intermetallics. At high anodic overpotentials, graphite fiber oxidation and subsequent crevice formation resulted in large deviations from mixed-potential theory. ... |
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| Probing Redox-Induced Molecular Transformations by Atomic-Resolution Scanning Tunneling Microscopy: Iodide Adsorption and Electrooxidation on Au(111) in Aqueous Solution |
OCT 92 |
34 pages |
| Authors:
Xiaoping Gao; Michael J. Weaver; PURDUE UNIV LAFAYETTE IN DEPT OF CHEMISTRY
|
| In-situ atomic-resolution scanning tunneling microscopy (STM) has been utilized on ordered Au(lll) under electrode potential control in acidic aqueous solution to examine iodine adlayer structures formed by iodide electrooxidation as well as electrosorption. In the potential region, -0. 3 to 0. 4 V vs SCE, below where electrooxidation of solution iodide occurs, several distinct iodine adlayer structures were observed. At the most negative potentials, structures close to the hexagonal ((check)3 ... |
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| Probing Electrochemical Adsorbate Structure and Reactions with In-Situ Atomic-Resolution Scanning Microscopy: Some Progress and Prospects |
OCT 92 |
38 pages |
| Authors:
Xiaoping Gao; Michael J. Weaver; PURDUE UNIV LAFAYETTE IN DEPT OF CHEMISTRY
|
| Some prospects for applying scanning tunneling microscopy (STM) as an in-situ atomic-resolution probe of adlayer structure at ordered metal-solution interfaces are considered with respect to both equilibrium and reactive adsorbate systems. Illustrative results of the former type are presented for the potential-dependent adsorption of iodide at low-index gold electrodes. The virtues of acquiring composite-domain STM Images, where the electrode potential is altered during data acquisition so to form or remove ... |
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| Some Observations on Stress Graphitization in Carbon-Carbon Composites |
15 SEP 92 |
35 pages |
| Authors:
Rafael J. Zaldivar; Gerald S. Rellick; AEROSPACE CORP EL SEGUNDO CA MECHANICS AND MATERIALS TECHNOLOGY CENTER
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| The in situ stress graphitization behavior of hard carbons in unidirectionally aligned carbon-carbon (C/C) composites was studied for three carbon fibers (PAN-based T-50, pitch-based PX7, and rayon-based WCA) and two carbon precursor resins (phenol-formaldehyde (SC1008), and polyarylacetylene (PAA), a high-char-yielding, low-shrinkage resin). Graphitization was followed by measurements of density, transverse thermal expansion, d-spacing by x-ray diffraction (XRD), and by scanning electron microscopy (SEM). In conjunction with xenon-ion etching, the SEM ... |
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| Applications of Scanning Tunneling Microscopy to Electrochemistry |
15 SEP 92 |
4 pages |
| Authors:
M. J. Heben; T. L. Longin; R. Pyllki; R. M. Penner; R. Blumenthal; CALIFORNIA INST OF TECH PASADENA DIV OF CHEMISTRY AND CHEMICAL ENGINEERING
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| Our efforts through the last contract period have involved the fundamental study of the STM imaging process, the investigation of the use of partially insulated STM tips as ultramicroelectrodes, and applications of STM for the generation of lithographic features. STM investigations of conducting polymers dispersed on graphite surfaces and doped with I2 revealed that, although the conducting backbone of the polymer could be imaged under a range of tunnelling conditions, ... |
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| An Investigation of the Processing, High Temperature Deformation and Fracture Characteristics of Superplastic Ceramics |
11 SEP 92 |
2 pages |
| Authors:
Atul H. Chokshi; Joanna McKittrick; CALIFORNIA UNIV SAN DIEGO LA JOLLA DEPT OF APPLIED MECHANICS AND ENGINEERING SCIENCES
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| The considerable interest in using ceramics for structural applications is constrained in large part by the difficulty in forming ceramics in useful component shapes. Superplasticity, a term referring to the ability of some fine grained crystalline materials to deform extensively, is being used commercially to form metallic components with complex shapes. It may be possible to use this phenomenon to form structural ceramics. This proposal outlines a three year, detailed, ... |
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| Adaptive Nulling in Hybrid Reflector Antennas |
SEP 92 |
43 pages |
| Authors:
Robert A. Shore; ROME LAB HANSCOM AFB MA
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| Hybrid antennas. the combination of a radiating or receiving aperture with an array feed, have been the subject of considerable recent interest because they offer some of the versatility of phased array antennas at a much lower cost. Adaptive nulling in hybrid antennas has not received as much attention as other important aspects, such as compensation for reflector surface distortion, scanning, pattern calculation, and the design of multibeam antennas. In ... |
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| Growth, Characterization and Device Development in Monocrystalline Diamond Films |
SEP 92 |
71 pages |
| Authors:
Robert F. Davis; NORTH CAROLINA STATE UNIV AT RALEIGH
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| Ordered diamond films have been deposited on single crystal Si(100) substrates via in-situ carburization followed by bias-enhanced nucleation. Photoluminescence and Raman spectroscopy have been employed to determine the time evolution of defect formation in these CVD diamond films for stages of growth spanning nucleation to continuous film formation. Analysis of the 1332/ cm. diamond feature showed two rates of diamond growth with a transition at the thickness where nearly complete ... |
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Reports by Keyword(s)
SCANNING
