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Deep Levels in p- and n-type InGaAsN for High Efficiency Multi-Junction III-V Solar Cells (open access)

Deep Levels in p- and n-type InGaAsN for High Efficiency Multi-Junction III-V Solar Cells

Red Teaming is an advanced form of assessment that can be used to identify weaknesses in a variety of cyber systems. it is especially beneficial when the target system is still in development when designers can readily affect improvements. This paper discusses the red team analysis process and the author's experiences applying this process to five selected Information Technology Office (ITO) projects. Some detail of the overall methodology, summary results from the five projects, and lessons learned are contained within this paper.
Date: November 11, 1999
Creator: Allerman, Andrew A.; Jones, Eric D.; Kaplar, Robert J.; Kurtz, Steven R.; Kwon, Daewon & Ringel, Steven A.
System: The UNT Digital Library
Jahn-Teller splitting and Zeeman effect of acceptors in diamond. (open access)

Jahn-Teller splitting and Zeeman effect of acceptors in diamond.

Employing the high resolution of a 5+4 tandem Fabry-Perot interferometer, we discovered that {Delta}{prime}, the Raman active electronic transition between the spin-orbit split 1s(p{sub 3/2}): {Lambda}{sub 8} and 1s(P{sub 1/2}) {Lambda}{sub 7} acceptor ground states, is a doublet for a boron impurity in diamond with a clearly resolved spacing of 0.81 {+-} 0.15 cm{sup {minus}1}. The direct observation of a Stokes/anti-Stokes pair with 0.80 {+-} 0.04 cm{sup {minus}1} shift provides a striking confirmation that the lower 1s(p{sub 3/2}): {Lambda}{sub 8} ground state has experienced a splitting due to a static Jahn-Teller distortion. The Zeeman effect of {Delta}{prime} has been investigated with a magnetic field along several crystallographic directions. Theory of the Zeeman effect, formulated in terms of the symmetry of the substitutional acceptor and the Luttinger parameters of the valence band, allows quantitative predictions of the relative intensities of the Zeeman components in full agreement with experiments. The observation of transitions within the {Lambda}{sub 8} Zeeman multiplet, i.e., the Raman-electron-paramagnetic-resonances, is yet another novel feature to emerge from the present study. The investigation has also yielded g-factors characterizing the Zeeman multiplets.
Date: September 11, 1999
Creator: Anthony, T. R.; Grimsditch, M.; Kim, H.; Ramdas, A. K. & Rodriguez, S.
System: The UNT Digital Library
Benchmarking D and D procurement best practices at four commercial nuclear power plants. (open access)

Benchmarking D and D procurement best practices at four commercial nuclear power plants.

The Department of Energy (DOE) has as two of its strategic objectives to safely accomplish the world's largest environmental clean-up of contaminated sites and the adoption of the best management practices of the private sector to achieve business-like results efficiently and effectively. An integral part of the strategic response to the challenges facing the Department has been the use of benchmarking and best practice management to facilitate identifying and implementing leading-edge thinking, practices, approaches, and solutions.
Date: May 11, 1999
Creator: Arflin, J.; Baker, G.; Bidwell, B.; Bugielski, D.; Cavanagh, J. & Sandlin, N.
System: The UNT Digital Library
Proton Irradiation Effects in Oxide-Confined Vertical Cavity Surface Emitting Laser (VCSEL) Diodes (open access)

Proton Irradiation Effects in Oxide-Confined Vertical Cavity Surface Emitting Laser (VCSEL) Diodes

Recent space experience has shown that the use of commercial optocouplers can be problematic in spacecraft, such as TOPEX/Poseidon, that must operate in significant radiation environments. Radiation--induced failures of these devices have been observed in space and have been further documented at similar radiation doses in the laboratory. The ubiquitous use of optocouplers in spacecraft systems for a variety of applications, such as electrical isolation, switching and power transfer, is indicative of the need for optocouplers that can withstand the space radiation environment. In addition, the distributed nature of their use implies that it is not particularly desirable to shield optocouplers for use in radiation environments. Thus, it will be important for the space community to have access to radiation hardened/tolerant optocouplers. For many microelectronic and photonic devices, it is difficult to achieve radiation hardness without sacrificing performance. However, in the case of optocouplers, one should be able to achieve both superior radiation hardness and performance for such characteristics as switching speed, current transfer ratio (CTR), minimum power usage and array power transfer, if standard light emitting diodes (LEDs), such as those in the commercial optocouplers mentioned above, are avoided, and VCSELs are employed as the emitter portion of the …
Date: March 11, 1999
Creator: Armendariz, M. G.; Barnes, C. E.; Choquette, K. D.; Guertin, S.; Hash, G. L.; Schwank, J. R. et al.
System: The UNT Digital Library
First Lasing of a High-Gain Harmonic Generation Free-Electron Laser Experiment. (open access)

First Lasing of a High-Gain Harmonic Generation Free-Electron Laser Experiment.

We report on the first lasing of a high-gain harmonic generation (HGHG) free-electron laser (FEL). The experiment was conducted at the Accelerator Test Facility (ATF) at Brookhaven National Laboratory (BNL). This is a BNL experiment in collaboration with the Advanced Photon Source (APS) at Argonne National Laboratory. A preliminary measurement gives a high-gain harmonic generation (HGHG) pulse energy that is 2 x 10{sup 7} times larger than the spontaneous radiation, In a purely self-amplified spontaneous emission (SASE) mode of operation, the signal was measured as 10 times larger than the spontaneous radiation in the same distance ({approximately}2 m) through the same wiggler. This means the HGHG signal is 2 x 10{sup 6} times larger than the SASE signal. To obtain the same saturated output power by the SASE process, the radiator would have to be 3 times longer (6 m).
Date: September 11, 1999
Creator: Babzien, M.; Ben-Zvi, Ilan; Biedron, S. G.; DiMauro, L. F.; Douryan, A.; Galayda, J. N. et al.
System: The UNT Digital Library
Transport, Growth Mechanisms, and Material Quality in GaN Epitaxial Lateral Overgrowth (open access)

Transport, Growth Mechanisms, and Material Quality in GaN Epitaxial Lateral Overgrowth

Growth kinetics, mechanisms, and material quality in GaN epitaxial lateral over-growth (ELO) were examined using a single mask of systematically varied patterns. A 2-D gas phase reaction/diffusion model describes how transport of the Ga precursor to the growth surface enhances the lateral rate in the early stages of growth. In agreement with SEM studies of truncated growth runs, the model also predicts the dramatic decrease in the lateral rate that occurs as GaN over-growth reduces the exposed area of the mask. At the point of convergence, a step-flow coalescence mechanism is observed to fill in the area between lateral growth-fronts. This alternative growth mode in which a secondary growth of GaN is nucleated along a single convergence line, may be responsible for producing smooth films observed to have uniform cathodoluminescence (CL) when using 1{micro}m nucleation zones. Although emission is comprised of both UV ({approximately}365nm) and yellow ({approximately}550nm) components, the spectra suggest these films have reduced concentrations of threading dislocations normally associated with non-radiative recombination centers and defects known to accompany growth-front convergence lines.
Date: January 11, 1999
Creator: Baca, Albert G.; Bartram, M. E.; Coltrin, M. E.; Crawford, M. H.; Han, J.; Missert, N. et al.
System: The UNT Digital Library
Effect of interior surface finish on the break-up of commercial shaped charge liners (open access)

Effect of interior surface finish on the break-up of commercial shaped charge liners

A series of experiments aimed at understanding the influence of the liner interior surface finish on the break-up of shaped charge jets has been completed. The experiments used a standard 81-mm shaped charge design, loaded with LX-14 high explosive; incorporating high-precision copper shaped charged liners. The results indicate that a significant reduction of jet break-up time occurs between a surface finish of 99.30 microinches and 375.65 microinches. Surface finishes of 4.78, 44.54 and 99.30 microinches produced significantly better ductility and associated break-up times than the 375.65-microinch finish. The baseline production process high-precision liners were measured to have an average surface finish of 44.54 microinches. The results show that for the shaped charge warhead geometry and explosive combination investigated, some care must be taken in respect to surface finish, but that very fine surface finishes do not significantly improve the jet ductility and associated break-up times.
Date: August 11, 1999
Creator: Baker, E L & Schwartz, A J
System: The UNT Digital Library
Steam generator mock-up for assessment of inservice inspection technology. (open access)

Steam generator mock-up for assessment of inservice inspection technology.

A steam generator mock-up has been assembled for round-robin studies of the effectiveness of currently practiced inservice inspection (ISI) technology for detection of current-day flaws. The mock-up will also be used to evaluate emerging inspection technologies. The 3.66-m (12-ft.)-tall mock-up contains 400 tube openings, each consisting of 9 test sections that can be used to simulate current-day field-induced flaws and artifacts. Included in the mock-up are simulations of tube support plate (TSP) intersections and the tube sheet (TS). Cracks are present at the TSP, TS, and in the free span sections of the mock-up. For initial evaluation of the round-robin results, various eddy current methods, as well as multivariate models for data analysis techniques, are being used to estimate the depth and length of defects in the mock-up. To ensure that the round-robin is carried out with procedures as close as possible to those implemented in the field, input was obtained from industry experts on the protocol and procedures to be used for the exercise. One initial assembly of the mock-up with a limited number of flaws and artifact has been completed and tested. A second completed configuration with additional flaw and artifacts simulations will be used for the round-robin.
Date: September 11, 1999
Creator: Bakhtiari, S.; Kupperman, D. S. & Muscara, J.
System: The UNT Digital Library
The intermediate silicon layers space Fframe (open access)

The intermediate silicon layers space Fframe

The Intermediate Silicon Layers (ISL) detector is being built as part of the Collider Detector at Fermilab (CDF) upgrades for the run II operation of Tevatron. The ISL Space Frame (SF) is a structure that defines the location of the ISL detectors, supports the micro-vertex silicon trackers (SVXII, L00) as well as the beryllium beam pipe. The SF design, project and construction is challenging due to the precision and mechanical stability requirements that must be achieved using a minimum amount of material. The SF is a high precision light structure made in carbon fiber designed and built at the INFN Pisa and shipped at Fermilab in summer 1999. In this contribution we describe in detail the SF construction phase and the accuracy obtained.
Date: November 11, 1999
Creator: Basti, A.; Bedeschi, F.; Demina, R.; Gaggelli, A. & Goldstein, J.
System: The UNT Digital Library
Ultrasonic characterization of synthetic soils for application to near surface geophysics (open access)

Ultrasonic characterization of synthetic soils for application to near surface geophysics

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Date: November 11, 1999
Creator: Berge, P; Bonner, B P; Boro, C; Hardy, E; Ruddle, C & Trombino, C
System: The UNT Digital Library
Solvent Extraction of Tc and Cs from Alkaline Nitrate Wastes (open access)

Solvent Extraction of Tc and Cs from Alkaline Nitrate Wastes

This paper summarizes progress at three collaborating US national laboratories on the extraction of the fission products {sup 99}Tc and {sup 137}Cs from alkaline high-level wastes (HLW). Efficient, economical processes for Tc and Cs extraction (SRTALK and alkaline-side CSEX, respectively) have been developed, and testing has progressed through batch tests on actual wastes and continuous countercurrent centrifugal-contactor tests on simulants.
Date: July 11, 1999
Creator: Bonnesen, P. V.; Conner, C.; Delmau, L. H.; Haverlock, T. J.; Leonard, R. A.; Lumetta, G. J. et al.
System: The UNT Digital Library
Magnetic properties and crystal structure of RENiA1 and UniA1 hydrides. (open access)

Magnetic properties and crystal structure of RENiA1 and UniA1 hydrides.

RENiAl (RE = rare-earth metal) and UNiAl compounds crystallizing in the hexagonal ZrNiAl-type structure (space group P{bar 6}2m) can absorb up to 2 and 3 hydrogen (deuterium) atoms per formula unit, respectively. Hydrogenation leads to a notable lattice expansion and modification of magnetic properties. However, the impact of hydrogenation on magnetism is the opposite for 4f- and 5f-materials: TN(T{sub c})is lowered in the case of rare-earth hydrides, while for UNiAlH(D){sub x} it increases by an order of magnitude. Here we present results of magnetic and structure studies performed of these compounds, focusing on the correlation between magnetic and structural variations and discussing possible reasons of the striking difference in effect of hydrogenation on rare-earth and actinide intermetallics.
Date: August 11, 1999
Creator: Bordallo, H. N.; Drulis, H.; Havela, L.; Iwasieczko, W.; Kolomiets, A. V.; Nakotte, H. et al.
System: The UNT Digital Library
A Coupled Modeling System to Simulate Water Resources in the Rio Grande Basin (open access)

A Coupled Modeling System to Simulate Water Resources in the Rio Grande Basin

Limited availability of fresh water in arid and semi-arid regions of the world requires prudent management strategies from accurate, science-based assessments. These assessments demand a thorough understanding of the hydrologic cycle over long time periods within the individual water-sheds that comprise large river basins. Measurement and simulation of the hydrologic cycle is a tremendous challenge, involving a coupling between global to regional-scale atmospheric precipitation processes with regional to local-scale land surface and subsurface water transport. Los Alamos National Laboratory is developing a detailed modeling system of the hydrologic cycle and applying this tool at high resolution to assess the water balance within the upper Rio Grande river basin. The Rio Grande is a prime example of a river system in a semiarid environment, with a high demand from agricultural, industrial, recreational, and municipal interests for its water supply. Within this river basin, groundwater supplies often augment surface water. With increasing growth projected throughout the river basin, however, these multiple water users have the potential to significantly deplete groundwater resources, thereby increasing the dependence on surface water resources.
Date: January 11, 1999
Creator: Bossert, J. E.; Breshears, D. D.; Campbell, K.; Costigan, K. R.; Greene, R. K.; Keating, E. H. et al.
System: The UNT Digital Library
Characterization of Pu colloidal and aqueous species in Yucca Mountain groundwater surrogate (open access)

Characterization of Pu colloidal and aqueous species in Yucca Mountain groundwater surrogate

The speciation and formation of Pu intrinsic colloids from an initial solution of Pu(V) were studied at pH 1, pH 3, pH 6, pIH 8, and pH 11. The medium was a surrogate Yucca Mountain groundwater from well J-l 3 under air atmosphere. The solutions were monitored for several months. Samples were analyzed using liquid scintillation counting, ultra filtration, solvent extraction: photon correlation spectroscopy, and laser-induced photo-acoustic breakdown and emission spectroscopy. Redox potentials were measured periodically. The time dependencies of soluble and colloidal Pu concentrations are reported. The size and concentration of Pu colloid particles were estimated.
Date: August 11, 1999
Creator: Bourcier, W. L.; Brachmann, A.; Jardine, L. J.; Palmer, C. E.; Romanovski, V. V. & Shaw, H. F.
System: The UNT Digital Library
Lessons Learned from the Puerto Rico Battery Energy Storage System (open access)

Lessons Learned from the Puerto Rico Battery Energy Storage System

The Puerto Rico Electric Power Authority (PREPA) installed a battery energy storage system in 1994 at a substation near San Juan, Puerto Rico. It was patterned after two other large energy storage systems operated by electric utilities in California and Germany. The Puerto Rico facility is presently the largest operating battery storage system in the world and has successfully provided frequency control, voltage regulation, and spinning reseme to the Caribbean island. The system further proved its usefulness to the PREPA network in the fall of 1998 in the aftermath of Hurricane Georges. However, the facility has suffered accelerated cell failures in the past year and PREPA is committed to restoring the plant to full capacity. This represents the first repowering of a large utility battery facility. PREPA and its vendors and contractors learned many valuable lessons during all phases of project development and operation, which are summarized in this paper.
Date: August 11, 1999
Creator: Boyes, John D.; De Anda, Mindi Farber & Torres, Wenceslao
System: The UNT Digital Library
Laser-induced breakdown system for colloid characterization in dilute aqueous suspensions (open access)

Laser-induced breakdown system for colloid characterization in dilute aqueous suspensions

Detection and sizing of colloids by acoustic detection of laser-induced breakdown and elemental analysis of colloids by laser-induced breakdown spectroscopy are investigated in dilute aqueous suspensions. Development and testing of the methods are performed with standard polystyrene suspensions and prepared suspensions of defined composition and particle size. Application of the methods to analysis of field and laboratory samples is discussed. Am atomic emission lines are observed by laser-induced breakdown spectroscopy of an Am hydroxycarbonate suspension.
Date: August 11, 1999
Creator: Brachmann, A.; Mihardja, S.; Palmer, C. E. A. & Wruck, D. A.
System: The UNT Digital Library
Multiple Input Microcantilever Sensor with Capacitive Readout (open access)

Multiple Input Microcantilever Sensor with Capacitive Readout

A surface-micromachined MEMS process has been used to demonstrate multiple-input chemical sensing using selectively coated cantilever arrays. Combined hydrogen and mercury-vapor detection was achieved with a palm-sized, self-powered module with spread-spectrum telemetry reporting.
Date: March 11, 1999
Creator: Britton, C. L., Jr.; Brown, G. M.; Bryan, W. L.; Clonts, L. G.; DePriest, J. C.; Emergy, M. S. et al.
System: The UNT Digital Library
Low-defect reflective mask blanks for extreme ultraviolet lithography (open access)

Low-defect reflective mask blanks for extreme ultraviolet lithography

Extreme Ultraviolet Lithgraphy (EUVL) is an emerging technology for fabrication of sub-100 nm feature sizes on silicon, following the SIA roadmap well into the 21st century. The specific EUVL system described is a scanned, projection lithography system with a 4:1 reduction, using a laser plasma EUV source. The mask and all of the system optics are reflective, multilayer mirrors which function in the extreme ultraviolet at 13.4 nm wavelength. Since the masks are imaged to the wafer exposure plane, mask defects greater than 80% of the exposure plane CD (for 4:1 reduction) will in many cases render the mask useless, whereas intervening optics can have defects which are not a printing problem. For the 100 nm node, we must reduce defects to less than 0.01/cm&sup2; @ 80nm or larger to obtain acceptable mask production yields. We have succeeded in reducing the defects to less than 0.1/cm&sup2; for defects larger than 130 nm detected by visible light inspection tools, however our program goal is to achieve 0.01/cm&sup2; in the near future. More importantly though, we plan to have a detailed understanding of defect origination and the effect on multilayer growth in order to mitigate defects below the 10<sup>-2</sup>/cm&sup2; level on the …
Date: March 11, 1999
Creator: Burkhart, S. C.; Cerjarn, C.; Kearney, P.; Mirkarimi, P.; Walton, C. & Ray-Chaudhuri, A.
System: The UNT Digital Library
Large Friction Anisotropy of a Polydiacetylene Monolayer (open access)

Large Friction Anisotropy of a Polydiacetylene Monolayer

Friction force microscopy measurements of a polydiacetylene monolayer film reveal a 300% friction anisotropy that is correlated with the film structure. The film consists of a monolayer of the red form of N-(2-ethanol)- 10,12 pentacosadiynamide, prepared on a Langmuir trough and deposited on a mica substrate. As confirmed by atomic force microscopy and fluorescence microscopy, the monolayer consists of domains of linearly oriented conjugated backbones with pendant hydrocarbon side chains above and below the backbones. Maximum friction occurs when the sliding direction is perpendicular to the backbone. We propose that the backbones impose anisotropic packing of the hydrocarbon side chains which leads to the observed friction anisotropy. Friction anisotropy is therefore a sensitive, optically-independent indicator of polymer backbone direction and monolayer structural properties.
Date: May 11, 1999
Creator: Burns, A. R.; Carpick, R. W. & Sasaki, D. Y.
System: The UNT Digital Library
Development of small, fast reactor core designs using lead-based coolant. (open access)

Development of small, fast reactor core designs using lead-based coolant.

A variety of small (100 MWe) fast reactor core designs are developed, these include compact configurations, long-lived (15-year fuel lifetime) cores, and derated, natural circulation designs. Trade studies are described which identify key core design issues for lead-based coolant systems. Performance parameters and reactivity feedback coefficients are compared for lead-bismuth eutectic (LBE) and sodium-cooled cores of consistent design. The results of these studies indicate that the superior neutron reflection capability of lead alloys reduces the enrichment and burnup swing compared to conventional sodium-cooled systems; however, the discharge fluence is significantly increased. The size requirement for long-lived systems is constrained by reactivity loss considerations, not fuel burnup or fluence limits. The derated lead-alloy cooled natural circulation cores require a core volume roughly eight times greater than conventional compact systems. In general, reactivity coefficients important for passive safety performance are less favorable for the larger, derated configurations.
Date: June 11, 1999
Creator: Cahalan, J. E.; Hill, R. N.; Khalil, H. S. & Wade, D. C.
System: The UNT Digital Library
Dynamical Behavior of Multi-Robot Systems Using Lattice Gas Automata (open access)

Dynamical Behavior of Multi-Robot Systems Using Lattice Gas Automata

Recent attention has been given to the deployment of an adaptable sensor array realized by multi-robotic systems. Our group has been studying the collective behavior of autonomous, multi-agent systems and their applications in the area of remote-sensing and emerging threats. To accomplish such tasks, an interdisciplinary research effort at Sandia National Laboratories are conducting tests in the fields of sensor technology, robotics, and multi-robotic and multi-agents architectures. Our goal is to coordinate a constellation of point sensors that optimizes spatial coverage and multivariate signal analysis using unmanned robotic vehicles (e.g., RATLERs, Robotic All-ten-sin Lunar Exploration Rover-class vehicles). Overall design methodology is to evolve complex collective behaviors realized through simple interaction (kinetic) physics and artificial intelligence to enable real-time operational responses to emerging threats. This paper focuses on our recent work understanding the dynamics of many-body systems using the physics-based hydrodynamic model of lattice gas automata. Three design features are investigated. One, for single-speed robots, a hexagonal nearest-neighbor interaction topology is necessary to preserve standard hydrodynamic flow. Two, adaptability, defined by the swarm's deformation rate, can be controlled through the hydrodynamic viscosity term, which, in turn, is defined by the local robotic interaction rules. Three, due to the inherent non-linearity of …
Date: March 11, 1999
Creator: Cameron, S. M.; Robinett, R.; Stantz, K. M.; Trahan, M. W. & Wagner, J. S.
System: The UNT Digital Library
Deflection of large near-earth objects (open access)

Deflection of large near-earth objects

The Earth is periodically hit by near Earth objects (NEOs) ranging in size from dust to mountains. The small ones are a useful source of information, but those larger than about 1 km can cause global damage. The requirements for the deflection of NEOs with significant material strength are known reasonably well; however, the strength of large NEOs is not known, so those requirements may not apply. Meteor impacts on the Earth`s atmosphere give some information on strength as a function of object size and composition. This information is used here to show that large, weak objects could also be deflected efficiently, if addressed properly.
Date: January 11, 1999
Creator: Canavan, G. H.
System: The UNT Digital Library
Polymerization of the E and Z Isomers of Bis-(Triethoxysilyl)-2-Butene (open access)

Polymerization of the E and Z Isomers of Bis-(Triethoxysilyl)-2-Butene

We have synthesized the Z and E isomers of 1,4-bis(triethoxysilyl)-2- butene and polymerized them under acid and base catalyzed sol-gel conditions. As expected the E system formed crosslinked, insoluble gels. The Z isomer, by nature of its geometry, formed high molecular weight, soluble polymeric products under acidic conditions. We were able to prepare and isolate both the cyclic disilsesquioxane monomer, and its dimer. Comparison of their spectral characterization with that of the soluble polymers suggests that the cyclics are present within the polymers. lle synthesis of a dimer likely present at some early stage of the polymerization suggests that we may be able to control the reaction and form rigid polymers with controllable tacticity. In addition, most of the gels were found to be non-porous indicating that the gels were, in fact, more compliant than ethenylene-bridged polysilsesquioxanes leading to collapse of pores during drying.
Date: May 11, 1999
Creator: Carpenter, J.P. Dorhout, K.; Loy, D.A.; Shaltout, R.M. & Shea, K.J.
System: The UNT Digital Library
Apparent Charge Transfer at Semiconductor Surfaces (open access)

Apparent Charge Transfer at Semiconductor Surfaces

We investigate the apparent charge transfer between adatoms in the GeXPb[l.XjGe(lll) interface both experimentally and theoretically. Scanning tunneling microscopy and surface core level measurements suggest significant charge transfer from the Ge adatoms to the Pb adatoms. However, first-principles calculations unambiguously find that the total electronic displacement is negligibly small, and that the results of published experiments can be explained as a result of bond rearrangement.
Date: May 11, 1999
Creator: Carpinelli, Joseph M.; Stumpf, Roland R. & Weitering, Hanno H.
System: The UNT Digital Library