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Adapting high-resolution speckle imaging to moving targets and platforms (open access)

Adapting high-resolution speckle imaging to moving targets and platforms

High-resolution surveillance imaging with apertures greater than a few inches over horizontal or slant paths at optical or infrared wavelengths will typically be limited by atmospheric aberrations. With static targets and static platforms, we have previously demonstrated near-diffraction limited imaging of various targets including personnel and vehicles over horizontal and slant paths ranging from less than a kilometer to many tens of kilometers using adaptations to bispectral speckle imaging techniques. Nominally, these image processing methods require the target to be static with respect to its background during the data acquisition since multiple frames are required. To obtain a sufficient number of frames and also to allow the atmosphere to decorrelate between frames, data acquisition times on the order of one second are needed. Modifications to the original imaging algorithm will be needed to deal with situations where there is relative target to background motion. In this paper, we present an extension of these imaging techniques to accommodate mobile platforms and moving targets.
Date: February 5, 2004
Creator: Carrano, C J & Brase, J M
System: The UNT Digital Library
Statistical Stability and Time-Reversal Imgaing in Random Media (open access)

Statistical Stability and Time-Reversal Imgaing in Random Media

Localization of targets imbedded in a heterogeneous background medium is a common problem in seismic, ultrasonic, and electromagnetic imaging problems. The best imaging techniques make direct use of the eigenfunctions and eigenvalues of the array response matrix, as recent work on time-reversal acoustics has shown. Of the various imaging functionals studied, one that is representative of a preferred class is a time-domain generalization of MUSIC (MUltiple Signal Classification), which is a well-known linear subspace method normally applied only in the frequency domain. Since statistical stability is not characteristic of the frequency domain, a transform back to the time domain after first diagonalizing the array data in the frequency domain takes optimum advantage of both the time-domain stability and the frequency-domain orthogonality of the relevant eigenfunctions.
Date: February 5, 2002
Creator: Berryman, J; Borcea, L; Papanicolaou, G & Tsogka, C
System: The UNT Digital Library
Effect of Small Variation in the Composition of Plates and Weld Filler Wires on the General Corrosion Rate of Ni-Cr-Mo Alloys (open access)

Effect of Small Variation in the Composition of Plates and Weld Filler Wires on the General Corrosion Rate of Ni-Cr-Mo Alloys

The ASTM standard B 575 provides the requirements for the chemical composition of Nickel-Chromium-Molybdenum (Ni-Cr-Mo) alloys such as Alloy 22 (N06022) and Alloy 686 (N06686). The compositions of each element are given in a range. For example, the content of Mo is specified from 12.5 to 14.5 weight percent for Alloy 22 and from 15.0 to 17.0 weight percent for Alloy 686. It was important to determine how the corrosion rate of welded plates of Alloy 22 using Alloy 686 weld filler metal would change if heats of these alloys were prepared using several variations in the composition of the elements even though still in the range specified in B 575. All the material used in this report were especially prepared at Allegheny Ludlum Co. Seven heats of plate were welded with seven heats of wire. Immersion corrosion tests were conducted in a boiling solution of sulfuric acid plus ferric sulfate (ASTM G 28 A) using both as-welded (ASW) coupons and solution heat-treated (SHT) coupons. Results show that the corrosion rate was not affected by the chemistry of the materials within the range of the standards.
Date: February 5, 2005
Creator: Fix, David V.; Estill, John C. & Rebak, Raúl B.
System: The UNT Digital Library
Immobilization of uranium and plutonium into borobasalt, pyroxene and andradite mineral-like compositions (open access)

Immobilization of uranium and plutonium into borobasalt, pyroxene and andradite mineral-like compositions

The immobilization of plutonium-containing wastes into stable solid compositions is one of the problems to be solved in the disposal of radioactive wastes. Research efforts on the selection, preparation with the use of the cold crucible induction melter (CCIM) technology, and investigation of materials that are most suitable for immobilizing plutonium-containing wastes of different origin have been carried out at the All-Russian Scientific Research Institute of Inorganic Materials (VNIINM) and the Institute of the Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry (IGEM), Russian Academy of Sciences within the framework of agreements with Lawrence Livermore National Laboratory (LLNL, USA) regarding material and technical support. This paper presents the data on the synthesis of cerium-, uranium-, and plutonium-containing materials based on borobasalt, pyroxene, and andradite compositions in the muffle furnace and by the CCIM method. Compositions containing up to 15-18 wt% cerium oxide, 8-11 wt% uranium oxide, and 4.6-5.7 wt% plutonium oxide were obtained in laboratory facilities installed in glove boxes. Comparison studies of the materials synthesized in the muffle furnace and CCIM demonstrate the advantages of using the CCIM method. The distribution of components in the materials.
Date: February 5, 2001
Creator: Matyunin, Y I; Jardine, L J & Yudintsev, S V
System: The UNT Digital Library
Stopping and Baryon Transport in Heavy Ion Reactions. (open access)

Stopping and Baryon Transport in Heavy Ion Reactions.

In this report I will give an experimental overview on nuclear stopping in hadron collisions, and relate observations to understanding of baryon transport. Baryon number transport is not only evidenced via net-proton distributions but also by the enhancement of strange baryons near mid-rapidity. Although the focus is on high-energy data obtained from pp and heavy ions from RHIC, relevant data from SPS and ISR will be considered. A discussion how the available data at higher energy relates and gives information on baryon junction, quark-diquark breaking will be made.
Date: February 5, 2005
Creator: Videbaek, F.
System: The UNT Digital Library
Applying New Methods to Research Reactor Analysis. (open access)

Applying New Methods to Research Reactor Analysis.

Detailed reactor physics and safety analyses are being performed for the 20 MW D{sub 2}O-moderated research reactor at the National Institute of Standards and Technology (NIST). The analyses employ state-of-the-art calculational methods and will contribute to an update to the Final Safety Analysis Report (FSAR). Three-dimensional MCNP Monte Carlo neutron and photon transport calculations are performed to determine power and reactivity parameters, including feedback coefficients and control element worths. The core depletion and determination of the fuel compositions are performed with MONTEBURNS to model the reactor at the beginning, middle, and end-of-cycle. The time-dependent analysis of the primary loop is determined with a RELAP5 transient analysis model that includes the pump, heat exchanger, fuel element geometry, and flow channels. A statistical analysis used to assure protection from critical heat flux (CHF) is performed using a Monte Carlo simulation of the uncertainties contributing to the CHF calculation. The power distributions used to determine the local fuel conditions and margin to CHF are determined with MCNP. Evaluations have been performed for the following accidents: (1) the control rod withdrawal startup accident, (2) the maximum reactivity insertion accident, (3) loss-of-flow resulting from loss of electrical power, (4) loss-of-flow resulting from a primary pump …
Date: February 5, 2004
Creator: Diamond, David J.; Cheng, L.; Hanson, A.; Xu, J. & Carew, J. F.
System: The UNT Digital Library
BRAHMS OVERVIEW (open access)

BRAHMS OVERVIEW

A brief review of BRAHMS measurements of bulk particle production in RHIC Au+Au collisions at {radical}s{sub NN} 200GeV is presented, together with some discussion of baryon number transport. Intermediate p{sub T} measurements in different collision systems (Au+Au, d+ Au and p+p) are also discussed in the context of jet quenching and saturation of the gluon density in Au ions at RHIC energies. This report also includes preliminary results for identified particles at forward rapidities in d+Au and Au+Au collisions.
Date: February 5, 2005
Creator: DEBBE, R. & COLLABORATION, FOR THE BRAHMS
System: The UNT Digital Library
Electric Current Enhanced Point Defect Mobility in Ni3Ti Intermetallic (open access)

Electric Current Enhanced Point Defect Mobility in Ni3Ti Intermetallic

The effect of the application of a DC current on the annealing of point defects in Ni{sub 3}Ti was investigated by positron annihilation spectroscopy (PAS). An increased rate of point defect annealing is observed under the influence of a current and is attributed to a 24% decrease in the mobility activation energy. The results are interpreted in terms of the electron wind effect and the complex nature of diffusion in ordered intermetallic phases. This work represents the first direct evidence of the role of the current on the mobility of point defects in intermetallic systems.
Date: February 5, 2004
Creator: Anselmi-Tamburini, U; Asoka-Kumar, P; Garay, J E; Munir, Z A & Glade, S C
System: The UNT Digital Library
Solution of the nonlinear multifrequency radiation diffusion equations using pseudo transient continuation (open access)

Solution of the nonlinear multifrequency radiation diffusion equations using pseudo transient continuation

Computer codes simulating high energy density physics consist of modules for distinct physical processes, e.g., compressible hydrodynamics and radiation transport. For the latter, one model assumes tight coupling between radiation and matter. The dependent variables are the spectral radiation energy density u(x,v,t) and the matter temperature T(x,t), where x, v, and T denote position, frequency, and time, respectively.
Date: February 5, 2004
Creator: Shestakov, A
System: The UNT Digital Library
Stifling of Crevice Corrosion in Alloy 22 During Constant Potential Tests (open access)

Stifling of Crevice Corrosion in Alloy 22 During Constant Potential Tests

Artificially creviced Alloy 22 (N06022) is susceptible to crevice corrosion in presence of high chloride aqueous solution when high temperatures and high anodic potentials are applied. The presence of oxyanions in the electrolyte, especially nitrate, inhibits the nucleation and growth of crevice corrosion. Crevice corrosion may initiate when a constant potential above the crevice repassivation potential is applied. The occurrence of crevice corrosion can be divided into three characteristic domains: (1) nucleation, (2) growth and (3) stifling and arrest. That is, crevice corrosion reaches a critical stage after which growth stops and the specimens start to regain the passive behavior displayed prior to localized attack.
Date: February 5, 2005
Creator: Mon, K G; Pasupathi, P; Yilmaz, A & Rebak, R B
System: The UNT Digital Library
Characterization and Operation of Liquid Crystal Adaptive Optics Phoropter (open access)

Characterization and Operation of Liquid Crystal Adaptive Optics Phoropter

Adaptive optics (AO), a mature technology developed for astronomy to compensate for the effects of atmospheric turbulence, can also be used to correct the aberrations of the eye. The classic phoropter is used by ophthalmologists and optometrists to estimate and correct the lower-order aberrations of the eye, defocus and astigmatism, in order to derive a vision correction prescription for their patients. An adaptive optics phoropter measures and corrects the aberrations in the human eye using adaptive optics techniques, which are capable of dealing with both the standard low-order aberrations and higher-order aberrations, including coma and spherical aberration. High-order aberrations have been shown to degrade visual performance for clinical subjects in initial investigations. An adaptive optics phoropter has been designed and constructed based on a Shack-Hartmann sensor to measure the aberrations of the eye, and a liquid crystal spatial light modulator to compensate for them. This system should produce near diffraction-limited optical image quality at the retina, which will enable investigation of the psychophysical limits of human vision. This paper describes the characterization and operation of the AO phoropter with results from human subject testing.
Date: February 5, 2003
Creator: Awwal, A.; Bauman, B.; Gavel, D.; Olivier, S.; Jones, S.; Hardy, J. L. et al.
System: The UNT Digital Library
Anodic Behavior of Specimens Prepared from a Full-Diameter Alloy 22 Fabricated Container (open access)

Anodic Behavior of Specimens Prepared from a Full-Diameter Alloy 22 Fabricated Container

Alloy 22 (N06022) has been extensively tested for general and localized corrosion behavior both in the wrought and annealed condition and in the as-welded condition. The specimens for testing were mostly prepared from flat plates of material. It was important to determine if the process of fabricating a full diameter Alloy 22 container will affect the corrosion performance of the alloy. Specimens were prepared directly from a fabricated container and tested for corrosion resistance. Results show that both the anodic corrosion behavior and the localized corrosion resistance of specimens prepared from a welded fabricated container was the same as from flat welded plates.
Date: February 5, 2005
Creator: King, K. J.; Estill, J. C. & Rebak, R. B.
System: The UNT Digital Library
Ductile, Brittle Failure Characteristics as Determined by the State of the Material and the Imposed State of Stress (open access)

Ductile, Brittle Failure Characteristics as Determined by the State of the Material and the Imposed State of Stress

A method is developed for determining whether a particular mode of failure is expected to be of ductile type or brittle type depending upon both the state of the material and the particular state of stressing the isotropic material to failure. The state of the material is determined by two specific failure properties and a newly formulated failure theory. The ductile versus brittle criterion then involves the state of the material specification and the mean normal stress part of the imposed stress state. Several examples are given for different stress states and a spectrum of materials types. Closely related to the failure mode types are the orientations of the associated failure surfaces. The resulting failure surface angle predictions are compared with those from the Coulomb-Mohr failure criterion. In uniaxial tension, only the present method correctly predicts the octahedral failure angle at the ductile limit, and also shows a distinct failure mode transition from ductile type to brittle type as the state of the material changes. The explicit D-B criterion and the related failure surface orientation methodology are intended to provide a refinement and generalization of the ductile-brittle transition viewed only as a state property to also include a dependence upon …
Date: February 5, 2004
Creator: Christensen, R M
System: The UNT Digital Library
Inverse problem in explosion and combustion (open access)

Inverse problem in explosion and combustion

The principal task of our studies is to provide a rational interpretation of the thermodynamic and fluid dynamic events taking place in a closed vessel upon detonation of an explosive charge and subsequent turbulent combustion of its products, acting as fuel for an exothermic reaction with air. Under such circumstances, the latter has been compressed by a reverberating shock front of the blast wave generated by the explosion. The paper presents the chemical and thermodynamic background and its numerical results, deduced for this purpose from mass spectroscopic data and pressure records, acquired upon explosion of a 0.8 kg charge of TNT in a 17 m{sup 3} chamber filled with air--a diagnostic analysis identified by the title. The evolution of the flow field and its structure are presented in a companion paper.
Date: February 5, 2001
Creator: Oppenheim, A K; Sum, T-H & Kuhl, A L
System: The UNT Digital Library
Disentangling Orbital and Valley Hall Effects in Bilayers of Transition Metal Dichalcogenides (open access)

Disentangling Orbital and Valley Hall Effects in Bilayers of Transition Metal Dichalcogenides

This article shows that a bilayer of 2H-MoS₂ is an orbital Hall insulator that exhibits a sizeable orbital Hall effect in the absence of both spin and valley Hall effects. The results are based on density functional theory and low-energy effective model calculations and strongly suggest that bilayers of TMDs are highly suitable platforms for direct observation of the orbital Hall insulating phase in two-dimensional materials.
Date: February 5, 2021
Creator: Cysne, Tarik P.; Costa, Marcio; Canonico, Luis M.; Buongiorno Nardelli, Marco; Muniz, R. B. & Rappoport, Tatiana G.
System: The UNT Digital Library
The mitochondrial localized CISD-3.1/CISD-3.2 proteins are required to maintain normal germline structure and function in Caenorhabditis elegans (open access)

The mitochondrial localized CISD-3.1/CISD-3.2 proteins are required to maintain normal germline structure and function in Caenorhabditis elegans

Article isolating the cisd-3.2(pnIs68) mutant that resulted in physiological and fitness defects including germline abnormalities that are associated with abnormal stem cell niche and disrupted formation of bivalent chromosomes. Results further support the idea that the CISD protein family is required for mitochondrial function that supports important functions in animals including overall fitness and germline viability.
Date: February 5, 2021
Creator: King, Skylar D.; Gray, Chipo F.; Song, Luhua; Mittler, Ron & Padilla, Pamela A.
System: The UNT Digital Library